JP2010205434A - Organic electroluminescent element - Google Patents

Abstract

A main object of the present invention is to provide an organic EL element that can achieve high efficiency and long life and has little color change.
The present invention is an organic EL device in which an anode, a hole injecting and transporting layer, an anode side light emitting layer, a central light emitting layer, an electron injecting and transporting layer, and a cathode are laminated in order. And the host material of the anode side light emitting layer are the same, the constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different, and the electron affinity of the material of the hole injection transport layer is expressed as Ea ₁ , where Ea ₂ is the electron affinity of the constituent material of the central light emitting layer, Ea ₁ ≧ Ea ₂ , the ionization potential of the constituent material of the central light emitting layer is Ip ₂ , and the constituent material of the electron injecting and transporting layer is Provided is an organic EL device characterized in that Ip ₂ ≧ Ip ₃ when the ionization potential is Ip ₃ .
[Selection] Figure 2

Description

  The present invention relates to an organic electroluminescence device having a plurality of light emitting layers.

  Organic electroluminescence (hereinafter, electroluminescence may be abbreviated as EL) elements are attracting attention for use as self-luminous displays, and high brightness, high efficiency, and long life are required.

As a technique for increasing the brightness of an organic EL element, it is known to use a light emitting layer containing a host material and a light emitting dopant. In this light emitting layer, holes and electrons injected from the anode and the cathode recombine with the host material in the light emitting layer, and the light emitting dopant receives the energy to emit light. In such a light emitting layer, light emission with high luminance and good color purity can be obtained.
In addition, in an organic EL device having a light emitting layer containing a host material and a light emitting dopant, only the host material is formed at the interface between the light emitting layer and the hole transport layer or the electron transport layer for the purpose of lowering the driving voltage. Providing a region has been proposed (see, for example, Patent Document 1).

  On the other hand, as a technology for improving the efficiency and extending the life of organic EL elements, in addition to a light emitting material, a multilayer in which a plurality of layers are stacked using a material having a hole or electron injection function, a transport function, and a blocking function It is known to have a structure. However, in an organic EL element having a multilayer structure, there is a concern that deterioration occurs at the interface of each layer during driving, resulting in a decrease in light emission efficiency or a decrease in luminance due to deterioration of the element. In particular, in an organic EL element provided with a blocking layer, charges are likely to accumulate at the interface between the light-emitting layer and the blocking layer, and therefore deterioration is likely to occur at the interface.

  Therefore, the present inventors have prescribed the magnitude relationship between the ionization potential and electron affinity of each layer as a method for suppressing the deterioration at the interface of each layer during driving, and developed an organic EL device having no blocking layer. It has been proposed (see Patent Document 2).

  In recent years, organic EL elements emitting white light have been actively developed because they can be applied to light sources. White light can usually be obtained by light emission of two or three kinds of light emitting materials. However, when the light emitting layer includes a plurality of types of light emitting materials, there is a problem that energy transfer occurs between the light emitting materials and chromaticity changes. Accordingly, it has been proposed to stack a plurality of light emitting layers containing different light emitting materials (see, for example, Patent Documents 3 to 7).

JP 2007-134777 A International Publication No. 2008/102644 Pamphlet JP 2000-68057 A JP 2003-282266 A International Publication No. 2005/91684 Pamphlet JP 2006-269232 A JP 2006-127969 A

  When a plurality of light emitting layers are stacked, the number of interfaces between the layers increases, and there is a concern about the deterioration at the interfaces between the layers as described above. In particular, deterioration at the interface of each layer tends to cause a color change when a plurality of light emitting layers are laminated. Therefore, there is room for further improvement in order to reduce the color change when a plurality of light emitting layers are stacked.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide an organic EL element capable of realizing high efficiency and long life and having little color change.

In order to achieve the above object, the present invention provides an anode, a hole injection transport layer formed on the anode, and an anode side formed on the hole injection transport layer and containing a host material and a light emitting dopant. An organic EL having a light emitting layer, a central light emitting layer formed on the anode side light emitting layer, an electron injecting and transporting layer formed on the central light emitting layer, and a cathode formed on the electron injecting and transporting layer The element, wherein the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, the constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different, and the hole When the electron affinity of the constituent material of the injection transport layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and the ionization potential of the constituent material of the central light emitting layer is Ip _2, structure of the electron injection transport layer When the ionization potential of the material was Ip _3, to provide an organic EL element which is a Ip ₂ ≧ Ip _3.

According to the present invention, the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, and the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ Therefore, there is no charge accumulation at the interface between the hole injection transport layer and the anode side light emitting layer during driving, and deterioration can be suppressed. In addition, since the ionization potential of the constituent materials of the central light emitting layer and the electron injecting and transporting layer is Ip ₂ ≧ Ip ₃ , there is no charge accumulation at the interface between the central light emitting layer and the electron injecting and transporting layer during driving, suppressing deterioration can do. Furthermore, since the constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different, the interface between the central light emitting layer and the anode side light emitting layer is the interface between the hole injection transport layer and the anode side light emitting layer, the central light emitting layer and the electrons. Charges are more easily accumulated than at the interface of the injection transport layer, and light can be emitted intensively at the interface between the central light emitting layer and the anode side light emitting layer. Therefore, it is possible to obtain an organic EL element with high efficiency and long life and little color change.

The present invention also provides an anode, a hole injection transport layer formed on the anode, a central light emitting layer formed on the hole injection transport layer, and a host material formed on the central light emitting layer. And a cathode-side light-emitting layer containing a light-emitting dopant, an electron injection / transport layer formed on the cathode-side light-emitting layer, and a cathode formed on the electron injection / transport layer, The constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, and the constituent material of the hole injection transport layer is When the electron affinity is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and the ionization potential of the constituent material of the central light emitting layer is Ip ₂ . Ionization potion of the constituent materials of When the interstitial was Ip _3, to provide an organic EL element which is a Ip ₂ ≧ Ip _3.

According to the present invention, since the electron affinity of the constituent materials of the hole injecting and transporting layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ , charge accumulation at the interface between the hole injecting and transporting layer and the central light emitting layer during driving No deterioration can be suppressed. In addition, since the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, and the ionization potential of the constituent material of the central light emitting layer and the electron injection transport layer is Ip ₂ ≧ Ip ₃ , There is no charge accumulation at the interface between the side light emitting layer and the electron injecting and transporting layer, and deterioration can be suppressed. Further, since the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, the interface between the central light emitting layer and the cathode side light emitting layer is the interface between the hole injection transport layer and the central light emitting layer, the cathode side light emitting layer and Charges are more easily accumulated than at the interface of the injection transport layer, and light can be emitted intensively at the interface between the central light emitting layer and the cathode side light emitting layer. Therefore, it is possible to obtain an organic EL element with high efficiency and long life and little color change.

Furthermore, the present invention provides an anode, a hole injection transport layer formed on the anode, an anode side light emitting layer formed on the hole injection transport layer and containing a host material and a light emitting dopant, and the anode A central light emitting layer formed on the side light emitting layer, a cathode side light emitting layer formed on the central light emitting layer and containing a host material and a light emitting dopant, and an electron injection transport layer formed on the cathode side light emitting layer And a cathode formed on the electron injecting and transporting layer, wherein the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer are the same, and the electron injecting and transporting The constituent material of the layer and the host material of the cathode side light emitting layer are the same, the constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different, and the constituent material of the central light emitting layer and the cathode side light emitting layer of Different strike material, Ea ₁ electron affinity of the constituent material of the hole injecting and transporting layer, when an electron affinity of the constituent material of the central light-emitting layer was changed to Ea _2, a Ea ₁ ≧ Ea _2, the central light-emitting layer Ip ₂ and an ionization potential of a constituent material, when the ionization potential of the constituent material of the electron injection transport layer was Ip _3, to provide an organic EL element which is a Ip ₂ ≧ Ip _3.

According to the present invention, the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, and the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ Therefore, there is no charge accumulation at the interface between the hole injection transport layer and the anode side light emitting layer during driving, and deterioration can be suppressed. In addition, since the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, and the ionization potential of the constituent material of the central light emitting layer and the electron injection transport layer is Ip ₂ ≧ Ip ₃ , There is no charge accumulation at the interface between the side light emitting layer and the electron injecting and transporting layer, and deterioration can be suppressed. Furthermore, the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, and the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different. Compared with the interface of the hole injection transport layer and the anode side light emitting layer and the interface of the cathode side light emitting layer and the electron injection transport layer, the charge is easily accumulated in the interface between the layer and the cathode side light emitting layer. Light can be emitted intensively at the interface of the anode side light emitting layer and at the interface of the central light emitting layer and the cathode side light emitting layer. Therefore, it is possible to obtain an organic EL element with high efficiency and long life and little color change.

  In the above invention, the hole injecting and transporting layer and the electron injecting and transporting layer contain a bipolar material capable of transporting holes and electrons, and the bipolar contained in the hole injecting and transporting layer and the electron injecting and transporting layer. The materials are preferably the same. When the hole injection / transport layer and the electron injection / transport layer contain the same bipolar material, even if holes penetrate into the electron injection / transport layer or electrons penetrate into the hole injection / transport layer, each layer during driving This is because deterioration at the interface can be effectively suppressed.

  Moreover, in the said invention, the said center light emitting layer contains host material and a light emission dopant, the constituent material of the said electron injection transport layer and the host material of the said center light emitting layer are the same, The structure of the said hole injection transport layer It is also preferable that the materials and the constituent materials of the electron injecting and transporting layer are different. This is because when the constituent material of the electron injecting and transporting layer and the host material of the central light emitting layer are the same, the electron injection barrier from the electron injecting and transporting layer to the central light emitting layer is reduced, and the driving voltage can be lowered.

  Furthermore, in the said invention, the said center light emitting layer contains host material and a light emission dopant, the constituent material of the said positive hole injection transport layer and the host material of the said central light emission layer are the same, It is also preferable that the constituent material and the constituent material of the electron injecting and transporting layer are different. Since the constituent material of the hole injecting and transporting layer and the host material of the central light emitting layer are the same, the hole injection barrier from the hole injecting and transporting layer to the central light emitting layer is reduced, and the driving voltage can be lowered. It is.

  In the above invention, a second central light emitting layer containing a host material and a light emitting dopant may be formed between the anode side light emitting layer and the central light emitting layer. In this case, the second central light emitting layer may be formed. It is preferable that the host material of the layer is the same as the host material of the anode side light emitting layer.

  Furthermore, in the above invention, a third central light emitting layer containing a host material and a light emitting dopant may be formed between the cathode side light emitting layer and the central light emitting layer. The host material of the layer is preferably the same as the host material of the cathode side light emitting layer.

  In the present invention, the central light emitting layer contains a host material and a light emitting dopant, and has one or more doped regions containing the light emitting dopant and one or more non-doped regions not containing the light emitting dopant. It is preferable. This is because, when the central light emitting layer has a non-doped region, energy transfer from the light emitting dopant in the doped region of the central light emitting layer to other substances can be suppressed, and the light emission efficiency can be increased.

  Furthermore, in the present invention, the anode side light emitting layer preferably has one or more doped regions containing the light emitting dopant and one or more non-doped regions not containing the light emitting dopant. This is because when the anode side light emitting layer has a non-doped region, energy transfer from the light emitting dopant in the doped region of the anode side light emitting layer to other substances can be suppressed, and the light emission efficiency can be increased.

  In the present invention, it is preferable that the cathode side light emitting layer has one or more doped regions containing the light emitting dopant and one or more non-doped regions not containing the light emitting dopant. This is because when the cathode side light emitting layer has a non-doped region, energy transfer from the light emitting dopant in the doped region of the cathode side light emitting layer to other substances can be suppressed, and the light emission efficiency can be increased.

In the above invention, the central light emitting layer may have the non-doped region on the hole injecting and transporting layer side. When the hole injecting and transporting layer, the anode side light emitting layer, and the central light emitting layer are sequentially laminated, the energy transfer between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the central light emitting layer is suppressed. be able to. On the other hand, when the hole injecting and transporting layer and the central light emitting layer are sequentially laminated, energy transfer from the light emitting dopant in the central light emitting layer to the constituent material of the hole injecting and transporting layer can be suppressed. In addition, since the non-doped region is provided at the interface between the central light emitting layer and the hole injecting and transporting layer, hole injection from the hole injecting and transporting layer to the central light emitting layer can be improved. Furthermore, although the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ , a non-doped region is provided at the interface between the central light emitting layer and the hole injection transport layer, The charge trapped by the light emitting dopant in the light emitting layer can balance the charge injected into the central light emitting layer.

In the above invention, the central light emitting layer may have the non-doped region on the electron injection / transport layer side. In the case where the central light emitting layer, the cathode side light emitting layer, and the electron injecting and transporting layer are sequentially laminated, the energy transfer between the light emitting dopant in the central light emitting layer and the light emitting dopant in the cathode side light emitting layer is suppressed. Can do. On the other hand, when the central light emitting layer and the electron injecting and transporting layer are sequentially laminated, energy transfer from the light emitting dopant in the central light emitting layer to the constituent material of the electron injecting and transporting layer can be suppressed. Further, since the non-doped region is provided at the interface between the central light emitting layer and the electron injecting and transporting layer, electron injection from the electron injecting and transporting layer to the central light emitting layer can be improved. Furthermore, although the ionization potential of the constituent material of the electron injection transport layer and the central light emitting layer is Ip ₂ ≧ Ip ₃ , a non-doped region is provided at the interface between the central light emitting layer and the electron injection transport layer, so the central light emitting layer The charge injected into the central light emitting layer can be balanced by trapping the charge by the light emitting dopant therein.

  Furthermore, in the above invention, the central light emitting layer has two doped regions, the non-doped regions are disposed between the two doped regions, and the two doped regions are of different types. It may contain a luminescent dopant. This is because energy transfer from the light-emitting dopant contained in one doped region to the light-emitting dopant contained in the other doped region hardly occurs and the light emission efficiency can be improved.

  Moreover, in the said invention, the said anode side light emitting layer may have the said non-dope area | region in the said center light emitting layer side. This is because energy transfer between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the central light emitting layer can be suppressed.

  Furthermore, in the above invention, the anode side light emitting layer has the two doped regions, the non-doped region is disposed between the two doped regions, and the two doped regions are different types. The luminescent dopant may be contained. This is because energy transfer from the light-emitting dopant contained in one doped region to the light-emitting dopant contained in the other doped region hardly occurs and the light emission efficiency can be improved.

  Moreover, in the said invention, the said cathode side light emitting layer may have the said non-dope area | region in the said center light emitting layer side. This is because energy transfer between the light emitting dopant in the cathode side light emitting layer and the light emitting dopant in the central light emitting layer can be suppressed.

  Furthermore, in the above invention, the cathode side light emitting layer has two doped regions, the non-doped region is disposed between the two doped regions, and the two doped regions are different from each other. The luminescent dopant may be contained. This is because energy transfer from the light-emitting dopant contained in one doped region to the light-emitting dopant contained in the other doped region hardly occurs and the light emission efficiency can be improved.

In the present invention, a second hole injection transport layer may be formed between the anode and the hole injection transport layer. In this case, the electron affinity of the constituent material of the second hole injection transport layer If Ea ₆ is Ea ₆ <Ea ₁ , and if the ionization potential of the constituent material of the second hole injection transport layer is Ip ₆ , Ip ₆ ≦ Ip ₁ may be satisfied. Since Ea ₆ <Ea ₁ , the presence of an energy barrier prevents penetration of electrons from the hole injection transport layer to the anode side, and suppresses deterioration at the interface between the second hole injection transport layer and the anode. Because you can. Further, since Ip ₆ ≦ Ip ₁ , holes can be easily injected from the anode.

Furthermore, in the present invention, a second electron injection transport layer may be formed between the electron injection transport layer and the cathode. In this case, the ionization potential of the constituent material of the second electron injection transport layer is set to Ip ₇ In this case, Ip ₃ <Ip ₇ and Ea ₃ ≦ Ea ₇ where Ea ₇ is the electron affinity of the constituent material of the second electron injecting and transporting layer. Because it is Ip ₃ <Ip _7, prevents the penetration of the electron injecting and transporting layer of holes to the cathode side by an energy barrier exists, that the second electron injecting and transporting layer and to suppress the deterioration at the interface between the cathode Because it can. Further, since Ea ₃ ≦ Ea ₇ , electrons can be easily injected from the cathode.

  In the present invention, it is preferable that at least one of the plurality of light emitting layers contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant. This is because energy transfer is suppressed between the fluorescent light-emitting dopant and the phosphorescent light-emitting dopant, the light emission efficiency is increased, and a desired light emission color can be obtained.

  In the present invention, the electron affinity of the constituent materials of the hole injection transport layer and the central light emitting layer and the ionization potential of the constituent materials of the central light emitting layer and the electron injection transport layer satisfy a predetermined relationship, and the hole injection transport layer and The anode-side light-emitting layer contains the same host material, or the electron-injecting and transporting layer and the cathode-side light-emitting layer contain the same host material, thereby improving efficiency and extending the life and reducing the color change. There is an effect that can be.

It is a schematic sectional drawing which shows an example of the organic EL element of this invention. It is a schematic diagram which shows an example of the band diagram of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic diagram which shows the other example of the band diagram of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention. It is a schematic sectional drawing which shows the other example of the organic EL element of this invention.

Hereinafter, the organic EL device of the present invention will be described in detail.
The organic EL device of the present invention can be divided into three embodiments depending on the constitution of a plurality of light emitting layers. In the following, each embodiment will be described separately.

I. First Embodiment A first embodiment of the organic EL device of the present invention includes an anode, a hole injection transport layer formed on the anode, a host material and a light emitting dopant formed on the hole injection transport layer. Containing an anode-side light emitting layer, a central light-emitting layer formed on the anode-side light-emitting layer, an electron injection / transport layer formed on the central light-emitting layer, and a cathode formed on the electron injection / transport layer Wherein the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer are the same, and the constituent material of the central light emitting layer and the host material of the anode side light emitting layer are In contrast, when the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and the constituent material of the central light emitting layer the Ip _2, the electron ionization potential When the ionization potential of the constituent material of the incoming transport layer was Ip _3, it is characterized in that it is Ip ₂ ≧ Ip _3.

  The “constituent material” of each layer refers to the material when each layer is composed of a single material, and the host material when each layer is composed of a host material and a dopant. Say.

  In addition, the “ionization potential of a constituent material” of each layer means the ionization potential of the material when each layer is made of a single material, and each layer is made up of a host material and a dopant. In some cases, it refers to the ionization potential of the host material. Similarly, the “electron affinity of a constituent material” of each layer means the electron affinity of the material when each layer is made of a single material, and each layer is made up of a host material and a dopant. The electron affinity of the host material.

  The ionization potential is a value determined by UPS (ultraviolet photoelectron spectroscopy) (for example, measuring instrument name “AC-2” manufactured by Riken Keiki Co., Ltd.). As a method for measuring electron affinity, first, HOMO energy is obtained by UPS (ultraviolet photoelectron spectroscopy) (for example, “AC-2” manufactured by Riken Keiki Co., Ltd.), and then an energy gap measurement value by light absorption and the above HOMO energy. The method of calculating from is adopted.

The organic EL element of this embodiment will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of the organic EL element of this embodiment. As illustrated in FIG. 1, the organic EL element 1 includes an anode 3, a hole injection transport layer 4, an anode side light emitting layer 5 a, a central light emitting layer 6, an electron injection transport layer 7, and a cathode 8 on a substrate 2. They are sequentially stacked. The constituent material of the hole injection transport layer 4 and the host material of the anode side light emitting layer 5a are the same. Moreover, the host material of the anode side light emitting layer 5a and the constituent material of the central light emitting layer 6 are different.

FIG. 2 and FIG. 3 are schematic views each showing an example of a band diagram of the organic EL element of this embodiment. In the organic EL device illustrated in FIG. 1, the ionization potential of the hole injection transport layer 4 is Ip ₁ , the ionization potential of the host material of the anode side light emitting layer 5a is Ip ₄ , and the ionization potential of the constituent material of the central light emitting layer 6 is Ip. ₂ , the ionization potential of the constituent material of the electron injection transport layer 7 is Ip ₃ , the electron affinity of the constituent material of the hole injection transport layer 4 is Ea ₁ , the electron affinity of the host material of the anode side light emitting layer 5 a is Ea ₄ , The electron affinity of the constituent material of the light emitting layer 6 is Ea ₂ , and the electron affinity of the constituent material of the electron injection / transport layer 7 is Ea ₃ .

The relationship between the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ , and the relationship of the ionization potential of the constituent material of the central light emitting layer and the electron injection transport layer is Ip ₂ ≧ Ip ₃ .
Since the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer are the same, the relationship between the ionizing potential of the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer is Ip ₁ = Ip ₄ And the relationship between the electron affinity of the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer is Ea ₁ = Ea ₄ .
Construction material of the host material and the central light-emitting layer on the anode side light emitting layer from different, Ea ₄ ≠ Ea ₂ when Ip ₄ = Ip _2, and a Ip ₄ ≠ Ip ₂ when Ea ₄ = Ea _2.
That is, the relationship of the electron affinity of the constituent material for the hole injecting and transporting layer constituting material and the anode side light emitting layer host material and the central light-emitting layer of is _{Ea 1 = Ea 4 ≧ Ea 2} , Ip 1 = Ip 4 = When Ip ₂ , Ea ₁ ≠ Ea ₂ and Ea ₄ ≠ Ea ₂ , and when Ea ₁ = Ea ₄ = Ea ₂ , Ip ₁ ≠ Ip ₂ and Ip ₄ ≠ Ip ₂ .

In this embodiment, the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, and the relationship between the electron affinity of the constituent material of the hole injection transport layer and the constituent material of the central light emitting layer is Ea ₁ Since ≧ Ea ₂ and the relationship between the ionization potentials of the constituent material of the central light emitting layer and the constituent material of the electron injecting and transporting layer is Ip ₂ ≧ Ip ₃ , the penetration of holes and electrons into the counter electrode occurs, but the anode Since holes and electrons are smoothly transported between the cathode and the cathode, there is no charge accumulation at the interface between the hole injection transport layer and the anode side light emitting layer and the interface between the central light emitting layer and the electron injection transport layer during driving, Deterioration at the interface between these layers can be suppressed. Accordingly, it is possible to obtain a remarkably stable lifetime characteristic and to reduce the color change.

  Further, in this embodiment, the host material of the anode side light emitting layer and the constituent material of the center light emitting layer are different, so that the hole injection transport layer and the anode side light emitting layer are disposed at the interface between the center light emitting layer and the anode side light emitting layer. Charges are more likely to be accumulated than at the interface and the interface between the central light emitting layer and the electron injecting and transporting layer, and light can be emitted intensively at the interface between the central light emitting layer and the anode side light emitting layer. Moreover, since holes and electrons are transported smoothly as described above, holes and electrons are recombined throughout the light emitting layer, so that the recombination efficiency of holes and electrons is not significantly reduced. Therefore, high efficiency can be achieved.

  Furthermore, in this embodiment, since the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, there is no hole injection barrier from the hole injection transport layer to the anode side light emitting layer. It is possible to reduce the voltage.

  Hereinafter, each structure in the organic EL element of this embodiment is demonstrated.

1. In this embodiment, when the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ When the ionization potential of the constituent material of the central light emitting layer is Ip ₂ and the ionization potential of the constituent material of the electron injection transport layer is Ip ₃ , Ip ₂ ≧ Ip ₃ .

Regarding the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer, the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ , and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ Ea ₁ ≧ Ea ₂ is sufficient. In this embodiment, since the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, the host material of the anode side light emitting layer and the constituent material of the central light emitting layer are different. The electron affinity of the constituent material of the anode, the host material of the anode side light emitting layer, and the constituent material of the central light emitting layer is the electron affinity of the constituent material of the hole injecting and transporting layer Ea ₁ , the electron of the host material of the anode side light emitting layer When the affinity is Ea ₄ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ = Ea ₄ ≧ Ea ₂ . In this case, since the constituent materials of the host-side light emitting layer and the central light-emitting layer are different, when Ip ₁ = Ip ₄ = Ip ₂ , Ea ₁ ≠ Ea ₂ and Ea ₄ ≠ Ea ₂ , and Ea ₁ = Ea ₄ When I = Ea ₂ , Ip ₁ ≠ Ip ₂ and Ip ₄ ≠ Ip ₂ .
Among these, it is preferable that Ea ₁ = Ea ₄ > Ea ₂ . This is because, if Ea ₁ = Ea ₄ > Ea ₂ and Ip ₁ = Ip ₄ <Ip ₂ , the band gap energy of the constituent material of the central light emitting layer can be made relatively large. For example, when the central light-emitting layer contains a host material and a light-emitting dopant, the host material and the light-emitting dopant have an ionization potential and an electron affinity that satisfy a predetermined relationship in order to improve luminous efficiency. It becomes easy to select the material and the luminescent dopant.

In the case of Ea ₁ = Ea ₄ > Ea ₂ , the difference between Ea ₁ and Ea ₄ and Ea ₂ is that Although it differs depending on the situation, specifically, it is preferably 0.1 eV or more, and more preferably 0.2 eV or more.

Regarding the relationship between the ionization potentials of the constituent materials of the hole injection transport layer and the central light emitting layer, the ionization potential of the constituent materials of the hole injection transport layer is Ip ₁ and the ionization potential of the constituent materials of the central light emitting layer is Ip _2. Usually, Ip ₁ ≦ Ip ₂ . In the present embodiment, as described above, the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, and the host material of the anode side light emitting layer and the constituent material of the central light emitting layer are different. relation of the ionization potentials of the constituent material for the hole injecting and transporting layer constituting material and the anode side light emitting layer host material and the central light-emitting layer of, Ip ₁ and the ionization potential of a constituent material for the hole injecting and transporting layer, the anode-side emission layer When the ionization potential of the host material is Ip ₄ , and the ionization potential of the constituent material of the central light emitting layer is Ip ₂ , Ip ₁ = Ip ₄ ≦ Ip ₂ is usually satisfied. In this case, since the host material of the anode side light emitting layer and the constituent material of the central light emitting layer are different, as described above, when Ip ₁ = Ip ₄ = Ip ₂ , Ea ₁ ≠ Ea ₂ and Ea ₄ ≠ Ea ₂ , and When Ea ₁ = Ea ₄ = Ea ₂ , Ip ₁ ≠ Ip ₂ and Ip ₄ ≠ Ip ₂ .
Among them, it is preferable that Ip ₁ = Ip ₄ <Ip ₂ . This is because the presence of some energy barrier in the hole transport from the anode side light emitting layer to the central light emitting layer can control the injection of holes and increase the light emission efficiency.

In the case of Ip ₁ = Ip ₄ <Ip ₂ , the difference between Ip ₁ and Ip ₄ and Ip ₂ is as follows. Although it differs depending on the situation, specifically, it is preferably 0.1 eV or more, and more preferably 0.2 eV or more. Even when the difference between Ip ₄ and Ip ₂ is relatively large, holes can be transported from the anode side light emitting layer to the central light emitting layer if the driving voltage is relatively high.

The relationship between the ionization potential of the constituent material of the central light-emitting layer and the electron injecting and transporting layer, when Ip ₂ and an ionization potential of a constituent material of the central light-emitting layer, the ionization potential of the constituent material of the electron injection transport layer was Ip _3, Ip ₂ ≧ Ip ₃ is sufficient. As the relationship between the electron affinity of the constituent material of the central light-emitting layer and the electron injecting and transporting layer, when an electron affinity Ea ₂ of the material of the central light-emitting layer, the electron affinity of the constituent material of the electron injection transport layer was Ea ₃ Usually, Ea ₂ ≦ Ea ₃ .

Among them, the central light emitting layer contains a host material and a light emitting dopant, and it is preferable that the host material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are the same. relation of the ionization potential and the electron affinity of the material, as illustrated in FIG. 3, it is preferable that Ip ₂ = Ip ₃ and Ea ₂ = Ea _3. This is because the electron injection barrier from the electron injection transport layer to the central light emitting layer is eliminated, and the drive voltage can be lowered.

On the other hand, the relationship between the ionization potential and the electron affinity of the constituent materials of the central light emitting layer and the electron injecting and transporting layer is preferably Ip ₂ > Ip ₃ and Ea ₂ <Ea ₃ as illustrated in FIG. This is because if Ip ₂ > Ip ₃ and Ea ₂ <Ea ₃ , the band gap energy of the constituent material of the central light emitting layer can be made relatively large. For example, when the central light-emitting layer contains a host material and a light-emitting dopant, the host material and the light-emitting dopant have an ionization potential and an electron affinity that satisfy a predetermined relationship in order to improve luminous efficiency. It becomes easy to select the material and the luminescent dopant. In addition, since Ea ₂ <Ea ₃ , the presence of some energy barrier in the electron transport from the electron injection transport layer to the central light emitting layer can control the electron injection and increase the light emission efficiency. is there.

In the case of Ip ₂ > Ip ₃ , the difference between Ip ₂ and Ip ₃ varies depending on the constituent materials of the central light emitting layer and the electron injecting and transporting layer. Preferably, it is 0.2 eV or more.

In the case of Ea ₂ <Ea ₃ , the difference between Ea ₂ and Ea ₃ varies depending on the constituent materials of the central light emitting layer and the electron injecting and transporting layer. Specifically, the difference may be 0.1 eV or more. Preferably, it is 0.2 eV or more and 0.5 eV or less. Even when the difference between Ea ₂ and Ea ₃ is relatively large, electrons can be transported from the electron injecting and transporting layer to the central light emitting layer if the driving voltage is relatively high.

The relationship between the ionization potential and the electron affinity of the constituent materials of the hole injection transport layer and the electron injection transport layer is not particularly limited.
Among these, since it is preferable that the hole injection transport layer and the electron injection transport layer contain the same bipolar material, the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , and the ionization potential of the constituent material of the electron injection transport layer is When the potential is Ip ₃ , the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ , and the electron affinity of the constituent material of the electron injecting and transporting layer is Ea ₃ , as illustrated in FIG. 2, Ip ₁ = Ip ₃ and Ea ₁ = Ea ₃ are preferred.
On the other hand, the host material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are the same. As illustrated in FIG. 3, the relationship between the ionization potential and the electron affinity of the constituent materials of the central light emitting layer and the electron injecting and transporting layer is Ip _2. = Ip ₃ and Ea ₂ = Ea _{3 Since} the constituent materials of the hole injection transport layer and the central light emitting layer are different, the constituent materials of the hole injection transport layer and the electron injection transport layer are also different. relation of the ionization potential and electron affinity of the constituent material of injecting and transporting layer and the electron injecting and transporting layer becomes _{Ea 1 ≠ Ea 3, Ea 1} = Ip 1 ≠ Ip 3 when Ea ₃ when Ip ₁ = Ip _3.

In the present embodiment, as illustrated in FIG. 4, a second hole injection / transport layer 9 may be formed between the anode 3 and the hole injection / transport layer 4.
In this case, assuming that the electron affinity of the constituent material of the second hole injecting and transporting layer 9 is Ea ₆ and the electron affinity of the constituent material of the hole injecting and transporting layer 4 is Ea ₁ , Ea ₆ <Ea as illustrated in FIG. ₁ is preferred. Even if electrons penetrate to the anode side and electrons are injected into the hole injecting and transporting layer, the second hole injecting and transporting is caused by the existence of an energy barrier between the second hole injecting and transporting layer and the hole injecting and transporting layer. Electron penetration from the layer to the anode side can be prevented. Therefore, deterioration at the interface between the second hole injecting and transporting layer and the anode can be suppressed. Further, the constituent material of the second hole injecting and transporting layer has a wider range of material selection than the constituent material of the hole injecting and transporting layer, and a material suitable for the second hole injecting and transporting layer can be used. . Thereby, it can be set as an advantageous structure in the hole injection from an anode to a 2nd hole injection transport layer.

In the case of Ea ₆ <Ea ₁ , the difference between Ea ₆ and Ea ₁ is different depending on the constituent materials of the second hole injection transport layer and the hole injection transport layer, but specifically 0.1 eV It is preferable to set it above, and more preferably in the range of 0.2 eV to 2.0 eV.

On the other hand, as the relationship of the electron affinity of the constituent materials of the second hole injecting and transporting layer and the hole injecting and transporting layer, it is also preferable that Ea ₆ ≧ Ea ₁ as illustrated in FIG. This is because there is no charge accumulation at the interface between the second hole injection transport layer and the hole injection transport layer during driving, and deterioration can be suppressed.

In the above case, if the ionization potential of the constituent material of the second hole injection transport layer 9 is Ip ₆ and the ionization potential of the constituent material of the hole injection transport layer 4 is Ip ₁ , usually Ip ₆ ≦ Ip ₁ . Among them, it is preferable that Ip ₆ <Ip ₁ as illustrated in FIG. When Ip ₁ and Ip ₄ are relatively large, it becomes difficult for holes to be transported to the anode-side light emitting layer, but the second hole injecting and transporting layer and hole injecting so that Ip ₆ <Ip ₁ = Ip ₄ It is because holes can be smoothly transported to the anode side light emitting layer by forming the transport layer and the anode side light emitting layer. In addition, the presence of a certain energy barrier in the hole transport from the second hole injecting and transporting layer to the hole injecting and transporting layer makes it possible to control the injection of holes and increase the light emission efficiency.

In the case of Ip ₆ <Ip ₁ , the difference between Ip ₆ and Ip ₁ varies depending on the constituent materials of the second hole injection transport layer and the hole injection transport layer, but specifically 0.1 eV. It is preferable to set it as the above, More preferably, it exists in the range of 0.2 eV-0.5 eV.

In the present embodiment, as illustrated in FIG. 4, a second electron injection transport layer 10 may be formed between the electron injection transport layer 7 and the cathode 8.
In this case, if the ionization potential of the constituent material of the electron injection / transport layer 7 is Ip ₃ and the ionization potential of the constituent material of the second electron injection / transport layer 10 is Ip ₇ , Ip ₃ <Ip ₇ as illustrated in FIG. Preferably there is. Even if holes penetrate to the cathode side and holes are injected into the electron injecting and transporting layer, there is an energy barrier between the electron injecting and transporting layer and the second electron injecting and transporting layer. Hole penetration to the cathode side can be prevented. Therefore, it is possible to suppress deterioration at the interface between the second electron injecting and transporting layer and the cathode. In addition, the constituent material of the second electron injecting and transporting layer has a wider range of material selection than the constituent material of the electron injecting and transporting layer, and a material suitable for the second electron injecting and transporting layer can be used. Thereby, it can be set as an advantageous structure in the electron injection from a cathode to the 2nd electron injection transport layer.

In the case of Ip ₃ <Ip ₇ , the difference between Ip ₃ and Ip ₇ varies depending on the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer, but specifically 0.1 eV or more. More preferably, it is in the range of 0.2 eV to 2.0 eV.

On the other hand, as the relationship between the ionization potentials of the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer, it is also preferable that Ip ₃ ≧ Ip ₇ as illustrated in FIG. This is because there is no charge accumulation at the interface between the second electron injecting and transporting layer and the electron injecting and transporting layer during driving, and deterioration can be suppressed.

In the above case, when the electron affinity of the constituent material of the electron injecting and transporting layer 7 is Ea ₃ and the electron affinity of the constituent material of the second electron injecting and transporting layer 10 is Ea ₇ , usually Ea ₃ ≦ Ea ₇ is satisfied. Among them, it is preferable that Ea ₃ <Ea ₇ as illustrated in FIG. When the energy gap of the central light emitting layer is relatively large, it becomes difficult for electrons to be transported to the central light emitting layer, but the central light emitting layer, the electron injection transport layer, and the second electron so that Ea ₂ ≦ Ea ₃ <Ea ₇ This is because the injection transport layer is formed, whereby electrons can be smoothly transported to the central light emitting layer. In addition, since there is a slight energy barrier in electron transport from the second electron injection transport layer to the electron injection transport layer, electron injection can be controlled and light emission efficiency can be increased.

In the case of Ea ₃ <Ea ₇ , the difference between Ea ₃ and Ea ₇ varies depending on the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer, and specifically 0.1 eV or more. More preferably, it is in the range of 0.2 eV to 0.5 eV.

In the present embodiment, as illustrated in FIG. 7, a third hole injection transport layer 11 may be formed between the second hole injection transport layer 9 and the hole injection transport layer 4.
In this case, the electron affinity of the constituent materials of the second hole injecting and transporting layer, the third hole injecting and transporting layer, and the hole injecting and transporting layer is expressed as Ea ₆ , when the electron affinity of the constituent material of the third hole injection / transport layer is Ea ₈ and the electron affinity of the constituent material of the hole injection / transport layer is Ea ₁ , Ea ₆ <Ea ₈ , as illustrated in FIG. It is preferable that Ea ₈ ≧ Ea ₁ . This is because deterioration at the interface between the anode and the second hole injection transport layer and the interface between the third hole injection transport layer and the hole injection transport layer can be suppressed. Further, since Ea ₆ <Ea ₈ , the range of options for the constituent material of the second hole injecting and transporting layer is widened.

In the case of Ea ₆ <Ea ₈ , the difference between Ea ₆ and Ea ₈ varies depending on the constituent materials of the second hole injection transport layer and the third hole injection transport layer, but specifically 0 0.1 eV or more is preferable, and more preferably in the range of 0.2 eV to 2.0 eV.

On the other hand, the relationship of the electron affinity of the constituent materials of the second hole injecting and transporting layer, the third hole injecting and transporting layer, and the hole injecting and transporting layer is Ea ₆ ≧ Ea ₈ ≧ Ea ₁ as illustrated in FIG. It is also preferable that there is. This is because deterioration at the interface of each layer during driving can be suppressed.

In the above case, the relationship between the ionization potentials of the constituent materials of the second hole injection transport layer, the third hole injection transport layer, and the hole injection transport layer is as follows. Ip ₆ , where the ionization potential of the constituent material of the third hole injection transport layer is Ip ₈ , and the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , usually Ip ₆ ≦ Ip ₈ ≦ Ip ₁ The Among them, it is preferable that Ip ₆ <Ip ₈ <Ip ₁ . When the difference between Ip ₆ and Ip ₈ is relatively large, holes are hardly transported, but between the second hole injecting and transporting layer so that Ip ₆ <Ip ₈ <Ip ₁ This is because the holes can be transported smoothly by forming the third hole injecting and transporting layer. In addition, the presence of a slight energy barrier can control the injection of holes and increase the light emission efficiency.

In the case of Ip ₆ <Ip ₈ <Ip ₁ , the difference between Ip ₆ and Ip _{8 and} the difference between Ip ₈ and Ip ₁ are the hole injection transport layer, the second hole injection transport layer, and the third hole injection. Although it differs depending on the constituent material of the transport layer, specifically, it is preferably set to 0.1 eV or more, and more preferably in the range of 0.2 eV to 0.5 eV.

In the present embodiment, as illustrated in FIG. 7, a third electron injection / transport layer 12 may be formed between the electron injection / transport layer 7 and the second electron injection / transport layer 10.
In this case, the electron injecting and transporting layer, the relation of the ionization potential of a constituent material of the third electron injecting and transporting layer and the second electron injecting and transporting layer, the ionization potential of the constituent material for the electron injecting and transporting layer Ip _3, the third electronic injection When the ionization potential of the constituent material of the transport layer is Ip ₉ and the ionization potential of the constituent material of the second electron injection transport layer is Ip ₇ , as shown in FIG. 8, Ip ₃ ≧ Ip ₉ and Ip ₉ <Ip ₇ Preferably there is. This is because deterioration at the interface between the electron injecting and transporting layer and the third electron injecting and transporting layer and at the interface between the second electron injecting and transporting layer and the cathode can be suppressed. Moreover, since Ip ₉ <Ip ₇ , the range of options for the constituent material of the second electron injecting and transporting layer is widened.

In the case of Ip ₉ <Ip ₇ , the difference between Ip ₉ and Ip ₇ varies depending on the constituent materials of the second electron injection transport layer and the third electron injection transport layer, but specifically 0.1 eV It is preferable to set it as the above, More preferably, it exists in the range of 0.2 eV-2.0 eV.

On the other hand, the relationship between the ionization potentials of the constituent materials of the electron injection / transport layer, the third electron injection / transport layer, and the second electron injection / transport layer is Ip ₃ ≧ Ip ₉ ≧ Ip ₇ as illustrated in FIG. preferable. This is because deterioration at the interface of each layer during driving can be suppressed.

In the above case, the electron injecting and transporting layer, the relation of the electron affinity of the constituent material of the third electron injecting and transporting layer and the second electron injecting and transporting layer, the electron affinity of the constituent material of the electron injecting and transporting layer Ea _3, the third electronic When the electron affinity of the constituent material of the injection / transport layer is Ea ₉ and the electron affinity of the constituent material of the second electron injection / transport layer is Ea ₇ , usually, Ea ₃ ≦ Ea ₉ ≦ Ea ₇ . Among them, it is preferable that Ea ₃ <Ea ₉ <Ea ₇ . When the difference between Ea ₃ and Ea ₇ is relatively large, electrons are difficult to be transported, but the _third electron injection transport layer and the second electron injection transport layer are arranged so that Ea ₃ <Ea ₉ <Ea ₇ . This is because electrons can be transported smoothly by forming the electron injecting and transporting layer. In addition, the presence of a slight energy barrier can control the injection of electrons and increase the light emission efficiency.

In the case of Ea ₃ <Ea ₉ <Ea ₇ , the difference between Ea ₃ and Ea _{9 and} the difference between Ea ₉ and Ea ₇ are the difference between the electron injection transport layer, the second electron injection transport layer, and the third electron injection transport layer. Although it differs depending on the constituent material, specifically, it is preferably 0.1 eV or more, more preferably in the range of 0.2 eV to 0.5 eV.

  In addition, the measuring method of the ionization potential and electron affinity of the constituent material of each layer is as having mentioned above.

2. Anode-side light-emitting layer The anode-side light-emitting layer in this embodiment contains a host material and a light-emitting dopant, and is formed between the hole-injecting and transporting layer and the central light-emitting layer. The constituent material of the hole injection transport layer is the same, and the host material of the anode side light emitting layer and the constituent material of the central light emitting layer are different. The anode side light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

  The host material of the anode side light emitting layer may be the same as the constituent material of the hole injecting and transporting layer, and examples thereof include a dye material, a metal complex material, and a polymer material.

  Examples of dye-based materials include cyclopentadiene derivatives, tetraphenylbutadiene derivatives, triphenylamine derivatives, oxadiazole derivatives, pyrazoloquinoline derivatives, distyrylbenzene derivatives, distyrylarylene derivatives, silole derivatives, thiophene ring compounds, pyridine Examples thereof include a ring compound, a perinone derivative, a perylene derivative, an oligothiophene derivative, a trifumanylamine derivative, a coumarin derivative, an oxadiazole dimer, and a pyrazoline dimer.

Examples of metal complex materials include aluminum quinolinol complex, benzoquinolinol beryllium complex, benzoxazole zinc complex, benzothiazole zinc complex, azomethyl zinc complex, porphyrin zinc complex, europium complex, iridium metal complex, platinum metal complex, etc. Al, Zn, Be, Ir, Pt, etc., or rare earth metals such as Tb, Eu, Dy, etc., and the ligand has an oxadiazole, thiadiazole, phenylpyridine, phenylbenzimidazole, quinoline structure, etc. A metal complex etc. can be mentioned. Specifically, tris (8-hydroxyquinolinolato) aluminum (Alq ₃ ) can be used.

  Examples of the polymer material include polyparaphenylene vinylene derivatives, polythiophene derivatives, polyparaphenylene derivatives, polysilane derivatives, polyacetylene derivatives, polyvinylcarbazole, polyfluorenone derivatives, polyfluorene derivatives, polyquinoxaline derivatives, polydialkylfluorene derivatives, and Examples thereof include copolymers thereof. Moreover, what polymerized said pigment-type material and metal complex-type material is also mentioned.

In this embodiment, the host material of the anode side light emitting layer is preferably a bipolar material.
The “bipolar material” is a material that can stably transport both holes and electrons, and when an electron unipolar device is manufactured using a material doped with a reducing dopant. It refers to a material that can transport electrons stably, and can transport holes stably when a unipolar device of holes is manufactured using a material doped with an oxidizing dopant. When producing a unipolar device, specifically, an electron unipolar device is produced using a material doped with Cs or 8-hydroxyquinolinolatolithium (Liq) as a reducing dopant, and is oxidized. A hole unipolar device can be fabricated using a material doped with V ₂ O ₅ or MoO ₃ as a dopant.
This is because the use of the bipolar material for the anode side light emitting layer can effectively suppress the deterioration at the interface of each layer during driving.

  Examples of the bipolar material include a distyrylarene derivative, a polyaromatic compound, an aromatic condensed ring compound, a carbazole derivative, and a heterocyclic compound. Specifically, 4,4′-bis (2,2-diphenyl-ethen-1-yl) diphenyl represented by the following formula (4,4′-bis (2,2-diphenyl-ethen-1-yl) diphenyl (DPVBi), 4,4'-bis (carbazol-9-yl) biphenyl (CBP), 2,2 ', 7,7'-tetrakis ( Carbazol-9-yl) -9,9'-spiro-bifluorene (2,2 ', 7,7'-tetrakis (carbazol-9-yl) -9,9'-spiro-bifluorene; spiro-CBP), 4 , 4 ''-di (N-carbazolyl) -2 ', 3', 5 ', 6'-tetraphenyl-p-terphenyl (4,4' '-di (N-carbazolyl) -2', 3 ' , 5 ', 6'-tetraphenyl-p-terphenyl (CzTT), 1,3-bis (carbazole-9-yl) -benzene (m-CP) 3-tert-butyl-9,10-di (naphtha-2-yl) anthracene (TBADN), and derivatives thereof Can be mentioned.

  Any material that is confirmed to be capable of transporting both hole and electron carriers by the above-described method can be used as the bipolar material in the present invention.

  The light emitting dopant of the anode side light emitting layer is not particularly limited as long as it emits fluorescence or phosphorescence. Examples of the luminescent dopant include perylene derivatives, coumarin derivatives, rubrene derivatives, quinacridone derivatives, squalium derivatives, porphyrin derivatives, styryl dyes, tetracene derivatives, pyrazoline derivatives, decacyclene, phenoxazone, quinoxaline derivatives, carbazole derivatives, fluorene derivatives, iridium (Ir ) Compounds, platinum compounds, gold compounds, osmium compounds, ruthenium (Ru) compounds, rhenium (Re) compounds, and the like. More specifically, 2,5,8,11-tetra-tert-butylperylene (2,5,8,11-Tetra-tert-butylperylene) (perylene derivative), 2,3,6,7-tetrahydro- 1,1,7,7, -Tetramethyl-1H, 5H, 11H-10- (2-benzothiazolyl) quinolidino- [9,9a, 1gh] coumarin (C545t) (2,3,6,7-Tetrahydro-1 , 1,7,7, -tetramethyl-1H, 5H, 11H-10- (2-benzothiazolyl) quinolizino- [9,9a, 1gh] coumarin (C545t)) (coumarin derivative), (5,6,11,12 ) -Tetraphenylnaphthacene ((5,6,11,12) -Tetraphenylnaphthacene) (rubrene derivative) and Tris (2-phenylpyridine) iridium (III) (Ir) (ppy) 3), Tris (1-phenylisoquinoline) iridium (III); Ir (piq) 3), bis (3,5-difluoro-2- (2-pyridyl) ) Phenyl- (2-carboxypyridyl) iridium (III) (Bis (3,5-difluoro-2- (2-pyridyl) phenyl- (2-carboxypyridyl) iridium (III); FIrpic)) Compound).

Regarding the relationship between the electron affinity and ionization potential of the host material and the luminescent dopant, Ea _h <Ea _d when the electron affinity of the host material is Ea _h and the electron affinity of the luminescent dopant is Ea _d . the ionization potential Ip _h, when the ionization potential of the light-emitting dopant was Ip _d, it is preferable that Ip _h> Ip _d. This is because, when the electron affinity and ionization potential of the host material and the luminescent dopant satisfy the above relationship, holes and electrons are trapped by the luminescent dopant, so that the luminous efficiency can be improved.

  Here, the ionization potential and electron affinity of the host material and the light-emitting dopant are obtained as follows. The ionization potential is obtained by UPS (ultraviolet photoelectron spectroscopy) (for example, measuring instrument name “AC-2” manufactured by Riken Keiki Co., Ltd.). On the other hand, as a method for measuring electron affinity, first, HOMO energy is obtained by UPS (ultraviolet photoelectron spectroscopy) (for example, “AC-2” manufactured by Riken Keiki Co., Ltd.), and then an energy gap measurement value by light absorption and the above HOMO energy. The method of calculating from is adopted.

  In the anode side light emitting layer, the light emitting dopant concentration may be constant in the layer thickness direction, and the light emitting dopant concentration may have a distribution in the layer thickness direction.

  The anode side light emitting layer may contain two or more kinds of light emitting dopants. For example, when three types of light emitting dopants of red, blue, and green corresponding to the three primary colors of light are used, two types of light emitting dopants are included in the anode side light emitting layer, and one type of light emitting dopant is included in the central light emitting layer. White light can be obtained by causing each of the three light emitting dopants to emit light. In addition, for example, when the difference in excitation energy between the host material and the luminescent dopant is relatively large, energy transfer is facilitated by further adding a luminescent dopant having an excitation energy between the excitation energy of the host material and the luminescent dopant. The luminous efficiency can be improved. Furthermore, for example, by containing a luminescent dopant that easily transports holes rather than electrons and a luminescent dopant that easily transports electrons rather than holes, the hole and electrons injected into the anode side light emitting layer are balanced. And the luminous efficiency can be improved.

When the anode side light emitting layer contains two or more kinds of light emitting dopants, each light emitting dopant may emit light or only one kind may emit light. Depending on the magnitude, distribution state, and concentration of the excitation energy of the luminescent dopant, light emission of one or each luminescent dopant can be obtained.
In particular, when white light is obtained using three types of red, blue, and green light emitting dopants corresponding to the three primary colors of light, the anode side light emitting layer contains two types of light emitting dopants, and the central light emitting layer has one type. It is preferable that each of the three types of light-emitting dopants emit light.

When the anode side light emitting layer contains a first light emitting dopant and a second light emitting dopant having an excitation energy smaller than the excitation energy of the host material and larger than the excitation energy of the first light emitting dopant, the first light emitting dopant and As a 2nd light emission dopant, it can select from the above-mentioned light emission dopant suitably, and can be used. For example, when Alq ₃ that emits green light is used as the host material and DCM that emits red light is used as the first light emitting dopant, by using rubrene that emits yellow light as the second light emitting dopant, Alq ₃ (host material) → rubrene (first Energy transfer can be caused smoothly in the order of two light emitting dopants) → DCM (first light emitting dopant).

  When the anode side light emitting layer contains a third light emitting dopant that easily transports holes rather than electrons and a fourth light emitting dopant that easily transports electrons than holes, the third light emitting dopant and the fourth light emitting dopant Can be used by appropriately selecting from the above-mentioned light emitting dopants according to the combination of the constituent materials of the hole injecting and transporting layer and the electron injecting and transporting layer and the host material of the anode side light emitting layer. For example, when TBADN is used for the hole injecting and transporting layer and the electron injecting and transporting layer, CBP is used for the host material of the anode side light emitting layer, and rubrene is used for the light emitting dopant, rubrene is a light emitting dopant that easily transports holes rather than electrons. Become. For example, when TBADN is used for the hole injecting and transporting layer and the electron injecting and transporting layer, CBP is used for the host material of the anode side light emitting layer, and anthracenediamine is used for the light emitting dopant, anthracene diamine is easier to transport electrons than holes. It becomes a luminescent dopant.

  Note that whether the anode-side light-emitting layer containing the host material and the light-emitting dopant is more likely to transport holes than electrons or whether it is easier to transport electrons than holes is a single thing with the host material. This can be confirmed by evaluating the angular dependence of the radiation pattern of the emission spectrum of the organic EL device having the anode side light emitting layer containing the light emitting dopant. That is, it can be confirmed from the wavelength of the emission spectrum, the refractive index of the material, the optical path length until light is extracted from the anode side light emitting layer by the organic EL element, and the angle dependency of the radiation pattern.

  When the anode side light emitting layer contains a third light emitting dopant that easily transports holes rather than electrons and a fourth light emitting dopant that easily transports electrons than holes, the third light emitting dopant in the doped region and Each concentration of the fourth light emitting dopant may be constant in the thickness direction of the layer, or may have a distribution in the thickness direction of the layer. Usually, the concentration of the third light-emitting dopant and the fourth light-emitting dopant in the anode side light-emitting layer is fixed in the thickness direction of the layer.

  The anode side light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant.

  In the example shown in FIG. 10A, the anode side light emitting layer 5a has a doped region 21 and a non-doped region 22, and the non-doped region 22 is disposed on the central light emitting layer 6 side. For example, when energy transfer can occur between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the center light emitting layer, by providing a non-doped region at the interface between the anode side light emitting layer and the central light emitting layer, The energy transfer is less likely to occur and the light emission efficiency can be improved. Specifically, when the anode side light emitting layer and the central light emitting layer contain light emitting dopants that emit different colors, and each light emitting dopant emits light to obtain white light, the anode side light emitting layer and the center light emitting layer It is preferable that a non-doped region is provided at the interface of the light emitting layer. In addition, when one of the anode side light emitting layer and the central light emitting layer contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant, each of the light emitting dopants emits light, respectively. It is preferable that a non-doped region is provided at the interface of the light emitting layer.

  In the example shown in FIG. 10B, the anode side light emitting layer 5a has two doped regions 21a and 21b and one non-doped region 22, and a non-doped region between the two doped regions 21a and 21b. 22 is arranged. For example, in the case where energy transfer can occur between the light-emitting dopant in the doped region 21a and the light-emitting dopant in the doped region 21b, the non-doped region 22 is disposed between the two doped regions 21a and 21b, so that the above energy is obtained. It is difficult to cause movement and light emission efficiency can be improved. Specifically, when the two doped regions contain light emitting dopants that emit different colors, and each light emitting dopant emits light to obtain white light, a non-doped region between the two doped regions. Is preferably arranged. In addition, when one of the two doped regions contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant, and each of the light emitting dopants emits light, the non-doped region is located between the two doped regions. Is preferably arranged.

  Thus, luminous efficiency can be improved because the anode side light emitting layer has a non-doped region.

  Note that the non-doped region that does not contain a light-emitting dopant means a region that does not substantially contain a light-emitting dopant. Specifically, a non-doped region refers to a region formed by closing a shutter of a light emitting dopant deposition source when a host material and a light emitting dopant are co-evaporated to form a light emitting layer. Further, when the thickness of the non-doped region is 10 nm or more, the non-doped region means that the content of the light-emitting dopant is 10% or less, preferably 5 when the content of the light-emitting dopant in the adjacent doped region is 100%. % Or less, more preferably 1% or less.

  The arrangement of the doped region and the non-doped region is not particularly limited as long as the anode side light emitting layer has an arrangement of one or more doped regions and one or more non-doped regions. For example, as shown in FIG. 10A, the anode side light emitting layer 5a may have a non-doped region 22 on the central light emitting layer 6 side, and as shown in FIG. You may have the non-dope area | region 22 pinched | interposed into the some dope area | regions 21a and 21b. Although not shown, the anode side light emitting layer may have two doped regions and two non-doped regions, and the doped regions and the non-doped regions may be alternately arranged.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant.

  The number of non-doped regions may be one or more, but is usually about 1-2. On the other hand, the number of doped regions may be one or more, but is usually about 1-2.

  The doped region may be a region containing a host material and a luminescent dopant. In the doped region, the luminescent dopant concentration may be constant in the layer thickness direction, and the luminescent dopant concentration has a distribution in the layer thickness direction. You may do it. Usually, in the doped region, the luminescent dopant concentration is constant in the thickness direction of the layer.

  As described above, the anode side light emitting layer may contain two or more kinds of light emitting dopants. In this case, for example, one doped region may contain two or more kinds of light emitting dopants, The two doped regions may contain different types of light emitting dopants.

  In the case where the two doped regions contain different types of light emitting dopants, for example, three types of light emitting dopants of red, blue, and green corresponding to the three primary colors of light are used. When each of the doped regions contains one type of light emitting dopant and the central light emitting layer contains one type of light emitting dopant, the non-doped region between the two doped regions in the anode side light emitting layer Is arranged, the energy transfer between the light-emitting dopants can be suppressed, the light-emitting dopants can each emit light, and the light emission efficiency can be improved and white light can be obtained.

  The thickness of the anode side light emitting layer is not particularly limited as long as it can provide a function of emitting light by providing a recombination field between electrons and holes, and is, for example, about 1 nm to 200 nm. Can be set. In particular, the thickness of the anode side light emitting layer is in the range of 3 nm to 100 nm in order to improve the light emission efficiency by increasing the injection balance of holes and electrons by increasing the thickness of the anode side light emitting layer. More preferably, it is in the range of 5 nm to 80 nm.

  When the anode side emission layer has a doped region and a non-doped region, the thickness of the non-doped region can form a uniform film, providing a field for recombination of electrons and holes to emit light The thickness is not particularly limited as long as it can secure a doped region to be formed. Specifically, the thickness of the non-doped region is preferably about 0.1 nm to 30 nm, more preferably in the range of 0.5 nm to 20 nm, and still more preferably in the range of 0.8 nm to 15 nm.

As a method for forming the anode side light emitting layer, a method of co-evaporating a host material and a light emitting dopant is preferably used. At this time, an anode-side light emitting layer having a doped region and a non-doped region can be formed by opening and closing a shutter of the light emitting dopant vapor deposition source or controlling the vapor deposition rate of the light emitting dopant.
In addition, when a thin film can be formed by application from a solution, a spin coating method, a dip coating method, or the like can be used. In this case, the host material and the luminescent dopant may be dispersed in an inert polymer.

  Moreover, when giving distribution to the light emission dopant density | concentration in an anode side light emitting layer, the method of changing the vapor deposition rate of host material and a light emission dopant continuously or periodically can be used, for example.

3. Central light-emitting layer The central light-emitting layer in this embodiment is formed between the anode-side light-emitting layer and the electron-injecting and transporting layer. The constituent material of the central light-emitting layer and the host material of the anode-side light-emitting layer are different, and the central light-emitting layer The constituent material of the layer and the constituent material of the hole injecting and transporting layer are also different. The central light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

  Examples of the constituent material of the central light emitting layer include a dye material, a metal complex material, and a polymer material. In addition, since it described in the item of the said anode side light emitting layer about the pigment | dye type | system | group material, a metal complex type | system | group material, and a polymeric material, description here is abbreviate | omitted.

  Further, the constituent material of the central light emitting layer may be a bipolar material. This is because the use of the bipolar material for the central light emitting layer can effectively suppress the deterioration at the interface of each layer during driving. Since the bipolar material is described in detail in the section of the anode side light emitting layer, description thereof is omitted here.

  In the central light emitting layer, a light emitting dopant that emits fluorescent light or phosphorescent light may be added for the purpose of improving the light emission efficiency and changing the light emission wavelength. That is, the central light-emitting layer may contain a host material such as the above-described dye-based material, metal complex-based material, polymer-based material, or bipolar material, and a light-emitting dopant. In addition, since it described in the term of the said anode side light emitting layer about the light emission dopant, description here is abbreviate | omitted.

  When the central light emitting layer contains a host material and a light emitting dopant, it is preferable that the host material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are the same. This is because the electron injection barrier from the electron injection transport layer to the central light emitting layer is eliminated, and the drive voltage can be lowered.

  On the other hand, as described later, when the hole injecting and transporting layer and the electron injecting and transporting layer contain the same bipolar material, the constituent material of the hole injecting and transporting layer is different from the constituent material of the central light emitting layer, The host material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are different.

  In the case where the central light emitting layer contains a host material and a light emitting dopant, the relationship between the electron affinity and ionization potential of the host material and the light emitting dopant, the light emitting dopant concentration in the central light emitting layer, and the central light emitting layer include two or more kinds of the central light emitting layer. Since the case of containing a light emitting dopant is the same as that described in the section of the anode side light emitting layer, the description thereof is omitted here.

  When the central light emitting layer contains a host material and a light emitting dopant, the central light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant.

  In the example shown in FIG. 11A, the central light emitting layer 6 has a doped region 21 and a non-doped region 22, and the non-doped region 22 is disposed on the anode light emitting layer 5a side. For example, when energy transfer can occur between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the center light emitting layer, by providing a non-doped region at the interface between the anode side light emitting layer and the central light emitting layer, The energy transfer is less likely to occur and the light emission efficiency can be improved.

  In the example shown in FIG. 11B, the central light emitting layer 6 has a doped region 21 and a non-doped region 22, and the non-doped region 22 is disposed on the electron injection / transport layer 7 side. For example, in the case where energy transfer can occur from the light emitting dopant in the central light emitting layer 6 to the constituent material of the electron injection transport layer 7, the central light emission layer 6 has the non-doped region 22 on the electron injection transport layer 7 side, so that the energy transfer is performed. Can be prevented and the luminous efficiency can be improved.

  In the example shown in FIG. 11C, the central light emitting layer 6 has two doped regions 21a and 21b and one non-doped region 22, and the non-doped region 22 is provided between the two doped regions 21a and 21b. Is arranged. For example, in the case where energy transfer can occur between the light-emitting dopant in the doped region 21a and the light-emitting dopant in the doped region 21b, the non-doped region 22 is disposed between the two doped regions 21a and 21b, so that the above energy is obtained. It is difficult to cause movement and light emission efficiency can be improved.

  Thus, luminous efficiency can be improved because the central light emitting layer has a non-doped region.

  The arrangement of the doped region and the non-doped region is not particularly limited as long as the central light emitting layer has one or more doped regions and one or more non-doped regions. For example, the central light emitting layer 6 may have a non-doped region 22 on the anode side light emitting layer 5a side as shown in FIG. 11A, and the central light emitting layer 6 has electron injection as shown in FIG. A non-doped region 22 may be provided on the transport layer 7 side, and as shown in FIG. 11C, the central light emitting layer 6 has a non-doped region 22 sandwiched between two doped regions 21a and 21b. Also good. Although not shown, the central light emitting layer may have two doped regions and three non-doped regions, and the doped regions and the non-doped regions may be alternately arranged.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant. Among them, it is preferable to appropriately select the arrangement of the doped region and the non-doped region so that the injection balance of holes and electrons can be obtained.

In the organic EL element illustrated in FIG. 11B, since the central light emitting layer 6 has the non-doped region 22 on the electron injection transport layer 7 side, the light emitting dopant performs electron injection at the interface between the electron injection transport layer and the central light emission layer. Electron injection from the electron injecting and transporting layer to the central light emitting layer can be improved without hindering.
Here, in this embodiment, the relationship between the ionization potentials of the constituent materials of the central light emitting layer and the electron injection transport layer is Ip ₂ ≧ Ip ₃ , and the holes injected into the central light emitting layer are prevented from penetrating to the counter electrode. Since the blocking layer to be provided is not provided, it is difficult to balance the holes and electrons injected into the light emitting layer in the same manner as an organic EL element having a conventional blocking layer.
On the other hand, in the organic EL element illustrated in FIG. 11B, the central light emitting layer has a non-doped region on the electron injecting and transporting layer side, whereby charge trapping by the light emitting dopant can be controlled. An efficient element can be obtained. For example, when the luminescent dopant is more likely to transport holes than electrons, hole injection tends to be excessive. In this case, since the central light emitting layer has a non-doped region on the electron injecting and transporting layer side, the light emission efficiency can be improved. This is injected from the anode into the central light emitting layer by providing a non-doped region on the electron injection transport layer side (cathode side) of the central light emitting layer and providing a doped region on the anode light emitting layer side (anode side) of the central light emitting layer. It is thought that this is because more holes are trapped by the light-emitting dopant in the central light-emitting layer, and more trapped by the light-emitting dopant, particularly on the anode side, and do not penetrate into the cathode. That is, when the central light emitting layer has a non-doped region on the electron injecting and transporting layer side, it is useful when hole injection is excessive.

  The number of non-doped regions may be one or more, but is usually about 1-3. On the other hand, the number of doped regions may be one or more, but is usually about 1-2.

  Since the other points of the doped region and the non-doped region are the same as those described in the section of the anode side light emitting layer, description thereof is omitted here.

  When the central light emitting layer also contains a host material and a light emitting dopant, the anode side light emitting layer and the central light emitting layer preferably contain different types of light emitting dopants. By laminating the anode side light emitting layer and the central light emitting layer, energy transfer between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the center light emitting layer is suppressed, and the light emitting dopant and center in the anode side light emitting layer are suppressed. This is because both of the light-emitting dopant in the light-emitting layer can be illuminated, so that the luminous efficiency can be increased and a desired emission color can be obtained.

  Among them, it is preferable that one of the anode side light emitting layer and the central light emitting layer, that is, a plurality of light emitting layers, contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant. When a fluorescent light emitting dopant and a phosphorescent light emitting dopant are contained in a single light emitting layer, energy transfer may occur between the fluorescent light emitting dopant and the phosphorescent light emitting dopant. Of the anode side light emitting layer and the central light emitting layer, By adding a fluorescent dopant in one and a phosphorescent dopant in the other, energy transfer can be suppressed between the fluorescent dopant and the phosphorescent dopant, and both the fluorescent dopant and the phosphorescent dopant can be emitted. This is because the emission efficiency can be increased and a desired emission color can be obtained.

  When the anode side light emitting layer and the central light emitting layer contain different kinds of light emitting dopants, the light emitting colors of the different kinds of light emitting dopants may be the same or different. Especially, it is preferable that the luminescent color of a different kind of light emission dopant differs. It is because a desired luminescent color can be obtained by making both the luminescent dopant in the anode side luminescent layer and the luminescent dopant in the central luminescent layer shine.

  In this embodiment, when obtaining white light, it is preferable to contain different kinds of light emitting dopants in the anode side light emitting layer and the central light emitting layer. For example, a combination of three types of luminescent dopants of red, blue, and green, two types of luminescent dopants of blue and yellow, two types of luminescent dopants of light blue and orange, and two types of luminescent dopants of green and purple can be given. . Among these, it is preferable to use three kinds of light emitting dopants of red, blue, and green.

  When three kinds of light emitting dopants of red, blue, and green are used, as described above, one of the anode side light emitting layer and the central light emitting layer may contain a fluorescent light emitting dopant and the other may contain a phosphorescent light emitting dopant. From preferred, for example, one contains a blue fluorescent dopant and the other contains a red phosphorescent dopant and a green fluorescent dopant, or one contains a red fluorescent dopant and the other contains a blue phosphorescent dopant and It is preferable to contain a green fluorescent luminescent dopant.

  Since the thickness of the central light emitting layer is the same as the thickness of the anode side light emitting layer, description thereof is omitted here.

As a method for forming the central light emitting layer, for example, a dry method such as a vacuum deposition method or a sputtering method, or a printing method, an ink jet method, a spin coating method, a casting method, a dipping method, a bar coating method, a blade coating method, a roll Examples thereof include wet methods such as a coating method, a gravure coating method, a flexographic printing method, and a spray coating method.
Note that the method for forming the central light emitting layer containing the host material and the light emitting dopant is the same as the method for forming the anode side light emitting layer, and thus the description thereof is omitted here.

  Further, in the case of providing a distribution of the light emitting dopant concentration in the central light emitting layer, for example, a method of changing the deposition rate of the host material and the light emitting dopant continuously or periodically can be used.

4). Hole Injecting and Transporting Layer The hole injecting and transporting layer used in this embodiment is formed between the anode and the anode-side light emitting layer, and the constituent material of the hole injecting and transporting layer and the host material of the anode-side emitting layer Are the same, and the constituent material of the hole injecting and transporting layer and the constituent material of the central light emitting layer are different. The hole injecting and transporting layer has a function of stably injecting or transporting holes from the anode to the anode side light emitting layer.

  The hole injection transport layer may be either a hole injection layer having a hole injection function and a hole transport layer having a hole transport function, or may be a hole injection function and a hole transport. It may be a single layer having both functions.

  The constituent material of the hole injecting and transporting layer is not particularly limited as long as it is a material that can stably transport holes injected from the anode to the anode side light emitting layer. What was illustrated to material can be used.

  Among these, the constituent material of the hole injecting and transporting layer is preferably a bipolar material. This is because the use of the bipolar material for the hole injecting and transporting layer can effectively suppress deterioration at the layer interface during driving. In addition, since it described in the term of the said anode side light emitting layer about the bipolar material, description here is abbreviate | omitted.

When the hole injecting and transporting layer and the later-described electron injecting and transporting layer contain bipolar materials, the bipolar materials contained in these layers may be the same or different.
Especially, it is preferable that the bipolar material contained in a positive hole injection transport layer and an electron injection transport layer is the same. This is because, if these bipolar materials are the same, even if holes penetrate into the electron injecting and transporting layer and electrons penetrate into the hole injecting and transporting layer, these layers are not easily deteriorated. Moreover, when forming these layers by a vacuum evaporation method etc., a common vapor deposition source can be used and it is advantageous on a manufacturing process.
On the other hand, as described above, when the host material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are the same, the constituent material of the hole injecting and transporting layer and the constituent material of the central light emitting layer are different. The bipolar materials contained in the hole injecting and transporting layer and the electron injecting and transporting layer are different.

The hole injection transport layer may have a region where an oxidizing dopant is mixed with an organic material (organic compound for hole injection transport layer) at least at the interface with the anode. A hole injection barrier from the anode to the hole injection transport layer by having a region in which the organic dopant for the hole injection transport layer is mixed with an oxidizing dopant at least at the interface with the anode. This is because the driving voltage can be reduced.
In the organic EL device, the hole injection process from the anode to the organic layer, which is basically an insulator, is oxidation of the organic compound on the anode surface, that is, formation of a radical cation state (Phys. Rev. Lett., 14 , 229 (1965)). By previously doping the hole injection transport layer in contact with the anode with an oxidizing dopant that oxidizes the organic compound, the energy barrier for hole injection from the anode can be lowered. In the hole injecting and transporting layer doped with the oxidizing dopant, an organic compound in a state oxidized by the oxidizing dopant (that is, a state in which electrons are donated) exists, so that the hole injection energy barrier is small, The driving voltage can be lowered compared to the organic EL element.

  The oxidizing dopant is not particularly limited as long as it has a property of oxidizing the organic compound for hole injection transport layer, but an electron accepting compound is usually used.

As the electron-accepting compound, both inorganic and organic substances can be used. When the electron-accepting compound is an inorganic substance, for example, Lewis such as ferric chloride, aluminum chloride, gallium chloride, indium chloride, antimony pentachloride, molybdenum trioxide (MoO ₃ ), vanadium pentoxide (V ₂ O ₅ ), etc. Examples include acids. Moreover, when an electron-accepting compound is organic substance, a trinitrofluorenone etc. are mentioned, for example.

Among them, as the electron-accepting compound, a metal oxide is _preferable, MoO _3, V 2 _{O 5} is preferably used.

  When the hole injecting and transporting layer has a region in which an oxidizing dopant is mixed with the organic compound for the hole injecting and transporting layer, the hole injecting and transporting layer has at least the above region at the interface with the anode. Well, for example, the hole injection transport layer may be uniformly doped with an oxidizing dopant, and the oxidizing dopant is continuously increased from the cathode side to the anode side. May be doped, or an oxidizing dopant may be locally doped only in the interface between the positive hole injection transport layer and the anode.

  The oxidizing dopant concentration in the hole injecting and transporting layer is not particularly limited, but the molar ratio of the organic compound for hole injecting and transporting layer and the oxidizing dopant is the organic compound for hole injecting and transporting layer: oxidation. It is preferable that it is in the range of 1:10 to 1:10. This is because if the ratio of the oxidizing dopant is less than the above range, the concentration of the organic compound for the hole injecting and transporting layer oxidized by the oxidizing dopant may be too low to obtain a sufficient doping effect. If the ratio of the oxidizing dopant exceeds the above range, the oxidizing dopant concentration in the hole injecting and transporting layer far exceeds the organic compound concentration for the hole injecting and transporting layer, and the holes oxidized by the oxidizing dopant. This is because the concentration of the organic compound for the injecting and transporting layer is extremely lowered, so that the doping effect may not be sufficiently obtained.

  As a film formation method of the hole injection transport layer, for example, a dry method such as a vacuum deposition method or a sputtering method, or a printing method, an ink jet method, a spin coating method, a casting method, a dipping method, a bar coating method, a blade coating method, etc. And wet methods such as a roll coating method, a gravure coating method, a flexographic printing method, and a spray coating method.

  Among these, as a method for forming a hole injection transport layer doped with an oxidizing dopant, a method of co-evaporating an organic compound for a hole injection transport layer and an oxidizing dopant is preferably used. In this co-evaporation technique, an oxidizing dopant having a relatively low saturation vapor pressure, such as ferric chloride and indium chloride, can be deposited in a crucible by a general resistance heating method. On the other hand, when the vapor pressure is high even at room temperature and the pressure inside the vacuum device cannot be kept below the predetermined vacuum level, the vapor pressure can be controlled by controlling the orifice (opening diameter) like a needle valve or mass flow controller, Alternatively, the vapor pressure may be controlled by cooling the sample holding portion so that the temperature can be controlled independently.

  Moreover, as a method of mixing an oxidizing dopant with an organic compound for a hole injection transport layer so that the content of the oxidizing dopant continuously increases from the cathode side to the anode side, for example, the above hole A method of continuously changing the deposition rate of the organic compound for the injection transport layer and the oxidizing dopant can be used.

  The thickness of the hole injecting and transporting layer is not particularly limited as long as the thickness of the hole injecting holes from the anode and transporting the holes to the light emitting layer is sufficiently exhibited. It can be set in the range of about 0.5 nm to 1000 nm, and in particular, it is preferably in the range of 5 nm to 500 nm.

  The thickness of the hole injecting and transporting layer doped with the oxidizing dopant is not particularly limited, but is preferably 0.5 nm or more. The hole injecting and transporting layer doped with the oxidizing dopant is not particularly limited because the organic compound for the hole injecting and transporting layer exists in the state of radical cation even in the absence of an electric field and acts as an internal charge. is there. Also, even if the hole injection / transport layer doped with the oxidizing dopant is made thick, the device voltage does not increase, so the distance between the anode and the cathode is set longer than in the case of a normal organic EL device. By doing so, the risk of a short circuit can be greatly reduced.

5). Electron Injecting and Transporting Layer The electron injecting and transporting layer used in this embodiment is formed between the cathode and the central light emitting layer. The electron injection / transport layer has a function of stably injecting or transporting electrons from the cathode to the central light emitting layer.

  The electron injection / transport layer may be one of an electron injection layer having an electron injection function and an electron transport layer having an electron transport function, or a single unit having both an electron injection function and an electron transport function. It may be a single layer.

  The constituent material of the electron injecting and transporting layer is not particularly limited as long as it is a material capable of stably transporting electrons injected from the cathode to the central light emitting layer, and is exemplified as the constituent material of the central light emitting layer. In addition to compounds, Ba, Ca, Li, Cs, Mg, Sr and other alkali metals or alkaline earth metals, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, lithium fluoride, cesium fluoride Alkali metal or alkaline earth metal fluorides, alkali metal alloys such as aluminum lithium alloys, metal oxides such as magnesium oxide, strontium oxide, aluminum oxide, alkali metal organics such as polymethyl methacrylate polystyrene sodium sulfonate A complex etc. can be mentioned. Moreover, phenanthroline derivatives such as bathocuproin (BCP) and bathophenanthroline (Bpehn), triazole derivatives, oxadiazole derivatives, and aluminum quinolinol complexes such as tris (8-hydroxyquinolinolato) aluminum (Alq3) can be given.

  Especially, it is preferable that the constituent material of an electron injection transport layer is a bipolar material. By using a bipolar material for the electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed. In addition, since it described in the term of the said anode side light emitting layer about the bipolar material, description here is abbreviate | omitted.

The constituent material of the electron injecting and transporting layer and the host material of the central light emitting layer are preferably the same. This is because there is no electron injection barrier from the electron injection transport layer to the central light emitting layer, and the drive voltage can be lowered.
On the other hand, as described above, when the bipolar materials contained in the hole injecting and transporting layer and the electron injecting and transporting layer are the same, the constituent material of the hole injecting and transporting layer and the constituent material of the central light emitting layer are different. The constituent material of the electron injecting and transporting layer and the host material of the central light emitting layer are different.

When the constituent material of the electron injecting and transporting layer is an organic compound (organic compound for electron injecting and transporting layer), the electron injecting and transporting layer is at least at the interface with the cathode, and the reducing compound is added to the organic compound for electron injecting and transporting layer. May have a mixed region. The electron injection transport layer has a region where a reducing dopant is mixed with the organic compound for the electron injection transport layer at least at the interface with the cathode, thereby reducing the electron injection barrier from the cathode to the electron injection transport layer, This is because the driving voltage can be reduced.
In the organic EL device, the electron injection process from the cathode to the organic layer, which is basically an insulator, is reduction of the organic compound on the cathode surface, that is, formation of a radical anion state (Phys. Rev. Lett., 14, 229 (1965)). By previously doping a reducing dopant that reduces the organic compound into the electron injection transport layer in contact with the cathode, the energy barrier for electron injection from the cathode can be lowered. In the electron injecting and transporting layer, an organic compound in a state reduced by a reducing dopant (that is, a state in which electrons are received and electrons are injected) exists, so that an electron injection energy barrier is small, and a conventional organic EL device As a result, the drive voltage can be reduced. Furthermore, a stable metal such as Al that is generally used as a wiring material can be used for the cathode.

  The reducing dopant is not particularly limited as long as it has a property of reducing the organic compound for the electron injecting and transporting layer, but an electron donating compound is usually used.

As the electron donating compound, a metal (metal simple substance), a metal compound, or an organometallic complex is preferably used. Examples of the metal (metal simple substance), the metal compound, or the organometallic complex include those containing at least one metal selected from the group consisting of alkali metals, alkaline earth metals, and transition metals including rare earth metals. it can. Among them, it is preferable that the material contains at least one metal selected from the group consisting of alkali metals, alkaline earth metals, and transition metals including rare earth metals having a work function of 4.2 eV or less. Examples of such a metal (metal simple substance) include Li, Na, K, Cs, Be, Mg, Ca, Sr, Ba, Y, La, Mg, Sm, Gd, Yb, and W. Examples of the metal compound include metal oxides such as Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, and CaO, LiF, NaF, KF, RbF, CsF, and MgF _2. , CaF ₂ , SrF ₂ , BaF ₂ , LiCl, NaCl, KCl, RbCl, CsCl, MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl _{2 and} other metal salts. Examples of the organometallic complex include organometallic compounds containing W, 8-hydroxyquinolinolatolithium (Liq), and the like. Of these, Cs, Li, and Liq are preferably used. This is because good electron injection characteristics can be obtained by doping these into the organic compound for the electron injection transport layer.

  When the electron injecting and transporting layer has a region in which the reducing dopant is mixed with the organic compound for the electron injecting and transporting layer, the electron injecting and transporting layer only needs to have the above region at least at the interface with the cathode. The electron injecting and transporting layer may be uniformly doped with a reducing dopant, and the reducing dopant is doped so that the content of the reducing dopant continuously increases from the anode side to the cathode side. Alternatively, the reducing dopant may be locally doped only in the interface of the electron injecting and transporting layer with the cathode.

  Although the reducing dopant density | concentration in an electron injection transport layer is not specifically limited, It is preferable to set it as about 0.1-99 mass%. This is because if the reducing dopant concentration is less than the above range, the concentration of the organic compound for the electron injecting and transporting layer reduced by the reducing dopant may be too low to obtain a sufficient doping effect. Further, when the reducing dopant concentration exceeds the above range, the reducing dopant concentration in the electron injecting and transporting layer far exceeds the organic compound concentration for the electron injecting and transporting layer, and the organic for the electron injecting and transporting layer reduced by the reducing dopant. This is because, since the concentration of the compound is extremely lowered, a sufficient doping effect may not be obtained in the same manner.

  As a method for forming the electron injecting and transporting layer, for example, a dry method such as a vacuum deposition method or a sputtering method, or a printing method, an ink jet method, a spin coating method, a casting method, a dip coating method, a bar coating method, or a blade coating method. And wet methods such as a roll coating method, a gravure coating method, a flexographic printing method, and a spray coating method.

Among these, as a method for forming an electron injecting and transporting layer doped with a reducing dopant, a method of co-evaporating the organic compound for electron injecting and transporting layer and a reducing dopant is preferably used.
When a thin film can be formed by application from a solution, a spin coating method, a dip coating method, or the like can be used as a method for forming an electron injecting and transporting layer doped with a reducing dopant. In this case, the organic compound for electron injecting and transporting layer and the reducing dopant may be dispersed in an inert polymer.

  Further, as a method of mixing the reducing dopant with the organic compound for the electron injecting and transporting layer so that the content of the reducing dopant continuously increases from the anode side to the cathode side, for example, the above-described electron injecting and transporting can be used. A method of continuously changing the deposition rate of the layer organic compound and the reducing dopant can be used.

  The thickness of the electron injecting and transporting layer is not particularly limited as long as the thickness of the electron injecting and transporting layer is sufficiently exerted.

  The thickness of the electron injecting and transporting layer doped with the reducing dopant is not particularly limited, but is preferably in the range of 0.1 nm to 300 nm, more preferably in the range of 0.5 nm to 200 nm. Is within. If the thickness is less than the above range, the effect of doping may not be sufficiently obtained due to the small amount of the organic compound for the electron injecting and transporting layer reduced by the reducing dopant existing in the vicinity of the cathode interface. is there. Further, if the thickness exceeds the above range, the film thickness of the entire electron injecting and transporting layer is too thick, which may increase the driving voltage.

6). Second Hole Injection / Transport Layer In this embodiment, a second hole injection / transport layer may be formed between the anode and the hole injection / transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the second hole injection transport layer and the hole injection transport layer satisfy the above-described relationship.

  When the second hole injecting and transporting layer is formed between the anode and the hole injecting and transporting layer, the second hole injecting and transporting layer usually functions as the hole injecting and transporting layer, and the hole injecting and transporting layer is positive. Functions as a hole transport layer.

  The constituent material of the second hole injecting and transporting layer is not particularly limited as long as it can stabilize the injection of holes from the anode, and is exemplified as the host material of the anode side light emitting layer. In addition to compounds, arylamines, starburst amines, phthalocyanines, vanadium oxide, molybdenum oxide, ruthenium oxide, aluminum oxide, and other conductive polymers such as amorphous carbon, polyaniline, polythiophene, polyphenylene vinylene, and the like Derivatives of can be used. Conductive polymers such as polyaniline, polythiophene, polyphenylene vinylene, and derivatives thereof may be doped with an acid. Specifically, N, N′-bis (naphthalen-1-yl) -N, N′-bis (phenyl) -benzidine (α-NPD), 4,4,4-tris (3-methylphenylphenylamino) ) Triphenylamine (MTDATA), poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS), polyvinylcarbazole (PVCz), and the like.

  Especially, it is preferable that the constituent material of a 2nd positive hole injection transport layer is a bipolar material. This is because the use of the bipolar material for the second hole injecting and transporting layer can effectively suppress deterioration at the layer interface during driving. In addition, since it described in the term of the said anode side light emitting layer about the bipolar material, description here is abbreviate | omitted.

  When the second hole injecting and transporting layer and the second electron injecting and transporting layer described later contain bipolar materials, the bipolar materials contained in these layers may be the same or different.

When the constituent material of the second hole injecting and transporting layer is an organic material (organic compound for hole injecting and transporting layer), the second hole injecting and transporting layer is at least at the interface with the anode for the hole injecting and transporting layer. It is preferable to have a region where an oxidizing dopant is mixed with an organic compound. The second hole injecting and transporting layer has a region in which the oxidizing dopant is mixed with the organic compound for the hole injecting and transporting layer at least at the interface with the anode, so that the anode to the second hole injecting and transporting layer is provided. This is because the hole injection barrier is reduced and the driving voltage can be lowered.
When the second hole injecting and transporting layer has a region in which the organic compound for hole injecting and transporting layer is mixed with an oxidizing dopant, the hole injecting and transporting layer is oxidized to the organic compound for hole injecting and transporting layer. Since it is the same as the case where it has the area | region where the active dopant was mixed, description here is abbreviate | omitted.

  The film forming method and thickness of the second hole injecting and transporting layer are the same as those of the above-described hole injecting and transporting layer, and thus the description thereof is omitted here.

7). Second Electron Injection / Transport Layer In this embodiment, a second electron injection / transport layer may be formed between the electron injection / transport layer and the cathode. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the electron injection / transport layer and the second electron injection / transport layer satisfy the relationship described above.

  When the second electron injecting and transporting layer is formed between the electron injecting and transporting layer and the cathode, normally, the second electron injecting and transporting layer functions as an electron injecting and transporting layer, and the electron injecting and transporting layer functions as an electron transporting layer. .

  As the constituent material of the second electron injecting and transporting layer, the same material as that of the electron injecting and transporting layer can be used.

  Among them, the constituent material of the second electron injecting and transporting layer is preferably a bipolar material. By using the bipolar material for the second electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed. In addition, since it described in the term of the said anode side light emitting layer about the bipolar material, description here is abbreviate | omitted.

When the constituent material of the second electron injecting and transporting layer is an organic compound (organic compound for electron injecting and transporting layer), the second electron injecting and transporting layer is reduced to the organic compound for electron injecting and transporting layer at least at the interface with the cathode. It is preferable to have a region mixed with a conductive dopant. The second electron injecting and transporting layer has a region in which a reducing dopant is mixed with the organic compound for the electron injecting and transporting layer at least at the interface with the cathode, so that an electron injection barrier from the cathode to the second electron injecting and transporting layer is formed. This is because the driving voltage can be reduced.
In addition, about the case where the 2nd electron injection transport layer has the area | region where the reducing dopant was mixed with the organic compound for electron injection transport layers, the said electron injection transport layer mixed a reducing dopant with the organic compound for electron injection transport layers. Since this is the same as the case of having an area, the description is omitted here.

  Note that the film formation method and thickness of the second electron injecting and transporting layer are the same as those of the above-described electron injecting and transporting layer, and thus the description thereof is omitted here.

8). Third Hole Injection / Transport Layer In this embodiment, a third hole injection / transport layer may be formed between the second hole injection / transport layer and the hole injection / transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the second hole injection transport layer, the third hole injection transport layer, and the hole injection transport layer satisfy the relationship described above.

  When the third hole injection / transport layer is formed between the second hole injection / transport layer and the hole injection / transport layer, the second hole injection / transport layer normally functions as the hole injection layer, The three hole injection transport layer and the hole injection transport layer function as a hole transport layer.

  As a constituent material of the third hole injecting and transporting layer, the same constituent material as that of the second hole injecting and transporting layer can be used.

  Among these, the constituent material of the third hole injection transport layer is preferably a bipolar material. By using the bipolar material for the third hole injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed. In addition, since it described in the term of the said anode side light emitting layer about the bipolar material, description here is abbreviate | omitted.

  When the third hole injecting and transporting layer and the third electron injecting and transporting layer described later contain a bipolar material, the bipolar materials contained in these layers may be the same or different.

  The film formation method and thickness of the third hole injecting and transporting layer are the same as those of the above-described hole injecting and transporting layer, and thus the description thereof is omitted here.

9. Third Electron Injection / Transport Layer In the present embodiment, a third electron injection / transport layer may be formed between the electron injection / transport layer and the second electron injection / transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the electron injection / transport layer, the third electron injection / transport layer, and the second electron injection / transport layer satisfy the relationship described above.

  When the third electron injecting and transporting layer is formed between the electron injecting and transporting layer and the second electron injecting and transporting layer, the second electron injecting and transporting layer normally functions as the electron injecting and transporting layer, and the third electron injecting and transporting layer The electron injecting and transporting layer functions as an electron transporting layer.

  As the constituent material of the third electron injecting and transporting layer, the same material as that of the second electron injecting and transporting layer can be used.

  Among them, the constituent material of the third electron injecting and transporting layer is preferably a bipolar material. By using the bipolar material for the third electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed. In addition, since it described in the term of the said anode side light emitting layer about the bipolar material, description here is abbreviate | omitted.

  Note that the film formation method and thickness of the third electron injecting and transporting layer are the same as those of the above-described electron injecting and transporting layer, and thus the description thereof is omitted here.

10. Second Central Light-Emitting Layer In this embodiment, as illustrated in FIG. 12, a second central light-emitting layer 16a containing a host material and a light-emitting dopant is formed between the anode-side light-emitting layer 5a and the central light-emitting layer 6. It may be. The second central light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

The host material of the second central light emitting layer is preferably the same as the host material of the anode side light emitting layer.
As the host material and light emitting dopant of the second central light emitting layer, the same materials as the host material and light emitting dopant of the anode side light emitting layer described above can be used.

  When the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer contain a host material and a light emitting dopant, the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer have different types of light emitting dopants. It is preferable to contain. By laminating the anode side light emitting layer, the second central light emitting layer and the central light emitting layer in this order, energy transfer between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the second central light emitting layer, and 2 It is possible to suppress energy transfer between the light-emitting dopant in the central light-emitting layer and the light-emitting dopant in the central light-emitting layer, and to emit each light-emitting dopant, thereby improving the light emission efficiency and obtaining a desired light emission color. Because it can.

Among them, it is preferable that one or two layers of the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer contain a fluorescent light emitting dopant, and the other two layers or one layer contain a phosphorescent light emitting dopant. . In the case where the single light-emitting layer includes a fluorescent light-emitting dopant and a phosphorescent light-emitting dopant, energy transfer may occur between the fluorescent light-emitting dopant and the phosphorescent light-emitting dopant. In addition, a fluorescent light emitting dopant is contained in one or two layers of the central light emitting layer, and a phosphorescent light emitting dopant is contained in the other two layers or one layer, thereby transferring energy between the fluorescent light emitting dopant and the phosphorescent light emitting dopant. This is because both the fluorescent emission phosphor and the phosphorescence emission dopant can be made to emit light, and the luminous efficiency can be increased and a desired emission color can be obtained.
Of the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer, when one layer contains a fluorescent light emitting dopant and the other two layers contain a phosphorescent light emitting dopant, the anode side light emitting layer, the second central light emitting layer Either the layer or the central light emitting layer may contain a fluorescent light emitting dopant.
In addition, when two layers of the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer contain a fluorescent light emitting dopant and the other layer contains a phosphorescent light emitting dopant, the anode side light emitting layer, the second light emitting layer, Either the central light emitting layer or the central light emitting layer may contain a phosphorescent light emitting dopant.

  When the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer contain different types of light emitting dopants, the light emitting colors of the different types of light emitting dopants may be the same or different. Especially, it is preferable that the luminescent color of a different kind of light emission dopant differs. It is because a desired luminescent color can be obtained by causing the luminescent dopant in the anode side luminescent layer, the luminescent dopant in the second central luminescent layer, and the luminescent dopant in the central luminescent layer to shine.

  The second central light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant. This is because the light emission efficiency can be improved because the second central light emitting layer has a non-doped region.

As the arrangement of the doped region and the non-doped region, for example, the second central light emitting layer may have a non-doped region on the anode side light emitting layer side, and the second central light emitting layer has a non-doped region on the central light emitting layer side. It may be.
When the second central light emitting layer has a non-doped region on the anode side light emitting layer side, for example, when energy transfer can occur between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the second central light emitting layer, By providing the non-doped region at the interface between the anode side light emitting layer and the second central light emitting layer, the energy transfer is less likely to occur and the light emission efficiency can be improved.
Similarly, when the second central light emitting layer has a non-doped region on the central light emitting layer side, for example, when energy transfer can occur between the light emitting dopant in the second central light emitting layer and the light emitting dopant in the central light emitting layer. Since the non-doped region is provided at the interface between the second central light emitting layer and the central light emitting layer, the energy transfer is less likely to occur and the light emission efficiency can be improved.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant. Among them, it is preferable to appropriately select the arrangement of the doped region and the non-doped region so that the injection balance of holes and electrons can be obtained.

  The number of non-doped regions may be one or more, but is usually one or two. On the other hand, the number of doped regions may be one or more, but is usually one.

  In the present invention, when obtaining white light, it is preferable to contain different types of light emitting dopants in the anode side light emitting layer, the second central light emitting layer, and the central light emitting layer. Among these, it is preferable to use three kinds of light emitting dopants of red, blue, and green.

  When using three kinds of light emitting dopants of red, blue and green, as described above, one or two layers of the anode side light emitting layer, the second central light emitting layer and the central light emitting layer contain a fluorescent light emitting dopant, Since the other two layers or one layer preferably contains a phosphorescent dopant, for example, one layer contains a blue fluorescent dopant, one of the other two layers contains a red phosphorescent dopant, and the other green It is preferable to contain a fluorescent light-emitting dopant, or to make one layer contain a red fluorescent light-emitting dopant, and to make one of the other two layers contain a blue phosphorescent light-emitting dopant and the other contain a green fluorescent light-emitting dopant.

  Note that the thickness and the film forming method of the second central light emitting layer are the same as the thickness and the film forming method of the anode side light emitting layer described above, and thus the description thereof is omitted here.

11. Anode The anode used in the present embodiment may be transparent or opaque, but needs to be a transparent electrode when light is extracted from the anode side.

  For the anode, a conductive material having a large work function is preferably used so that holes can be easily injected. The anode preferably has as low resistance as possible. Generally, a metal material is used, but an organic substance or an inorganic compound may be used. Specific examples include tin oxide, indium tin oxide (ITO), and indium zinc oxide (IZO).

The anode can be formed using a general electrode forming method, and examples thereof include a sputtering method, a vacuum evaporation method, and an ion plating method.
The thickness of the anode is appropriately selected depending on the target resistance value, visible light transmittance, and type of conductive material.

12 Cathode The cathode used in this embodiment may be transparent or opaque, but it needs to be a transparent electrode when light is extracted from the cathode side.

For the cathode, it is preferable to use a conductive material having a small work function so that electrons can be easily injected. Moreover, it is preferable that the cathode has as low resistance as possible. Generally, a metal material is used, but an organic substance or an inorganic compound may be used. Specifically, Al, Cs, Er, etc. as a simple substance, MgAg, AlLi, AlLi, AlMg, CsTe, etc. as an alloy, Ca / Al, Mg / Al, Li / Al, Cs / Al, Cs ₂ O / Al, LiF / Al, include _ErF 3 / Al or the like.

The cathode can be formed using a general electrode forming method, and examples thereof include a sputtering method, a vacuum deposition method, and an ion plating method.
Further, the thickness of the cathode is appropriately selected depending on the target resistance value, visible light transmittance, and type of conductive material.

13. Substrate In the present embodiment, the substrate supports the anode, the hole injection transport layer, the anode side light emitting layer, the central light emitting layer, the electron injection transport layer, the cathode, and the like. When the anode or the cathode has a predetermined strength, the anode or the cathode may serve as the substrate, but the anode or the cathode is usually formed on the substrate having the predetermined strength. In general, when an organic EL element is produced, since the organic EL element can be stably produced by laminating from the anode side, the anode, hole injection transport is usually provided on the substrate. A layer, an anode side light emitting layer, a central light emitting layer, an electron injecting and transporting layer, and a cathode are laminated in this order.

  The substrate may be transparent or opaque, but needs to be a transparent substrate when light is extracted from the substrate side. Examples of the transparent substrate that can be used include glass substrates such as soda lime glass, alkali glass, lead alkali glass, borosilicate glass, aluminosilicate glass, and silica glass, and resin substrates that can be formed into a film.

II. Second Embodiment A second embodiment of the organic EL device of the present invention includes an anode, a hole injecting and transporting layer formed on the anode, a central light emitting layer formed on the hole injecting and transporting layer, A cathode-side light-emitting layer formed on the central light-emitting layer and containing a host material and a light-emitting dopant, an electron-injecting / transporting layer formed on the cathode-side light-emitting layer, and a cathode formed on the electron-injecting / transporting layer The constituent material of the electron injecting and transporting layer and the host material of the cathode side light emitting layer are the same, and the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different. When the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and the constituent material of the central light emitting layer is the ionization potential Ip _2, the electronic When the ionization potential of the constituent material of the incoming transport layer was Ip _3, it is characterized in that it is Ip ₂ ≧ Ip _3.

The organic EL element of this embodiment will be described with reference to the drawings.
FIG. 13 is a schematic cross-sectional view showing an example of the organic EL element of this embodiment. As illustrated in FIG. 13, the organic EL element 1 includes an anode 3, a hole injecting and transporting layer 4, a central light emitting layer 6, a cathode side light emitting layer 5 b, an electron injecting and transporting layer 7, and a cathode 8 on a substrate 2. They are sequentially stacked. The constituent material of the electron injection transport layer 7 and the host material of the cathode side light emitting layer 5b are the same. Further, the host material of the cathode side light emitting layer 5b and the constituent material of the central light emitting layer 6 are different.

FIG. 14 and FIG. 15 are schematic views each showing an example of a band diagram of the organic EL element of this embodiment. In the organic EL device illustrated in FIG. 13, the ionization potential of the hole injection transport layer 4 is Ip ₁ , the ionization potential of the constituent material of the central light emitting layer 6 is Ip ₂ , and the ionization potential of the host material of the cathode side light emitting layer 5b is Ip. ₅ , the ionization potential of the constituent material of the electron injection transport layer 7 is Ip ₃ , the electron affinity of the constituent material of the hole injection transport layer 4 is Ea ₁ , the electron affinity of the constituent material of the central light emitting layer 6 is Ea ₂ , the cathode side The electron affinity of the host material of the light emitting layer 5b is Ea ₅ , and the electron affinity of the constituent material of the electron injection / transport layer 7 is Ea ₃ .

The relationship between the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ , and the relationship of the ionization potential of the constituent material of the central light emitting layer and the electron injection transport layer is Ip ₂ ≧ Ip ₃ .
The host material of the cathode-side light emitting layer and the constituent material of the electron injection / transport layer are the same, so the relationship between the ionization potential of the host material of the cathode-side light emitting layer and the material of the electron injection / transport layer is Ip ₅ = Ip ₃ The relationship between the electron affinity of the host material of the cathode side light emitting layer and the constituent material of the electron injecting and transporting layer is Ea ₅ = Ea ₃ .
The host material is different from the constituent material and the cathode side light emitting layer of the central light-emitting layer, Ea ₂ ≠ Ea ₅ when Ip ₂ = Ip _5, and a Ip ₂ ≠ Ip ₅ when Ea ₂ = Ea _5.
That is, the relationship between the ionization potential of the constituent material of the central light emitting layer, the host material of the cathode side light emitting layer, and the constituent material of the electron injection transport layer is Ip ₂ ≧ Ip ₅ = Ip ₃ and Ip ₂ = Ip ₅ = Ip when ₃ Ea ₂ ≠ Ea ₅ and Ea ₂ ≠ Ea _3, and a Ip ₂ ≠ Ip ₅ and Ip ₂ ≠ Ip ₃ when _{Ea 2 = Ea 5 = Ea 3} .

In this embodiment, the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, and the relationship between the electron affinity of the constituent material of the hole injection transport layer and the constituent material of the central light emitting layer is Ea ₁ ≧ is Ea _2, by the relationship of the ionization potential of a constituent material of the constituent material and the electron injection transport layer of the central light-emitting layer is Ip ₂ ≧ Ip _3, although penetration of holes and electrons to the counter electrode occurs, an anode and Since holes and electrons are smoothly transported between the cathodes, there is no charge accumulation at the interface between the hole injection transport layer and the central light emitting layer and the interface between the cathode side light emitting layer and the electron injection transport layer during driving. It is possible to suppress deterioration at the interface of the layers. Accordingly, it is possible to obtain a remarkably stable lifetime characteristic and to reduce the color change.

  In this embodiment, the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, so that the interface between the central light emitting layer and the cathode side light emitting layer is the interface between the hole injection transport layer and the central light emitting layer. As compared with the interface between the cathode-side light-emitting layer and the electron-injecting and transporting layer, charges are more easily accumulated, and light can be emitted intensively at the interface between the central and light-emitting layers. In addition, since holes and electrons are transported smoothly, holes and electrons are recombined throughout the light emitting layer, so that the recombination efficiency of holes and electrons is not significantly reduced. Therefore, high efficiency can be achieved.

  Furthermore, in this embodiment, since the constituent material of the electron injecting and transporting layer and the host material of the cathode side light emitting layer are the same, there is no electron injection barrier from the electron injecting and transporting layer to the cathode side light emitting layer, and the driving voltage is reduced. It is possible to make it.

  The anode, the cathode, the substrate, the third hole injecting and transporting layer, and the third electron injecting and transporting layer are the same as those described in the first embodiment, and the description thereof is omitted here. Hereinafter, the other structure in the organic EL element of this embodiment is demonstrated.

1. In this embodiment, when the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ When the ionization potential of the constituent material of the central light emitting layer is Ip ₂ and the ionization potential of the constituent material of the electron injection transport layer is Ip ₃ , Ip ₂ ≧ Ip ₃ .

Regarding the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer, the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ , and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ Ea ₁ ≧ Ea ₂ is sufficient. In addition, the relationship between the ionization potentials of the constituent materials of the hole injection transport layer and the central light emitting layer is as follows: the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , and the ionization potential of the constituent material of the central light emitting layer is Ip ₂ . In general, Ip ₁ ≦ Ip ₂ is satisfied.

In particular, since the central light emitting layer contains a host material and a light emitting dopant, and the constituent material of the hole injecting and transporting layer and the host material of the central light emitting layer are preferably the same, the central light emitting layer and the hole injecting and transporting layer are preferred. The relationship between the ionization potential and the electron affinity of the constituent material is preferably Ip ₁ = Ip ₂ and Ea ₁ = Ea ₂ as illustrated in FIG. This is because there is no hole injection barrier from the hole injection transport layer to the central light emitting layer, and the driving voltage can be lowered.

On the other hand, the relationship between the ionization potential and the electron affinity of the constituent materials of the hole injecting and transporting layer and the central light emitting layer is preferably Ip ₁ <Ip ₂ and Ea ₁ > Ea ₂ as illustrated in FIG. This is because if Ip ₁ <Ip ₂ and Ea ₁ > Ea ₂ , the band gap energy of the constituent material of the central light emitting layer can be made relatively large. For example, when the central light-emitting layer contains a host material and a light-emitting dopant, the host material and the light-emitting dopant have an ionization potential and an electron affinity that satisfy a predetermined relationship in order to improve luminous efficiency. It becomes easy to select the material and the luminescent dopant. In addition, since Ip ₁ <Ip ₂ , the presence of some energy barrier in the hole transport from the hole injection transport layer to the central light emitting layer can control the hole injection and increase the luminous efficiency. Because it can.

In the case of Ip ₁ <Ip ₂ , the difference between Ip ₁ and Ip ₂ varies depending on the constituent materials of the hole injection transport layer and the central light emitting layer, but specifically 0.1 eV or more Is preferable, and more preferably 0.2 eV or more. Even when the difference between Ip ₁ and Ip ₂ is relatively large, holes can be transported from the hole injecting and transporting layer to the central light emitting layer if the driving voltage is relatively high.

When Ea ₁ > Ea ₂ , the difference between Ea ₁ and Ea ₂ varies depending on the constituent materials of the hole injecting and transporting layer and the central light emitting layer, but specifically 0.1 eV or more. Is preferable, and more preferably 0.2 eV or more and 0.5 eV or less.

The relationship between the ionization potential of the constituent material of the central light-emitting layer and the electron injecting and transporting layer, when Ip ₂ and an ionization potential of a constituent material of the central light-emitting layer, the ionization potential of the constituent material of the electron injection transport layer was Ip _3, Ip ₂ ≧ Ip ₃ is sufficient. In this embodiment, since the host material of the cathode side light emitting layer and the constituent material of the electron injection transport layer are the same, the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different. The ionization potential between the host material of the cathode-side light emitting layer and the constituent material of the electron injection / transport layer is expressed as follows: the ionization potential of the constituent material of the central light-emitting layer is Ip ₂ and the ionization potential of the host material of the cathode-side light-emitting layer is Ip ₅ When the ionization potential of the constituent material of the electron injecting and transporting layer is Ip ₃ , Ip ₂ ≧ Ip ₅ = Ip ₃ . In this case, since the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, when Ip ₂ = Ip ₅ = Ip ₃ , Ea ₂ ≠ Ea ₅ and Ea ₂ ≠ Ea ₃ , and Ea ₂ = Ea ₅ When Ea ₃ , Ip ₂ ≠ Ip ₅ and Ip ₂ ≠ Ip ₃ .
Among them, it is preferable that Ip ₂ > Ip ₅ = Ip ₃ . This is because if Ip ₂ > Ip ₅ = Ip ₃ and Ea ₂ <Ea ₅ = Ea ₃ , the band gap energy of the constituent material of the central light emitting layer can be made relatively large. For example, when the central light-emitting layer contains a host material and a light-emitting dopant, the host material and the light-emitting dopant have an ionization potential and an electron affinity that satisfy a predetermined relationship in order to improve luminous efficiency. It becomes easy to select the material and the luminescent dopant.

When Ip ₂ > Ip ₅ = Ip ₃ , the difference between Ip ₂ and Ip ₅ and Ip ₃ depends on the constituent material of the central light emitting layer, the host material of the cathode side light emitting layer, and the constituent material of the electron injection and transport layer Specifically, it is preferably 0.1 eV or more, more preferably 0.2 eV or more.

The relationship between the electron affinity of the constituent material of the central light emitting layer and the electron injecting and transporting layer is as follows: when the electron affinity of the constituent material of the central light emitting layer is Ea ₂ and the electron affinity of the constituent material of the electron injecting and transporting layer is Ea ₃ , Is Ea ₂ ≦ Ea ₃ . In the present embodiment, as described above, the host material of the cathode side light emitting layer and the constituent material of the electron injecting and transporting layer are the same, and the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different. the relationship between the electron affinity of the constituent material of the material of the light-emitting layer on the cathode side light emitting layer host material and the electron injecting and transporting layer, the electron affinity of the constituent material of the central light-emitting layer Ea _2, the host material for the cathode-side emission layer When the electron affinity is Ea ₅ and the electron affinity of the constituent material of the electron injecting and transporting layer is Ea ₃ , Ea ₂ ≦ Ea ₅ = Ea ₃ is satisfied. In this case, since the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, as described above, when Ip ₂ = Ip ₅ = Ip ₃ , Ea ₂ ≠ Ea ₅ and Ea ₂ ≠ Ea ₃ , and When Ea ₂ = Ea ₅ = Ea ₃ , Ip ₂ ≠ Ip ₅ and Ip ₂ ≠ Ip ₃ .
Among these, it is preferable that Ea ₂ <Ea ₅ = Ea ₃ . This is because the presence of some energy barrier in electron transport from the cathode side light emitting layer to the central light emitting layer can control the injection of electrons and increase the light emission efficiency.

When Ea ₂ <Ea ₅ = Ea ₃ , the difference between Ea ₂ and Ea ₅ and Ea ₃ depends on the constituent material of the central light emitting layer, the host material of the cathode side light emitting layer, and the constituent material of the electron injection and transport layer Specifically, it is preferably 0.1 eV or more, more preferably 0.2 eV or more. Even when the difference between Ea ₂ and Ea ₅ is relatively large, electrons can be transported from the cathode side light emitting layer to the central light emitting layer if the driving voltage is relatively high.

The relationship between the ionization potential and the electron affinity of the constituent materials of the hole injection transport layer and the electron injection transport layer is not particularly limited.
In particular, since the hole injection transport layer and the electron injection transport layer preferably contain the same bipolar material, the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , and the ionization potential of the constituent material of the electron injection transport layer is Assuming that the potential is Ip ₃ , the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ , and the electron affinity of the constituent material of the electron injecting and transporting layer is Ea ₃ , as illustrated in FIG. 14, Ip ₁ = Ip ₃ and Ea ₁ = Ea ₃ are preferred.
On the other hand, the constituent material of the hole injecting and transporting layer and the host material of the central light emitting layer are the same, and the relationship between the ionization potential and the electron affinity of the constituent materials of the hole injecting and transporting layer and the central light emitting layer as illustrated in FIG. When Ip ₁ = Ip ₂ and Ea ₁ = Ea ₂ , the constituent materials of the central light emitting layer and the electron injecting and transporting layer are different. relation of the ionization potential and electron affinity of the constituent material of the hole injection transport layer and the electron injecting and transporting layer becomes _{Ea 1 ≠ Ea 3, Ea 1} = Ip 1 ≠ Ip 3 when Ea ₃ when Ip ₁ = Ip _3.

  In the present embodiment, as illustrated in FIG. 16, a second hole injection / transport layer 9 may be formed between the anode 3 and the hole injection / transport layer 4. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the second hole injecting and transporting layer and the hole injecting and transporting layer is the same as that in the first embodiment, and a description thereof will be omitted here.

  In the present embodiment, as illustrated in FIG. 16, the second electron injection / transport layer 10 may be formed between the electron injection / transport layer 7 and the cathode 8. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer is the same as that in the first embodiment, and a description thereof will be omitted here.

  In the present embodiment, as illustrated in FIG. 17, a third hole injection transport layer 11 may be formed between the second hole injection transport layer 9 and the hole injection transport layer 4. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the second hole injecting and transporting layer, the third hole injecting and transporting layer, and the hole injecting and transporting layer is the same as that in the first embodiment. The description in is omitted.

  In the present embodiment, as illustrated in FIG. 17, a third electron injection / transport layer 12 may be formed between the electron injection / transport layer 7 and the second electron injection / transport layer 10. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the electron injecting and transporting layer, the third electron injecting and transporting layer, and the electron affinity is the same as that in the first embodiment. Is omitted.

  In addition, the measuring method of the ionization potential and electron affinity of the constituent material of each layer is as having described in the said 1st embodiment.

2. Cathode side light emitting layer The cathode side light emitting layer in this embodiment contains a host material and a light emitting dopant, and is formed between the central light emitting layer and the electron injecting and transporting layer. The constituent material of the electron injecting and transporting layer is the same, and the host material of the cathode side light emitting layer and the constituent material of the central light emitting layer are different. The cathode side light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

  The host material for the cathode-side light emitting layer may be the same as the constituent material for the electron injecting and transporting layer, and examples thereof include a dye material, a metal complex material, and a polymer material. In addition, since it described in the said 1st embodiment about the pigment | dye type | system | group material, a metal complex type | system | group material, and a polymeric material, description here is abbreviate | omitted.

In the present embodiment, the host material of the cathode side light emitting layer is preferably a bipolar material. This is because the use of the bipolar material for the cathode-side light emitting layer can effectively suppress deterioration at the interface of each layer during driving.
The bipolar material has been described in detail in the section of the anode side light emitting layer of the first embodiment, and the description thereof is omitted here.

  The relationship between the electron affinity and ionization potential of the light emitting dopant, the host material and the light emitting dopant, the light emitting dopant concentration in the cathode side light emitting layer, and the case where the cathode side light emitting layer contains two or more kinds of light emitting dopants are as described above. Since it is the same as that of what was described in the term of the anode side light emitting layer of the 1st embodiment, explanation here is omitted.

  The cathode-side light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant.

  In the example shown in FIG. 18A, the cathode-side light-emitting layer 5b has a doped region 21 and a non-doped region 22, and the non-doped region 22 is disposed on the central light-emitting layer 6 side. For example, when energy transfer can occur between the light emitting dopant in the cathode side light emitting layer and the light emitting dopant in the center light emitting layer, by providing a non-doped region at the interface between the cathode side light emitting layer and the central light emitting layer, The energy transfer is less likely to occur and the light emission efficiency can be improved. Specifically, the cathode side light emitting layer and the central light emitting layer contain light emitting dopants that emit different colors, and when each light emitting dopant emits light to obtain white light, the cathode side light emitting layer and the center light emitting layer It is preferable that a non-doped region is provided at the interface of the light emitting layer. In addition, when one of the cathode-side light emitting layer and the central light-emitting layer contains a fluorescent light-emitting dopant and the other contains a phosphorescent light-emitting dopant, It is preferable that a non-doped region is provided at the interface of the light emitting layer.

  In the example shown in FIG. 18B, the cathode side light emitting layer 5b has two doped regions 21a and 21b and one non-doped region 22, and a non-doped region between the two doped regions 21a and 21b. 22 is arranged. For example, in the case where energy transfer can occur between the light-emitting dopant in the doped region 21a and the light-emitting dopant in the doped region 21b, the non-doped region 22 is disposed between the two doped regions 21a and 21b, so that the above energy is obtained. It is difficult to cause movement and light emission efficiency can be improved. Specifically, when the two doped regions contain light emitting dopants that emit different colors, and each light emitting dopant emits light to obtain white light, a non-doped region between the two doped regions. Is preferably arranged. In addition, when one of the two doped regions contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant, and each of the light emitting dopants emits light, the non-doped region is located between the two doped regions. Is preferably arranged.

  Thus, luminous efficiency can be improved because the cathode side light emitting layer has a non-doped region.

  The arrangement of the doped region and the non-doped region is not particularly limited as long as the cathode side light emitting layer has an arrangement of one or more doped regions and one or more non-doped regions. For example, the cathode side light emitting layer 5b may have a non-doped region 22 on the central light emitting layer 6 side as shown in FIG. 18A, and the cathode side light emitting layer 5b has 2 as shown in FIG. You may have the non-dope area | region 22 pinched | interposed into the some dope area | regions 21a and 21b. Although not shown, the cathode side light emitting layer may have two doped regions and two non-doped regions, and the doped regions and the non-doped regions may be alternately arranged.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant.

  Since the other points of the doped region and the non-doped region are the same as those described in the section of the anode side light emitting layer, description thereof is omitted here.

  Further, the thickness of the cathode-side light emitting layer and the film forming method are the same as the thickness of the anode-side light emitting layer and the film forming method in the first embodiment, and the description thereof is omitted here.

3. Central light-emitting layer The central light-emitting layer in this embodiment is formed between the hole injection transport layer and the cathode-side light-emitting layer, and the constituent material of the central light-emitting layer and the host material of the cathode-side light-emitting layer are different. The constituent material of the light emitting layer and the constituent material of the electron injecting and transporting layer are also different. The central light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

The constituent material of the central light emitting layer may be different from the constituent material of the host material of the cathode side light emitting layer and the electron injecting and transporting layer.
When the central light emitting layer contains a host material and a light emitting dopant, it is preferable that the host material of the central light emitting layer and the constituent material of the hole injecting and transporting layer are the same. This is because there is no electron injection barrier from the hole injecting and transporting layer to the central light emitting layer, and the driving voltage can be lowered.
On the other hand, as will be described later, when the constituent material of the hole injecting and transporting layer and the constituent material of the electron injecting and transporting layer are the same, the constituent material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are different. Therefore, the host material of the central light emitting layer and the constituent material of the hole injecting and transporting layer are different.
In addition, since it is the same as that of the said 1st embodiment about the other point of the constituent material of a center light emitting layer, description here is abbreviate | omitted.

  In the case where the central light emitting layer contains a host material and a light emitting dopant, the relationship between the electron affinity and ionization potential of the host material and the light emitting dopant, the light emitting dopant concentration in the central light emitting layer, and the central light emitting layer having two or more types Since the case of containing a light emitting dopant is the same as that described in the section of the anode side light emitting layer of the first embodiment, description thereof is omitted here.

  When the central light emitting layer contains a host material and a light emitting dopant, the central light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant.

  In the example shown in FIG. 19A, the central light emitting layer 6 has a doped region 21 and a non-doped region 22, and the non-doped region 22 is arranged on the cathode side light emitting layer 5b side. For example, when energy transfer can occur between the light emitting dopant in the cathode side light emitting layer and the light emitting dopant in the center light emitting layer, by providing a non-doped region at the interface between the cathode side light emitting layer and the central light emitting layer, The energy transfer is less likely to occur and the light emission efficiency can be improved.

  In the example shown in FIG. 19B, the central light emitting layer 6 has a doped region 21 and a non-doped region 22, and the non-doped region 22 is arranged on the hole injection transport layer 4 side. For example, when energy transfer can occur from the light emitting dopant in the central light emitting layer 6 to the constituent material of the hole injecting and transporting layer 4, the central light emitting layer 6 has the non-doped region 22 on the hole injecting and transporting layer 4 side. Energy transfer is unlikely to occur and the light emission efficiency can be improved.

  In the example shown in FIG. 19C, the central light emitting layer 6 has two doped regions 21a and 21b and one non-doped region 22, and the non-doped region 22 is provided between the two doped regions 21a and 21b. Is arranged. For example, in the case where energy transfer can occur between the light-emitting dopant in the doped region 21a and the light-emitting dopant in the doped region 21b, the non-doped region 22 is disposed between the two doped regions 21a and 21b, so that the above energy is obtained. It is difficult to cause movement and light emission efficiency can be improved.

  Thus, luminous efficiency can be improved because the central light emitting layer has a non-doped region.

  The arrangement of the doped region and the non-doped region is not particularly limited as long as the central light emitting layer has one or more doped regions and one or more non-doped regions. For example, the central light emitting layer 6 may have a non-doped region 22 on the cathode side light emitting layer 5b side as shown in FIG. 19A, and the central light emitting layer 6 has holes as shown in FIG. A non-doped region 22 may be provided on the injection transport layer 4 side, and the central light emitting layer 6 has a non-doped region 22 sandwiched between two doped regions 21a and 21b as shown in FIG. May be. Although not shown, the central light emitting layer may have two doped regions and three non-doped regions, and the doped regions and the non-doped regions may be alternately arranged.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant. Among them, it is preferable to appropriately select the arrangement of the doped region and the non-doped region so that the injection balance of holes and electrons can be obtained.

In the organic EL device illustrated in FIG. 19B, since the central light emitting layer 6 has the non-doped region 22 on the hole injecting and transporting layer 4 side, the light emitting dopant is positive at the interface between the hole injecting and transporting layer and the central light emitting layer. The hole injection from the hole injecting and transporting layer to the central light emitting layer can be improved without hindering the hole injection.
Here, in this embodiment, the relationship between the electron affinity of the constituent materials of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ , and the electrons injected into the central light emitting layer are prevented from penetrating to the counter electrode. Since no blocking layer is provided, it is difficult to balance the holes and electrons injected into the light emitting layer in the same manner as an organic EL device having a conventional blocking layer.
On the other hand, in the organic EL device illustrated in FIG. 19B, the central light emitting layer has a non-doped region on the hole injecting and transporting layer side, whereby charge trapping by the light emitting dopant can be controlled. A highly efficient element can be obtained. For example, when the luminescent dopant is more likely to transport electrons than holes, the electron injection tends to be excessive. In this case, since the central light emitting layer has a non-doped region on the hole injecting and transporting layer side, the light emission efficiency can be improved. This is because a non-doped region is provided on the hole-injecting and transporting layer side (anode side) of the central light-emitting layer, and a doped region is provided on the cathode light-emitting layer side (cathode side) of the central light-emitting layer. It is thought that this is because the generated electrons are trapped by the light emitting dopant more in the central light emitting layer, and are trapped by the light emitting dopant more at the cathode side, and do not penetrate to the anode. That is, when the central light emitting layer has a non-doped region on the hole injecting and transporting layer side, it is useful when electron injection is excessive.

  The remaining points of the doped region and the non-doped region are the same as in the first embodiment.

  When the central light emitting layer also contains a host material and a light emitting dopant, the cathode side light emitting layer and the central light emitting layer preferably contain different types of light emitting dopants. By laminating the cathode side light emitting layer and the central light emitting layer, the energy transfer between the light emitting dopant in the cathode side light emitting layer and the light emitting dopant in the central light emitting layer is suppressed, and the light emitting dopant and center in the cathode side light emitting layer are suppressed. This is because both of the light-emitting dopant in the light-emitting layer can be illuminated, so that the luminous efficiency can be increased and a desired emission color can be obtained.

  The case where the cathode side light emitting layer and the central light emitting layer contain different types of light emitting dopants is the same as the case where the anode side light emitting layer and the central light emitting layer contain different types of light emitting dopants in the first embodiment. Since there is, explanation here is omitted.

  Further, since the thickness of the central light emitting layer and the film forming method are the same as those in the first embodiment, description thereof is omitted here.

4). Hole Injecting and Transporting Layer The hole injecting and transporting layer used in this embodiment is formed between the anode and the central light emitting layer. The hole injection transport layer has a function of stably injecting or transporting holes from the anode to the central light emitting layer.

  The hole injection transport layer may be either a hole injection layer having a hole injection function and a hole transport layer having a hole transport function, or may be a hole injection function and a hole transport. It may be a single layer having both functions.

  The constituent material of the hole injecting and transporting layer is not particularly limited as long as it is a material that can stably transport holes injected from the anode to the central light emitting layer, and is not limited to the second material in the first embodiment. The same constituent materials as the hole injecting and transporting layer can be used.

  Among these, the constituent material of the hole injecting and transporting layer is preferably a bipolar material. This is because the use of the bipolar material for the hole injecting and transporting layer can effectively suppress deterioration at the layer interface during driving. Since the bipolar material has been described in the first embodiment, description thereof is omitted here.

When the hole injecting and transporting layer and the later-described electron injecting and transporting layer contain bipolar materials, the bipolar materials contained in these layers may be the same or different.
Especially, it is preferable that the bipolar material contained in a positive hole injection transport layer and an electron injection transport layer is the same. This is because, if these bipolar materials are the same, even if holes penetrate into the electron injecting and transporting layer and electrons penetrate into the hole injecting and transporting layer, these layers are not easily deteriorated. Moreover, when forming these layers by a vacuum evaporation method etc., a common vapor deposition source can be used and it is advantageous on a manufacturing process.

On the other hand, it is also preferable that the constituent material of the hole injection transport layer and the host material of the central light emitting layer are the same. This is because there is no hole injection barrier from the hole injection transport layer to the central light emitting layer, and the driving voltage can be lowered.
In addition, when the bipolar materials contained in the hole injecting and transporting layer and the electron injecting and transporting layer are the same, the constituent material of the electron injecting and transporting layer is different from the constituent material of the central light emitting layer. And the host material of the central light emitting layer are different.

  Note that the region where the oxidizing dopant is mixed, the film formation method and the thickness of the hole injecting and transporting layer are the same as those described in the first embodiment, and a description thereof is omitted here.

5). Electron Injecting and Transporting Layer The electron injecting and transporting layer used in this embodiment is formed between the cathode and the central light emitting layer, and the constituent material of the electron injecting and transporting layer and the host material of the cathode side light emitting layer are the same. The constituent material of the electron injecting and transporting layer and the constituent material of the central light emitting layer are different. The electron injection / transport layer has a function of stably injecting or transporting electrons from the cathode to the cathode-side light emitting layer.

  The electron injection / transport layer may be one of an electron injection layer having an electron injection function and an electron transport layer having an electron transport function, or a single unit having both an electron injection function and an electron transport function. It may be a single layer.

  The constituent material of the electron injecting and transporting layer is not particularly limited as long as it is a material that can stably transport electrons injected from the cathode to the central light emitting layer, and is exemplified as the host material of the cathode side light emitting layer. The compound can be used.

  Especially, it is preferable that the constituent material of an electron injection transport layer is a bipolar material. By using a bipolar material for the electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed. Since the bipolar material is described in the section of the anode side light emitting layer in the first embodiment, description thereof is omitted here.

  Note that the region where the reducing dopant is mixed and the film formation method and thickness of the electron injecting and transporting layer are the same as those described in the first embodiment, and thus the description thereof is omitted here.

6). Second Hole Injection / Transport Layer In this embodiment, a second hole injection / transport layer may be formed between the anode and the hole injection / transport layer. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the second hole injection transport layer and the hole injection transport layer satisfy the above-described relationship.

  When the second hole injecting and transporting layer is formed between the anode and the hole injecting and transporting layer, the second hole injecting and transporting layer usually functions as the hole injecting and transporting layer, and the hole injecting and transporting layer is positive. Functions as a hole transport layer.

  As the constituent material of the second hole injecting and transporting layer, the same material as the constituent material of the hole injecting and transporting layer can be used.

  Especially, it is preferable that the constituent material of a 2nd positive hole injection transport layer is a bipolar material. This is because the use of the bipolar material for the second hole injecting and transporting layer can effectively suppress deterioration at the layer interface during driving. Since the bipolar material has been described in the first embodiment, description thereof is omitted here.

  When the second hole injecting and transporting layer and the second electron injecting and transporting layer described later contain bipolar materials, the bipolar materials contained in these layers may be the same or different.

  Note that the region where the oxidizing dopant is mixed, the film formation method and the thickness of the second hole injecting and transporting layer are the same as those described in the first embodiment, and the description thereof is omitted here.

7). Second Electron Injection / Transport Layer In this embodiment, a second electron injection / transport layer may be formed between the electron injection / transport layer and the cathode. In this case, it is preferable that the ionization potential and the electron affinity of the constituent materials of the electron injection / transport layer and the second electron injection / transport layer satisfy the relationship described above.

  When the second electron injecting and transporting layer is formed between the electron injecting and transporting layer and the cathode, normally, the second electron injecting and transporting layer functions as an electron injecting and transporting layer, and the electron injecting and transporting layer functions as an electron transporting layer. .

  The constituent material of the second electron injecting and transporting layer is not particularly limited as long as it is a material capable of stably transporting electrons injected from the cathode to the central light emitting layer. The same material as the constituent material of the transport layer can be used.

  Among them, the constituent material of the second electron injecting and transporting layer is preferably a bipolar material. By using the bipolar material for the second electron injecting and transporting layer, deterioration at the layer interface during driving can be effectively suppressed. Since the bipolar material is described in the section of the anode side light emitting layer in the first embodiment, description thereof is omitted here.

  Note that the region where the reducing dopant is mixed and the film formation method and thickness of the second electron injecting and transporting layer are the same as those described in the first embodiment, and thus the description thereof is omitted here.

8). Third Central Light-Emitting Layer In this embodiment, as illustrated in FIG. 20, a third central light-emitting layer 16b containing a host material and a light-emitting dopant is formed between the central light-emitting layer 6 and the cathode-side light-emitting layer 5b. It may be. The third central light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

The host material of the third central light emitting layer is preferably the same as the host material of the cathode side light emitting layer.
As the host material and light emitting dopant of the third central light emitting layer, the same host materials and light emitting dopant as those of the cathode side light emitting layer described above can be used.

  When the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer contain a host material and a light emitting dopant, the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer have different types of light emitting dopants. It is preferable to contain. By laminating the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer in order, the energy transfer between the light emitting dopant in the central light emitting layer and the light emitting dopant in the third central light emitting layer, and the third The energy transfer between the light emitting dopant in the central light emitting layer and the light emitting dopant in the cathode side light emitting layer can be suppressed, each light emitting dopant can be made to emit light, and the light emitting efficiency can be increased and a desired light emitting color can be obtained. Because it can.

Among them, it is preferable that one or two layers of the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer contain a fluorescent light emitting dopant and the other two layers or one layer contain a phosphorescent light emitting dopant. . In the case where a fluorescent emitting phosphor and a phosphorescent emitting dopant are included in a single emitting layer, energy transfer may occur between the fluorescent emitting dopant and the phosphorescent emitting dopant, but the central emitting layer, the third central emitting layer, Energy transfer between the fluorescent light emitting dopant and the phosphorescent light emitting dopant by including a fluorescent light emitting dopant in one or two layers of the cathode side light emitting layer and adding a phosphorescent light emitting dopant to the other two layers or one layer. This is because both the fluorescent emission phosphor and the phosphorescence emission dopant can be made to emit light, and the emission efficiency can be increased and a desired emission color can be obtained.
Of the central light emitting layer, the third central light emitting layer and the cathode side light emitting layer, when one layer contains a fluorescent light emitting dopant and the other two layers contain a phosphorescent light emitting dopant, the central light emitting layer and the third central light emitting layer Either of the light emitting layer and the cathode side light emitting layer may contain a fluorescent light emitting dopant.
Further, when two of the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer contain a fluorescent light emitting dopant and the other layer contains a phosphorescent light emitting dopant, the central light emitting layer, the third central light emitting layer, Either the light emitting layer or the cathode side light emitting layer may contain a phosphorescent light emitting dopant.

  When the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer contain different types of light emitting dopants, the light emission colors of the different types of light emitting dopants may be the same or different. Especially, it is preferable that the luminescent color of a different kind of light emission dopant differs. It is because a desired luminescent color can be obtained by causing the luminescent dopant in the central luminescent layer, the luminescent dopant in the third central luminescent layer, and the luminescent dopant in the cathode side luminescent layer to shine.

  The third central light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant. This is because the light emission efficiency can be improved because the second central light emitting layer has a non-doped region.

As the arrangement of the doped region and the non-doped region, for example, the third central light emitting layer may have a non-doped region on the central light emitting layer side, and the third central light emitting layer has a non-doped region on the cathode side light emitting layer side. It may be.
When the third central light emitting layer has a non-doped region on the central light emitting layer side, for example, when energy transfer can occur between the light emitting dopant in the central light emitting layer and the light emitting dopant in the third central light emitting layer, the central light emission By providing the non-doped region at the interface between the layer and the third central light emitting layer, the energy transfer is less likely to occur and the light emission efficiency can be improved.
Similarly, when the third central light emitting layer has a non-doped region on the cathode side light emitting layer side, for example, energy transfer can occur between the light emitting dopant in the third central light emitting layer and the light emitting dopant in the cathode side light emitting layer. Since the non-doped region is provided at the interface between the third central light emitting layer and the cathode side light emitting layer, the energy transfer is less likely to occur and the light emission efficiency can be improved.

  The arrangement of the doped region and the non-doped region is appropriately selected in consideration of the energy transition of the luminescent dopant. Among them, it is preferable to appropriately select the arrangement of the doped region and the non-doped region so that the injection balance of holes and electrons can be obtained.

  The number of non-doped regions may be one or more, but is usually one or two. On the other hand, the number of doped regions may be one or more, but is usually one.

  In the present invention, when white light is obtained, it is preferable to contain different types of light emitting dopants in the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer. Among these, it is preferable to use three kinds of light emitting dopants of red, blue, and green.

  When using three types of light emitting dopants of red, blue, and green, as described above, one or two layers of the central light emitting layer, the third central light emitting layer, and the cathode side light emitting layer contain a fluorescent light emitting dopant, Since the other two layers or one layer preferably contains a phosphorescent dopant, for example, one layer contains a blue fluorescent dopant, one of the other two layers contains a red phosphorescent dopant, and the other green It is preferable to contain a fluorescent light-emitting dopant, or to make one layer contain a red fluorescent light-emitting dopant, and to make one of the other two layers contain a blue phosphorescent light-emitting dopant and the other contain a green fluorescent light-emitting dopant.

  The thickness and the film forming method of the third central light emitting layer are the same as the thickness and the film forming method of the cathode side light emitting layer described above, and thus the description thereof is omitted here.

III. Third Embodiment A third embodiment of the organic EL device of the present invention includes an anode, a hole injection transport layer formed on the anode, a host material and a light emitting dopant formed on the hole injection transport layer. An anode-side light-emitting layer containing the cathode, a central light-emitting layer formed on the anode-side light-emitting layer, a cathode-side light-emitting layer formed on the central light-emitting layer and containing a host material and a light-emitting dopant, and the cathode side An organic EL device having an electron injecting and transporting layer formed on a light emitting layer and a cathode formed on the electron injecting and transporting layer, comprising the constituent material of the hole injecting and transporting layer and the anode side light emitting layer The host material is the same, the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, the constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different, and the central material Of the light emitting layer When the constituent material and the host material of the cathode side light emitting layer are different, the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ , and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and Ip ₂ ≧ Ip ₃ when the ionization potential of the constituent material of the central light emitting layer is Ip ₂ and the ionization potential of the constituent material of the electron injection / transport layer is Ip ₃ It is.

The organic EL element of this embodiment will be described with reference to the drawings.
FIG. 21 is a schematic cross-sectional view showing an example of the organic EL element of this embodiment. As illustrated in FIG. 21, the organic EL element 1 includes an anode 3, a hole injection transport layer 4, an anode side light emitting layer 5 a, a central light emitting layer 6, a cathode side light emitting layer 5 b, and an electron injection transport layer on a substrate 2. 7 and the cathode 8 are sequentially laminated. The constituent material of the hole injection transport layer 4 and the host material of the anode side light emitting layer 5a are the same, and the constituent material of the electron injection transport layer 7 and the host material of the cathode side light emitting layer 5b are also the same. Further, the host material of the anode side light emitting layer 5a and the constituent material of the central light emitting layer 6 are different, and the host material of the cathode side light emitting layer 5b and the constituent material of the central light emitting layer 6 are also different.

FIG. 22 is a schematic diagram showing an example of a band diagram of the organic EL element of this embodiment. In the organic EL device illustrated in FIG. 21, the ionization potential of the hole injection transport layer 4 is Ip ₁ , the ionization potential of the host material of the anode side light emitting layer 5a is Ip ₄ , and the ionization potential of the constituent material of the central light emitting layer 6 is Ip. ₂ , the ionization potential of the host material of the cathode side light emitting layer 5 b is Ip ₅ , the ionization potential of the constituent material of the electron injection transport layer 7 is Ip ₃ , the electron affinity of the constituent material of the hole injection transport layer 4 is Ea ₁ , the anode The electron affinity of the host material of the side light emitting layer 5a is Ea ₄ , the electron affinity of the constituent material of the central light emitting layer 6 is Ea ₂ , the electron affinity of the host material of the cathode side light emitting layer 5b is Ea ₅ , and the structure of the electron injection / transport layer 7 The electron affinity of the material is Ea ₃ .

The relationship between the electron affinity of the constituent material of the hole injection transport layer and the central light emitting layer is Ea ₁ ≧ Ea ₂ , and the relationship of the ionization potential of the constituent material of the central light emitting layer and the electron injection transport layer is Ip ₂ ≧ Ip ₃ .

Since the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer are the same, the relationship between the ionizing potential of the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer is Ip ₁ = Ip ₄ And the relationship between the electron affinity of the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer is Ea ₁ = Ea ₄ .
The host material of the cathode side light emitting layer and the constituent material of the electron injecting and transporting layer are the same, so the relationship between the ionization potential of the host material of the cathode side light emitting layer and the constituent material of the electron injecting and transporting layer is Ip ₅ = Ip ₃ The relationship between the electron affinity of the constituent material of the hole injecting and transporting layer and the host material of the anode side light emitting layer is Ea ₅ = Ea ₃ .

Construction material of the host material and the central light-emitting layer on the anode side light emitting layer from different, Ea ₄ ≠ Ea ₂ when Ip ₄ = Ip _2, and a Ip ₄ ≠ Ip ₂ when Ea ₄ = Ea _2. That is, the relationship of the electron affinity of the constituent material for the hole injecting and transporting layer constituting material and the anode side light emitting layer host material and the central light-emitting layer of is _{Ea 1 = Ea 4 ≧ Ea 2} , Ip 1 = Ip 4 = When Ip ₂ , Ea ₁ ≠ Ea ₂ and Ea ₄ ≠ Ea ₂ , and when Ea ₁ = Ea ₄ = Ea ₂ , Ip ₁ ≠ Ip ₂ and Ip ₄ ≠ Ip ₂ .
Since the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are also different, Ea ₂ ≠ Ea ₅ when Ip ₂ = Ip ₅ and Ip ₂ ≠ Ip ₅ when Ea ₂ = Ea ₅ . That is, the relationship between the ionization potential of the constituent material of the central light emitting layer, the host material of the cathode side light emitting layer, and the constituent material of the electron injection transport layer is Ip ₂ ≧ Ip ₅ = Ip ₃ and Ip ₂ = Ip ₅ = Ip when ₃ Ea ₂ ≠ Ea ₅ and Ea ₂ ≠ Ea _3, and a Ip ₂ ≠ Ip ₅ and Ip ₂ ≠ Ip ₃ when _{Ea 2 = Ea 5 = Ea 3} .

In this embodiment, the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, and the hole injection The relationship between the electron affinity of the constituent material of the transport layer and the constituent material of the central light emitting layer is Ea ₁ ≧ Ea ₂ , and the relationship between the ionization potentials of the constituent material of the central light emitting layer and the constituent material of the electron injection transport layer is Ip ₂ ≧ Ip ₃ , the penetration of holes and electrons into the counter electrode occurs, but the holes and electrons are smoothly transported between the anode and the cathode. There is no charge accumulation at the interface and the interface between the cathode-side light emitting layer and the electron injecting and transporting layer, and deterioration at the interface between these layers can be suppressed. Accordingly, it is possible to obtain a remarkably stable lifetime characteristic and to reduce the color change.

  In the present embodiment, the host material of the anode side light emitting layer and the constituent material of the central light emitting layer are different, and the host material of the cathode side light emitting layer and the constituent material of the central light emitting layer are different. Charges are more likely to accumulate at the interface between the layer and the interface between the central light emitting layer and the cathode side light emitting layer than at the interface between the hole injection transport layer and the anode side light emitting layer, and the interface between the cathode side light emitting layer and the electron injection transport layer. Thus, light can be emitted intensively at the interface between the central light emitting layer and the anode side light emitting layer and at the interface between the central light emitting layer and the cathode side light emitting layer. In addition, since holes and electrons are transported smoothly, holes and electrons are recombined throughout the light emitting layer, so that the recombination efficiency of holes and electrons is not significantly reduced. Therefore, high efficiency can be achieved.

  Furthermore, in this embodiment, since the constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same, there is no hole injection barrier from the hole injection transport layer to the anode side light emitting layer. It is possible to reduce the voltage. Similarly, since the constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same, there is no electron injection barrier from the electron injection transport layer to the cathode side light emitting layer, and the driving voltage can be lowered. It is.

  The anode, cathode, substrate, anode-side light emitting layer, hole injection / transport layer, second hole injection / transport layer, third hole injection / transport layer, second electron injection / transport layer, and third electron injection / transport layer The cathode side light emitting layer and the electron injecting and transporting layer are the same as those described in the second embodiment, and the description thereof will be omitted here. Hereinafter, the other structure in the organic EL element of this embodiment is demonstrated.

1. In this embodiment, when the electron affinity of the constituent material of the hole injection transport layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ When the ionization potential of the constituent material of the central light emitting layer is Ip ₂ and the ionization potential of the constituent material of the electron injection transport layer is Ip ₃ , Ip ₂ ≧ Ip ₃ .

The relationship between the ionization potential and the electron affinity of the constituent material of the hole injecting and transporting layer, the host material of the anode-side light emitting layer, and the constituent material of the central light emitting layer is the same as that in the first embodiment. Description of is omitted.
The relationship between the ionization potential and the electron affinity of the constituent material of the central light emitting layer, the host material of the cathode side light emitting layer, and the constituent material of the electron injecting and transporting layer is the same as in the second embodiment. Description is omitted.

The relationship between the ionization potential and the electron affinity of the constituent materials of the hole injection transport layer and the electron injection transport layer is not particularly limited. In particular, since the hole injection transport layer and the electron injection transport layer preferably contain the same bipolar material, the ionization potential of the constituent material of the hole injection transport layer is Ip ₁ , and the ionization potential of the constituent material of the electron injection transport layer is When the potential is Ip ₃ , the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ , and the electron affinity of the constituent material of the electron injecting and transporting layer is Ea ₃ , as illustrated in FIG. 22, Ip ₁ = Ip ₃ and Ea ₁ = Ea ₃ are preferred.

  In the present embodiment, as illustrated in FIG. 23, a second hole injection / transport layer 9 may be formed between the anode 3 and the hole injection / transport layer 4. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the second hole injecting and transporting layer and the hole injecting and transporting layer is the same as that in the first embodiment, and a description thereof will be omitted here.

  In the present embodiment, as illustrated in FIG. 23, the second electron injection / transport layer 10 may be formed between the electron injection / transport layer 7 and the cathode 8. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the electron injecting and transporting layer and the second electron injecting and transporting layer is the same as that in the first embodiment, and a description thereof will be omitted here.

  In the present embodiment, as illustrated in FIG. 24, the third hole injection / transport layer 11 may be formed between the second hole injection / transport layer 9 and the hole injection / transport layer 4. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the second hole injecting and transporting layer, the third hole injecting and transporting layer, and the hole injecting and transporting layer is the same as that in the first embodiment. The description in is omitted.

  In the present embodiment, as illustrated in FIG. 24, the third electron injection / transport layer 12 may be formed between the electron injection / transport layer 7 and the second electron injection / transport layer 10. In this case, the relationship between the ionization potential and the electron affinity of the constituent materials of the electron injecting and transporting layer, the third electron injecting and transporting layer, and the electron affinity is the same as that in the first embodiment. Is omitted.

  In addition, the measuring method of the ionization potential and electron affinity of the constituent material of each layer is as having described in the said 1st embodiment.

2. Central light-emitting layer The central light-emitting layer in the present embodiment is formed between the anode-side light-emitting layer and the cathode-side light-emitting layer. The constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different, that is, the constituent material of the central light emitting layer and the constituent material of the hole injection transport layer are also different. Further, the constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different, that is, the constituent material of the central light emitting layer and the constituent material of the electron injecting and transporting layer are also different. The central light emitting layer has a function of emitting light by providing a recombination field between electrons and holes.

  The constituent material of the central light emitting layer may be different from the constituent material of the anode side light emitting layer and the hole injecting and transporting layer, and different from the constituent material of the cathode side light emitting layer and the electron injecting and transporting layer. In addition, since it is the same as that of the said 1st embodiment about the other point of the constituent material of a center light emitting layer, description here is abbreviate | omitted.

  When the central light emitting layer contains a host material and a light emitting dopant, the central light emitting layer preferably has one or more doped regions containing a light emitting dopant and one or more non-doped regions not containing a light emitting dopant. In the case of having a non-doped region on the anode side light emitting layer side of the central light emitting layer, it is difficult for energy transfer to occur between the light emitting dopant in the anode side light emitting layer and the light emitting dopant in the central light emitting layer, thereby improving the light emission efficiency. it can. Further, when a non-doped region is provided on the cathode side light emitting layer side of the central light emitting layer, energy transfer hardly occurs between the light emitting dopant in the cathode side light emitting layer and the light emitting dopant in the central light emitting layer, and the light emission efficiency is improved. be able to. Furthermore, when the central light emitting layer has a non-doped region sandwiched between two doped regions, energy transfer is unlikely to occur between the light emitting dopants in each doped region, and the light emission efficiency can be improved. Thus, luminous efficiency can be improved because the central light emitting layer has a non-doped region.

  The arrangement of the doped region and the non-doped region is not particularly limited as long as the central light emitting layer has one or more doped regions and one or more non-doped regions. For example, a non-doped region may be disposed on the anode side light emitting layer side of the central light emitting layer, a non-doped region may be disposed on the cathode side light emitting layer side of the central light emitting layer, and the central light emitting layer may be doped at two locations. There may be a region and one non-doped region, and the non-doped region may be disposed between the two doped regions. The central light emitting layer may have two doped regions and three non-doped regions, and the doped regions and the non-doped regions may be alternately arranged.

  Since other points of the doped region and the non-doped region are the same as those in the first embodiment, description thereof is omitted here.

  When the central light emitting layer also contains a host material and a light emitting dopant, the anode side light emitting layer, the central light emitting layer and the cathode side light emitting layer preferably contain different types of light emitting dopants. By laminating the anode side light emitting layer, the central light emitting layer, and the cathode side light emitting layer, the light emitting dopant in the anode side light emitting layer, the light emitting dopant in the central light emitting layer, and the light emitting dopant in the cathode side light emitting layer This is because energy transfer can be suppressed, each luminescent dopant can be made to emit light, luminous efficiency can be increased, and a desired luminescent color can be obtained.

  Among these, it is preferable that at least one of the anode-side light-emitting layer, the central light-emitting layer, and the cathode-side light-emitting layer, that is, a plurality of light-emitting layers contains a fluorescent light-emitting dopant and the other contains a phosphorescent light-emitting dopant. . As a result, energy transfer can be suppressed between the fluorescent light emitting dopant and the phosphorescent light emitting dopant, and both the fluorescent light emitting dopant and the phosphorescent light emitting dopant can be made to emit light, thereby increasing the light emission efficiency and obtaining a desired light emission color. is there.

  When the anode side light emitting layer, the central light emitting layer, and the cathode side light emitting layer contain different types of light emitting dopants, the light emission colors of the different types of light emitting dopants may be the same or different. Especially, it is preferable that the luminescent color of a different kind of light emission dopant differs. It is because a desired luminescent color can be obtained by making each luminescent dopant shine.

  In this embodiment, when white light is obtained, it is preferable to contain different types of light emitting dopants in the anode side light emitting layer, the central light emitting layer, and the cathode side light emitting layer. Among these, it is preferable to use three kinds of light emitting dopants of red, blue, and green.

  When three kinds of light emitting dopants of red, blue and green are used, as described above, at least one of the anode side light emitting layer, the central light emitting layer and the cathode side light emitting layer contains a fluorescent light emitting dopant, and the others are Since it is preferable to contain a phosphorescent dopant, for example, a blue fluorescent dopant, a red phosphorescent dopant, and a green fluorescent dopant are used, or a red fluorescent dopant, a blue phosphorescent dopant, and a green fluorescent dopant are used. It is preferable to use it.

  Since the thickness of the central light emitting layer and the film forming method are the same as those in the first embodiment, description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
First, the structural formulas of the materials used in the examples, the ionization potential, and the electron affinity are shown below.

[Example 1]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. Its ITO substrate, the total thickness 10nm and TBADN and MoO ₃ represented by the structural formula under the condition of a vacuum degree of 10 ^-5 Pa by volume 67:33, by co-deposition at a deposition rate of 1.0 Å / sec Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and using TBPe represented by the above structural formula as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe are vacuumed so that the TBPe concentration is 3 wt%. A blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under the condition of a degree of 10 ⁻⁵ Pa.
Next, TBADN is used as a host material, C545T represented by the above structural formula is used as a green light emitting dopant, and TBADN and C545T are placed on the blue light emitting layer so that the C545T concentration is 3 wt%. Under the condition of 10 ⁻⁵ Pa, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 Å / sec.
Next, using CBP represented by the above structural formula as a host material and using Ir (piq) ₃ represented by the above structural formula as a red light emitting dopant, CBP and Ir (piq) on the green light emitting layer the _3, Ir (piq) as ₃ concentration of 3 wt%, was formed by vacuum evaporation under the condition of a vacuum degree of 10 ^-5 Pa, a thickness of 10nm at a deposition rate of 1 Å / sec, the red light-emitting layer (3 The light emitting layer) was formed.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, a film thickness of TBADN and Liq represented by the above structural formula is co-evaporated at a deposition rate of 1 mm / sec on the electron transport layer under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. The film was formed to 10 nm to form an electron injection layer (second electron injection transport layer).

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Comparative Example 1]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, α-NPD and MoO ₃ represented by the above structural formula were combined at a deposition rate of 1.0 Å / sec by co-evaporation under a vacuum ratio of 10 ^-5 Pa at a volume ratio of 67:33. A film was formed to a thickness of 10 nm to form a hole injection layer. Next, α-NPD and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 under a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. On top of that, α-NPD was vacuum-deposited to a thickness of 10 nm to form a hole transport layer.

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TBADN as the host material and C545T as the green light-emitting dopant, TBADN and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the green light emitting layer, and the Ir (piq) ₃ concentration becomes 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, on the light emitting layer, Alq ₃ represented by the above structural formula was deposited by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa. A transport layer was formed. Next, on the above electron transport layer, Alq ₃ and Liq were formed to a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-evaporation under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ⁻⁵ Pa, An electron injection layer was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 2 shows the light emission characteristics of the organic EL elements of Example 1 and Comparative Example 1 under 10 mA / cm ² .

From the organic EL devices of Example 1 and Comparative Example 1, emission peaks derived from TBPe, C545T, and Ir (piq) ₃ were observed. In the organic EL device of Example 1, the luminous efficiency of the front luminance is 6.8 cd / A, and the external quantum efficiency is determined from the number of photons obtained by observing the light emitted to all angles and the number of electrons input. The calculated value was 3.4%. On the other hand, in the organic EL device of Comparative Example 1, the luminous efficiency of front luminance was 6.1 cd / A, and the external quantum efficiency was 3.1%. Regarding the lifetime characteristics, the luminance half-life from the initial luminance of 1000 cd / m ² was observed under a constant current density, and in the organic EL device of Example 1, the luminance half-life was 150 hours. On the other hand, in the organic EL device of Comparative Example 1, the luminance was reduced by half in 100 hours.

[Example 2]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using CBP as a host material and using Ir (ppy) ₃ represented by the above structural formula as a green light-emitting dopant, CBP and Ir (ppy) ₃ on the blue light-emitting layer, Ir (ppy) ₃ Form a green light-emitting layer (second light-emitting layer) by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ^-5 Pa so that the concentration is 3 wt%. Formed.
Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the green light emitting layer, and the Ir (piq) ₃ concentration becomes 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Comparative Example 2]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, α-NPD and MoO ₃ were formed by co-evaporation with a volume ratio of 67:33 and a vacuum of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. A hole injection layer was formed. Next, α-NPD and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 under a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. On top of that, α-NPD was vacuum-deposited to a thickness of 10 nm to form a hole transport layer.

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, CBP is used as the host material, Ir (ppy) ₃ is used as the green light emitting dopant, and CBP and Ir (ppy) ₃ are formed on the blue light emitting layer so that the Ir (ppy) ₃ concentration is 3 wt%. As described above, a green light-emitting layer (second light-emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.
Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the green light emitting layer, and the Ir (piq) ₃ concentration becomes 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, Alq ₃ was deposited on the light-emitting layer by vacuum deposition under a condition of a vacuum degree of 10 ⁻⁵ Pa at a deposition rate of 1 Å / sec to a thickness of 10 nm to form an electron transport layer. Next, on the above electron transport layer, Alq ₃ and Liq were formed to a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-evaporation under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ⁻⁵ Pa, An electron injection layer was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 3 shows the light emission characteristics of the organic EL elements of Example 2 and Comparative Example ² under 10 mA / cm ² .

From the organic EL devices of Example 2 and Comparative Example 2, emission peaks derived from TBPe, Ir (ppy) ₃ , and Ir (piq) ₃ were observed. In the organic EL device of Example 2, the luminous efficiency of the front luminance is 11.4 cd / A, and the external quantum efficiency is determined from the number of photons obtained by observing the light emitted to all angles and the number of electrons input. The calculated value was 6.1%. On the other hand, in the organic EL device of Comparative Example 2, the luminous efficiency of the front luminance was 9.2 cd / A, and the external quantum efficiency was 5.4%. As for the lifetime characteristics, the luminance half-life from an initial luminance of 1000 cd / m ² was observed under a constant current density, and in the organic EL device of Example 2, the luminance half-life was 100 hours. On the other hand, in the organic EL device of Comparative Example 2, the luminance was reduced by half in 70 hours.

[Example 3]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TBADN as the host material and C545T as the green light-emitting dopant, TBADN and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the green light emitting layer, and the Ir (piq) ₃ concentration becomes 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, CBP was deposited on the light-emitting layer by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an electron transport layer (first layer of electrons) An injection transport layer) was formed. Next, on the electron transport layer, CBP and Liq were deposited to a thickness of 10 nm at a deposition rate of 1 mm / sec by co-evaporation under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Example 4]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TBADN as the host material and C545T as the green light-emitting dopant, TBADN and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting region (dope region) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec. Next, TBADN was deposited on the doped region by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form a non-doped region. Thus, a green light emitting layer (second light emitting layer) having a doped region and a non-doped region was obtained.
Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the green light emitting layer, and the Ir (piq) ₃ concentration becomes 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Example 5]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TBADN as the host material and C545T as the green light-emitting dopant, TBADN and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, CBP was deposited on the green light emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, thereby forming a non-doped region. Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the non-doped region so that the Ir (piq) ₃ concentration becomes 3 wt%. In addition, a red light emitting region (dope region) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa. As a result, a red light emitting layer (third light emitting layer) having a non-doped region and a doped region was obtained.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

[Example 6]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TBADN as the host material and C545T as the green light-emitting dopant, TBADN and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, CBP was deposited on the green light emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, thereby forming a non-doped region. Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the non-doped region so that the Ir (piq) ₃ concentration becomes 3 wt%. In addition, a red light emitting region (dope region) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa. Next, CBP was deposited on the doped region by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form a non-doped region. Thus, a red light emitting layer (third light emitting layer) having a non-doped region, a doped region, and a non-doped region was obtained.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, TBADN and Liq were formed into a film with a film thickness of 10 nm at a deposition rate of 1 mm / sec by co-deposition under a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 4 shows the light emission characteristics of the organic EL elements of Examples 3 to 6 under 10 mA / cm ² .

It was confirmed that current efficiency was improved by providing a non-doped region at the interface of each light emitting layer. The luminance half life from the initial luminance 1000 cd / m ² was 150 hours or more in both elements.

[Example 7]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, DNTPD represented by the above structural formula was formed to a film thickness of 40 nm at a deposition rate of 1.0 Å / sec by co-evaporation under a vacuum degree of 10 ^-5 Pa, and hole injection A layer (first hole injecting and transporting layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 and under a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 10 nm at a deposition rate of 1.0 sec / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TBADN as the host material and C545T as the green light-emitting dopant, TBADN and C545T are placed on the blue light-emitting layer under the conditions of a vacuum degree of 10 ⁻⁵ Pa so that the C545T concentration is 3 wt%. Then, a green light emitting layer (second light emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 cm / sec.
Next, CBP was deposited on the green light emitting layer by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, thereby forming a non-doped region. Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the non-doped region so that the Ir (piq) ₃ concentration becomes 3 wt%. In addition, a red light emitting region (dope region) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa. Next, CBP was deposited on the doped region by vacuum deposition to a thickness of 5 nm at a deposition rate of 1.0 Å / sec under a vacuum degree of 10 ⁻⁵ Pa to form a non-doped region. Thus, a red light emitting layer (third light emitting layer) having a non-doped region, a doped region, and a non-doped region was obtained.

Next, TBADN was deposited on the light-emitting layer by vacuum deposition under the condition of a vacuum degree of 10 ^-5 Pa and a deposition rate of 1 mm / sec to a thickness of 10 nm, and an electron transport layer (first electron layer) An injection transport layer) was formed. Next, on the electron transport layer, BCP represented by the above structural formula and Liq are co-deposited at a deposition rate of 1 mm / sec under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An electron injection layer (second electron injection transport layer) was formed to a thickness of 10 nm.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 5 shows the light emission characteristics of the organic EL device of Example 7 under 10 mA / cm ² .

From the organic EL device of Example 7, emission peaks derived from TBPe, C545T, and Ir (piq) ₃ were observed. Comparing the organic EL elements of Example 6 and Example 7, the organic EL element of Example 6 has a luminous efficiency of front luminance of 8.4 cd / A, and is obtained by observing the light emitted to all angles. The external quantum efficiency calculated from the number of photons and the number of electrons input was 4.3%. On the other hand, in the organic EL device of Example 7, the luminous efficiency of the front luminance was 8.6 cd / A, and the external quantum efficiency was 4.4%. As for the lifetime characteristics, the luminance half-life from an initial luminance of 1000 cd / m ² was observed under a constant current density, and in the organic EL elements of Examples 6 and 7, the luminance halving time reached 150 hours each. did.

[Example 8]
(Production of organic EL element)
First, an ITO substrate in which ITO was patterned into a 2 mm wide line as an anode on a glass substrate was prepared. On the ITO substrate, TBADN and MoO ₃ were deposited at a volume ratio of 67:33 under a vacuum degree of 10 ^-5 Pa so that the total film thickness was 10 nm at a deposition rate of 1.0 mm / sec. Then, a hole injection layer (first hole injection transport layer) was formed. Next, TBADN and MoO ₃ were vacuum-deposited at a volume ratio of 90:10 at a vacuum degree of 10 ^-5 Pa by co-evaporation to a total film thickness of 100 nm at a deposition rate of 1.0 Å / sec. TBADN was vacuum-deposited to a thickness of 10 nm to form a hole transport layer (second hole injection transport layer).

Next, using TBADN as the host material and TBPe as the blue light-emitting dopant, on the hole transport layer, TBADN and TBPe, conditions of a vacuum degree of 10 ^-5 Pa so that the TBPe concentration is 3 wt% Then, a blue light-emitting layer (first light-emitting layer) was formed by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 cm / sec.
Next, using TCTA represented by the above structural formula as a host material, and using C545T represented by the above structural formula as a green light emitting dopant, TCTA and C545T on the blue light emitting layer, C545T concentration of 3 wt% Thus, a green light-emitting layer (second light-emitting layer) was formed by vacuum deposition to a thickness of 5 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.
Next, using CBP as the host material and Ir (piq) ₃ as the red light emitting dopant, CBP and Ir (piq) ₃ are added onto the green light emitting layer, and the Ir (piq) ₃ concentration becomes 3 wt%. As described above, a red light emitting layer (third light emitting layer) was formed by vacuum vapor deposition to a thickness of 10 nm at a vapor deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa.

Next, CBP was deposited on the light-emitting layer by vacuum deposition to a thickness of 10 nm at a deposition rate of 1 Å / sec under a vacuum degree of 10 ⁻⁵ Pa, and an electron transport layer (first layer of electrons) An injection transport layer) was formed. Next, on the electron transport layer, CBP and Liq were deposited to a thickness of 10 nm at a deposition rate of 1 mm / sec by co-evaporation under the condition of a volume ratio of 1: 1 and a degree of vacuum of 10 ^-5 Pa. An injection layer (second electron injection transport layer) was formed.

  Finally, Al was deposited as a cathode on the electron injection layer to a thickness of 100 nm at a deposition rate of 5 mm / sec.

(Evaluation)
Table 6 shows the light emission characteristics of the organic EL device of Example 8 under 10 mA / cm ² .

From the organic EL device of Example 8, emission peaks derived from TBPe, C545T, and Ir (piq) ₃ were observed. Comparing the organic EL elements of Example 3 and Example 8, the organic EL element of Example 3 has a luminous efficiency of front luminance of 7.1 cd / A, and is obtained by observing the light emitted to all angles. The external quantum efficiency calculated from the number of photons and the number of electrons input was 3.6%. On the other hand, in the organic EL device of Example 8, the luminous efficiency of front luminance was 7.6 cd / A, and the external quantum efficiency was 4.0%. Regarding the lifetime characteristics, when the luminance half-life from the initial luminance of 1000 cd / m ² was observed under a constant current density, the organic EL elements of Examples 3 and 8 achieved 150 hours of luminance reduction time, respectively. did.

DESCRIPTION OF SYMBOLS 1 ... Organic EL element 2 ... Substrate 3 ... Anode 4 ... Hole injection transport layer 5a ... Anode side light emitting layer 5b ... Cathode side light emitting layer 6 ... Central light emitting layer 7 ... Electron injection transport layer 8 ... Cathode 9 ... Second hole Injection transport layer 10 ... Second electron injection transport layer 11 ... Third hole injection transport layer 12 ... Third electron injection transport layer 16a ... Second central light emitting layer 16b ... Third central light emitting layer 21, 21a, 21b ... Doped region 22 ... Non-doped region

Claims (23)

An anode, a hole injecting and transporting layer formed on the anode, an anode side light emitting layer formed on the hole injecting and transporting layer and containing a host material and a light emitting dopant, and formed on the anode side light emitting layer An organic electroluminescence device having a central light emitting layer formed, an electron injection transport layer formed on the central light emission layer, and a cathode formed on the electron injection transport layer,
The constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same,
The constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different,
When the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and ionization of the constituent material of the central light emitting layer the potential Ip _2, when the ionization potential of the constituent material of the electron injection transport layer was Ip _3, the organic electroluminescent device which is a Ip ₂ ≧ Ip _3. An anode, a hole injecting and transporting layer formed on the anode, a central light emitting layer formed on the hole injecting and transporting layer, formed on the central light emitting layer, and containing a host material and a light emitting dopant An organic electroluminescence device having a cathode side light emitting layer, an electron injection transport layer formed on the cathode side light emission layer, and a cathode formed on the electron injection transport layer,
The constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same,
The constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different,
When the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and ionization of the constituent material of the central light emitting layer the potential Ip _2, when the ionization potential of the constituent material of the electron injection transport layer was Ip _3, the organic electroluminescent device which is a Ip ₂ ≧ Ip _3. An anode, a hole injecting and transporting layer formed on the anode, an anode side light emitting layer formed on the hole injecting and transporting layer and containing a host material and a light emitting dopant, and formed on the anode side light emitting layer A central light emitting layer formed on the central light emitting layer, a cathode side light emitting layer containing a host material and a light emitting dopant, an electron injecting and transporting layer formed on the cathode side light emitting layer, and the electron injecting and transporting An organic electroluminescent device having a cathode formed on the layer,
The constituent material of the hole injection transport layer and the host material of the anode side light emitting layer are the same,
The constituent material of the electron injection transport layer and the host material of the cathode side light emitting layer are the same,
The constituent material of the central light emitting layer and the host material of the anode side light emitting layer are different,
The constituent material of the central light emitting layer and the host material of the cathode side light emitting layer are different,
When the electron affinity of the constituent material of the hole injecting and transporting layer is Ea ₁ and the electron affinity of the constituent material of the central light emitting layer is Ea ₂ , Ea ₁ ≧ Ea ₂ and ionization of the constituent material of the central light emitting layer the potential Ip _2, when the ionization potential of the constituent material of the electron injection transport layer was Ip _3, the organic electroluminescent device which is a Ip ₂ ≧ Ip _3.   The hole injection transport layer and the electron injection transport layer contain a bipolar material capable of transporting holes and electrons, and the bipolar materials contained in the hole injection transport layer and the electron injection transport layer are the same. The organic electroluminescent element according to claim 1.   The hole injection transport layer and the electron injection transport layer contain a bipolar material capable of transporting holes and electrons, and the bipolar materials contained in the hole injection transport layer and the electron injection transport layer are the same. The organic electroluminescent element according to claim 2.   The hole injection transport layer and the electron injection transport layer contain a bipolar material capable of transporting holes and electrons, and the bipolar materials contained in the hole injection transport layer and the electron injection transport layer are the same. The organic electroluminescent element according to claim 3.   The central light emitting layer contains a host material and a light emitting dopant, and the constituent material of the electron injecting and transporting layer and the host material of the central light emitting layer are the same, and the constituent material of the hole injecting and transporting layer and the electron injecting and transporting layer The organic electroluminescent element according to claim 1, wherein the constituent materials are different.   The central light emitting layer contains a host material and a light emitting dopant, the constituent material of the hole injection transport layer and the host material of the central light emitting layer are the same, the constituent material of the hole injection transport layer, and the electron injection transport The organic electroluminescence device according to claim 2, wherein the constituent materials of the layers are different.   A second central light emitting layer containing a host material and a light emitting dopant is formed between the anode side light emitting layer and the central light emitting layer, and the host material of the second central light emitting layer is a host material of the anode side light emitting layer. The organic electroluminescence device according to claim 1, 4 or 7, wherein the organic electroluminescence devices are the same.   A third central light emitting layer containing a host material and a light emitting dopant is formed between the cathode side light emitting layer and the central light emitting layer, and the host material of the third central light emitting layer is a host material of the cathode side light emitting layer. The organic electroluminescence device according to claim 2, 5 or 8, wherein the organic electroluminescence devices are the same.   The central light-emitting layer contains a host material and a light-emitting dopant, and has one or more doped regions containing the light-emitting dopant and one or more non-doped regions not containing the light-emitting dopant. The organic electroluminescent element in any one of Claim 1-10.   The said anode side light emitting layer has one or more dope area | regions which contain the said light emission dopant, and one or more non-dope area | regions which do not contain the said light emission dopant, The claim | item 3 characterized by the above-mentioned. The organic electroluminescent element according to claim 6, claim 7, claim 9, or claim 11.   The said cathode side light emitting layer has one or more dope area | regions which contain the said light emission dopant, and one or more non-dope area | regions which do not contain the said light emission dopant, The claim 2, the claim 3, the claim 5 characterized by the above-mentioned. The organic electroluminescent element according to claim 6, claim 8, claim 10, or claim 11.   The organic electroluminescence device according to claim 11, wherein the central light emitting layer has the non-doped region on the hole injection transport layer side.   The organic electroluminescent element according to claim 11 or 14, wherein the central light emitting layer has the non-doped region on the electron injecting and transporting layer side.   The central light emitting layer has the two doped regions, the non-doped region is disposed between the two doped regions, and the two doped regions contain different types of light emitting dopants. The organic electroluminescence device according to claim 11, wherein the organic electroluminescence device is characterized by.   The organic electroluminescent element according to claim 12, wherein the anode side light emitting layer has the non-doped region on the central light emitting layer side.   The anode side light emitting layer has two doped regions, the non-doped region is disposed between the two doped regions, and the two doped regions contain different types of light emitting dopants. The organic electroluminescent element according to claim 12 or 17, wherein   The organic electroluminescence device according to claim 13, wherein the cathode side light emitting layer has the non-doped region on the central light emitting layer side.   The cathode side light emitting layer has the two doped regions, the non-doped region is disposed between the two doped regions, and the two doped regions contain different types of light emitting dopants. The organic electroluminescent element according to claim 13 or 19, wherein A second hole injecting and transporting layer is formed between the anode and the hole injecting and transporting layer, and Ea ₆ <Ea ₁ when the electron affinity of the constituent material of the second hole injecting and transporting layer is Ea ₆ 21. The organic material according to claim ₁ , wherein Ip ₆ ≦ Ip ₁ when the ionization potential of the constituent material of the second hole injecting and transporting layer is Ip _6. Electroluminescence element. A second electron injecting and transporting layer is formed between the electron injecting and transporting layer and the cathode, and when the ionization potential of the constituent material of the second electron injecting and transporting layer is Ip ₇ , Ip ₃ <Ip ₇ and the organic electroluminescent device according to any one of claims 1 to 21, characterized in that the electron affinity of the constituent material of the second electron injecting and transporting layer is Ea ₃ ≦ Ea ₇ when the Ea _7.   The organic electro according to any one of claims 1 to 22, wherein at least one of the plurality of light emitting layers contains a fluorescent light emitting dopant and the other contains a phosphorescent light emitting dopant. Luminescence element.

Images