JPH10162959A - Organic electroluminescence device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To have a cathode having low resistance and high transparency,
Provided is an organic electroluminescent element (EL element) which has excellent luminous efficiency and durability (moisture and heat resistance) and can be used as a transparent light emitting element. An organic EL device having an organic layer including an organic light emitting layer interposed between an anode and a cathode, wherein the cathode comprises an electron injection cathode layer and an amorphous transparent conductive film, and An organic EL device having a configuration in which an electron injection cathode layer is in contact with the organic layer is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly durable organic electroluminescent device capable of extracting light emission from both sides of the device.

[0002]

2. Description of the Related Art Electroluminescent devices utilizing electroluminescence (hereinafter abbreviated as EL devices) have high visibility due to self-luminescence and are completely solid devices.
Due to its characteristics such as excellent impact resistance, attention has been paid to its use as a light emitting element in various display devices.

[0003] An EL element includes an inorganic EL element using an inorganic compound as a light emitting material and an organic EL element using an organic compound.
Among them, organic EL elements are easy to be miniaturized so that the applied voltage can be significantly reduced. Therefore, research on practical use as a next-generation display element has been actively conducted.
The structure of the organic EL element is basically based on the structure of anode / light-emitting layer / cathode, and a structure in which a transparent anode is laminated on a substrate using a glass plate or the like is usually adopted. In this case, light emission is extracted to the substrate side.

[0004] In recent years, attempts have been made to make the cathode transparent to extract light emission to the cathode side for the following reasons. (A) If the anode is transparent, a transparent light emitting element can be obtained. (A) An arbitrary color can be adopted as the background color of the transparent light emitting element, and a colorful display can be obtained even when light is not emitted, and the decorativeness is improved. When black is used as the background color, the contrast at the time of light emission is improved. (C) When a color filter or a color conversion layer is used, these can be placed on the light emitting element. Therefore, the device can be manufactured without considering these layers. As an advantage, for example, when forming the anode, the substrate temperature can be increased, thereby reducing the resistance value of the anode.

Since the above-mentioned advantages can be obtained by making the cathode transparent, attempts have been made to produce an organic EL device using a transparent cathode. JP-A-8-18598
Japanese Patent Application Laid-Open No. 4 (1999) -1992 discloses a transparent organic EL provided with a first electrode layer made of a transparent conductive layer, an ultrathin electron injection metal layer, and a second electrode layer made of a transparent conductive layer formed thereon. An element is disclosed. And, as a material constituting these transparent conductive layers, ITO (indium tin oxide) is used.
And SnO ₂ are disclosed. However, they cannot lose crystallinity to the extent that the X-ray diffraction peak disappears, and are essentially crystalline. For this reason, when laminating on a substrate via an organic layer, when the substrate temperature is set at room temperature to near 100 ° C. in order to prevent damage to the organic layer, a transparent conductive layer having a high specific resistance is formed ( In the case of ITO, it is about 1 × 10 ⁻³ Ω · cm or more.) And
In such an organic EL element, a voltage drop occurs in the wiring line of the transparent conductive layer, and non-uniformity occurs in light emission. Therefore, improvement in lowering the specific resistance value is required. Also, I
Since TO and SnO ₂ are crystalline in nature, moisture and oxygen tend to penetrate through the crystal grain boundaries. For this reason, the electron-injection metal layer stacked adjacently is liable to be deteriorated, and as a result, a light-emitting defect occurs or the light-emission stops, and the durability is not sufficient, and further improvement is required. I have.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic EL device having a low-resistance and highly transparent cathode by solving the above-mentioned prior art. Another object of the present invention is to provide an organic EL element which is less likely to penetrate moisture and oxygen from a transparent conductive film constituting a cathode and has excellent durability.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, by adopting an amorphous transparent conductive film as a transparent conductive film constituting a cathode, It has been found that the above problem is solved. The present invention has been completed based on such findings.

That is, the gist of the present invention is as follows. (1). An organic electroluminescence device in which an organic layer including an organic light emitting layer is interposed between an anode and a cathode, wherein the cathode comprises an electron injection electrode layer and an amorphous transparent conductive film, and the electron injection electrode An organic electroluminescent device, wherein a layer is in contact with the organic layer. (2). The electron injecting electrode layer is one or two selected from an electron injecting metal, an alloy, and an alkaline earth metal oxide;
The organic electroluminescent device according to the above (1), wherein the organic electroluminescent device is formed in an ultra-thin film shape using at least one kind. (3). The electron injecting electrode layer is one or two selected from an electron injecting metal, an alloy, and an alkaline earth metal oxide;
The organic electroluminescence device according to the above (1), wherein the organic electroluminescence device is a mixed layer of an organic material having electron conductivity and at least species. (4). 2. The organic electroluminescence device according to claim 1, wherein the electron injection electrode layer comprises an island-shaped electron injection region. (5). Any of (1) to (4), wherein the amorphous transparent conductive film is formed using an oxide made of indium (In), zinc (Zn), and oxygen (O). 3. The organic electroluminescent device according to 1.).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the organic EL device of the present invention, an organic layer including an organic light emitting layer is interposed between an anode and a cathode, and the cathode is composed of an electron injection electrode layer and an amorphous transparent conductive film. It has a configuration in which the injection electrode layer is in contact with the organic layer. This configuration can be schematically represented by, for example, FIG. Hereinafter, these configurations will be described.

<Amorphous Transparent Conductive Film> First, the amorphous transparent conductive film constituting the cathode in the organic EL device of the present invention will be described. The amorphous transparent conductive film used in the present invention is not particularly limited as long as it is amorphous and has transparency, but as described above, in order to eliminate non-uniformity of voltage drop and emission caused by the voltage drop, It is preferable that the specific resistance value is 5 × 10 ⁻⁴ Ω · cm or less.

The material is preferably an In-Zn-O-based oxide film. Here, an In—Zn—O-based oxide film refers to indium (In) as a main cation element.
And a transparent conductive film made of an amorphous oxide containing zinc (Zn). Atomic ratio of In [In / (In + Zn)]
Is preferably from 0.45 to 0.90. This is because the conductivity may be reduced outside this range. The atomic ratio [In / (In + Zn)] of In is 0.1 in terms of conductivity.
It is particularly preferably from 50 to 0.90, more preferably from 0.70 to 0.85.

[0012] The amorphous oxide may contain substantially only In and Zn as main cation elements, or may contain one or more third cations having a valence of 3 or more.
It may contain an element. Specific examples of the third element include tin (Sn), aluminum (Al),
Antimony (Sb), gallium (Ga), germanium (Ge), titanium (Ti) and the like can be mentioned, but those containing Sn are particularly preferable in that conductivity is improved. Further, the content of the third element is preferably such that the atomic ratio of the total amount ((all third elements) / (In + Zn + (all third elements)) is 0.2 or less. If the ratio exceeds 0.2, the conductivity may decrease due to ion scattering, and a particularly preferable atomic ratio of the total amount of the third element is 0.1 or less.
Crystallized ones are less conductive than amorphous ones,
From this point, it is necessary to use an amorphous transparent conductive film.

The above-mentioned amorphous oxide can be used as a transparent conductive film by forming it into a thin film. The film thickness at this time is
Preferably, the thickness is approximately 3 to 3000 nm. It is 3
If the thickness is less than 300 nm, the conductivity tends to be insufficient, and
m, the light transmittance is reduced, or the organic E element is intentionally or inevitably produced during or after the production of the organic EL device.
When the L element is deformed, cracks and the like easily occur in the transparent conductive film. The particularly preferred thickness of the transparent conductive film is 5 to 1
000 nm, more preferably 10 to 800 n
m.

In the organic EL device of the present invention, when a cathode is formed on a substrate via an anode and an organic layer, an amorphous transparent conductive film (oxide film) is formed on the electron injection electrode layer. As a method for forming the amorphous transparent conductive film, in addition to the sputtering method, a chemical vapor deposition method, a sol-gel method, an ion plating method, or the like can be adopted, but from the viewpoint of less thermal influence on the organic layer and simplicity. More preferred is a sputtering method. In this case, care must be taken so that the organic layer is not damaged by plasma generated during sputtering. Further, since the heat resistance of the organic layer is low, the temperature of the substrate is preferably set to 200 ° C. or lower.

The sputtering method is RF or D
C magnetron sputtering or reactive sputtering may be used, and the composition of the sputtering target to be used and sputtering conditions are appropriately selected according to the composition of the transparent conductive film to be formed. RF or D
In-Zn-O by C magnetron sputtering etc.
When forming a system transparent conductive film, the following (i) to
It is preferable to use the sputtering target of (ii).

(I) A sintered target made of a composition of indium oxide and zinc oxide having a predetermined indium atomic ratio. Here, “the atomic ratio of indium is predetermined” means that the atomic ratio of In in the finally obtained film [In / (In + Zn)] is a desired value in the range of 0.45 to 0.90. It means that the atomic ratio in the sintered target is approximately 0.50 to 0.90. The sintered target may be a sintered body comprising a mixture of indium oxide and zinc oxide, an In ₂
It may be a sintered body consisting essentially of one or more hexagonal layered compounds represented by O ₃ (ZnO) m (m = 2 to 20), or In ₂ O ₃ (ZnO) m (m = 2 to 20) and at least one of the hexagonal layered compounds represented by In ₂ O ₃ and / or
Alternatively, it may be a sintered body substantially composed of ZnO.
In the above formula representing a hexagonal layered compound, m is 2 to
The reason for limiting to 20 is that if m is outside the above range, the compound will not be a hexagonal layered compound.

(Ii) A sputtering target comprising an oxide-based disk and one or more oxide-based tablets disposed on the disk. The oxide-based disk may be substantially composed of indium oxide or zinc oxide, or one of hexagonal layered compounds represented by In ₂ O ₃ (ZnO) m (m = 2 to 20). From the above, a sintered body substantially consisting of In ₂ O ₃ (ZnO) m (m
= 2 to 20), and may be a sintered body substantially composed of one or more of the hexagonal layered compounds represented by In ₂ O ₃ and / or ZnO. In addition, as an oxide tablet,
The same oxide disk as above can be used. The composition and use ratio of the oxide disk and the oxide tablet are such that the atomic ratio of In [In / (In + Zn)] in the finally obtained film is 0.45 to 0.80.
Is appropriately determined so as to be a desired value within the range of.

Preferably, the sputtering target of any of the above (i) to (ii) has a purity of 98% or more. If the content is less than 98%, the moisture-heat resistance (durability) of the obtained film may be reduced, the conductivity may be reduced, or the light transmittance may be reduced due to the presence of impurities. A more preferred purity is 99% or more, and an even more preferred purity is 9%.
9.9% or more.

When a sintered target is used, the relative density of the target is preferably 70% or more. If the relative density is less than 70%, it tends to cause a decrease in the film forming rate and a decrease in the film quality. More preferred relative density is 85%
And more preferably 90% or more.

Although the sputtering conditions for providing a transparent conductive film by the direct sputtering method vary depending on the method of the direct sputtering, the composition of the sputtering target, the characteristics of the apparatus to be used, and the like, it is difficult to unconditionally define the sputtering conditions. In the case of the DC direct sputtering method, for example, it is preferable to set as follows.

The degree of vacuum and the voltage applied to the target during sputtering are preferably set as follows. The degree of vacuum during sputtering is 1.3 × 10 ^{-2 to} 6.7 × 1
0 ⁰ Pa, more preferably about 1.7 × 10 ^-2 ~ 1.3,
About × 10 ⁰ Pa, more preferably 4.0 × 10 ⁻² or more.
It is set to about 6.7 × 10 ⁻¹ Pa. Further, the applied voltage of the target is preferably 200 to 500 V. The degree of vacuum during sputtering is less than 1.3 × 10 ^-2 Pa (1.3 × 1
When the pressure is lower than 0 ^-2 Pa), the stability of the plasma is poor, and is higher than 6.7 × 10 ⁰ Pa (6.7 × 10 ⁰ P).
If the pressure is higher than a), the voltage applied to the sputtering target cannot be increased. If the target applied voltage is less than 200 V, it may be difficult to obtain a good-quality thin film, or the deposition rate may be limited.

As the atmosphere gas, a mixed gas of an inert gas such as an argon gas and an oxygen gas is preferable. When argon gas is used as the inert gas, the mixing ratio (volume ratio) of the argon gas and the oxygen gas is generally 1: 1 to 9
9.99: 0.01, preferably 9: 1 to 99.9:
0.1. Outside this range, a film having low resistance and high light transmittance may not be obtained.

The substrate temperature is appropriately selected according to the heat resistance of the organic layer within a temperature range at which the organic layer does not deform or deteriorate due to heat. If the substrate temperature is lower than room temperature, a separate cooling device is required, which increases the manufacturing cost. Further, as the substrate temperature is increased to a higher temperature, the manufacturing cost increases. For this reason, the temperature is preferably from room temperature to 200 ° C.

The target transparent conductive film can be provided on the organic layer by performing direct sputtering under the conditions described above using the sputtering targets (i) to (ii) described above.

<Electron Injection Electrode Layer> Next, the electron injection electrode layer will be described. The electron injection electrode layer is a layer of an electrode that can satisfactorily inject electrons into the organic layer including the light emitting layer. In order to obtain a transparent light emitting device, the light transmittance is preferably 50% or more. 0.5 to 20n
It is desirable to have an ultrathin film of about m.

As the electron injecting electrode layer, for example, a metal having a work function of 3.8 eV or less (electron injecting metal), for example, Mg, Ca, Ba, Sr, Li, Yb, Eu, Y,
A layer having a thickness of 1 nm to 20 nm using Sc or the like can be given. In this case, a configuration that provides a light transmittance of 50% or more, particularly 60% or more, is preferable.

Another preferred example is an electron using an alloy (an electron-injecting alloy) of the metal having a work function of 3.8 eV or less (a plurality of kinds may be used) and the metal having a work function of 4.0 eV or more. An injection electrode layer can be mentioned. As such an alloy, any alloy capable of forming an electron injection electrode layer is sufficient. For example, aluminum-lithium alloy, magnesium-aluminum alloy, indium-lithium alloy, lead-lithium alloy, bismuth-lithium alloy, Examples include a tin-lithium alloy, an aluminum-calcium alloy, an aluminum-barium alloy, and an aluminum-scandium alloy. Also in this case, it is preferable that the film thickness be 1 nm to 20 nm,
It is preferable that the layer provides a light transmittance of 0% or more, particularly 60% or more.

When the electron injection electrode layer is formed using the above metal or alloy, a resistance heating evaporation method is preferably used. In this case, it is preferable to set the substrate temperature between 10 and 100 ° C. and set the deposition rate between 0.05 and 20 nm / sec. In particular, when an alloy is deposited, 2
By using the original deposition method, deposition can be performed by individually setting the deposition rates of the two metals. In this case, Li, Ba,
The deposition rate of Ca, Sc, Mg, etc. is set to 0.01 to 0.1 n.
m / sec and the deposition rate of a base metal such as Al is 1
It is possible to adopt a method of setting the speed between 10 nm / sec and 10 nm / sec and performing simultaneous vapor deposition. In the case of depositing an alloy, a one-source deposition method can be used. In this case, a vapor-deposited pellet or granular material in which a metal having an electron-injecting property is previously charged into a base metal at a desired ratio is placed on a resistance heating boat or a filament, and heated and vapor-deposited.

As still another preferred embodiment, an ultra-thin film of an alkaline earth metal oxide having an electron injecting property having a film thickness of 0.1 nm to 10 nm can be mentioned.
Examples of the alkaline earth metal oxide include Ba
Ba _x Sr containing O, SrO, CuO and a mixture thereof
_1-x O (0 <x <1) or Ba _x Ca _1-x O (0 <x <
1) can be mentioned as preferred.

As a method of forming the alkaline earth metal oxide layer, oxygen is introduced into the vacuum chamber while the alkaline earth metal is deposited by the resistance heating evaporation method to reduce the degree of vacuum to 10 ^-3 to 1.
A method in which the pressure is set to 0 ^-4 Pa and vapor deposition is performed while reacting oxygen and alkaline earths is preferable. Further, a method of forming a film of an alkaline earth metal oxide by an electron beam evaporation method can also be employed.

The electron injecting electrode layer can be formed by using not only one kind but also two or more kinds of the metal, alloy and alkaline earth metal oxide described above.

As still another preferred example, the electron injecting electrode layer may be an electron injecting metal, alloy or a mixed layer of an alkaline earth metal oxide and an electron transporting compound.

The metals, alloys and alkaline earth metal oxides having electron injecting properties include the above-mentioned metals, alloys and alkaline earth metal oxides. These are 1
Not only species but also two or more species can be used. On the other hand, the electron-transporting compound may be any compound that transmits electrons, and preferred compounds include chelated oxinoid compounds, and more preferred compounds include those represented by the following formula.

[0034]

Embedded image

Wherein Me represents a metal, n is an integer from 1 to 3, and Z independently represents in each case an atom which completes a nucleus having at least two fused aromatic rings. The metal in the formula may be a metal having a valence of 1 to 3 having chelating ability, for example, an alkali metal such as lithium, sodium or potassium, an alkaline earth metal such as magnesium or calcium, or boron or aluminum. And the like. Also, Z
Represents an atom completing a heterocyclic nucleus having at least two fused aromatic rings. As a heterocyclic nucleus where Z is completed,
For example, an azole ring and an azine ring can be mentioned.

The useful chelated oxinoid compounds include aluminum trisoxine, magnesium bisoxin, bis [benzo (f) -8-quinolinol] zinc, bis (2-methyl-8-quinolinolate) aluminum oxide, indium trisoxine , Aluminum tris (5-methyloxin), lithium oxine, gallium trisoxin, calcium bis (5
-Chlorooxin), poly [zinc (II) -bis (8-
Hydroxy-5-quinolinonyl) methane], dilithium epindridione and the like.

The mixing ratio (weight ratio) between the electron-injecting metal, alloy, or alkaline earth metal oxide and the electron-transporting compound is preferably 100: 1 to 1: 2. The mixed layer of the electron-injecting metal or alloy and the electron-transporting compound is preferably formed by a binary simultaneous evaporation method. The substrate temperature may be set between 10 and 100 ° C.

As still another preferred example, there can be mentioned a configuration in which the electron injection electrode layer is an island-shaped electron injection region. Here, the island shape means that an electron injecting compound layer is formed discontinuously as shown in FIG. 2, for example, and this layer does not cover the surface of the organic layer. The island-shaped electron injection region is formed by, for example, discontinuously forming a metal, an oxide, a metal boride, a metal nitride, a metal silicide, or the like having a low work function of 3.8 eV or less as islands. The shape and size are not particularly limited, but are preferably in the form of fine particles or crystals having a size of about 0.5 nm to 5 μm.

Further, this electron injection region does not indicate a thin film shape, nor does it indicate a state of isolated atom dispersion. This refers to a state in which the metal or compound having a low work function is dispersed in the form of particles on the conductive thin film or in the organic compound layer. Due to such dispersion, the area in contact with the organic compound layer increases, and the electron injecting property increases.

The low work function metal and alloy constituting the island-shaped electron injection region preferably have a work function of 3.8 eV or less, and include, for example, the above-mentioned metals and alloys. Further, as the oxide having a low work function, an oxide of an alkali metal or an alkaline earth metal is preferable,
Particularly, CaO, BaO, SrO and the like are preferable.
Solid solutions of these with other metal oxides are also preferred. Further, as the low work function metal boride or metal nitride, for example, a rare earth boride, a rare earth silicide, or TiN is preferably exemplified.

As a method of forming the island-shaped electron injection region, a resistance heating evaporation method or an electron beam evaporation method can be employed. In the latter case, a high melting point metal boride, metal nitride or oxide is discontinuously formed in an island shape by electron beam evaporation.

In the organic EL device of the present invention, since the cathode is composed of the electron injection electrode layer and the amorphous transparent conductive film, the easily deteriorated electron injection electrode layer is protected by the amorphous transparent conductive film. As a result, the thickness of the electron injection electrode layer can be reduced, and as a result, a transparent cathode can be formed.

When the electron injection electrode layer comes into contact with the organic layer, electrons are injected into the organic layer. Thereby, an EL element is formed in combination with the injection of holes from the anode side. In the organic EL device of the present invention, a structure is usually adopted in which an anode is laminated on a substrate and an organic layer is laminated thereon. In this case, an electron injection electrode layer is formed on the organic layer including the organic light emitting layer. Form. Although the formation method is as described above, another preferable method is a sputtering method. In using this technique, care must be taken that the organic layer is not damaged by the plasma.

<Organic Layer> In the organic EL device of the present invention, the organic layer interposed between the anode and the cathode includes at least a light emitting layer. The organic layer may be a layer composed of only a light emitting layer, or may have a multilayer structure in which a hole injection transport layer and the like are stacked together with the light emitting layer.

In this organic EL device, the light emitting layer has the following functions: (1) a function of injecting holes by an anode or a hole transport layer and applying an electron from an electron injecting layer when an electric field is applied; 2) a transport function of moving the injected charges (electrons and holes) by the force of an electric field; and (3) a light-emitting function of providing a field for recombination of electrons and holes inside the light-emitting layer and connecting it to light emission. Have. There is no particular limitation on the type of light emitting material used for the light emitting layer, and a known material for an organic EL element can be used.

The hole injecting and transporting layer is a layer made of a hole transporting compound and has a function of transmitting holes injected from the anode to the light emitting layer. By interposing between the light emitting layer and the light emitting layer, many holes are injected into the light emitting layer at a lower electric field. In addition, the electrons injected from the electron injection layer into the light emitting layer cause the luminous efficiency of the EL element accumulated near the interface in the light emitting layer due to the electron barrier existing at the interface between the light emitting layer and the hole injection transport layer. And an EL device having excellent light emitting performance. There is no particular limitation on the hole transport compound used in the hole injection transport layer,
Conventionally known compounds can be used as hole transport compounds in organic EL devices. The hole injecting and transporting layer can be not only a single layer but also a multilayer.

<Anode> The anode is not particularly limited as long as it has a work function of 4.8 eV or more. A metal having a work function of 4.8 eV or more, a transparent conductive film (conductive oxide film), or a combination thereof is preferable. The anode is not necessarily required to be transparent, and may be coated with a black carbon layer or the like.

Suitable metals include, for example, Au, P
t, Ni, and Pd. Examples of the conductive oxide include In-Zn-O, In-Sn-O, and Zn.
O-Al and Zn-Sn-O can be mentioned. Examples of the laminate include a laminate of Au and In—Zn—O, a laminate of Pt and In—Zn—O, and an In—Sn—
A laminate of O and Pt can be given.

Since the anode only needs to have a work function of 4.8 eV or more at the interface with the organic layer, the anode has two layers and a conductive film having a work function of 4.8 eV or less is provided on the side not in contact with the organic layer. May be used. In this case, a metal such as Al, Ta, W, or the like, an Al alloy, an alloy such as a Ta-W alloy, or the like can be used. Also, a doped conductive polymer such as doped polyaniline or doped polyphenylenevinylene, an amorphous semiconductor such as α-Si, α-SiC, α-C, μC-Si, μC-SiC, etc. Microcrystals and the like can also be preferably used. Furthermore, black semiconductive oxides such as Cr ₂ O ₃ , Pr ₂ O ₅ , NiO, Mn ₂ O ₅ ,
MnO ₂ or the like can be used.

The thickness of the anode is preferably about 50 to 300 nm. If the film thickness is less than 50 nm, the resistance value may be too high. On the other hand, when the thickness exceeds 300 nm, in an organic EL element, a step formed at an end where an anode is patterned may cause an upper film, for example, an organic layer or a cathode to be disconnected or disconnected.

<Structure of Organic EL Element> Organic EL Element of the Present Invention
In the device, an organic layer including an organic light emitting layer is interposed between an anode and a cathode, and the cathode is composed of an electron injection electrode layer and an amorphous transparent conductive film. The object of the present invention can be achieved by providing a structure in contact with a layer, but various functions can be provided by further adding another structure. Hereinafter, a configuration using the organic EL device of the present invention will be exemplified.

Transparent anode / organic layer / electron injection electrode layer /
Amorphous transparent electrode Anode / organic layer / electron injection electrode layer / amorphous transparent electrode /
Color filter anode / organic layer / electron injection electrode layer / amorphous transparent electrode /
Color conversion layer Transparent anode / organic layer / electron injection electrode layer / amorphous transparent electrode / black light absorbing layer Transparent anode / organic layer / electron injection electrode layer / amorphous transparent electrode / background color forming layer black light absorbing layer / Transparent anode / organic layer / electron injection electrode layer / amorphous transparent electrode Background color forming layer / transparent anode / organic layer / electron injection electrode layer / amorphous transparent electrode In the above configuration, both electrodes are transparent, A transparent display element is formed.

In the case of the above structure, the anode is formed on the support substrate, and light can be extracted in the direction opposite to the support substrate. Therefore, it is not necessary to form the anode on the color filter or the color conversion layer. Therefore, when forming the anode, the substrate temperature is 1
It is possible to adopt a process in which the temperature is 50 ° C. or higher, and there is a great merit in lowering the resistance value of the anode.
Further, since the color filter and the color conversion layer are formed after the formation of the anode, there is no need to worry about deterioration due to the adoption of the high temperature process. FIG. 3 illustrates an example of the configuration. Here, it is preferable that the color conversion layer is made of a transparent polymer containing a fluorescent dye, and converts the EL emission color to another color by fluorescence.

In a mode in which a large number of pixels are formed in a slightly different configuration, auxiliary wirings other than the anode and TFTs (Thin Film Transisters) are formed on the substrate. There is a drawback that the auxiliary wiring and the TFT block light, and the aperture ratio of light extraction is reduced, resulting in a decrease in display brightness and image quality. According to the present invention, light can be extracted in the direction opposite to the direction of the substrate. In this case, light is not blocked and the aperture ratio of light extraction does not decrease.

In the configuration described above, since the pixel looks black when the pixel is off, there is an advantage that external light is not reflected and the contrast of the display is improved. FIG.
FIG. In the above configuration, various background colors and patterns can be adopted, and a display having excellent decorativeness can be provided even when the pixels are off. FIG. 5 shows an example of the configuration.

In the above constitutions, the color conversion layer, the color filter, the black light absorbing layer and the background color forming layer do not necessarily have to be in close contact with the electrode, and may have an intermediate layer interposed between them. May be installed as shown in FIG. However, the color conversion layer and the color filter need to be installed in the light extraction direction, and the black light absorption layer and the background color formation layer need to be installed in the direction opposite to the light extraction direction.

[0057]

Embodiments of the present invention will be described below. Example 1 <Manufacture of Organic EL Element> A conductive thin film was formed on a glass substrate of 25 mm × 75 mm × 1 mm (manufactured by Geomatics Co., Ltd.) by forming ITO to a thickness of 100 nm. Used as is. Next, after immersing this in isopropyl alcohol and performing ultrasonic cleaning,
UV-irradiator UV-30 manufactured by Samco International
Washing was carried out for 30 minutes using UV light and ozone in combination with O.

Next, the glass substrate with the ITO thin film is put in a commercially available vacuum evaporation apparatus, attached to a substrate holder installed in the apparatus, and the vacuum chamber is set to 5 × 10 ^-4.
The pressure was reduced to Pa. In addition, a phthalocyanine (hereinafter, referred to as Cu-coordinated) is previously provided in the resistance heating boat of the vacuum evaporation apparatus.
Abbreviated as CuPc. ), N, N'-bis (3-methylphenyl) -N, N'-diphenyl- (1,1'-biphenyl) -4,4'-diamine (hereinafter abbreviated as TPD) and 8-quinolinol An aluminum complex (aluminum trisoxin; hereinafter, abbreviated as Alq) was charged in an amount of 200 mg each, and the resistance heating filament was charged with an aluminum-lithium alloy (Li content: 2% by weight). These components were deposited by sequentially heating these boats and filaments.

First, CuPc was used as a hole injection / transport layer.
25 nm was deposited on a glass substrate with a TO thin film, then TPD was deposited to a thickness of 40 nm as a second hole injection / transport layer, and Alq was deposited to a thickness of 60 nm as a light emitting layer. Next, a mask was placed on the formed laminate, and an aluminum-lithium alloy was deposited to a thickness of 7 nm to form an electron injection electrode layer.

Next, the substrate was transferred and set to a substrate holder of another vacuum tank connected to the above-mentioned vacuum evaporation apparatus.
During this period, the degree of vacuum is maintained. The above-mentioned another vacuum chamber is formed by DC magnetron sputtering.
Equipment is provided so that a Zn—O-based oxide film can be formed. The target for forming the In—Zn—O-based oxide film is a sintered body composed of In ₂ O ₃ and ZnO, and the atomic ratio of In [In / (In + Zn)] is 0.67.
It is. A mixed gas (1000: 2.8 in volume ratio) of argon gas and oxygen gas in this vacuum chamber was introduced until the gas pressure reached 3 × 10 ⁻¹ Pa, the sputtering output was set to 20 W, and the substrate temperature was set to room temperature. A 200 nm amorphous transparent conductive film was formed. Note that the fact that the In—Zn—O-based oxide film is amorphous means that a laminate is formed by a method similar to the above using a glass substrate on which an ITO thin film is not deposited, and X
It was confirmed by line diffraction.

Further, by using a method similar to the above-described method for fabricating the element, a laminate in which an electron injection electrode layer and an amorphous transparent conductive film were directly laminated on a glass substrate with an ITO thin film was fabricated, and a wavelength of 460 nm was formed. The light transmittance was measured to be 63%, which was highly transparent.

<Evaluation of Organic EL Element> The sheet resistance of the amorphous transparent conductive film formed by the manufacturing method of the above embodiment was examined by a four-probe method using Loresta FP manufactured by Mitsubishi Yuka. However, it was 17Ω / □. Since the film thickness is 200 nm, the specific resistance is 3.4 × 10 ⁻⁴ Ω ·
cm and low resistance.

Next, when a voltage of 8 V was applied using the ITO thin film as an anode and the amorphous transparent conductive film as a cathode,
The current density was 3.1 mA / cm ² , and when observed from the side of the amorphous transparent conductive film, light emission of 60 Cd / m ² was observed. Light emission was green light emitted from Alq. Furthermore, when this device was left in an atmosphere of 70% RH (relative humidity) in the atmosphere for 100 hours, no light emitting point was observed with the naked eye, and the light emitting performance of the device was maintained.

Comparative Example 1 An organic EL device was manufactured in the same manner as in Example 1.
However, instead of forming an In—Zn—O-based oxide film, an ITO film that was a crystalline transparent conductive film was formed using a commercially available ITO target.

Thereafter, the performance of the organic EL device was evaluated in the same manner as in Example 1, and the sheet resistance was 130 Ω.
/ □. And since the film thickness is 200 nm,
It was confirmed that the specific resistance was as high as 2.6 × 10 ⁻³ Ω · cm. Next, when a voltage of 8 V was applied to the organic EL device, the current density became 4 mA / cm ² , and when observed from the side of the amorphous transparent conductive film, light emission of 60 Cd / m ² was observed. Light emission was green light emitted from Alq. This device was placed in an atmosphere of 70% RH in the air for 100 hours.
After standing for a long time, countless non-emission points were confirmed with the naked eye,
It was confirmed that there were many light emission defects.

From the above results, the organic EL device of the present invention has high luminous efficiency due to the high transparency of the cathode and the low resistance of the amorphous transparent conductive film constituting the cathode, and furthermore, the organic EL device is amorphous. Therefore, it was confirmed that the durability was excellent and the light emission defect hardly occurred. By the way, it is known that a light emission defect occurs due to oxidation of the electron injection electrode layer. In the organic EL device of the present invention, an amorphous transparent conductive film is formed on the electron injection electrode layer, and since there is no crystal grain boundary in the transparent conductive film, penetration of oxygen and moisture is prevented, and It is considered that the result was obtained.

Example 2 <Preparation of Organic EL Element> A glass substrate with an ITO thin film similar to that used in Example 1 was mounted on a substrate holder in a vacuum evaporation apparatus in the same manner as in Example 1, and the × 10
^The pressure was reduced to ^-4 Pa. In addition, 200 mg each of CuPc, TPD, and Alq was put in the resistance heating boat of the vacuum evaporation apparatus, and an aluminum-lithium alloy (Li content: 2% by weight) was put in the resistance heating filament.

First, CuPc was deposited on a glass substrate with an ITO thin film to a thickness of 25 nm, TPD was deposited to a thickness of 40 nm, and Alq was deposited to a thickness of 60 nm. Next, a mask is placed on the formed laminate, oxygen is introduced until the degree of vacuum becomes 1 × 10 ⁻³ Pa, and barium (Ba) is deposited to a thickness of 1.0 nm.
Vapor deposition was performed to form BaO as an electron injection electrode layer. Ba reacts with oxygen present in the vacuum chamber and produces BaO.
An electron injection electrode layer is formed.

Next, the substrate was transferred and set to a substrate holder of another vacuum chamber connected to the above-mentioned vacuum deposition apparatus.
During this period, the degree of vacuum is maintained. The above-mentioned another vacuum chamber is formed by DC magnetron sputtering.
Equipment is provided so that a Zn—O-based oxide film can be formed. The target for forming the In—Zn—O-based oxide film is a sintered body composed of In ₂ O ₃ and ZnO, and the atomic ratio of In [In / (In + Zn)] is 0.84.
It is. A mixed gas (volume ratio: 1000: 5.0) of argon gas and oxygen gas in this vacuum chamber was introduced until the pressure reached 3 × 10 ⁻¹ Pa, the sputtering output was set to 20 W, the substrate temperature was set to room temperature, and the film thickness was set. A 200 nm amorphous transparent conductive film was formed. Note that the fact that the In—Zn—O-based oxide film is amorphous means that a laminate is formed by a method similar to the above using a glass substrate on which an ITO thin film is not deposited, and X
It was confirmed by line diffraction.

<Evaluation of Organic EL Element> When the sheet resistance of the amorphous transparent conductive film formed by this manufacturing method was examined in the same manner as in Example 1, it was 16 Ω / □.
Since the film thickness is 200 nm, the specific resistance is 3.
It was confirmed that the resistance was as low as 2 × 10 ⁻⁴ Ω · cm.

Next, when a voltage of 8 V was applied using the ITO thin film as an anode and the amorphous transparent conductive film as a cathode,
The current density became 3.0 mA / cm ² , and light emission of 80 Cd / m ² was observed from the amorphous transparent conductive film side. Light emission was green light emitted from Alq. Furthermore, when this device was left in the atmosphere of 70% RH in the air for 100 hours, no light emitting point was observed with the naked eye, the luminous efficiency of the device did not decrease, and the luminous performance was maintained.

Example 3 <Preparation of Organic EL Device> A glass substrate with an ITO thin film similar to that used in Example 1 was mounted on a substrate holder in a vacuum evaporation apparatus in the same manner as in Example 1, and the × 10
^The pressure was reduced to ^-4 Pa. In addition, 200 mg each of CuPc, TPD, and Alq was put in the resistance heating boat of the vacuum evaporation apparatus, and an aluminum-lithium alloy (Li content: 2% by weight) was put in the resistance heating filament.

First, CuPc was deposited on a glass substrate with an ITO thin film at 25 nm, TPD was deposited at 40 nm, and Alq was deposited at 60 nm. Next, a mask was placed on the formed laminate, and magnesium (Mg) as an electron injecting metal was simultaneously deposited at a deposition rate of 1.4 nm / sec and Alq as an electron transporting compound at 0.1 nm / sec. Vapor deposition was performed to form a mixed electron injection electrode layer having a thickness of 10 nm.

Next, the substrate was transferred and set to a substrate holder in another vacuum chamber connected to the above-mentioned vacuum deposition apparatus.
During this period, the degree of vacuum is maintained. The above-mentioned another vacuum chamber is formed by DC magnetron sputtering.
Equipment is provided so that a Zn—O-based oxide film can be formed. The target for forming the In—Zn—O-based oxide film is a sintered body composed of In ₂ O ₃ and ZnO, and the atomic ratio of In [In / (In + Zn)] is 0.84.
It is. A mixed gas of argon gas and oxygen gas (volume ratio: 1000: 5.0) in this vacuum chamber was introduced until the pressure became 3 × 10 ⁻¹ Pa, the sputtering output was set to 1 W / cm ² , and the substrate temperature was set to room temperature. Thus, an amorphous transparent conductive film having a thickness of 200 nm was formed. Note that the fact that the In—Zn—O-based oxide film was amorphous was confirmed by X-ray diffraction using a glass substrate on which an ITO thin film had not been deposited by forming a laminate in the same manner as described above. .

<Evaluation of Organic EL Element> When the sheet resistance of the amorphous transparent conductive film formed by this manufacturing method was examined in the same manner as in Example 1, it was 20 Ω / □.
Since the film thickness is 200 nm, the specific resistance is 4.
It was confirmed that the resistance was as low as 0 × 10 ⁻⁴ Ω · cm.

Next, when a voltage of 8 V was applied using the ITO thin film as an anode and the amorphous transparent conductive film as a cathode,
The current density was 2.9 mA / cm ² , and when observed from the side of the amorphous transparent conductive film, light emission was 60 Cd / m ² . Light emission was green light emitted from Alq. Furthermore, when this device was left in the atmosphere of 70% RH in the air for 100 hours, no light emitting point was observed with the naked eye, the luminous efficiency of the device did not decrease, and the luminous performance was maintained.

Example 4 <Preparation of Organic EL Element> A glass substrate with an ITO thin film similar to that used in Example 1 was mounted on a substrate holder in a vacuum evaporation apparatus in the same manner as in Example 1, and the × 10
^The pressure was reduced to ^-4 Pa. In addition, 200 mg each of CuPc, TPD, and Alq was put in the resistance heating boat of the vacuum evaporation apparatus, and an aluminum-lithium alloy (Li content: 2% by weight) was put in the resistance heating filament.

First, CuPc was deposited on a glass substrate with an ITO thin film to a thickness of 25 nm, TPD was deposited to a thickness of 40 nm, and Alq was deposited to a thickness of 60 nm. Next, a mask was placed on the formed laminate, and an Al—Li alloy was deposited to a thickness of 2 nm. However, in this embodiment, the electron injection electrode layer was formed by vapor deposition so as to be discontinuous in an island shape.

Next, the substrate was transferred and set to a substrate holder in another vacuum chamber connected to the above-mentioned vacuum deposition apparatus.
During this period, the degree of vacuum is maintained. The above-mentioned another vacuum chamber is formed by DC magnetron sputtering.
Equipment is provided so that a Zn—O-based oxide film can be formed. The target for forming the In—Zn—O-based oxide film is a sintered body composed of In ₂ O ₃ and ZnO, and the atomic ratio of In [In / (In + Zn)] is 0.84.
It is. A mixed gas of argon gas and oxygen gas (volume ratio: 1000: 5.0) in this vacuum chamber was introduced until the pressure became 3 × 10 ⁻¹ Pa, the sputtering output was set to 1 W / cm ² , and the substrate temperature was set to room temperature. Thus, an amorphous transparent conductive film having a thickness of 200 nm was formed. Note that the fact that the In—Zn—O-based oxide film was amorphous was confirmed by X-ray diffraction using a glass substrate on which an ITO thin film had not been deposited by forming a laminate in the same manner as described above. .

Regarding the formation of the island-like electron injection region,
In the above-described method for producing an EL element, a laminate was stopped separately at the stage when the Al-Li alloy was vapor-deposited, and it was confirmed by a scanning electron microscope that the layer was vapor-deposited in an island shape.

<Evaluation of Organic EL Device> The sheet resistance of the amorphous transparent conductive film formed by the manufacturing method of the above embodiment was measured in the same manner as in Example 1, and was found to be 15 Ω / □. Since the film thickness was 200 nm, it was confirmed that the specific resistance was as low as 3.0 × 10 ⁻⁴ Ω · cm.

Next, when a voltage of 8 V was applied using the ITO thin film as an anode and the amorphous transparent conductive film as a cathode,
The current density became 3.8 mA / cm ² , and when observed from the side of the amorphous transparent conductive film, light emission of 65 Cd / m ² was observed. Light emission was green light emitted from Alq. Furthermore, when this device was left in the atmosphere of 70% RH in the air for 100 hours, no light emitting point was observed with the naked eye, the luminous efficiency of the device did not decrease, and the luminous performance was maintained.

[0083]

Since the organic EL device of the present invention has a cathode having low resistance and high transparency, light can be efficiently extracted from both sides of the device. Also, it has excellent durability. For this reason, the organic EL element of the present invention is suitably used, for example, for displays of information equipment.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an example of an organic EL device of the present invention.

FIG. 2 is a cross-sectional view illustrating an example of a configuration in which an island-shaped electron injection region is present at an interface between an amorphous transparent conductive film and an organic layer in the organic EL device of the present invention.

FIG. 3 is a simplified cross-sectional view showing an example of a use mode of the organic EL element of the present invention, showing a configuration in which a color filter is added outside an amorphous transparent conductive film.

FIG. 4 is a simplified cross-sectional view showing an example of a use mode of the organic EL element of the present invention, showing a configuration in which a black absorbing layer is provided outside an amorphous transparent conductive film.

FIG. 5 is a cross-sectional view showing a simplified example of a use mode of the organic EL element of the present invention, and showing a configuration provided with a background color forming layer outside a transparent anode.

[Explanation of symbols]

 1: substrate 2: anode 3: organic layer 4: electron injection electrode layer 5: amorphous transparent conductive film 6: island-like injection region 7: color filter 8: black light absorbing layer 9: background color forming layer

Claims (5)

[Claims] 1. An organic electroluminescence device having an organic layer including an organic light emitting layer interposed between an anode and a cathode, wherein the cathode comprises an electron injection electrode layer and an amorphous transparent conductive film, An organic electroluminescence device, wherein the electron injection electrode layer is in contact with the organic layer. 2. An electron injection electrode layer comprising: an electron injection metal;
2. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is formed in an ultra-thin film using one or more selected from alloys and alkaline earth metal oxides. 3. An electron injection electrode layer comprising: an electron injection metal;
2. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is a mixed layer of one or more selected from alloys and alkaline earth metal oxides and an electron-transporting organic substance. 4. The organic electroluminescence device according to claim 1, wherein the electron injection electrode layer comprises an island-shaped electron injection region. 5. An amorphous transparent conductive film is made of indium (I)
The organic electroluminescence device according to any one of claims 1 to 4, wherein the organic electroluminescence device is formed using an oxide composed of n), zinc (Zn), and oxygen (O).