JPH0790260A - Organic electroluminescent device - Google Patents

Abstract

(57) [Summary] [Structure] In the first organic electroluminescence device, a hole-transporting light-emitting layer 1 in which a dye is molecularly dispersed is laminated with an electron-transporting layer 2. The electron transport layer 2 preferably contains the triazole derivative of the formula (1). The second element is the above formula (1)
Of a triazole derivative of In the third device, a layer of the triazole derivative represented by the above formula (1) was interposed between the electron transport layer and the hole transport layer. [Chemical 1] (The symbols in the formula are as described in the specification.) [Effect] Such an organic electroluminescence device has excellent luminous efficiency, luminous brightness, and stability, and emits blue light.
It is capable of multi-color light emission of three primary colors and white light emission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (EL) device.

[0002]

2. Description of the Related Art In light emission of an organic electroluminescence device, holes and electrons injected from electrodes recombine in a light emitting layer to generate excitons, which excite molecules of a light emitting material forming the light emitting layer. It is believed to be based on that.
Then, when a fluorescent dye is used as the light emitting material, an emission spectrum equivalent to the photoluminescence of the dye molecule can be obtained as electroluminescence emission.

Recently, an element having two layers, a hole transporting layer and an electron transporting light emitting layer, which efficiently emits green light at a voltage as low as about 10 V, as compared with a conventional organic electroluminescent element having a single layer structure, has been developed. Proposed by Tang and Vanslyke [CW Tang and SAVanSlyke; Appl.Phys.Lett.,
51 (1987) 913]. The device is composed of an anode, a hole transport layer, an electron transport light emitting layer, and a cathode formed on a glass substrate.

In the above device, the hole transporting layer functions to inject holes from the anode into the electron transporting light emitting layer, and prevents the electrons injected from the cathode from escaping to the anode without being recombined with the holes. It also plays the role of confining electrons in the electron-transporting light-emitting layer. Therefore, due to the electron confinement effect of the hole transport layer, recombination of holes and electrons occurs more efficiently than in the conventional device having a single-layer structure, and the driving voltage can be significantly reduced.

Saito et al.
It has been shown that not only the electron transport layer but also the hole transport layer can be the light emitting layer [C. Adachi, T. Tsutsui and S. Saito;
Pl.Phys.Lett., 55 (1989) 1489], proposed a three-layer organic electroluminescent device in which an organic light emitting layer is sandwiched between a hole transport layer and an electron transport layer [C. Adachi, ST.
okito, T.Tsutsui and S.Saito; Jpn.J.Appl.Phys., 27
(1988) L269].

The two-layer structure element of Saito et al. Consists of an anode, a hole-transporting light-emitting layer, an electron-transporting layer, and a cathode formed on a glass substrate. Contrary to the above, the electron-transporting layer is from the cathode to the holes. It not only functions to inject electrons into the transporting light-emitting layer, but also prevents holes injected from the anode from escaping to the cathode without recombining with the electrons, and also plays a role in confining holes in the hole-transporting light-emitting layer. . Therefore, due to the hole confinement effect of this electron transport layer, the driving voltage can be drastically reduced as in the previous case.

The element of Saito et al. Has a three-layer structure,
These devices are further improved and consist of an anode formed on a glass substrate, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode.The hole transport layer functions to confine electrons in the light emitting layer and to transport electrons. Since the layer functions to confine holes in the light emitting layer, the recombination efficiency of electrons and holes in the light emitting layer is further improved as compared with the two-layer structure.
Further, the electron transport layer and the hole transport layer also have a function of preventing excitons generated by recombination of electrons and holes from escaping to any of the positive and negative electrodes and being quenched. Therefore, according to the three-layer structure element proposed by Saito et al., The luminous efficiency is further improved.

Aromatic tertiary amines such as triphenylamine are used as hole transport materials constituting these organic electroluminescent devices, oxadiazoles are used as electron transport materials, and tetraphenylbutadiene derivatives and tris () are used as light emitting materials. 8-quinolinolato) aluminum (III) complex, distyrylbenzene derivative, distyrylbiphenyl derivative and the like are known.

The above-described organic electroluminescent device is capable of emitting light with high brightness at a low voltage as compared with the conventional electroluminescent device using an inorganic light emitting material, and it is possible to use not only the vapor deposition method but also the solution coating method. Although each layer can be formed, it is easy to increase the area, and it is possible to make multiple colors by designing the molecular weight of organic molecules. There are problems, and improvement of stability and prolongation of life are major issues.

In addition, there is a problem that it is difficult for the conventional electroluminescence device currently known to emit blue light regardless of whether it is organic, inorganic, single-layer or multi-layer. In the case of inorganic devices, for example, inorganic light-emitting materials with a wide bandgap required for blue light emission are limited, and such materials often involve technical difficulties in crystal growth and thin film fabrication, so they should be made into devices. Is difficult.

On the other hand, although it has been described above that organic materials can be multicolored by molecular design, there are few materials capable of emitting blue light, and anthracene and distyrylbenzene derivatives, which have insufficient luminous efficiency, are known. However, it is far from being put to practical use. In addition, the conventional electroluminescence elements each emit only a single color of light, and are capable of performing multicolor display by the three primary colors of R (red), G (green), and B (blue) and white light emission. At present, it is impossible to realize the light emission of the above different spectra with one element.

In order to solve this problem, Ogura et al.
Bis-di (p- as a diamine derivative in the hole transport layer
Toluyl) aminophenyl-1,1-cyclohexane,
1, as a tetraphenyl butadiene derivative in the light emitting layer
1-di (p-methoxyphenyl) -4,4-diphenylbutadiene, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3 as an oxadiazole derivative in the electron transport layer Proposed a three-layer device using 1,4-oxadiazole [Sharp Technical Report, 52 (3)
, 15-18 (1992)].

This device has emission spectrum peaks at wavelengths of 480 nm and 590 nm and emits white light. Wavelength 4
Light having a wavelength of 80 nm is caused by the light emitting layer having a hole transporting property, and light having a wavelength of 590 nm is caused by the hole transporting layer.
Ogura et al. Explain the mechanism of light emission from the hole transport layer due to exciton diffusion from the light emitting layer. Mori et al.
Polymer poly-N- that doubles as hole transport material and binder resin
An organic electroluminescence device having a single light emitting layer, in which a light emitting material such as coumarin 6 or coumarin 7 known as a laser dye and an oxadiazole derivative as an electron transporting material are molecularly dispersed in vinylcarbazole. In his proposal, he reported that he could emit light of various colors by selecting the kind of dye to be molecularly dispersed in the light emitting layer [Applied Physics, 61 (10), 1044
~ 1047 (1992)].

In this device, depending on the kind and combination of dyes to be molecularly dispersed in the light emitting layer, R,
There is a possibility that multi-color display by the three primary colors of G and B and white light emission can be realized.

[0015]

However, in the former device having a three-layer structure, the emission intensity during use is greatly reduced, and improvement in stability is a major problem. One of the causes of this is deterioration of the material due to heat generated when the device emits light.
Aggregation, crystallization, etc. are considered. The latter element has a single-layer structure, so that the recombination efficiency of holes and electrons is not high and the emission luminance is low.

An object of the present invention is to provide an organic electroluminescence device which is excellent in luminous efficiency, luminous brightness and stability. Another object of the present invention is to emit light of a color such as blue light emission, which could not be sufficiently emitted or could not be emitted in the past.
An object of the present invention is to provide an organic electroluminescence device that can be obtained with high luminous efficiency. Still another object of the present invention is that it is possible to emit light of two or more emission spectra different from each other, and multi-color display by three primary colors, white light emission, etc. can not be obtained or sufficient light emission efficiency can be obtained conventionally. An object of the present invention is to provide an organic electroluminescence device capable of obtaining undesired color light emission with high light emission efficiency.

[0017]

The first organic electroluminescent device of the present invention comprises at least an electron transporting layer and a hole transporting light emitting layer, and the hole transporting light emitting layer is at least one kind. The dye is characterized by being dispersed in a polymer.

In the organic electroluminescence device of the present invention having the above-mentioned constitution, since the hole transporting light emitting layer is constituted by dispersing at least one kind of dye in a polymer, a conventional low molecular weight material is used. It has excellent heat resistance as compared with a hole transport layer made of, and also has excellent adhesion to substrates such as ITO glass and ITO film. Therefore, it is possible to form a hole-transporting light-emitting layer in which deterioration, aggregation, crystallization and the like due to heat generation during light emission of the element are unlikely to occur, and the stability of the element can be improved. In addition, by combining this hole-transporting light-emitting layer with an electron-transporting layer, the carrier injection efficiency and the hole-electron recombination efficiency are improved compared to the conventional single layer, so that high efficiency and high brightness are achieved. Can be emitted. Moreover, depending on the type and combination of the dyes, multicolor display with high color purity by the three primary colors of R, G, B, white light emission, natural light emission, etc. can be realized.

In the first organic electroluminescence device, the electron transport layer is composed of a layer of 1,2,4-triazole derivative alone, or 1,2,4-.
It is preferably composed of two layers, a layer of a triazole derivative and a layer of a tris (8-quinolinolato) aluminum (III) complex. Such electron transport layers are 1, 2, 4
-The triazole derivative not only has a good electron-transporting property but also exhibits a hole-blocking property that prevents the passage of holes, so that in the hole-transporting light-emitting layer, recombination of electrons and holes can be efficiently performed, and The generated excitons can be efficiently contained in the hole-transporting light-emitting layer, and the light-emitting efficiency and emission brightness of the hole-transporting light-emitting layer can be further improved.

The above 1,2,4-triazole derivative has the formula (2):

[0021]

[Chemical 2]

3- (4-biphenylyl) -represented by
4-phenyl-5- (4-tert-butylphenyl)-
1,2,4-triazole (hereinafter referred to as "TAZ0")
Although various compounds such as
(1):

[0023]

[Chemical 3]

(Wherein R ¹ , R ² , R ³ , R ⁴ and R
⁵ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxyl group, an aryl group or an aralkyl group.
However, the groups R ¹ , R ² , R ³ , R ⁴ and R ⁵ are not hydrogen atoms at the same time. 1,2,4-triazole derivative (hereinafter referred to as "s-TAZ") is preferably used.

The s-TAZ has excellent thin film forming properties by the vapor deposition method or the solution coating method, and can form a thin film of good film quality without pinholes. Furthermore, there is an advantage that an electron transport layer having an excellent hole blocking property can be formed.
Further, the electron transport layer needs to have a smooth surface in terms of the efficiency of injecting electrons into the hole transporting light emitting layer.
Since TAZ is less likely to aggregate or crystallize than TAZ0, this thin film made of s-TAZ has little surface irregularity change over time, has excellent thermal stability, and dramatically improves the life of the device. There is also an advantage that you can.

The second organic electroluminescent device of the present invention is characterized by including at least an s-TAZ layer represented by the general formula (1). Since the organic electroluminescent device of the present invention is provided with the s-TAZ layer exhibiting good electron transporting property and hole blocking property as described above, the coupling efficiency of electrons and holes can be further improved as compared with the conventional one. Since the excitons generated by the recombination of the can be efficiently contained in the light emitting layer, it is very effective in improving the light emitting efficiency and the light emitting brightness of the light emitting layer and the stability associated therewith. In particular, when combined with a conventional blue light emitting layer that has a high hole transporting property, its luminous efficiency and luminous brightness are
Since it can be improved to a practically sufficient range, it is also possible to realize blue light emission with high brightness, which has been difficult to put into practical use in the past. In addition, since the s-TAZ layer has less surface irregularities over time as described above and is excellent in thermal stability, the life of the device can be dramatically improved.

Further, the third organic electroluminescence device of the present invention comprises a hole transport layer and an electron transport layer, and between the layers, s-TAZ represented by the general formula (1) is used. In addition, a carrier transport control layer that selectively transports at least one of holes and electrons is interposed. In the organic electroluminescent element of the present invention, the above-mentioned s
Due to the exciton confinement effect of the carrier transport control layer made of -TAZ, the hole transport layer or the electron transport layer can be used as a light emitting layer to emit light with high brightness and high efficiency. In addition to being able to improve, the luminous efficiency and luminous brightness of blue light emission can be improved to a practical range.

By selecting the film thickness of the carrier transport control layer, one or both of the hole transport layer and the electron transport layer can emit light with high brightness and high efficiency. By using materials having emission spectra different from each other for the electron transport layer, one device can emit two or more emission spectra different from each other, which is impossible in the past. Therefore, there is a possibility that the multicolor display and the light emission such as white light emission can be put to practical use.

In addition, the carrier transport control layer made of s-TAZ has little change in surface irregularities over time and has excellent thermal stability, so that the life of the device can be dramatically improved. As described above, according to the first to third organic electroluminescence elements of the present invention, not only excellent luminous efficiency, luminous brightness and stability, but also sufficient luminous efficiency such as blue light emission cannot be obtained conventionally. It becomes possible to obtain light emission of a color that could not be emitted with high light emission efficiency. Furthermore, according to the organic electroluminescence elements of these inventions, it is possible to emit light of two or more emission spectra different from each other, and it has been impossible to obtain sufficient light emission efficiency in the past such as multicolor display by three primary colors or white light emission or light emission. It is also possible to obtain light emission of a color that could not be achieved with high light emission efficiency.

The present invention will be described below. First, of the present invention, a first organic electroluminescent device, which is characterized in that at least one kind of dye is molecularly dispersed in a polymer to form a hole transporting light emitting layer, will be described. As the polymer constituting the hole-transporting light-emitting layer, either one having carrier transportability itself or one not having carrier transportability may be adopted. In the case of using a polymer that does not have carrier transportability by itself, a low molecular weight hole transport material may be molecularly dispersed together with the dye to impart hole transportability.

Examples of the former polymer having carrier transporting property include polyphenylene vinylene and its derivatives, polyalkylthiophene and poly-N-.
Examples thereof include vinylcarbazole, polymethylphenylsilane, and polymers having a triphenylamine group in the side chain or main chain. Especially, the following formula (3):

[0032]

[Chemical 4]

Poly-N-vinylcarbazole represented by [wherein n represents the degree of polymerization] (hereinafter referred to as "PVK")
Is most preferably used because it has a stable carrier transporting property. The degree of polymerization n of PVK is not particularly limited, but is preferably about 20 to 5000. Degree of polymerization n
Is less than the above range, heat resistance and adhesiveness may be insufficient, and conversely, if it is more than the above range, it may be difficult to form a layer by a solution coating method described later.

As the latter polymer having no carrier transporting property, various polymers having excellent optical properties such as polymethylmethacrylate, polycarbonate and polystyrene can be used. As the dye that is molecularly dispersed in the polymer, various dyes that can emit fluorescence when excited by excitons, such as the above-described laser dye, can be used. Examples of the dyes include cyanine dyes, xanthene dyes, oxazine dyes, coumarin derivatives, perylene derivatives, acridine dyes, acridone dyes and quinoline dyes. Specifically, the following formula (4):

[0035]

[Chemical 5]

Tetraphenylbutadiene represented by the formula (blue emission, hereinafter referred to as "TPB"), the following formula (5):

[0037]

[Chemical 6]

Coumarin 6 (green emission) represented by the following formula (6):

[0039]

[Chemical 7]

Coumarin 7, represented by the following formula (7):

[0041]

[Chemical 8]

4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (orange emission, hereinafter referred to as "DCM") and the like are preferably used. In the case of white light emission, TP of the above formula (4)
A combination of B, coumarin 6 of formula (5) and DCM of formula (7) is preferably employed. According to the above combination,
The emission spectrum of the hole-transporting light-emitting layer has a wavelength of 400 to
It covers the entire visible light region of 700 nm and exhibits excellent white light emission.

The mixing ratio of the dye in the polymer is not particularly limited in the present invention, and a preferable range is appropriately set depending on the types of the polymer and the dye, the emission intensity and the color tone. When the polymer does not have a carrier transporting property, examples of the low molecular weight hole transporting material that is molecularly dispersed in the polymer include triphenylamine derivatives and the like. Among them, the following formula (8):

[0044]

[Chemical 9]

N, N'-diphenyl-N, represented by
N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4-diamine (hereinafter referred to as "TPD") is preferably used. The hole-transporting light-emitting layer consisting of the above components is a solution in which a material such as a polymer or a dye forming the layer is dissolved in a suitable solvent, and the coating solution is applied onto a substrate or another layer and dried. It is formed by a coating method.

As the electron-transporting layer combined with the hole-transporting light-emitting layer, layers made of various publicly known electron-transporting materials can be adopted. Particularly, a layer of 1,2,4-triazole derivative or 1,2,4-triazole derivative is preferable. A layer of a 4,4-triazole derivative and the following formula (9):

[0047]

[Chemical 10]

Tris (8-quinolinolato) represented by
A layer having a two-layer structure in which layers of aluminum (III) complex (hereinafter referred to as "Alq") are laminated is suitably used as the electron transport layer. The 1,2,4-triazole derivative not only has a good electron-transporting property but also exhibits a hole-blocking property that prevents the passage of holes, so that the recombination of electrons and holes is efficiently performed in the hole-transporting light-emitting layer. The exciton generated can be efficiently encapsulated in the hole-transporting light-emitting layer, and the light-emitting efficiency and emission brightness of the hole-transporting light-emitting layer can be further improved.

As the above 1,2,4-triazole derivative, various compounds can be used, and TAZ0 represented by the above formula (2) is generally used from the viewpoints of synthesis and availability. However, as described above, the following general formula (1):

[0050]

[Chemical 11]

(Wherein R ¹ , R ² , R ³ , R ⁴ and R
⁵ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxyl group, an aryl group or an aralkyl group.
However, the groups R ¹ , R ² , R ³ , R ⁴ and R ⁵ are not hydrogen atoms at the same time. S-TAZ represented by) is most preferably used in the present invention.

The substitution position and the number of substitutions of the substituent in s-TAZ are not particularly limited, but in view of easiness of synthesis, any one of the groups R ² , R ³ and R ⁴ is more preferable than the groups R ¹ and R ⁵ . Substituents are preferably substituted, and the total number of substitutions in that case may be mono (1 substitution), di (2 substitutions) or tri (3 substitutions). Further, in the case of a small group such as a lower alkyl group, the groups R ¹ and R ⁵ may be substituted, and in this case, the total number of substitutions may be 1 to 5 substitutions.

Examples of the alkyl group corresponding to the groups R ^{1 to} R ⁵ include, but are not limited to, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, Examples thereof include alkyl groups having 1 to 10 carbon atoms such as tert-butyl group, pentyl group and hexyl group, with methyl group and ethyl group being particularly preferred. Examples of the alkoxyl group include carbon number such as methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, iso-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group. Examples thereof include alkoxyl groups of 1 to 10, and methoxy group and ethoxy group are particularly preferable.

Further, as the aryl group, for example, phenyl group, tolyl group, xylyl group, biphenylyl group, o-
Examples thereof include a terphenyl group, a naphthyl group, an anthryl group and a phenanthryl group. Examples of the aralkyl group include benzyl group, α-phenethyl group, β-phenethyl group, 3-phenylpropyl group, benzhydryl group and trityl group.

Specific examples of s-TAZ include, but are not limited to, formula (1a):

[0056]

[Chemical 12]

3- (4-biphenylyl) -represented by:
4- (4-ethylphenyl) -5- (4-tert-butylphenyl) -1,2,4-triazole (hereinafter "s-T
AZ1 ”) and the formula (1b):

[0058]

[Chemical 13]

3- (4-biphenylyl) -represented by
4- (3-ethylphenyl) -5- (4-tert-butylphenyl) -1,2,4-triazole (hereinafter "s-T
AZ2 ”) and the like. The thickness of the layer made of the 1,2,4-triazole derivative is not particularly limited in the present invention, but if the thickness of the layer is too thin, the hole blocking property becomes insufficient. Thick is desirable.

Of the layer of 1,2,4-triazole derivative,
The preferred film thickness range is not particularly limited, but for example, in the case of the vapor deposition film of TAZ0 represented by the above formula (2), the film thickness is 100 to 200Å or more in order to secure sufficient hole blocking property. Is preferred. The above T
The upper limit range of the vapor-deposited film of AZ0 is not particularly limited, however, if the film thickness is too thick, the electron transporting property is deteriorated, so the film thickness is preferably 1000 Å or less.

On the other hand, the layer composed of s-TAZ represented by the general formula (1) is more excellent in hole blocking property than the layer composed of TAZ0 as described above.
The film thickness can be made thinner than the case of 0. The suitable film thickness range is not particularly limited, but for example, s
In the case of a vapor-deposited film of -TAZ, the film thickness is preferably 100 to 150 Å or more in order to secure sufficient hole blocking property. The upper limit of the film thickness of the vapor-deposited film of s-TAZ is not particularly limited, but if the film thickness is too thick, the electron transporting property is lowered, so the film thickness is 100.
It is preferably 0 Å or less.

When the 1,2,4-triazole derivative layer is combined with the Alq layer represented by the above formula (9), the electron injection property to the hole transporting light emitting layer is further improved. Further, it is possible to obtain an element having higher luminous efficiency and higher luminous brightness. Although the film thickness of the Alq layer is not particularly limited, the film thickness of the layer is 100 when the electron injection property and the electron transport property to the hole transporting light emitting layer are taken into consideration.
It is preferably about 1000 Å. When laminating Alq layers, the thickness of the 1,2,4-triazole derivative layer is increased because the Alq layer acts to assist the hole blocking property of the 1,2,4-triazole derivative layer. May be below the preferred range described above.

Further, the total film thickness of both layers is not particularly limited, but is preferably about 200 to 1500Å. If the film thickness is smaller than this range, the hole blocking property may be insufficient, and conversely, if the film thickness is larger than this range, the electron transporting property may be deteriorated. Above 1,
The electron transport layer such as the layer of the 2,4-triazole derivative and the layer of Alq may be composed of only the electron transport material such as the above 1,2,4-triazole derivative and Alq.
Alternatively, the electron transport material may be dispersed in a suitable binder. Further, the electron transport layer may contain other components such as various additives which do not impair the function of the electron transport material.

The electron transport layer can be formed by a vapor phase growth method such as a vacuum vapor deposition method, or a coating solution prepared by dissolving a material constituting the layer in an appropriate solvent is coated on a substrate or another layer and dried. It can also be formed by a solution coating method.
The order of stacking the layers of the first organic electroluminescent element of the present invention including the above layers is not particularly limited.

However, as described above, the polymer constituting the hole-transporting light-emitting layer has excellent adhesion to a substrate such as ITO glass or ITO film, and the hole-transporting light-emitting layer is exclusively a solution. Considering that it is formed by a coating method, etc., as shown in FIGS. 1A and 1B, ITO (Indium-tin-
On the anode 40 made of a transparent conductive material such as oxide),
It is preferable that two layers of the hole transporting light emitting layer 1 and the electron transporting layer 2 are laminated in this order.

The electron transport layer 2 shown in FIG.
A two-layer structure in which two layers of a triazole derivative layer (TAZ layer) 21 and an Alq layer 22 are laminated in this order on the hole-transporting light-emitting layer 1. In both figures above, reference numeral 5 is Mg
/ Ag is a cathode made of a metal vapor deposition film, and B is a power source for applying a driving voltage to the device.

Next, of the present invention, a second organic electroluminescent device, which is characterized by comprising at least the s-TAZ layer represented by the general formula (1), will be described. The term "s-TAZ layer" as used herein refers to a layer containing at least one or two or more of the above-mentioned s-TAZ, and a layer formed of only one or two or more species of s-TAZ, or a suitable layer. An example is one in which one or more s-TAZ are dispersed in a binder. The layer of s-TAZ contains s-TA containing various additives.
It may contain other components which do not inhibit the function of Z.

The s-TAZ layer can be formed by a vapor phase growth method such as a vacuum vapor deposition method, or a coating solution prepared by dissolving a material forming the layer in an appropriate solvent is applied on a substrate or another layer. It can also be formed by a solution coating method of drying after drying. The thickness of the s-TAZ layer is not particularly limited in the present invention. However, if the film thickness of the above layer is too thin, the hole blocking property becomes insufficient, so it is desirable that the film thickness of the layer be somewhat thick. of the s-TAZ layer,
The suitable film thickness range is not particularly limited, but in the case of a vapor-deposited film of s-TAZ, for example, the film thickness is preferably 100 to 150 Å or more in order to secure a sufficient hole blocking property. The upper limit of the film thickness of the vapor-deposited film of s-TAZ is not particularly limited, but if the film thickness is too thick, the electron transporting property is deteriorated, so the film thickness is preferably 1000 Å or less.

The organic electroluminescence device of the present invention is not particularly limited in other constitutions as long as it has the above-mentioned s-TAZ layer, and may have a conventional single-layer structure or a multilayer structure of two or more layers. It may be a structure. In short, the structure of the present invention can be applied to devices having various layer structures. When the device has a multi-layer structure, s-T
The material constituting the layers other than the AZ layer is not particularly limited in the present invention, and various materials conventionally used for each layer can be used. The thickness of each layer forming the element is not particularly limited in the present invention. Like each layer of s-TAZ, each layer can be formed by a vapor phase growth method such as a vacuum vapor deposition method, or a coating solution obtained by dissolving a material forming the layer in an appropriate solvent is formed on a substrate or another layer. It can also be formed by a solution coating method of coating and drying.
Further, each of the above layers may contain other components such as a binder resin and various additives, which are not directly related to the function of the layer.

In the organic electroluminescence device of the present invention, since the s-TAZ layer exhibits excellent electron transporting property and hole blocking property as described above,
By combining the TAZ layer as an electron transport layer with a hole transporting light emitting layer for emitting blue light having a high hole transporting property as described above, it is possible to realize blue light emission with high brightness, which has been difficult to put into practical use in the past. It is possible. Also, the above s-
As described above, the TAZ layer has little change in surface irregularities over time and is excellent in thermal stability, so that the life of the device can be dramatically improved.

Above all, PV represented by the above formula (3)
The layer K is suitable as a blue light emitting hole transporting light emitting layer. Since the PVK layer has a high hole mobility and injected holes escape to the cathode side, it is usually difficult to emit light, but this PVK layer has the exciton confinement effect as described above. Excellent, when combined with a layer of s-TAZ having a high hole blocking property, blue light can be emitted.

The PVK also has a function as a hole transport material as can be seen from its molecular structure, and since it is a polymer, it is a conventional hole transport material such as the low molecular weight aromatic tertiary amine compound. It has excellent heat resistance as compared with, and it is possible to form a hole-transporting light-emitting layer that emits blue light and is less likely to be deteriorated or crystallized due to heat generation during storage or light emission of the device.

Moreover, the PVK layer is made of ITO glass or IT.
Excellent adhesion to substrates such as O film. Therefore, the above PVK layer is used as a hole transporting light emitting layer, and s-
When combined with a TAZ layer, a blue light emitting organic electroluminescence device having excellent light emission efficiency, high light emission brightness, and excellent stability can be formed.

The degree of polymerization n of PVK is not particularly limited in the present invention, but is preferably about 20 to 5,000. If the degree of polymerization n is less than the above range, heat resistance and adhesiveness may be insufficient. On the contrary, if the degree of polymerization n is more than the above range, it may be difficult to form a layer by a solution coating method described later. is there. As a further preferred example of the device in which the s-TAZ layer and the PVK layer (hole transporting light emitting layer) are combined, an Alq layer represented by the formula (9) is combined as an electron transport layer, An example is a three-layer structure. In this organic electroluminescent device having a three-layer structure, the function of the Alq layer further improves the electron injection property into the hole-transporting light-emitting layer, and more efficient blue light emission with high emission brightness is obtained. .

The layer structure of the element having the three-layer structure is not particularly limited. However, as described above, considering that the PVK layer has excellent adhesion to a substrate such as ITO glass or ITO film, and that the PVK layer is formed exclusively by a solution coating method, As shown in FIG. 2 (a), the IT formed on the surface of the glass substrate 4 or the like.
A hole-transporting light-emitting layer (PVK) is formed on the anode 40 made of a transparent conductive material such as O (indium-tin-oxide).
Layer) 1, s-TAZ layer 20 and electron transport layer (Alq
It is preferable that three layers of Layer 3 are laminated in this order. In the figure, reference numeral 5 is a cathode made of a metal vapor deposition film of Mg / Ag or the like, and B is a power source for applying a drive voltage to the element, as in the case of FIGS.

The film thicknesses of the PVK layer 1 and the Alq layer 3 are not particularly limited in the present invention, and if the optimum film thickness range is set according to the type of s-TAZ to be combined and the film thickness of the layer. Good. The PVK layer 1 is the PVK that constitutes the layer.
Since it is a polymer, it is mainly formed by a solution coating method in which a coating liquid prepared by dissolving a material containing PVK in a suitable solvent is coated on a substrate or another layer and dried as described above.

On the other hand, the Alq layer 3 is a layer containing at least Alq, and examples thereof include a layer formed of only Alq, and a layer in which Alq is dispersed in a suitable binder. The Alq layer 3 can be formed by a vapor phase growth method such as a vacuum vapor deposition method, or a solution in which a coating solution in which a material forming the layer is dissolved in a suitable solvent is applied on a substrate or another layer and dried. It can also be formed by a coating method.

The PVK layer 1 and the Alq layer 3 are
Each may contain other components such as various additives that do not inhibit the functions of PVK and Alq. Next, among the present invention, between the hole transport layer and the electron transport layer,
A third organic electroluminescence device having a three-layer structure in which a carrier transport control layer made of s-TAZ represented by (1) is interposed will be described.

The organic electroluminescence device of the present invention is provided with a glass substrate 4 as shown in FIG. 2 (b), for example.
Three layers of the hole transport layer 10, the carrier transport control layer 23 made of s-TAZ and the electron transport layer 3 on the anode 40 made of a transparent conductive material such as ITO (indium-tin-oxide) formed on the surface of the. It is configured by stacking. The order of forming the three layers may be reversed. In short, the carrier transport control layer 23 made of s-TAZ may be interposed between the hole transport layer 10 and the electron transport layer 3.
In the figure, reference numeral 5 indicates Mg as in the case of the previous figures.
/ Ag is a cathode made of a metal vapor deposition film, and B is a power source for applying a driving voltage to the device.

The carrier transport control layer 23 made of s-TAZ as used herein means a layer containing at least s-TAZ. In addition to a layer made of only s-TAZ, s-TAZ is added to an appropriate binder. Examples include dispersed materials. The s-TAZ layer can be formed by a vapor phase growth method such as a vacuum vapor deposition method, or a coating solution in which a material forming the layer is dissolved in a suitable solvent is coated on a substrate or another layer and dried. It can also be formed by a solution coating method.
Further, the carrier transport control layer 23 made of s-TAZ described above.
May contain other components such as various additives that do not inhibit the function of s-TAZ.

The carrier transport control layer 23 made of s-TAZ can be formed by selecting the material or the film thickness of the carrier transport control layer 23 as described above, so that either or both of the hole transport layer 10 and the electron transport layer 3 can be formed. It works to emit light with high brightness and high efficiency. Carrier transport control layer 2 comprising s-TAZ
3 has the function of s-T as the carrier transport control layer 23.
The vapor deposition film of AZ (s-TAZ layer) is used, and the vapor deposition film of TPD represented by the above formula (8) (T
PD layer), and as the electron transport layer 3, the above formula is used.
The case of using the Alq vapor deposition film (Alq layer) represented by (9) will be described below as an example.

Generally, the injection of carriers into the organic insulating film is limited by the space charge, and the amount of current flowing is proportional to the square of the carrier mobility and the electric field strength and inversely proportional to the cube of the film thickness of the organic insulating film. To do. That is, the higher the electric field strength and the higher the mobility, the more the carrier injection is promoted, and the larger the film thickness, the more restricted. As shown in FIG. 6, the TPD layer 10
And a device having a two-layer structure in which the Alq layer 3 is combined (the above-mentioned Ta
(corresponding to the device of ng et al.), when a DC electric field is applied between the anode 40 and the cathode 5, first, holes are generated in the TPD layer 10.
It is injected into the inside and blocked at the TPD / Alq interface to form space charge (FIG. 6 (a)).

At this time, the electric field strength applied to the Alq layer 3 is
Due to the space charge at the TPD / Alq interface, the electric field strength becomes larger than the apparent electric field strength applied between the both electrodes 40 and 5, whereby electrons start to be injected into the Alq layer 3 (FIG. 6 (b)).
). Then, excitons are generated by recombination of holes and electrons in the Alq layer 3 near the TPD / Alq interface (see FIG. 6).
(c)), Alq is excited to emit light.

S-TA is formed between the TPD layer 10 and the Alq layer 3.
The order of injecting holes and electrons is the same when the Z layer is interposed, and as shown in FIG. 3, when the film thickness of the s-TAZ layer 23 is sufficiently large (about 150 Å or more),
Since the s-TAZ layer 23 has an excellent hole blocking property as described in the previous invention, the positive and negative electrodes 40, 5
The holes injected into the TPD layer 10 by applying a DC electric field therebetween are blocked at the TPD / TAZ interface (FIG. 3 (a)).

The electrons injected into the Alq layer 3 due to the formation of space charge by the holes are s-
Since the TAZ layer 23 has excellent electron transporting property, TPD / T
It is transported to the AZ interface (Fig. 3 (b)), and at this interface excitons are generated by recombination of holes and electrons (Fig. 3 (c)),
TPD, which has a lower excitation energy level than TAZ, is excited by the generated excitons and emits light.

On the other hand, as shown in FIG. 4, the s-TAZ layer 23
If the film thickness of is sufficiently small (less than about 50Å),
By applying a DC electric field between the positive and negative electrodes 40 and 5, TPD
The holes injected into the layer 10 pass through the s-TAZ layer 23 and are blocked at the TAZ / Alq interface to form space charges (FIG. 4 (a)). The holes pass through the s-TAZ layer 23 because the carrier (holes in this case) is injected into the s-TAZ layer 2 which is an organic insulating film as described above.
This is because it is inversely proportional to the cube of the film thickness of 3.

When space charge is formed by holes, electrons are injected into the Alq layer 3 (FIG. 4 (b)).
4), excitons are generated by recombination of holes and electrons at the TAZ / Alq interface (FIG. 4C), and Alq having a lower excitation energy level than TAZ is excited by the generated excitons to emit light. Furthermore, as shown in FIG. 5, s-TA
When the film thickness of the Z layer 23 is between the above values (about 50 to 15)
In the case of 0 Å), holes injected into the TPD layer 10 by applying a DC electric field between the positive and negative electrodes 40, 5 are
What is blocked at the TPD / TAZ interface and s-TA
Both pass through the Z layer 23 and are blocked at the TAZ / Alq interface (FIG. 5 (a)).

When space charge is formed by holes, electrons are injected into the Alq layer 3 (FIG. 5 (b)).
), Excitons are generated by recombination of holes and electrons at both the TPD / TAZ interface and the TAZ / Alq interface (FIG. 5).
(c)), TPD and Alq, both of which have lower excitation energy than TAZ, are excited by the generated excitons and emit light.

The holes injected into the TPD layer 10 are TP
As described above, the amount of holes injected is s− as the blocking at the D / TAZ interface and the blocking at the TAZ / Alq interface after passing through the s-TAZ layer 23. This is because it is inversely proportional to the cube of the film thickness of the TAZ layer 23. In the case of the device shown in FIG. 5, the s-TAZ layer 23 allows both holes and electrons to pass therethrough. Therefore, it is fully conceivable that both of them recombine in the s-TAZ layer 23. However, since TAZ has an emission peak in the short wavelength region of 4000 nm or less, even if holes and electrons are recombined in the s-TAZ layer 23 to generate excitons, and thus TAZ is excited, , Either a TPD layer or an Alq layer having an emission peak in a longer wavelength region,
Or since the excitation energy is transferred to both, s-T
The AZ layer 23 itself does not emit light.

As is clear from the above description, in the combination of the TPD layer 10, the s-TAZ layer 23 and the Alq layer 3, by adjusting the film thickness of the s-TAZ layer 23 within the above-mentioned range, I was able to change my work. However, the relationship between the function of the carrier transport control layer 23 made of s-TAZ and the film thickness range of the carrier transport control layer 23 in the present invention does not necessarily match the above example. The range of the film thickness of the carrier transport control layer 23 that performs a specific function is a different value based on factors such as a difference in materials constituting each layer and a difference in layer structure (evaporation film or binder dispersion film, etc.). Becomes As is clear from the description of FIG. 5, the carrier transport control layer 23 made of s-TAZ.
Is due to the fact that the amount of injected holes is inversely proportional to the cube of the film thickness. Therefore, by adjusting the film thickness, the ratio of the emission intensity of the hole transport layer 10 and the electron transport layer 3 can be changed. .

Therefore, when the hole transport layer 10 and the electron transport layer 3 which emit light with different emission spectra are combined like the combination of the TPD layer and the Alq layer, the film thickness of the carrier transport control layer 23 can be set appropriately. There is also an advantage that the hue of the emission color of the entire element can be finely adjusted, which is a mixture of emission colors of both layers. The organic electroluminescence device of the present invention has the hole transport layer 10, s-TA
Carrier transport control layer 23 and electron transport layer 3 made of Z
Other configurations are not particularly limited as long as the three layers are included.

Like the carrier transport control layer 23, each layer other than the carrier transport control layer 23 can be formed by a vapor phase growth method such as a vacuum vapor deposition method, or the material constituting the layer is dissolved in an appropriate solvent. It can also be formed by a solution coating method in which the liquid is coated on a substrate or another layer and dried. In the first to third organic electroluminescent elements of the present invention described above, in order to improve the storage stability in the air and the life during continuous light emission, the element is protected from moisture and oxygen in the air. To shield
The protective film may be coated, or the element coated with the protective film may be further sealed with glass or polymer.

[0093]

EXAMPLES The present invention will be described below based on examples. Evaluation of stability of s-TAZ The above formula (1a) belonging to s-TAZ represented by the general formula (1)
S-TAZ1 represented by and s-T represented by formula (1b)
AZ2 and TAZ0 represented by the above formula (2) are each provided with an ITO (indium-tin-oxide) coated glass substrate (manufactured by Asahi Glass Co., Ltd., ITO film thickness 1500 to 1600).
Å), a film is formed by a vacuum evaporation method, and a film thickness of 1000 Å
Thin film was formed. Deposition conditions are ultimate vacuum: 1-2
× 10 ^-5 Torr, substrate temperature: room temperature, deposition rate: 2-4Å /
It was seconds.

Next, each of the above samples was allowed to stand in the air at room temperature, and the surface condition of the thin film was measured with a step meter at regular time intervals to evaluate its smoothness. The results are shown in FIGS. In addition, each figure immediately after leaving (= 0 hours, FIG. 7),
Measurement results after 24 hours (FIG. 8), 48 hours (FIG. 9), 96 hours (FIG. 10), 168 hours (FIG. 11), 384 hours (FIG. 12) and 552 hours (FIG. 13). Is shown. In each figure, the upper row is a thin film of TAZ0,
The middle row shows the measurement results of the s-TAZ1 thin film and the lower row shows the measurement results of the s-TAZ2 thin film.

From the results of these figures, it was found that the thin film of TAZ0 had unprecedented irregularities on the surface 48 hours after standing, and TAZ0 aggregated or crystallized. On the other hand, the s-TAZ1 thin film did not show any new irregularities even after 552 hours had passed, and
In the thin film of -TAZ2, no new unevenness was observed until 384 hours after being left.
It was confirmed that the thin films of 1 and s-TAZ2 both have less surface irregularities over time than the thin film of TAZ0, have excellent thermal stability, and can dramatically improve the life of the device.

Example 1 PVK represented by the above formula (3) and 5 for this PVK
TPB represented by the formula (4) in a mol%, 0.3 mol% of coumarin 6 represented by the formula (5) with respect to PVK, and PV
A coating liquid was prepared by dissolving 0.2 mol% of K and DCM represented by the formula (7) with K in dichloromethane. Then, this coating solution is applied onto an ITO (indium-tin-oxide) coated glass substrate (manufactured by Asahi Glass Co., Ltd., ITO film thickness 1500 to 1600Å) having a sheet resistance of 15 Ω / □ by a dip coating method, dried and then transported by holes. A light-emitting layer was formed.

Next, TAZ0 represented by the above formula (2) and Alq represented by the above formula (9) as electron transport materials were formed on this hole transporting light emitting layer in this order by a vacuum deposition method. The film was formed into an electron transport layer having a two-layer structure. The light emitting region had a square shape with a length of 0.5 cm and a width of 0.5 cm. The conditions for vapor deposition of the TAZ layer and the Alq layer are as follows: ultimate vacuum: 1-2 × 10 ⁻⁵ Torr, substrate temperature: room temperature, vapor deposition rate:
It was 2 to 4Å / sec, and the film thickness of each layer was as follows: hole transporting light emitting layer = 400 to 500Å, TAZ layer = 200Å, Alq layer = 300Å.

Next, magnesium and silver were co-evaporated on the above Alq layer to obtain a film thickness of 2000Å and Mg / Ag = 10/1.
After forming the Mg / Ag electrode layer (molar ratio), silver was vapor-deposited on the electrode layer to form a protective layer having a film thickness of 1000Å.
An organic electroluminescence device having the layer structure shown in (a) was obtained. The electrode layer had a deposition rate of 11Å / sec, and the protective layer had a deposition rate of 10Å / sec.

Using the ITO film of the organic electroluminescent device produced as described above as an anode and the Mg / Ag electrode layer as a cathode, a direct current electric field was applied between the two electrodes at room temperature and in the atmosphere to cause the light emitting layer to emit light. The emission luminance was measured using a luminance meter (LS-100 manufactured by Minolta Co., Ltd.), and was 1
Brightness 33 at a driving voltage of 6 V and a current density of 250 mA / cm ^2.
White light emission of 52 cd / m ² was observed. Further, when this white light emission was measured at room temperature using a fluorescence photometer (F4010 manufactured by Hitachi, Ltd.), as shown in FIG.
An emission spectrum was obtained over the entire visible light range of 0 to 700 nm. Furthermore, even if this device was kept at room temperature for several days, no change in appearance was observed, and it was possible to emit light with the same level of luminance as immediately after manufacture.

Example 2 Instead of TAZ0, s-TA represented by the above formula (1a)
An organic electroluminescence device was produced in the same manner as in Example 1 except that Z1 was used as an electron transport material, and its characteristics were examined. As a result, white light emission having an emission spectrum similar to that in Example 1 was obtained. It was In addition, this device was tested at room temperature in an inert gas atmosphere with an initial luminance of 100 cd.
When continuously emitting light at / m ² , it was possible to continuously emit light for one month or more.

Example 3 PVK and 5 mol% TPB to PVK were dissolved in dichloromethane to prepare a coating solution, except that
Example 1 to fabricate an organic electroluminescent device in the same manner as were examined their characteristics, the driving voltage of 16V, 220 mA / cm luminance 1500 cd / m ² at a ^second current density
Blue emission was observed. Further, when this blue light emission was measured using the above-mentioned fluorescence photometer, an emission spectrum having a peak at a wavelength of 450 nm was obtained as shown in FIG. 15, and it was confirmed that the light was emitted from TPB. Furthermore, even if this device was kept at room temperature for several days, no change in appearance was observed, and it was possible to emit light with the same level of luminance as immediately after manufacture.

Example 4 An organic electroluminescent device was prepared in the same manner as in Example 3 except that s-TAZ1 was used as the electron transport material in place of TAZ0, and the characteristics thereof were investigated. Blue light emission having an emission spectrum similar to that of Example 3 was obtained. When this device was made to continuously emit light at an initial luminance of 100 cd / m ² in an inert gas atmosphere at room temperature, it was possible to continuously emit light for one month or more.

Example 5 An organic electroluminescence device was prepared in the same manner as in Example 1 except that PVK and 1 mol% of coumarin 6 based on this PVK were dissolved in dichloromethane to prepare a coating solution. The characteristics were examined, and a luminance of 2200 cd / at a driving voltage of 16 V and a current density of 340 mA / cm ^2.
A green emission of m ² was observed. Further, when this green light emission was measured using the above-mentioned fluorescence photometer, an emission spectrum having a peak at a wavelength of 510 nm was obtained as shown in FIG. 16, and it was confirmed that the emission was from coumarin 6. Furthermore, even if this device was kept at room temperature for several days, no change in appearance was observed, and it was possible to emit light with the same level of luminance as immediately after manufacture.

Example 6 An organic electroluminescence device was prepared in the same manner as in Example 5 except that s-TAZ1 was used as the electron transport material in place of TAZ0, and the characteristics thereof were examined. Green light emission having an emission spectrum similar to that of Example 5 was obtained. When this device was made to continuously emit light at an initial luminance of 100 cd / m ² in an inert gas atmosphere at room temperature, it was possible to continuously emit light for one month or more.

Example 7 An organic electroluminescence device was prepared in the same manner as in Example 1 except that PVK and 0.1 mol% of DCM with respect to this PVK were dissolved in dichloromethane to prepare a coating solution. Then, when the characteristics were examined, a luminance of 1100 cd / at a driving voltage of 16 V and a current density of 210 mA / cm ^2.
White emission of m ² was observed. Further, when this white light emission was measured using the above-mentioned fluorescence photometer, as shown in FIG. 17, the light emission from PVK having a wavelength of 410 nm and the wavelength of 550
It was confirmed that the light was emitted from the DCM of nm.

Therefore, when a device was similarly prepared by setting the concentration of DCM to PVK to 2 mol% in the coating liquid and examining its characteristics, the peak at the wavelength of 550 nm was found to be 4 nm.
It became larger than the peak at 10 nm and the emission became orange. Furthermore, even if these devices were kept at room temperature for several days, no change was observed in their appearance, and they were able to emit light with the same level of emission brightness as immediately after manufacture.

Example 8 An organic electroluminescence device was prepared in the same manner as in Example 7 except that s-TAZ1 was used as the electron transport material in place of TAZ0, and the characteristics thereof were examined. White or orange luminescence with an emission spectrum similar to 7 was obtained. In addition, these elements were subjected to an initial luminance of 100 cd in an inert gas atmosphere at room temperature.
When continuously emitting light at / m ² , it was possible to continuously emit light for one month or more.

Example 9 An ITO (indium-tin-oxide) coated glass substrate having a sheet resistance of 15 Ω / □ (manufactured by Asahi Glass Co., Ltd., ITO film thickness 1500 to 1600Å) was used as a hole transporting light emitting material, and the above formula (3) was used. ) PVK represented by the above formula is formed by a dip coating method using dichloroethane as a solvent, and then s-TAZ1 represented by the above formula (1a) and the above-mentioned s-TAZ1 represented by the above formula (1a) as an electron transport material on the PVK layer formula
Alq represented by (9) was formed in this order by a vacuum evaporation method. The light emitting region had a square shape with a length of 0.5 cm and a width of 0.5 cm. The vapor deposition conditions were the same as in Example 1, and the thickness of each layer formed was PVK layer (hole transporting light emitting layer) = 400Å, s-TAZ layer = 200Å, Alq.
Layer (electron transport layer) = 300Å.

Next, magnesium and silver were co-evaporated on the above Alq layer to obtain a film thickness of 2000Å and Mg / Ag = 10/1.
After forming a Mg / Ag electrode layer (molar ratio), silver is vapor-deposited on the electrode layer to form a protective layer having a film thickness of 1000Å.
An organic electroluminescence device having a layer structure shown in (a) was obtained. The vapor deposition rates of the electrode layer and the protective layer were the same as in Example 1.

Using the ITO film of the organic electroluminescence device produced as described above as an anode and the Mg / Ag electrode layer as a cathode, a direct current electric field was applied between the two electrodes at room temperature in the air to cause the light emitting layer to emit light. The emission luminance was measured using a luminance meter (LS-100 manufactured by Minolta Co., Ltd.), and was 4
Light emission started from V, and blue light emission with a luminance of 1500 cd / m ² was observed at a driving voltage of 15 V (270 mA / cm ² ) at maximum. Considering that the emission brightness in the blue region of the CRT is about ²⁰ to 30 cd / m ² , it can be seen that the blue emission of the device of this example has extremely high brightness.

The blue emission was measured at room temperature using a fluorimeter (F4010 manufactured by Hitachi Ltd.), and an emission spectrum having a peak at a wavelength of 410 nm was obtained. This emission spectrum is almost the same as the emission spectrum of PVK itself. Therefore, the device of Example 9 is PVK.
It was confirmed that the layer was emitting light. In addition, this element
Initial brightness of 100 cd / m ² in an inert gas atmosphere at room temperature
When it was made to continuously emit light, it could be continuously emitted for one month or more.

Comparative Example 1 An organic electroluminescence device was prepared in the same manner as in Example 9 except that TAZ0 was used as an electron transport material instead of s-TAZ1.
When light was continuously emitted at an initial luminance of 100 cd / m ² in an inert gas atmosphere, the light emission stopped after 10 hours.

Example 10 An organic electroluminescent device was prepared in the same manner as in Example 9 except that the Alq layer was omitted, and its characteristics were examined. As a result, the light emission starting voltage was slightly increased and the maximum current value was increased. Although it was small, high-intensity blue light emission was obtained as in Example 9.

When this device was made to continuously emit light at an initial luminance of 100 cd / m ² in an inert gas atmosphere at room temperature, it was possible to continuously emit light for one month or more. Example 11 TPD, s-TAZ2, on an ITO (indium-tin-oxide) coated glass substrate (made by Asahi Glass Co., Ltd., ITO film thickness 1500 to 1600Å) having a sheet resistance of 15 Ω / □.
And Alq were formed in this order by a vacuum evaporation method.
The light emitting region had a square shape with a length of 0.5 cm and a width of 0.5 cm. The vapor deposition conditions were the same as in Example 1, and the thickness of each layer formed was TPD layer (hole transport layer) = 40.
0Å, s-TAZ layer (carrier transport control layer) = 150
Å, Alq layer (electron transport layer) = 450 Å.

Next, magnesium and silver were co-deposited on the Alq layer to obtain a film thickness of 2000Å and Mg / Ag = 10/1.
After forming a Mg / Ag electrode layer (molar ratio), silver is vapor-deposited on the electrode layer to form a protective layer having a film thickness of 1000Å.
An organic electroluminescence device having a layer structure shown in (b) was obtained. The vapor deposition rates of the electrode layer and the protective layer were the same as in Example 1.

Using the ITO film of the organic electroluminescent device produced as described above as an anode and the Mg / Ag electrode layer as a cathode, a direct current electric field was applied between the two electrodes at room temperature and in the atmosphere to cause the light emitting layer to emit light. The emission luminance was measured using a luminance meter (LS-100 manufactured by Minolta Co., Ltd.), and the luminance was 6000 at a maximum driving voltage of 15 V (200 mA / cm ² ).
A blue emission of cd / m ² was observed.

The blue emission was measured at room temperature using a fluorometer (F4010 manufactured by Hitachi Ltd.), and an emission spectrum having a peak at a wavelength of 464 nm was obtained. This emission spectrum is almost the same as the emission spectrum of the single vapor-deposited film of TPD. Therefore, in the device of Example 11, it was confirmed that the TPD layer was emitting light. In addition, this element was subjected to an initial luminance of 10 at room temperature in an inert gas atmosphere.
When continuously emitting light at 0 cd / m ² , it was possible to continuously emit light for 5 days.

Examples 12 and 13 The s-TAZ layer as the carrier transport control layer was replaced with s-TA.
An organic electroluminescence device was prepared in the same manner as in Example 11, except that a vapor deposition film made of Z1 having a thickness of 50 Å (Example 12) or a vapor deposition film made of s-TAZ1 having a thickness of 100 Å (Example 13) was used. It was made.

Comparative Example 2 Instead of the s-TAZ layer, a film thickness of 100 Å made of TAZ0.
An organic electroluminescent element was produced in the same manner as in Example 11 except that the vapor-deposited film of 2 was used as the carrier transport control layer. When the emission spectra of the devices of Examples 12 and 13 and Comparative Example 2 were measured in the same manner as in Example 11, the devices of Example 12 and Comparative Example 2 exhibited Alq.
The element of Example 13 emitted blue light, which was the emission color of the TPD layer, although it emitted green light that was the emission color of the layer and blue emission that was the emission color of the TPD layer. Therefore, the s-TAZ layer composed of s-TAZ1 is TA
It was confirmed to have a higher hole blocking property than that of Z0.

[0120]

As described above in detail, in the first organic electroluminescent device of the present invention, since the hole transporting light emitting layer is constituted by dispersing the dye in the polymer, the conventional low molecular weight element is used. It has better heat resistance than the hole transport layer made of the above materials. The hole-transporting light-emitting layer also has excellent adhesion to a substrate such as ITO glass or ITO film. Therefore, it is possible to form a hole-transporting light-emitting layer in which deterioration, aggregation, crystallization and the like due to heat generation during light emission of the element are unlikely to occur, and the stability of the element can be improved.

Further, the hole transporting light emitting layer is
By combining with a 4-triazole derivative, especially an electron transport layer composed of s-TAZ represented by the general formula (1), carrier injection efficiency, particularly electron injection efficiency is improved as compared with a conventional single layer. Therefore, it is possible to emit light with high efficiency and high brightness. Moreover, since the s-TAZ has excellent stability, the life of the device can be dramatically improved.

Further, since the dyes can be easily dispersed in the polymer by adjusting the solution, it is possible to simultaneously disperse various dyes. Depending on the kind and combination of the dyes,
It is possible to realize multi-color display with good color purity by the three primary colors of R, G, B, white light emission, and natural light emission. In addition, according to the second organic electroluminescence device of the present invention, the s-T having excellent hole blocking property is excellent.
By the action of the AZ layer, the coupling efficiency of electrons and holes can be further improved as compared with the conventional one, and the excitons formed by the coupling of both can be more effectively confined in the light emitting layer. Further, since the s-TAZ has excellent stability, the life of the device can be dramatically improved.

Therefore, the organic electroluminescence device of the present invention has high luminous efficiency and luminous brightness and is excellent in stability. Further, in the organic electroluminescence device of the present invention, by combining the layer of s-TAZ excellent in hole blocking property with the light emitting layer of blue light emission having insufficient light emission efficiency as described above, it has been difficult to put into practical use in the past. It is also possible to achieve the desired high brightness blue light emission.

By combining a layer of PVK, which is a polymer that emits blue light and is a polymer, with the layer of s-TAZ, a blue-emitting organic electroluminescent device having higher efficiency, higher brightness, and excellent stability can be obtained. A luminescence element is obtained. Further, the combination of the above two with the addition of the Alq layer provides higher efficiency, higher brightness, and excellent stability.

Furthermore, the third organic electroluminescent device of the present invention is the same as the previous invention because the carrier transport control layer made of s-TAZ is interposed between the hole transport layer and the electron transport layer. In addition, due to the exciton confinement effect of the carrier transport control layer, the hole transport layer or the electron transport layer can be used as a light emitting layer to emit light with high brightness and high efficiency, and the light emitting efficiency and the light emitting brightness can be improved and the stability associated therewith can be improved. In addition to being possible, the luminous efficiency of blue light emission can be improved to a practical range.

Since the s-TAZ is excellent in stability, the life of the device can be remarkably improved. Also s-TAZ
When either of the hole transporting layer and the electron transporting layer, or both, can be made to emit light with high brightness and high efficiency by selecting the film thickness of, the hole transporting layer and the electron transporting layer are made of materials having different emission spectra. By using one element, it becomes possible to emit light of two or more emission spectra different from each other with one element, which is impossible with the conventional electroluminescence element, and multi-color display by the three primary colors of R, G, B and white light emission. There is a possibility that light emission such as the above can be put to practical use.

Therefore, the above three organic electroluminescent elements of the present invention can be driven at a low voltage and can be effectively used for manufacturing a large-area light emitting element having flexibility because they are made of an organic material, and will be used for the future. It is highly applicable in the fields of display, lighting, display, etc.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view showing an element having a two-layer structure of an electron transport layer in the first organic electroluminescent element of the present invention, and FIG. 1 (b) is a single electron transport layer. It is sectional drawing which shows the element of a layer.

FIG. 2 (a) is a sectional view showing an element having a three-layer structure as a preferred example of the second organic electroluminescence element of the present invention, and FIG. 2 (b) is a sectional view showing the third embodiment of the present invention. It is sectional drawing which shows an example of the organic electroluminescent element of.

FIGS. 3 (a) to 3 (c) show light emission of a device having a sufficiently large s-TAZ layer as a carrier transport control layer in the three-layer structure of the third organic electroluminescence device. It is a figure explaining a principle in order.

4 (a) to 4 (c) are diagrams for sequentially explaining the light emission principle of an element in which the film thickness of the s-TAZ layer as a carrier transport control layer is sufficiently small.

5 (a) to 5 (c) show, in order, the light emitting principle of the device in which the film thickness of the s-TAZ layer as the carrier transport control layer is intermediate between those in FIGS. It is a figure explaining.

6 (a) to (c) show TP as a hole transport layer.
S-TA is formed between the D layer and the Alq layer as the electron transport layer.
It is a figure which explains the light emission principle of the element of 2 layer structure which does not interpose Z layer one by one.

FIG. 7 is a graph showing the measurement results of the surface state of each vapor-deposited film immediately after the vapor-deposited film made of these materials was left in the air in order to evaluate the thermal stability of s-TAZ and TAZ0. .

FIG. 8 is a graph showing the measurement results of the surface state of each vapor-deposited film at the stage where 24 hours have passed after leaving each vapor-deposited film in the air.

FIG. 9 is a graph showing the measurement results of the surface state of each vapor deposition film at the stage where 48 hours have passed after leaving each vapor deposition film in the air.

FIG. 10 is a graph showing the measurement results of the surface state of each vapor deposition film at the stage where 96 hours have passed after each vapor deposition film was left in the air.

FIG. 11 is a graph showing the measurement results of the surface state of each vapor-deposited film at the stage where 168 hours have passed since each vapor-deposited film was left in the air.

FIG. 12 is a graph showing the measurement results of the surface state of each vapor-deposited film at the stage where 384 hours have passed after leaving each vapor-deposited film in the air.

FIG. 13 is a graph showing the measurement results of the surface state of each vapor-deposited film after 552 hours have passed since the vapor-deposited film was left in the air.

FIG. 14 is a graph showing a result of measuring an emission spectrum of the organic electroluminescence device manufactured in Example 1 of the present invention.

FIG. 15 is a graph showing a result of measuring an emission spectrum of the organic electroluminescence device produced in Example 3 of the present invention.

FIG. 16 is a graph showing a result of measuring an emission spectrum of the organic electroluminescent element produced in Example 5 of the present invention.

FIG. 17 is a graph showing a result of measuring an emission spectrum of the organic electroluminescence device manufactured in Example 7 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hole transporting light emitting layer 2 Electron transport layer 3 Electron transport layer (Alq layer) 10 Hole transport layer 20 s-TAZ layer 21 TAZ layer 22 Alq layer 23 Carrier transport control layer

Claims (9)

[Claims] 1. An electron-transporting layer and a hole-transporting light-emitting layer are provided at least, and the hole-transporting light-emitting layer comprises:
An organic electroluminescence device comprising at least one dye dispersed in a polymer. 2. The electron transport layer comprises a layer of 1,2,4-triazole derivative alone, or a layer of 1,2,4-triazole derivative and tris (8-quinolinolate).
The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is composed of two layers of an aluminum (III) complex. 3. A 1,2,4-triazole derivative has the general formula (1): (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxyl group, an aryl group or an aralkyl group.
¹ , R ² , R ³ , R ⁴ and R ⁵ are not hydrogen atoms at the same time. The organic electroluminescent element of Claim 2 represented by these. 4. A hole-transporting light-emitting layer is formed by molecularly dispersing a dye in a polymer having a carrier-transporting property, or a polymer having no carrier-transporting property, a dye and a low molecular weight compound. The organic electroluminescence device according to claim 1, wherein the organic electroluminescence device is formed by molecularly dispersing the hole transport material. 5. The emission spectrum of the hole transporting light emitting layer is:
In order to cover the entire visible light range of wavelength 400-700 nm,
The organic electroluminescent device according to claim 1, wherein a plurality of dyes that are molecularly dispersed in the hole transporting light emitting layer are combined. 6. An organic electroluminescence device comprising at least a layer of a 1,2,4-triazole derivative represented by the general formula (1). 7. The organic electroluminescence device according to claim 5, which comprises a layer of poly-N-vinylcarbazole as a hole transporting light emitting layer. 8. The organic electroluminescence device according to claim 6, further comprising a tris (8-quinolinolato) aluminum (III) complex layer as an electron transport layer. 9. A hole-transporting layer and an electron-transporting layer are provided, and a layer represented by the general formula (1) is provided between the layers.
An organic electroluminescence device comprising a carrier transport control layer which is composed of a 2,4-triazole derivative and selectively transports at least one of holes and electrons.