JPH10270166A - Electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroluminescent element for emitting lights with high luminance and high efficiency by containing an electron transport type light emitter and a hole transport member in an organic light emission layer or a hole transport type light emitter and an electron transport member in the same. SOLUTION: A hole transport layer 2, an organic light emission layer 3, an electron transport layer 4 and an electron injection electrode 5 are sequentially stacked on a hole injection electrode 1, and the hole injection electrode 1 and the electron injection electrode 5 are connected to each other by a lead wire 8 to apply a voltage and thereby a light is emitted from the organic light emission layer 3. For the organic light emission layer 3, a hole transport type light emitter or an electron transport type light emitter is used, a charge transport member is further mixed to increase an effective contact area between the charge transport member and the light emitter, a carrier re-coupling probability is increased and light emission is increased by energy excited following the re-coupling between the hole and the electrons. For the organic light emission layer 3, an electron transport material is used in the case of the hole transport type light emitter, and in the case of the electron transport type light emitter, a charge transport material is used. Thus, an electroluminescent element capable of performing low voltage driving and prolonging a service life is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electroluminescent device having at least a hole transport layer, an organic light emitting layer and an electron transport layer between a hole injection electrode and an electron injection electrode.

[0002]

2. Description of the Related Art In recent years, with the diversification of information equipment, the need for a flat display element which consumes less power than a cathode ray tube (CRT) (CRT) and which is thinner has increased. Liquid crystal, plasma display (PD) as such a flat display element
In particular, a self-luminous electroluminescent element with a clear display and a wide viewing angle has recently been receiving attention. here,
The electroluminescent device can be roughly classified into an inorganic electroluminescent device and an organic electroluminescent device depending on the constituent materials, and the inorganic electroluminescent device has already been put to practical use and commercially available as a product.

However, the driving voltage of the above-mentioned inorganic electroluminescent element is so-called collision excitation light emission in which accelerated electrons collide with the light emission center and emit light when a high electric field is applied. It is necessary to drive. For this reason, there has been a problem that the cost of peripheral devices is increased. In addition, there is also a problem that a full-color display cannot be performed because there is no luminous body that emits blue light.

On the other hand, in an organic electroluminescent device, charges (holes and electrons) injected from electrodes are recombined in a luminous body to generate excitons, which excite molecules of the luminous body. It is possible to drive at a low voltage because of so-called injection type light emission. Moreover, since it is an organic compound, the molecular structure of the luminous body can be easily changed, and any luminescent color can be obtained. Therefore, the organic electroluminescent device is very promising as a future display device.

Here, as an organic electroluminescent device, a device having two layers, a hole transporting layer and an electron transporting light emitting layer, is called Tang.
Proposed by VanSlyke (CWTang and SAVanS
lyke; Appl. Phys. Lett., 51 (1987) 913). The structure of the device was a cathode formed on a glass substrate, a hole transporting layer, an electron transporting light emitting layer, and a cathode.

In the above device, the hole transport layer functions to inject holes from the anode to the electron transporting light emitting layer, and also prevents the electrons injected from the cathode from escaping to the anode without recombination with the holes. It also serves to prevent electrons and to confine electrons in the electron-transporting light-emitting layer. For this reason, the recombination effect of electrons and holes occurs more efficiently than the conventional device having a single-layer structure due to the effect of confining electrons by the hole transport layer,
Driving voltage can be greatly reduced.

Saito et al. Have shown that, in a device having a two-layer structure, not only an electron transport layer but also a hole transport layer can be a light-emitting layer (C. Adachi, T. Tsutsui and S. Saito; Ap).
pl. Phys. Lett., 55 (1989) 1489).

As an improvement of the two-layer structure, Saito et al. Proposed an organic electroluminescent device having a three-layer structure in which an organic light-emitting layer was sandwiched between a hole transport layer and an electron transport layer (C. Adachi, S. Tokito, T.Tsut
sui and S. Saito; Jpn. J. Appl. Phys., 27 (1988) L269).
It consists of an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode formed on a glass substrate.The hole transport layer functions to confine electrons in the light emitting layer, and the electron transport layer traps holes. The luminous efficiency was further improved due to the function of confining in the light emitting layer.

[0009]

As described above, improvements have been made from the layer structure in order to improve the luminous efficiency of the organic electroluminescent device, but it is still necessary to increase the luminance and efficiency of the luminescence. It is the current situation. Further, in order for the organic electroluminescent device to emit light for a long time, it is necessary to emit light at a lower voltage and a lower current density.

In view of the above, an object of the present invention is to provide an electroluminescent device which emits light with high luminance and high efficiency.

[0011]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that at least a hole transport layer, an organic light emitting layer, In an electroluminescent device having an electron transport layer, it is effective that the organic light emitting layer contains an electron transporting luminescent material and a hole transporting material, or that the organic light emitting layer contains a hole transporting luminescent material and an electron transporting material. It was found that the above problem was solved.

In the organic light emitting layer of the present invention, a hole transporting luminescent material or an electron transporting luminescent material is used, and a charge transport material is further mixed therein. Therefore, in the organic light emitting layer, the effective contact area between the charge transporting material and the light emitting material increases, the probability of carrier recombination increases, and energy due to the energy excited by the recombination of holes and electrons at the emission center. Light emission increases, and the excitation energy level of the charge transport material is higher than the excitation level of the emission center, so that the excitation energy due to recombination of holes and electrons in the charge transport material moves to the emission center. Occurs. As a result, luminous efficiency is improved, high luminance is achieved, and low voltage driving is possible, so that long life is achieved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electroluminescent device of the present invention comprises at least a hole transport layer, an organic light emitting layer and an electron transport layer between electrodes. 1 to 4 schematically illustrate possible configurations of the electroluminescent device of the present invention. In FIG. 1, (1) denotes a hole injection electrode (anode), on which a hole transport layer (2) and an organic light emitting layer (3), an electron transport layer (4), and an electron injection electrode (5). Are sequentially laminated, and the organic light emitting layer contains an organic light emitting material and a charge transport material.

In FIG. 2, (1) is a hole injection electrode, on which a hole injection layer (6), a hole transport layer (2), an organic light emitting layer (3), and an electron transport layer (4). ) And an electron injecting electrode (5) are sequentially laminated, and the organic light emitting layer contains an organic light emitting material having a charge transporting property and a charge transporting material.

In FIG. 3, (1) is a hole injection electrode, on which a hole transport layer (2), an organic light emitting layer (3) and an electron transport layer (4), and an electron injection layer (7). And an electron injecting electrode (5) are sequentially laminated, and the organic light emitting layer contains a charge transporting organic light emitting material and a charge transporting material.

In FIG. 4, (1) is a hole injection electrode, on which a hole injection layer (6), a hole transport layer (2),
An organic light emitting layer (3), an electron transporting layer (4), an electron injecting layer (7), and an electron injecting electrode (5) are sequentially laminated. And a charge transport material.

A hole injection electrode (1) and an electron injection electrode (5)
And an organic light-emitting layer (3) emits light by applying a voltage between both electrodes.

As the charge transporting material contained in the organic light emitting layer, an electron transporting material is used when the luminous body has a hole transporting property, and a hole transporting charge transporting material is used when the luminous body is a light emitting substance. .

The conductive material used as the hole injection electrode (1) of the electroluminescent device preferably has a work function of more than 4 eV, and is preferably made of carbon, aluminum, vanadium, iron, cobalt, nickel, copper, zinc. , Tungsten, silver, tin, gold, and alloys thereof, and conductive metal compounds such as tin oxide, indium oxide, antimony oxide, zinc oxide, and zirconium oxide are used.

The metal forming the electron injection electrode (4) preferably has a work function of less than 4 eV, and magnesium, calcium, titanium, yttrium lithium, gadolinium, ytterbium, ruthenium, manganese and alloys thereof are used. .

In the electroluminescent device, at least the hole injection electrode (1) or the electron injection electrode (4) needs to be a transparent electrode so that light emission can be seen. At this time, if the electron injection electrode is a transparent electrode, the transparent electrode is easily oxidized and deteriorated, and the transparency is easily impaired. Therefore, it is preferable that the hole injection electrode be a transparent electrode.

When forming a transparent electrode, on a transparent substrate,
Using a conductive material as described above, a device such as vapor deposition, sputtering, or a method such as a sol-gel method or a method of dispersing and applying in a resin or the like is used to secure desired translucency and conductivity. I just need.

The transparent substrate has an appropriate strength and is not adversely affected by heat due to vapor deposition or the like during the production of the electroluminescent device.
The material is not particularly limited as long as it is transparent. For example, a glass substrate and a transparent resin such as polyethylene, polypropylene, polyethersulfone, and polyetheretherketone may be used. ITO with a transparent electrode formed on a glass substrate
Commercially available products such as those having a film provided on a glass plate and NESA glass using SnO ₂ as a transparent conductive film are known, but these may be used.

The fabrication of an electroluminescent device having the structure shown in FIG. 1 in which a hole transport layer, an organic light emitting layer, and an electron transport layer are laminated using the above-described electrodes will be described as an example.

First, a hole transport layer (2) is formed on the hole injection electrode (1). The hole transport layer (2) may be formed by evaporating a hole transport material, or by dip coating or spin coating a solution in which the hole transport material is dissolved or a solution in which a suitable resin is dissolved. You may.

When formed by the vapor deposition method, the thickness is usually 1 to 500 nm, and when formed by the coating method, the thickness is 5 to 500 nm.
The thickness may be about 1000 nm.

It is necessary to increase the applied voltage for emitting light as the thickness of the formed film increases, so that the luminous efficiency is poor and the electroluminescent element is liable to be deteriorated. When the film thickness is small, the luminous efficiency is improved, but the breakdown is easy and the life of the electroluminescent element is shortened.

As the hole transporting material used for the hole transporting layer, known materials can be used. For example, N, N'-diphenyl-N, N'-bis (3,4-dimethylphenyl)
-1,1′-diphenyl-4,4′-diamine, N,
N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4,4′-diamine;
N, N'-diphenyl-N, N'-bis (4-methylphenyl) -1,1'-diphenyl-4,4'-diamine, N, N'-diphenyl-N, N'-bis (1- Naphthyl) -1,1′-diphenyl-4,4′-diamine;
N, N′-diphenyl-N, N′-bis (2-naphthyl) -1,1′-diphenyl-4,4′-diamine;
N, N'-tetra (4-methylphenyl) -1,1'-
Diphenyl-4,4'-diamine, N, N'-tetra (4-methylphenyl) -1,1'-bis (3-methylphenyl) -4,4'-diamine, N, N'-diphenyl-N , N'-bis (3-methylphenyl) -1,1 '
-Bis (3-methylphenyl) -4,4'-diamine,
N, N′-bis (N-carbazolyl) -1,1′-diphenyl-4,4′-diamine, 4,4 ′, 4 ″ -tris (N-carbazolyl) triphenylamine, N, N ′,
N "-triphenyl-N, N ', N" -tris (3-methylphenyl) -1,3,5-tri (4-aminophenyl) benzene, 4,4', 4 "-tris [N, N ',
N "-triphenyl-N, N ', N" -tris (3-methylphenyl)] triphenylamine. These may be used as a mixture of two or more. In addition, a hole transporting luminescent material described below may be used as the hole transporting material.

Next, an organic light emitting layer (3) is formed on the hole transport layer (2). In the organic light emitting layer, an organic light emitting material and a charge transport material such as a hole transport material or an electron transport material are mixed. The amount of the charge transporting material to be mixed is 0.5 to 100% by weight based on the charge transporting organic luminescent material. This is because, if the amount is too small, the effect is not obtained, and if the amount is too large, it becomes an energy trap and causes a decrease in luminous efficiency.

As the hole transporting material, the following hole transporting materials, the following hole transporting organic light-emitting materials, and other hole transporting materials can be used. May be.

As the electron transporting material, for example, 2- (4
-Biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2- (1-naphthyl) -5- (4-tert-butylphenyl) -1,3,3
4-oxadiazole, 1,4-bis {2- [5- (4
-Tert-butylphenyl) -1,3,4-oxadiazolyl]} benzene, 1,3-bis} 2- [5- (4-te
rt-butylphenyl) -1,3,4-oxadiazolyl] {benzene, 4,4′-bis} 2- [5- (4-te
rt-butylphenyl) -1,3,4-oxadiazolyl] biphenyl, 2- (4-biphenylyl) -5-
(4-tert-butylphenyl) -1,3,4-thiodiazole, 2- (1-naphthyl) -5- (4-tert-butylphenyl) -1,3,4-thiodiazole, 1,4-
Bis {2- [5- (4-tert-butylphenyl) -1,
3,4-thiodiazolyl] {benzene, 1,3-bis} 2- [5- (4-tert-butylphenyl) -1,3,3
4-thiodiazolyl] {benzene, 4,4′-bis} 2
-[5- (4-tert-butylphenyl) -1,3,4-
Thiodiazolyl] biphenyl, 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole, 3- (1-naphthyl) -4-phenyl-5 -(4-tert-butylphenyl) -1,2,4-triazole, 1,4-bis {3-
[4-phenyl-5- (4-tert-butylphenyl)-
1,2,4-triazolyl] {benzene, 1,3-bis {3- [4-phenyl-5- (4-tert-butylphenyl) -1,3,4-oxadiazolyl]} benzene,
4,4'-bis {2- [4-phenyl-5- (4-tert
-Butylphenyl) -1,3,4-oxadiazolyl] {biphenyl, 1,3,5-tris} 2- [5-
(4-tert-butylphenyl) -1,3,4-oxadiazolyl] @benzene. These may be used as a mixture of two or more. In addition, an electron transporting luminescent material described later and other known electron transporting materials can be used.

As the charge transporting organic light emitting material used in the organic light emitting layer, known materials can be used. For example, as the electron transporting light emitting material, 2,5-bis [5,7-di-t is used.
-Pentyl-2-benzoxazolyl] thiophene,
2,2 ′-(1,4-phenylenedivinylene) bisbenzothiazole, 2,2 ′-(4,4′-biphenylene)
Bisbenzothiazole, 5-methyl-2- {2- [4-
(5-Methyl-2-benzoxazolyl) phenyl] vinyl} benzoxazole, 2,5-bis (5-methyl-2-benzoxazolyl) thiophene, perinone, coumarin, 2- (4-biphenyl)- 6-phenylbenzoxazole, aluminum trisoxine, magnesium bisoxin, bis (benzo-8-quinolinol)
Zinc, bis (2-methyl-8-quinolinol) aluminum oxide, indium trisoxin, aluminum tris (5-methyloxin), lithium oxine, gallium trisoxin, calcium bis (5-chlorooxin), polyzinc-bis (8 -Hydroxy-5
-Quinolinolyl) methane, dilithium epindridione, zinc bisoxin, zinc bisbenzooxin, 1,
Examples thereof include 2-phthaloperinone and 1,2-naphthaloperinone.

When an electron transporting luminescent material is used, it is preferably used together with a hole transporting material. As a preferable combination, when a quinolinol complex or a benzoquinolinol complex is used as the electron-transporting luminous body, it is preferable to use a diarylamino compound as the hole-transporting material. A more preferred combination is aluminum trisoxine (electron transporting luminescent material) or zinc bisbenzooxin (electron transporting luminescent material) and N, N'-diphenyl-N, N'-bis (3,4-dimethylphenyl). −
1,1′-diphenyl-4,4′-diamine (hole transporting material), N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4,4 '-Diamine (hole transporting material), the following compound (A) (hole transporting material):

Embedded image 4,4 ', 4 "-tris (N-carbazolyl) triphenylamine or N, N', N" -triphenyl-
N, N ', N "-tris (3-methylphenyl) -1,
3,5-tri (4-aminophenyl) benzene.

Examples of the hole-transporting luminescent material include epidolidine, anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, 1,4-diphenylbutadiene, tetraphenylbutadiene, acridine, stilbene, distyryl compound, 1,4-bis ( 1,1-diphenylvinyl) benzene, 1,3-bis (1,1-diphenylvinyl) benzene, 4,4′-bis (1,1-diphenylvinyl) biphenyl, 2,5-bis (1,1- Diphenylvinyl) pyridine, 2,5-bis (1,1-diphenylvinyl) thiophene, 2,5-bis (1,1-
Diphenylvinyl) furan, 5,5'-bis (1,1-
Diphenylvinyl) -2,2'-bithiophene, phenanthroline complex, bipyridyl complex and the like.

In addition, general fluorescent dyes such as fluorescent coumarin dyes, fluorescent perylene dyes, fluorescent pyran dyes, fluorescent thiopyran dyes, fluorescent polymethine dyes, fluorescent methyanine dyes, fluorescent imidazole dyes and the like are also used. it can.

When a hole transporting luminescent material is used, it is preferable to use it together with an electron transporting material. As a preferable combination, when a distyryl compound, a benzidine compound, or a condensed polycyclic compound is used as a hole-transporting light-emitting substance, an oxadiazole compound, a triazole compound, or an oxazole compound may be used as an electron transporting material. preferable. A more preferred combination is a distyryl compound (hole transporting luminescent material) and an oxadiazole compound (electron transporting material) or a triazole compound (electron transporting material).

The organic light-emitting layer may have a single-layer structure or a multi-layer structure in order to adjust characteristics such as light emission color and light emission intensity. Further, two or more kinds of light-emitting substances may be mixed or the light-emitting layer may be doped.

The organic light-emitting layer (3) may be formed by co-evaporation of an organic light-emitting substance and a charge transport material, or a solution in which the light-emitting substance and the charge transport material are dissolved or a solution in which a suitable resin is dissolved. It may be formed by dip coating or spin coating.

The thickness is usually from 1 to 500 nm when formed by a vapor deposition method, and from 5 to 500 nm when formed by a coating method.
The thickness may be about 1000 nm.

It is necessary to increase the applied voltage for emitting light as the thickness of the formed film increases, so that the luminous efficiency is poor and the electroluminescent element is liable to be deteriorated. When the film thickness is small, the luminous efficiency is improved, but the breakdown is easy and the life of the electroluminescent element is shortened.

Electron transport layer (4) on organic light emitting layer (3)
To form For the electron transporting layer, the above-described electron transporting material and the electron transporting luminescent material may be used as the electron transporting material.

The electron transporting layer may be formed by vapor deposition of an electron transporting material, or dip coating or spin coating of a solution in which the electron transporting material is dissolved or a solution in which a suitable resin is dissolved.

When formed by the vapor deposition method, the thickness is usually 1 to 500 nm, and when formed by the coating method, the thickness is 5 to 500 nm.
The thickness may be about 1000 nm.

When the film thickness is large, it is necessary to increase the applied voltage for causing light emission, which easily causes deterioration of the electroluminescent element. Further, when the film thickness is small, the luminous efficiency is improved, but the breakdown is easy, and the life of the electroluminescent element is shortened. Next, the above-described electron injection electrode is formed on the electron transport layer.

As described above, the hole transport layer (2), the organic light emitting layer (3), and the electron transport layer (4) were formed on the hole injection electrode (1).
The case where the electron injecting electrode (5) is sequentially laminated to form the electroluminescent element has been described. The hole injecting layer (6), the hole transporting layer (2), and the organic light emitting element are formed on the hole injecting electrode (1). The layer (3), the electron transport layer (4) and the electron injection electrode (5) are sequentially laminated, or the electron transport layer (4), the organic light emitting layer (3), and the hole are provided on the electron injection electrode (5). Transport layer (2),
The hole injection electrode (1) is sequentially laminated, or a hole transport layer (2), an organic light emitting layer (3), an electron transport layer (4), and an electron injection layer (7) are formed on the hole injection electrode (1). And, the electron injection electrode (5) is sequentially laminated, or the hole injection layer (6), the hole transport layer (2), the organic light emitting layer (3), and the electron transport layer are formed on the hole injection electrode (1). Of course, (4), the electron injection layer (7) and the hole injection electrode (5) may be sequentially laminated.

When the hole injection layer (6) is formed on the hole injection electrode (1) as shown in FIG. 2 or FIG. 4, a hole transporting material, a phthalocyanine compound, carbon or the like is used, and a vapor deposition method is used. By forming a thin film, the thickness is about 1 to 20 nm. If the thickness is too thick, the light-emitting intensity is weak because of poor transportability, or there is an adverse effect such that deterioration tends to be caused.If the thickness is too thin, the function as a film does not work, breakdown occurs or the cause of deterioration is caused. Problem arises.

When the electron injecting layer (7) is formed as shown in FIG. 3 or FIG. 4, the electron injecting layer is made of, for example, an electron transporting material and a metal material for an electron injecting electrode, and is formed by co-evaporation. The thickness is about 1 to 20 nm.
If the thickness is too large, electron transport is not sufficient or the electron is deteriorated. If it is too thin, the function as a film cannot be achieved.

One set of transparent electrodes, ie, an electron injection electrode and a hole injection electrode, is connected to an appropriate lead wire (8) such as a nichrome wire, a gold wire, a copper wire, a platinum wire, etc. Light is emitted by applying an appropriate voltage (Vs) to both electrodes.
The electroluminescent device of the present invention is applicable to various display devices, display devices, and the like.

[0049]

The present invention will be described below with reference to examples. Example 1 N, N'-diphenyl-N, N'-bis (3-dimethylphenyl) -1,1'-diphenyl-4,4'- as a hole transport layer on an indium tin oxide-coated glass substrate Diamine was deposited to form a thin film having a thickness of 40 nm. Next, aluminum trisoxine and N, N'-
Diphenyl-N, N'-bis (3-dimethylphenyl)-
1,1'-diphenyl-4,4'-diamine was added in a weight ratio of 10
A thin film having a thickness of 20 nm was formed by co-evaporation so as to have a ratio of 0: 1. Next, a thin film having a thickness of 40 nm was formed by vapor deposition of aluminum trisoxine as an electron transport layer. Next, as a cathode, Al was vapor-deposited for 20 minutes.
A thin film was formed so as to have a thickness of 0 nm. Thus, an electroluminescent device was manufactured.

Example 2 In Example 1, aluminum trisoxine and N, N'-diphenyl-N, N'-bis (3-
(Dimethylphenyl) -1,1′-diphenyl-4,4′-diamine by co-evaporation at a weight ratio of 10: 1.
An electroluminescent device was manufactured in exactly the same manner as in Example 1 except that a thin film was formed to a thickness of 0 nm.

Example 3 N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4, N, N'-diphenyl-N, N'-bis (3-methylphenyl) was formed on a glass substrate coated with indium tin oxide. A thin film having a thickness of 30 nm was formed by vapor deposition of 4′-diamine. Next, aluminum trisoxine and N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1 ′ were used as an organic light emitting layer.
-Diphenyl-4,4'-diamine in a weight ratio of 100: 1
Then, a thin film having a thickness of 40 nm was formed by co-evaporation. Next, a thin film having a thickness of 30 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer. Next, a thin film was formed as a cathode by Al vapor deposition to have a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Example 4 In Example 1, aluminum trisoxine and N, N'-diphenyl-N, N'-bis (3-
(Dimethylphenyl) -1,1′-diphenyl-4,4′-diamine by co-evaporation at a weight ratio of 10: 1.
An electroluminescent device was manufactured in exactly the same manner as in Example 1 except that a thin film was formed to a thickness of 0 nm.

Example 5 In Example 1, aluminum trisoxine and N, N'-diphenyl-N, N'-bis (3-
(Dimethylphenyl) -1,1′-diphenyl-4,4′-diamine was co-deposited in a weight ratio of 1: 1 by co-evaporation.
An electroluminescent device was manufactured in exactly the same manner as in Example 1 except that a thin film was formed to a thickness of nm.

Example 6 N, N'-diphenyl-N, N'-bis (3-dimethylphenyl) -1,1'-diphenyl-4 was used as a hole transport layer on a substrate of indium tin oxide coated glass. A thin film having a thickness of 45 nm was formed by vapor deposition of 4,4'-diamine. next,
Aluminum trisoxine and N, N 'as organic light emitting layer
-Diphenyl-N, N'-bis (3-dimethylphenyl)-
1,1′-diphenyl-4,4′-diamine is added in a weight ratio of 1:
A thin film having a thickness of 10 nm was formed by co-evaporation to have a thickness of 1. Next, a thin film having a thickness of 45 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer. Next, as a cathode, Al was vapor-deposited for 200 n.
A thin film was formed to have a thickness of m. Thus, an electroluminescent device was manufactured.

Comparative Example 1 N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4 was formed as a hole transport layer on a substrate of indium tin oxide coated glass. A thin film having a thickness of 50 nm was formed by vapor deposition of 4,4′-diamine. Next, a thin film having a thickness of 50 nm was formed as an organic light emitting layer by vapor deposition of aluminum trisoxine. Next, A as a cathode
A thin film was formed by vapor deposition to a thickness of 200 nm. Thus, a two-layer type electroluminescent device was manufactured.

Evaluation When the electroluminescent devices obtained in Examples 1 to 6 and Comparative Example 1 were operated at a current density of 20 mA / cm ² by gradually applying a DC voltage using the glass electrode as an anode, and The emission luminance (cd / m ² ) when operated at a current density of 60 mA / cm ² was measured. Table 1 summarizes the measurement results.

[0057]

[Table 1]

Example 7 N, N'-diphenyl-N, N'-bis (3,4-dimethylphenyl) -1,1'-diphenyl was used as a hole transport layer on a glass substrate coated with indium tin oxide. -4,4'-Diamine was deposited to form a thin film having a thickness of 50 nm. Next, as an organic light emitting layer, aluminum trisoxine and N, N '
-Diphenyl-N, N'-bis (3,4-dimethylphenyl) -1,1'-diphenyl-4,4'-diamine is co-deposited in a weight ratio of 10: 1, and has a thickness of 20 nm. Then, a thin film was formed.

Next, aluminum trisoxin was deposited as an electron transporting layer to form a thin film having a thickness of 50 nm.

Finally, Mg and Ag were deposited at an atomic ratio of 10: 1 as an electron injection electrode to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Example 8 N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-diphenyl-4 was used as a hole transport layer on a glass substrate coated with indium tin oxide. A thin film having a thickness of 50 nm was formed by vapor deposition of 4,4′-diamine.

Next, aluminum trisoxine and N, N'-diphenyl-N, N'-bis (3-
Methylphenyl) -1,1′-diphenyl-4,4′-diamine was co-deposited at a weight ratio of 20: 1, and 20 nm
To form a thin film.

Next, as an electron transporting layer, a thin film was formed to a thickness of 50 nm by vapor deposition of aluminum trisoxine.

Next, Mg and Ag having an atomic ratio of 10: 1 were deposited as an electron injection electrode to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Example 9 The following compound (A) was deposited as a hole transport layer on a glass substrate coated with indium tin oxide to form a thin film having a thickness of 50 nm.

Embedded image

Next, aluminum trisoxine and the compound (A) were co-deposited as an organic light emitting layer at a weight ratio of 30: 1 to form a thin film having a thickness of 30 nm.

Next, the following triazole compound (B) was deposited as an electron transporting layer to form a thin film having a thickness of 30 nm.

Embedded image

Next, a thin film of 200 nm in thickness was formed by vapor deposition of Mg and Ag in an atomic ratio of 10: 1 as an electron injection electrode. Thus, an electroluminescent device was manufactured.

Example 10 A thin film having a thickness of 10 nm was formed on a substrate of indium tin oxide-coated glass by vapor deposition of the following compound (C) as a hole injection layer.

Embedded image

Next, on the hole injection layer, as a hole transport layer, N, N'-diphenyl-N, N'-bis (1-naphthyl)
-1,1′-Diphenyl-4,4′-diamine was deposited to form a thin film having a thickness of 50 nm.

Next, aluminum trisoxine and N, N'-diphenyl-N, N'-bis (1-
(Naphthylphenyl) -1,1′-diphenyl-4,4′-diamine was co-deposited in a weight ratio of 15: 1, and 30
A thin film was formed with a thickness of nm.

Next, the following oxadiazole compound (D) was deposited as an electron transport layer to form a thin film having a thickness of 40 nm.

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Next, Mg and Ag having an atomic ratio of 10: 1 were deposited as an electron injection electrode to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Example 11 4,4 ', 4 "-tris [N, N', N" -triphenyl-N, N ', N "as a hole injection layer on a substrate of indium tin oxide coated glass [Tris (3-methylphenyl)] triphenylamine was deposited to form a thin film having a thickness of 5 nm.

Next, on the hole injecting layer, 4,4 ′, 4 ″ -tris (N-carbazolyl) triphenylamine was deposited as a hole transporting layer to form a thin film having a thickness of 45 nm.

Next, zinc bisbenzooxine and 4,4 ', 4 "-tris (N-carbazolyl) triphenylamine were co-deposited as an organic light emitting layer in a weight ratio of 100: 1, and a thickness of 15 nm was obtained. To form a thin film.

On top of that, 3- (4-biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole was deposited as an electron transporting layer to a thickness of 30 nm.
A thin film was formed to have a thickness of.

Next, as an electron injection electrode, a thin film was formed by vapor deposition of Mg and Ag at an atomic ratio of 10: 1 to a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Example 12 N, N'-diphenyl-N, N'-bis (3,4-dimethylphenyl) -1,1'-diphenyl was used as a hole transport layer on an indium tin oxide coated glass substrate. -4,4'-Diamine was deposited to form a thin film having a thickness of 50 nm.

Next, the following distyryl compound (E) and oxadiazole compound (D) were used in an organic light emitting layer in a weight ratio of 2:
A thin film having a thickness of 20 nm was formed by co-evaporation so that the ratio became 0: 3.

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Next, an oxadiazole compound (D) was deposited as an electron transporting layer to form a thin film having a thickness of 30 nm.

Next, as an electron injection electrode, a thin film having a thickness of 200 nm was formed by vapor deposition of Mg and Ag at an atomic ratio of 10: 1. Thus, an electroluminescent device was manufactured.

Example 13 N, N ', N "-triphenyl-N, N', N" -tris (3-methylphenyl) -1 was used as a hole transport layer on a glass substrate coated with indium tin oxide. A thin film having a thickness of 50 nm was formed by vapor deposition of 3,5-tri (4-aminophenyl) benzene.

Next, aluminum trisoxine and N, N ', N "-triphenyl-N, N', N"-
Tris (3-methylphenyl) -1,3,5-tri (4-aminophenyl) benzene was co-deposited at a weight ratio of 20: 1 to form a thin film having a thickness of 30 nm.

Next, aluminum trisoxine was deposited as an electron transport layer to form a thin film having a thickness of 45 nm.

Further, aluminum trioxin and Mg were co-deposited as an electron injection layer at a weight ratio of 30: 1 to form a thin film having a thickness of 5 nm.

Next, as an electron injection electrode, Mg and Ag having an atomic ratio of 10: 1 were deposited to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Example 14 N, N'-diphenyl-N, N'-bis (3,4-dimethylphenyl) -1,1'-diphenyl was used as a hole transport layer on a glass substrate coated with indium tin oxide. -4,4'-Diamine was deposited to form a thin film having a thickness of 50 nm.

Next, a distyryl compound is used as the organic light emitting layer.
(E) and the following triazole compound (F) in a weight ratio of 30:
The thin film was formed by co-evaporation so as to have a thickness of 20 nm.

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Next, a triazole compound (F) was deposited as an electron transporting layer to form a thin film having a thickness of 30 nm.

Next, as an electron injection electrode, Mg and Ag having an atomic ratio of 10: 1 were deposited to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Comparative Example 2 N, N′-diphenyl-N, N′-bis (3,4-dimethylphenyl) -1,1′-diphenyl was used as a hole transport layer on a substrate of indium tin oxide coated glass. -4,4'-Diamine was deposited to form a thin film having a thickness of 50 nm.

Next, aluminum trisoxin was deposited as an organic light emitting layer to form a thin film having a thickness of 20 nm.

Next, aluminum trisoxine was deposited as an electron transporting layer to form a thin film having a thickness of 50 nm.

Next, as an electron injection electrode, Mg and Ag having an atomic ratio of 10: 1 were deposited to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Comparative Example 3 A compound (A) was deposited as a hole transport layer on a substrate of indium tin oxide coated glass to form a thin film having a thickness of 50 nm.

Next, aluminum trisoxin was deposited as an organic light emitting layer to form a thin film having a thickness of 30 nm.

Next, a triazole compound (B) was deposited as an electron transporting layer to form a thin film having a thickness of 30 nm.

Next, Mg and Ag having an atomic ratio of 10: 1 were deposited as an electron injection electrode to form a thin film having a thickness of 200 nm. Thus, an electroluminescent device was manufactured.

Evaluation The voltage at which light emission starts when the DC voltage is gradually applied to the electroluminescent devices obtained in Examples 7 to 14 and Comparative Examples 1 to 3 with a glass electrode used as a hole injection electrode is used. V)
And the emission luminance (cd) when a DC voltage of 10 V is applied.
/ M ² ) was measured.

Also, the decrease rate (%) of the initial output when operated at a current density of 5 mA / cm ² for 10 hours (output (mW / cm ² ) after 10 hours / initial output (mW / cm ² ) × 100)
I asked. Table 2 summarizes the measurement results.

[0102]

[Table 2]

As can be seen from Table 2, the electroluminescent device of the present invention started to emit light at a low potential and exhibited good light emission luminance.

Further, in the electroluminescent device of the present invention, stable light emission having a long life and little decrease in output was able to be observed.

The electroluminescent device of the present invention achieves an improvement in luminous efficiency, luminous brightness and a long life. The luminescent substance, luminescent auxiliary material, charge transport material, sensitizer, resin, It is not limited to the electrode material and the like and the element manufacturing method.

[0106]

According to the present invention, in an electroluminescent device having a hole transport layer, an organic light emitting layer, an electron transport layer and an electron injection electrode provided on a hole injection electrode, the organic light emitting layer contains a charge transport material. As a result, an electroluminescent element having high light emission luminance, low light emission start voltage, and excellent durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one configuration example of an electroluminescent device according to the present invention.

FIG. 2 is a schematic sectional view of a configuration example of an electroluminescent device according to the present invention.

FIG. 3 is a schematic sectional view of a configuration example of an electroluminescent device according to the present invention.

FIG. 4 is a schematic sectional view of a configuration example of an electroluminescent device according to the present invention.

[Explanation of symbols]

 1: hole injection electrode 2: hole transport layer 3: organic light emitting layer 4: electron transport layer 5: electron injection electrode 6: hole injection layer 7: electron injection layer 8: lead wire

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuo Mori 1-5-6, Nishihioki, Nakagawa-ku, Nagoya City, Aichi Prefecture (72) Inventor Hitoshi Tsuge 5-7-5 Oyamada, Kuwana-shi, Mie Prefecture (72) Invention Person Hideaki Ueda 2-3-113 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Yoshihisa Terasaka 2-3-13-Azuchicho, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta stock In company

Claims (4)

[Claims] 1. An electroluminescent device having at least a hole transporting layer, an organic light emitting layer, and an electron transporting layer between a hole injecting electrode and an electron injecting electrode, wherein the organic light emitting layer is composed of an electron transporting luminescent material and a hole transporting material. An electroluminescent device comprising a material. 2. An electroluminescent device having at least a hole transporting layer, an organic light emitting layer, and an electron transporting layer between a hole injecting electrode and an electron injecting electrode, wherein the organic light emitting layer has a hole transporting light emitting material and an electron transporting layer. An electroluminescent device comprising a material. 3. The electroluminescent device according to claim 1, wherein the amount of the hole transporting material contained in the organic light emitting layer is 0.5 to 100% by weight of the electron transporting luminescent material. 4. The electroluminescent device according to claim 2, wherein the amount of the electron transporting material contained in the organic light emitting layer is 0.5 to 100% by weight of the hole transporting luminescent material.