JP2002056976A - Organic luminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic luminescent element enabled to utilize for a surface light source of a full-color display, a back light, an array of a printer light source, or the like, enabled to illuminate in plurality, with high brightness and luminous efficiency, enabled to be manufactured into big size, and easy to manufacture. SOLUTION: The organic luminescent element formed by laminating a transparent electrode, an organic compound layer, and a back face electrode, on a substrate, comprises a hole transport layer with the organic compound layer containing a hole transport material, and a luminous layer containing an ortho- metallized complex and an electron transport material. The state that an electron affinity (Eap) of the hole transport material and an electron affinity (Eae) of the electron transport material fulfils the formula; (Eae)-(Eap)>=0.5 eV, the state of the ortho-metallized complex being an iridium complex, the state that the luminous layer contains a host compound, the state that the organic compound is formed by a wet film deposition method, or the like, are preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device which can be effectively used for a surface light source such as a full color display and a backlight and a light source array for a printer and the like.

[0002]

2. Description of the Related Art Organic light-emitting devices using organic substances are expected to be used as solid-state light-emitting inexpensive large-area full-color display devices and writing light source arrays, and many developments have been made. This organic light-emitting device generally includes a light-emitting layer and a pair of opposed electrodes sandwiching the light-emitting layer. In this organic light emitting device, when an electric field is applied between a pair of opposing electrodes, electrons are injected from a cathode and holes are injected from an anode. The electrons and holes are recombined in the light emitting layer, and when the energy level returns from the conductor to the valence band, energy is emitted as light to generate light.

[0003] Conventional organic light emitting devices have a problem that driving voltage is high and light emission luminance and light emission efficiency are low. In recent years, various techniques for solving the problems have been reported. As one example, an organic light-emitting device in which an organic thin film is formed by vapor deposition of an organic compound has been proposed (Applied Physics Letters, vol. 51, p. 913, 1987). In the case of this organic light emitting device, a conventional organic light emitting device having a laminated two-layer structure of an electron transport layer made of an electron transport material and a hole transport layer made of a hole transport material has a single-layer structure. The light emission characteristics are significantly improved as compared with the device. In this organic light emitting device, a low molecular amine compound is used as the hole transport material, and an 8-quinolinol Al complex (Alq) is used as the electron transport material and the luminescent material, and the light emission is green.

After that, many organic light-emitting devices in which an organic thin film is formed by such vapor deposition have been reported (Macromolecular Symposium, Vol. 125, pp. 1, 1).
997). However, in the case of such an organic light emitting device, there is a major problem that the luminous efficiency is extremely low as compared with an inorganic LED device and a fluorescent tube. Most of the organic light-emitting devices proposed at present utilize fluorescence emitted from singlet excitons of an organic light-emitting material. In a simple quantum chemistry mechanism, in the exciton state, the ratio of a singlet exciton that can obtain fluorescence emission to a triplet exciton that can obtain phosphorescence emission is 1: 3, and the fluorescence emission is used. 25% of excitons as long as
Can only be used effectively and the luminous efficiency is low. On the other hand, if phosphorescence obtained from triplet excitons can be used, luminous efficiency can be improved.

[0005] In recent years, an organic light-emitting device utilizing phosphorescence using an iridium phenylpyridine complex has been reported (Applied Physics Letter, vol. 75, p. 4,
1999, Japanese Journal of Applied Physics, 38, L1502, 1999
Year). According to these, it has been reported that the organic light-emitting device exhibits 2-3 times the luminous efficiency as compared with the conventional organic light-emitting device utilizing fluorescence. However, in the case of these organic light-emitting elements, since a low-molecular compound is formed by a dry method such as an evaporation method, deterioration due to crystallization of the low-molecular compound is inevitable, and the production cost is high, and the production efficiency is high. There is a serious problem that is bad.

On the other hand, an organic light emitting device in which a polymer compound is formed by a wet film forming method has been reported for the purpose of reducing the manufacturing cost and applying to a large area device such as a backlight and an illumination light source. As the polymer compound, for example, polyparaphenylene vinylene that emits green light (Nature,
347, 539, 1990), poly (3-alkylthiophene) emitting red-orange light (Japanese Journal of Applied Physics, 30, L,
1938, 1991), polyalkylfluorene (Japanese Journal of
Applied Physics, 30, L1941, 19
1991). Further, Japanese Unexamined Patent Publication No. Hei.
No. 88 discloses an attempt to disperse a low molecular compound in a binder resin and form a film by a wet film forming method. However, in each case, fluorescence emission obtained from a singlet exciton is used, and there is a fundamental problem of low luminous efficiency.

Few wet film-forming light-emitting devices using triplet excitons have been reported, and organic light-emitting devices that have high luminous efficiency, high luminous brightness, low manufacturing cost, and can be made large in area are still provided. At present, it is strongly desired to provide it.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the prior art, to meet the above-mentioned demand, and to achieve the following objects. That is, the present invention can be effectively used for a full-color display, a surface light source such as a backlight, a light source array such as a printer, and the like, and effectively uses triplet excitons, has high luminance, extremely high luminous efficiency, and has a large area. It is an object of the present invention to provide an organic light emitting device which can be manufactured at low cost and can be easily manufactured.

[0009]

Means for solving the above problems are as follows. That is, <1> a transparent electrode, an organic compound layer, and a back electrode are laminated on a substrate, and the organic compound layer is composed of a hole transport layer containing a hole transport material, an orthometalated complex, and an electron transport layer. And a light emitting layer containing a material. <2> The electron affinity (Eap) of the hole transport material and the electron affinity (Eae) of the electron transport material are represented by the following formula: (Eae) −
The organic light-emitting device according to <1>, wherein (Eap) ≧ 0.5 (eV). <3> The organic light-emitting device according to <1> or <2>, wherein the ortho-metalated complex is an iridium complex. <4> The organic light-emitting device according to any one of <1> to <3>, wherein the light-emitting layer contains a host compound. <5> The organic compound layer is formed by a wet film forming method.
An organic light-emitting device according to any one of <1> to <4>.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The organic light emitting device of the present invention comprises a transparent electrode, an organic compound layer and a back electrode laminated on a base material, and further has other layers such as a protective layer if necessary. Become. For specific examples of compounds for forming each of these layers, see, for example, “Monthly Display '98
"Organic EL Display" (published by Techno Times Co., Ltd.) in a separate volume of October issue.

—Organic Compound Layer— In the present invention, the organic compound layer comprises a hole transport layer,
At least a light emitting layer, and further, if necessary, a hole injection layer, an electron injection layer, and the like.

--Hole transport layer-- The hole transport layer contains at least a hole transport material and, if necessary, other components such as a polymer binder appropriately selected.

The material of the hole transport layer may be any material capable of transporting holes or blocking electrons injected from the back electrode. Examples of the material include a carbazole derivative and a triazole derivative. , Oxazole derivative, oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative,
Pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, phthalocyanines Porphyrin derivatives, polysilane compounds, poly (N-vinylcarbazo-
B) Derivatives, aniline-based copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, polythiophene derivatives, polyphenylene derivatives, polymer compounds such as polyphenylenevinylene derivatives, polyfluorene derivatives, polymethylphenylsilane derivatives, polyaniline derivatives, Butadiene derivatives, benzidine derivatives, polystyrene derivatives, triphenylmethane derivatives, tetraphenylbenzine derivatives, starburst polyamine derivatives, and the like. These may be used alone or in combination of two or more.

The relationship between the electron affinity (Eap) of the hole transport material and the electron affinity (Eae) of the electron transport material is expressed by the following equation: (Eae)-(Eap) ≧ 0.5 (e)
V). In this case, electrons can be confined in the light emitting layer, the electrons and holes injected from the hole transport layer can be efficiently recombined to generate excitons, and high brightness and This is advantageous in that high luminous efficiency can be obtained.

In the present invention, the hole transporting material can be appropriately selected according to the electron affinity (Eae), type, and the like of the electron transporting material.

Electron affinity (Eap) of the hole transport material
Can be measured by any method. For example, the ionization potential is measured by an atmospheric ultraviolet photoelectron analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.), and the absorption edge energy of the absorption spectrum is subtracted from this value. Can be calculated.

Note that (Eae)-(Eap) ≧ 0.5
(EV), for example, when polyvinyl carbazole (Eap = 2.3 eV) is used as the hole transport material, 4,4′- is used as the electron transport material.
N, N'-dicarbazolebiphenyl (Eae = 3.2
eV) can be used together, in this case, high brightness,
High luminous efficiency is obtained.

The content of the hole transport material in the hole transport layer is preferably 30 to 100% by weight. If the content of the hole transport material is not 30 to 100% by weight, the hole transport force may decrease and the driving voltage may increase.

The other components are not particularly limited and can be appropriately selected according to the purpose. For example, a polymer binder is preferably used. The polymer binder is not particularly limited as long as it is an electrically inactive polymer.For example, polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, and carbonized Examples include hydrogen resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane, melamine resin, unsaturated polyester, alkyd resin, epoxy resin, silicone resin, polyvinyl butyral, and polyvinyl acetal. When the hole transport layer contains the polymer binder, it is advantageous in that the hole transport layer can be easily formed over a large area by a wet film formation method.

In the case where the hole transport layer is formed by coating by a wet film forming method, the solvent used for preparing the coating solution by dissolving the material of the hole transport layer is not particularly limited. Transport material, can be appropriately selected according to the type of the polymer binder and the like, for example, chloroform, carbon tetrachloride, dichloromethane, 1,2-dichloroethane,
Halogen solvents such as chlorobenzene, ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, n-propyl methyl ketone and cyclohexanone, benzene,
Aromatic solvents such as toluene and xylene, ester solvents such as ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone and diethyl carbonate, and ether solvents such as tetrahydrofuran and dioxane Solvents, amide solvents such as dimethylformamide and dimethylacetamide, dimethylsulfoxide, water and the like. The solid content in the coating solution (the amount of the hole transport material and the polymer binder used as needed) is not particularly limited,
The viscosity can also be arbitrarily selected according to the wet film forming method.

The thickness of the hole transport layer is 10 to 2
00 nm is preferable, and 20 to 80 nm is more preferable.
When the thickness exceeds 200 nm, the driving voltage may increase, and when the thickness is less than 10 nm, the organic light emitting device may be short-circuited.

In the present invention, the hole transport layer is preferably formed by lamination with a hole injection layer. As a material of the hole injection layer, any material can be used as long as it can inject holes (holes) from the transparent electrode or can block electrons injected from the back electrode. And the like. These materials are advantageous in that the thickness (layer thickness) of the organic light emitting element can be increased without substantially increasing the driving voltage, and luminance unevenness and short circuit can be improved.

The P-type inorganic semiconductor is not particularly limited and may be appropriately selected depending on the intended purpose.
Si _1-X C _X (0 ≦ X ≦ 1), CuI, Cu ₂ S, CuS
CN and the like are preferred.

The thickness of the hole injection layer is 5 to 10
The thickness is preferably about 00 nm, more preferably 10 to 500 nm.

--Light-Emitting Layer-- The light-emitting layer must contain at least an ortho-metalated complex and an electron transporting material, preferably contains a host compound, and further contains other components appropriately selected as necessary. It contains.

The ortho-metalated complex is described, for example, in "Organometallic Chemistry-Fundamentals and Applications-" by Akio Yamamoto, p.
232 pages, Shokabosha (issued in 1982), Yer
Sin, Photochemistry and P
photophysics of Coordinati
on Compounds ", pp. 71-77, 135-1
46, Springer-Verlag (1987
This is a general term for a group of compounds described in, for example, Japanese Patent Publication No. The organic compound layer containing the ortho-metalated complex is advantageous in that it has high luminance and excellent luminous efficiency.

As the ligand forming the ortho-metalated complex, there are various ligands, which are described in the above-mentioned documents. Among them, preferred ligand is 2-
Phenylpyridine derivative, 7,8-benzoquinoline derivative, 2- (2-thienyl) pyridine derivative, 2- (1-
Naphthyl) pyridine derivatives, 2-phenylquinoline derivatives and the like. These derivatives may have a substituent as needed. The ortho-metalated complex,
It may have other ligands in addition to the ligand.
The metal forming the ortho-metalated complex includes I
Examples thereof include r, Pd, and Pt, among which iridium (Ir) is particularly preferable.

Among the above ortho-metalated complexes, compounds emitting light from triplet excitons can be suitably used in the present invention from the viewpoint of improving luminous efficiency. The ortho-metalated complex may be used alone or in combination of two or more.

The content of the ortho-metalated complex in the light emitting layer is not particularly limited and can be appropriately selected depending on the purpose. For example, the content is 0.1 to 99% by weight, and 1 to 20% by weight. % Is preferred. When the content of the ortho-metalated complex is not 0.1 to 99% by weight, the content effect may not be sufficiently exhibited. When the content is 1 to 20% by weight, the content effect is sufficient, and This is preferred in that the layer has good wet film formability.

Examples of the electron transporting material include triazole derivatives, oxazole derivatives, oxadiazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimide derivatives,
Metal complexes of heterocyclic tetracarboxylic anhydrides such as fluorenylidenemethane derivatives, distyrylpyrazine derivatives, naphthalene perylene, phthalocyanine derivatives, and 8-quinolinol derivatives, and metal complexes having metal phthalocyanine, benzoxazole, and benzothiazole as ligands Metal complexes, polysilane compounds, poly (N-
(Vinylcarbazole) derivative, aniline copolymer, thiophene oligomer, conductive polymer oligomer such as polythiophene, polythiophene derivative, polyphenylene derivative, polyphenylenevinylene derivative, polyvinylpyridine derivative, polyvinyloxadiazole derivative, triazine derivative, nitro-substituted fluorenone derivative , A fluorenylidenemethane derivative, a perylenetetracarboxyl derivative, a perinone derivative, an oxine derivative, a quinoline complex derivative, and the like. These may be used alone or in combination of two or more.

The relationship between the electron affinity (Eae) of the electron transport material and the electron affinity (Eap) of the hole transport material is expressed by the following equation: (Eae)-(Eap) ≧ 0.5 (e)
V). In this case, electrons can be confined in the light emitting layer, the electrons and holes injected from the hole transport layer can be efficiently recombined to generate excitons, and high brightness and This is advantageous in that high luminous efficiency can be obtained.

In the present invention, the electron transporting material can be appropriately selected according to the electron affinity (Eap), type, and the like of the hole transporting material.

The electron affinity (Eae) of the electron transport material
Can be measured by any method. For example, the ionization potential is measured by an atmospheric ultraviolet photoelectron analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.), and the absorption edge energy of the absorption spectrum is subtracted from this value. Can be calculated.

The content of the electron transport material in the light emitting layer is preferably 30 to 99.9% by weight. If the content of the electron transport material is not 30 to 99.9% by weight, high luminance and high luminous efficiency may not be obtained.

The host compound is a compound having a function of causing energy transfer from the excited state to the ortho-metalated complex (acting as a guest compound), thereby causing the ortho-metalated complex to emit light. . The host compound is not particularly limited as long as it is a compound capable of transferring exciton energy to the ortho-metalated complex, and can be appropriately selected depending on the intended purpose.Specifically, a carbazole derivative, Triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives , Silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin compounds, anthraquinodimethane derivatives, anthrone derivatives, dif Nylquinone derivatives, thiopyrandioxide derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, heterocyclic tetracarboxylic anhydrides such as naphthaleneperylene, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzones Various metal complexes represented by metal complexes having oxazole or benzothiazole as ligands, polysilane compounds, poly (N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, And high molecular compounds such as polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, and polyfluorene derivatives. The host compounds may be used alone or in combination of two or more.

The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include the same polymer binders as those described as the other components in the hole transport layer. . When the light emitting layer contains the polymer binder, it is advantageous in that the light emitting layer can be easily formed over a large area by a wet film forming method.

When the light emitting layer is formed by coating by a wet film forming method, the solvent used in preparing the coating solution by dissolving the material of the light emitting layer must be such that the hole transport layer is not eluted. There is no particular limitation, and examples thereof include the same solvents as those used when preparing the coating liquid for the hole transport layer.
The solid content (the amount of the orthometalated complex, the electron transporting material, and the amount of the host compound and the polymer binder used as needed) in the coating solution is not particularly limited, and the viscosity thereof is also determined according to the wet film forming method. Can be arbitrarily selected.

The thickness of the light emitting layer is 10 to 200
nm is preferable, and 20 to 80 nm is more preferable. When the thickness exceeds 200 nm, the driving voltage may increase, and when the thickness is less than 10 nm, the organic light emitting device may be short-circuited.

In the present invention, the light emitting layer is preferably formed by lamination with an electron injection layer. The material of the electron injection layer may be any material that can inject electrons from the back electrode, can transport the electrons, or can block holes (holes) injected from the transparent electrode. For example, inorganic insulating materials such as aluminum oxide, lithium fluoride, and cesium fluoride; n-type inorganic semiconductors such as n-type silicon and titanium dioxide; and n-type organic semiconductors such as naphthalenetetracarboxylic diimide can be given. The thickness of the electron injection layer is 0.01 to 10 n
m.

-Structure of Organic Compound Layer- The formation position of the organic compound layer in the organic light emitting device is not particularly limited, and can be appropriately selected depending on the use, purpose, and the like of the organic light emitting device. Preferably, it is formed on the transparent electrode or on the back electrode.
In this case, the organic compound layer is formed on the entire surface or the entire surface of the transparent electrode or the back electrode. The shape, size, thickness, and the like of the organic compound layer are not particularly limited, and can be appropriately selected depending on the purpose.

The hole injection layer may be formed between the hole transport layer and the transparent electrode, and the electron injection layer may be formed between the back electrode and the light emitting layer described later. May be. Specific layer configurations include transparent electrode / hole injection layer / hole transport layer / light emitting layer / back electrode, transparent electrode / hole injection layer / hole transport layer / light emitting layer / electron injection layer / back electrode,
And the like. In either configuration, light is usually extracted from the transparent electrode side.

In the present invention, it is preferable that a conductive polymer layer is provided between the transparent electrode and the hole transport layer in contact with the transparent electrode. In this case, the driving voltage can be hardly increased, and the thickness of the organic compound layer can be increased, which is advantageous in that uneven brightness and short circuit are improved.

The material for the conductive polymer layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a polyaniline derivative, a polythiophene derivative, a polypyrrole derivative described in WO 98/05187 and the like are suitable. It is listed. These are protonic acids (eg,
Camphor sulfonic acid, p-toluene sulfonic acid, styrene sulfonic acid, polystyrene sulfonic acid, etc.). In addition, these may be used, if necessary, with other polymers (for example, polymethyl methacrylate (P
MMA), poly-N-vinylcarbazole (PVCz)
Etc.) can be used as a mixture. The surface resistance of the conductive polymer layer is preferably 10,000Ω / □ or less. The thickness of the conductive polymer layer is 1
0-1000 nm is preferable and 20-200 nm is more preferable.

--Formation of Organic Compound Layer-- The organic compound layer is formed by a wet process such as dipping, spin coating, casting, die coating, roll coating, blade coating, bar coating, gravure coating, or the like. The coating can be formed particularly suitably by the film method. In the case of coating formation by the wet film forming method, the organic compound layer can be easily increased in area, and is advantageous in that an organic light emitting device having high luminance and excellent luminous efficiency can be efficiently obtained at low cost. . The type of the wet film forming method can be appropriately selected depending on the material of the organic compound layer. After the film is formed by the wet film forming method, drying can be appropriately performed. The conditions for the drying are not particularly limited, and a temperature or the like in a range where the layer formed by coating is not damaged can be adopted.

When the organic compound layer is formed by coating by the wet film forming method, a binder resin can be added to the organic compound layer. In this case, examples of the binder resin include polyvinyl chloride, bisphenol A-type polycarbonate, bisphenol Z-type polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, and poly (N- Vinyl carbazole), hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, butyral resin, acetal resin, ABS resin, polyurethane, melamine resin, unsaturated polyester resin,
Alkyd resin, epoxy resin, silicon resin, and the like can be given. These may be used alone or may be used alone.
More than one species may be used in combination.

-Substrate- As a material of the substrate, a material that does not transmit moisture or a material having a very low moisture permeability is preferable, and does not scatter or attenuate light emitted from the organic compound layer. Materials are preferable, for example, YSZ (zirconia-stabilized yttrium), inorganic materials such as glass, polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polyether sulfone, polyarylate, allyl diglycol carbonate, Organic materials such as synthetic resins such as polyimide, polycycloolefin, norbornene resin, and poly (chlorotrifluoroethylene), and the like. In the case of the organic material, it is preferable that the organic material is excellent in heat resistance, dimensional stability, solvent resistance, electric insulation, workability, low air permeability, low moisture absorption, and the like. Among these, when the material of the transparent electrode is indium tin oxide (ITO) which is suitably used as the material of the transparent electrode, a material having a small difference in lattice constant from the indium tin oxide (ITO) is preferred. preferable. These materials may be used alone or in combination of two or more.

The shape, structure, size, and the like of the substrate are not particularly limited, and can be appropriately selected according to the use and purpose of the light emitting device. Generally, the shape is a plate shape. The structure may be a single-layer structure, a laminated structure, a single member, or two or more members. The substrate may be colorless and transparent,
It may be colored and transparent, but is preferably colorless and transparent from the viewpoint that the light emitted from the light emitting layer is not scattered or attenuated.

It is preferable to provide a moisture permeation preventing layer (gas barrier layer) on the front surface or the back surface (the transparent electrode side) of the substrate. As a material of the moisture permeation preventing layer (gas barrier layer), inorganic substances such as silicon nitride and silicon oxide are preferably exemplified. The moisture permeation preventing layer (gas barrier layer) can be formed by, for example, a high frequency sparging method. The base material may further include a hard coat layer, an undercoat layer, and the like, if necessary.

-Transparent electrode-The transparent electrode usually only has to function as an anode for supplying holes to the organic compound layer, and the shape, structure, size and the like are not particularly limited. Instead, it can be appropriately selected from known electrodes according to the use and purpose of the organic light emitting device. The transparent electrode may function as a cathode, and in this case, the back electrode may function as an anode.

Suitable materials for the transparent electrode include, for example, metals, alloys, metal oxides, organic conductive compounds, and mixtures thereof. Materials having a work function of 4.0 eV or more are preferred. Specific examples of the material include tin oxide (ATO, FTO) doped with antimony, fluorine, and the like.
Zinc oxide, indium oxide, zinc indium oxide (IZ
O), conductive metal oxides such as indium tin oxide (ITO) and zinc aluminum oxide (AZO), gold, platinum, silver,
Chromium, metals such as nickel, and mixtures or laminates of these metals and conductive metal oxides, copper iodide, inorganic conductive substances such as copper sulfide, polyaniline, polythiophene,
Organic conductive materials such as polypyrrole, laminates of these with ITO, and the like.

The transparent electrode can be formed, for example, by a wet method such as a printing method or a coating method, a physical method such as a vacuum evaporation method, a sputtering method, or an ion plating method, or a CV.
D, a chemical method such as a plasma CVD method, or the like, and can be formed on the substrate according to a method appropriately selected in consideration of suitability for the material. For example, when ITO is selected as the material of the transparent electrode, the transparent electrode can be formed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating, or the like. When an organic conductive compound is selected as a material for the transparent electrode, it can be performed according to a wet film forming method.

The position at which the transparent electrode is formed in the organic light emitting device is not particularly limited and can be appropriately selected depending on the use, purpose, and the like of the organic light emitting device. Is preferred. In this case, the transparent electrode may be formed on the entire one surface of the substrate, or may be formed on a part thereof.

The patterning of the transparent electrode may be performed by chemical etching such as photolithography or the like, or may be performed by physical etching using a laser or the like. Or a lift-off method or a printing method.

The thickness of the transparent electrode can be appropriately selected according to the material and cannot be specified unconditionally, but is usually 10 nm to 50 μm,
~ 20 µm is preferred. The resistance value of the transparent electrode is preferably 103Ω / □ or less, more preferably 102Ω / □ or less. The transparent electrode may be colorless and transparent, or may be colored and transparent. In order to take out light emission (fluorescence) from the transparent electrode side, the transmittance is 6
0% or more is preferable, and 70% or more is more preferable. This transmittance can be measured according to a known method using a spectrophotometer or the like.

The transparent electrode is described in "New Development of Transparent Conductive Film", supervised by Yutaka Sawada, published by CMC (1999).
And these can be applied to the present invention. When using a plastic substrate with low heat resistance,
A transparent electrode formed by using TO or IZO at a low temperature of 150 ° C. or lower is preferable.

--- Back electrode--The back electrode usually has only to function as a cathode for injecting electrons into the organic compound layer, and its shape, structure, size, etc. are particularly limited. However, it can be appropriately selected from known electrodes according to the use, purpose, and the like of the light emitting element. The back electrode may function as an anode, and in this case, the transparent electrode may function as a cathode.

Examples of the material for the back electrode include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof, and those having a work function of 4.5 eV or less are preferable. Specific examples of the material include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloy, lithium- Rare earth metals such as aluminum alloys, magnesium-silver alloys, indium, ytterbium, and the like. They are,
One type may be used alone, but from the viewpoint of achieving both stability and electron injection properties, two or more types may be suitably used in combination.

Of these, alkali metals and alkaline earth metals are preferable in terms of electron injecting properties, and materials mainly composed of aluminum are preferable in terms of excellent storage stability. The material mainly composed of aluminum refers to aluminum alone or an alloy or mixture of aluminum and 0.01 to 10% by weight of an alkali metal or an alkaline earth metal (for example, a lithium-aluminum alloy, a magnesium-aluminum alloy, etc.). Say.

The material of the back electrode is described in detail in JP-A-2-15595 and JP-A-5-121172.

The formation of the back electrode is not particularly limited.
It can be performed according to a known method, for example, a printing method, a wet method such as a coating method, a physical method such as a vacuum evaporation method, a sputtering method, an ion plating method, a chemical method such as a CVD method or a plasma CVD method, and the like. Can be carried out in accordance with a method appropriately selected in consideration of suitability with the above-mentioned materials. For example, when a metal or the like is selected as the material of the back electrode, one or two or more of them can be simultaneously subjected to a sputtering method or the like. In addition,
The patterning of the back electrode may be performed by chemical etching such as photolithography,
The etching may be performed by physical etching using a laser or the like, may be performed by vacuum deposition or sputtering with a mask overlapped, or may be performed by a lift-off method or a printing method.

The position at which the back electrode is formed in the organic light-emitting device is not particularly limited, and can be appropriately selected depending on the use and purpose of the organic light-emitting device. Preferably. In this case, the back electrode is formed entirely or partially on the organic compound layer. Further, a dielectric layer of 0.1 to 5 nm in thickness of the alkali metal or the alkaline earth metal fluoride may be inserted between the back electrode and the organic compound layer. Note that the dielectric layer can be formed by, for example, a vacuum evaporation method, a sputtering method, an ion plating method, or the like.

The thickness of the back electrode can be appropriately selected according to the material and cannot be specified unconditionally, but it is usually 10 nm to 5 μm, and usually 50 nm to 50 nm.
1 μm is preferred. The back electrode may be transparent or opaque. The transparent back electrode can be formed by forming a thin film of the material of the back electrode to a thickness of 1 to 10 nm, and further laminating a transparent conductive material such as ITO or IZO.

-Other Layers- The other layers are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a protective layer. As the protective layer, for example, JP-A-7-85
974, 7-192866 and 8-22
Nos. 891, 10-275682 and 10-275
Preferable examples include those described in JP-A-106746. The protective layer is, on the outermost surface thereof, in the laminated body element, for example, when the base material, the transparent electrode, the organic compound layer, and the back electrode are laminated in this order, on the back electrode. When the base material, the back electrode, the organic compound layer, and the transparent electrode are laminated in this order, they are formed on the transparent electrode. The shape, size, thickness, and the like of the protective layer can be appropriately selected. As the material, a material that can deteriorate the light-emitting element, such as moisture or oxygen, can be penetrated or transmitted into the light-emitting element. There is no particular limitation as long as it has the function of suppressing,
For example, silicon oxide, silicon dioxide, germanium oxide, germanium dioxide, and the like can be given.

The method for forming the protective layer is not particularly limited, and includes, for example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, and the like. Plasma CVD, laser CVD, thermal CVD
Method, coating method, and the like.

In the present invention, it is preferable that at least the organic compound layer in the organic light-emitting device is sealed with a cover member such as a glass or poly (chlorotrifluoroethylene) sheet. A moisture absorbent, a water-repellent inert liquid, or the like may be inserted into the member. The water absorbent is not particularly limited,
For example, barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride, cesium fluoride, niobium fluoride, calcium bromide, bromide Vanadium, molecular sieve, zeolite, magnesium oxide, etc. are mentioned. The inert liquid is not particularly limited, but includes, for example, paraffins, liquid paraffins, fluorinated solvents such as perfluoroalkanes and perfluoroamines, perfluoroethers, chlorinated solvents, silicone oils, and the like. Can be

Further, in the present invention, it is preferable to provide a sealing layer for the purpose of preventing moisture and oxygen from entering each layer in the organic light emitting device. As the material of the sealing layer, for example, a copolymer containing tetrafluoroethylene and at least one comonomer, a fluorinated copolymer having a cyclic structure in the copolymer main chain, polyethylene, polypropylene, polymethyl methacrylate, Polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, two or more copolymers selected from chlorotrifluoroethylene and dichlorodifluoroethylene, a water-absorbing substance having a water absorption of 1% or more, Moisture-proof substance having water absorption of 0.1% or less, In, Sn, Pb, Au, Cu, Ag, Al, T
1, metal such as NI, MgO, SiO, SiO ₂ , A1 ₂ O
_{3, GeO, NlO, CaO,} BaO, Fe 2 O 3, Y 2 O
_3, a metal oxide such as TiO _2, MgF _2, LiF, Al
Metal fluorides such as F ₃ and CaF ₂ , liquid fluorinated carbon such as perfluoroalkane, perfluoroamine and perfluoroether, and liquid fluorinated carbon in which an adsorbent that adsorbs moisture and oxygen is dispersed. No.

The organic light-emitting device according to the present invention is characterized in that a direct current (which may contain an alternating current component if necessary) voltage (usually in the range of 2 to 30 volts) or a direct current is applied between the transparent electrode and the rear electrode. By applying, light emission can be obtained. The driving of the organic light emitting device of the present invention is described in JP-A-2-148687 and JP-A-6-301355.
Nos. 5-29080, 7-134558 and 8
234686, 8-241047, U.S. Pat.
Nos. 828429 and 6023308, Japanese Patent No. 27
No. 84615, etc. can be used.

[0068]

EXAMPLES Examples of the organic light emitting device of the present invention will be described below, but the present invention is not limited to these examples.

Example 1 The substrate had a thickness of 0.5
This substrate was introduced into a vacuum chamber using a 2.5 mm square glass plate, and an ITO target (indium: tin = 95: 5 (molar ratio)) having a SnO ₂ content of 10% by weight was used. And DC magnetron sputtering (conditions:
An 1TO thin film (0.2 μm thick) as a transparent electrode was formed at a substrate temperature of 250 ° C. and an oxygen pressure of 1 × 10 ⁻³ Pa). The surface resistance of the lTO thin film was 10Ω / □.

Next, the glass plate on which the transparent electrode was formed was placed in a cleaning vessel, and was subjected to IPA cleaning, followed by oxygen plasma treatment. Then, an aqueous dispersion of poly (ethylenedioxythiophene) / polystyrene sulfonic acid (manufactured by BAYER, Baytron P:
(Solid content: 1.3%), spin-coated at 150 ° C., 2
Vacuum drying was performed for a time to form a hole injection layer having a thickness of 100 nm.

Then, on this hole injection layer, polyvinyl carbazole (Mw = 63000,
(Aldrich) in dichloroethane was applied using a spin coater and dried at room temperature to form a hole transport layer having a thickness of 40 nm.

Next, on this hole transport layer, polymethyl methacrylate (PMMA, Mw = 120,000, manufactured by Aldrich) and 4,4'-N, N 'as an electron transport material
-Dicarbazole biphenyl (CBP) and tris (2-phenylpyridine) iridium complex as an orthometalated complex in a weight ratio of 10: 20: 1 in a mixed solution of methyl ethyl ketone / toluene (50/50 vol%)
Was applied using a spin coater, and vacuum-dried at 80 ° C. for 2 hours to form a light-emitting layer having a thickness of 40 nm.

Further, a patterned mask (a mask having a light-emitting area of 5 mm × 5 mm) was set on this light-emitting layer, and magnesium: silver = 10: 1 (molar ratio) was added in a vapor deposition apparatus. The back electrode was formed by depositing 25 μm and depositing 0.3 μm of silver. Aluminum lead wires were connected to the transparent electrode (functioning as an anode) and the back electrode (functioning as a cathode), respectively, to produce a laminated structure.

Here, the obtained laminated structure was placed in a glove box purged with nitrogen gas, and an ultraviolet-curing adhesive (XNR549, manufactured by Chise Nagase, manufactured by Chiba Nagase) was placed in a sealed container made of glass.
It sealed using 3). Thus, the organic light-emitting device of Example 1 was manufactured.

The electron affinities of the hole transporting material and the electron transporting material used in Example 1 were measured by the following method by preparing a sample. That is, a solution of polyvinyl carbazole, which is a hole transport material, in dichloroethane was applied to glass using a spin coater, dried at room temperature, and then a polyvircarbazole thin film having a thickness of about 100 nm was formed. Also, CBP which is an electron transport material
Is obtained by applying a toluene solution dissolved at a weight ratio of CBP / PMMA = 80/20 on a glass using a spin coater, drying at room temperature, and then forming a CBP having a thickness of about 100 nm.
/ PMMA thin film was formed.

For these, the ionization potential was measured, and the electron affinity was calculated by subtracting the value of the absorption edge of the absorption spectrum from the value. Note that the ionization potential is determined by using an atmospheric ultraviolet photoelectron analyzer AC-
1 (manufactured by Riken Keiki Co., Ltd.), the absorption spectrum was measured using UV-2200 (manufactured by Shimadzu Corporation). The results are shown in Table 1.

The following evaluation was performed on the organic light emitting device of Example 1. A DC voltage was applied to the organic light emitting device using a source measure unit 2400 manufactured by Toyo Technica to emit light. The maximum luminance at that time is defined as Lmax, and Lmax
The voltage at which max was obtained was defined as Vmax. further,
Luminous efficiency at 200 Cd / m ² at P200 (Cd / A)
And the luminous efficiency at 2000 Cd / m ² is P2000
(Cd / A). Table 1 shows the results of these measurements.

(Example 2) In Example 1, instead of CBP as the electron transporting material, 2,2 ', 2''-
(1,3,5-benzenetriyl) tris [3- (2-
An organic light-emitting device was manufactured in the same manner as in Example 1 except that methylphenyl) -3H-imidazo [4,5-b] pyridine was used, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Example 3 An organic light-emitting device was prepared in the same manner as in Example 2 except that poly (9-hexylphenylene) was used instead of polyvinyl carbazole as the hole transporting material. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 1 An organic light-emitting device was manufactured in the same manner as in Example 1, except that an aluminum complex of hydroxyquinoline (Alq) was used instead of CBP as the electron transporting material. Then, the same evaluation as in Example 1 was performed. The results are shown in Table 1. In Comparative Example 1,
The electron affinity (Eae) of Alq is 2.7 eV, and the electron affinity (Eap) of polyvinyl carbazole is 2.3.
eV, and the difference was 0.4 eV, which was smaller than 0.5 eV. As a result, both the luminous efficiency and the luminous brightness were low.

(Comparative Example 2) In Example 2, the above-mentioned hole transporting layer was formed of N, N'-dinaphthyl-N, N'-diphenylbenzidine (NPD) / polycarbonate (PC) =
An organic light-emitting device was produced in the same manner as in Example 2 except that it was formed at 80/20% by weight, and the same evaluation as in Example 2 was performed. The results are shown in Table 1. In Comparative Example 2, 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris [3- (2-methylphenyl) -3H-imidazo [4,5-b] pyridine] Electron affinity (Eae)
Is 3.0 eV, the electron affinity (Eap) of NPD is 2.6 eV, and the difference is 0.4 eV, which is 0.5 eV.
It was smaller than eV. As a result, both the luminous efficiency and the luminous brightness were low.

Comparative Example 3 Organic light emission was performed in the same manner as in Example 2 except that coumarin 6 was used instead of the tris (2-phenylpyridine) iridium complex as the ortho-metalated complex. An element was manufactured, and the same evaluation as in Example 2 was performed. The results are shown in Table 1. In Comparative Example 3, both the luminous efficiency and the luminous luminance were low because the ortho-metalated complex was not used in the luminescent layer.

[0083]

[Table 1]

[0084]

According to the present invention, the above-mentioned problems in the prior art can be solved and can be effectively used for a full-color display, a surface light source such as a backlight, a light source array such as a printer, etc., and a triplet exciton can be effectively used. Thus, it is possible to provide an organic light-emitting element that can be easily manufactured at low cost with high luminance, extremely high luminous efficiency, large area, and low cost.

Claims (5)

[Claims] A transparent electrode, an organic compound layer, and a back electrode are laminated on a base material. The organic compound layer comprises a hole transport layer containing a hole transport material, an orthometalated complex, and an electron transport layer. An organic light-emitting device comprising: a light-emitting layer containing a material. 2. An electron affinity (Eap) of a hole transport material,
The electron affinity (Eae) of the electron transporting material is expressed by the following equation (Ea).
e)-(Eap) ≧ 0.5 (eV).
3. The organic light-emitting device according to item 1. 3. The organic light-emitting device according to claim 1, wherein the ortho-metalated complex is an iridium complex. 4. The organic light emitting device according to claim 1, wherein the light emitting layer contains a host compound. 5. The organic light emitting device according to claim 1, wherein the organic compound layer is formed by a wet film forming method.