JP2003257640A - Light emitting element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element effectively usable for surface light sources such as a full color display, a back light, and a lighting source and light source arrays for a printer, providing an excellent durability, and increasing a luminous efficiency and luminous brightness, and a method of manufacturing the element. <P>SOLUTION: In this light emitting device, a transparent anode, one or more layers of organic compound layers, and the light emitting element having a cathode thereon are installed on a supporting substrate. After the transparent anode and the organic compound layers are formed on the substrate, the substrate is heated and dried in vacuum inside a film forming device for forming the cathode, and the cathode is installed on the substrate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device which can be effectively used for a surface light source such as a full color display, a backlight, an illumination light source, a light source array for a printer and the like, and a method for manufacturing the same, and in particular, it has excellent emission brightness and durability. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Organic light-emitting devices using organic materials are promising for use as solid-state light-emitting inexpensive large-area full-color display devices and writing light source arrays, and many developments have been made. Generally, an organic light emitting device is composed of a light emitting layer and a pair of opposing electrodes sandwiching the light emitting layer. When an electric field is applied between both electrodes, electrons are injected from the cathode and holes are injected from the anode. Light emission is a phenomenon in which the electrons and holes recombine in the light emitting layer and energy is emitted as light when the energy level returns from the conduction band to the valence band.

The conventional organic light emitting device has a problem that the driving voltage is high and the light emission luminance and the light emission efficiency are low. In recent years, various techniques for solving this problem have been reported. As one example thereof, 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-transporting layer made of an electron-transporting material and a hole-transporting layer made of a hole-transporting material and having a single-layer structure is provided. The emission characteristics are significantly improved compared to the device. This organic light emitting device uses a low molecular weight amine compound as a hole transport material, uses an Al complex (Alq) of 8-quinolinol as an electron transport material and a light emitting material, and emits green light. 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, 1).
Page, references cited in 1997).

However, in the case of such an organic light emitting device, there is a problem that the luminous efficiency is very low as compared with the inorganic LED device and the fluorescent tube. Most of the organic light emitting devices that have been proposed at present utilize fluorescence emission obtained from singlet excitons of an organic light emitting material. In the mechanism of quantum chemistry, the ratio of singlet excitons that give fluorescence emission to triplet excitons that give phosphorescence emission in the exciton state is 1: 3, and as long as fluorescence emission is used, excitons are used. Only 25% can be effectively used, and the luminous efficiency is low.
On the other hand, if phosphorescence obtained from triplet excitons can be utilized, the luminous efficiency can be further improved.

Therefore, in recent years, an organic light emitting device utilizing phosphorescence using a phenylpyridine complex of iridium has been reported (Applied Physics Letter, Vol. 75, p. 4, 1999).
Year, Japanese Journal of Applied Physics, 38, L1502, 1999). These organic light emitting devices are 2 to 3 compared to conventional organic light emitting devices using fluorescence.
It has been reported to show double the luminous efficiency. However, it is lower than the theoretical luminous efficiency limit, and further efficiency improvement is required. Further, in the case of these organic light emitting devices, since the low molecular weight compound is formed into a film by a dry method such as a vapor deposition method, deterioration due to crystallization of the low molecular weight compound cannot be avoided, and the production cost is high and the production efficiency is high. There is a problem of being low.

On the other hand, for the purpose of reducing the manufacturing cost and applying it to a large area device such as a backlight and an illumination light source, an organic light emitting device in which a polymer compound is formed by a wet film forming method has been reported. Examples of the polymer compound include polyparaphenylene vinylene (Nature, 34
7, 539, 1990), poly (3-alkylthiophene) emitting reddish orange light (Japanese Journal of Applied Physics, 30, L1938, 1991)
), And polyalkylfluorene that emits blue light (Japanese Journal of Applied Physics, Volume 30, L 1941, 1991). Further, JP-A-2-223188 reports an attempt to disperse a low-molecular compound in a binder resin and form a film by wet coating. However, each of these uses fluorescence emission obtained from singlet excitons, and has a problem of low emission efficiency.

None of the above-mentioned coating type element, vapor deposition type element, singlet light emitting element and triplet light emitting element satisfy the durability. Moisture can be mentioned as one of the main factors. When water is present in the light emitting element, water is electrolyzed into oxygen and hydrogen, and the water and the cathode react with each other. Such a reaction causes deterioration of durability. A method of putting a desiccant in the sealing element has been proposed as a method of removing the water in the light emitting element. Although this method can remove the water in the atmosphere, it removes the water in the substrate and the organic compound layer. You cannot do it.
JP-A-2001-85161, JP-A-2001-68272, JP-A-2000-31178
No. 4 and the like propose a method of removing water in the organic compound layer, in which the organic compound layer is formed, then once taken out of the film forming apparatus, and heated and dried by a heater or the like. But,
In this method, the water is removed and then exposed to the atmosphere, so that the water is absorbed again by the organic compound layer, and it is impossible to completely remove the water. Therefore, there is a strong demand for a method of thoroughly removing water in the element.

[0008]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is that it can be effectively used for a surface light source such as a full-color display, a backlight and an illumination light source, a light source array for a printer and the like, and is excellent in durability and emission brightness. A light emitting device and a method for manufacturing the same are provided.

[0009]

The light emitting device of the present invention comprises:
It was achieved by the following means. 1. One or more layers including a transparent anode and a light emitting layer on a supporting substrate.
In a film forming apparatus that forms a cathode after forming an organic compound layer
Heat drying in vacuum at, then provide the cathode
A method of manufacturing a light emitting device, comprising: 2. In the production method described in 1 above, the heat drying
Manufacturing method, characterized in that the temperature is between 60 ℃ and 200 ℃
Law. 3. In the manufacturing method described in 1 or 2, the heating
Vacuum degree when drying is 10 ^-2Pa ~ 10^-7Specializing in being Pa
Manufacturing method. 4. In the manufacturing method according to any one of the above 1 to 3,
At least one of the organic compound layers is formed by a wet film forming method.
A manufacturing method characterized in that the film is formed more. 5. In the manufacturing method according to any one of 1 to 4 above,
The light emitting layer contains a phosphorescent compound.
And manufacturing method. 6. One or more layers including a transparent anode and a light emitting layer on a supporting substrate.
A light emitting device provided with a compound layer and a cathode, wherein
After forming a bright anode and the organic compound layer, the cathode
Heat and dry in a vacuum in the film forming equipment to be formed, and then
2. A light emitting device, characterized in that the cathode is provided. 7. In the light-emitting element as described in 6 above, the heat drying
Luminescent element characterized by a temperature of 60 to 200 ° C
Child. 8. In the light-emitting element according to the above 6 or 7, the heating
Vacuum degree when drying is 10 ^-2Pa ~ 10^-7Specializing in being Pa
Light-emitting element to be collected. 9. The light emitting device according to any one of 6 to 8 above,
At least one of the organic compound layers is formed by a wet film forming method.
A light emitting device characterized by being formed into a film. Ten. The light emitting device according to any one of 6 to 9 above,
The light emitting layer contains a phosphorescent compound.
Light emitting element.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The light emitting device of the present invention is a light emitting device in which a transparent anode, one or more organic compound layers including a light emitting layer, and a cathode are provided on a supporting substrate, and a transparent anode and an organic compound layer are formed. After that, the light emitting element is characterized in that it is heated and dried in a vacuum in a film forming apparatus for forming a cathode, and then a cathode is provided. Hereinafter, the light emitting device of the present invention will be described in detail.

[1] Constitution The overall constitution of the light emitting device is as follows: transparent anode / light emitting layer / cathode, transparent anode / light emitting layer / electron transport layer / cathode, transparent anode / hole transport layer / light emitting layer / on a substrate support. Electron transport layer / cathode, transparent anode / hole transport layer / light emitting layer / cathode, transparent anode / light emitting layer / electron transport layer / electron injection layer / cathode, transparent anode / hole injection layer /
The hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode may be laminated in this order, or these layers may be laminated in reverse.

[2] Support Substrate The support substrate preferably does not scatter or attenuate the light emitted from the organic compound layer. Specific examples include zirconia-stabilized yttrium (YSZ), inorganic materials such as glass, polyester (polyethylene terephthalate, polybutylene phthalate, polyethylene naphthalate, etc.), polystyrene, polycarbonate, polyether sulfone, polyarylate, allyldigilicol carbonate, Examples of the organic material include polyimide, polycycloolefin, norbornene resin, poly (chlorotrifluoroethylene), and polyimide. In the case of an organic material, it is preferable that it is excellent in heat resistance, dimensional stability, solvent resistance, electric insulation and workability.

The shape, structure, size, etc. of the support substrate are not particularly limited, and can be appropriately selected according to the application, purpose, etc. of the light emitting device. The shape is generally a plate. The structure may be a single layer structure or a laminated structure. Further, it may be formed of a single member or two or more members.

The supporting substrate may be colorless and transparent or colored and transparent, but is preferably colorless and transparent in that it does not scatter or attenuate the light emitted from the light emitting layer. A moisture permeation preventive layer (gas barrier layer) may be provided on the surface of the support substrate on the electrode side, the surface opposite to the electrode, or both. As a material forming the moisture permeation preventive layer, it is preferable to use an inorganic substance such as silicon nitride or silicon oxide. The moisture permeation preventive layer can be formed by a high frequency sputtering method or the like. Further, the support substrate may be provided with a hard coat layer, an undercoat layer or the like, if necessary.

[2] Transparent Anode The transparent anode generally has a function as an anode for supplying holes to the organic compound layer. The shape, structure, size, etc. of the transparent anode are not particularly limited, and can be appropriately selected from known electrodes according to the application, purpose, etc. of the light emitting element.

A preferred material for the transparent anode is a metal,
An alloy, a metal oxide, an organic conductive compound, or a mixture thereof can be used, and particularly preferably the work function is 4.
It is a material of 0 eV or more. As a specific example, a semiconducting metal oxide (tin oxide doped with antimony or fluorine (AT
O, FTO), tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), zinc indium oxide (IZO), etc.),
Metals (gold, silver, chromium, nickel, etc.), mixtures or laminates of these metals and conductive metal oxides, inorganic conductive substances (copper iodide, copper sulfide, etc.), the above semiconductive metal oxides or metals Examples thereof include compound dispersions, organic conductive materials (polyaniline, polythiophene, polypyrrole, etc.), and laminates of these with ITO.

The transparent anode is selected from among wet methods such as printing method and coating method, physical methods such as vacuum deposition method, sputtering method and ion plating method, and chemical methods such as CVD and plasma CVD method. It is formed on the substrate by a method appropriately selected in consideration of suitability with the transparent anode material. For example, when ITO is used as the material of the transparent anode, the transparent anode is formed by direct current or high frequency sputtering, vacuum deposition,
Ion plating or the like may be used. When an organic conductive compound is used as the material of the transparent anode, a wet film forming method may be used. Above all, increasing the area of the light emitting element,
From the viewpoint of productivity, it is preferable to use the wet film forming method.

The patterning of the transparent anode can be performed by chemical etching such as photolithography or physical etching using a laser or the like. Further, patterning may be performed by a vacuum deposition method using a mask, a sputtering method, a lift-off method, a printing method, or the like.

The thickness of the transparent anode can be appropriately selected depending on the material and cannot be specified unconditionally, but is usually 10
nm to 50 μm, preferably 50 nm to 20 μm.
The resistance value of the transparent anode is preferably 10 ⁶ Ω / □ or less, more preferably 10 ⁵ Ω / □ or less. In the case of 10 ⁵ Ω / □ or less, a large area light emitting device having excellent performance can be obtained by installing a bus line electrode. The transparent anode may be colorless and transparent or colored and transparent, and in order to take out light emission from the transparent anode side, its transmittance is preferably 60% or more, more preferably 70% or more. . The transmittance can be measured according to a known method using a spectrophotometer.

[3] Organic Compound Layer The organic compound layer used in the present invention comprises at least one organic compound layer including at least a light emitting layer. The formation position of the organic compound layer in the light emitting element is not particularly limited and can be appropriately selected according to the application or purpose of the light emitting element, but it is preferably formed on the transparent anode. in this case,
The organic compound layer is formed on all or part of the surface of the transparent anode. The shape, size, thickness, etc. of the organic compound layer are not particularly limited and can be appropriately selected according to the purpose.

(1) Light-Emitting Layer The light-emitting layer used in the present invention is made of at least one kind of light-emitting material, and may optionally contain a hole-transporting material, an electron-transporting material and a host compound. The light emitting material used in the present invention is not particularly limited, and may be a fluorescent light emitting compound or a phosphorescent light emitting compound. Examples of fluorescent compounds include benzoxazole derivatives, benzimidazole derivatives, benzothiazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, perylene derivatives, perinone derivatives, and oxanes. Diazole derivative, aldazine derivative,
Pyrrolidine derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives, quinacridone derivatives, pyrrolopyridine derivatives, thiadiazolopyridine derivatives, styrylamine derivatives, aromatic dimethylidene compounds, various metal complexes (metal complexes of 8-quinolinol derivatives, rare earth complexes, etc.) Polymer compounds (polythiophene derivative, polyphenylene derivative, polyphenylene vinylene derivative, polyfluorene derivative, etc.) can be used. These may be used alone or in combination of two or more.

The phosphorescent compound is not particularly limited,
Orthometallated metal complexes or porphyrin metal complexes are preferred.

The ortho-metallated metal complex referred to in the present invention is described by Akio Yamamoto in "Organometallic Chemistry-Basics and Applications-" 150.
Page, page 232, Sokabosha (issued in 1982) and H. Yersin's "Pho
tochemistry and Photophisics of Coodination Compou
nds "71-77, 135-146, Springer-Verlag (1987
(Published annually), etc. The organic compound layer containing the orthometallated metal complex has high brightness and excellent light emission efficiency.

There are various ligands forming an orthometallated metal complex, and among them, 2-phenylpyridine derivative, 7,8-benzoquinoline derivative, 2- (2-thienyl) pyridine derivative, 2- (1-naphthyl) pyridine derivative, 2
-Phenylquinoline derivatives and the like are preferable. These derivatives may have a substituent if necessary. The orthometallated metal complex may have other ligands in addition to the above ligands.

The orthometallated metal complex used in the present invention is
Inorg. Chem. 1991, No. 30, 1685, 1988, 27.
Issue, page 3464, 1994, Issue 33, page 545, Inorg.Chim.Act.
a 1991, No. 181, 245, J. Organomet. Chem. 1987,
No. 335, p. 293, J. Am. Chem. Soc. 1985, No. 107, 1431
It can be synthesized by a known method described in pages etc.
Among the orthometalated complexes, compounds that emit light from triplet excitons are preferable from the viewpoint of improving the luminous efficiency. Further, among the porphyrin metal complexes, a porphyrin platinum complex is preferable. The phosphorescent compounds may be used alone or in combination of two or more. Further, the fluorescent compound and the phosphorescent compound may be used at the same time. In the light emitting device of the present invention, it is preferable to use a phosphorescent compound from the viewpoint of emission brightness and emission efficiency.

The hole transport material is not particularly limited as long as it has any of the function of injecting holes from the anode, the function of transporting holes, and the function of blocking the electrons injected from the cathode. It may be a molecular material or a polymeric hole transport material. Specific examples thereof include a carbazole derivative, a triazole derivative, an oxazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a pyrazoline derivative, a pyrazolone derivative, a phenylenediamine derivative, an arylamine derivative, an amino-substituted chalcone derivative, and a styrylanthracene derivative. , Fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin compounds, conductive polymer oligomers (polysilane compounds, poly (N-vinylcarbazole) )
Derivative, aniline copolymer, thiophene oligomer,
Polythiophene etc.), polymer compounds (polythiophene derivative, polyphenylene derivative, polyphenylene vinylene derivative, polyfluorene derivative etc.) and the like. These may be used alone or in combination of two or more. The content of the hole transport material in the light emitting layer is preferably 0 to 99.9% by mass, more preferably 0 to 80% by mass.

The electron transport material is not particularly limited as long as it has any of the function of injecting electrons from the cathode, the function of transporting electrons, and the function of blocking the holes injected from the anode. Specific examples thereof include triazole derivatives, oxazole derivatives, oxadiazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimide derivatives, fluorenylidene methane derivatives, distyryl. Pyrazine derivatives, heterocyclic tetracarboxylic acid anhydrides such as naphthalene perylene, phthalocyanine derivatives, various metal complexes (metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzoxazole, metal complexes having benzothiazole as a ligand, etc.), Polymer compounds (aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, polyphenylene derivatives) It can be mentioned Oren derivatives, etc.), and the like. The content of the electron transport material in the light emitting layer is preferably 0 to 99.9% by mass, more preferably 0 to 80% by mass.

The host compound is a compound which causes energy transfer from its excited state to a fluorescent compound or a phosphorescent compound, and as a result causes the fluorescent or phosphorescent compound to emit light. The host compound is not particularly limited as long as it is a compound that can transfer exciton energy to the light emitting material, and can be appropriately selected according to the purpose. Specific examples thereof include carbazole derivatives,
Triazole derivative, oxazole derivative, oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative, pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, styrylanthracene derivative,
Fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin compounds, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide Derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, heterocyclic tetracarboxylic acid anhydrides such as naphthaleneperylene, phthalocyanine derivatives, various metal complexes (metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzoxazole, benzothiazo) A metal complex having a ligand such as silane), a conductive polymer oligomer (polysilane compound,
Examples thereof include poly (N-vinylcarbazole) derivatives, aniline-based copolymers, thiophene oligomers, polythiophenes, etc.), polymer compounds (polythiophene derivatives, polyphenylene derivatives, polyphenylenevinylene derivatives, polyfluorene derivatives, etc.) and the like. The host compounds may be used alone or in combination of two or more. The content of the host compound in the light emitting layer is preferably 0 to 99.9% by mass, more preferably 0 to 99.0% by mass.

If desired, an electrically inactive polymer binder may be used in the light emitting layer as another component. As the electrically inactive polymer binder, for example, polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon 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, polyvinyl acetal and the like can be mentioned. When the light emitting layer contains a polymer binder, the light emitting layer can be easily coated and formed in a large area by a wet film forming method.

(2) Other Organic Compound Layer The light emitting device of the present invention may be provided with another organic compound layer, if necessary. For example, a hole injection layer or a hole transport layer may be provided between the transparent electrode and the light emitting layer, and an electron transport layer or an electron injection layer may be provided between the light emitting layer and the cathode. It is preferable to use a hole transport material for the hole transport layer and the hole injection layer, and to use an electron transport material for the electron transport layer and the electron injection layer.

(3) Formation of Organic Compound Layer The organic compound layer is formed by a dry film forming method (evaporation method, sputtering method, etc.).
And a wet film forming method (dipping, spin coating, dip coating, casting, die coating, roll coating, bar coating, gravure coating, etc.).

In particular, in the case of coating and forming by a wet film forming method, the organic compound layer can be easily made to have a large area, and a light emitting device having high luminance and excellent light emitting efficiency can be efficiently obtained at low cost. These film forming methods can be appropriately selected depending on the material forming the organic compound layer. When the film is formed by a wet film forming method, the film is formed and then dried appropriately. As a drying condition, 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 applied and formed by a wet film forming method, a binder resin can be added to the organic compound layer. In this case, as the binder resin, polyvinyl chloride, polycarbonate, polystyrene, polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon 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, polyvinyl acetal and the like can be used. These may be used alone or in combination of two or more.

When the organic compound layer is coated and formed by a wet film forming method, the solvent used for dissolving the material of the organic compound layer to prepare the coating solution is not particularly limited, and may be a hole transport material or an orthometallated complex. , The host compound, the polymer binder, etc., can be appropriately selected. Specific examples include halogen-based solvents (chloroform, carbon tetrachloride, dichloromethane, 1,2-dichloroethane, chlorobenzene, etc.), ketone-based solvents (acetone, methyl ethyl ketone, diethyl ketone, n-propyl methyl ketone, cyclohexanone, etc.), aromatics System solvents (benzene, toluene, xylene, etc.), ester solvents (ethyl acetate, acetic acid
n-propyl, n-butyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, diethyl carbonate, etc.), ether solvents (tetrahydrofuran, dioxane, etc.), amide solvents (dimethylformamide, dimethylacetamide, etc.), dimethyl sulfoxide , Water, etc.

The solid content mass relative to the coating liquid mass and the solid content mass relative to the solvent mass are not particularly limited, and the viscosity thereof can be arbitrarily selected according to the wet film forming method.

[2] Cathode Generally, the cathode may have a function as a cathode for injecting electrons into the organic compound layer. The shape, structure, size, etc. of the cathode are not particularly limited, and can be appropriately selected from known electrodes according to the application, purpose, etc. of the light emitting element.

As the material constituting the cathode, a metal, an alloy, a metal oxide, an electrically conductive compound, a mixture thereof or the like can be used, and a material having a work function of 4.5 eV or less is preferably used. Specifically, alkali metals (Li, Na,
K, Cs, etc.), alkaline earth metals (Mg, Ca, etc.), gold, silver,
Examples thereof include lead, aluminum, sodium-potassium alloy, lithium-aluminum alloy, magnesium-silver alloy, indium, rare earth metal (ytterbium, etc.) and the like. These may be used alone, but it is preferable to use two or more kinds in combination from the viewpoint of achieving both stability and electron injection property.

Among these materials, alkali metals and alkaline earth metals are preferable from the viewpoint of electron injection property, and materials mainly containing aluminum are preferable from the viewpoint of storage stability. Here, the material mainly composed of aluminum is not only aluminum alone, but an alloy of aluminum and 0.01 to 10 mass% of an alkali metal or an alkaline earth metal (lithium-aluminum alloy, magnesium-aluminum alloy, etc.), or these. Refers to a mixture of. As the material of the cathode, those described in detail in JP-A Nos. 2-15595 and 5-121172 can be used.

The cathode is formed by forming a transparent anode and an organic compound layer on a supporting substrate, heating and drying in vacuum in a film forming apparatus for forming the cathode, and then providing the organic compound layer.

The film forming apparatus for forming the cathode may be an ordinary vacuum film forming apparatus, for example, a vacuum vapor deposition apparatus, a sputtering apparatus, an ion plating apparatus, a CVD apparatus, a plasma CVD apparatus.
A device or the like can be used. The method of heating and drying is not particularly limited. Specific examples include a method in which a halogen lamp or an infrared lamp is installed on the substrate and heating is performed by using lamp light, a method in which a resistance heating unit is installed in a substrate holder installed in a vacuum chamber, and the like.

The heating and drying temperature is preferably lower than the temperature at which the previously formed organic compound layer is denatured and within the temperature range where the effect of heating and drying is exerted. Specifically, 60 ℃ ~ 200 ℃
Is preferable, and 80 to 150 ° C. is more preferable. If the temperature is higher than 200 ° C., the temperature becomes higher than the glass transition point (Tg) of the material contained in the organic compound layer, and the organic compound is crystallized or aggregated, which is not preferable in terms of emission brightness and durability.

The vacuum heating time is not particularly limited, but is preferably 10 minutes to 10 hours. If it is shorter than 10 minutes, the effect of dry heating becomes small, and if it is longer than 10 hours, the production efficiency becomes low. The degree of vacuum during heating in the film forming equipment is 10 ^-2 Pa to 10 ^-7
Pa is preferred, 10 ^-2 Pa to 10 ^- more preferably ⁶ Pa, 10
Most preferred is ^-2 Pa to 10 ^-5 Pa. When the degree of vacuum is lower than 10 ^-2 Pa, the effect of drying and heating is small, and when the degree of vacuum is higher than 10 ^-7 Pa, the production efficiency is low.

The method for forming the cathode is not particularly limited, and a known method can be used, but it is preferably carried out in a film forming apparatus. For example, physical method (vacuum evaporation method, sputtering method, ion plating method, etc.), chemical method (CV
D, plasma CVD method, etc.) may be appropriately selected in consideration of suitability for a cathode material. For example, when two or more metals are used as the material of the cathode, the materials can be formed simultaneously or sequentially by the sputtering method or the like.

The patterning of the cathode can be performed by chemical etching such as photolithography or physical etching using a laser or the like. Further, patterning may be performed by stacking masks by a vacuum vapor deposition method, a sputtering method, a lift-off method, a printing method, or the like.

The formation position of the cathode is preferably formed on the organic compound layer. At this time, the cathode may be formed on the entire surface of the organic compound layer or only on a part thereof. Also,
A dielectric layer made of a fluoride of an alkali metal or an alkaline earth metal or the like may be provided between the cathode and the organic compound layer in a thickness of 0.1 to 5 nm. The dielectric layer can be formed by a vacuum vapor deposition method, a sputtering method, an ion plating method, or the like.

The thickness of the cathode can be appropriately selected depending on the above-mentioned materials and cannot be specified unconditionally, but usually 10
nm to 5 μm, preferably 50 nm to 1 μm. The cathode may be transparent or opaque. The transparent cathode can be formed by forming a thin film of the material forming the cathode to a thickness of 1 to 10 nm and further laminating a transparent conductive material such as ITO or IZO.

[5] Other Layers Other layers are not particularly limited and can be appropriately selected depending on the purpose. Specific examples include a protective layer and the like. As a preferred example of the protective layer, JP-A-7-85974,
7-29866, 8-22891, 10-275682, 10-106
Examples thereof include those described in No. 746. The shape, size, thickness, etc. of the protective layer can be appropriately selected, and the material thereof is
There is no particular limitation as long as it has a function of suppressing entry or permeation of substances such as water and oxygen that may deteriorate the light emitting element into the light emitting element, and examples thereof include silicon oxide, silicon dioxide and germanium oxide. , Germanium dioxide, etc. can be used.

The method for forming the protective layer is not particularly limited, and examples thereof include vacuum deposition method, sputtering method, reactive sputtering method, molecular sen epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, and plasma CVD method. , Laser CVD method, thermal CVD method, coating method and the like can be applied.

It is also preferable to provide a sealing layer for the purpose of preventing moisture and oxygen from entering each layer of the light emitting device. Examples of the material of the sealing layer include a copolymer containing tetrafluoroethylene and at least one type of comonomer, a fluorine-containing copolymer having a cyclic structure in the copolymer main chain, polyethylene, polypropylene, polymethylmethacrylate, Two or more kinds of copolymers selected from polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, chlorotrifluoroethylene and dichlorodifluoroethylene, a water absorbing material having a water absorption rate of 1% or more, Moisture-proof substances with water absorption of 0.1% or less, metals (In, Sn, Pb, Au, Cu, Ag, Al, Tl, Ni
Etc.), metal oxides (MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, Ni)
O, CaO, BaO, Fe ₂ O ₃ , Y ₂ O ₃ , TiO _2, etc., metal fluorides (MgF ₂ , LiF, AlF ₃ , CaF _2, etc.), liquid fluorinated carbon (perfluoroalkane, perfluoroamine) , Perfluoroether, etc.), liquid fluorinated carbon in which an adsorbent for water or oxygen is dispersed, and the like can be used.

Further, a water absorbent or an inert liquid can be provided in the space between the sealed container and the light emitting element. The water absorbent is not particularly limited, and specific examples include 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, vanadium bromide, molecular sieves, Zeolite, magnesium oxide, etc. may be mentioned. Examples of the inert liquid include paraffins, liquid paraffins, fluorine-based solvents (perfluoroalkane, perfluoroamine, perfluoroether, etc.), chlorine-based solvents, silicone oils and the like.

The light emitting device can obtain light emission by applying a direct current (which may include an alternating current component as necessary) voltage (usually 2 to 40 volts) or a direct current between the anode and the cathode. it can. As a driving method of the light emitting element,
JP-A Nos. 2-148687, 6-301355, 5-29080 and 7-1
34558, 8-234685, 8-241047, U.S. Patent 58284
The methods described in No. 29, No. 6023308, Japanese Patent No. 2784615 and the like can be used.

As described above, after the transparent anode and the organic compound layer are formed on the supporting substrate, they are heated and dried in a vacuum in a film forming apparatus for forming a cathode, and then the cathode is provided. It is a light-emitting element that can greatly reduce water content in the element and has excellent durability and luminous efficiency.

[0053]

The present invention will be described in more detail by the following examples, but the present invention is not limited thereto.

Example 1 A glass substrate of 2.5 cm square (thickness 0.5 mm) was DC magnetron sputtered to a thickness of 250 nm to form ITO (indium / indium).
Tin = 95/5 (molar ratio) was formed into a film, and then patterned to form a transparent anode. Surface resistance of ITO film is 6Ω / □
Met. After IPA (isopropyl alcohol) cleaning and oxygen plasma treatment, PEDOT-PSS (Baitron, Bayer) was applied on the ITO film using a spin coater.
A hole injection layer (film thickness = 100 nm) was formed by vacuum drying at 0 ° C. for 2 hours. The film thickness was measured using a stylus type film thickness meter (DEKTAK-3 manufactured by Nippon Vacuum Technology Co., Ltd.).

On the formed hole injection layer, tris (2-phenylpyridine) iridium complex as a phosphorescent compound, N-polyvinylcarbazole as a host compound and hole transport material (Mw = 69,000 manufactured by Aldrich), 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole (t-PBD) was used as an electron transport material in dichloroethane at a mass ratio of 1:40:12, respectively. The coating solution obtained by dissolution was applied using a spin coater and dried at room temperature to form a light emitting layer having a thickness of about 60 nm.

The light emitting element substrate on which the organic compound layer consisting of the hole injection layer and the light emitting layer was formed was placed in a vacuum vapor deposition apparatus for cathode installation, and a mask patterned for cathode film formation (emission area 5 mm × A mask of 4 mm) was placed on the organic compound layer. Next, it was heated with an infrared lamp at 120 ° C. for 1 hour at a vacuum degree of 2 × 10 ⁻⁴ Pa. The temperature was monitored by a thermocouple installed beside the substrate.

After heating the substrate, a magnesium-silver alloy (magnesium: silver = 10: 1 (molar ratio)) was placed in a vacuum evaporation system.
A cathode was provided by vapor deposition to a thickness of 0.25 μm, and further vapor deposition of silver to a thickness of 0.3 μm. Aluminum lead wires were respectively connected to the anode and the cathode to form a laminated structure.
The obtained laminated structure was placed in a glove box purged with nitrogen gas, and a light-emitting device was sealed by using a UV-curable adhesive (XNR5493T, manufactured by Nagase Ciba Co., Ltd.) in a glass sealing container. It was made.

A source measure unit Model 2400 manufactured by Toyo Technica Co., Ltd. was used to apply a DC voltage to the light emitting element to cause it to emit light. The maximum luminance at that time was Lmax, and the voltage when Lmax was obtained was Vmax. In addition, the luminous efficiency at 200 Cd / m ² (η
₂₀₀ ) was the external quantum efficiency. Further, this light emitting device was made to continuously emit light at an initial luminance of 200 Cd / m ² , and the time at which the luminance became half (t (1/2)) was measured. The results are shown in Table 1.

[0059]

[Table 1]

Comparative Example 1 A light emitting device was prepared and evaluated in the same manner as in Example 1 except that the substrate was not heated and dried after the organic compound layer was formed.
The results are shown in Table 1. There are more dark spots than in Example 1,
The external quantum efficiency was low and the durability was poor.

Comparative Example 2 A light emitting element substrate having an organic compound layer formed of a hole injection layer and a light emitting layer was heated in an infrared lamp at 50 ° C. for 1 hour in a vacuum vapor deposition apparatus for cathode installation. A light emitting device was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. Compared with Example 1, the number of dark spots was large, the external quantum efficiency was low, and the durability was poor.

Comparative Example 3 A light emitting element substrate having an organic compound layer formed of a hole injecting layer and a light emitting layer was placed in a sputtering apparatus for setting a transparent anode.
A light emitting device was prepared and evaluated in the same manner as in Example 1 except that the vacuum lamp was heated at 120 ° C. for 1 hour with an infrared lamp at a vacuum of 10 ⁻¹ Pa. The results are shown in Table 1. Compared with Example 1, the number of dark spots was large, the external quantum efficiency was low, and the durability was poor.

Comparative Example 4 A light-emitting element substrate on which an organic compound layer composed of a hole injection layer and a light-emitting layer was formed was dried in a vacuum dryer at a vacuum degree of 10 ^-2 Pa and 120
A light emitting device was prepared and evaluated in the same manner as in Example 1 except that the material was dried at 1 ° C. for 1 hour and then the cathode was installed by a vacuum vapor deposition apparatus for installing the cathode. The results are shown in Table 1. Compared with Example 1, the number of dark spots was large, the external quantum efficiency was low, and the durability was poor.

Example 2 On a glass substrate of 2.5 cm square (0.5 mm in thickness), an ITO target having an In ₂ O ₃ content of 95 mass% was used and DC magnetron sputtering (condition: substrate temperature 100 ℃, oxygen pressure 1 × 10 ^-3 P
According to a), a transparent anode composed of an ITO thin film (thickness 0.2 μm) was formed. The surface resistance of the ITO thin film was 10Ω / □.

On the transparent anode thus formed, N, N'-dinaphthyl-N, N'-diphenylbenzidine was provided as a hole transport layer by a vacuum deposition method at a rate of 1 nm / sec to a thickness of 0.04 μm. On top of this, tris (2-phenylpyridine) iridium complex as an orthometallated metal complex (phosphorescent compound) and 4,4'-N, N'-dicarbazolebiphenyl as a host compound at 0.1 nm / sec and 1 nm, respectively. Co-evaporation was performed at a rate of / sec to obtain a light-emitting layer having a thickness of 0.024 μm.

Furthermore, as an electron transport material, 2,
2 ', 2 "-(1,3,5-benzenetriyl) tris [3- (2-me
Tylphenyl) -3H-imidazo [4,5-b] pyridine] at 1 nm /
The electron transport layer with a thickness of 0.024 μm is formed by vapor deposition at a rate of
I got it. A hole transport layer, a light emitting layer and an electron transport layer
A light-emitting device substrate on which an organic compound layer is formed is used as a cathode mounting device.
It was installed in the vacuum evaporation system and patterned for cathode film formation.
A mask (mask with a light emitting area of 5 mm x 4 mm)
It was placed on the organic compound layer. Next, vacuum degree 4 × 10^-3 Pa,
It was heated by an infrared lamp at 80 ° C. for 1 hour. Temperature is the substrate
It was monitored by a thermocouple set aside.

After heating and drying the substrate, a magnesium-silver alloy (magnesium: silver = 10: 1 (molar ratio)) was vapor-deposited in a vacuum vapor deposition apparatus to a thickness of 0.25 μm, and silver was further 0.3 μm.
A cathode was provided by vapor deposition to a thickness of m. An aluminum lead wire was connected to each of the anode and the cathode to produce a laminated structure. The obtained laminated structure was placed in a glove box purged with nitrogen gas, and a light-emitting device was sealed by using a UV-curable adhesive (XNR5493T, manufactured by Nagase Ciba Co., Ltd.) in a glass sealing container. It was made. Using this element, the same method as in Example 1 was evaluated. The results are shown in Table 1.

[0068]

As described above, the light emitting device of the present invention is manufactured by heating and drying the substrate in a vacuum in a film forming apparatus for forming a cathode, and then providing a cathode, so that the water content in the light emitting device is greatly reduced. It has excellent durability, high brightness, and extremely high luminous efficiency. Therefore, it can be effectively used as a surface light source such as a display, a backlight, and an illumination light source.

Claims (2)

[Claims] 1. After forming one or more organic compound layers including a transparent anode and a light emitting layer on a supporting substrate, heating and drying in a vacuum in a film forming apparatus for forming a cathode, and then providing the cathode. A method for manufacturing a light-emitting element characterized by the above. 2. A light emitting device comprising a support substrate, a transparent anode, one or more organic compound layers including a light emitting layer, and a cathode, wherein the transparent anode and the organic compound layer are formed.
A light emitting device, characterized by comprising heating and drying in a vacuum in a film forming apparatus for forming the cathode, and then providing the cathode.