JP2010209320A - Composition for organic electroluminescent element, method for producing organic electroluminescent element, organic electroluminescent element, organic el display and organic el lighting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition that improves characteristics of an organic electroluminescent element using a wet film formation method under atmospheric environment in the composition for an organic electroluminescent element containing a low-molecular compound and a solvent; and to provide an inexpensive and high-performance organic electroluminescent element from the composition for an organic electroluminescent element which enables reduction in a production cost and improvement of productive efficiency when used for production of the organic electroluminescent element having a low molecule-based organic layer formed by the wet film formation method. <P>SOLUTION: The composition for an organic electroluminescent element is provided which contains the low-molecular compound and the solvent and has oxygen concentration and/or moisture concentration of 100 ppm or more. A method for producing the organic electroluminescent element is provided, wherein the organic electroluminescent element is formed using the composition, which contains the low-molecular compound and the solvent and has oxygen concentration and/or moisture concentration of 100 ppm or more, by the wet film formation method at the oxygen concentration of 1% or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a composition for an organic electroluminescent element for forming an organic layer of an organic electroluminescent element, an organic electroluminescent element formed using the composition, an organic EL display and organic EL illumination.
The present invention also relates to a method for producing an organic electroluminescent element, an organic electroluminescent element produced using the same, an organic EL display, and organic EL illumination.

The organic electroluminescence device usually has an anode, a cathode, and an organic layer such as a light emitting layer and a charge transport layer disposed between the anode and the cathode on a substrate. As a method for forming the organic layer, a vacuum deposition method or a wet film formation method is used.
The vacuum deposition method has advantages such as being able to form a high-quality film uniformly on the substrate, easy to obtain a device with easy lamination and excellent characteristics, and very little contamination from the manufacturing process. Many of the organic electroluminescence devices currently in practical use are based on a vacuum evaporation method using a low molecular material.

  On the other hand, the wet film forming method has advantages such as that a vacuum process is not required and a large area can be easily formed, and a plurality of materials having various functions can be put in one layer (coating liquid). is there. When the wet film forming method is used, a polymer material is usually used as the material. However, it is difficult to control the degree of polymerization and molecular weight distribution of polymer materials, deterioration due to terminal residues during continuous driving, high purity of the polymer material itself is difficult, and impurities are included. There is a problem, and there is no practical level other than elements using some polymer materials. Therefore, as an attempt to solve the above problem, in Patent Document 1 and Patent Document 2, an organic layer is formed by a wet film formation method using a low molecular material or the like, but these elements have insufficient luminous efficiency. And practicality was poor.

  Furthermore, a problem in wet film formation of a low molecular material is that the device characteristics are easily affected by oxygen and moisture. For example, Patent Document 3 describes a method for improving element characteristics by managing the oxygen concentration and the water concentration in the composition for organic electroluminescent elements extremely low. For example, Patent Document 4 describes a method of improving element characteristics by wet-forming an organic layer of an organic electroluminescent element in an inert gas atmosphere. However, in these methods, a complicated process for removing oxygen and moisture from the composition is required, and it is necessary to maintain a special coating environment. There is also a problem that production efficiency is significantly hindered.

  In addition, when a film is formed by a wet film forming method, there is a problem that a composition containing a low molecular compound is repelled and a film is not formed uniformly.

JP-A-4-212286 Japanese Patent Laid-Open No. 11-238359 Japanese Patent Application No. 2006-550738 JP 2003-217840 A

The present invention provides a composition for an organic electroluminescent device comprising a low molecular weight compound and a solvent, and provides a composition that improves the characteristics of the organic electroluminescent device by performing a wet film formation method in an atmospheric environment. Let it be an issue.
The present invention also provides an organic electroluminescent device composition that can be used in the manufacture of an organic electroluminescent device having a low molecular weight organic layer formed by a wet film formation method, and that can reduce manufacturing costs and improve production efficiency. An object of the present invention is to provide an organic electroluminescent element that is inexpensive and has high performance.

As a result of intensive studies, the present inventors have found that in forming an organic electroluminescent element, oxygen in the composition for an organic electroluminescent element is formed when wet deposition of a layer containing a low molecular compound is performed at an oxygen concentration of 1% or more. The inventors have found that the characteristics of the organic electroluminescent device are improved by excessively increasing the concentration and / or the moisture concentration, and have reached the present invention.
That is, the present invention relates to a composition for organic electroluminescent elements comprising a low molecular weight compound and a solvent, wherein the oxygen concentration and / or water concentration is 100 ppm or more. And an organic electroluminescent element formed using the same, and an organic EL display and an organic EL illumination including the organic electroluminescent element.

  The present invention also provides a composition containing a low molecular weight compound and a solvent in a method for producing an organic electroluminescent device having an anode and a cathode, and a plurality of organic layers disposed between the anode and the cathode on a substrate. Organic electroluminescence, characterized in that the composition has an oxygen concentration and / or a water concentration of 100 ppm or more, and is formed by a wet film-forming method using the composition with a volume concentration of oxygen of 1% or more. It exists in the manufacturing method of an element, an organic electroluminescent element, an organic EL display provided with the same, and organic EL illumination.

According to the present invention, in an organic electroluminescent device having a layer containing a low molecular compound formed by a wet film forming method, the composition for organic electroluminescent device having an oxygen concentration and / or a water concentration of 100 ppm or more is used. By using a wet film formation method with an oxygen concentration of 1% or more, light emission unevenness is reduced, and light emission efficiency and drive life are improved.
According to the present invention, when forming an organic layer containing a low molecular weight compound by a wet film forming method, a complicated and / or special environment is not required, and the manufacturing cost can be reduced. It can be set as the manufacturing method of an organic electroluminescent element with high efficiency.

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. It is not specified in the contents.
<Composition for organic electroluminescence device>
The composition of the present invention is a composition for an organic electroluminescent device comprising a low molecular compound and a solvent, wherein the oxygen concentration and / or the water concentration is 100 ppm or more, It is a composition.

[Low molecular compounds]
The low molecular weight compound in the present invention refers to a compound defined by a single molecular weight.
The low molecular weight compound is preferably the following light emitting low molecular weight compound and / or charge transporting low molecular weight compound.
[Luminescent low molecular weight compound]
The composition for organic electroluminescent elements of the present invention contains a light-emitting low molecular compound as a low molecular compound.

The light emitting low molecular compound is not particularly limited as long as it is a compound having a light emitting property defined by a single molecular weight, and a known material can be applied. For example, it may be a fluorescent low molecular weight compound or a phosphorescent low molecular weight compound, but from the viewpoint of internal quantum efficiency, it is preferably a phosphorescent low molecular weight compound.
In order to improve the solubility in a solvent, it is preferable to reduce the symmetry and rigidity of the molecule of the light-emitting low molecular weight compound or to introduce a lipophilic substituent such as an alkyl group.

Hereinafter, examples of the fluorescent light-emitting low molecular compound among the light-emitting low molecular compounds will be described, but the fluorescent light-emitting low molecular compound is not limited to the following examples.
Although the example of a fluorescent light-emitting material is given among light-emitting materials, a fluorescent light-emitting material is not limited to the following illustrations.
Examples of the fluorescent light-emitting material that gives blue light emission (blue fluorescent light-emitting material) include naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis (2-phenylethenyl) benzene, and derivatives thereof.

Examples of the fluorescent light emitting material that gives green light emission (green fluorescent light emitting material) include quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al (C ₉ H ₆ NO) _3, and the like.
Examples of the fluorescent light-emitting material that gives yellow light (yellow fluorescent light-emitting material) include rubrene and perimidone derivatives.

  Examples of fluorescent light-emitting materials (red fluorescent light-emitting materials) that emit red light include, for example, DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) -based compounds, benzopyran derivatives, rhodamine derivatives. Benzothioxanthene derivatives, azabenzothioxanthene and the like.

As the phosphorescent material, for example, a long-period type periodic table (hereinafter referred to as a long-period type periodic table when referred to as “periodic table” unless otherwise specified) is selected from the seventh to eleventh groups. And an organometallic complex containing a metal.
Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

  As the ligand of the complex, a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or a (hetero) arylpyrazole ligand and a pyridine, pyrazole, phenanthroline, or the like is connected is preferable. A pyridine ligand and a phenylpyrazole ligand are preferable. Here, (hetero) aryl represents an aryl group or a heteroaryl group.

  Specific examples of the phosphorescent material include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, tris (2- Phenylpyridine) osmium, tris (2-phenylpyridine) rhenium, octaethyl platinum porphyrin, octaphenyl platinum porphyrin, octaethyl palladium porphyrin, octaphenyl palladium porphyrin, and the like.

  The molecular weight of the compound used as the light emitting material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, Preferably it is 200 or more, More preferably, it is 300 or more, More preferably, it is the range of 400 or more. If the molecular weight of the luminescent material is too small, the heat resistance will be significantly reduced, gas generation will be caused, the film quality will be reduced when the film is formed, or the morphology of the organic electroluminescent element will be changed due to migration, etc. Sometimes come. On the other hand, if the molecular weight of the luminescent material is too large, it tends to be difficult to purify the luminescent material, or it may take time to dissolve in the solvent.

In addition, any 1 type may be used for the luminescent material mentioned above, and 2 or more types may be used together by arbitrary combinations and a ratio.
Specific examples of the light-emitting low molecular compound are shown below, but the present invention is not limited to these. Hex represents a hexyl group.

  <Examples of luminescent low molecular weight compounds>

[Charge transporting low molecular weight compounds]
The composition for organic electroluminescent elements of the present invention preferably contains a charge transporting low molecular weight compound as the low molecular weight compound.
In the present invention, only one kind of charge transporting low molecular weight compound may be used, or two or more kinds may be used in any combination and ratio.

In the light emitting layer, it is preferable to use a light emitting material as a dopant material and a charge transporting low molecular weight compound as a host material.
The charge transporting low molecular weight compound may be a compound that has been conventionally used in a light emitting layer of an organic electroluminescence device, and particularly a compound that is used as a host material of the light emitting layer.
Specific examples of charge transporting low molecular weight compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, and compounds in which tertiary amines are linked by a fluorene group. , Hydrazone compounds, silazane compounds, silanamine compounds, phosphamine compounds, quinacridone compounds, anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, silole compounds Etc.

For example, two or more condensed aromatic rings including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl are substituted with nitrogen atoms. Aromatic amine compounds having a starburst structure (J. Lumin, etc.) such as aromatic diamines (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine, etc. , 72-74, 985, 1997), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 ′, 7, 7 ′. -Fluorene compounds such as tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4'-N, N'- Carbazole compounds such as carbazole biphenyl, 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 2,5-bis (1- Oxadiazole compounds such as naphthyl) -1,3,4-oxadiazole (BND), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3 , 4-diphenylsilol (PyPySPyPy) and other silole compounds, bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin) and other phenanthroline compounds It is done.

Specific examples of the charge transporting low molecular weight compound are shown below, but the present invention is not limited thereto. In the formula, Bu represents a butyl group, and Et represents an ethyl group.
<Examples of charge transporting low molecular weight compounds>

[solvent]
Moreover, a solvent will not be specifically limited if it is a solvent in which a luminescent low molecular weight compound and a charge transporting low molecular weight compound dissolve favorably.
The solubility of the solvent is usually 0.01% by weight or more, preferably 0.05% by weight or more, and more preferably 0% of the light-emitting low-molecular compound and the charge-transporting low-molecular compound at normal temperature and normal pressure, respectively. It is preferable to dissolve 1% by weight or more.

Although the specific example of a solvent is given to the following, as long as the effect of this invention is not impaired, it is not limited to these.
For example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated aroma such as chlorobenzene, dichlorobenzene, and trichlorobenzene Group hydrocarbons: 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethyl Aromatic ethers such as anisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; Alicyclic ketones such as Sanone, Cyclooctanone and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Ethylene And aliphatic ethers such as glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA).

Of these, alkanes and aromatic hydrocarbons are preferable. One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.
In order to obtain a more uniform film, it is preferable that the solvent evaporates from the liquid film immediately after the film formation at an appropriate rate. For this reason, the boiling point of the solvent is usually 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and usually 270 ° C. or lower, preferably 260 ° C. or lower, more preferably 250 ° C. or lower.

  The amount of the solvent used is arbitrary as long as the effect of the present invention is not significantly impaired, but is preferably 10 parts by weight or more, more preferably 50 parts by weight or more, particularly preferably 100 parts by weight or more with respect to 100 parts by weight of the organic electroluminescent element composition. The amount is preferably 80 parts by weight or more, preferably 99.95 parts by weight or less, more preferably 99.9 parts by weight or less, and particularly preferably 99.8 parts by weight or less. When the content is lower than the lower limit, the viscosity becomes too high, and the film forming workability may be lowered. On the other hand, when the value exceeds the upper limit, the film thickness obtained by removing the solvent after film formation cannot be obtained, so that film formation tends to be difficult. In addition, when using 2 or more types of solvents as a composition for organic electroluminescent elements, it is made for the sum total of these solvents to satisfy | fill this range.

Moreover, the composition for organic electroluminescent elements in this invention may contain various additives, such as a leveling agent and an antifoamer, for the purpose of improving film forming property.
<Oxygen concentration / water concentration>
The oxygen concentration of the composition for organic electroluminescent elements of the present invention is usually 100 ppm or more, preferably 500 ppm or more, and usually 10,000 ppm or less, preferably 2000 ppm or less.

Moreover, the water concentration of the composition for organic electroluminescent elements of the present invention is usually 100 ppm or more, preferably 500 ppm or more, and usually 10,000 ppm or less, preferably 2000 ppm or less.
Within the above range, in an environment with an oxygen concentration of 1% or more, the affinity between the ink and the substrate is improved, so that the effect of improving the wettability of the coating film is well expressed, and the storage stability of the ink is improved. Since it does not impair, it is preferable at the point which improves the production efficiency of an organic electroluminescent element.

The composition for an organic electroluminescent element of the present invention uses the following method in order to keep the oxygen concentration or the water concentration within the above specified range.
The oxygen concentration of the composition can be measured by a dissolved oxygen concentration meter (B-506 manufactured by Iijima Electronics Co., Ltd.) and the moisture concentration can be measured by Karl Fischer titration method (CA-200 model manufactured by Mitsubishi Chemical Analytech, etc.).

If the concentration is too low, adjust to the specified concentration by bubbling oxygen or adding pure water. If the concentration is excessive, remove it by bubbling with an inert gas such as nitrogen, adding and mixing molecular sieves, or degassing with a porous hollow fiber separation membrane module (such as Nittoep manufactured by Nitto Denko). Prepare until.
<Method for producing organic electroluminescent element>
The method for producing an organic electroluminescent device of the present invention is a method for producing an organic electroluminescent device having an anode and a cathode and a plurality of organic layers disposed between the anode and the cathode on a substrate. And the composition has an oxygen concentration and / or moisture concentration of 100 ppm or more, and is formed by a wet film formation method in an environment where the volume concentration of oxygen is 1% or more using the composition. A method for producing an organic electroluminescent element, characterized in that:

The low molecular compound and the solvent are the same as those described in the above section [Low molecular compound]. The preferred examples are also the same.
In the method for producing an organic electroluminescent element of the present invention, the oxygen concentration in the wet film formation method is usually 1%.
Above, preferably 10% or more, more preferably 18% or more, and usually 25% or less, preferably 22% or less.

The relative humidity is usually 10% or more, preferably 30% or more, and usually 70% or less, preferably 50% or less.
Within the above range, adsorbed oxygen and adsorbed water are appropriately present on the surface of the organic electroluminescent element substrate, which is preferable in terms of improving coating uniformity.
The method for producing an organic electroluminescent element of the present invention is performed by appropriately combining the following conditions using a composition for organic electroluminescent element having a water concentration and / or an oxygen concentration of 100 ppm or more.

After application by the wet film forming method, the drying treatment step is usually started within 60 seconds, preferably within 30 seconds, more preferably within 10 seconds.
The drying process is usually performed under reduced pressure, and the ultimate vacuum is usually 1 Torr or less, preferably 0.1 Torr or less, more preferably 0.01 Torr or less. The decompression time is usually 10 seconds or longer, preferably 20 seconds or longer, more preferably 30 seconds or longer, and usually 180 seconds or shorter, preferably 120 seconds or shorter, more preferably 60 seconds or shorter.

After the decompression step is completed, a gas purge for restoring the pressure to the atmospheric pressure is performed using an inert gas such as nitrogen or argon. The purge time is usually 1 second or longer, preferably 2 seconds or longer, more preferably 5 seconds or longer, and usually 60 seconds or shorter, preferably 40 seconds or shorter, more preferably 20 seconds or shorter.
After the drying process, heat treatment is performed in vacuum or in an inert gas such as nitrogen or argon. The heating temperature is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 140 ° C. or higher, and usually 230 ° C. or lower, preferably 210 ° C. or lower, more preferably 190 ° C. or lower. The heating time is usually 1 minute or longer, preferably 5 minutes or longer, more preferably 10 minutes or longer, and usually 120 minutes or shorter, preferably 60 minutes or shorter, more preferably 30 minutes or shorter. Examples of the heating method include a hot plate method, a convection oven method, an infrared heater method, an induction heating method, and a dielectric heating method.

After completion of the reduced-pressure drying process, the vacuum deposition process is performed without returning to atmospheric pressure. There may be a vacuum heating step before the vacuum deposition step.
There may be a UV ozone treatment step or a plasma etching treatment step after the drying treatment step or the heat treatment step.
After the drying treatment step or the heat treatment step, there may be a storage step in vacuum or in an inert gas such as nitrogen or argon. The storage time is usually 10 minutes or longer, preferably 30 minutes or longer, more preferably 180 minutes or longer, and usually 90 hours or shorter, preferably 30 hours or shorter, more preferably 10 hours or shorter.

<Organic electroluminescent device>
Below, the layer structure of the organic electroluminescent element manufactured with the method of this invention, its general formation method, etc. are demonstrated with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device according to the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 Represents a light-emitting layer, 6 represents a hole blocking layer, 7 represents an electron transport layer, 8 represents an electron injection layer, and 9 represents a cathode.

(substrate)
The substrate serves as a support for the organic electroluminescence device, and quartz or glass plates, metal plates or metal foils, plastic films, sheets, or the like are used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

(anode)
The anode 2 serves to inject holes into the layer on the light emitting layer side.
This anode 2 is usually made of a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide,
It is composed of carbon black or a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline.

  In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. When forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., an appropriate binder resin solution It is also possible to form the anode 2 by dispersing it and applying it onto the substrate. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate (Appl. Phys. Lett., 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.

For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the surface of the anode 2 is subjected to ultraviolet (UV) / ozone treatment, oxygen plasma, argon plasma treatment, etc. It is preferable to do.
(Hole injection layer)
The hole injection layer is a layer that transports holes from the anode 2 to the light emitting layer, and is usually formed on the anode 2.

The method for forming the hole injection layer according to the present invention may be a vacuum vapor deposition method or a wet film formation method, and is not particularly limited. However, from the viewpoint of reducing dark spots, the hole injection layer may be formed by a wet film formation method. preferable.
The thickness of the hole injection layer is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When the hole injection layer is formed by wet film formation, the material for forming the hole injection layer is usually mixed with an appropriate solvent (hole injection layer solvent) to form a composition for film formation (hole injection). Layer forming composition), and applying this hole injection layer forming composition onto a layer corresponding to the lower layer of the hole injection layer (usually an anode) by an appropriate technique, A hole injection layer is formed by drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer.
As long as the hole transporting compound is a compound having a hole transporting property, which is usually used in a hole injection layer of an organic electroluminescence device, a monomer or the like may be a polymer compound or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

  The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer. Examples of hole transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by a fluorene group, hydrazone derivatives, silazane derivatives, silanamines Derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

In the present invention, the derivative includes, for example, an aromatic amine derivative and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.
The hole transporting compound used as the material for the hole injection layer may contain any one of these compounds alone, or may contain two or more. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two other hole transporting compounds are used. It is preferable to use the above in combination.

Among the above-mentioned examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.
The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

(In Formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Represents a linking group selected from the group of linking groups, and among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > represents each independently the aromatic hydrocarbon group which may have a substituent, or the aromatic heterocyclic group which may have a substituent. R ¹ and R ² each independently represents a hydrogen atom or an arbitrary substituent.))
As the aromatic hydrocarbon group and the aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ , a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport property of the polymer compound A group derived from a ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.
When R ¹ and R ² are optional substituents, examples of the substituent include an alkyl group, an alkenyl group, an alkoxy group, a silyl group, a siloxy group, an aromatic hydrocarbon group, and an aromatic heterocyclic group. .

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (I) include those described in International Publication No. 2005/089024.
In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), which is a polythiophene derivative, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably in terms of film thickness uniformity. Is 0.1% by weight or more, more preferably 0.5% by weight or more, and usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The hole injection layer 3 preferably contains an electron-accepting compound, and therefore the hole-injection layer composition preferably also contains an electron-accepting compound. As the electron-accepting compound, a compound having an oxidizing power and an ability to accept one electron from the above-described hole-transporting compound is preferable. Specifically, a compound having an electron affinity of 4 eV or more is preferable, and a compound of 5 eV or more is more preferable.

Examples of the electron-accepting compound include a triaryl boron compound, a metal halide, a Lewis acid, an organic acid, an onium salt, a salt of an arylamine and a metal halide, and a salt of an arylamine and a Lewis acid. 1 type, or 2 or more types of compounds etc. chosen from are mentioned. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate or triphenylsulfonium tetrafluoroborate (WO 2005/089024) High-valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067) and ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds; fullerene derivatives; iodine and the like. In addition, only 1 type may be used for an electron-accepting compound, and 2 or more types may be used together by arbitrary combinations and arbitrary ratios.

Since these electron accepting compounds oxidize the hole transporting compound, the conductivity of the hole injection layer 3 can be improved.
The content of the electron-accepting compound with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(solvent)
At least one of the solvents contained in the hole injection layer composition is preferably a solvent capable of dissolving the material of the hole injection layer 3.
Moreover, the boiling point of a solvent is 110 degreeC or more normally, Preferably it is 140 degreeC or more, More preferably, it is 200 degreeC or more, and is 400 degrees C or less normally, Preferably it is 300 degrees C or less. If the boiling point of the solvent is too low, the drying rate of the formed film is high and the film quality may deteriorate. Moreover, if the boiling point of the solvent is too high, the temperature of the drying process increases, which may adversely affect other layers 2 and the substrate 1 (for example, a glass substrate).

  Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents and the like. Specifically, examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3- And aromatic ethers such as dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole. Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate. Further, examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-iropropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Etc. Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like. In addition, dimethyl sulfoxide and the like can also be used as a solvent.

Among the solvents described above, a solvent having a high ability to dissolve the material of the hole injection layer 3 (dissolution ability) or a high affinity with the material is preferable. This is because a composition having a concentration excellent in the efficiency of the film forming process can be prepared by arbitrarily setting the concentration of the composition for the hole injection layer.
In addition, 1 type may be used for a solvent and it may use 2 or more types together by arbitrary combinations and arbitrary ratios.

(Other ingredients)
As a material of the hole injection layer 3, other components may be further contained in addition to the hole transporting compound and the electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and arbitrary ratios.

(Film formation method)
After preparing the composition for the hole injection layer, this composition is applied onto the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by a wet film formation method, and dried to dry the hole. The injection layer 3 is formed. After the application, it is usually dried by heating or the like. The heating means used in the heating step is not limited as long as the effects of the present invention are not significantly impaired. Examples of the heating means include a clean oven, a hot plate, infrared rays, a halogen heater, and microwave irradiation. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film. However, when the composition for hole injection layers contains the arylamine polymer of the present invention, crosslinking is performed after coating.

In the case of forming a layer by a vacuum deposition method, first, one or more materials (hole transporting compound, electron accepting compound, etc.) are put in a crucible installed in a vacuum vessel (two or more types). When using the material, put it in each crucible), and evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with an appropriate vacuum pump. Then, the crucible is heated (each crucible is heated when two or more materials are used), and the evaporation amount is controlled to evaporate (when two or more materials are used, the evaporation amount is controlled independently). The hole injection layer 3 is formed on the anode of the substrate placed facing the crucible. When two or more kinds of materials are used, a mixture thereof can be put in a crucible, heated and evaporated to be used for forming the hole injection layer 3.

The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. If the film thickness is too thin, the hole injection ability may be insufficient, and if it is too thick, the resistance may be increased.
The hole injection layer 3 may have a single layer structure, or may have a structure in which a plurality of layers are stacked. In the latter case, the plurality of layers may be layers made of the same material or layers made of different materials.
[Hole transport layer]
The formation method of the hole transport layer according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole transport layer may be formed by a wet film formation method from the viewpoint of reducing dark spots. preferable.

The hole transport layer can be formed on the hole injection layer when there is a hole injection layer and on the anode 2 when there is no hole injection layer. The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.
The material for forming the hole transport layer is preferably a material having high hole transportability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, since it is in contact with the light emitting layer, it is preferable not to quench the light emitted from the light emitting layer or to reduce the efficiency by forming an exciplex with the light emitting layer.

As a material of such a hole transport layer, any material that has been conventionally used as a constituent material of a hole transport layer may be used. What was illustrated is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatics Group derivatives and metal complexes.

  Also, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of an alternating copolymer, a random polymer, a block polymer, or a graft copolymer. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.

Of these, polyarylamine derivatives and polyarylene derivatives are preferred.
The polyarylamine derivative is preferably a polymer containing a repeating unit represented by the following formula (II). In particular, the polymer is preferably a polymer composed of a repeating unit represented by the following formula (II). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In Formula (II), Ar ^a and Ar ^b each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)
Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, and an acenaphthene. Examples thereof include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, a fluorene ring, and a group in which two or more rings are connected by a direct bond.

  Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine Ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. Or a group and the rings of from 2-4 fused rings include groups formed by connecting a direct bond or two or more rings.

In view of solubility and heat resistance, Ar ^a and Ar ^b are each independently selected from the group consisting of a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, and fluorene ring. A group derived from a selected ring or a group formed by linking two or more benzene rings (for example, a biphenyl group or a terphenyl group) is preferable.
Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.

Examples of the substituent that the aromatic hydrocarbon group and the aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II) is used as its repeating unit. The polymer which has is mentioned.
As a polyarylene derivative, the polymer which has a repeating unit which consists of following formula (III-1) and / or following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In Formula (III-2), R ^e and R ^f are each independently the same as R ^a , R ^b , R ^c or R ^d in Formula (III-1) above. Independently, it represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R ^f may form a ring, and X represents an atom or a group of atoms constituting a 5-membered ring or a 6-membered ring.)
Specific examples of X include an oxygen atom, a boron atom which may have a substituent, a nitrogen atom which may have a substituent, a silicon atom which may have a substituent, and a substituent. A phosphorus atom which may be substituted, a sulfur atom which may have a substituent, a carbon atom which may have a substituent, or a group formed by bonding these.

  The polyarylene derivative has a repeating unit represented by the following formula (III-3) in addition to the repeating unit represented by the following formula (III-1) and / or the following formula (III-2). Is preferred.

(In the formula (III-3), Ar ^{c to} Ar ^j each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent. Independently represents 0 or 1.)
Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (II).

Specific examples of the above formulas (III-1) to (III-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.
When the hole transport layer is formed by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer, followed by heat drying after the wet film formation.
The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. The film forming conditions, heat drying conditions, and the like are the same as in the case of forming the hole injection layer.

When the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as those in the case of forming the hole injection layer.
The hole transport layer may contain various light emitting materials, electron transport compounds, binder resins, coatability improvers, and the like in addition to the hole transport compound.
The hole transport layer may also be a layer formed by crosslinking a crosslinkable compound. The crosslinkable compound is a compound having a crosslinkable group, and forms a network polymer compound by crosslinking.

Examples of this crosslinkable group include groups derived from cyclic ethers such as oxetane and epoxy; groups derived from unsaturated double bonds such as vinyl, trifluorovinyl, styryl, acrylic, methacryloyl and cinnamoyl; benzo Examples include groups derived from cyclobutene.
The crosslinkable compound may be any of a monomer, an oligomer, and a polymer. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of the hole transporting compound include those exemplified above, and those having a crosslinkable group bonded to the main chain or side chain with respect to these hole transporting compounds. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole transporting compound is preferably a polymer containing a repeating unit having a crosslinkable group, and the above formula (II) and formulas (III-1) to (III-3) are represented by a crosslinkable group. Is preferably a polymer having a repeating unit bonded directly or via a linking group.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of hole transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; triphenylamine derivatives Silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. Particularly preferred are triphenylamine derivatives.

In order to form a hole transport layer by crosslinking a crosslinkable compound, a composition for forming a hole transport layer in which a crosslinkable compound is dissolved or dispersed in a solvent is usually prepared and formed by wet film formation. Crosslink.
The composition for forming a hole transport layer may contain an additive for promoting a crosslinking reaction in addition to the crosslinking compound. Examples of additives that accelerate the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds.

Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound; a binder resin;
In the composition for forming a hole transport layer, the crosslinkable compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20%. It is contained by weight% or less, more preferably 10% by weight or less.

After forming a composition for forming a hole transport layer containing a crosslinkable compound at such a concentration on a lower layer (usually a hole injection layer), the crosslinkable compound is formed by heating and / or irradiation with electromagnetic energy such as light. A network polymer compound is formed by crosslinking.
Conditions such as temperature and humidity during film formation are the same as those during wet film formation of the hole injection layer.
The heating method after film formation is not particularly limited. As heating temperature conditions, it is 120 degreeC or more normally, Preferably it is 400 degrees C or less.

The heating time is usually 1 minute or longer, preferably 24 hours or shorter. The heating means is not particularly limited, and means such as placing a laminated body having a deposited layer on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.
In the case of irradiation with electromagnetic energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp or an infrared lamp, or the above-mentioned light source is incorporated. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In electromagnetic energy irradiation other than light, for example, there is a method of irradiation using a device that irradiates a microwave generated by a magnetron, a so-called microwave oven. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

Heating and irradiation of electromagnetic energy such as light may be performed individually or in combination. When combined, the order of implementation is not particularly limited.
The film thickness of the hole transport layer thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.
(Light emitting layer 5)
When the hole injection layer 3 or the hole transport layer 4 is provided, the light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between the electrodes 2 and 9 to which an electric field is applied, and becomes a main light emitting source. is there.

The light emitting layer 5 can use the material described in the above-mentioned [Low molecular compound] as a constituent material. The preferred examples are also the same.
-Formation method of the light emitting layer 5 The light emitting layer 5 is normally formed by the wet film-forming method. In this case, the above-mentioned material is dissolved in an appropriate solvent (light emitting layer solvent) to prepare a light emitting layer composition, and the composition is applied and dried. Moreover, you may make it bridge | crosslink after application | coating as needed. Film formation, drying, crosslinking, and the like may be performed in the same manner as the hole injection layer 3 and the hole transport layer 4.

  As a solvent for forming the light emitting layer 5 by a wet film forming method, any solvent can be used as long as the light emitting layer 5 can be formed. However, those capable of dissolving the light emitting material, the hole transporting compound, and the electron transporting compound are preferable. Specifically, the solubility of the light-emitting material, the hole transporting compound or the electron transporting compound is usually 0.01% by weight or more, particularly 0.05% by weight or more, particularly 0.1% at room temperature and normal pressure. It is preferable to dissolve by weight% or more.

Suitable examples of the solvent for the light emitting layer include the same solvents as those contained in the composition for organic electroluminescent elements. In addition, the solvent for light emitting layers may use 1 type, and may use 2 or more types together by arbitrary combinations and arbitrary ratios.
The ratio of the solvent for the light emitting layer to the composition for the light emitting layer is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.8%. It is 5% by weight or more, usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. In addition, when mixing and using 2 or more types of solvents as a solvent for light emitting layers, it is made for the sum total of these solvents to satisfy | fill this range.

In the wet film forming method, the light emitting layer 5 is usually formed by drying the coating film obtained after applying the composition for the light emitting layer and removing the solvent for the light emitting layer. The method of the wet film forming method is not limited as long as the effect of the present invention is not significantly impaired, and any of the methods described above can be used.
In addition, when forming another organic layer with the wet film-forming method based on this invention, you may use a vapor deposition method or another method for formation of the light emitting layer 5. FIG.

The thickness of the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the thickness of the light emitting layer 5 is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.
(Hole blocking layer 6)
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. Have
The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high. Examples of the material for the hole blocking layer satisfying such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Mixed ligand complexes of: metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes; distyryl biphenyl derivatives Styryl compounds (JP-A-11-242996); Triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (JP-A-7 -41759); phenanthroline derivatives such as bathocuproine (JP-A-10-79297) and the like. That. Further, a compound having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005-022962 is also preferable as a material for the hole blocking layer.

In addition, the material of the hole-blocking layer 6 may use 1 type, and may use 2 or more types together by arbitrary combinations and arbitrary ratios.
There is no restriction | limiting in the formation method of the hole-blocking layer 6. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The thickness of the hole blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less. If the hole blocking layer 6 is too thin, the light emission efficiency may be reduced due to insufficient hole blocking capability. If the hole blocking layer 6 is too thick, the voltage of the device may be increased.

(Electron transport layer 7)
An electron transport layer 7 may be provided between the light emitting layer 5 and an electron injection layer 8 described later.
The electron transport layer 7 has a role of further improving the light emission efficiency of the device.
The physical properties required of the material constituting the electron transport layer 7 include that electrons injected from the cathode 9 can be efficiently transported in the direction of the light emitting layer 5 between the electrodes 2 and 9 to which an electric field is applied. . Examples of the material that satisfies such conditions include an electron transporting compound. Among them, usually, a compound that has high electron injection efficiency from the cathode 9 or the electron injection layer 8 and has high electron mobility and can efficiently transport injected electrons is used. Examples thereof include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, distyrylbiphenyl derivatives, Silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds (JP-A-6-207169) Publication), phenanthroline derivative (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, Examples include n-type zinc selenide.

In addition, the material of the electron carrying layer 7 may use 1 type, and may use 2 or more types together by arbitrary combinations and arbitrary ratios.
There is no restriction | limiting in the formation method of the electron carrying layer 7. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The film thickness of the electron transport layer 7 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

(Electron injection layer 8)
The electron injection layer 8 is a layer that plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function.
Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. In this case, the thickness of the electron injection layer 8 is preferably 0.1 nm or more and 5 nm or less.

  Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

In addition, the material of the electron injection layer 8 may use 1 type, and may use 2 or more types together by arbitrary combinations and arbitrary ratios.
There is no restriction | limiting in the formation method of the electron injection layer 8. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
(Cathode 9)
The cathode 9 plays a role of injecting electrons into a layer on the light emitting layer 5 side (such as the electron injection layer 8 or the light emitting layer 5).

  The material of the cathode 9 can be the same as the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection. For example, a suitable metal such as tin, magnesium, indium, calcium, aluminum, silver, or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

In addition, the material of the cathode 9 may use 1 type, and may use 2 or more types together by arbitrary combinations and arbitrary ratios.
The film thickness of the cathode 9 is usually the same as that of the anode 2.
Furthermore, for the purpose of protecting the cathode 9 made of a low work function metal, if a metal layer (not shown) having a high work function and stable to the atmosphere is further laminated thereon, the stability of the device is increased. preferable. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may use 1 type and may use 2 or more types together by arbitrary combinations and arbitrary ratios.

(Other layers)
The organic electroluminescent element according to the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 9 in addition to the layers 3 to 8 described above, and the optional layer is omitted. May be.

  Examples of the layer that may be included include an electron blocking layer. The electron blocking layer is a layer provided between the hole injection layer 3 or the hole transport layer 4 and the light emitting layer 5. This electron blocking layer prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3 or the hole transport layer 4, thereby recombining holes and electrons in the light emitting layer 5. It plays a role of increasing the probability and confining the generated excitons in the light emitting layer 5 and efficiently transporting holes injected from the hole injection layer 3 in the direction of the light emitting layer 5. In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting material, it is effective to provide an electron blocking layer.

  The characteristics required for the material of the electron blocking layer include a high hole transport ability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, when the light emitting layer 5 is produced by a wet film formation method, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260).

In addition, the material of an electron blocking layer may use 1 type, and may use 2 or more types together by arbitrary combinations and arbitrary ratios.
There is no restriction | limiting in the formation method of an electron blocking layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
Further, at the interface between the cathode 9 and the light emitting layer 5 or the electron transport layer 7, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ). It is also an effective method to improve the efficiency of the element to insert an ultrathin insulating film (thickness is usually 0.1 nm to 5 nm) formed by the method (Applied Physics Letters, 199).
7 years, Vol. 70, pp. 152; Japanese Patent Laid-Open No. 10-74586; IEEE Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04
Digest, pp. 154 etc.).

Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than the board | substrate 1 in reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate 1 are the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, the positive layer. The hole injection layer 3 and the anode 2 may be provided in this order.
Furthermore, the organic electroluminescent element according to the present invention can be configured by, for example, laminating components other than the substrate between two substrates, at least one of which is transparent.

Further, for example, a structure in which a plurality of components (light emitting units) other than the substrate are stacked (a structure in which a plurality of light emitting units are stacked) may be used. In that case, instead of the interface layer between the steps (between the light emitting units) (in the case where the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like. When a generation layer (Carrier Generation Layer: CGL) is provided, the barrier between the stages is reduced, which is more preferable from the viewpoint of luminous efficiency and driving voltage.

Furthermore, the organic electroluminescent element may be configured as a single organic electroluminescent element, or may be applied to a configuration in which a plurality of organic electroluminescent elements are arranged in an array, and the anode and the cathode are X- You may apply to the structure arrange | positioned at Y matrix form.
In addition, each of the layers 1 to 9 described above may contain components other than those described as materials as long as the effects of the present invention are not significantly impaired.

<Organic EL display and organic EL lighting>
The organic EL display and the organic EL illumination of the present invention are provided with the organic electroluminescent element of the present invention as described above. There is no restriction | limiting in particular about the model and structure of an organic electroluminescent display, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.
For example, the organic EL display and the organic EL display of the present invention can be obtained by the method described in “Organic EL display” (Ohm, August 20, 2004, published by Shizushi Tokito, Chiba Adachi, Hideyuki Murata). EL illumination can be formed.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
[Preparation of composition for light emitting layer]
Example 1
Using the charge transporting low molecular weight compound (C1) and the light emitting low molecular weight compound (D1) shown below, a light emitting layer composition was prepared under the following conditions.

<Composition for light emitting layer>
Solvent cyclohexylbenzene
Composition concentration (C1): 3.2% by weight
(D1): 0.32% by weight
<Environment during preparation of composition for light emitting layer>
Temperature 23 ° C
Relative humidity 40%
Oxygen concentration 21%

The amount of water contained in the composition for the light emitting layer obtained as described above was measured with a Karl Fischer moisture meter (CA-21 model manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The results are shown in Table 1.
(Example 2)
A composition for a light emitting layer was prepared in the same manner as in Example 1 except that the light emitting low molecular compound (D2) shown below was used.

<Composition for light emitting layer>
Solvent cyclohexylbenzene
Composition concentration (C1): 3.2% by weight
(D2): 0.32% by weight

The water content contained in the composition for the light emitting layer obtained as described above was measured in the same manner as in Example 1. The results are shown in Table 1.
Example 3
A light emitting layer composition was prepared in the same manner as in Example 1 except that the following charge transporting low molecular weight compounds (C2 and C3) and light emitting low molecular weight compound (D3) were used.
<Composition for light emitting layer>
Solvent cyclohexylbenzene
Composition concentration (C2): 3.7% by weight
(C3): 1.2% by weight
(D3): 0.5% by weight

The water content contained in the composition for the light emitting layer obtained as described above was measured in the same manner as in Example 1. The results are shown in Table 1.
(Comparative Example 1)
In Example 1, the environment at the time of preparing the composition for the light emitting layer was in a glove box under a nitrogen atmosphere, except that the temperature was 25 ° C., the moisture concentration in the gas phase and the oxygen concentration were both 1 ppm or less. The composition for the light emitting layer was prepared in the same manner as in Example 1, and the moisture concentration in the composition was measured. The measurement results are shown in Table 1.

(Comparative Example 2)
In Example 2, the environment at the time of preparing the composition for the light emitting layer was in a glove box under a nitrogen atmosphere, except that the temperature was 25 ° C., the moisture concentration in the gas phase and the oxygen concentration were both 1 ppm or less. The composition for light emitting layers was prepared similarly to 2, and the moisture concentration in the composition was measured. The measurement results are shown in Table 1.

(Comparative Example 3)
In Example 3, the environment at the time of preparing the composition for the light emitting layer was in a glove box under a nitrogen atmosphere, except that the temperature was 25 ° C., and the moisture concentration and oxygen concentration in the gas phase were both 1 ppm or less. The composition for the light emitting layer was prepared in the same manner as in Example 3, and the moisture concentration in the composition was measured. The measurement results are shown in Table 1.

[Production of organic electroluminescence device]
Example 4
The organic electroluminescent element shown in FIG. 1 was produced.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate to a thickness of 120 nm (manufactured by Sanyo Vacuum Co., Ltd., sputtered film) using ordinary photolithography technology and hydrochloric acid etching An anode was formed by patterning into a stripe having a width of 2 mm. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with an aqueous surfactant solution, water cleaning with ultrapure water, ultrasonic cleaning with ultrapure water, and water cleaning with ultrapure water, followed by drying with compressed air, and finally UV irradiation. Ozone cleaning was performed.

  First, a hole transporting polymer compound having a repeating structure represented by the following structural formula (P1) (weight average molecular weight: 26500, number average molecular weight: 12000), 4-isopropyl-4′- represented by the structural formula (A1) A composition for a hole injection layer containing methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and ethyl benzoate was prepared. This composition was formed on the anode by spin coating under the following conditions to obtain a hole injection layer having a thickness of 30 nm.

<Composition for hole injection layer>
Solvent ethyl benzoate
Composition concentration (P1): 2.0% by weight
(A1): 0.8% by weight
<Film formation conditions for hole injection layer>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In air (temperature 23 ° C, oxygen concentration 21%, relative humidity 40
%)
Heating conditions Atmosphere 230 ° C 3 hours
Subsequently, a composition for forming a crosslinked film containing a crosslinkable polymer (H1) (weight average molecular weight: 76000) represented by the following structural formula is prepared, applied by the spin coat method under the following conditions, and heated. Crosslinking was performed to form a crosslinked film having a thickness of 20 nm (corresponding to a hole transport layer).

<Composition for forming crosslinked film>
Solvent cyclohexylbenzene
Solid content concentration 0.4% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In nitrogen
Heating conditions In nitrogen, 230 ° C, 1 hour
Next, using the composition for light emitting layer prepared in Example 1, a light emitting layer and a mixed layer were obtained by spin coating on a crosslinked film under the following conditions. The light emitting layer has a thickness of 40 nm when formed on a glass plate.

<Deposition conditions for light emitting layer>
Spinner speed 1200rpm
Spinner rotation time 30 seconds
Spin coat atmosphere In air (temperature 23 ° C, oxygen concentration 21%, relative humidity 40%)
Heating conditions Under reduced pressure (0.1 MPa), 130 ° C., 1 hour
Here, the substrate on which the light-emitting layer was formed was transferred into an organic layer deposition apparatus, evacuated until the degree of vacuum in the apparatus became 2.4 × 10 ⁻⁴ Pa or less, and then the compound (C4) shown below Were stacked by a vacuum deposition method to obtain a hole blocking layer. The vapor deposition rate was controlled in the range of 0.7 to 0.8 kg / second, and a hole blocking layer having a thickness of 10 nm was formed by laminating on the light emitting layer. The degree of vacuum at the time of vapor deposition was 2.4 to 2.7 × 10 ⁻⁴ Pa.

Subsequently, the following Alq ₃ (C5) was heated and evaporated to form an electron transport layer. The degree of vacuum during deposition is 0.4 to 1.6 × 10 ⁻⁴ Pa, the deposition rate is controlled in the range of 1.0 to 1.5 Å / sec, and the film is stacked on the hole blocking layer to a thickness of 20 nm. The electron transport layer was formed.

Here, the element that had been deposited up to the electron transport layer was transferred to a cathode deposition apparatus, and a 2 mm wide stripe shadow mask was brought into close contact with the element so as to be orthogonal to the ITO ITO stripe as a mask for cathode deposition. .
As an electron injection layer, first, lithium fluoride (LiF) was controlled at a deposition rate of 0.1 to 0.4 liter / second and a degree of vacuum of 3.2 to 6.7 × 10 ⁻⁴ Pa using a molybdenum boat. A film having a thickness of 0.5 nm was formed on the electron transport layer. Next, aluminum as a cathode is similarly heated by a molybdenum boat and controlled at a deposition rate of 0.7 to 5.3 liters / second and a degree of vacuum of 2.8 to 11.1 × 10 ⁻⁴ Pa. An aluminum layer was formed. The substrate temperature during the above two-layer deposition was kept at room temperature.

Subsequently, in order to prevent the element from being deteriorated by moisture in the atmosphere during storage, sealing treatment was performed by the method described below.
In a nitrogen glove box, a photocurable resin (30Y-437 manufactured by ThreeBond Co., Ltd.) with a width of about 1 mm is applied to the outer periphery of a 23 mm × 23 mm size glass plate, and a moisture getter sheet (manufactured by Dynic) is applied to the center. Was installed. On this, the board | substrate which completed cathode formation was bonded together so that the vapor-deposited surface might oppose a desiccant sheet. Thereafter, only the region where the photocurable resin was applied was irradiated with ultraviolet light to cure the resin.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The luminance half life of this device is shown in Table 2.
(Example 5)
In Example 4, an organic electroluminescent element was produced in the same manner as in Example 4 except that the atmosphere of the spin coat at the time of forming the crosslinked film was changed to the atmosphere. The luminance half life of this device is shown in Table 2.

(Example 6)
An organic electroluminescent element was produced in the same manner as in Example 5 except that the composition for the light emitting layer in Example 5 was changed to the composition prepared in Example 2. The luminance half life of this device is shown in Table 2.
(Example 7)
In Example 5, the organic electroluminescence device was the same as Example 5 except that the composition for the light emitting layer was the composition prepared in Example 3 and the spinner rotation speed during film formation of the light emitting layer was 1500 rpm. Was made. The luminance half life of this device is shown in Table 2.

(Comparative Example 4)
In Example 4, an organic electroluminescent element was produced in the same manner as in Example 4 except that the light-emitting layer film formation environment was in nitrogen. The luminance half life of this device is shown in Table 2.
(Comparative Example 5)
In Example 6, an organic electroluminescent element was produced in the same manner as in Example 6 except that the environment for forming the crosslinked film and the light emitting layer was in nitrogen. The luminance half life of this device is shown in Table 2.

(Comparative Example 6)
In Example 7, an organic electroluminescent element was produced in the same manner as in Example 7 except that the environment for forming the crosslinked film and the light emitting layer was in nitrogen. The luminance half life of this device is shown in Table 2.

  The present invention relates to various fields in which organic electroluminescent elements are used, for example, light sources (for example, light sources of copiers, flat panel displays (for example, for OA computers and wall-mounted televisions) and surface light emitters). It can be suitably used in the fields of liquid crystal displays and backlights of instruments), display panels, indicator lamps and the like.

1 Substrate
2 Anode
3 Hole injection layer
4 hole transport layer
5 Light emitting layer
6 Hole blocking layer
7 Electron transport layer
8 Electron injection layer
9 Cathode

Claims (8)

  An organic electroluminescent element composition comprising a low molecular weight compound and a solvent, wherein the oxygen concentration and / or the water concentration is 100 ppm or more.   The composition for an organic electroluminescent element according to claim 1, wherein the low molecular compound is a light emitting low molecular compound. On a substrate, in an organic electroluminescent device manufacturing method having an anode and a cathode, and a plurality of organic layers disposed between the anode and the cathode,
A composition containing a low molecular compound and a solvent,
The oxygen concentration and / or water concentration of the composition is 100 ppm or more,
A method for producing an organic electroluminescent element, characterized in that the composition is formed by a wet film-forming method in an environment where the volume concentration of oxygen is 1% or more.   The method for producing an organic electroluminescent element according to claim 4, wherein the wet film-forming method is performed in an environment having a relative humidity of 10% or more.   The organic electroluminescent element according to claim 1 or 2, wherein at least one of the organic layers has an anode and a cathode on the substrate, and an organic layer disposed between the anode and the cathode. An organic electroluminescent device, wherein the organic electroluminescent device is an organic layer formed of a material.   An organic electroluminescent device manufactured by the method for manufacturing an organic electroluminescent device according to claim 3.   An organic EL display comprising the organic electroluminescent element according to claim 5.   An organic EL illumination comprising the organic electroluminescent element according to claim 5.

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