JP5577685B2 - Organic electroluminescent device manufacturing method, organic electroluminescent device, organic EL display device, and organic EL illumination - Google Patents

Description

  The present invention relates to a method for manufacturing an organic electroluminescent element having high luminous efficiency and driving stability, the manufactured organic electroluminescent element, an organic EL display device including the organic electroluminescent element, and organic EL lighting.

In recent years, an electroluminescent element (organic electroluminescent element) using an organic thin film has been developed. Examples of the method for forming the organic thin film include a vacuum deposition method and a wet film forming method. Among these, the wet film-forming method does not require a vacuum process, is easy to increase in area, and can easily mix a plurality of materials having various functions into one layer (coating liquid). There are advantages.
Polymer materials such as poly (p-phenylene vinylene) derivatives and polyfluorene derivatives are mainly used as the material for the light emitting layer formed by the wet film forming method. There's a problem.

・ It is difficult to control the degree of polymerization and molecular weight distribution of polymer materials.
・ During continuous driving, degradation occurs due to residues at the molecular ends of the polymer material that is the active site.
・ High purity of the material itself is difficult and contains impurities.
Due to the above problems, the organic electroluminescence device by the wet film forming method is inferior in driving stability to the organic electroluminescence device by the vacuum deposition method and has not reached a practical level except for a part.

As an attempt to solve the above problems, Patent Document 1 uses an organic thin film formed by a wet film-forming method by mixing a plurality of low-molecular materials (charge transport materials, light-emitting materials), not a polymer compound. Organic electroluminescent devices are described.
Moreover, in the organic electroluminescent element using the organic thin film which consists of a several low molecular material formed by the wet film forming method, in order to raise the luminous efficiency of an organic electroluminescent element in a nonpatent literature 1 and patent document 2, An element using a phosphorescent material is described. In particular, in Patent Document 2, an element is formed using a compound containing an arylamine and a carbazole ring, but there is a problem that the driving life is short. In addition, as described in Patent Documents 3 and 4, in an organic electroluminescent device manufactured using a wet film formation method, oxygen and moisture in a coating environment adversely affect the device. It was considered desirable to produce in an inert gas. However, there was a problem in manufacturing cost.

Japanese Patent Laid-Open No. 11-238359 JP 2007-110093 A JP 2002-170676 A Japanese Patent No. 4112800

Japanese Journal of Applied Physics Vol.44, No.1B, 2005, pp. 626-629

The present invention relates to a light emitting material, a charge transport material comprising a triarylamine partial structure及beauty mosquitoes carbazole ring, and the production of organic electroluminescent device having a light-emitting layer which is formed using the light-emitting layer forming composition containing a solvent An object of the present invention is to provide an element having a long driving life.
Another object of the present invention is to provide an organic electroluminescent device having a long driving life at a low production cost.

The present inventors have a result of intensive studies, the light emitting material, by using a charge transport material comprising a triarylamine structure及beauty mosquitoes carbazole ring within the molecule, and a composition containing a solvent, forming an organic layer by a wet film-forming method In the method of manufacturing an organic electroluminescent element including the step of: solving the above-mentioned problem by setting the environment for forming the coating film by wet film formation and the environment for heating the coating film as specific conditions. As a result, the present invention has been reached.

（上記式中、Ａｒ ^２１ は、置換基を有していてもよい芳香族環基を表し、Ａｒ ^２２ およびＡｒ ^２３ は、置換基を有していてもよいアルキル基又は芳香族炭化水素基を表し、Ａｒ ^２４ およびＡｒ ^２５ は水素原子、置換基を有していてもよいアルキル基又は置換基を有して
いてもよい芳香族環基を表す。尚、Ａｒ ^２１ 〜Ａｒ ^２５ は、互いに隣接するＡｒ ^２１ 〜Ａｒ ^２５ と結合して、環を形成していてもよい。）
That is, a method for manufacturing an organic electroluminescent element having a light emitting layer between a first electrode and a second electrode formed to face the first electrode, wherein the light emitting layer is formed. Using a composition for forming a light-emitting layer containing a light-emitting material, a charge transport material represented by the following formula (2) , and a solvent, the process is a wet film-forming method in an environment where the oxygen concentration is 18 to 22% by volume. A method for producing an organic electroluminescent element, an organic electroluminescent element produced by the production method, and a process for forming the coated film in an inert gas. It exists in the organic EL display apparatus containing an element, and organic EL illumination.

(In the above formula, Ar ²¹ represents an aromatic ring group which may have a substituent, and Ar ²² and Ar ²³ represent an alkyl group or an aromatic hydrocarbon group which may have a substituent. Ar ²⁴ and Ar ²⁵ have a hydrogen atom, an alkyl group which may have a substituent, or a substituent.
An aromatic ring group which may be present. ^{Incidentally,} Ar 21 ^{to Ar 25} is bonded to ^Ar 21 ^{to Ar 25} which are adjacent to each other, may form a ring. )

According to the production method of the present invention, a composition for forming a light emitting layer containing a light emitting material, a charge transport material represented by the above formula (2) and a solvent is used, and the environment has an oxygen concentration of 18 to 22% by volume. By forming a light emitting layer by a wet film forming method, it is possible to manufacture an organic electroluminescent element having high driving stability and a long driving life.
Furthermore, in the present invention, it is not necessary to use a nitrogen atmosphere or a low oxygen environment as the environment for forming the light emitting layer by the wet film formation method, so that it is possible to manufacture an organic electroluminescent element at a low manufacturing cost. .

Accordingly, the organic electroluminescent device manufactured by the manufacturing method of the present invention is a light source that makes use of the characteristics of a flat panel display (for example, for OA computers and thin televisions), an in-vehicle display device, a mobile phone display, and a surface light emitter. (For example, a light source of a copying machine, a backlight light source of a liquid crystal display or an instrument), a display board, and a marker lamp can be considered, and its technical value is great.

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.
<Method for producing organic electroluminescent element>
The method for producing an organic electroluminescent element of the present invention is a method for producing an organic electroluminescent element having a light emitting layer between a first electrode and a second electrode formed to face the first electrode. The light emitting layer is a phosphorescent light emitting material, a charge transport material containing a triarylamine structure and / or a carbazole ring, and a composition for forming a light emitting layer containing a solvent, and the oxygen concentration is 18 to 22 volumes. A method for producing an organic electroluminescent element, comprising a step of forming a coating film by a wet film-forming method in a% environment and a step of heating the coating film in an inert gas.

[Light emitting layer]
The light-emitting layer of the present invention uses a light-emitting layer forming composition containing a light-emitting material, a charge transport material containing a triarylamine structure and / or a carbazole ring, and a solvent, and has an oxygen concentration of 18 to 22% by volume. Then, after forming a coating film by a wet film formation method, the coating film is formed by heating in an inert gas environment.

[Light emitting material]
As the light-emitting material, any known material can be applied, whether it is a fluorescent light-emitting material or a phosphorescent light-emitting material, but a phosphorescent light-emitting material is preferable in the following points.
In principle, phosphorescent materials have very high emission efficiency of organic electroluminescent devices, but the energy gap in the excited singlet state is larger than fluorescent materials with the same emission wavelength, and the exciton lifetime is on the order of microseconds to milliseconds. Since it is long, the driving life is likely to be longer than that of the fluorescent material. Therefore, it is preferable to use a phosphorescent material for applications in which light emission efficiency is more important than lifetime.

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. A Werner complex or an organometallic complex containing a metal as a central 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. Among these, iridium or platinum is more preferable.

  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.

In particular, the phosphorescent organometallic complex of the phosphorescent material is preferably a compound represented by the following formula (III) or formula (IV).
ML _(q−j) L ′ _j (III)
(In formula (III), M represents a metal, q represents the valence of the metal, L and L ′ represent a bidentate ligand, and j represents a number of 0, 1 or 2. )

(In the formula (IV), M ⁷ represents a metal, T represents a carbon atom or a nitrogen atom. R ^{92 to} R ⁹⁵ each independently represents a substituent. However, when T is a nitrogen atom, R 7 ⁹⁴ and R ⁹⁵ are not.)
Hereinafter, the compound represented by the formula (III) will be described first.
In the formula (III), M represents an arbitrary metal, and specific examples of preferable ones include those in the seventh to fifth periodic tables.
The metal mentioned above is mentioned as a metal chosen from 11 groups.

  Moreover, in formula (III), the bidentate ligand L shows the ligand which has the following partial structures.

In the partial structure of L, the ring A1 represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.
Examples of the aromatic hydrocarbon group include a 5- or 6-membered monocyclic ring or a 2-5 condensed ring. Specific examples include monovalent groups derived from benzene, naphthalene, anthracene, phenanthrene, perylene, tetracene, pyrene, benzpyrene, chrysene, triphenylene, acenaphthene, fluoranthene, and fluorene rings. Is mentioned.

Examples of the aromatic heterocyclic group include a 5- or 6-membered monocyclic ring or a 2-4 condensed ring. Specific examples include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, Thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzisothiazole 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, monovalent group derived from an azulene ring, and the like.

In the partial structure of L, ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.
Examples of the nitrogen-containing aromatic heterocyclic group include groups derived from a 5- or 6-membered monocyclic ring or a 2-4 condensed ring. Specific examples include pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, furopyrrole ring, thienofuran ring, benzoisoxazole ring. , Benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone Examples thereof include a monovalent group derived from a ring.

Examples of the substituent that each of ring A1 and ring A2 may have include a halogen atom; an alkyl group; an alkenyl group; an alkoxycarbonyl group; an alkoxy group; an aryloxy group; a dialkylamino group; Acyl group; haloalkyl group; cyano group; aromatic hydrocarbon group and the like.
In the formula (III), the bidentate ligand L ′ represents a ligand having the following partial structure. However, in the following formulae, “Ph” represents a phenyl group.

  Among these, as L ′, the following ligands are preferable from the viewpoint of the stability of the complex.

More preferably, the compound represented by the formula (III) is represented by the following formulas (IIIa), (IIIb),
The compound represented by (IIIc) is mentioned.

(In formula (IIIa), M ⁴ represents the same metal as M, w represents the valence of the metal, and ring A
1 represents an aromatic hydrocarbon group which may have a substituent, and ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent. )

(In formula (IIIb), M ⁵ represents the same metal as M, w represents the valence of the metal, and ring A
1 represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent. )

(In formula (IIIc), M ⁶ represents the same metal as M, w represents the valence of the metal, j represents 0, 1 or 2, and ring A1 and ring A1 ′ each represent Independently represents an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group, and ring A2 and ring A2 ′ are each independently a nitrogen-containing aromatic optionally having a substituent. Represents a heterocyclic group.)
In the above formulas (IIIa), (IIIb) and (IIIc), preferred examples of ring A1 and ring A1 ′ include phenyl group, biphenyl group, naphthyl group, anthryl group, thienyl group, furyl group, benzothienyl group, benzofuryl group. Group, pyridyl group, quinolyl group, isoquinolyl group, carbazolyl group and the like.

In the above formulas (IIIa) to (IIIc), preferred examples of ring A2 and ring A2 ′ include pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, benzimidazole group, quinolyl group, An isoquinolyl group, a quinoxalyl group, a phenanthridyl group, and the like can be given.
Examples of the substituent that the compounds represented by the formulas (IIIa) to (IIIc) may have include a halogen atom; an alkyl group; an alkenyl group; an alkoxycarbonyl group; an alkoxy group; an aryloxy group; A diarylamino group; a carbazolyl group; an acyl group; a haloalkyl group; a cyano group, and the like.

These substituents may be connected to each other to form a ring. As a specific example, a substituent of the ring A1 and a substituent of the ring A2 are bonded, or a substituent of the ring A1 ′ and a substituent of the ring A2 ′ are bonded to each other. A condensed ring may be formed. Examples of such a condensed ring include a 7,8-benzoquinoline group.
Among these, as a substituent for ring A1, ring A1 ′, ring A2 and ring A2 ′, an alkyl group, alkoxy group, aromatic hydrocarbon group, cyano group, halogen atom, haloalkyl group, diarylamino group, carbazolyl are more preferable. Groups.

In addition, preferable examples of M ^{4 to} M ⁶ in the formulas (IIIa) to (IIIc) include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, or gold.
Specific examples of the organometallic complexes represented by the above formulas (III) and (IIIa) to (IIIc) are shown below, but are not limited to the following compounds.

Among the organometallic complexes represented by the above formula (III), in particular, the ligand L and / or L ′
As the compound, a 2-arylpyridine ligand, that is, a compound having 2-arylpyridine, an arbitrary substituent bonded thereto, and a compound obtained by condensing an arbitrary group thereto is preferable.
The compounds described in International Publication No. 2005/019373 pamphlet can also be used as the light emitting material.

Next, the compound represented by formula (IV) will be described.
In formula (IV), M ⁷ represents a metal. Specific examples include the metals described above as the metal selected from Groups 7 to 11 of the periodic table. Among these, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold is preferable, and divalent metals such as platinum and palladium are particularly preferable.

In the formula (IV), R ⁹² and R ⁹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, Represents an alkoxy group, an alkylamino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group;

Further, when T is carbon ^{atom, R 94} and ^{R 95} each independently ^represents a substituent represented by the same exemplary compounds and ^{R 92} and ^{R 93.} Also, if T is a nitrogen ^{atom, R 94} and ^{R 95} is not.
R ^{92 to} R ⁹⁵ may further have a substituent. When it has a substituent, there is no restriction | limiting in particular in the kind, Arbitrary groups can be made into a substituent.

Further, any two or more groups of R ^{92 to} R ⁹⁵ may be connected to each other to form a ring.
Specific examples (T-1, T-10 to T-15) of the organometallic complex represented by the formula (IV) are shown below, but are not limited to the following examples. In the chemical formulas below, “Me” represents a methyl group, and Et represents an ethyl group.

  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 organic compound, 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.

The ratio of the light emitting material in the light emitting layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.05% by weight or more and usually 35% by weight or less. If the amount of the light emitting material is too small, uneven light emission may occur. If the amount is too large, the light emission efficiency may be reduced. In addition, when using together 2 or more types of luminescent material, it is made for the total content of these to be contained in the said range.

[Charge transport material]
The charge transport material in the present invention is a compound containing a triarylamine structure and / or a carbazole ring.
The compound containing a triarylamine structure and / or a carbazole ring is further preferably a compound represented by the following formula (2) or (3) from the viewpoint that the effects of the present invention can be further obtained.

(In the above formula, Ar ²¹ and Ar ²⁶ represent an aromatic ring group which may have a substituent, and Ar ^{22 to} Ar ²⁵ and Ar ^{27 to} Ar ³¹ may have a substituent. It represents an aromatic ring group which may have a good alkyl group or substituent.
^{Incidentally,} Ar 21 ^{to Ar 31} is bonded to ^Ar 21 ^{to Ar 31} which are adjacent to each other, may form a ring. )
[Regarding Compound Represented by Formula (2)]
Ar ²¹ represents an aromatic ring group that may have a substituent, and Ar ^{22 to} Ar ²⁵ represent an alkyl group that may have a substituent, or an aromatic that may have a substituent. Represents a cyclic group.

  The alkyl group preferably has 1 to 20 carbon atoms. For example, methyl group, ethyl group, propyl group, iso-propyl group, butyl group, iso-butyl group, sec-butyl group, tert-butyl group, hexyl group, octyl group. Group, cyclohexyl group, decyl group, octadecyl group and the like. A methyl group, an ethyl group, an iso-propyl group, a sec-butyl group, and a tert-butyl group are preferable. Methyl group and ethyl group are preferable from the viewpoint of availability of raw materials and low cost, and iso-butyl group, sec-butyl group, and tert-butyl group are preferable because they have high solubility in nonpolar solvents.

As an aromatic hydrocarbon group, C6-C25 is preferable and the aromatic hydrocarbon group derived from a 6-membered monocyclic ring or a 2-5 condensed ring is preferable. Examples thereof include groups derived from a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, and the like.
Examples of the aromatic ring group include an aromatic hydrocarbon group and an aromatic heterocyclic group.

The aromatic heterocyclic group preferably has 3 to 20 carbon atoms, and furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrrolo Imidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, Examples include groups derived from pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring and the like.

The substituent that the alkyl group and the aromatic heterocyclic group may have is arbitrary as long as the effects of the present invention are not impaired. For example, the aromatic group having 3 to 10 carbon atoms has 1 to 5 aromatic rings. Examples include linked groups.
(About the compound represented by Formula (3))
Ar ²⁶ in Formula (3) includes the same ring-derived group as Ar ²¹ in Formula (2), and Ar ^{27 to} Ar ³¹ have the same meanings as Ar ^{22 to} Ar ²⁵ in Formula (2). The same applies to specific examples and preferred examples.

[Concrete example]
Although the preferable specific example of the charge transport material in this invention is shown below, this invention is not limited to these.

In the present invention, the molecular weight of the compound used as the charge transport material is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, and still more preferably 3000 or less. Also, it is usually 100 or more, preferably 200 or more, more preferably 300 or more, and still more preferably 400 or more.
Within the above range, the heat resistance is good, it is difficult to cause gas generation, and the film quality when the film is formed is preferable. Furthermore, it is easy to increase the purity because it is easy to purify.

[solvent]
The composition for forming a light emitting layer in the present invention contains a solvent. Here, the solvent in the present invention is a compound that is liquid in an atmosphere of 20 ° C. and 1 atm, and that can dissolve the light emitting material and the charge transporting material contained in the composition for forming a light emitting layer in the present invention. is there.
The solvent is not particularly limited as long as it is a commercially available polar or nonpolar solvent. Among them, a substituted or unsubstituted aromatic such as benzene, toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, and dichlorobenzene. Aromatic hydrocarbon solvents, aromatic ether solvents such as anisole, benzoic acid ester, diphenyl ether, aromatic ester solvents, linear or cyclic alkane solvents such as hexane, heptane, cyclohexane, and carboxylic acid ester solvents such as ethyl acetate Solvents, carbonyl-containing solvents such as acetone and cyclohexanone, water, alcohols, cyclic ethers and the like are preferable, and aromatic hydrocarbon solvents are more preferable. Among them, benzene, toluene, mesitylene and cyclohexylbenzene are preferable.

In the composition for forming a light emitting layer in the present invention, one kind of solvent may be contained, or may be contained in a combination of two or more kinds of solvents, but usually one or more kinds, preferably It is preferably contained in a combination of 2 or more, usually 10 or less, preferably 8 or less, more preferably 6 or less.
[Other ingredients]
In addition, the composition for forming a light emitting layer in the present invention includes a leveling agent, an antifoaming agent, a coating property improving agent such as a thickener, a charge transporting aid such as an electron accepting compound and an electron donating compound, a binder resin, and the like. You may contain. The content of these other components in the composition for forming the light emitting layer is usually from the viewpoint of not significantly inhibiting the charge transfer of the thin film, not inhibiting the light emission of the light emitting material, and not deteriorating the film quality of the thin film. 50% by weight or less.

[Solvent concentration / solid concentration]
When the composition for forming a light emitting layer in the present invention is used as a composition for forming a light emitting layer for forming a light emitting layer of an organic electroluminescence device of the present invention described later, the content of the solvent in the composition for forming a light emitting layer Is optional as long as the effect of the present invention is not significantly impaired, but is usually 50% by weight or more and usually 99.9999% by weight or less. In addition, when mixing and using 2 or more types of solvents as a solvent, it is made for the sum total of these solvents to satisfy | fill this range.

Further, the total solid content concentration of the light emitting material, the charge transporting material, etc. is usually 0.01% by weight or more and usually 70% by weight or less. If this concentration is too large, film thickness unevenness may occur, and if it is too small, defects may occur in the film.
[Film formation method]
When forming an organic thin film by the wet film-forming method according to the present invention, a composition for forming a light-emitting layer containing the light-emitting material, the charge transporting material, and a solvent is prepared and used to form a film.

The ratio of the solvent to the composition for forming a light emitting layer for forming an organic thin film is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 30% by weight or more and usually 99.99% by weight or less. In addition, when mixing and using 2 or more types of solvents as a solvent, it is made for the sum total of these solvents to satisfy | fill this range.
The solid content concentration of the charge transport material, the light emitting material, etc. in the composition for forming the light emitting layer is usually 0.01% by weight or more and usually 70% by weight or less. If this concentration is too large, film thickness unevenness may occur, and if it is too small, defects may occur in the film.

After wet-deposition of the composition for forming a light emitting layer, the obtained coating film is dried and the solvent is removed to form an organic thin film.
Examples of the wet film forming method in the present invention include spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, nozzle printing, inkjet printing, and screen printing. A method of forming a film using an ink containing a solvent, such as a printing method, a gravure printing method, a flexographic printing method, or an offset printing. From the viewpoint of ease of patterning, a die coating method, a roll coating method, a spray coating method, an ink jet method, or a flexographic printing method is preferable.

The oxygen concentration in the environment in which a coating film is formed by a wet film formation method (hereinafter sometimes referred to as “coating step”) is usually 18% by volume or more, more preferably 19% by volume or more, and usually 22% by volume or less. More preferably, it is 21 volume% or less.
Within the above range, oxygen is appropriately taken into the light emitting layer, and is preferable in that the effect of the present invention is obtained. When the lower layer of the light emitting layer is an organic layer, it is excessively contained in the organic layer. This is preferable in that oxygen is hardly taken in.

Although the relative humidity in an application | coating process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally, and usually 80% or less.
The cleanliness of the coating process is FED standard, and is usually class 100,000 or less, preferably class 10,000 or less, more preferably class 1000 or less, and usually class 100 or more, preferably class 10 or more.

Within the above range, since a coating film with few defects can be formed, an element with high driving durability can be manufactured, and this is preferable in terms of improving yield.
In addition, although the measurement of the said cleanliness can be measured, for example using particle counter KR-12A (made by Rion Co., Ltd.), if the same measurement is possible, it will not be limited to these.

The pressure in the coating step is usually 110000 Pa or less, preferably 105000 Pa or less, and usually 90000 Pa or more, preferably 950,000 Pa or more.
The above-mentioned range is a general atmospheric pressure, and it is preferable in that a large area can be easily applied because it does not require equipment or time for a vacuum environment.
The temperature in the coating step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower in order to prevent film loss due to the formation of crystals in the composition.

After the coating film is formed by the wet film forming method, a heating step (hereinafter may be referred to as “heating step”) is performed.
As the environment for the heating process, an inert gas is usually used.
Examples of the inert gas include noble gases such as nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and xenon gas, and nonflammable gases such as chlorofluorocarbon gas, and nitrogen gas is preferable.

These inert gases can be used alone or in combination of two or more in any ratio and combination.
Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  As for the heating temperature in the heating step, it is preferable to heat at a temperature not higher than the glass transition temperature of the charge transport material or phosphorescent material used in the composition for forming a light emitting layer, unless the effects of the present invention are significantly impaired. Further, when two or more kinds of charge transport materials or light emitting materials used in the composition for forming a light emitting layer are contained, at least one kind is heated at a temperature lower than the glass transition temperature of the charge transport material or light emitting material. Is preferred.

In the heating step, the heating time is not limited, but is preferably 10 seconds or longer and usually 180 minutes or shorter. If the heating time is too long, the light emission efficiency tends to decrease, and if it is too short, the light emitting layer tends to be inhomogeneous. Heating may be performed in two steps.
The thickness of the organic thin film is arbitrary as long as the effects of the present invention are not significantly impaired. However, when the organic thin film is a light emitting layer, it is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. Range. If the thickness of the organic thin film is too thin, defects may occur in the film, and if it is too thick, the light emitting layer may be used and the drive voltage may increase.

[Reason why the present invention is effective]
The reason why the present invention is effective is estimated as follows.
A film formed by a wet film formation method has a lower film density than a film formed by a vacuum evaporation method. That is, the film formed by the wet film formation method has more gaps than the film formed by the vapor deposition method, and this becomes a site for trapping charges.

Further, when a film is formed by a wet film formation method, oxygen is more easily taken into the film than by a vacuum evaporation method.
In other words, in the case of the wet film forming method, the movement of electric charges is likely to be hindered by further adsorption of oxygen to the sites where electric charges are trapped. More specifically, it is presumed that the movement of electrons is particularly trapped by the adsorption of oxygen.

On the other hand, in the present invention , when the compound containing the triarylamine structure and the carbazole ring in the molecule is used as a material for forming the light emitting layer, the light emitting site of the light emitting layer is considered to be on the anode side. In the case of using the anode side, deterioration near the interface due to driving is promoted, so that high driving stability may not be obtained.
However, when a film is formed by a wet film forming method in an environment where the oxygen concentration is 18 to 22% by volume, oxygen is taken into the film and the light emitting site is shifted to the cathode side.

In addition, after forming the coating film, it is formed by heating the coating film, but by performing heating in an inert gas, it is difficult to place a chemical reaction such as oxidation or decomposition of heat unstable oxygen, It will be in a state of being incorporated as a molecule in the organic layer.
From this, it is estimated that the organic electroluminescent element formed with the manufacturing method of this invention has a long drive life.

<Organic electroluminescent device>
Below, the layer structure of the organic electroluminescent element 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 plays a role of hole injection into the layer on the light emitting layer side.
This anode is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as indium and / or tin oxide, metal halide such as copper iodide, carbon black, or poly It is composed of conductive polymers such as (3-methylthiophene), polypyrrole and polyaniline.

The anode is usually formed by a sputtering method, a vacuum deposition method, or the like. In addition, when forming an anode using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution is used. The anode can also be formed by dispersing and coating the substrate. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on a substrate by electrolytic polymerization, or an anode can be formed by applying a conductive polymer on a substrate (Appl. Phys. Lett., 60). roll,
2711, 1992).

The anode usually has a single-layer structure, but it can also have a laminated structure composed of a plurality of materials if desired.
The thickness of the anode 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 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 opaqueness is acceptable, the thickness of the anode is arbitrary, and the anode may be the same as the substrate. Furthermore, it is also possible to laminate different conductive materials on the anode.

The surface of the anode is treated with ultraviolet (UV) / ozone, oxygen plasma, or argon plasma for the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve hole injection. Is preferred.
(Hole injection layer)
The hole injection layer is a layer that transports holes from the anode to the light emitting layer, and is usually formed on the anode.

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 a constituent material of the hole injection layer.
The hole transporting compound is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device, and may be a polymer compound or the like, a monomer 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 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. In the case of containing two or more kinds of hole transporting compounds, the combination is arbitrary, but one or more kinds of aromatic tertiary amine polymer compounds and one or two kinds of other hole transporting compounds. It is preferable to use the above in combination.

Among the above 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 the 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, the .Z ^b representing each independently, may have a which may have aromatic hydrocarbon group or a substituent substituted aromatic heterocyclic group, the following In addition, two groups bonded to the same N atom among Ar ^{1 to} Ar ⁵ may be bonded to each other to form a ring.

(In the above formulas, Ar ^{6 to} Ar ¹⁶ each independently represents an aromatic hydrocarbon group which may have a substituent or an 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 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 alkyl groups, alkenyl groups, alkoxy groups, silyl groups, siloxy groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like. .

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), 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 hole transporting compound may be a crosslinkable polymer described in the following [Hole transporting layer]. The same applies to the film formation method when the crosslinkable polymer is used.
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 composition for forming a hole injection layer preferably contains an electron accepting compound as a constituent material of the hole injection layer.
The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound which is the compound of these is further more preferable.

Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and triphenylsulfonium tetrafluoroborate (International Publication No. WO 2005/089024); High valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067), ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds such as); fullerene derivatives; iodine; sulfonate ions such as polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate ions, and the like.

These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound.
The content of the electron-accepting compound in the hole-injecting layer or the composition for forming a hole-injecting layer 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.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and 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, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and ratios.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying step, which may adversely affect other layers and the substrate.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.
Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.

Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.
Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.
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.
These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.
(Film formation method)
After preparing the composition for forming the hole injection layer, the composition is applied to the layer corresponding to the lower layer of the hole injection layer (usually an anode) by wet film formation, and dried to dry the hole. An injection layer is formed.

The temperature in the coating step is preferably 10 ° C. or higher and preferably 50 ° C. or lower in order to prevent film loss due to the formation of crystals in the composition.
Although the relative humidity in an application | coating process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally, and usually 80% or less.
After coating, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When forming the hole injection layer by vacuum deposition, one or more of the constituent materials of the hole injection layer (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles (in case of using two or more kinds of materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then heat the crucible (two or more kinds) When using materials, heat each crucible) and evaporate by controlling the amount of evaporation (when using two or more materials, evaporate by independently controlling the amount of evaporation) and place it facing the crucible. A hole injection layer is formed on the anode of the substrate. In addition, when using 2 or more types of materials, those hole mixture layers can also be formed by putting them in a crucible and heating and evaporating them.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired.
It is not less than × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) and usually not more than 9.0 × 10 ⁻⁶ Torr (12.0 × 10 ⁻⁴ Pa). The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

[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 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. For example, as a hole transport compound used in the above-described hole injection layer 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, metal complexes and the like.

  In addition, 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 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, for example, a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and acenaphthene. Examples 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 these rings are linked 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. ring Are those groups group and the rings of from 2-4 fused ring is linked by a direct bond or two or more rings.

Ar ^a and Ar ^b are each independently from benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, fluorene ring, from the viewpoint of solubility in organic solvents and heat resistance. A group derived from a group selected from the group consisting of two or more benzene rings linked together (for example, a biphenyl group (biphenyl group) or a terphenylene group (terphenylene group)) is preferred.

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 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 ^a 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). Independently 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 are —O—, —BR—, —NR—, —SiR ₂ —, —PR—, —SR—, —CR ₂ —, or a group formed by bonding thereof. R represents a hydrogen atom or an arbitrary organic group. The organic group in the present invention is a group containing at least one carbon atom.

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

(In 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, and v and w each represent 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) can be used as 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 promote 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 in an amount of not more than wt%, more preferably not more than 10 wt%.

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 active 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 active 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, 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 active energy irradiation other than light, for example, there is a method of irradiation using a so-called microwave oven that irradiates a microwave generated by a magnetron. 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.

The irradiation of active energy such as heating and light may be performed alone 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]
When a hole injection layer is provided on the hole injection layer or a hole transport layer, a light emitting layer is provided on the hole transport layer.

The light emitting layer in the present invention is formed using the materials and methods described in the above [Light emitting layer] section.
The thickness of the light emitting layer 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 light emitting layer is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.
[Hole blocking layer]
A hole blocking layer may be provided between the light emitting layer and an electron injection layer described later. The hole blocking layer is a layer stacked on the light emitting layer so as to be in contact with the cathode side interface of the light emitting layer.

The hole blocking layer has a role of blocking holes moving from the anode from reaching the cathode and a role of efficiently transporting electrons injected from the cathode toward the light emitting layer.
The physical properties required for the material constituting the hole blocking layer include high electron mobility, low hole mobility, large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). It is expensive. 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 metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Triazole derivatives such as styryl compounds (JP-A-11-242996), 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. Furthermore, compounds having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005-022962 are also preferable as the material for the hole blocking layer.

In addition, the material of a hole-blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
There is no restriction | limiting in the formation method of a hole-blocking layer. 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 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.

[Electron transport layer]
You may provide an electron carrying layer between a light emitting layer and the below-mentioned electron injection layer.
The electron transport layer is provided for the purpose of further improving the light emission efficiency of the device, and can efficiently transport electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the light emitting layer. Is formed.

  The electron transporting compound used for the electron transporting layer is usually a compound that has high electron injection efficiency from the cathode or the electron injection layer and has high electron mobility and can efficiently transport the injected electrons. Is used. Examples of the compound satisfying such conditions 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), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type zinc Such as emissions of zinc, and the like.

In addition, only 1 type may be used for the material of an electron carrying layer, and 2 or more types may be used together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of an electron carrying layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
The thickness of the electron transport layer 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]
The electron injection layer plays a role of efficiently injecting electrons injected from the cathode into the light emitting layer. In order to perform electron injection efficiently, the material for forming the electron injection layer is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, alkaline earth metals such as barium and calcium, and the film thickness is preferably from 0.1 nm to 5 nm.

  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, only 1 type may be used for the material of an electron injection layer, and 2 or more types may be used together by arbitrary combinations and a ratio.
There is no restriction | limiting in the formation method of an electron injection layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.
[cathode]
The cathode plays a role of injecting electrons into a layer (such as an electron injection layer or a light emitting layer) on the light emitting layer side.

  As the material of the cathode, it is possible to use the material used for the anode described above, but in order to perform electron injection efficiently, a metal having a low work function is preferable, for example, tin, magnesium, indium, calcium, A suitable metal such as aluminum or 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, only 1 type may be used for the material of a cathode, and 2 or more types may be used together by arbitrary combinations and a ratio.
The thickness of the cathode is usually the same as that of the anode.
Further, for the purpose of protecting the cathode made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

[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 and the cathode in addition to the layers described above, and an arbitrary layer may be omitted.
[Electron blocking layer]
Examples of the layer that may be included include an electron blocking layer.

  The electron blocking layer is provided between the hole injecting layer or the hole transporting layer and the light emitting layer, and prevents electrons moving from the light emitting layer from reaching the hole injecting layer. Increases the recombination probability of holes and electrons, and has the role of confining the generated excitons in the light-emitting layer and the role of efficiently transporting holes injected from the hole injection layer toward the light-emitting layer. . 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 electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the light emitting layer is formed as an organic layer according to the present invention by a wet film formation method, the electron blocking layer is also required to be compatible with 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 only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
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 and the light emitting layer or the electron transport layer, for example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ), etc. are formed. It is also an effective method to improve the efficiency of the device by inserting a very thin insulating film (0.1 to 5 nm) (Applied Physics Letters, 1997, Vol. 70, pp. 152; No. 74586; IEEE
Transactions on Electron Devices, 1 997
Year, 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 a board | substrate in reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate are in the order of cathode, electron injection layer, electron transport layer, hole blocking layer, light emitting layer, hole transport layer, hole injection layer, and anode. It may be provided.
Furthermore, it is also possible to constitute the organic electroluminescent element according to the present invention by laminating components other than the substrate between two substrates, at least one of which is transparent.

In addition, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interface layer between the steps (between the light emitting units) (when 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, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

Furthermore, the organic electroluminescent device according to the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array. You may apply to the structure by which the cathode is arrange | positioned at XY matrix form.
Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

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

<Organic EL lighting>
The organic EL illumination of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic EL illumination of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.

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.
Example 1
An organic electroluminescent element having the structure shown in FIG. 1 was produced by the following method.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 having a thickness of 150 nm (sputtered film; sheet resistance 15 Ω) is patterned into a 2 mm wide stripe using normal photolithography and hydrochloric acid etching. Thus, an anode 2 was formed. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, then dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  Next, the hole injection layer 3 was formed by a wet film forming method as follows. As a material for the hole injection layer 3, a non-conjugated polymer compound (PB-1 (weight average molecular weight: 52000, number average molecular weight: 32500)) having an aromatic amino group represented by the structural formula shown below and the structure shown below: Using the electron-accepting compound (A-2) of the formula, spin coating was performed under the following conditions.

<Composition for hole injection layer>
Solvent ethyl benzoate
Coating solution concentration PB-1 2.0% by weight
A-2 0.4% by weight
<Film formation conditions>
Spinner speed 2250rpm
Spinner rotation time 30 seconds
Spin coating atmosphere Baking conditions in an environment with an oxygen concentration of 20% by volume 230 ° C x 60 minutes (in air)
A uniform thin film having a thickness of 30 nm was formed by the above spin coating.
Subsequently, a hole transport layer was formed by a wet film forming method as follows. A composition for organic electroluminescence device was prepared using a charge transport material (PB-2) having the following structural formula as a material for the hole transport layer and cyclohexylbenzene as a solvent. Was used for spin coating under the following conditions.

<Composition for hole transport layer>
Solvent Cyclohexylbenzene
Coating solution concentration PB-2 1.4% by weight
<Film formation conditions>
Spinner speed 1500rpm
Spinner rotation time 120 seconds
Spin coating atmosphere Baking conditions in an environment with an oxygen concentration of 20% by volume 230 ° C x 60 minutes (under dry nitrogen)
A uniform thin film having a thickness of 20 nm was formed by the above spin coating.

  Next, in forming the light emitting layer, the organic compound (HO-1) and organic compound (HO-2) shown below as the charge transport material in the present invention, and the organic compound shown below as the light emitting material A composition for forming a light emitting layer shown below is prepared using (DO-1) and an organic compound (DO-2), and spin coated on the hole transport layer under the conditions shown below to form a light emitting layer with a film thickness of 50 nm. Got.

<Composition for light emitting layer>
Solvent Cyclohexylbenzene
Concentration in composition HO-1 2.5% by weight
HO-2 2.5% by weight
DO-1 0.25% by weight
DO-2 0.35 wt%
<Film formation conditions>
Spinner speed 2000rpm
Spinner rotation time 120 seconds
Spin coating atmosphere In an environment with an oxygen concentration of 20% by volume, 25 ° C., 1.01 ×
10 ⁵ Pa,
FED standard class 100
Bake conditions 130 ° C x 60 minutes (under dry nitrogen)
Next, a pyridine derivative (HB-1) shown below as a hole blocking layer was deposited at a crucible temperature of 251 to 252 ° C. at a deposition rate of 0.08 to 0.12 nm / sec. The degree of vacuum during the deposition was 2.1 to 2.4 × 10 ⁻⁴ Pa (about 1.6 to 1.8 × 10 ⁻⁶ Torr).

Next, an aluminum 8-hydroxyquinoline complex (ET-1) shown below was deposited as an electron transport layer on the hole blocking layer in the same manner. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex is controlled in the range of 222 to 239 ° C., and the degree of vacuum during the deposition is 1.7 to 2.0 × 10 ⁻⁴ Pa (about 1.3 to 1. 5 × 10 ⁻⁶ Torr), the deposition rate was 0.1 nm / second, and the film thickness was 30 nm.

The substrate temperature during vacuum deposition of the hole blocking layer and the electron transport layer was kept at room temperature.
Here, the element on which the electron transport layer has been deposited is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide stripe shadow mask is orthogonal to the ITO stripe of the anode 2 as a mask for cathode deposition. In close contact with the element, it is placed in another vacuum deposition apparatus and the degree of vacuum in the apparatus is 2.3 × 10 ⁻⁶ Torr (about 3.0 × 10 ⁻⁴ Pa) in the same manner as the organic layer. Exhaust until below.

Next, lithium fluoride (LiF) is deposited on the electron transport layer as an electron injection layer by using a molybdenum boat, a deposition rate of 0.015 nm / second, and a degree of vacuum of 2.5 × 10 ⁻⁶ Torr (about 3 3 × 10 ⁻⁴ Pa) and a film thickness of 0.5 nm was formed on the electron transport layer.
Next, on the electron injection layer, aluminum is heated as a cathode by a molybdenum boat, a deposition rate of 0.5 to 3.0 nm / second, and a degree of vacuum of 3.3 to 7.5 × 10 ⁻⁶ Torr (about The film was formed at 4.4 to 10.0 × 10 ⁻⁴ Pa) to form an aluminum layer having a thickness of 80 nm, thereby completing the cathode.

The substrate temperature at the time of vapor deposition of the electron injection layer and the cathode was kept at room temperature.
As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained.
The maximum wavelength of the emission spectrum of the device was 628 nm, which was identified as that from the iridium complex (DO-2). The chromaticity was CIE (x, y) = (0.680, 0.317).

(Example 2)
An organic electroluminescent element was produced in the same manner as in Example 1 except that the charge transport material (HO-2) was changed to the organic compound (HO-3) represented by the following structural formula in Example 1.
A uniform thin film (light emitting layer) having a thickness of 50 nm was formed by spin coating.

( Comparative Example 5 )
An organic electroluminescent element was produced in the same manner as in Example 1 except that the charge transport material (HO-2) was changed to the organic compound (HO-4) represented by the following structural formula in Example 1.
A uniform thin film (light emitting layer) having a thickness of 50 nm was formed by spin coating.

( Comparative Example 6 )
An organic electroluminescent element was produced in the same manner as in Example 1 except that the charge transport material (HO-2) was changed to the organic compound (HO-5) represented by the following structural formula in Example 1.
A uniform thin film (light emitting layer) having a thickness of 50 nm was formed by spin coating.

(Comparative Example 1)
In Example 1, the spin coating atmosphere of the hole transport layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen, and the spin coating atmosphere of the light emitting layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen. Otherwise, an organic electroluminescent element was produced in the same manner as in Example 1.
(Comparative Example 2)
In Example 2, the spin coating atmosphere of the hole transport layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen, and the spin coating atmosphere of the light emitting layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen. Otherwise, an organic electroluminescent element was produced in the same manner as in Example 2.

(Comparative Example 3)
In Example 3, the spin coating atmosphere of the hole transport layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen, and the spin coating atmosphere of the light emitting layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen. Otherwise, an organic electroluminescent element was produced in the same manner as in Example 3.
(Comparative Example 4)
In Example 4, the spin coating atmosphere of the hole transport layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen, and the spin coating atmosphere of the light emitting layer was changed from an environment having an oxygen concentration of 20% by volume to nitrogen. Otherwise, an organic electroluminescent element was produced in the same manner as in Example 4.

The characteristics of the organic electroluminescent devices prepared in Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1, and a direct current driving test was performed with an initial luminance of 3000 cd / m ² until the luminance decreased to 1500 cd / m ² . The time (luminance 50% decay life) is summarized in Table 2.

  As shown in Table 2, it can be seen that the device manufactured by the method for manufacturing an organic electroluminescent device of the present invention has a long driving life.

  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 (4)

A method for producing an organic electroluminescent element having a light emitting layer between a first electrode and a second electrode formed opposite to the first electrode,
Forming the light emitting layer comprises:
Using a light emitting layer forming composition containing a light emitting material, a charge transport material represented by the following formula (2), and a solvent,
Manufacturing of an organic electroluminescent device, comprising: a step of forming a coating film by a wet film formation method in an environment where the oxygen concentration is 18 to 22% by volume; and a step of heating the coating film in an inert gas Method.

(In the above formula, Ar ²¹ represents an optionally substituted aromatic hydrocarbon group having 6 to 25 carbon atoms or an aromatic heterocyclic group having 3 to 20 carbon atoms , Ar ²² and Ar ^23. Represents an alkyl group which may have a substituent or an aromatic hydrocarbon group having 6 to 25 carbon atoms , and Ar ²⁴ and Ar ²⁵ are a hydrogen atom, an alkyl group which may have a substituent or It represents an optionally substituted aromatic hydrocarbon group having 6 to 25 carbon atoms or an aromatic heterocyclic group having 3 to 20 carbon atoms , wherein Ar ^{21 to} Ar ²⁵ are adjacent to each other Ar ^21. To Ar ²⁵ may form a ring.)   An organic electroluminescent element formed by the manufacturing method according to claim 1.   An organic EL display comprising the organic electroluminescent element according to claim 2.   An organic EL illumination comprising the organic electroluminescent element according to claim 2.

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