JP2011026237A - Organic compound, charge-transporting material, composition for organoelectroluminescent element, organoelectroluminescent element, organic el display and organic el illumination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic compound exhibiting excellent heat resistance and high charge-transporting performance and having high solubility in an organic solvent. <P>SOLUTION: The organic compound includes a partial structure represented by formula (I) and a partial structure represented by formula (II) in one molecule and has at least two optionally substituted naphthalene rings. In formulae (I) and (II), the rings A to F are each independently an optionally substituted benzene ring; provided that substituent groups of the rings A to F are bonded together to form a naphthalene ring together with these rings or a naphthalene ring is linked directly or via an another group to the rings A to F so that the compound has at least two naphthalene rings in one molecule. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is a compound useful as a charge transport material suitably used for an organic electroluminescence device having high luminous efficiency, low driving voltage, and excellent driving stability including heat resistance, and further suitable for use in a wet film-forming method. The present invention relates to an organic compound having high solubility in an organic solvent.

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 formation method. Among these, the wet film forming method does not require a vacuum process, and can easily increase the 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 formation method. There's a problem.

・ It is difficult to control the degree of polymerization and molecular weight distribution of polymer materials.
・ Deterioration due to terminal residues occurs during continuous driving.
・ High purity of the material itself is difficult and contains impurities.
Due to the above-described problems, an element using a wet film formation method is inferior in driving stability as compared with an element using a 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 transporting materials and light-emitting materials) instead of a polymer compound. The organic electroluminescent elements described above are described, and the following compounds H-1 and H-2 are used as the hole transporting charge transporting material.

  In addition, in an organic electroluminescent device using an organic thin film made of a plurality of low-molecular materials formed by a wet film forming method, Non-Patent Document 1 discloses a device using phosphorescence emission in order to increase the luminous efficiency of the device. The following compounds H-3 and H-4 are used for the charge transport materials described.

  However, the compounds H-1, H-2, H-3, and H-4 have low solubility in solvents. For this reason, it is necessary to use a halogen-based solvent such as chloroform as the coating solvent. However, the halogen-based solvent has a large environmental load and has a practical problem. Furthermore, since there is a high possibility that the material is deteriorated by impurities contained in the halogen-based solvent, it is considered that the element by the wet film forming method using the halogen-based solvent does not have sufficient driving stability.

Moreover, the said compound H-1, H-2, H-3, H-4 has a low glass transition temperature, and it is thought that the element currently disclosed by patent document 1 and nonpatent literature 1 is not enough in heat resistance. Furthermore, the compounds H-1, H-2, H-3, and H-4 are very easy to crystallize, and it is difficult to obtain a uniform amorphous film by the wet film forming method.
In the case where a phosphorescent material is used as the light-emitting material, compound H-1 has a low triplet excitation level, and thus light emission of an organic electroluminescent element formed using a composition containing compound H-1 and the phosphorescent material. Efficiency is considered low.

  Patent Document 2 discloses, for example, a charge transport material including a carbazole ring represented by the following formula H-5 and a triphenylamine structure. However, problems have been pointed out for practical use in terms of durability and driving voltage, and further improvement in performance has been demanded.

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

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

INDUSTRIAL APPLICABILITY The present invention is a compound useful as a charge transport material suitably used for an organic electroluminescence device having high luminous efficiency, low driving voltage, and excellent driving stability including heat resistance, and further suitable for use in a wet film-forming method. It is an object of the present invention to provide an organic compound that is highly soluble in an organic solvent.
It is another object of the present invention to provide an organic electroluminescent element having high current efficiency and a long driving life, and an organic EL display and organic EL illumination including the element.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by further including two or more naphthalene rings in a compound having a specific partial structure. did.
That is, the present invention is a compound having a partial structure represented by the following formula (I) and a partial structure represented by the following formula (II) in one molecule, wherein the compound has a substituent. An organic compound, a charge transport material, a composition for an organic electroluminescent device containing the compound, an organic electroluminescent device, an organic EL display and an organic EL illumination, characterized by having at least two naphthalene rings Exist.

(In formulas (I) and (II), ring A to ring F each independently represent a benzene ring optionally having a substituent.
However, the substituents of the rings A to F are bonded to each other to form a naphthalene ring together with these rings, or the naphthalene ring is bonded to the rings A to F directly or through other groups, The compound has two or more naphthalene rings in one molecule. )

  The organic compound having the partial structure represented by the above formula (I) and the partial structure represented by the above formula (II) of the present invention has a high triplet excitation level and high heat resistance. Furthermore, by having two or more naphthalene rings, steric hindrance occurs between the naphthalene ring and other rings, thereby improving the solubility in organic solvents and the film quality. For this reason, by using the composition for organic electroluminescent elements of the present invention, it is possible to form a film that is hardly crystallized, has excellent thermal stability, and has excellent light emitting characteristics by a wet film forming method.

Therefore, the organic electroluminescent element having such a layer containing the organic compound of the present invention is an organic electroluminescent element having high luminous efficiency, low driving voltage, and high driving stability including heat resistance.
The organic electroluminescent device according to the present invention is a flat panel display (for example, for OA computers or wall-mounted televisions), an in-vehicle display device, a light source utilizing characteristics as a mobile phone display or a surface light emitter (for example, a light source of a copying machine, a liquid crystal It can be applied to backlight sources for displays and instruments, display panels, and indicator lights, 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.

Hereinafter, embodiments of the organic compound, charge transport material, composition for organic electroluminescence device, organic electroluminescence device, and organic EL display and organic EL lighting of the present invention will be described in detail. Is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist.
<Organic compounds>
The organic compound of the present invention has a partial structure represented by the following formula (I) in one molecule (hereinafter sometimes referred to as “partial structure (I)”) and a partial structure represented by the following formula (II). (Hereinafter sometimes referred to as “partial structure (II)”), which is an organic compound having two or more naphthalene rings which may have a substituent in the compound.

(In formulas (I) and (II), ring A to ring F each independently represent a benzene ring which may have a substituent, provided that the substituents of ring A to ring F are bonded to each other. Then, these compounds have two or more naphthalene rings in one molecule by forming a naphthalene ring together with these rings, or by bonding a naphthalene ring to rings A to F directly or via other groups. .)
[1] Structural features
The organic compound of the present invention has one or more partial structures (I) and one or more partial structures (II) as partial structures, and further has two or more naphthalene skeletons which may have a substituent. .

By having one or more partial structures (I) in one molecule, higher heat resistance, and by having one or more partial structures (II) in one molecule, more excellent charge (hole) transport ability Have Furthermore, it has two or more naphthalene rings which may have a substituent in order to have high solubility in an organic solvent.
In the organic compound of the present invention, the ratio of the number of each partial structure in one molecule is partial structure (I): partial structure (II) = 1: 3 to 3: 1 from the viewpoint of charge transport ability and heat resistance. Preferably there is.

[2] Molecular weight range
The molecular weight of the organic compound of the present invention is usually 5000 or less, preferably 4000 or less, more preferably 3000 or less, and usually 400 or more, preferably 500 or more, more preferably 600 or more.
If the molecular weight exceeds this upper limit, purification may be difficult due to the high molecular weight of impurities, and if the molecular weight falls below this lower limit, the glass transition temperature, melting point, vaporization temperature, etc. will decrease. There is a risk that the properties are significantly impaired.

[3] Physical properties
The organic compound of the present invention usually has a glass transition temperature of 50 ° C. or higher, but from the viewpoint of heat resistance, the glass transition temperature is preferably 80 ° C. or higher, and more preferably 110 ° C. or higher. The upper limit of the glass transition temperature is usually about 400 ° C.
The organic compound of the present invention usually has a vaporization temperature of 300 ° C. or higher and 800 ° C. or lower.
The organic compound of the present invention preferably has no crystallization temperature between the glass transition temperature and the vaporization temperature.

[4] Ring A to Ring F
Rings A to F in the formulas (I) and (II) each independently represent a benzene ring optionally having an arbitrary substituent.
Specific examples of the optional substituent that the benzene ring of ring A to ring F may have include the following.
An alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl, n-butyl, isobutyl, and a tert-butyl group.)
An alkenyl group which may have a substituent (preferably an alkenyl group having 2 to 9 carbon atoms, such as vinyl, allyl, 1-butenyl group, etc.).
An alkynyl group which may have a substituent (preferably an alkynyl group having 2 to 9 carbon atoms, such as ethynyl and propargyl groups).
An aralkyl group which may have a substituent (preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group).

An optionally substituted amino group [preferably an alkylamino group having one or more optionally substituted alkyl groups having 1 to 8 carbon atoms (for example, methylamino, dimethylamino, diethylamino, And dibenzylamino group.)
An arylamino group having an aromatic hydrocarbon group having 6 to 12 carbon atoms which may have a substituent (for example, phenylamino, diphenylamino, ditolylamino group, etc.).
A heteroarylamino group having a 5- or 6-membered aromatic heterocyclic ring which may have a substituent (for example, pyridylamino, thienylamino, dithienylamino group, etc.).
An acylamino group having an acyl group having 2 to 10 carbon atoms which may have a substituent (for example, acetylamino, benzoylamino group, etc.)]
An alkoxy group that may have a substituent (preferably an alkoxy group having 1 to 8 carbon atoms that may have a substituent, such as methoxy, ethoxy, and butoxy groups).

An aryloxy group which may have a substituent (preferably an aromatic hydrocarbon group having 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy and 2-naphthyloxy groups) )
A heteroaryloxy group which may have a substituent (preferably has a 5- or 6-membered aromatic heterocyclic group, and examples thereof include a pyridyloxy and thienyloxy group).
An acyl group which may have a substituent (preferably an acyl group having 2 to 10 carbon atoms which may have a substituent, such as formyl, acetyl and benzoyl groups).
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 10 carbon atoms which may have a substituent, such as methoxycarbonyl and ethoxycarbonyl groups).
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 7 to 13 carbon atoms which may have a substituent, such as a phenoxycarbonyl group).

An alkylcarbonyloxy group which may have a substituent (preferably an alkylcarbonyloxy group having 2 to 10 carbon atoms which may have a substituent, such as an acetoxy group).
A halogen atom (preferably a fluorine atom or a chlorine atom)
Carboxy group
Cyano group
Hydroxyl group
Mercapto group
An alkylthio group which may have a substituent (preferably an alkylthio group having 1 to 8 carbon atoms, such as a methylthio group and an ethylthio group).
An arylthio group which may have a substituent (preferably an arylthio group having 6 to 12 carbon atoms, such as a phenylthio group and a 1-naphthylthio group).
A sulfonyl group which may have a substituent (for example, a mesyl group, a tosyl group, etc.).
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.).
An optionally substituted boryl group (eg, a dimesitylboryl group).
A phosphino group which may have a substituent (for example, a diphenylphosphino group).

An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. And monovalent groups derived from 5- or 6-membered monocyclic rings or 2 to 5 condensed rings.)
An aromatic heterocyclic group which may have a substituent (for example, 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, Monovalent groups derived from 5- or 6-membered monocyclic or 2-4 condensed rings such as pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring Can be mentioned.)
When the said substituent further has a substituent, the said exemplary substituent is mentioned as the substituent.

  From the viewpoint of improving electrochemical durability and improving heat resistance, the substituent of the benzene ring of ring A to ring F is preferably an aromatic hydrocarbon group which may have a substituent, More preferably, it may be a phenyl which may have a substituent or a naphthyl group which will be described later, an unsubstituted, a 1 or 2 substituted phenyl group, or a naphthyl group which will be described later (however, the number of the substituents is The rings A to F in formulas (I) and (II) are not included as substituents.

[5] Particularly preferred partial structure
In order to improve durability against repeated electrical one-electron oxidation and neutralization, each of the rings D, E, and F in the triphenylamine partial skeleton represented by the formula (II) includes a triphenylamine moiety. It preferably has an optional substituent at the p-position with respect to the N atom at the center of the skeleton (examples of preferred substituents are the same as those of preferred substituents for rings A to F). In particular, the triphenylamine partial skeleton is most preferably a tris (4-biphenyl) amine skeleton represented by the following formula (III).

(In Formula (III), Ring D to Ring I each independently represents a benzene ring which may have a substituent, provided that the substituents of Ring D to Ring I are bonded to each other. The compound has two or more naphthalene rings in one molecule by forming a naphthalene ring together with the ring or by binding a naphthalene ring to rings D to I directly or via other groups.
In formula (III), ring G to ring I may have a substituent, and examples of the substituent include those exemplified as the substituents of ring A to ring F above. However, although it is preferable that the ring D to the ring F have no substituent other than that represented by the above formula (III) in terms of having high charge transporting ability, in terms of having high solubility in an organic solvent. And preferably have a substituent. Furthermore, in formula (III), ring H, ring I or ring G has a carbazole ring bonded to the meta position with respect to the bonding position of ring E, ring F or ring D to which each is bonded. Is preferred. In particular, it is preferable that all of ring H, ring I, and ring G have a carbazole ring bonded to the meta position.

  In order to further improve the solubility in an organic solvent, the organic compound of the present invention preferably has an m-phenylene group represented by the following formula (IV) in the molecule, and in particular, m-phenylene. More preferably, the 2,4,5,6-position of the group is a hydrogen atom, that is, the carbons other than the two bonds of the m-phenylene group have no substituent.

(In formula (IV), the benzene ring may have a substituent.
However, the substituents of the benzene ring in the formula (IV) are bonded to each other to form a naphthalene ring together with these rings, or the naphthene ring in the formula (IV) directly or via another group , The compound has two or more naphthalene rings in one molecule. )
In particular, the organic compound of the present invention preferably has 2 or more m-phenylene groups represented by the above formula (IV) in the molecule, and more preferably 3 or more and 10 or less. When it has too many m-phenylene groups, there exists a possibility that heat resistance may fall.

  In order to improve both the heat resistance and the solubility in an organic solvent, the m-phenylene group is preferably bonded to a carbazole ring. In particular, the organic compound of the present invention has an intramolecular structure. It is most preferable to have a 3- (N-carbazolyl) phenyl group represented by the following formula (IVa). The 3- (N-carbazolyl) phenyl group may have a substituent, but is preferably unsubstituted.

(In formula (IVa), the benzene ring and the carbazole ring may have a substituent.
However, the substituents of the benzene ring and the carbazole ring in the formula (IVa) are bonded to each other to form a naphthalene ring together with these rings, or directly to the benzene ring and the carbazole ring in the formula (IVa) or other When the naphthalene ring is bonded via a group, the compound has two or more naphthalene rings in one molecule. )
In addition, a compound composed only of a benzene ring, an aromatic heterocycle having a nitrogen atom as a heteroatom, and a partial structure selected from the group consisting of nitrogen atoms is an aromatic heterocycle having a nitrogen atom as a benzene ring and a heteroatom. A compound formed by bonding only a ring or an atom selected from the group consisting of a ring and a nitrogen atom. That is, an alkyl group, an alkoxy group, an aryloxy group and the like are not included in the compound.

[Naphthalene ring]
Two or more naphthalene rings contained in the organic compound of the present invention may have a substituent or may not have a substituent.
When it has a substituent, the number of substituents that the naphthalene ring has is usually 3 or less, preferably 2 or less.

When the naphthalene ring has one substituent, the a pattern in the naphthalene ring shown in the following “[6] Bonding position group of naphthalene ring” in the specific example is used from the viewpoint of durability. It is preferable to include.
[6] Bonding position group of naphthalene ring

“7” Exemplified Compound Preferred specific examples of the organic compound of the present invention are listed below, but the organic compound of the present invention is not limited to the following exemplified compounds.

<Use of the organic compound of the present invention>
The organic compound of the present invention is preferably used as a light emitting material and a charge transport material (charge transporting compound), and is preferably used as a light emitting material and a charge transport material for a light emitting layer in an organic electroluminescent device. It is preferable to be used as a material.
Moreover, since the manufacturing method can be simplified, the organic compound of the present invention is preferably used for an organic layer formed by a wet film forming method.

In addition, the organic compound of this invention can be used suitably also for an electrophotographic photoreceptor, a photoelectric conversion element, an organic solar cell, an organic rectifying element, etc. besides an organic electroluminescent element.
<Synthesis Method of Organic Compound>
The organic compound of the present invention can be prepared by reacting only one allylamine compound with an allylamine compound to form a secondary allylamine compound and then further reacting with the halogenated allyl compound (Method 1), or dihalogenodiallylamine. There is a method (method 2) in which an allylboronic acid is reacted and then an allyl halide compound is reacted.

As a reaction for forming an N—Ar bond with an amine and a halogenated compound, a coupling reaction such as a Buch Barto-Hartwig reaction using a Pd complex, an Ullmann reaction using copper, or the like can be used. As a method of reacting the compound with allylboronic acid, Suzuki coupling or the like can be used.

(Ar in the formula represents an arbitrary allyl group, and a plurality of Ars may be the same as or different from each other.)
<Composition for organic electroluminescence device>
The composition for organic electroluminescent elements of the present invention contains the organic compound of the present invention and a solvent.
The content of the organic compound of the present invention in the composition for organic electroluminescent elements is usually 5 parts by weight or more, preferably 10 parts by weight or more, and usually 99 parts by weight or less, preferably 95 parts by weight or less. By setting it within this range, the effect of improving the light emission efficiency and lowering the voltage of the element can be obtained. In addition, the organic compound of the present invention may be included in the composition alone or in combination of two or more.

[solvent]
The solvent contained in the composition for organic electroluminescent elements of the present invention is not particularly limited as long as the solute such as the organic compound of the present invention dissolves well, but aromatic compounds and aliphatic ketone compounds are used. It is preferable to use the organic compound because it dissolves well.
Examples of the aromatic compound include aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, and trichlorobenzene; 1,2-dimethoxybenzene, 1, Aromatic ethers such as 3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole; phenyl acetate, phenyl propionate, Aromatic esters such as methyl benzoate, ethyl benzoate, propyl benzoate, n-butyl benzoate;
Examples of the aliphatic ketone include ketones having an alicyclic ring such as cyclohexanone, cyclooctanone, cyclopentanone, and trimethylcyclohexanone; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; and methyl ethyl ketone.

  In addition, alcohols having an alicyclic ring such as cyclohexanol and cyclooctanol; aliphatic alcohols such as butanol and hexanol; aliphatics such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA) Ether; Aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate and n-butyl lactate can be used.

Of these, aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, tetralin and the like are preferable in that they have low water solubility and are not easily altered.
Since organic electroluminescent devices use many materials such as cathodes that deteriorate significantly due to moisture, the presence of moisture in the composition causes moisture to remain in the dried film, degrading the device characteristics. The possibility is considered and it is not preferable.

  Examples of the method for reducing the amount of water in the composition include dehydration of the solvent in advance by distillation or use of a desiccant, nitrogen gas sealing, use of a solvent with low water solubility, and the like. In particular, it is preferable to use a solvent having low water solubility because the solution film can prevent whitening by absorbing moisture in the atmosphere during the wet film forming process. From such a viewpoint, the composition for organic electroluminescent elements to which the present embodiment is applied includes, for example, a solvent having a water solubility at 25 ° C. of 1% by weight or less, preferably 0.1% by weight or less. It is preferable to contain 10% by weight or more in the composition.

  Further, in order to reduce a decrease in film formation stability due to evaporation of the solvent from the composition during wet film formation, the solvent of the composition for organic electroluminescent elements has a boiling point of 100 ° C. or higher, preferably a boiling point of 150. It is effective to use a solvent having a boiling point of 200 ° C. or higher, more preferably 200 ° C. or higher. In order to obtain a more uniform film, it is necessary for the solvent to evaporate from the liquid film immediately after the film formation at an appropriate rate. For this purpose, the boiling point is usually 80 ° C. or higher, preferably the boiling point is 100 ° C. or higher. It is effective to use a solvent having a boiling point of 120 ° C. or more, usually less than 270 ° C., preferably less than 250 ° C., more preferably less than 230 ° C.

A solvent that satisfies the above-mentioned conditions, ie, solute solubility, evaporation rate, and water solubility conditions, may be used alone. However, if a solvent that satisfies all the conditions cannot be selected, two or more solvents may be mixed. It can also be used.
[Light emitting material]
It is preferable that the composition for organic electroluminescent elements of the present invention further contains a luminescent material.

A luminescent material refers to the component which mainly light-emits in the composition for organic electroluminescent elements of this invention, and corresponds to the dopant component in an organic EL device. Of the amount of light (unit: cd / m ² ) emitted from the composition for organic electroluminescent elements, it is usually 10 to 100%, preferably 20 to 100%, more preferably 50 to 100%, and most preferably 80 to 100%. If% is identified as luminescence from a component material, it is defined as the luminescent material.

As the luminescent material, any known material can be applied, and a fluorescent luminescent material or a phosphorescent luminescent material can be used alone or in combination. A phosphorescent luminescent material is preferable from the viewpoint of internal quantum efficiency.
For the purpose of improving the solubility in a solvent, it is also important to reduce the symmetry and rigidity of the light emitting material molecule or to introduce a lipophilic substituent such as an alkyl group.

Fluorescent dyes that emit blue light include perylene, pyrene, anthracene, coumarin, p
-Bis (2-phenylethenyl) benzene and derivatives thereof. Examples of the green fluorescent dye include quinacridone derivatives and coumarin derivatives. Examples of yellow fluorescent dyes include rubrene and perimidone derivatives. Examples of red fluorescent dyes include DCM compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

Examples of the phosphorescent material include organometallic complexes containing a metal selected from Groups 7 to 11 of the periodic table.
Preferred examples of the metal in the phosphorescent organometallic complex containing a metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Preferred examples of these organometallic complexes include compounds represented by the following formula (V) or the following formula (VI).

ML _(q−j) L ′ _j (V)
(In formula (V), M represents a metal, q represents the valence of the metal, L and L ′ represent a bidentate ligand, and j represents 0, 1 or 2.)

(In the formula (VI), ^{M d} represents a metal, T is ^.R 92 ^{to R 95} that represents a carbon or nitrogen, each independently represent a substituent. However, when T is ^{nitrogen, R 94} and R ^There is no ^95. )
Hereinafter, the compound represented by formula (V) will be described first.
In the formula (V), M represents an arbitrary metal, and specific examples of preferable ones include the metals described above as metals selected from Groups 7 to 11 of the periodic table.

  Further, the bidentate ligands L and L ′ in the formula (V) each represent a ligand having the following partial structure.

  L ′ is particularly preferably the following from the viewpoint of the stability of the complex.

In the partial structures of L and L ′, the ring A1 represents an aromatic hydrocarbon group or an aromatic heterocyclic group, and these may have a substituent. Ring A2 represents a nitrogen-containing aromatic heterocyclic group, and these may have a substituent.
When the rings A1 and A2 have a substituent, preferred substituents include halogen atoms such as fluorine atoms; alkyl groups such as methyl groups and ethyl groups; alkenyl groups such as vinyl groups; methoxycarbonyl groups and ethoxycarbonyl groups. Alkoxycarbonyl groups; alkoxy groups such as methoxy groups and ethoxy groups; aryloxy groups such as phenoxy groups and benzyloxy groups; dialkylamino groups such as dimethylamino groups and diethylamino groups; diarylamino groups such as diphenylamino groups; carbazolyl groups; An acyl group such as an acetyl group; a haloalkyl group such as a trifluoromethyl group; a cyano group; an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, and a phenanthyl group.

  More preferred examples of the compound represented by the formula (V) include compounds represented by the following formulas (Va), (Vb), and (Vc).

(In formula (Va), M ^a represents the same metal as M, w represents the valence of the metal, and ring A1 represents an aromatic hydrocarbon group which may have a substituent, Ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.

(In the formula (Vb), M ^b represents the same metal as M, w represents the valence of the metal. Further, the ring A1 is an aromatic optionally substituted hydrocarbon group or an optionally substituted And ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.

(In the formula (Vc), M ^c represents the same metal as M, w represents the valence of the metal, and j represents 0, 1 or 2. Furthermore, ring A1 and ring A1 ′ are Each independently represents an optionally substituted aromatic hydrocarbon group or an optionally substituted aromatic heterocyclic group, and ring A2 and ring A2 ′ are each independently (It represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.)
In the above formulas (Va), (Vb), and (Vc), the group of ring A1 and ring A1 ′ is preferably, for example, phenyl group, biphenyl group, naphthyl group, anthryl group, thienyl group, furyl group, benzothienyl. Group, benzofuryl group, pyridyl group, quinolyl group, isoquinolyl group, carbazolyl group and the like.

In addition, the group of ring A2 and ring A2 ′ is preferably a pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, benzimidazole group, quinolyl group, isoquinolyl group, quinoxalyl group, A phenanthridyl group and the like can be mentioned.
Furthermore, the substituents that the compounds represented by the formulas (Va), (Vb), and (Vc) may have include halogen atoms such as fluorine atoms; alkyl groups such as methyl groups and ethyl groups; vinyl groups Alkenyl groups such as methoxycarbonyl group and ethoxycarbonyl group; alkoxy groups such as methoxy group and ethoxy group; aryloxy groups such as phenoxy group and benzyloxy group; dialkylamino groups such as dimethylamino group and diethylamino group A diarylamino group such as a diphenylamino group; a carbazolyl group; an acyl group such as an acetyl group; a haloalkyl group such as a trifluoromethyl group; a cyano group;

  When the said substituent is an alkyl group, the carbon number is 1 or more and 6 or less normally. Furthermore, when the substituent is an alkenyl group, the carbon number is usually 2 or more and 6 or less. When the substituent is an alkoxycarbonyl group, the carbon number is usually 2 or more and 6 or less. Further, when the substituent is an alkoxy group, the carbon number is usually 1 or more and 6 or less. Moreover, when a substituent is an aryloxy group, the carbon number is 6 or more and 14 or less normally. Furthermore, when the substituent is a dialkylamino group, the carbon number is usually 2 or more and 24 or less. Further, when the substituent is a diarylamino group, the carbon number is usually 12 or more and 28 or less. Furthermore, when the substituent is an acyl group, the carbon number is usually 1 or more and 14 or less. Moreover, when a substituent is a haloalkyl group, the carbon number is 1 or more and 12 or less normally.

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. Two fused rings may be formed. Examples of such a condensed ring group include a 7,8-benzoquinoline group.
Among them, 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 group are more preferable. Is mentioned.

Further, the formula (Va), (Vb), preferably as ^{M a, M b, M c} in (Vc), ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold.
Specific examples of the organometallic complex represented by the above formula (V), (Va), (Vb) or (Vc) are shown below, but are not limited to the following compounds (in the following, Ph is a phenyl group) Represents.)

Among the organometallic complexes represented by the above formulas (V), (Va), (Vb), and (Vc), in particular, as the ligand L and / or L ′, a 2-arylpyridine-based ligand, A compound having 2-arylpyridine, a compound in which an arbitrary substituent is bonded thereto, and a compound in which an arbitrary group is condensed to this is preferable.
Next, the compound represented by the formula (VI) will be described.

In the formula (VI), M ^d represents a metal, and specific examples thereof 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 (VI), 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, R ⁹⁴ and R ⁹⁵ each independently represent a substituent represented by the same examples as R ⁹² and R ⁹³ . Further, as described above, when T is nitrogen, R ⁹⁴ and R ⁹⁵ are absent.
R ^{92 to} R ⁹⁵ may further have a substituent. In this case, the substituent which may further be present is not particularly limited, and any group can be used as the substituent.

Furthermore, R ^{92 to} R ⁹⁵ may be connected to each other to form a ring, and this ring may further have an arbitrary substituent.
Specific examples (T-1, T-10 to T-15) of the organometallic complex represented by the formula (VI) are shown below, but are not limited to the following exemplified compounds. In the following, Me represents a methyl group, and Et represents an ethyl group.

Moreover, as an organometallic complex, the compound as described in an international publication 2005/019373 pamphlet can also be used.
[Charge transport material]
Although the composition for organic electroluminescent elements of the present invention preferably contains the organic compound of the present invention as a charge transport material, it may contain other charge transport materials.

As other charge transport materials that may be contained, in addition to the various compounds exemplified as the (low molecular weight hole transport compound) in the hole injection layer 3 described above, for example, 4,4′-bis [ An aromatic diamine represented by N- (1-naphthyl) -N-phenylamino] biphenyl and containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms No. 234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine and other aromatic amine compounds having a starburst structure (Journal)
of Luminescence, 1997, Vol. 72-74, pp. 985), an aromatic amine compound composed of a tetramer of triphenylamine (Chemical Communications, 1996, pp. 2175), 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′- Spiro compounds such as spirobifluorene (Synthetic Metals, 1997, Vol. 91, pp. 209).

Although the preferable specific example of the charge transport material which can be used together below is shown, this invention is not limited to these.
The charge transporting material used in combination includes a compound having a hole transporting ability (hereinafter referred to as a hole transporting material) and a compound having an electron transporting ability (electron transporting material). In general, it is preferably 0: 100 or less, preferably 2:98 or less, and usually 100: 0 or more, preferably 98: 2 or more.

Within the above range, it is preferable in that the movement balance of holes and electrons is improved, an element having a long driving life and high current efficiency is obtained.
Examples of the hole transport material include compounds having triarylamine or carbazole as a partial structure. Specific examples of the hole transport material are shown below, but are not limited thereto.

Examples of the electron transport material include compounds having an aromatic heterocyclic ring as a partial structure.
Examples of the aromatic heterocycle include a pyridine ring, a quinoline ring, a quinoxaline ring, a pyrimidine ring, and a triazine ring. Specific examples of the charge transport material are shown below, but are not limited thereto.

When a charge transport material other than the organic compound of the present invention is included, the concentration of the charge transport material in the composition is usually 80% by weight or less, preferably 70% by weight or less. Since the charge transport material other than the organic compound of the present invention may not be contained, the lower limit is usually 0% by weight or more.
[Other ingredients]
In the composition for organic electroluminescent elements of the present invention, various other solvents may be included as necessary in addition to the above-described solvents and light emitting materials. Examples of such other solvents include amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide.

Moreover, various additives, such as a leveling agent and an antifoamer, may be included.
In addition, when two or more layers are laminated by a wet film formation method, in order to prevent these layers from being compatible with each other, a photocurable resin or a thermosetting resin is used for the purpose of curing and insolubilizing after film formation. Can also be contained.

[Material concentration and blending ratio in composition for organic electroluminescence device]
The solid content concentration of the charge transport material, the luminescent material, and components (leveling agents, etc.) that can be added as necessary in the composition for organic electroluminescent elements of the present invention is usually 0.01% by weight or more, preferably 0. 0.05% by weight or more, more preferably 0.1% by weight or more, more preferably 0.5% by weight or more, most preferably 1% by weight or more, and usually 80% by weight or less, preferably 50% by weight or less, more It is preferably 40% by weight or less, more preferably 30% by weight or less, and most preferably 20% by weight or less. When this concentration is below the lower limit, it is difficult to form a thick film when forming a thin film, and when it exceeds the upper limit, it is difficult to form a thin film.

  In the composition for organic electroluminescent elements of the present invention, the weight mixing ratio of the light emitting material / charge transporting material is usually 0.1 / 99.9 or more, more preferably 0.5 / 99.5 or more. More preferably, it is 1/99 or more, most preferably 2/98 or more, usually 50/50 or less, more preferably 40/60 or less, and further preferably 30/70 or less. Most preferably, it is 20/80 or less. If this ratio falls below the lower limit or exceeds the upper limit, the luminous efficiency may be significantly reduced.

[Properties, physical properties, etc. of composition for organic electroluminescence device]
(Moisture concentration)
In the case of producing an organic electroluminescent element by forming a layer by a wet film forming method using the composition for organic electroluminescent element of the present invention, if water is present in the composition for organic electroluminescent element to be used, the formed film Since moisture is mixed and the uniformity of the film is impaired, the water content in the composition for organic electroluminescent elements of the present invention is preferably as low as possible. In general, since organic electroluminescent devices use many materials such as cathodes that deteriorate significantly due to moisture, when moisture is present in the composition for organic electroluminescent devices, moisture remains in the dried film. However, there is a possibility of deteriorating the characteristics of the element, which is not preferable.

Specifically, the amount of water contained in the composition for organic electroluminescent elements of the present invention is usually 1% by weight or less, preferably 0.1% by weight or less, more preferably 0.01% by weight or less.
As a method for measuring the moisture concentration in the composition for organic electroluminescent elements, the method described in Japanese Industrial Standard “Method for Measuring Moisture of Chemical Products” (JIS K0068: 2001) is preferable. For example, the Karl Fischer reagent method (JIS K0211). -1348) and the like.

(Uniformity)
The composition for organic electroluminescent elements of the present invention is preferably in a uniform liquid state at room temperature in order to enhance stability in a wet film forming process, for example, ejection stability from a nozzle in an ink jet film forming method. . The uniform liquid at normal temperature means that the composition is a liquid composed of a uniform phase and does not contain a particle component having a particle size of 0.1 μm or more in the composition.

(Physical properties)
Regarding the viscosity of the composition for organic electroluminescent elements of the present invention, when the viscosity is extremely low, for example, coating surface non-uniformity due to excessive liquid film flow in the film forming process, nozzle ejection failure in ink jet film formation, etc. are likely to occur. In the case of extremely high viscosity, nozzle clogging or the like in ink jet film formation is likely to occur. For this reason, the viscosity at 25 ° C. of the composition of the present invention is usually 2 mPa · s or more, preferably 3 mPa · s or more, more preferably 5 mPa · s or more, and usually 1000 mPa · s or less, preferably 100 mPa · s or less. More preferably, it is 50 mPa · s or less.

Further, when the surface tension of the composition for organic electroluminescent elements of the present invention is high, the wettability of the film forming liquid to the substrate is lowered, the leveling property of the liquid film is poor, and the film formation surface is disturbed during drying. Since the problem of becoming easy occurs, the surface tension at 20 ° C. of the composition of the present invention is usually less than 50 mN / m, preferably less than 40 mN / m.
Furthermore, when the vapor pressure of the composition for organic electroluminescent elements of the present invention is high, problems such as a change in solute concentration due to evaporation of the solvent tend to occur. For this reason, the vapor pressure at 25 ° C. of the composition of the present invention is usually 50 mmHg or less, preferably 10 mmHg or less, more preferably 1 mmHg or less.

[Thin film for organic electroluminescence device]
The thin film for an organic electroluminescent device of the present invention formed by a wet film formation method using the composition for an organic electroluminescent device of the present invention is a film that is difficult to crystallize, has excellent luminescent properties and heat resistance, and is usually organic. Used as a layer between the cathode and anode of the electroluminescent device.
Here, the wet film forming method is a spin coating method, a dip coating method, a die coating method, a bar coating method, a blade coating method, a roll coating method, a spray coating method, a capillary coating method, an ink jet method, a screen printing method, and a gravure printing. A method of forming a film by a wet method such as a method or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable. This is because the liquid property specific to the coating composition used for the organic electroluminescent element is matched.

The film thickness of the thin film for organic electroluminescent elements of the present invention is appropriately determined depending on the application. For example, in the case of a light emitting layer of an organic electroluminescent element, as described later, it is usually 10 nm or more, preferably 20 nm or more, usually 300 nm. Below, it is preferably 200 nm or less, or usually 30 nm or more, preferably 50 nm or more, usually 500 nm or less, preferably 300 nm or less.
[Organic electroluminescence device]
The organic electroluminescent element of the present invention has at least an anode, a cathode, and a light emitting layer provided between both electrodes on a substrate, and is wet-film-formed using the composition for organic electroluminescent elements of the present invention. It has the layer formed by the method. The layer formed by the wet film formation method is preferably the light emitting layer.

FIG. 1 is a schematic cross-sectional view showing a structure example suitable for the organic electroluminescent device of the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a light emitting layer, Each of the electron injection layers 6 represents a cathode.
[1] Substrate
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, or polysulfone 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.

[2] Anode
An anode 2 is provided on the substrate 1. The anode 2 plays a role of hole injection into a layer on the light emitting layer side (such as the hole injection layer 3 or the light emitting layer 4).
This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or A conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline is used.

  In general, the anode 2 is often formed by sputtering, vacuum deposition, 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, or conductive polymer fine powder, an appropriate binder resin solution is used. The anode 2 can also be formed by dispersing and coating the substrate 1. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.

  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 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, and is usually formed on the anode 2.
The method for forming the hole injection layer 3 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 injection layer 3 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When forming the hole injection layer 3 by wet film formation, the material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (hole injection layer solvent) to form a film-forming composition (positive A composition for forming a hole injection layer), and applying the composition for forming a hole injection layer on a layer (usually an anode) corresponding to the lower layer of the hole injection layer 3 by an appropriate technique. The hole injection layer 3 is formed by coating and 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 2 to the hole injection layer 3. 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 3 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 (1).

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

(In 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 (1) 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.

Furthermore, as the hole transporting compound, a crosslinkable compound described in the section of [Hole transporting layer] described later may be used. When a crosslinkable compound is used, the film forming method is the same.
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, 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; 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, usually 1
It is 00 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 on the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film formation, and dried. The hole injection layer 3 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, an infrared ray, a halogen heater, and microwave irradiation. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  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 equal to or higher 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 the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles installed (in case of using two or more 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 types When using the above materials, heat each crucible) and control the evaporation amount to evaporate (when using two or more materials, control each evaporation amount independently) and face the crucible Then, the hole injection layer 3 is formed on the anode 2 of the substrate placed on the substrate. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

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, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less. 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 method for forming the hole transport layer 4 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 4 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The hole transport layer 4 can be formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3. 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 4 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, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

Such a material for the hole transport layer 4 may be any material conventionally used as a constituent material for the hole transport layer. For example, the hole transport property used for the hole injection layer 3 described above. What was illustrated as a compound is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives,
Examples include triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes, and the like.

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

Of these, polyarylamine derivatives and polyarylene derivatives are preferred.
The polyarylamine derivative is preferably a polymer containing a repeating unit represented by the following formula (2). In particular, the polymer is preferably a polymer composed of a repeating unit represented by the following formula (2). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In formula (2), 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 a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a pyrene ring, a thiophene ring, a pyridine ring, a fluorene from the viewpoint of solubility and heat resistance in an organic solvent. A group derived from a ring selected from the group consisting of rings or a group formed by linking two or more benzene rings (for example, a biphenyl group (biphenylene group) or a terphenyl group (terphenylene group)) is preferable.

Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.
Examples of the substituent that the aromatic hydrocarbon group and 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 (2) is used as its repeating unit. The polymer which has is mentioned.
As a polyarylene derivative, the polymer which has a repeating unit which consists of following formula (III-1) and / or following formula (III-2) is preferable.

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

(In formula (III-2), R ^e and R ^f are each independently the same as R ^a , R ^b , R ^c or R ^d in formula (III-1). 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 (2).
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.

In the case of forming the hole transport layer 4 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 3 and then heated and dried 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 3.

When the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as in the case of forming the hole injection layer 3.
The hole transport layer 4 may contain various light emitting materials, electron transport compounds, binder resins, coating property improving agents, and the like in addition to the hole transport compound.
The hole transport layer 4 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. Particularly, the hole transporting compound is preferably a polymer containing a repeating unit having a crosslinkable group, and the above formula (2) 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 4 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 deposited by wet film formation. To crosslink.
The composition for forming a hole transport layer may contain an additive for promoting a crosslinking reaction in addition to the crosslinking compound. Examples of additives that accelerate the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds.

Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound; a binder resin;
In the composition for forming a hole transport layer, the crosslinkable compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20%. It is contained 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 the lower layer (usually the hole injection layer 3), the composition is crosslinked by heating and / or irradiation with active energy such as light. Are crosslinked to form a network polymer compound.
Conditions such as temperature and humidity during film formation are the same as those during the wet film formation of the hole injection layer 3.
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 coated film 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 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.
[4] Light emitting layer
A light emitting layer 4 is usually provided on the hole injection layer 3. The light emitting layer 4 is, for example, a layer containing the above-described light emitting material. Between the electrodes to which an electric field is applied, holes injected from the anode 2 through the hole injection layer 3 and from the cathode 6 through the electron transport layer 5 are injected. It is a layer that is excited by recombination with other electrons and becomes a main light source. The light-emitting layer 4 preferably contains a light-emitting material (dopant) and one or more host materials, and the light-emitting layer 4 more preferably contains the organic compound of the present invention as a host material, and is formed by a vacuum evaporation method. However, it is particularly preferable that the layer be prepared by a wet film-forming method using the composition for organic electroluminescent elements of the present invention.

Here, the wet film forming method is, as described above, a composition containing a solvent, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating. This method is a wet film formation method such as a method, an ink jet method, a screen printing method, a gravure printing method, or a flexographic printing method.
In addition, the light emitting layer 4 may contain other materials and components as long as the performance of the present invention is not impaired.

  In general, when the same material is used in the organic electroluminescent element, the thinner the film thickness between the electrodes, the larger the effective electric field, so that the injected current increases, so the driving voltage decreases. For this reason, the driving voltage of the organic electroluminescence device decreases when the total film thickness between the electrodes is thin, but if it is too thin, a short circuit occurs due to the protrusion caused by the electrode such as ITO. Necessary.

  In the present invention, in addition to the light emitting layer 4, when the organic layer such as the hole injection layer 3 and the electron transport layer 5 described later is provided, the light emitting layer 4 and other organic materials such as the hole injection layer 3 and the electron transport layer 5 are used. The total film thickness combined with the layer is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more, usually 1000 nm or less, preferably 500 nm or less, and more preferably 300 nm or less. In addition, when the conductivity of the hole injection layer 3 other than the light emitting layer 4 and the electron injection layer 5 described later is high, the amount of charge injected into the light emitting layer 4 increases. It is also possible to reduce the drive voltage while increasing the thickness to reduce the thickness of the light emitting layer 4 and maintaining the total thickness to some extent.

Therefore, the thickness of the light emitting layer 4 is usually 10 nm or more, preferably 20 nm or more, and usually 300 nm or less, preferably 200 nm or less. When the element of the present invention has only the light emitting layer 4 between the anode and the cathode, the thickness of the light emitting layer 4 is usually 30 nm or more, preferably 50 nm or more, usually 500 nm or less, preferably 300 nm or less. is there.
[5] Electron injection layer
The electron injection layer 5 serves to efficiently inject electrons injected from the cathode 6 into the light emitting layer 4. In order to perform electron injection efficiently, the material for forming the electron injection layer 5 is preferably a metal having a low work function, and alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium are used.

The film thickness of the electron injection layer 5 is preferably 0.1 to 5 nm.
Also, an ultrathin insulating film (0.1 to 5 nm) such as LiF, MgF ₂ , Li ₂ O, Cs ₂ CO ₃ may be inserted at the interface between the cathode 6 and the light emitting layer 4 or the electron transport layer 8 described later. This is an effective method for improving the efficiency of the device (Appl. Phys. Lett., 70, 152, 1997; JP-A-10-74).
586 publication; IEEE Trans. Electron. Devices, 44, 1245, 1997; SID 04 Digest, 154).

In addition, organic electron transport materials represented by metal complexes such as nitrogen-containing heterocyclic compounds such as bathophenanthroline and aluminum complexes of 8-hydroxyquinoline described later are doped with alkali metals such as sodium, potassium, cesium, lithium and rubidium. (Japanese Patent Laid-Open Nos. 10-270171, 2002-100478, 2002-10048)
2), it is preferable because the electron injecting / transporting property is improved and excellent film quality can be achieved. The film thickness in this case is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

The electron injection layer 5 is formed by laminating on the light emitting layer 4 by a wet film forming method or a vacuum deposition method in the same manner as the light emitting layer 4. In the case of the vacuum vapor deposition method, the vapor deposition source is put in a crucible or metal boat installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with an appropriate vacuum pump, and then the crucible or metal boat is Evaporate by heating to form an electron injection layer on the substrate placed facing the crucible or metal boat.

The alkali metal is deposited using an alkali metal dispenser in which nichrome is filled with an alkali metal chromate and a reducing agent. By heating the dispenser in a vacuum container, the alkali metal chromate is reduced and the alkali metal is evaporated. In the case of co-evaporating the organic electron transport material and the alkali metal, the organic electron transport material is put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump. Each crucible and dispenser are simultaneously heated and evaporated to form an electron injection layer on the substrate placed facing the crucible and dispenser.

At this time, co-evaporation is uniformly performed in the film thickness direction of the electron injection layer 5, but there may be a concentration distribution in the film thickness direction.
The electron injection layer 5 may be omitted as shown in FIGS.
[6] Cathode
The cathode 6 plays a role of injecting electrons into a layer on the light emitting layer side (such as the electron injection layer 5 or the light emitting layer 4). The material used for the cathode 6 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, such as 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.

The film thickness of the cathode 6 is usually the same as that of the anode 2. For the purpose of protecting the cathode made of a low work function metal, further laminating a metal layer having a high work function and stable to the atmosphere on the cathode increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.
[7] Other constituent layers
As described above, the element having the layer structure shown in FIG. 1 has been mainly described. However, the above description is provided as long as the performance is not impaired between the anode 2 and the cathode 6 and the light emitting layer 4 in the organic electroluminescent element of the present invention. In addition to the layers, any layer may be included, and any layer other than the light emitting layer 4 may be omitted.

Examples of the layer that may be included include the electron transport layer 7. The electron transport layer 7 is provided between the light emitting layer 4 and the electron injection layer 5 as shown in FIG. 2 for the purpose of further improving the light emission efficiency of the device.
The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode 6 between electrodes to which an electric field is applied in the direction of the light emitting layer 4. As the electron transporting compound used for the electron transport layer 7, the electron injection efficiency from the cathode 6 or the electron injection layer 5 is high, and the injected electrons can be efficiently transported with high electron mobility. It must be a compound.

Materials 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, Styryl biphenyl derivative, silole derivative, 3- or 5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound No. 207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N′-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide, n-type sulfide Examples include zinc and n-type zinc selenide.

The lower limit of the thickness of the electron transport layer 7 is usually 1 nm, preferably about 5 nm, and the upper limit is usually about 300 nm, preferably about 100 nm.
The electron transport layer 7 is formed by laminating on the light emitting layer 4 by the wet film formation method or the vacuum deposition method in the same manner as the hole injection layer 3. Usually, a vacuum deposition method is used.
In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting substance, it is also effective to provide the hole blocking layer 8 as shown in FIG. The hole blocking layer 8 has a function of confining holes and electrons in the light emitting layer 4 and improving luminous efficiency. That is, the hole blocking layer 8 is generated by blocking the holes moving from the light emitting layer 4 from reaching the electron transport layer 7, thereby increasing the recombination probability with electrons in the light emitting layer 4. There is a role of confining excitons in the light emitting layer 4 and a role of efficiently transporting electrons injected from the electron transport layer 8 toward the light emitting layer 4.

The hole blocking layer 8 prevents the holes moving from the anode 2 from reaching the cathode 6 and can efficiently transport the electrons injected from the cathode 6 toward the light emitting layer 4. The compound is laminated on the light emitting layer 4 so as to be in contact with the interface of the light emitting layer 4 on the cathode 6 side.
The physical properties required for the material constituting the hole blocking layer 8 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high.

  Examples of the hole blocking layer material satisfying such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Ligand complexes, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, and styryl compounds such as distyrylbiphenyl derivatives ( JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (JP-A-7-41759) And phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297).

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 hole blocking material.
The film thickness of the hole blocking layer 8 is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.
The hole blocking layer 8 can also be formed by the same method as the hole injection layer 3, but a vacuum deposition method is usually used.

The electron transport layer 7 and the hole blocking layer 8 may be appropriately provided as necessary. 1) Only the electron transport layer, 2) Only the hole blocking layer, 3) Stack of hole blocking layer / electron transport layer, 4) There are usages such as not using.
For the same purpose as the hole blocking layer 8, it is also effective to provide an electron blocking layer 9 between the hole injection layer 3 and the light emitting layer 4 as shown in FIG. The electron blocking layer 9 increases the probability of recombination with holes in the light emitting layer 4 by blocking the electrons moving from the light emitting layer 4 from reaching the hole injection layer 3, thereby generating excitons generated. Has a role of confining the light in the light emitting layer 4 and a role of efficiently transporting holes injected from the hole injection layer 3 in the direction of the light emitting layer 4.

The characteristics required for the electron blocking layer 9 include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Further, when the light emitting layer 4 is formed by a wet film forming method, it is preferable that the electron blocking layer 9 is also formed by a wet film forming method because the device manufacturing becomes easy.
For this reason, it is preferable that the electron blocking layer 9 also has wet film forming compatibility, and examples of the material used for such an electron blocking layer 9 include dioctylfluorene typified by F8-TFB in addition to the organic compound of the present invention. And a copolymer of triphenylamine (WO 2004/084260 pamphlet) and the like.

The structure opposite to that shown in FIG. 1, that is, the cathode 6, the electron injection layer 5, the light emitting layer 4, the hole injection layer 3, and the anode 2 can be laminated on the substrate 1 in this order. It is also possible to provide the organic electroluminescent element of the present invention between two substrates, at least one of which is highly transparent. Similarly, it is also possible to laminate | stack to the structure opposite to the said each layer structure shown in FIGS.
Further, a structure in which a plurality of layers shown in FIG. 1 are stacked (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interfacial layer (between the light emitting units) (when the anode is ITO and the cathode is Al, the two layers), for example, V ₂ O ₅ is used as the charge generation layer (CGL). This is more preferable from the viewpoint of luminous efficiency and driving voltage.

  The present invention can be applied to any of an organic electroluminescent element having a single element, an element having a structure arranged in an array, and a structure having an anode and a cathode arranged in an XY matrix.

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

  For example, the organic EL display and the organic EL display of the present invention can be obtained by the method described in “Organic EL display” (Ohm, August 20, 2004, published by Shizushi Tokito, Chiba Adachi, Hideyuki Murata). EL illumination can be formed.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention can be arbitrarily modified and implemented without departing from the gist thereof.
[Synthesis Example of Compound A]

Under a nitrogen atmosphere, tetrakis (trimethyl chloride) was added to a solution of 1-bromo-3-iodobenzene (11.98 g, 42.37 mmol), 1-naphthylboronic acid (6.07 g, 35.31 mmol), toluene (176 ml), ethanol (88 ml) at room temperature. Phenylphosphine) palladium (0) (2.04 g, 1.76 mmol) and 2M aqueous sodium carbonate solution (44 ml) were added, and the mixture was refluxed for 6 hours. After allowing to cool to room temperature, the reaction mixture was extracted with toluene, the organic layer was washed with water, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane / methylene chloride = 1/1) to obtain Intermediate 1 (9.41 g, yield 94%).

Under a nitrogen atmosphere, intermediate 1 (9.41 g, 33.26 mmol), bispinacolatodiborane (10.13 g, 39.91 mmol), potassium acetate (11.09 g, 113.08 mmol) in dehydrated dimethyl sulfoxide (100 m
L) After the suspension was heated to 60 ° C, dichloro [1,1'-bis (diphenylphosphino) ferrocene] palladium (II) dichloromethane adduct (0.81 g, 0.99 mol) was added, and the temperature was raised to 80 ° C. Raised and stirred for 8 hours. After allowing to cool to room temperature, water is added to the reaction mixture, and the precipitated crystals are collected by filtration, dissolved in methylene chloride, magnesium sulfate and white clay are added, and the mixture is stirred and filtered. The filtrate is concentrated, and the residue is concentrated on a silica gel column. Purification by chromatography (hexane / methylene chloride = 2/1) gave Intermediate 2 (8.9 g, yield 82%).

  Under nitrogen atmosphere, tris (4-bromophenyl) amine (6.70 g, 15.67 mmol), MCPB (3 g, 10.45 mmol), toluene (52 ml), ethanol (26 ml) solution was added to tetrakis (triphenylphosphine) palladium ( 0) (0.60 g, 0.522 mmol) and 2M aqueous sodium carbonate solution (13 ml) were added, and the mixture was refluxed for 2 hours. After cooling to room temperature, the reaction mixture was extracted with toluene, the organic layer was washed with brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane / methylene chloride = 5/1 → 3/1 → 2/1) and recrystallized with toluene / cyclohexane to give intermediate 3 (1.75 g, yield 26%) Got.

  Under a nitrogen atmosphere, a solution of intermediate 3 (1.75 g, 2.71 mmol), intermediate 2 (2.24 g, 6.79 mmol), toluene (27.2 ml), ethanol (13.6 ml) at room temperature with tetrakis (triphenylphosphine) palladium ( 0) (0.15 g, 0.13 mmol) and 2M aqueous sodium carbonate solution (6.8 ml) were added, and the mixture was refluxed for 6 hours. After allowing to cool to room temperature, the reaction mixture was extracted with toluene, the organic layer was washed with water, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane / methylene chloride = 3/1), dissolved in methylene chloride, and reprecipitated in methanol to obtain Compound A (2.09 g, yield 86%).

Compound A was confirmed by DEI-MS (m / z = 890 (M ⁺ )).
The glass transition temperature of this product was 124 ° C., and the onset of weight loss under a nitrogen stream was 566 ° C.
[Synthesis Example of Compound B]

  Under nitrogen atmosphere, tris (4-bromophenyl) amine (4 g, 9.34 mmol), 3-biphenylboronic acid (3.7 g, 18.69 mmol), toluene (92 ml) and ethanol (46 ml) were added to tetrakis at room temperature. (Triphenylphosphine) palladium (0) (0.54 g, 0.46 mmol), 2M aqueous sodium carbonate solution (23 ml) was added, and the mixture was refluxed for 4 hours. After allowing to cool to room temperature, water was added to the reaction mixture, extracted with toluene, the organic layer was washed with water, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane / methylene chloride = 4/1) and washed with ethanol to obtain Intermediate I (1.75 g, yield 30%).

  Under a nitrogen atmosphere, a solution of intermediate I (1.75 g, 2.78 mmol), MCPB (0.96 g, 3.34 mmol), toluene (14 ml), ethanol (7 ml) at room temperature with tetrakis (triphenylphosphine) palladium ( 0) (0.16 g, 0.14 mmol), 2M aqueous sodium carbonate solution (3.5 ml) was added, and the mixture was refluxed for 6 hours. After allowing to cool to room temperature, the reaction mixture was extracted with toluene, the organic layer was washed with water, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane / methylene chloride = 4/1 → 3/1), dissolved in methylene chloride, and reprecipitated in ethanol to obtain Compound B (1.95 g, yield 89%). Obtained.

Compound A was confirmed by DEI-MS (m / z = 790 (M ⁺ )).
This had a glass transition temperature of 106 ° C. and a weight loss starting temperature under a nitrogen stream of 546 ° C.
[Creation of organic electroluminescence device]
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, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  Next, the hole injection layer 3 was formed by a wet film formation method as follows. As a material for the hole injection layer 3, a polymer compound having an aromatic amino group of the following formula (PB-1) (weight average molecular weight: 52000, number average molecular weight: 32500) and an electron accepting property of the following structural formula Using the compound (A-2), 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 coat atmosphere Atmosphere 25 ℃
Drying conditions 230 ° C x 60 minutes
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 coat atmosphere 25 ° C in dry nitrogen
Drying conditions 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 the organic compound (HO-2) of the present invention shown below as the charge transport material, and the organic compounds shown below as the light emitting material. An organic electroluminescent element composition shown below is prepared using the compound (DO-1) and the organic compound (DO-2), and is spin-coated on the hole transport layer under the conditions shown below to emit light at a film thickness of 50 nm. A layer was obtained.

<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% by weight
<Spin coating conditions>
Spinner speed 2000rpm
Spinner rotation time 120 seconds
Drying conditions 130 ° C x 60 minutes (under reduced pressure)
A uniform thin film having a thickness of 50 nm was formed by the above spin coating.

Next, a pyridine derivative (HB-1) shown below was laminated as a hole blocking layer at a crucible temperature of 251 to 252 ° C. with a deposition rate of 0.08 to 0.12 nm / second and a thickness of 10 nm. 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 light emission characteristics of this element are as follows.
Luminance / current: 7.2 [cd / A] (@ 100 cd / m ² )
Voltage: 8.2 [V] (@ 100 cd / m ² )
Luminous efficiency: 2.7 [1 m / W] (@ 100 cd / m ² )
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).
[Comparative Example: Production and Evaluation of Organic Electroluminescence Device Using Composition for Organic Electroluminescence Device Containing Charge Transport Material (HO-3)]
An organic electroluminescent element was prepared in the same manner as in the Example except that the compound (HO-3) having the structural formula shown below was used instead of (HO-2) as a material for the light emitting layer and spin coating was performed under the same conditions. Produced.

A uniform thin film (light emitting layer) having a thickness of 50 nm was formed by the above spin coating.
The light emission characteristics of this element are as follows.
Luminance / current: 6.7 [cd / A] (@ 100 cd / m ² )
Voltage: 8.1 [V] (@ 100 cd / m ² )
Luminous efficiency: 2.6 [1 m / W] (@ 100 cd / m ² )
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) = (0.678, 0.320).

The characteristics of the organic electroluminescent elements produced in Example 1 and Comparative Example 1 and the initial luminance was set to 2000 cd / m ² , a DC drive test was performed, and the time until the luminance decreased to 1000 cd / m ² (luminance reduced by 50%) Table 1 summarizes the lifetime.

  As shown in Table 1, it can be seen that the organic electroluminescent device using the organic compound of the present invention has high current efficiency and a long driving life.

The organic compound of the present invention is used in various fields where organic EL optical elements are used, such as flat panel displays (for example, for OA computers and wall-mounted televisions) and light sources (for example, copying machines) that make use of the characteristics of surface emitters. Can be suitably used in the fields of a light source, a liquid crystal display and a backlight light source for instruments), a display panel, a marker lamp, and the like.
Moreover, since the organic compound of the present invention has excellent redox stability, it is useful not only for organic electroluminescent elements but also for general organic devices such as electrophotographic photoreceptors and organic solar cells.

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 (12)

A compound having a partial structure represented by the following formula (I) and a partial structure represented by the following formula (II) in one molecule,
An organic compound having two or more naphthalene rings which may have a substituent in the compound.

(In formulas (I) and (II), ring A to ring F each independently represent a benzene ring which may have a substituent, provided that the substituents of ring A to ring F are bonded to each other. Then, these compounds have two or more naphthalene rings in one molecule by forming a naphthalene ring together with these rings, or by bonding a naphthalene ring to rings A to F directly or via other groups. .) 2. The organic compound according to claim 1, wherein the partial structure represented by the formula (II) in the compound is a partial structure represented by the following formula (III).

(In Formula (III), Ring D to Ring I each independently represents a benzene ring which may have a substituent.
However, the substituents of ring D to ring I are bonded to each other to form a naphthalene ring together with these rings, or the naphthalene ring is bonded to ring D to I directly or through another group, The compound has two or more naphthalene rings in one molecule. ) The organic compound according to claim 1 or 2, wherein the compound has a partial structure represented by the following formula (IV).

(In formula (IV), the benzene ring may have a substituent.
However, the substituents of the benzene ring in the formula (IV) are bonded to each other to form a naphthalene ring together with these rings, or the naphthene ring in the formula (IV) directly or via another group , The compound has two or more naphthalene rings in one molecule. ) The organic compound according to any one of claims 1 to 3, wherein in the compound, the partial structure represented by the formula (I) is a partial structure represented by the following formula (IVa).

(In formula (IVa), the benzene ring and the carbazole ring may have a substituent.
However, the substituents of the benzene ring and the carbazole ring in the formula (IVa) are bonded to each other to form a naphthalene ring together with these rings, or directly to the benzene ring and the carbazole ring in the formula (IVa) or other When the naphthalene ring is bonded via a group, the compound has two or more naphthalene rings in one molecule. )   A charge transport material comprising the organic compound according to any one of claims 1 to 4.   An organic electroluminescent element composition comprising the organic compound according to any one of claims 1 to 4 and a solvent.   The composition for organic electroluminescent elements according to claim 6, wherein the solvent is an aromatic compound or an aliphatic ketone compound.   Furthermore, the composition for organic electroluminescent elements of Claim 6 or 7 containing a phosphorescence-emitting material.   It is an organic electroluminescent element which has a light emitting layer provided between an anode, a cathode, and these both electrodes on a board | substrate, Comprising: Using the composition for organic electroluminescent elements of any one of Claims 6-8. An organic electroluminescence device having a layer formed by a wet film formation method.   The organic electroluminescent device according to claim 9, wherein a layer formed by a wet film formation method using the composition for an organic electroluminescent device is a light emitting layer.   An organic EL display comprising the organic electroluminescent element according to claim 9.   An organic EL illumination comprising the organic electroluminescent element according to claim 9.

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