JP2007308557A - Composition for organic electroluminescent device and organic electroluminescent device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for organic electroluminescent elements whose organic layers are formed from low molecular materials by a wet film-forming method and have good light-emitting characteristics. <P>SOLUTION: The composition for forming the organic layers of organic electroluminescent elements comprising dopant materials, host materials and solvents is characterized in that the dopant materials and the host materials are non-polymerizable compounds, respectively, and the dopant materials and the host materials are compounds having 1 to 30C alkyl groups as partial structures, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composition for an organic electroluminescence device and the like. More specifically, the present invention relates to a composition for an organic electroluminescent element suitable for a wet film forming method.

  In recent years, an electroluminescent element (organic electroluminescent element) using an organic thin film has been developed. Materials for organic electroluminescent elements can be classified mainly into low molecular weight materials and high molecular weight materials (polymerization type organic compounds).

  In the case of using a low molecular weight material, for example, an organic electroluminescent element provided with a hole transport layer containing an aromatic diamine and a light emitting layer containing an aluminum complex of 8-hydroxyquinoline, or aluminum of 8-hydroxyquinoline An organic electroluminescent element containing a complex as a host material and a fluorescent dye for laser such as coumarin as a doping material has been developed. In addition, low molecular weight materials such as platinum complexes and iridium complexes are also used as materials for the light emitting layer.

  On the other hand, an organic electric field using a polymer material such as poly (p-phenylene vinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylene vinylene], poly (3-alkylthiophene), etc. Development of a light emitting element and an element in which a low molecular light emitting material and an electron transporting material are mixed with a polymer material such as polyvinyl carbazole are also underway.

  Focusing on the method of forming a thin film, until now, most of the low molecular materials were vacuum deposition methods, and the high molecular materials were wet film forming methods. The vacuum deposition method has advantages such as being able to form a high-quality film uniformly on the substrate, easy to obtain a device with excellent characteristics and easy lamination, and very little contamination from the manufacturing process. . Most of the organic electroluminescent devices currently in practical use are based on vacuum deposition using low molecular weight materials.

  On the other hand, a wet film-forming method using a polymer material can easily increase the area without requiring a vacuum process, and a single layer (coating liquid) can contain a plurality of materials having various functions. There are advantages, such as being. However, it is difficult to control the degree of polymerization and molecular weight distribution of polymer materials (polymerized organic compounds), deterioration due to terminal residues during continuous driving, and high purity of the polymer materials themselves are difficult. There may be a problem of including impurities. The present condition is that it has not reached the practical level other than the element using some polymer materials.

  As an attempt to solve the above problems, Patent Document 1 and Patent Document 2 describe that wet film formation is performed using a low-molecular fluorescent substance, a hole transport material, an electron transport material, and the like (non-polymerization type organic compound). A method for forming an organic layer by a method is described. Patent Documents 3 and 4 propose a phosphor material that uses a phosphorescent material instead of a fluorescent material.

Japanese Patent No. 3069139 Japanese Patent Laid-Open No. 11-238359 JP 2004-296185 A Japanese Patent Laying-Open No. 2005-078896

However, these elements are insufficient in terms of luminous efficiency and lifetime, and are not practical.
The present invention has been made in view of such circumstances. That is, the main object of the present invention is to provide a composition for an organic electroluminescent element that realizes an element having good light emission characteristics in an organic electroluminescent element in which an organic layer is formed by a wet film forming method using a low molecular material. It is to provide. Another object of the present invention is to provide an organic electroluminescent device having good light emission characteristics.

  As a result of intensive studies by the present inventors in view of the above object, in an organic electroluminescent device in which an organic layer to be a light emitting layer is formed by a wet film forming method using a low molecular material, The inventors have found that the compatibility between the dopant material and the host material in the composition greatly affects the light emission efficiency, the lifetime, and the like, and reached the present invention.

  Thus, according to the present invention, a composition for forming an organic layer of an organic electroluminescent device containing a dopant material, a host material, and a solvent, wherein the dopant material and the host material are each a non-polymerizable compound. A dopant material and a host material are each a compound having an alkyl group having 1 to 30 carbon atoms as a partial structure, and a composition for an organic electroluminescence device is provided.

Here, the alkyl group may have 2 to 20 carbon atoms.
The dopant material is a compound having an aromatic hydrocarbon ring, an aromatic heterocyclic ring, or a chalcogen atom, and the alkyl group is bonded to the aromatic hydrocarbon ring, the aromatic heterocyclic ring, or the chalcogen atom. Can be characterized.
Further, the host material is a compound having an aromatic hydrocarbon ring, aromatic heterocycle or chalcogen atom, and the alkyl group is bonded to the aromatic hydrocarbon ring, aromatic heterocycle or chalcogen atom. Can be characterized.
Still further, the dopant material can be characterized by being a phosphorescent luminescent dye, and the host material can be characterized by being a carbazole-based compound.

  On the other hand, the present invention is regarded as an organic electroluminescent device, and the organic electroluminescent device of the present invention is an organic electroluminescent device comprising an anode, a cathode, and an organic layer provided between both electrodes on a substrate. The organic layer is a layer formed using any one of the above-described compositions for organic electroluminescent elements.

That is, when both the dopant material and the host material do not have a substituent that dissolves each other, when an organic layer is formed from a composition containing both the materials by a coating method, each of the dopant material and the host material in the organic layer. Has a strong tendency to form clusters, and the dispersibility of the dopant material is considered to be poor (FIG. 2).
When the dopant material forms a cluster, the light emission from the dopant material is absorbed by another neighboring dopant material, and the recombination phenomenon of light emission, or nearby dopant materials interact with each other to form an exciplex. It is considered that the “exciplex light emission” phenomenon in which the light emission efficiency and the color purity deteriorate due to the formation of the light emission, and therefore, the light emission luminance, the lifetime, the light emission efficiency and the like tend to deteriorate. Moreover, such a tendency is considered to be more remarkable in the wet film forming method than in the vapor deposition film forming method.

However, by introducing a substituent common to both the dopant material and the host material, more specifically, a substituent having at least a partial structure of an alkyl group into the molecule, such an undesirable phenomenon can be reduced. It was considered. That is, if the substituent of the host material can interact with the substituent of the dopant material, it is considered that the dopant material is uniformly dispersed (FIG. 1).
The present inventor has improved the compatibility between the dopant material and the host material by using such a dopant material and the host material. And by forming a good fine dispersion state of the dopant material without forming a cluster in the dopant material, even in the case of adopting a wet film forming method, it was improved in terms of luminous efficiency, lifetime, luminance, etc. The formation of an organic electroluminescent element is realized.

  ADVANTAGE OF THE INVENTION According to this invention, the low molecular material type organic electroluminescent element which has a favorable light emission characteristic is provided by the wet film-forming method.

  The best mode for carrying out the present invention (hereinafter, an embodiment of the present invention) will be described in detail below. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. The drawings used are for explaining the present embodiment and do not represent the actual size.

(1) Composition for organic electroluminescent element In this Embodiment, the composition for organic electroluminescent elements contains a dopant material, host material, and a solvent.

(Common matters for dopant materials and host materials)
As the dopant material and the host material used in the present embodiment, any known material or new material can be used as long as the object of the present invention is not impaired.
In this embodiment, both the dopant material and the host material are non-polymerizable compounds. Here, the “non-polymerizable compound” refers to a compound other than a compound generally called a polymer (polymerizable compound). That is, it refers to a substance other than a substance composed of a high molecular weight polymer or a condensate molecule produced by repeating the same reaction or a similar reaction in a low molecular weight compound. That is, it is different from a high molecular weight organic compound produced by regularly or irregularly polymerizing a single or plural polymerizable monomers, oligomers or polymers by any method, and has a substantial molecular weight. It is a single compound, and its molecular structure can be uniquely and quantitatively defined by a chemical formula.

In this embodiment, both the dopant material and the host material are compounds having an alkyl group having 1 to 30 carbon atoms as a partial structure.
Here, “having an alkyl group as a partial structure” means that an alkyl group is included in any of the chemical structural formulas. Such an alkyl group may be an alkyl group that is directly bonded to the molecular skeleton serving as the base of the compound as a side chain, or an alkyl group that is bonded to the molecular skeleton serving as the parent of the compound via some connecting portion. (It may be included as a part of the substituent).
In addition, as a connection part, although it does not specifically limit, For example, the connection part by an ether bond, a thioether bond, an amide bond, an ester bond, a carbonyl bond, a phenylene group, an amino group etc. can be mentioned.

In addition, the “alkyl group” in the present embodiment includes a substituted or unsubstituted alkyl group.
Examples of the substituted alkyl group include those in which some or all of the hydrogen atoms are substituted with halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From the viewpoint of improving the stability of the compound because it is chemically inert, a fluorine atom-substituted product is particularly preferable.
Specific examples of such a substituted halogen atom (hereinafter sometimes abbreviated as “haloalkyl group”) include, for example, a perfluoroethyl group, a 1-perfluoropropyl group, a 2-perfluoropropyl group, A 1-perfluorobutyl group and a perfluorocyclohexyl group can be exemplified. From the viewpoint of the thermal stability of the compound, a perfluoroethyl group is particularly preferable.

The dopant material and the host material used in the present embodiment have a substituent that dissolves each other (hereinafter, may be abbreviated as “substituent S”). Although it does not specifically limit as such a substituent, Substituents as shown to following (i)-(viii) are mentioned.
In addition, these can be used individually by 1 type or can use 2 or more types together. Moreover, the substituent S which a dopant material and a host material each have may be the same, or may differ.

(I) an alkyl group having 1 to 30 carbon atoms (preferably 2 to 20, more preferably 2 to 12 and still more preferably 2 to 5).
Examples of such an alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and an eicosanyl group.
These are linear alkyl groups such as ethyl group, n-propyl group, n-butyl group and n-pentyl group; branched chain alkyl groups such as 2-propyl group, 2-butyl group and 2-pentyl group. Any of a group; a cyclic alkyl group such as a cyclopentyl group and a cyclohexyl group may be used.

(Ii) an alkyloxy group having 1 to 30 carbon atoms (preferably 2 to 20, more preferably 2 to 12 and still more preferably 2 to 5). Any alkyloxy group partially having the alkyl group shown in the above (i) can be used.
Examples of such an alkyloxy group include an ethoxy group, a 1-propoxy group, a 2-propoxy group, a 1-butoxy group, a 1-pentyloxy group, a 1-octyloxy group, a 1-eicosanyloxy group, and cyclohexyl. An oxy group is mentioned. Preferred are an ethoxy group and a 1-propoxy group, and most preferred is an ethoxy group.

(Iii) An alkylcarbonyl group having 2 to 31 carbon atoms (preferably 3 to 21, more preferably 3 to 13, and still more preferably 3 to 6). Any alkylcarbonyl group partially having the alkyl group shown in the above (i) can be used.
Examples of such an alkylcarbonyl group include an acetyl group, an ethylcarbonyl group, a propylcarbonyl group, and an octylcarbonyl group, and preferably an acetyl group.

(Iv) an alkyloxycarbonyl group having 2 to 31 carbon atoms (preferably 3 to 21, more preferably 3 to 13 and still more preferably 3 to 6). Any alkyloxycarbonyl group partially having the alkyl group shown in the above (i) can be used.
Examples of such an alkyloxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a pentyloxycarbonyl group, and an octyloxycarbonyl group, and preferably an ethoxycarbonyl group.

(V) an arylalkyl group having 8 to 40 (preferably 8 to 12) carbon atoms. Any arylalkyl group partially having the alkyl group shown in the above (i) can be used.
Examples of such an arylalkyl group include a 2-phenylethyl group, a 1-phenylethyl group, an 8-phenyl-1-octyl group, and a 4-phenylcyclohexyl group, and preferably a 2-phenylethyl group. .

(Vi) an alkenyl group having 3 to 30 (preferably 3 to 12) carbon atoms. Any alkenyl group partially having an alkyl group shown in (i) above can be used.
Examples of such an alkenyl group include a 1-propen-1-yl group and a 1-buten-2-yl group, and a 1-propen-1-yl group is preferable.

(Vii) an N, N-dialkylamino group having 2 to 30 (preferably 2 to 12) carbon atoms. Any of the N, N-dialkylamino groups partially having an alkyl group shown in (i) above can be used.
Examples of such N, N-dialkylamino group include N-ethyl-N-methylamino group, N, N-diethylamino group, N, N-dipropylamino group, and N-propyl-N-methylamino group. N-octyl-N-methylamino group, preferably N, N-diethylamino group.

(Viii) an N-alkyl-N-arylamino group having 8 to 40 (preferably 8 to 20) carbon atoms. Any N-alkyl-N-arylamino group partially having the alkyl group shown in the above (i) can be used.
Examples of such an N-alkyl-N-arylamino group include an N-ethyl-N-phenylamino group and an N-octyl-N-phenylamino group, preferably an N-ethyl N-phenylamino group. It is.

Among these, from the viewpoint of stability of the compound, an alkyl group and an alkyloxy group are preferable, and an alkyl group is most preferable.
In addition, when the alkyl chain is branched or cyclic, the branched carbon is easily subjected to electrical oxidation or reduction, so that the preferable alkyl difference is linear.

The alkyl group in this embodiment is preferably an alkyl group having a long chain length. That is, an alkyl group such as an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and an eicosanyl group is preferable to a methyl group. This is because the use of an alkyl group having a long chain length facilitates the interaction between the host material and the dopant material, and as a result, the dopant material is more easily dispersed.
On the other hand, when the chain length of the alkyl group is short, it is considered to be behind the substituents around the alkyl group, and the alkyl group is unlikely to interact with other molecules. However, when the chain length of the alkyl group is excessively long, the glass transition point of the material itself is likely to be lowered and the heat resistance may be poor. From such a viewpoint, the alkyl group suitably used in the present embodiment is an ethyl group, a propyl group, a butyl group, or a pentyl group, particularly preferably an ethyl group, a propyl group, or a butyl group, Most preferred are ethyl group and propyl group.

In the molecular structure of the host material or dopant material, the alkyl group may be substituted with any part of the molecular structure, but from the viewpoint of molecular stability, preferably a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring. , A pyridine ring, a furan ring, an aromatic hydrocarbon ring such as a carbazole ring (in particular, a benzene ring or a pyridine ring is more preferable, and a benzene ring is particularly preferable) or an aromatic heterocyclic ring. preferable.
Furthermore, when the host material or dopant material is a compound having a chalcogen atom such as an oxygen atom, a sulfur atom, or a selenium atom, an alkyl group is bonded to such a chalcogen atom from the same viewpoint as described above. Is preferred.

  In the present embodiment, the number of substituents S is not particularly limited, but the number of substituents in one molecule is preferably 1 to 20, more preferably 1 to 10, and most preferably 2 to 8. When the number of the substituents S exceeds 20, the glass transition temperature of the compound decreases or becomes oily at room temperature, which is not preferable.

In this embodiment, both the dopant material and the host material have an alkyl group having 1 to 30 carbon atoms as a partial structure. As described above, when forming an organic layer of an organic electroluminescent element using a low molecular material, a vapor deposition method has been generally employed. Here, when a substituent is introduced and the molecular weight of the compound increases, the compound tends to hardly evaporate. That is, since vapor deposition tends to be more difficult, those skilled in the art have never intentionally introduced an alkyl group (particularly, a long-chain alkyl group) as a substituent into a conventionally known low-molecular material.
In addition, as a method for adjusting the emission characteristics of the dopant material or the host material, a so-called chromophore is introduced, or a method of changing the bond angle of a single bond in a compound by introducing some substituent, Methods of changing are known. However, alkyl groups generally do not belong to chromophores. Moreover, small substituents are sufficient to change the bond angle for a single bond. Also from these facts, those skilled in the art did not intentionally introduce an alkyl group (particularly, a long-chain alkyl group) as a substituent into a conventionally known low molecular weight material.
In the present embodiment, the compatibility between the dopant material and the host material affects the light emission characteristics of the organic electroluminescent element, and the above-described tendency has been found to increase in the wet film forming method. Such an alkyl group is introduced into both the dopant material and the host material.

  In the present embodiment, the molecular weight of the compound used as the host material or dopant material is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, usually 100 or more, preferably 200 or more, more preferably 300 or more, still more preferably 400 or more, particularly preferably 500 or more. When the molecular weight is less than 100, the heat resistance is remarkably reduced, gas is generated, the film quality is deteriorated when the film is formed, or the morphology of the organic electroluminescent element is changed due to migration or the like. This is not preferable. If the molecular weight exceeds 10,000, it may be difficult to purify the organic compound, and it is likely that time is required for dissolution in the solvent, which is not preferable.

  In this embodiment, the glass transition point of the compound used as the host material or dopant material is usually 70 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, more preferably 130 ° C. or higher, most preferably Is 150 ° C. or higher. If the glass transition point is too low, the heat resistance of the organic electroluminescent device may be lowered, and the driving life may be shortened.

Hereinafter, each of the dopant material and the host material will be described in detail.
(Dopant material)
Examples of the dopant material in this embodiment can include a fluorescent material and a phosphorescent material. Among these, phosphorescent materials are preferably used from the viewpoint of internal quantum efficiency.
Among fluorescent materials, examples of fluorescent dyes that give blue light emission 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.

The phosphorescent material preferably includes, for example, an organometallic complex containing a metal selected from Group 7 to Group 11 (periodic table: IUPAC Periodic Table of the Elements, 2004).
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 (I).

（式（Ｉ）中、Ｍは金属を表し、ｑは金属Ｍの価数を表す。Ｇ及びＸは二座配位子を表し、Ｙは単座配位子を表す。Ｚは対アニオンを表し、ｍ，ｎは錯体及び対アニオンの価数を表す。添字ｉは０、１又は２、ｊは０、２又は４を表し、添字ｒ、ｐは自然数を表し、ｒ×ｍ＝ｐ×ｎである。）

(In formula (I), M represents a metal, q represents a valence of the metal M. G and X represent a bidentate ligand, Y represents a monodentate ligand, and Z represents a counter anion.) , M, n represent valences of the complex and counter anion, subscript i represents 0, 1 or 2, j represents 0, 2 or 4, subscripts r and p represent natural numbers, and r × m = p × n .)

Hereinafter, the compound represented by the formula (I) will be described in detail.
In the formula (I), 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. Moreover, the bidentate ligands G and X in the formula (I) each represent a ligand having the following partial structure. Here, the following “ligand having a partial structure” means that the chemical structural formula of the ligand includes a structure that substantially overlaps the following structural formula. In addition, regarding the abbreviations appropriately described in the structural formulas exemplified below, Ph represents a phenyl group, Me represents a methyl group, Et represents an ethyl group, and Bu represents a butyl group. The same applies hereinafter.

The partial structure of the bidentate ligand X is particularly preferably the following partial structure from the viewpoint of the stability of the complex.

In the partial structures of G and X, the ring Q1 represents an aromatic hydrocarbon group or an aromatic heterocyclic group, and these may have a substituent S. Ring Q2 represents a nitrogen-containing aromatic heterocyclic group, and these may have a substituent S. In addition, these rings Q1 and Q2 may have a substituent other than the substituent S. In addition, it is preferable that at least one substituent S is substituted on either ring Q1 or ring Q2.
Preferred substituents for the rings Q1 and Q2 other than the substituent S include a halogen atom such as a fluorine atom or an alkyl group such as a methyl group; an alkenyl group such as a vinyl group; an alkoxycarbonyl group such as a methoxycarbonyl group; a methoxy group Alkoxy groups such as phenoxy groups, benzyloxy groups, etc .; Dialkylamino groups such as dimethylamino groups; Diarylamino groups such as diphenylamino groups; Carbazolyl groups; Acyl groups such as acetyl groups; Trifluoromethyl groups, etc. Among the aromatic hydrocarbon groups such as phenyl group, naphthyl group and phenanthyl group, those different from the substituent S can be mentioned.

In addition, the monodentate ligand Y in the formula (I) is any partial structure of (CH ₃ ) ₃ C (CN), CN ⁻ , P (n—C ₄ H ₉ ) ₃ , Cl ⁻ , SCN ^—. The ligand which has is shown.

Further, the counter anion Z in the formula (I) is a halide ion, CF ₃ SO ₂ ⁻ , HCO ₃ ⁻ , HSO ₃ ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , PO ₄ ³⁻ , HPO ₄ ²⁻ , One of BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ and SbCl ₅ ⁻ is shown.

  More preferable examples of the compound represented by the formula (I) include compounds represented by the following formulas (Ia) to (Ic).

（式（Ｉａ）中、Ｍ^ａはＭと同様の金属を表し、ｑ^ａは金属Ｍ^ａの価数を表す。環Ｑ１は置換基を有していても良い芳香族炭化水素基又は芳香族複素環基を表し、環Ｑ２は置換基を有していても良い含窒素芳香族複素環基を表す。）

(In the formula (Ia), M ^a represents the same metal as M, q ^a represents the valence of the metal M ^a. Ring Q1 is aromatic optionally substituted hydrocarbon group or an aromatic Represents a heterocyclic group, and ring Q2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.

（式（Ｉｂ）中、Ｍ^ｂはＭと同様の金属を表し、ｑ^ｂは金属Ｍ^ｂの価数を表す。環Ｑ１は置換基を有していても良い芳香族炭化水素基又は芳香族複素環基を表し、環Ｑ２は置換基を有していても良い含窒素芳香族複素環基を表す。Ｒ^３１，Ｒ^３２は置換基を有していても良いアルキル基、芳香族基を表す。）

(In the formula (Ib), M ^b represents the same metal as M, q ^b represents the valence of the metal M ^b. Ring Q1 is aromatic optionally substituted hydrocarbon group or an aromatic Represents a heterocyclic group, ring Q2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent, and R ³¹ and R ³² represent an alkyl group or an aromatic group which may have a substituent. To express.)

（式（Ｉｃ）中、Ｍ^ｃはＭと同様の金属を表し、ｑ^ｃは金属Ｍ^ｃの価数を表す。ｊは０、１又は２を表す。環Ｑ１及び環Ｑ１’は、それぞれ独立に、置換基を有していても良い芳香族炭化水素基又は芳香族複素環基を表す。環Ｑ２及び環Ｑ２’は、それぞれ独立に、置換基を有していても良い含窒素芳香族複素環基を表す。）

(In the formula (Ic), ^{M c} denotes the same metal as M, ^{q c} is .j representing the valence of the metal ^{M c} represents 0, 1 or 2. Ring Q1 and Ring Q1 'are each independently Represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and ring Q2 and ring Q2 ′ are each independently a nitrogen-containing aromatic which may have a substituent. Represents a heterocyclic group.)

In the above formulas (Ia), (Ib) and (Ic), the ring Q1 and the ring Q1 ′ are preferably, for example, a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a thienyl group, a furyl group, a benzothienyl group, A benzofuryl group, a pyridyl group, a quinolyl group, an isoquinolyl group, a carbazolyl group, and the like can be given.
The ring Q2 and ring Q2 ′ are preferably, for example, pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, benzimidazole group, quinolyl group, isoquinolyl group, quinoxalyl group, phenane. A tridyl group etc. are mentioned.

In the formula (Ib), R ³¹ and R ³² represent an alkyl group or an aromatic ring group which may have a substituent. More specifically, examples of the alkyl group include a methyl group, an ethyl group, Examples include propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group and the like. A methyl group and an ethyl group are preferred.

  Examples of the aromatic ring group include a phenyl group, a naphthyl group, an anthranyl group, a phenanthrenyl group, a thienyl group, a furyl group, a pyridyl group, a pyrazolyl group, and a carbazolyl group, preferably a phenyl group, a pyridyl group, and a carbazolyl group. Particularly preferred are a phenyl group and a pyridyl group, and particularly preferred is a phenyl group.

Examples of the substituent that R ³¹ and R ³² may have include a halogen atom, and more specifically, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From an active point, a chlorine atom and a fluorine atom are preferable, and a fluorine atom is particularly preferable.

  Examples of the substituent other than the substituent S that the compound represented by the formula (Ia), (Ib), or (Ic) may have include a halogen atom such as a fluorine atom or an alkyl group such as a methyl group; Alkenyl groups such as vinyl groups; alkoxycarbonyl groups such as methoxycarbonyl groups; alkoxy groups such as methoxy groups; aryloxy groups such as phenoxy groups and benzyloxy groups; dialkylamino groups such as dimethylamino groups; diaryls such as diphenylamino groups Among the amino groups; carbazolyl groups; acyl groups such as acetyl groups; haloalkyl groups such as trifluoromethyl groups;

These substituents may be connected to each other to form a ring. As a specific example, the substituent of ring Q1 and the substituent of ring Q2 are bonded, or the substituent of ring Q1 ′ and the substituent of ring Q2 ′ are bonded to form one condensed group. A ring may be formed. Examples of such a condensed ring include a 7,8-benzoquinoline group.
Among them, as a substituent of ring Q1, ring Q1 ′, ring Q2 and ring Q2 ′, an alkyl group, alkoxy group, aromatic hydrocarbon group, cyano group, halogen atom, haloalkyl group, diarylamino group, carbazolyl group are more preferable. Is mentioned.

In addition, examples of M ^a , M ^b , and M ^c in the formulas (Ia), (Ib), and (Ic) include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, or gold, preferably palladium, Examples include osmium, iridium, platinum, and gold, particularly preferably iridium, osmium, and platinum, and most preferably iridium.

  Specific examples of the organometallic complex represented by the above formula (I), (Ia), (Ib) or (Ic) are shown below, but are not limited to the following compounds. These may be used alone or in combination of two or more.

  Further, among the organometallic complexes represented by the above formulas (I), (Ia), (Ib), and (Ic), from the viewpoint of the stability of the complex, in particular, 2 as ligand G and / or G ′. -Arylpyridine-based ligands, that is, compounds having 2-arylpyridine, those having an arbitrary substituent bonded thereto, and those obtained by condensing an arbitrary group thereto are preferable.

(Host material)
Examples of the host material in the present embodiment include carbazole compounds (including triarylamine compounds); phenylanthracene derivatives such as a starburst compound of a condensed ring arylene; a condensed triazole compound, and a propeller arylene compound. Monotriarylamine compounds, arylbenzidine compounds, triarylboron compounds, indole compounds, indolizine compounds, pyrene compounds, dibenzoxazole (or dibenzothiazole) compounds, bipyridyl compounds, pyridine compounds, A cyclic imidazole compound, an azepine compound; and the like.

  Among these, carbazole compounds (including triarylamine compounds), condensed arylene starburst compounds, condensed imidazole compounds, from the viewpoint of excellent emission characteristics when using an organic electroluminescent device, Propeller type arylene compounds, monotriarylamine type compounds, indole compounds, indolizine compounds, bipyridyl compounds, pyridine compounds and the like are preferable.

  Furthermore, from the viewpoint of driving life when using an organic electroluminescent device, a carbazole compound, a bipyridyl compound, and a pyridine compound are more preferable, a mixture of a carbazole compound and a bipyridyl compound, or a carbazole compound and It is most preferable to use a mixture of pyridine compounds.

  It is also preferable to employ a compound having both a carbazolyl group and a pyridyl group. For the purpose of improving the solubility in a solvent, it is also important to reduce the symmetry and rigidity of the molecule or to introduce a lipophilic substituent such as an alkyl group. Specific examples of particularly preferable compounds as the host material are shown below. In addition, these are independent or can use 2 or more types together.

  Note that the compound used as the host material preferably has a band gap of usually 3.0 V or higher, preferably 3.2 V or higher, more preferably 3.5 V or higher. Blue fluorescent light-emitting materials or phosphorescent light-emitting materials, especially green to blue light-emitting materials have a large band gap. When an organic electroluminescent element is produced using this phosphorescent light-emitting material, the host material surrounding the phosphorescent light-emitting material is: This is because, in general, it is preferable that the phosphorescent material has a bandgap that is equal to or larger than that of the phosphorescent material in terms of luminous efficiency and life as an organic electroluminescent element.

(solvent)
Examples of the solvent used in the present embodiment include aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, and trichlorobenzene; 1,2- Aromatic ethers such as dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole; phenyl acetate , Aromatic esters such as phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate and n-butyl benzoate; ketones having an alicyclic ring such as cyclohexanone and cyclooctanone; fats such as methyl ethyl ketone and dibutyl ketone Ketone; Alcohol having an alicyclic ring such as methyl ethyl ketone, cyclohexanol and cyclooctanol; Aliphatic alcohol such as butanol and hexanol; Fat such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA) Aliphatic ethers; 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. These can be used alone or in combination of two or more.

Here, many materials (for example, a cathode material) that are remarkably deteriorated by moisture are used in the organic electroluminescent element. The presence of moisture in the composition for organic electroluminescence devices is not preferable because moisture may remain in the dried film and may deteriorate the characteristics of the device. The solvent used in this embodiment is preferably a solvent having low water solubility.
Examples of a method for reducing the amount of water in the composition include a method of performing nitrogen gas sealing, a method of using a desiccant, a method of dehydrating a solvent in advance, a method of using a solvent having low water solubility, and the like. Is mentioned. In particular, when a solvent having low water solubility is used, the solution film can prevent the phenomenon of whitening due to absorption of moisture in the air during the wet film-forming process.

  As the water solubility of the solvent, the solubility of water at 25 ° C. is usually 1% by weight or less, preferably 0.1% by weight or less. The proportion of such a solvent in the charge transport material composition is usually 10% by weight or more.

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

  A solvent that satisfies the conditions for such a solvent, that is, the solubility of the solute, the evaporation rate, and the solubility of water may be used alone, but if a solvent that satisfies all the conditions cannot be selected, two or more types of solvents may be used. It is also possible to use a mixture of solvents.

(Other compounds)
In addition to the various materials described above, the composition for organic electroluminescent elements in the present embodiment may contain various dispersants and other solvents as necessary. 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.
Further, when two or more layers are laminated by a wet film forming method, in order to prevent these layers from being compatible with each other, a photo-curing resin or a thermosetting resin is used for the purpose of curing and insolubilizing after the film formation. Can also be contained.

(Preferred embodiment as a composition)
In the composition for organic electroluminescent elements in the present embodiment, the blending concentration of solid materials such as a dopant material and a host material is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.8%. 1% by weight or more, more preferably 0.5% by weight or more, most preferably 1% by weight or more, usually 80% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less, still more preferably 30%. % By weight or less, most preferably 20% by weight or less. If this concentration is below the lower limit, it may be difficult to form a thick film when forming a thin film. On the other hand, if the upper limit is exceeded, it may be difficult to form a thin film.

  Moreover, in the composition for organic electroluminescent elements in this Embodiment, as a compounding ratio of dopant material and host material, it is 0.1 / 99.9-50 / as dopant material / host material (weight ratio) normally. 50, preferably 0.5 / 99.5 to 40/60, more preferably 1/99 to 30/70, and most preferably 2/98 to 20/80. If this ratio is outside the above range, the luminous efficiency may be significantly reduced.

(Method for preparing composition for organic electroluminescent device)
The composition for an organic electroluminescent device in the present embodiment dissolves a solute composed of a dopant material, a host material, and various additives such as a leveling agent and an antifoaming agent that can be added as necessary in an appropriate solvent. It is prepared by. In order to shorten the time required for the dissolution step and to keep the solute concentration in the composition uniform, the solute is usually dissolved while stirring the liquid. The dissolution step may be performed at room temperature, but when the dissolution rate is slow, it can be heated and dissolved. After completion of the dissolution step, a filtration step such as filtering may be performed as necessary.

(2) Properties, physical properties, etc. (moisture concentration) of the composition for organic electroluminescent elements
When the organic electroluminescence device is produced by forming a layer by a wet film forming method using the composition for organic electroluminescence device in the present embodiment, the organic electroluminescence device is formed when water is present in the composition for organic electroluminescence device to be used. Water is mixed into the film, and the uniformity of the film is impaired. Therefore, it is preferable that the water content in the composition for organic electroluminescent elements is 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 charge transport material composition, moisture remains in the dried film. There is a possibility of deteriorating the characteristics of the element, which is not preferable.
The amount of water contained in the composition for organic electroluminescent elements is usually 1% by weight or less, preferably 0.1% by weight or less, more preferably 0.01% by weight or less.
In the present embodiment, the method described in Japanese Industrial Standard “Method for Measuring Water of Chemical Products” (JIS K0068: 2001) is preferable as the method for measuring the moisture concentration. For example, it can be analyzed by the Karl Fischer reagent method (JIS K0211-1348) or the like.

(Uniformity)
As an aspect of the composition for organic electroluminescent elements in the present embodiment, it is a uniform liquid 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. It is preferable. 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.

(viscosity)
As for the viscosity of the composition for organic electroluminescent elements in the present embodiment, in the case of extremely low viscosity, for example, uneven coating surface due to excessive liquid film flow in the film forming process, nozzle discharge failure in ink jet film forming, etc. It tends to happen. On the other hand, when the viscosity is extremely high, nozzle clogging or the like in ink-jet film formation tends to occur. Therefore, the viscosity at 25 ° C. of the composition in the present embodiment 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. · S or less, more preferably 50 mPa · s or less.

(surface tension)
In addition, when the surface tension of the composition for organic electroluminescent elements in the present embodiment is high, there is a problem that the wettability of the liquid for film formation with respect to the substrate is low, and the leveling property of the liquid film is poor, and the production at the time of drying is not good. Problems such as film surface disturbances may occur. For this reason, the surface tension at 20 ° C. is usually less than 50 mN / m, preferably less than 40 mN / m.

(Vapor pressure)
Furthermore, when the vapor pressure of the composition for organic electroluminescent elements in the present embodiment is high, problems such as changes in solute concentration due to evaporation of the solvent are likely to occur. For this reason, the vapor pressure at 25 ° C. is usually 50 mmHg or less, preferably 10 mmHg or less, more preferably 1 mmHg or less.

(Preservation method)
The composition for organic electroluminescent elements in the present embodiment is preferably filled in a container capable of preventing the transmission of ultraviolet rays, such as a brown glass bottle, and sealed and stored. The storage temperature is usually −30 ° C. or higher, preferably 0 ° C. or higher, and usually 35 ° C. or lower, preferably 25 ° C. or lower.

(3) Organic electroluminescent element The organic electroluminescent element of this Embodiment has an anode, a cathode, and the light emitting layer provided between these both electrodes on a board | substrate, The above-mentioned composition for organic electroluminescent elements The light emitting layer is formed of an object.

(Constitution)
3 to 9 are schematic cross-sectional views showing structural examples suitable for the organic electroluminescent element of the present embodiment. For example, the organic electroluminescent element shown in FIG. 3 is formed by laminating an anode 2, a hole injection layer 3, a light emitting layer 4, an electron injection layer 5, and a cathode 6 in this order on a substrate 1.

(Substrate 1)
The substrate 1 serves as a support for the organic electroluminescent element, and is formed using a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet. 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.

(Anode 2)
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).
The anode 2 is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as oxide of indium and / or tin, metal halide such as copper iodide, carbon black, or poly It is formed of conductive polymers such as (3-methylthiophene), polypyrrole, and polyaniline.

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. Furthermore, 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).
In FIG. 3, the anode 2 has a single-layer structure, but it may be a laminated structure made of a plurality of materials as desired.

The thickness of the anode 2 is appropriately selected 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. It is also possible to further stack different conductive materials on the anode 2.
For the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve the hole injection property, the anode surface is treated with ultraviolet (UV) / ozone, or with oxygen plasma or argon plasma. It is preferable to do.

(Hole injection layer 3)
Since the hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 4, the hole injection layer 3 preferably contains a hole transporting compound.
The hole injection layer 3 further preferably contains a hole transporting compound and an electron accepting compound. Furthermore, the hole injection layer 3 preferably contains a cation radical compound, and particularly preferably contains a cation radical compound and a hole transporting compound.

The hole injection layer 3 may contain a binder resin that does not easily act as a charge trap or a coating property improving agent, if necessary.
The hole injection layer 3 may be formed by depositing only the electron-accepting compound on the anode 2 by a wet film-forming method, and directly applying and laminating the charge transport material composition thereon. In this case, a part of the charge transport material composition interacts with the electron-accepting compound, so that a layer excellent in hole injecting property is formed.

(Hole transporting compound)
As the hole transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable.
Examples of the hole transporting compound include aromatic amine compounds, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, and the like. Of these, aromatic amine compounds are preferred from the viewpoints of amorphousness and visible light transmittance.

Of the aromatic amine compounds, 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 kind of the aromatic tertiary amine compound is not particularly limited, but a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (polymerized hydrocarbon compound in which repeating units are linked) is more preferable from the viewpoint of the surface smoothing effect.

  And as a preferable example of an aromatic tertiary amine high molecular compound, the high molecular compound which has a repeating unit represented by the following general formula (II) is mentioned.

（一般式（ＩＩ）中、Ａｒ^２１，Ａｒ^２２は各々独立して、置換基を有していても良い芳香族炭化水素基、または置換基を有していても良い芳香族複素環基を表す。Ａｒ^２３〜Ａｒ^２５は、各々独立して、置換基を有していても良い２価の芳香族炭化水素基、または置換基を有していても良い２価の芳香族複素環基を表す。Ｙは、下記の連結基群の中から選ばれる連結基を表す。また、Ａｒ^２１〜Ａｒ^２５のうち、同一のＮ原子に結合する二つの基は互いに結合して環を形成しても良い。）

(In the general formula (II), each of Ar ²¹ and Ar ²² independently represents an aromatic hydrocarbon group which may have a substituent, or an aromatic heterocyclic group which may have a substituent. Ar ^{23 to} Ar ²⁵ each independently represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. Y represents a linking group selected from the following group of linking groups, and among Ar ^{21 to} Ar ²⁵ , two groups bonded to the same N atom are bonded to each other to form a ring. May be.)

（上記各式中、Ａｒ^３１〜Ａｒ^４１は、各々独立して、置換基を有していても良い芳香族炭化水素環、または置換基を有していても良い芳香族複素環由来の１価または２価の基を表す。Ｒ^５１およびＲ^５２は、各々独立して、水素原子または任意の置換基を表す。）

(In the above formulas, Ar ^{31 to} Ar ⁴¹ are each independently an aromatic hydrocarbon ring which may have a substituent or an aromatic heterocyclic ring which may have a substituent. And R ⁵¹ and R ⁵² each independently represents a hydrogen atom or an arbitrary substituent.)

As Ar ^{21 to} Ar ²⁵ and Ar ^{31 to} Ar ⁴¹ , any monovalent or divalent group derived from any aromatic hydrocarbon ring or aromatic heterocyclic ring is applicable. These may be the same or different from each other. Moreover, you may have arbitrary substituents.

The group derived from the aromatic hydrocarbon ring and / or aromatic heterocycle of Ar ^{21 to} Ar ⁴¹ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less.

Ar ²¹ and Ar ²² are preferably monovalent groups derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, or a pyridine ring from the viewpoint of the solubility, heat resistance, and hole injection / transport properties of the polymer compound. More preferred are a phenyl group and a naphthyl group.
Ar ^{23 to} Ar ²⁵ are preferably divalent groups derived from a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring from the viewpoint of heat resistance and hole injection / transport properties including redox potential. A group, a biphenylene group, and a naphthylene group are more preferable.

  Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the general formula (II) include those described in WO2005 / 089024.

  The hole transporting compound used as the material for the hole injection layer may contain any one of these compounds alone, or may contain two or more. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two other hole transporting compounds are used. It is preferable to use the above together.

(Electron-accepting compound)
As the electron-accepting compound, a compound having an oxidizing power and an ability to accept one electron from the hole-transporting compound described above is preferable. Specifically, a compound with an electron affinity of 4 eV or more is preferable, and a compound with a compound of 5 eV or more is more preferable.

  Examples of the electron-accepting compound include onium salts substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, iron (III) chloride (Japanese Patent Laid-Open No. 11-251067). , Inorganic compounds having high valence such as ammonium peroxodisulfate, cyano compounds such as tetracyanoethylene, aromatic boron compounds such as tris (pentafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365), fullerene derivatives, iodine and the like. .

Of the above compounds, onium salts substituted with organic groups and high valent inorganic compounds are preferred because of their strong oxidizing power, and organic groups are substituted because they are soluble in various solvents and applicable to wet coating. Preferred are onium salts, cyano compounds, and aromatic boron compounds.
Specific examples of the onium salt substituted with an organic group, a cyano compound, and an aromatic boron compound suitable as an electron-accepting compound include those described in WO2005 / 089024, and preferred examples thereof are also the same. For example, although the compound (A-2) represented by the following structural formula is mentioned, it is not limited to them at all.

(Cation radical compound)
As the cation radical compound, an ionic compound composed of a cation radical which is a chemical species obtained by removing one electron from a hole transporting compound and a counter anion is preferable. However, when the cation radical is derived from a hole transporting polymer compound, the cation radical has a structure in which one electron is removed from the repeating unit of the polymer compound.
The cation radical is preferably a chemical species obtained by removing one electron from the compound described above as the hole transporting compound. A chemical species obtained by removing one electron from a compound preferable as a hole transporting compound is public in view of amorphousness, visible light transmittance, heat resistance, solubility, and the like.

  Here, the cation radical compound can be generated by mixing the hole transporting compound and the electron accepting compound. That is, by mixing the hole transporting compound and the electron accepting compound, electron transfer occurs from the hole transporting compound to the electron accepting compound, and the cation radical and the counter anion of the hole transporting compound are included. A cation ion compound is formed.

  Cation radical compounds derived from polymer compounds such as PEDOT / PSS (Adv. Mater., 2000, 12, 481) and emeraldine hydrochloride (J. Phys. Chem., 1990, 94, 7716) It is also produced by oxidative polymerization (dehydrogenation polymerization). The oxidative polymerization referred to here is a method in which a monomer is chemically or electrochemically oxidized using peroxodisulfate or the like in an acidic solution. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is polymerized by oxidation, and a cation radical that is removed from the polymer repeating unit by using an anion derived from an acidic solution as a counter anion is removed. Generate.

The hole injection layer 3 is formed on the anode 2 by, for example, a wet film forming method or a vacuum deposition method.
In the case of layer formation by the wet film forming method, one or two or more predetermined amounts of each of the aforementioned materials (hole transporting compound, electron accepting compound, cation radical compound) act as a charge trap if necessary. First, a coating solution is prepared by dissolving it in a solvent together with a difficult binder resin and coating property improver. Subsequently, the positive hole injection layer 3 can be formed by applying on the anode by a wet film forming method such as spin coating, spray coating, dip coating, die coating, flexographic printing, screen printing, and inkjet method, and drying.

  As the solvent used for the layer formation by the wet film forming method, any solvent can be used as long as it can dissolve the above-mentioned materials (hole transporting compound, electron accepting compound, cation radical compound). Is not particularly limited. In addition, the material used for the hole injection layer (a hole transporting compound, an electron accepting compound, a cation radical compound) may not contain a deactivating substance or a substance that generates a deactivating substance. preferable. An ether solvent or an ester solvent is preferable.

  The concentration of the solvent in the coating solution is usually 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more. Moreover, as an upper limit, it is 99.999 weight% or less normally, Preferably it is 99.99 weight% or less, More preferably, it is 99.9 weight% or less. In addition, when using 2 or more types of solvents in mixture, the total of these solvents should just satisfy this range.

In the case of layer formation by vacuum deposition, first, one or more of the above-mentioned materials (hole transporting compound, electron accepting compound, cation radical compound) are placed in a crucible placed in a vacuum vessel. Put (into each crucible when two or more materials are used), and then evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump. After that, the crucible is heated (each crucible is heated when two or more materials are used), and the amount of evaporation is controlled and evaporated (when two or more materials are used, the amount of evaporation is controlled independently). Evaporation) and a hole injection layer can be formed on the anode of the substrate placed facing the crucible. In addition, when using 2 or more types of materials, they can also be put into a crucible, can be heated and evaporated, and can be used for hole injection layer formation.

  The film thickness of the hole injection layer 3 thus formed is usually in the range of 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. The hole injection layer 3 may be omitted as shown in FIG.

(Light emitting layer 4)
A light emitting layer 4 is usually provided on the hole injection layer 3. The light emitting layer 4 is a layer formed by using the composition for organic electroluminescent elements of the present embodiment, and holes injected from the anode 2 through the hole injection layer 3 between electrodes to which an electric field is applied. And a layer that is excited by recombination with electrons injected from the cathode 6 through the electron injection layer 5 and serves as a main light emitting source.

  In general, in an organic electroluminescent device, when compared with the same material, the thinner the film thickness between the electrodes, the larger the effective electric field and the larger the injected current, so the driving voltage decreases. Therefore, it is preferable that the total film thickness between the electrodes is thin, but if it is too thin, a short circuit occurs due to a protrusion caused by an electrode such as ITO. Therefore, a certain film thickness is required.

  In the present embodiment, when the organic layer such as the hole injection layer 3 or the electron injection layer 5 described later is provided in addition to the light emitting layer 4, the light emitting layer 4 and other organic materials such as the hole injection layer 3 and the electron injection layer 5 are used. The total film thickness combined with the layers is usually 30 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. On the other hand, the upper limit is 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 and the electron injection layer 5 other than the light emitting layer 4 is high, the amount of charge injected into the light emitting layer 4 increases. Therefore, for example, by increasing the film thickness of the hole injection layer 3 and decreasing the film thickness of the light emitting layer 4, it is possible to reduce the drive voltage while maintaining a certain film thickness as the total film thickness.

  The film 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 organic electroluminescent element of the present embodiment 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, and usually 500 nm or less. Preferably, it is 300 nm or less.

(Electron injection layer 5)
The electron injection layer 5 plays a role of efficiently injecting 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. Specifically, for example, 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.

Further, at the interface between the cathode 6 and the light emitting layer 4 or at the interface between the cathode 6 and the electron transport layer 7 described later, an ultrathin insulating film (0... LiF, MgF ₂ , Li ₂ O, Cs ₂ CO _3, etc.). 1-5 nm) is also an effective method for improving the efficiency of the device (Appl. Phys. Lett., 70, 152, 1997; JP-A-10-74586; IEEE Etran. Electron. Devices, 44, 1245, 1997; SID 04 Digest, 154).

  Furthermore, an alkali metal such as sodium, potassium, cesium, lithium, or rubidium is added to an organic electron transport material typified by a nitrogen-containing heterocyclic compound such as bathophenanthroline described later or a metal complex such as an aluminum complex of 8-hydroxyquinoline. The method of doping (described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.) also provides a viewpoint of achieving both improved electron injection / transport properties and excellent film quality. To preferred. The thickness of such a dope material 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 can be formed by being laminated 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 a metal boat installed in the vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with an appropriate vacuum pump. The crucible or metal boat can then be heated and evaporated 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 by an appropriate vacuum pump. Each crucible and dispenser can then be heated and evaporated simultaneously 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.

(Cathode 6)
The cathode 6 plays a role of injecting electrons into a layer (such as the electron injection layer 5 or the light emitting layer 4) on the light emitting layer side. The material used for the anode 2 can be used for forming the cathode 6. In order to perform electron injection efficiently, it is preferable to use a metal having a low work function, and an appropriate metal such as tin, magnesium, indium, calcium, aluminum, silver, or an alloy thereof is used. Specific examples of the material forming the low work function alloy electrode include a magnesium-silver alloy, a magnesium-indium alloy, and an 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 (increasing the stability of the device), a metal layer having a high work function and stable to the atmosphere can be further laminated on the cathode 6. Examples of metals suitable for this purpose include metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum.

(Other component layers)
As described above, the element having the layer configuration shown in FIG. 3 has been mainly described. However, the performance between the anode 2 and the cathode 6 and the light emitting layer 4 in the organic electroluminescent element of the present embodiment is not impaired. In addition to the layers described above, an arbitrary layer may be provided. Further, any layer other than the light emitting layer 4 may be omitted.
As another layer which the organic electroluminescent element of this Embodiment may have, the electron carrying layer 7 is mentioned, for example. For the purpose of further improving the luminous efficiency of the device, an electron transport layer 7 can be provided between the light emitting layer 4 and the electron injection layer 5 as shown in FIG.

The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode 6 between the electrodes to which an electric field is applied in the direction of the light emitting layer 4. As an electron transport 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. A compound is preferred.
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 thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more as the lower limit, and is usually 300 nm or less, preferably 100 nm or less as the upper limit. The electron transport layer 7 can be formed by being laminated on the light emitting layer 4 by a wet film forming method or a 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 effective to provide the hole blocking layer 8 as shown in FIGS. 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 increases the probability of recombination with electrons in the light emitting layer 4 by blocking the holes moving from the light emitting layer 4 from reaching the electron transport layer 7. There are a role of confining the excitons in the light emitting layer 4 and a role of efficiently transporting electrons injected from the electron transport layer 7 in the direction of the light emitting layer 4.

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

Examples of the material for the hole blocking layer satisfying such conditions include bis (2-methyl-8-quinolinolato) (phenolate) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum. Mixed ligand complexes such as, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Of triazole derivatives (JP-A-11-242996), 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole, etc. 41759) and phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297).
Furthermore, a compound having at least one pyridine ring substituted at the 2,4,6-positions described in WO2005 / 022962 is also preferable as the hole blocking material.

The 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) laminating the hole blocking layer / electron transport layer together, and 4) not using both layers.

  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. Have 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.
And it is preferable that the electron blocking layer 9 also has wet film forming compatibility. Examples of the material used for the electron blocking layer 9 include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (described in WO 2004/084260).

  Note that the structure opposite to that in FIG. 3, 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. Further, as described above, an organic electroluminescent element can be provided between two substrates, at least one of which is highly transparent. Similarly, it is also possible to laminate in a structure opposite to each layer configuration shown in FIGS.

Furthermore, it is possible to adopt a structure in which a plurality of layers shown in FIG. 3 are stacked (a structure in which a plurality of light emitting units are stacked). In this case, if V ₂ O ₅ or the like is used as the charge generation layer (CGL) instead of the interfacial layer (between the light emitting units) (two layers when the anode is ITO and the cathode is Al), the step This is more preferable from the viewpoint of luminous efficiency and driving voltage.

The organic electroluminescent element in the present embodiment can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. .
In addition, the organic electroluminescent element in the present embodiment can be formed as a top emission type element that extracts light emission from above (from the surface opposite to the substrate 1) using a transparent cathode.

  Hereinafter, the present embodiment will be described more specifically based on examples. In addition, this Embodiment is not limited to a following example, unless it deviates from the summary.

Example 1
An organic electroluminescent element having the structure shown in FIG. 4 was produced by the following method.
[Production of Substrate 1 and Anode 2]
First, an indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 with a thickness of 150 nm (sputtered film product; sheet resistance 15 Ω) is 2 mm wide using ordinary photolithography technology and hydrochloric acid etching. The anode 2 was formed by patterning into stripes. 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.

[Preparation of hole injection layer 3]
Next, the hole injection layer 3 was formed by a wet coating method as follows. As a material of the hole injection layer 3, a polymer compound having an aromatic amino group having the following structural formula (PB-1 (weight average molecular weight: 26500, number average molecular weight: 12000)), and a structural formula shown below Using the electron-accepting compound (A-1), spin coating was performed under the following conditions. As a result, a uniform thin film having a thickness of 30 nm was formed.

(Spin coating conditions)
Solvent Anisole Coating concentration PB-1 2.0% by weight
A-1 0.4% by weight
Spinner speed 2000rpm
Spinner rotation time 30 seconds Drying conditions 230 ° C x 5.5 hours

[Preparation of Light-Emitting Layer 4]
Subsequently, the light emitting layer 4 was formed by a wet coating method as follows. As a material for the light emitting layer 4, an organic compound (I-1) having the structural formula shown below was used together with an iridium complex (D-1) having the structural formula shown below, and spin-coated under the following conditions. As a result, a uniform thin film having a thickness of 45 nm was formed.

(Spin coating conditions)
Solvent Xylene Coating concentration I-1 2.5% by weight
D-1 0.13 wt%
Spinner speed 1500rpm
Spinner rotation time 30 seconds Drying conditions 130 ° C x 60 minutes (under reduced pressure)

[Preparation of Electron Transport Layer 7]
Next, an aluminum 8-hydroxyquinoline complex (ET-1) shown below was deposited as the electron transport layer 7. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex is controlled in the range of 321 to 311 ° C., and the degree of vacuum during the deposition is 1.3 to 1.5 × 10 ⁻⁴ Pa (about 1.1 to 1). 0.0 × 10 ⁻⁶ Torr), the deposition rate was 0.08 to 0.16 nm / sec, and the film thickness was 30 nm. In addition, the substrate temperature at the time of vacuum-depositing the electron carrying layer 7 was kept at room temperature.

[Production of Electron Injection Layer 5 and Cathode 6]
The element which performed vapor deposition to the electron carrying layer 7 was taken out in the air from the inside of a vacuum vapor deposition apparatus. On the electron transport layer 7, a 2 mm wide striped shadow mask as a mask for cathode vapor deposition was brought into close contact with the ITO stripe of the anode 2 and placed in another vacuum vapor deposition apparatus.
First, in the same manner as the electron transport layer 7, evacuation was performed until the degree of vacuum in the apparatus became 1.8 × 10 ⁻⁶ Torr (about 2.4 × 10 ⁻⁴ Pa) or less. Next, lithium fluoride (LiF), which is a material of the electron injection layer 5, is deposited at a deposition rate of 0.01 to 0.06 nm / second and a degree of vacuum of 2.0 × 10 ⁻⁶ Torr (about 2.10) using a molybdenum boat. 6 × 10 ⁻⁴ Pa). The film thickness of the electron injection layer 5 formed on the electron transport layer 7 was 0.5 nm.
Next, aluminum was vapor-deposited to form the cathode 6. Vapor deposition was performed as described above. Aluminum is heated by a molybdenum boat, the deposition rate is 0.1 to 0.3 nm / second, and the degree of vacuum is 3.0 to 6.8 × 10 ⁻⁶ Torr (about 4.0 to 9.0 × 10 ⁻⁴ Pa). Film forming conditions were used. The film thickness of the obtained cathode 6 was 80 nm. In addition, the substrate temperature at the time of vapor deposition was kept at room temperature.

  As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The maximum wavelength of the emission spectrum of the device was 513 nm, which was identified as from the iridium complex (D-1). The chromaticity was CIE (x, y) = (0.307, 0.625). The light emission characteristics of this device are shown in Table 1.

(Example 2)
A device was produced under exactly the same conditions except that the organic compound (I-1) of Example 1 was changed to the organic compound (I-2) having the structural formula shown below. The maximum wavelength of the emission spectrum of the device was 513 nm, which was identified as from the iridium complex (D-1). The chromaticity was CIE (x, y) = (0.321, 0.615). The light emission characteristics of this device are shown in Table 1.

(Example 3)
A device was produced under exactly the same conditions except that the organic compound (I-1) of Example 1 was changed to the organic compound (I-3) having the structural formula shown below. The maximum wavelength of the emission spectrum of the device was 512 nm, which was identified as that from the iridium complex (D-1). The chromaticity was CIE (x, y) = (0.312, 0.618). The light emission characteristics of this device are shown in Table 1.

(Comparative Example 1)
An organic electroluminescent element having the structure shown in FIG. 4 was produced by the following method.
[Production of Substrate 1 and Anode 2]
It was produced in the same manner as in Example 1.

[Preparation of hole injection layer 3]
Next, the hole injection layer 3 was formed by a wet coating method as follows. As a material for the hole injection layer 3, a polymer compound having an aromatic amino group having the following structural formula (PB-2 (weight average molecular weight: 29400, number average molecular weight: 12600)) and an electron having the structural formula shown below. Using the receptor compound (A-2), spin coating was performed under the following conditions. As a result, a uniform thin film having a thickness of 30 nm was formed.

(Spin coating conditions)
Solvent Ethyl benzoate Coating solution concentration PB-2 2.0% by weight
A-2 0.4% by weight
Spinner speed 1500rpm
Spinner rotation time 30 seconds Drying conditions 230 ° C x 3 hours

[Preparation of Light-Emitting Layer 4]
Subsequently, the light emitting layer 4 was formed by a wet coating method as follows. As a material of the light emitting layer 4, organic compounds (T-1) and (T-2) having the structural formula shown below are used together with an iridium complex (D-2) having the structural formula shown below, and spin coating is performed under the following conditions. did. As a result, a uniform thin film having a thickness of 100 nm was formed.

(Spin coating conditions)
Solvent Chloroform Coating solution concentration T-1 1.0% by weight
T-2 1.0% by weight
D-2 0.1% by weight
Spinner speed 1500rpm
Spinner rotation time 30 seconds Drying conditions 80 ° C x 60 minutes (under reduced pressure)

[Preparation of Electron Transport Layer 7]
Next, an organic compound (ET-2) having the following structural formula was deposited as the electron transport layer 7. At this time, the degree of vacuum during vapor deposition is 1.79 to 1.71 × 10 ⁻⁴ Pa (about 1.3 × 10 ⁻⁶ Torr), the vapor deposition rate is 0.09 to 0.1 nm / second, and the film thickness is It was 20 nm.

[Production of Electron Injection Layer 5 and Cathode 6]
Next, lithium fluoride (LiF) is used as the electron injection layer 5 by using a molybdenum boat, a deposition rate of 0.009 to 0.013 nm / second, and a degree of vacuum of 1.3 × 10 ⁻⁶ Torr (about 1.76). The film was formed on the electron transport layer 7 with a film thickness of 0.5 nm at × 10 ⁻⁴ Pa).
Next, aluminum was similarly heated by a molybdenum boat, and the deposition rate was 0.06 to 0.19 nm / second, and the degree of vacuum was 2.1 × 10 ⁻⁶ Torr (about 3.15 to 10.0 × 10 ⁻⁴ Pa). ), An aluminum layer having a thickness of 80 nm was formed to complete the cathode 6. The substrate temperature during the above evaporation was kept at room temperature.

  As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The maximum wavelength of the emission spectrum of the device was 514 nm, which was identified as from the iridium complex (D-2). The chromaticity was CIE (x, y) = (0.308, 0.621). The light emission characteristics of this device are shown in Table 1.

(Luminance / current, voltage)
A value at a luminance of 100 cd / m ² is shown.
(Half life)
The value at 1000 cd / A is shown.

  As is apparent from the results in Table 1, when a device is produced by introducing substituents that dissolve each other into each of the host material and the dopant material based on the method of the present embodiment, good emission characteristics are obtained. The organic electroluminescent element which has was obtained. This is presumably because the dopant material was uniformly dispersed in the host material to obtain uniform light emission, and the light emission efficiency was increased.

It is a conceptual diagram which shows an example of a mode that dopant material is disperse | distributing in host material. It is a conceptual diagram which shows the other example of a mode that dopant material has disperse | distributed in host material. It is typical sectional drawing which showed an example of the organic electroluminescent element of this Embodiment. It is typical sectional drawing which showed another example of the organic electroluminescent element of this Embodiment. It is typical sectional drawing which showed another example of the organic electroluminescent element of this Embodiment. It is typical sectional drawing which showed another example of the organic electroluminescent element of this Embodiment. It is typical sectional drawing which showed another example of the organic electroluminescent element of this Embodiment. It is typical sectional drawing which showed another example of the organic electroluminescent element of this Embodiment. It is typical sectional drawing which showed another example of the organic electroluminescent element of this Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Anode, 3 ... Hole injection layer, 4 ... Light emitting layer, 5 ... Electron injection layer, 6 ... Cathode, 7 ... Electron transport layer, 8 ... Hole blocking layer, 9 ... Electron blocking layer

Claims (7)

A composition for forming an organic layer of an organic electroluminescent device containing a dopant material, a host material, and a solvent,
The dopant material and the host material are each non-polymerizable compounds,
The dopant material and the host material are compounds each having an alkyl group having 1 to 30 carbon atoms as a partial structure.   The composition for organic electroluminescent elements according to claim 1, wherein the alkyl group has 2 to 20 carbon atoms.   The dopant material is a compound having an aromatic hydrocarbon ring, an aromatic heterocycle, or a chalcogen atom, and the alkyl group is bonded to the aromatic hydrocarbon ring, the aromatic heterocycle, or the chalcogen atom. The composition for organic electroluminescent elements according to claim 1 or 2.   The host material is a compound having an aromatic hydrocarbon ring, an aromatic heterocycle, or a chalcogen atom, and the alkyl group is bonded to the aromatic hydrocarbon ring, the aromatic heterocycle, or the chalcogen atom. The composition for organic electroluminescent elements according to any one of claims 1 to 3.   The composition for organic electroluminescent elements according to claim 1, wherein the dopant material is a phosphorescent luminescent dye.   The composition for organic electroluminescent elements according to any one of claims 1 to 5, wherein the host material is a carbazole-based compound.   It is an organic electroluminescent element provided with an anode, a cathode, and the organic layer provided between these both on a board | substrate, Comprising: The said organic layer is an organic electric field as described in any one of Claims 1-6. An organic electroluminescent element characterized by being a layer formed using a composition for a light emitting element.

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