TW202309244A - Composition for organic electroluminescent element, organic electroluminescent element, display device, and illuminator - Google Patents

Abstract

A composition for organic electroluminescent elements which comprises a functional material, a compound represented by formula (1), and an aliphatic ester solvent having two or more carbonyl groups and/or an aromatic diester solvent. [In formula (1), a is an integer of 0-4, R1 and R2 each independently represent a C1-C12 alkyl group or a C1-C12 alkoxy group, and when a is an integer of 2-4, the R2 moieties may be the same or different.].

Description

Composition for organic electroluminescent device, organic electroluminescent device, display device, and lighting device

The present invention relates to a composition for an organic electroluminescence element that can be effectively used to form a light emitting layer of an organic electroluminescence element (hereinafter sometimes referred to as "organic EL (Electro-Luminescence) element"). In addition, the present invention relates to an organic electroluminescent device having a light emitting layer formed using the composition for organic electroluminescent device, a method for manufacturing the same, a display device and a lighting device having the organic electroluminescent device.

Various electronic devices using organic EL elements, such as organic EL lighting and organic EL displays, are being put into practical use. The organic electroluminescence element consumes little power due to the low applied voltage, and can also emit light in three primary colors. Therefore, it is not only applied to large-scale display monitors, but also to small and medium-sized displays represented by mobile phones or smart phones.

An organic electroluminescent device is manufactured by laminating multiple layers such as a light-emitting layer, a charge injection layer, and a charge transport layer. Currently, most organic electroluminescent devices are manufactured by evaporating organic materials under vacuum. However, the evaporation process of the vacuum evaporation method is complicated and the productivity is poor. In addition, it is extremely difficult to increase the area of a panel for lighting or display in an organic electroluminescent device manufactured by a vacuum evaporation method.

In recent years, a wet film-forming method (coating method) has been studied as a process for efficiently manufacturing an organic electroluminescence element that can be used for a large display or lighting. The wet film-forming method has an advantage that a stable layer can be easily formed as compared with the vacuum deposition method. Therefore, it is expected to be applied to mass-production or large-scale displays of displays or lighting devices.

In order to manufacture an organic electroluminescent device by a wet film-forming method, it is necessary to dissolve a functional material in an organic solvent and use it as an ink. If the solubility of the functional material in the organic solvent is low, operations such as heating for a long time are required, and therefore there is a possibility that the material may deteriorate before use. In addition, if a uniform state cannot be maintained for a long period of time in a solution state, material will be precipitated from the solution, making it impossible to form a film using an inkjet device or the like. The organic solvent used in the ink is required to have solubility in two senses, namely, rapidly dissolving the functional material and keeping the functional material in a homogeneous state after dissolution.

In recent years, for the purpose of suppressing the reduction of the luminous efficiency or the driving life of the organic electroluminescent element when the organic electroluminescent element is manufactured after storing the ink for a long time, attempts have been made to contain a phenol derivative in the ink (for example, Patent Document 1 and patent literature 2).

It is disclosed that an aromatic ester is used as an organic solvent used in ink for the purpose of improving the flatness of a film when a functional layer is formed by a wet film-forming method (for example, Patent Document 3).

Patent Document 1: Japanese Patent Laid-Open No. 2015-63662 Patent Document 2: Japanese Patent Laid-Open No. 2015-93938 Patent Document 3: International Publication No. 2019/212022

According to the prior art described above, by including the phenol derivative in the ink, it is possible to suppress the deterioration of the functional material, which is one cause of reduction in luminous efficiency or driving life, even when the ink is stored for a long time. However, the stability of the liquid physical properties of the ink, especially the stability of the surface tension of the ink is not sufficient, and improvement of the stability of the liquid physical properties is required.

The object of the present invention is to provide a composition for organic electroluminescent elements, which is used for forming a light-emitting layer in an organic electroluminescent element by wet film formation, and which has the stability of liquid physical properties, especially the stability of the surface tension of ink Improved.

The present inventors found that by using an aliphatic ester and/or an aromatic diester solvent having two or more carbonyl groups as a solvent, even when a phenol derivative is contained, the change in the physical properties of the liquid becomes small.

The gist of the present invention is as follows.

[1] A composition for an organic electroluminescence device, comprising: a functional material; a compound represented by the following formula (1); and an aliphatic ester solvent and/or an aromatic diester solvent having two or more carbonyl groups.

[chemical 1]

[In the formula, a is an integer of 0 to 4, and R ¹ and R ² each independently represent an alkyl group having 1 to 12 carbons or an alkoxy group having 1 to 12 carbons. When a is an integer of 2 to 4, a plurality of R ² may be the same or different. ]

[2] The composition for an organic electroluminescence device according to [1], wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having two ester groups.

[3] The composition for an organic electroluminescence device according to [1], wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having one ester group and one ketone group.

[4] The composition for an organic electroluminescence device according to [1], wherein the aliphatic ester solvent having two or more carbonyl groups is the following formula (9-1) or the following formula (9-2) The indicated solvent.

[Chem 2]

[In the formula, R ²⁴ represents an alkylene group. R ²⁵ and R ²⁶ each independently represent an alkyl group. R ²⁴ and R ²⁵ may be bonded to each other to form a ring. ]

[Chem 3]

[In the formula, R ²⁷ represents an alkylene group. R ²⁸ and R ²⁹ each independently represent an alkyl group. R ²⁷ and R ²⁸ , or R ²⁷ and R ²⁹ may be bonded to each other to form a ring. ]

[5] The composition for an organic electroluminescence device according to [1], wherein the aromatic diester solvent is a solvent represented by the following formula (9-3).

[chemical 4]

[In the formula, Ar ³¹ represents an arylylene group. R ^30a and R ^30b each independently represent an alkyl group. R ^30a and Ar ³¹ may be bonded to each other to form a ring. ]

[6] The composition for an organic electroluminescence device according to any one of [1] to [5], wherein the compound represented by the formula (1) is represented by the following formula (1-1) compound.

[chemical 5]

[In the formula, b is an integer of 0-3. R ³ , R ⁴ , and R ⁵ each independently represent an alkyl group having 1 to 12 carbons or an alkoxy group having 1 to 12 carbons. When b is an integer of 2 to 3, a plurality of R ⁵ may be the same or different. ]

[7] The composition for an organic electroluminescence device according to [6], wherein the compound represented by the formula (1-1) is a compound represented by the following formula (1-2).

[chemical 6]

[In the formula, b and R ⁵ have the same meaning as b and R ⁵ in the formula (1-1). ]

[8] The composition for an organic electroluminescence device according to any one of [1] to [7], which contains an iridium complex as the functional material.

[9] The composition for an organic electroluminescence device according to [8], wherein the functional material contains an iridium complex represented by the following formula (2).

[chemical 7]

[In the formula, R ⁷ and R ⁸ are independently an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, an alkoxy group with 1 to 20 carbons, or an alkoxy group with 3 carbons. A (hetero)aryloxyl group with ∼20 carbons, an alkylsilyl group with 1 to 20 carbons, an arylsilyl group with 6 to 20 carbons, an alkylcarbonyl group with 2 to 20 carbons, an aromatic group with 7 to 20 carbons Any one of a carbonylcarbonyl group, an alkylamino group having 1 to 20 carbons, an arylamino group having 6 to 20 carbons, and a (hetero)aryl group having 3 to 30 carbons, or a combination thereof. These groups may further have a substituent. When there are a plurality of R ⁷ and R ⁸ , the plurality of R ⁷ and R ⁸ may be the same or different. Adjacent R ⁷ or R ⁸ bonded to the benzene ring may bond to each other to form a ring condensed to the benzene ring. d is an integer of 0-4. e is an integer of 0-3. m is an integer of 1-20. n is an integer of 0-2. Ring A is pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, oxazole ring, thiazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, carba Any of the phyline rings. Ring A may also have a substituent, and the substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbons, a (hetero)aralkyl group having 7 to 40 carbons, or an aralkyl group having 1 to 20 carbons. Alkoxy, (hetero)aryloxy with 3 to 20 carbons, alkylsilyl with 1 to 20 carbons, arylsilyl with 6 to 20 carbons, alkylcarbonyl with 2 to 20 carbons, Any of an arylcarbonyl group with 7 to 20 carbons, an alkylamino group with 2 to 20 carbons, an arylamino group with 6 to 20 carbons, and a (hetero)aryl group with 3 to 20 carbons, or a combination of these. Adjacent substituents bonded to ring A may bond to each other to form a ring condensed on ring A. Z ¹ represents a direct bond or an aromatic linking group having a valence of m+1. L ¹ represents an auxiliary ligand. l is an integer of 1-3. When a plurality of auxiliary ligands exist, they may be different or the same. ]

[10] The composition for an organic electroluminescence device according to [9], wherein the Z ¹ includes a trivalent group represented by the following formula (2-2A) or formula (2-2B).

[chemical 8]

[11] A method for manufacturing an organic electroluminescent device, comprising the step of forming a light-emitting layer by a wet film-forming method using the composition for an organic electroluminescent device according to any one of [1] to [10] .

[12] An organic electroluminescent device having a light emitting layer formed using the composition for an organic electroluminescent device according to any one of [1] to [10].

[13] A display device comprising the organic electroluminescent element according to [12].

[14] A lighting device comprising the organic electroluminescent element according to [12]. [Effect of the invention]

The composition for an organic electroluminescence device of the present invention is excellent in the stability of liquid physical properties, especially the stability of the surface tension of ink. Therefore, even if the composition for an organic electroluminescent device of the present invention is used for the production of an organic electroluminescent device after long-term storage, the reduction in luminous efficiency or driving life is small, and since the change in the physical properties of the liquid is small, unevenness can be obtained. Small display or lighting fixtures. That is, the composition for an organic electroluminescence device of the present invention is applicable to large-area coating and can be stored for a long period of time.

In the present invention, the mechanism of action by which such effects can be obtained is estimated as follows. Since the composition for an organic electroluminescence device of the present invention contains the compound represented by the above formula (1) as a phenol derivative, deterioration of the functional material can be suppressed even when the ink is stored for a long time. Furthermore, since an aliphatic ester and/or an aromatic diester solvent having two or more carbonyl groups is contained as a solvent, it is possible to reduce changes in liquid physical properties accompanying oxidation of the phenol derivative.

By making the ink contain a phenol derivative, deterioration due to oxidation of the functional material can be suppressed, but it is considered that the phenol derivative itself is oxidized. In the case of phenols being oxidized, phenoxy radicals are usually formed due to proton transfer or hydrogen atom transfer after one-electron oxidation. Thereafter, although it is uncertain whether the phenoxy radicals in the ink will be further changed into other substances such as benzoquinones or peroxides, in any case, they will have a structure without phenolic hydroxyl groups. It is considered that the phenolic hydroxyl group exhibits acidity due to the resonance effect of the aromatic ring in addition to hydrogen bonding, but these properties are greatly changed by oxidation.

It is considered that the structural change due to the oxidation of the phenol derivative as described above affects the liquid physical properties of the ink even if the content of the phenol derivative is small. However, by using an aliphatic ester solvent and/or an aromatic diester solvent containing two or more carbonyl groups as polar groups as a solvent, changes in the physical properties of the liquid can be suppressed.

Hereinafter, embodiments of the present invention will be described in detail. This invention is not limited to the following embodiment, Various deformation|transformation can be implemented within the range of the summary.

In this specification, (hetero)aralkyl, (hetero)aryloxy, and (hetero)aryl represent respectively aralkyl that may contain heteroatoms, aryloxy that may contain heteroatoms, and aryloxy that may contain heteroatoms. the aryl. "Heteroatoms may be included" means that among the carbon atoms forming the main skeleton of the aryl group, aralkyl group or aryloxy group, one or two or more carbon atoms are substituted with heteroatoms. Examples of hetero atoms include nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, and silicon atoms. Among them, nitrogen atoms are preferred from the viewpoint of durability. The same is true for (hetero)arylylene groups.

In this specification, "aromatic linking group" means not only an aromatic hydrocarbon linking group, that is, a linking group having an aromatic hydrocarbon ring, but also a heteroaromatic linking group, that is, a linking group having a heteroaromatic ring. Aromatic linking group.

[Composition for organic electroluminescence device] The composition for an organic electroluminescence device of the present invention is characterized by comprising: a functional material; a compound represented by the following formula (1); and an aliphatic ester solvent and/or an aromatic diester solvent having two or more carbonyl groups.

[chemical 9]

[In the formula, a is an integer of 0-4. R ¹ and R ² each independently represent an alkyl group having 1 to 12 carbons or an alkoxy group having 1 to 12 carbons. When a is an integer of 2 to 4, a plurality of R ² may be the same or different. ]

[functional material] The composition for an organic electroluminescent device of the present invention contains a functional material. The functional material refers to a light-emitting material or a charge-transporting material contained in the light-emitting layer of an organic electroluminescent device.

From the aspect that the energy for exciting the triplet state can contribute to light emission, the composition for an organic electroluminescent device of the present invention preferably contains a phosphorescent organic metal complex as a functional material, and among them, preferably contains An organometallic complex with iridium as the central element is an iridium complex.

[Iridium complex] The iridium complex contained in the composition for an organic electroluminescence device of the present invention is preferably represented by the following formula (2) from the viewpoint of high solubility in an organic solvent and high heat resistance.

[chemical 10]

[In the formula, R ⁷ and R ⁸ are independently an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, an alkoxy group with 1 to 20 carbons, or an alkoxy group with 3 carbons. A (hetero)aryloxyl group with ∼20 carbons, an alkylsilyl group with 1 to 20 carbons, an arylsilyl group with 6 to 20 carbons, an alkylcarbonyl group with 2 to 20 carbons, an aromatic group with 7 to 20 carbons Any one of a carbonylcarbonyl group, an alkylamino group having 1 to 20 carbons, an arylamino group having 6 to 20 carbons, and a (hetero)aryl group having 3 to 30 carbons, or a combination thereof. These groups may further have a substituent. When there are a plurality of R ⁷ and R ⁸ , the plurality of R ⁷ and R ⁸ may be the same or different. Adjacent R ⁷ or R ⁸ bonded to the benzene ring may bond to each other to form a ring condensed to the benzene ring. d is an integer of 0-4. e is an integer of 0-3. m is an integer of 1-20. n is an integer of 0-2. Ring A is pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, oxazole ring, thiazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, carba Any of the phyline rings. Ring A may also have a substituent, and the substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbons, a (hetero)aralkyl group having 7 to 40 carbons, or an aralkyl group having 1 to 20 carbons. Alkoxy, (hetero)aryloxy with 3 to 20 carbons, alkylsilyl with 1 to 20 carbons, arylsilyl with 6 to 20 carbons, alkylcarbonyl with 2 to 20 carbons, Any of an arylcarbonyl group with 7 to 20 carbons, an alkylamino group with 2 to 20 carbons, an arylamino group with 6 to 20 carbons, and a (hetero)aryl group with 3 to 20 carbons, or a combination of these. Adjacent substituents bonded to ring A may bond to each other to form a ring condensed on ring A. Z ¹ represents a direct bond or an aromatic linking group having a valence of m+1. L ¹ represents an auxiliary ligand. l is an integer of 1-3. When a plurality of auxiliary ligands exist, they may be different or the same. ]

In formula (1), in terms of durability, R ⁷ and R ⁸ are each independently preferably an alkyl group having 1 to 20 carbons, a (hetero)aralkyl group having 7 to 40 carbons, a carbon An arylamino group with 6 to 20 carbons, or a (hetero)aryl group with 3 to 30 carbons, more preferably an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, or a carbon A (hetero)aryl group whose number is 3-20.

Two adjacent R ⁷ and R ⁸ may be linked to each other to form a ring condensed to the benzene ring to which these groups are bonded.

From the viewpoint of easy production, d is preferably 0. d is preferably 1 or 2, more preferably 1, since the solubility can be improved. When two adjacent R ⁷ are connected to each other to form a ring, d is preferably 2.

From the viewpoint of easy production, e is preferably 0. e is preferably 1 or 2, more preferably 1, since durability and solubility can be improved. When two adjacent R ⁸ are connected to each other to form a ring, e is preferably 2 or 3.

When R ⁷ and R ⁸ further have a substituent, examples of the substituent include: a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbons, and a (hetero)aryl group having 7 to 40 carbons. Alkyl, alkoxy with 1 to 20 carbons, (hetero)aryloxy with 3 to 20 carbons, alkylsilyl with 1 to 20 carbons, arylsilyl with 6 to 20 carbons, carbon Alkylcarbonyl with 2 to 20 carbons, arylcarbonyl with 7 to 20 carbons, alkylamino with 2 to 20 carbons, arylamino with 6 to 20 carbons, and (hetero ) any of the aryl groups, or a combination of these.

In order to improve the solubility of the phenyl group having a tertiary butyl group at the end in an organic solvent, m is preferably 2 or more. The phenyl group having a tertiary butyl group at the end contributes little to charge transport or luminescence, so if too much, the driving voltage may increase or the luminous efficiency may decrease. Therefore, m is preferably 8 or less, more preferably 4 or less.

In terms of both solubility, low driving voltage, and high luminous efficiency, the iridium complex represented by formula (2) preferably has 4 or more, especially 6 or more, based on the iridium complex as a whole. , and less than 48, especially less than 24 such terminal tertiary butyl groups.

n is preferably 0 or 1 in terms of ease of manufacture. It is preferable that n is 0 since there is little concern that the driving voltage will increase. n is preferably 1 or 2 at the point that the solubility can be improved.

In terms of durability, ring A is preferably a pyridine ring, a pyrimidine ring, or an imidazole ring, and more preferably a pyridine ring.

In terms of durability and solubility improvement, the hydrogen atom on ring A is preferably an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, or an alkyl group with 3 carbons. ~20 (hetero)aryl substitutions. In terms of ease of manufacture, the hydrogen atoms on ring A are preferably unsubstituted. When the hydrogen atom on the ring A is substituted by a phenyl or naphthyl group which may have a substituent, excitons are easily generated when used in an organic electroluminescent device, so that the luminous efficiency can be improved, which is preferable.

In ring A, the substituents on ring A are bonded to each other to form a condensed ring condensed on ring A, thereby forming quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, etc. ring and carboline ring. In this case, since the emission wavelength becomes longer, it can be effectively used for the application of red light emission. Among them, ring A preferably has a quinoline ring, an isoquinoline ring, or a quinazoline ring in terms of durability and red light emission.

In terms of ease of manufacture, Z ¹ is preferably a direct bond. Z ¹ is preferably an aromatic linking group having a valency of m+1 since there is little concern about the increase in driving voltage.

When m is 1, in terms of durability, ^Z1 is preferably a phenylene group, a biphenylene group, a terphenylene group, or a fluorene diyl group, and particularly preferably a p-phenylene group. .

When m is 2 or more, in terms of durability, ^Z1 preferably includes a benzene ring at the 1,3,5-position as the bonding position or a benzene ring at the 2,4,6-position as the bonding position triazine ring.

Z ¹ preferably includes a trivalent group represented by the following formula (2-2A) or formula (2-2B).

[chemical 11]

The group represented by formula (2-2A) or formula (2-2B) is more preferably bonded to the benzene ring or ring A to which iridium is bonded.

L ¹ is an auxiliary ligand. Although not particularly limited, L ¹ is preferably a monovalent didentate ligand, more preferably selected from ligands represented by the following formula (2A), formula (2B), and formula (2C). The dotted lines in the following formulas (2A) to (2C) represent coordination bonds. When l is 1 and there are two auxiliary ligands L ¹ , the auxiliary ligands L ¹ may have the same or different structures. When l is 3, L ¹ does not exist.

[chemical 12]

In the formula (2A) and formula (2B), R ⁹ and R ¹⁰ are selected from the same group as the R ⁷ and R ⁸ , and the preferred examples are also the same.

g is an integer of 0-4. h is an integer of 0-4. From the viewpoint of easy production, g and h are preferably 0. g and h are preferably 1 or 2, more preferably 1, since the solubility can be improved.

Ring B is pyridine ring, pyrimidine ring, imidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, carboline ring, benzothiazole ring, benzoxa Any of the azole rings. These may also have a substituent. In terms of durability, ring B is preferably a pyridine ring, a pyrimidine ring, or an imidazole ring, and more preferably a pyridine ring.

In terms of durability and solubility improvement, the hydrogen atom on ring B is preferably an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, or an alkyl group with 3 carbons. ~20 (hetero)aryl substitutions. In terms of ease of production, the hydrogen atom on ring B is preferably unsubstituted. When the hydrogen atom on the ring B is substituted by a phenyl or naphthyl group which may have a substituent, excitons are easily generated when used in an organic electroluminescent device, and thus luminous efficiency can be improved, which is preferable.

In ring B, the substituents on ring B are bonded to each other to form a condensed ring condensed on ring B, thereby forming quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring In this case, a ring and a carboline ring are preferable in terms of easily generating excitons on the auxiliary dopant and thus improving luminous efficiency. Among them, ring B is preferably formed with a quinoline ring, isoquinoline ring, or quinazoline ring in terms of durability and red light emission.

In formula (2C), R ¹¹ to R ¹³ independently represent a hydrogen atom, an alkyl group with 1 to 20 carbons that may be substituted by a fluorine atom, a phenyl group that may be substituted with an alkyl group with 1 to 20 carbons, or halogen atom. More preferably, R ¹¹ and R ¹³ are methyl or tert-butyl, and R ¹² is a hydrogen atom, an alkyl group with 1 to 20 carbons, or a phenyl group.

The compound represented by the formula (2) is also preferably a compound represented by the following formula (2-2) in which adjacent R ⁸ are bonded to each other to form a fluorene ring.

[chemical 13]

[In formula (2-2), R ⁷ , d, m, n, ring A, Z ¹ , L ¹ , l and in formula (2) R ⁷ , d, m, n, ring A, Z ¹ , L ¹ and l have the same meaning. R ¹⁵ to R ¹⁷ are substituents. ]

Examples of R ¹⁵ include the substituents that R ⁸ may have. More preferably, R ¹⁵ is an alkyl group having 1-20 carbons, an aromatic hydrocarbon group having 6-30 carbons which may be substituted by one or two alkyl groups having 1-20 carbons. Here, the aromatic hydrocarbon group having 6 to 30 carbon atoms refers to a monocyclic, bicyclic condensed ring, or tricyclic condensed ring, or a group in which a plurality of monocyclic, bicyclic condensed rings, or tricyclic condensed rings are linked. R ¹⁵ is more preferably an alkyl group having 1 to 20 carbons, particularly preferably an alkyl group having 1 to 8 carbons.

R ¹⁶ and R ¹⁷ are a part of the R ⁸ or a substituent that the R ⁸ may have, preferably each independently an alkyl group with 1 to 12 carbons, and one or two groups with 1 to 12 carbons may be An aromatic hydrocarbon group with 6 to 20 carbons substituted by an alkyl group, an alkoxy group with 1 to 12 carbons, or an aromatic hydrocarbon with 6 to 20 carbons that may be substituted by one or two alkoxyls with 1 to 12 carbons family of hydrocarbon groups. Here, the aromatic hydrocarbon group having 6 to 20 carbon atoms means a monocyclic, bicyclic condensed ring, or tricyclic condensed ring, or a group in which a plurality of monocyclic, bicyclic condensed rings, or tricyclic condensed rings are linked. R ¹⁶ and R ¹⁷ are further preferably independently an alkyl group with 1 to 8 carbons, or an aromatic hydrocarbon group with 6 or 12 carbons which may be substituted by one or two alkyl groups with 1 to 8 carbons, especially It is preferably an alkyl group having 1 to 8 carbons, or an aromatic hydrocarbon group having 6 carbons which may be substituted by one or two alkyl groups having 1 to 8 carbons. Here, the aromatic hydrocarbon structure having 6 carbon atoms is a benzene structure, and the aromatic hydrocarbon structure having 12 carbon atoms is a biphenyl structure.

A preferred specific example of the iridium complex, that is, the compound represented by formula (2) that can be included as a functional material in the composition for an organic electroluminescent device of the present invention is shown below.

[chemical 14]

[chemical 15]

[chemical 16]

The composition for an organic electroluminescence device of the present invention may contain only one kind of these iridium complexes, or may contain two or more kinds thereof.

[Charge Transport Material] In the composition for an organic electroluminescent device of the present invention, the charge-transporting material that may be included as a functional material is a material having positive charge (hole) or negative charge (electron) transportability. The charge-transporting material is not particularly limited as long as it does not impair the effects of the present invention, and known materials can be used.

As the charge-transporting material, a compound or the like previously used in a light-emitting layer of an organic electroluminescent device can be used. As the charge-transporting material, a compound used as a host material of the light-emitting layer is particularly preferable.

Specific examples of charge-transporting materials include aromatic amine-based compounds, phthalocyanine-based compounds, porphyrin-based compounds, oligothiophene-based compounds, polythiophene-based compounds, benzylphenyl-based compounds, fluorenyl-based Compounds formed by linking tertiary amines, hydrazone-based compounds, silazane-based compounds, silanamine-based compounds, phosphamine-based compounds, quinacridone-based compounds, etc. are used as the hole injection layer 3 described later. Compounds exemplified as hole transporting compounds and the like. In addition, electron-transporting compounds such as anthracene-based compounds, pyrene-based compounds, carbazole-based compounds, pyridine-based compounds, phenanthroline-based compounds, oxadiazole-based compounds, and silole-based compounds, etc. .

As the charge-transporting material, for example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl containing two or more tertiary amines and Aromatic diamines with two or more condensed aromatic rings substituted on nitrogen atoms (Japanese Patent Laid-Open No. 5-234681); 4,4',4''-tris(1-naphthylphenylamine) Aromatic amine compounds with a starburst structure such as triphenylamine (Journal of Luminescence, J. Lumin., vol. 72-74, p. 985, 1997); Aromatic amine compounds of tetramers of amines (Chemical Communication, Chem. Commun., p. 2175, 1996); 2,2',7,7'-tetra-(diphenylamino) -9,9'-spirobifluorene and other fluorene compounds (Synthetic Metals, Synth. Metals, Volume 91, Page 209, 1997); 4,4'-N,N'-Dicarbazole biphenyl Compounds such as carbazole-based compounds and the like are exemplified as hole transporting compounds of the hole transporting layer 4 described later. As other charge-transporting materials, 2-(4-biphenyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD), 2, 5-bis(1-naphthyl)-1,3,4-oxadiazole (BND) and other oxadiazole compounds; 2,5-bis(6'-(2',2''-bipyridyl) )-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy) and other silacyclopentadiene compounds; 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline, BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP (bathocuproin), bathocuproin) and other phenanthroline compounds, etc.

In terms of film-forming properties, the charge-transporting material that can be included in the composition for organic electroluminescent devices of the present invention preferably has a repeating unit including a structure represented by the following formula (3) (hereinafter, sometimes A polymer compound called "repeating unit (3)".)

[chemical 17]

[In formula (3), R ¹⁹ and R ²⁰ are independently an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, an alkoxy group with 1 to 20 carbons, or an alkoxy group with 1 to 20 carbons. (hetero)aryloxyl group with 3 to 20 carbons, alkylsilyl group with 1 to 20 carbons, arylsilyl group with 6 to 20 carbons, alkylcarbonyl with 2 to 20 carbons, and alkylsilyl group with 7 to 20 carbons Any one of an arylcarbonyl group, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 30 carbon atoms, or a combination thereof. These groups may further have a substituent. ]

In formula (3), in terms of solubility, R ¹⁹ and R ²⁰ are each independently preferably an alkyl group having 1 to 20 carbons or a (hetero)aralkyl group having 7 to 40 carbons. In terms of heat resistance, R ¹⁹ and R ²⁰ are each independently preferably a (hetero)aryl group having 3 to 30 carbon atoms.

Among the polymer compounds having the repeating unit (3) that can be included in the composition for organic electroluminescent devices of the present invention, it is preferable that the repeating unit (3) also includes Contains a repeating unit having a structure represented by the following formula (3-1) (hereinafter, may be referred to as "repeating unit (3-1)"). In this case, the repeating unit (3) may also be included in the following repeating unit (3-1).

[chemical 18]

[In formula (3-1), Ar ²¹ to Ar ²³ each independently represent a divalent (hetero)arylylene group having 3 to 30 carbon atoms which may have a substituent. Ar ²⁴ and Ar ²⁵ each independently represent a (hetero)aryl group having 3 to 30 carbon atoms which may have a substituent. r represents an integer of 0-2. ]

In terms of durability, Ar ²¹ to Ar ²³ are each independently preferably a phenylene group, a biphenylene group, a terphenylene group, a fluorene diyl group, or arbitrarily selecting the number of carbon atoms formed by linking these groups. The divalent group below 30 is especially preferably a p-phenylene group or a biphenylene group. These groups may have a substituent.

When formula (3-1) includes the structure represented by formula (3), when Ar ²¹ , Ar ²² or r is 1 or more, at least one selected from at least one Ar ²³ is represented by formula (3) A fluorenyl group that may have a substituent at the 9,9' position.

In terms of durability, Ar ²⁴ and Ar ²⁵ are each independently preferably a phenyl group, a biphenyl group, a terphenyl group, or a fluorenyl group, and particularly preferably a phenyl group or a fluorenyl group. These groups may have a substituent.

The polymer compound having the repeating unit (3) that may be contained in the composition for an organic electroluminescence device of the present invention may contain only one kind of repeating unit (3), or may contain two or more kinds. In addition, only one kind of repeating unit (3-1) may be included, or two or more kinds may be included.

The weight-average molecular weight (Mw) of the polymer compound having the repeating unit (3) that may be included in the composition for organic electroluminescent devices of the present invention is usually 2,000,000 or less, preferably 500,000 or less, more preferably 100,000 or less, and more preferably It is preferably 50,000 or less, and usually 2,500 or more, preferably 5,000 or more, more preferably 10,000 or more, still more preferably 20,000 or more. When a weight average molecular weight is below the said upper limit, it will be excellent in the solubility to a solvent, and it will also be excellent in film-forming property. When a weight average molecular weight is more than the said lower limit, the glass transition temperature, a melting point, and a vaporization temperature of a polymer compound are high, and it is excellent in heat resistance.

The number average molecular weight (Mn) of the polymer compound having the repeating unit (3) that may be contained in the composition for organic electroluminescence device of the present invention is usually 1,000,000 or less, preferably 250,000 or less, more preferably 50,000 or less, and further It is preferably 25,000 or less, and usually 2,000 or more, preferably 4,000 or more, more preferably 8,000 or more, and still more preferably 15,000 or more.

The dispersion (Mw/Mn) of the polymer compound having the repeating unit (3) that may be contained in the composition for an organic electroluminescent device of the present invention is preferably 3.5 or less, more preferably 2.5 or less, particularly preferably 2.0 or less . The smaller the value of the degree of dispersion, the better, so the lower limit value is ideally 1. When the degree of dispersion of the polymer compound is not more than the above-mentioned upper limit, purification is easy, and solubility in a solvent and charge transportability are good.

Usually, the weight average molecular weight of the polymer compound is determined by size exclusion chromatography (Size Exclusion Chromatography, SEC) measurement. In the SEC measurement, the higher the molecular weight component, the shorter the dissolution time, and the lower the low molecular weight component, the longer the dissolution time. Using a calibration curve calculated from the elution time of polystyrene (standard sample) with a known molecular weight, the elution time of the sample was converted into molecular weight to calculate the weight average molecular weight. The number average molecular weight was obtained similarly.

The method for producing the polymer compound having the repeating unit (3) that can be contained in the composition for an organic electroluminescence device of the present invention is not particularly limited, as long as the polymer compound having the repeating unit (3) can be obtained. For example, a polymerization method based on Suzuki reaction, a polymerization method based on Grignard reaction, a polymerization method based on Yamamoto reaction, a polymerization method based on Ullmann reaction, a polymerization method based on Buchwald-Hartwig (Buchwald-Hartwig) polymerization method to produce.

[Phenol derivatives] The composition for an organic electroluminescent device of the present invention contains a phenol derivative as a compound represented by the following formula (1).

[chemical 19]

[In the formula, a is an integer of 0-4. R ¹ and R ² each independently represent an alkyl group having 1 to 12 carbons or an alkoxy group having 1 to 12 carbons. When a is an integer of 2 to 4, a plurality of R ² may be the same or different. ]

In the compound represented by formula (1), since there is an alkyl or alkoxy group as an electron-donating group at the o-position of the hydroxyl group, the oxidation-reduction potential of the compound represented by formula (1) shifts to the negative side, The highest occupied molecular orbital (HOMO) becomes shallower, and itself is easily oxidized. Therefore, the oxidation of the functional material contained at the same time is suppressed.

It is preferable that a is 1 or 2 from the point which becomes a moderate oxidation-reduction potential.

When R ¹ and R ² are alkyl groups having 1 to 12 carbon atoms, examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, second butyl, third butyl, and pentyl , Isopentyl, Hexyl, Cyclohexyl, Heptyl, Octyl, 2-Ethylhexyl, Nonyl, Decyl, Undecyl, Dodecyl.

When R ¹ and R ² are alkoxy groups having 1 to 12 carbon atoms, examples include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, and second butoxy , the third butoxy, pentyloxy, isopentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, 2-ethylhexyloxy, nonyloxy, Decyloxy, Undecyloxy, Dodecyloxy.

In terms of large steric hindrance, the coupling reaction of phenoxy radicals generated after oxidation is inhibited, and they can function as antioxidants again, R ¹ and R ² are preferably secondary alkyl or tertiary alkyl group, more preferably a tertiary alkyl group. The o-position of the hydroxyl group is preferably a tertiary butyl group which is the smallest tertiary alkyl group in terms of low cost and low molecular weight so that it does not easily remain in the light-emitting layer after film formation.

Both of the o-positions of the hydroxyl group are preferably an alkyl or alkoxy group in terms of a moderate oxidation-reduction potential and high stability of phenoxy radicals generated after oxidation. That is, the composition for an organic electroluminescence device of the present invention preferably contains a compound represented by the following formula (1-1) as the compound represented by the formula (1).

[chemical 20]

[In the formula, b is an integer of 0-3. R ³ , R ⁴ , and R ⁵ each independently represent an alkyl group having 1 to 12 carbons or an alkoxy group having 1 to 12 carbons. When b is an integer of 2 to 3, a plurality of R ⁵ may be the same or different. ]

b is preferably 0 or 1 from the viewpoint of having a moderate oxidation-reduction potential.

In terms of the large steric hindrance, the inhibition of the coupling reaction between the phenoxy radicals generated after oxidation, and the ability to function as an antioxidant again, the o-position of the hydroxyl group is preferably a secondary alkyl or a tertiary alkane group, more preferably a tertiary alkyl group. The o-position of the hydroxyl group is preferably a tertiary butyl group which is the smallest tertiary alkyl group in terms of low cost and low molecular weight so that it does not easily remain in the light-emitting layer after film formation. That is, the composition for an organic electroluminescence device of the present invention preferably contains a compound represented by the following formula (1-2) as the compound represented by the formula (1).

[chem 21]

[In the formula, b and R ⁵ have the same meaning as b and R ⁵ in the formula (1-1). ]

As described above, b is preferably 0 or 1 from the viewpoint of obtaining a moderate oxidation-reduction potential.

[solvent] The composition for an organic electroluminescence device of the present invention contains an aliphatic ester solvent and/or an aromatic diester solvent having two or more carbonyl groups.

The solvent contained in the composition for an organic electroluminescence device of the present invention is a volatile liquid component for forming a layer containing a functional material by wet film formation. The solvent is preferably a solvent that dissolves the light-emitting material or the charge-transporting material as a functional material well.

＜Aliphatic ester solvents having two or more carbonyl groups＞ The aliphatic ester solvent having two or more carbonyl groups also has one or more carbonyl groups in addition to the carbonyl groups contained in the aliphatic carboxylate moiety. The carbonyl group that the solvent further has may or may not be an aliphatic carboxylate group, but it can further suppress the change in the liquid physical properties of the ink due to the structural change caused by the oxidation of the phenol derivative. In terms of aspects, aliphatic carboxylate groups are preferred.

As examples of carbonyl groups that are not aliphatic carboxylate groups, aromatic carboxylate groups, aliphatic carboxylic acid amide groups, aromatic carboxylic acid amide groups, ketone groups, and aldehyde groups can be cited, which can further inhibit A ketone group is preferable in terms of changing the liquid physical properties of the ink due to the structural change caused by the oxidation of the derivative.

As the aliphatic ester solvent having two or more carbonyl groups, a compound having two ester groups is preferred in that it can further suppress changes in liquid physical properties of the ink due to structural changes caused by oxidation of phenol derivatives. In addition, a compound having one ester group or one ketone group is preferable in terms of better solubility of a light-emitting material or a charge-transporting material that is a functional material.

The composition for an organic electroluminescent device of the present invention preferably contains a compound represented by the following formula (9-1) as an aliphatic dicarboxylic acid ester.

[chem 22]

[In the formula, R ²⁴ represents an alkylene group. R ²⁵ and R ²⁶ each independently represent an alkyl group. R ²⁴ and R ²⁵ may be bonded to each other to form a ring. ]

R ²⁴ is preferably an alkylene group having 1 to 20 carbons, more preferably an alkylene group having 2 to 12 carbons, in terms of moderate volatility as a solvent. R ²⁵ and R ²⁶ are each independently preferably an alkyl group having 1 to 20 carbons, more preferably an alkyl group having 1 to 6 carbons, in terms of moderate volatility as a solvent.

R ²⁴ as an alkylene group may be any of linear, branched, or cyclic. ^R24 is preferably a straight-chain alkylene group in terms of increasing the viscosity of the ink and reducing the flow after coating. ^R24 is preferably a branched alkylene group in terms of lower viscosity of the ink and stable ejection properties during inkjet coating. ^R24 is preferably a cyclic alkylene group in terms of lower ink viscosity and stable ejection properties during inkjet coating.

R ²⁵ and R ²⁶ as the alkyl group may be the same or different from each other. In addition, R ²⁵ and R ²⁶ may be linear, branched, or cyclic. R ²⁵ and R ²⁶ are preferably straight-chain alkyl groups in that the viscosity of the ink increases and the flow after coating can be reduced. R ²⁵ and R ²⁶ are preferably branched alkyl groups in terms of lowering the viscosity of the ink and stabilizing the ejectability during inkjet coating. R ²⁵ and R ²⁶ are preferably cyclic alkyl groups in terms of lower viscosity of the ink and stable dischargeability during inkjet coating.

The compound represented by the formula (9-1) is preferably an aliphatic dicarboxylic acid ester containing a cyclic structure in terms of easily dissolving a solute and making it easy to prepare a high-concentration ink.

The composition for an organic electroluminescence device of the present invention preferably contains a compound represented by the following formula (9-2) as an aliphatic carboxylic acid ester having a ketone group.

[chem 23]

[In the formula, R ²⁷ represents an alkylene group. R ²⁸ and R ²⁹ each independently represent an alkyl group. R ²⁷ and R ²⁸ , or R ²⁷ and R ²⁹ may be bonded to each other to form a ring. ]

R ²⁷ is preferably an alkylene group having 1 to 20 carbons, more preferably an alkylene group having 2 to 12 carbons, since it has moderate volatility as a solvent. R ²⁸ and R ²⁹ are each independently preferably an alkyl group having 1 to 20 carbons, more preferably an alkyl group having 1 to 6 carbons, in terms of moderate volatility as a solvent.

R ²⁷ which is an alkylene group may be any of linear, branched, or cyclic. ^R27 is preferably a straight-chain alkylene group in terms of increasing the viscosity of the ink and reducing the flow after coating. ^R27 is preferably a branched alkylene group in terms of lower viscosity of the ink and stable ejection properties during inkjet coating. R ²⁷ is preferably a cyclic alkylene group in terms of lower viscosity of the ink and stable dischargeability during inkjet coating.

R ²⁸ and R ²⁹ as the alkyl group may be the same or different from each other. In addition, R ²⁸ and R ²⁹ may be linear, branched, or cyclic. R ²⁸ and R ²⁹ are preferably straight-chain alkyl groups in that the viscosity of the ink increases and the flow after coating can be reduced. R ²⁸ and R ²⁹ are preferably branched alkyl groups in terms of lowering the viscosity of the ink and stabilizing the ejectability during inkjet coating. R ²⁸ and R ²⁹ are preferably cyclic alkyl groups in terms of lower viscosity of the ink and stable dischargeability during inkjet coating.

The compound represented by the formula (9-2) is preferably an aliphatic carboxylic acid ester having a cyclic structure and having a ketone group in terms of easily dissolving a solute and making it easy to prepare a high-concentration ink.

These aliphatic ester solvents having two or more carbonyl groups may be used alone or in any combination and ratio.

＜Aromatic diester solvent＞ The aromatic diester solvent is preferable in that it can effectively suppress the change of the liquid physical properties of the ink due to the structural change caused by the oxidation of the phenol derivative. An aromatic diester solvent is also preferable in that it can easily dissolve a solute.

The composition for an organic electroluminescence device of the present invention preferably contains a compound represented by the following formula (9-3) as an aromatic diester solvent.

[chem 24]

[In the formula, Ar ³¹ represents an aryl group, and R ^30a and R ^30b independently represent an alkyl group. R ^30a and Ar ³¹ may be bonded to each other to form a ring. ]

Ar ³¹ is preferably a phenylene group or a naphthalenediyl group, and more preferably a phenylene group, since it has moderate volatility as a solvent. Ar ³¹ is preferably an ortho-phenylene group or a meta-phenylene group, and more preferably a meta-phenylene group, in terms of lowering the viscosity of the ink and stabilizing the ejection property at the time of inkjet coating.

R ^30a and R ^30b are preferably an alkyl group having 1 to 20 carbons, more preferably an alkyl group having 1 to 6 carbons, in terms of moderate volatility as a solvent.

R ^30a and R ^30b as the alkyl group may be the same or different from each other. In addition, R ^30a and R ^30b may be linear, branched, or cyclic. R ^30a and R ^30b are preferably straight-chain alkyl groups in terms of increasing ink viscosity and reducing fluidity after coating. R ^30a and R ^30b are preferably branched alkyl groups in terms of lower viscosity of the ink and stable dischargeability during inkjet coating. R ^30a and R ^30b are preferably cyclic alkyl groups in terms of lower viscosity of the ink and stable dischargeability during inkjet coating. R ^30a and R ^30b are preferably an alkyl group containing a cyclic structure in terms of easily dissolving a solute and making it easy to prepare a high-concentration ink.

One of these aromatic diester solvents may be used alone, or two or more of them may be used in arbitrary combinations and ratios.

In addition, the composition for an organic electroluminescent device of the present invention may contain one or two or more of the above-mentioned aliphatic ester solvents having two or more carbonyl groups and one or two or more of the above-mentioned aromatic diesters in any combination and ratio. solvent.

＜Other solvents＞ The composition for an organic electroluminescence device of the present invention may contain other solvents than the aliphatic ester solvent and the aromatic diester solvent having two or more carbonyl groups.

As other solvents, alkylated biphenyls, aromatic ethers, and aromatic monoesters are preferable in terms of having a moderate boiling point and easily dissolving a solute.

The alkylated biphenyl that can be contained in the composition for an organic electroluminescence device of the present invention as another solvent may be a monoalkylated biphenyl having one alkyl group or a dialkyl biphenyl having two alkyl groups. Biphenyls may be trialkylated biphenyls, tetraalkylated biphenyls, heptaalkylated biphenyls, hexaalkylated biphenyls, etc. which have three or more alkyl groups.

In terms of low boiling point and high volatility, monoalkylated biphenyl or dialkylated biphenyl is preferred, and monoalkylated biphenyl is more preferred. Dialkylated biphenyl and trialkylated biphenyl are preferable, and trialkylated biphenyl is more preferable in terms of a high melting point and little fear of solidification of the composition when the composition is left at a low temperature. Dialkylated biphenyl is preferable in terms of having moderate boiling point and melting point.

Monoalkylated biphenyl is represented by the following formula (4).

[chem 25]

[In the formula, R ³¹ represents an alkyl group which may have a substituent. ]

^R31 as an alkyl group to be substituted in biphenyl is preferably an alkyl group having 1 to 12 carbon atoms, and examples thereof include methyl, ethyl, propyl, isopropyl, butyl, and isobutyl , Second butyl, third butyl, pentyl, isopentyl, hexyl, cyclohexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl. Among these, a methyl group, an ethyl group, a propyl group, and an isopropyl group are particularly preferable at the point that a boiling point is low and high volatility can be ensured. R ³¹ may have a phenyl group as a substituent, and in this case, the alkyl group having a substituent is preferably a benzyl group or a 2-phenylethyl group.

Examples of monoalkylated biphenyl include: 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, 2-ethylbiphenyl, 3-ethylbiphenyl, 4-ethylbiphenyl Biphenyl, 2-propylbiphenyl, 3-propylbiphenyl, 4-propylbiphenyl, 2-isopropylbiphenyl, 3-isopropylbiphenyl, 4-isopropylbiphenyl, 2 -Butylbiphenyl, 3-butylbiphenyl, 4-butylbiphenyl, 4-cyclohexylbiphenyl and the like.

Dialkylated biphenyl is represented by the following formula (4-1) or formula (4-2).

[chem 26]

[In the formula, R ³² to R ³⁵ each independently represent an alkyl group which may have a substituent. ]

Preferred examples of R ³² to R ³⁵ are the same as those of R ³¹ .

Examples of dialkylated biphenyls include: 2,3-dimethylbiphenyl, 3,4-dimethylbiphenyl, 3,3'-dimethylbiphenyl, 2,4-diethyl Biphenyl, 2,3'-diethylbiphenyl, 3,4'-diethylbiphenyl, 2,2'-dipropylbiphenyl, 2,4-dipropylbiphenyl, 2,4' -Dipropylbiphenyl, 3,4-diisopropylbiphenyl, 3,4'-diisopropylbiphenyl, 3,5-diisopropylbiphenyl, 3,3'-butylbiphenyl , 3,4'-butyl biphenyl, 4,4'-butyl biphenyl, etc.

Trialkylated biphenyl is represented by the following formula (4-3) or formula (4-4).

[chem 27]

[In the formula, R ³⁶ to R ⁴¹ each independently represent an alkyl group which may have a substituent. ]

Preferred examples of R ³² to R ³⁵ are the same as those of R ³¹ .

Examples of trialkylated biphenyls include 2,3,4-trimethylbiphenyl, 2,3,3'-trimethylbiphenyl, 3,3',4-trimethylbiphenyl, 2,4,4'-triethylbiphenyl, 3,4,5-triethylbiphenyl, 3,4',5-triethylbiphenyl, 2,2',4-tripropylbiphenyl , 2,4,5-dipropylbiphenyl, 2,3,4'-tripropylbiphenyl, 2,3',4-triisopropylbiphenyl, 2,3',5-triisopropylbiphenyl Biphenyl, 3,4,4'-triisopropylbiphenyl, etc.

One of these alkylated biphenyls may be used alone, or two or more of them may be used in arbitrary combinations and ratios.

The aromatic ether that can be contained in the composition for an organic electroluminescence device of the present invention as another solvent is preferably an alkane optionally having an alkyl group represented by the following formula (5) in terms of having high solubility. Oxybenzene.

[chem 28]

[In the formula, i represents an integer of 0-5. R ⁵¹ and R ⁵² each independently represent an alkyl group which may have a substituent. ]

In terms of low boiling point and high volatility, i is preferably an integer of 0 to 3, more preferably 0 or 1.

R ⁵¹ and R ⁵² are preferably an alkyl group having 1 to 12 carbon atoms. Examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, second butyl, Tertiary butyl, pentyl, isopentyl, hexyl, cyclohexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl. R ⁵¹ and R ⁵² may have a phenyl group as a substituent, and in this case, the alkyl group having a substituent is preferably a benzyl group or a 2-phenylethyl group.

The aromatic ether that can be contained in the composition for an organic electroluminescent device of the present invention as another solvent is preferably the following formula (5-1) in terms of having a high boiling point and being suitable for large-area coating The indicated phenoxybenzene may have an alkyl group.

[chem 29]

[In the formula, j and k represent integers of 0-5. R ⁵³ and R ⁵⁴ each independently represent an alkyl group which may have a substituent. ]

j and k are preferably an integer of 0 to 2, more preferably 0 or 1, in terms of low boiling point and high volatility.

R ⁵³ and R ⁵⁴ are preferably an alkyl group having 1 to 12 carbons. Examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, second butyl, Tertiary butyl, pentyl, isopentyl, hexyl, cyclohexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl. R ⁵³ and R ⁵⁴ may have a phenyl group as a substituent, and in this case, the alkyl group having a substituent is preferably benzyl or 2-phenylethyl.

The aromatic monoester that can be contained in the composition for an organic electroluminescence device of the present invention as another solvent is preferably a benzoic acid monoester that may have an alkyl group represented by the following formula (6).

[chem 30]

[In the formula, q represents an integer of 0-5. R ⁵⁵ and R ⁵⁶ each independently represent an alkyl group which may have a substituent. ]

q is preferably an integer of 0 to 2, more preferably 0 or 1, in terms of low boiling point and high volatility.

R ⁵⁵ and R ⁵⁶ are preferably an alkyl group having 1 to 12 carbons. Examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, second butyl, Tertiary butyl, pentyl, isopentyl, hexyl, cyclohexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl. R ⁵⁵ and R ⁵⁶ may have a phenyl group as a substituent. In this case, the alkyl group having a substituent is preferably benzyl or 2-phenylethyl.

One of these aromatic ethers and/or aromatic monoesters may be used alone, or two or more of them may be used in arbitrary combinations and ratios. That is, only one kind of aromatic ether may be used, only one kind of aromatic monoester may be used, and one kind or two kinds or more of aromatic ethers and one kind or two kinds or more of aromatic monoesters may be used in arbitrary combinations and ratios.

In the composition for an organic electroluminescence device of the present invention, as other solvents other than the aliphatic ester solvent and the aromatic diester solvent having two or more carbonyl groups, other than the above-mentioned alkylated biphenyl, aromatic ether , Other solvents other than aromatic monoesters.

Examples of preferable solvents other than alkylated biphenyls, aromatic ethers, and aromatic monoesters include n-decane, cyclohexane, ethylcyclohexane, decahydronaphthalene, and bicyclohexane Alkanes such as toluene, xylene, mesitylene, cyclohexylbenzene (phenylcyclohexane), tetrahydronaphthalene and other aromatic hydrocarbons; chlorobenzene, dichlorobenzene, trichlorobenzene and other halogenated aromatic hydrocarbons; Cyclohexanone, cyclooctanone, fenchone and other alicyclic ketones; cyclohexanol and cyclooctanol and other alicyclic alcohols; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA) class etc.

One of these other solvents may be used alone, or two or more of them may be used in any combination and ratio.

＜Boiling point of solvent＞ The boiling point of the solvent is usually above 80°C, preferably above 100°C, more preferably above 150°C, particularly preferably above 200°C, and usually below 350°C, preferably below 320°C, more preferably below 300°C . If the boiling point is lower than this range, the stability of the film may decrease due to evaporation of the solvent from the composition during wet film formation.

[Content of each ingredient] When the composition for an organic electroluminescent device of the present invention contains a light-emitting material as a functional material, the content (concentration) of the light-emitting material in the composition for an organic electroluminescent device of the present invention is preferably 0.05% by mass or more, more preferably Preferably, it is 0.1 mass % or more, More preferably, it is 0.2 mass % or more, More preferably, it is 8.0 mass % or less, More preferably, it is 4.0 mass % or less, More preferably, it is 2.0 mass % or less. When the concentration of the luminescent material is not less than the above lower limit, a layer containing a sufficient luminescent material can be formed. If the concentration of the luminescent material is below the above upper limit, the dissolved luminescent material will not be precipitated and it will be easy to maintain a uniform state.

When the composition for an organic electroluminescent device of the present invention contains a charge-transporting material as a functional material, the content (concentration) of the charge-transporting material in the composition for an organic electroluminescent device of the present invention is preferably 0.1 mass % or more, more preferably at least 0.2 mass %, more preferably at least 0.4 mass %, and preferably at most 16 mass %, more preferably at most 8.0 mass %, further preferably at most 4.0 mass %. When the concentration of the charge-transporting material is more than the above lower limit, a layer containing a sufficient charge-transporting material can be formed. When the concentration of the charge-transporting material is not more than the above upper limit, the dissolved charge-transporting material is not precipitated, and a uniform state is easily maintained.

When the composition for an organic electroluminescent device of the present invention contains a light-emitting material and a charge-transporting material as functional materials, the total content (concentration) of these in the composition for an organic electroluminescent device of the present invention is preferably 0.1 Mass % or more, more preferably 0.2 mass % or more, still more preferably 0.4 mass % or more, and preferably 16 mass % or less, more preferably 8.0 mass % or less, still more preferably 4.0 mass % or less. A layer containing sufficient functional materials can be formed as the total concentration of functional materials is more than the said minimum. If the total concentration of functional materials is below the said upper limit, it will become easy to maintain a uniform state without depositing the dissolved functional materials.

The quality ratio of the content of the luminescent material and the charge-transporting material is preferably in the range of luminescent material:charge-transporting material=1:0.8-16, especially the range of 1:1.2-8.0, especially preferably 1:1.6-4.0 scope. When the mass ratio of the content of the light-emitting material to the charge-transporting material is within the above-mentioned range, an organic electroluminescence device having a low driving voltage and high luminous efficiency can be produced.

The content (concentration) of the phenol derivative as the compound represented by the formula (1) contained in the composition for an organic electroluminescence device of the present invention is preferably 5 mass ppm or more, more preferably 10 mass ppm or more , and more preferably at least 20 mass ppm, and more preferably at most 4000 mass ppm, more preferably at most 2000 mass ppm, still more preferably at most 1000 mass ppm. When the density|concentration of a phenol derivative is more than the said minimum, the deterioration suppression effect of a phenol derivative with respect to a functional material can fully be acquired. When the density|concentration of a phenol derivative is below the said upper limit, when forming a light emitting layer, a phenol derivative and its oxide are easily removed together with a solvent.

The content of the aliphatic ester solvent and/or the aromatic diester solvent having two or more carbonyl groups contained in the composition for an organic electroluminescence device of the present invention is preferably at least 2.0% by mass, more preferably at least 5.0% by mass , and more preferably 10% by mass or more. When the content of the aliphatic ester solvent and/or the aromatic diester solvent having two or more carbonyl groups is more than the above lower limit, changes in liquid physical properties during long-term storage of the ink can be reduced.

In addition to the aliphatic ester solvent and/or aromatic diester solvent having two or more carbonyl groups, the composition for an organic electroluminescence device of the present invention may further include the other solvents, but in the organic electroluminescence device of the present invention, When the composition for an electroluminescent element contains other solvents, based on the fact that the effects of the present invention brought about by using an aliphatic ester solvent and/or an aromatic diester solvent having two or more carbonyl groups are more effectively obtained, The content of other solvents in all solvents is preferably at most 95% by mass, especially preferably at most 85% by mass.

The total content of the solvents in the composition for organic electroluminescent elements of the present invention is preferably large in terms of ease of film formation due to low viscosity, and on the other hand, it is easy to form a thick film In terms of aspect, preferably less. The total content of solvents in the composition for an organic electroluminescent device of the present invention is preferably at least 1% by mass, more preferably at least 10% by mass, particularly preferably at least 50% by mass, and is preferably at most 99.99% by mass, and more preferably at least 99.99% by mass. Preferably, it is 99.9 mass % or less, and especially preferably, it is 99 mass % or less.

[use] The composition for an organic electroluminescence device of the present invention is particularly suitable as a composition for forming a light-emitting layer containing a light-emitting material and a charge-transporting material as functional materials.

〔Organic electroluminescence element〕 The organic electroluminescent device of the present invention has a light emitting layer formed using the composition for an organic electroluminescent device of the present invention.

The organic electroluminescent element of the present invention preferably has at least an anode and a cathode on the substrate and at least one organic layer between the anode and the cathode, at least one of the organic layers using the organic electric field of the present invention Composition for light-emitting device and light-emitting layer formed by wet film-forming method.

In the present invention, the so-called wet film-forming method refers to methods such as spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, inkjet coating, etc. method, nozzle printing method, screen printing method, gravure printing method, flexographic printing method, etc. to form a film by wet method as a film forming method, that is, a coating method, and dry the film formed by these methods method for film formation.

FIG. 1 is a schematic cross-sectional view showing a preferred structural example of an organic electroluminescent device 10 of the present invention. In Fig. 1, the symbol 1 represents the substrate, the symbol 2 represents the anode, the symbol 3 represents the hole injection layer, the symbol 4 represents the hole transport layer, the symbol 5 represents the light-emitting layer, the symbol 6 represents the hole blocking layer, and the symbol 7 represents the electron transport layer , Symbol 8 denotes an electron injection layer, and Symbol 9 denotes a cathode.

The materials used in these structures can be known materials and are not particularly limited. Representative materials and manufacturing methods for each layer are described below as examples. When citing gazettes, papers, etc., the corresponding content can be appropriately applied and applied within the scope of common knowledge of those skilled in the art.

[Substrate 1] The substrate 1 serves as a support for the organic electroluminescence element, and generally uses a quartz or glass plate, a metal plate or metal foil, a plastic film or sheet, and the like. Among these, a glass plate, or a plate of transparent synthetic resin such as polyester, polymethacrylate, polycarbonate, and polyester is preferable. The substrate 1 is preferably made of a material with high gas barrier properties from the viewpoint that degradation of the organic electroluminescence element due to external air is less likely to occur. Therefore, especially when a material with low gas barrier properties such as a synthetic resin substrate is used, it is preferable to provide a dense silicon oxide film or the like on at least one side of the substrate 1 to improve the gas barrier properties.

[Anode 2] The anode 2 has the function of injecting holes into the layer on the light emitting layer side.

The anode 2 usually includes: metals such as aluminum, gold, silver, nickel, palladium, platinum; metal oxides such as indium and/or tin oxides; metal halides such as copper iodide; carbon black or poly(3-methylthiophene) , polypyrrole, polyaniline and other conductive polymers.

Formation of the anode 2 is generally performed by dry methods such as sputtering and vacuum deposition. In the case of forming the anode 2 using metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., the anode 2 can also be dispersed in an appropriate binder resin solution and spread onto the substrate to form. In the case of conductive polymers, it is also possible to form a thin film directly on the substrate by electrolytic polymerization, or to coat the conductive polymer on the substrate to form the anode 2 (Applied Physics Letters, Appl. Phys. Lett .), Vol. 60, p. 2711, 1992).

The anode 2 usually has a single-layer structure, but a laminated structure can also be appropriately used. In the case that the anode 2 has a laminated structure, different conductive materials can also be laminated on the anode of the first layer.

The thickness of the anode 2 may be determined according to the desired transparency, material, and the like. Especially when high transparency is required, it is preferable to make the visible light transmittance into the thickness of 60% or more, and it is more preferable to make it into the thickness of 80% or more. The thickness of the anode 2 is usually not less than 5 nm, preferably not less than 10 nm, and usually not more than 1000 nm, preferably not more than 500 nm. When transparency is not required, the thickness of the anode 2 may be any thickness according to required strength, etc. In this case, the anode 2 may have the same thickness as the substrate 1 .

When forming a film on the surface of the anode 2, it is preferable to perform treatments such as ultraviolet light+ozone, oxygen plasma, and argon plasma before film formation, thereby removing impurities on the anode and adjusting its ionization potential to make holes Injectability improved.

[Hole injection layer 3] The layer that assumes the function of transporting holes from the anode 2 side to the light emitting layer 5 side is generally called a hole injection transport layer or a hole transport layer. When there are two or more layers that perform the function of transporting holes from the anode 2 side to the light emitting layer 5 side, the layer closer to the anode 2 side may be referred to as a hole injection layer 3 . From the viewpoint of enhancing the function of transporting holes from the anode 2 to the light emitting layer 5 side, it is preferable to use the hole injection layer 3 . In the case of using the hole injection layer 3 , the hole injection layer 3 is usually formed on the anode 2 .

The film thickness of the hole injection layer 3 is usually not less than 1 nm, preferably not less than 5 nm, and usually not more than 1000 nm, preferably not more than 500 nm.

The method for forming the hole injection layer 3 may be a vacuum evaporation method or a wet film-forming method. It is preferably formed by a wet film-forming method in terms of excellent film-forming properties.

The hole injection layer 3 preferably contains a hole-transporting compound, more preferably contains a hole-transporting compound and an electron-accepting compound. Furthermore, it is preferable to include a cationic radical compound in the hole injection layer 3 , and it is particularly preferable to include a cationic radical compound and a hole transporting compound.

(Hole transporting compound) The composition for forming a hole injection layer generally contains a hole transporting compound to be the hole injection layer 3 . In addition, in the case of a wet film-forming method, a solvent is usually further contained. The hole-transporting compound is preferably one that has high hole-transporting properties and can efficiently transport injected holes. Therefore, it is preferable that the hole-transporting compound has a high hole mobility, and an impurity that is less likely to become a trap during production or use. In addition, the hole-transporting compound is preferably excellent in stability, low in ionization potential, and high in transparency to visible light. Especially when the hole injection layer 3 is in contact with the light-emitting layer 5, 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 so as not to reduce the luminous efficiency. By.

The hole transport compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of inhibition of charge injection from the anode 2 to the hole injection layer 3 . Examples of hole transporting compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, Compounds formed by linking grade amines, hydrazone compounds, silazane compounds, quinacridone compounds, etc.

Among the exemplified compounds, aromatic amine compounds are preferable, and aromatic tertiary amine compounds are particularly preferable in terms of amorphous properties and visible light transmittance. Here, the aromatic tertiary amine compound refers to 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, and it is preferable to use a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less in terms of easily obtaining uniform light emission due to the surface smoothing effect (repeated A polymeric compound in which units are connected).

As a preferable example of an aromatic tertiary amine high molecular compound, the high molecular compound etc. which have a repeating unit represented by following formula (I) are mentioned.

[chem 31]

[In the formula, Ar ¹ and Ar ² each independently represent an aromatic group which may have a substituent or a heteroaromatic group which may have a substituent. Ar ³ to Ar ⁵ each independently represent an aromatic group which may have a substituent or a heteroaromatic group which may have a substituent. Q represents a linking group selected from the following linking group group. Among Ar ¹ to Ar ⁵ , two groups bonded to the same N atom may bond to each other to form a ring. ]

Linking groups are shown below.

[chem 32]

[In each of the formulas, Ar ⁶ to Ar ¹⁶ each independently represent an aromatic group which may have a substituent or a heteroaromatic group which may have a substituent. R ^a to R ^b each independently represent a hydrogen atom or an arbitrary substituent. ]

The aromatic and heteroaromatic groups of Ar ¹ to Ar ¹⁶ are preferably derived from benzene rings, naphthalene rings, and phenanthrene rings in terms of solubility, heat resistance, and hole injection transport properties of polymer compounds. , a thiophene ring, and a pyridine ring, and more preferably a group derived from a benzene ring or a naphthalene ring.

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by formula (I) include compounds described in International Publication No. 2005/089024, and the like.

(electron-accepting compound) Since the electrical conductivity of the hole injection layer 3 can be increased by oxidation of the hole transport compound, the hole injection layer 3 preferably contains an electron accepting compound.

The electron-accepting compound is preferably a compound having oxidation ability and the ability to accept a single electron from the hole-transporting compound. Specifically, the electron-accepting compound is preferably a compound having an electron affinity of 4 eV or higher, more preferably a compound having an electron affinity of 5 eV or higher.

Examples of such electron-accepting compounds include those selected from triaryl boron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. One or two or more compounds in a group, etc. Specifically, onium salts with organic groups substituted, such as 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl) borate and triphenylmazonium tetrafluoroborate ( International Publication No. 2005/089024); iron (III) chloride (Japanese Patent Laid-Open Publication No. 11-251067), high-valence inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; three Aromatic boron compounds such as (pentafluorophenyl)borane (Japanese Patent Laid-Open No. 2003-31365); fullerene derivatives and iodine, etc.

(cationic radical compound) The cationic radical compound is preferably an ionic compound containing a cationic radical, which is a chemical species from which one electron has been removed from the hole transport compound, and a counter anion. Among them, 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 cationic radical is preferably a chemical species from which one electron has been removed from the compound described above as the hole-transporting compound. From the viewpoints of amorphousness, visible light transmittance, heat resistance, solubility, and the like, chemical species from which one electron has been removed from a compound preferable as a hole-transporting compound are preferable.

The cationic radical compound can be produced by mixing the hole-transporting compound and the electron-accepting compound. That is, by mixing the hole-transporting compound and the electron-accepting compound, electrons move from the hole-transporting compound to the electron-accepting compound, and a cation radical and a counteranion including the hole-transporting compound are generated. Cationic ionic compounds.

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), PEDOT/PSS) (Advanced Materials, Adv.Mater .), 2000, volume 12, page 481) or aniline green (emeraldine) hydrochloride (The Journal of Chemical Physics, J. Phys. Chem., 1990, volume 94, page 7716), etc. Cationic radical compounds derived from polymer compounds can also be produced by oxidative polymerization (dehydropolymerization). The oxidative polymerization mentioned here is to chemically or electrochemically oxidize a monomer in an acidic solution using peroxodisulfate or the like. In the case of this oxidative polymerization (dehydropolymerization), the monomer is polymerized by oxidation, and an anion derived from an acidic solution is used as a counter anion to generate a cation from which one electron is removed from the repeating unit of the polymer. free radicals.

(Formation of hole injection layer 3 by wet film formation method) In the case of forming the hole injection layer 3 by a wet film-forming method, the material for forming the hole injection layer 3 is usually mixed with a soluble solvent (solvent for the hole injection layer) to prepare a film-forming composition (a composition for forming a hole injection layer), and the composition for forming a hole injection layer is formed on a layer corresponding to a lower layer of the hole injection layer 3 (usually the anode 2) by a wet film-forming method , and allowed to dry, thereby forming. Drying of the formed film can be carried out in the same manner as the drying method in the formation of the light-emitting layer 5 by the wet film-forming method described later.

The concentration of the hole transport 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 it is preferably low in terms of uniformity of film thickness. It is preferably high in terms of the fact that defects are less likely to be generated in the hole injection layer 3 . Specifically, the concentration of the hole transporting compound in the composition for forming a hole injection layer is preferably at least 0.01% by mass, more preferably at least 0.1% by mass, particularly preferably at least 0.5% by mass, and more preferably at least 0.5% by mass. 70 mass % or less, More preferably, it is 60 mass % or less, Most preferably, it is 50 mass % or less.

Examples of the solvent include ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, amide-based 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, 2 , 4-dimethylanisole and other aromatic ethers.

Examples of the ester-based solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate. Examples of aromatic hydrocarbon solvents include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3,4-tetramethylbenzene, and 1,4-diisopropylbenzene , Methylnaphthalene, etc.

Examples of the amide-based solvent include N,N-dimethylformamide, N,N-dimethylacetamide, and the like. Other than these, dimethylsulfone and the like can also be used.

The formation of the hole injection layer 3 utilizing the wet film-forming method is usually by applying the composition for forming the hole injection layer to a layer corresponding to the lower layer of the hole injection layer 3 (usually anode 2) and dry to carry out. The hole injection layer 3 is usually dried by heating or drying under reduced pressure after film formation.

(Formation of Hole Injection Layer 3 by Vacuum Evaporation Method) In the case of forming hole injection layer 3 by vacuum evaporation method, the constituent material of hole injection layer 3 (the hole transport One or two or more kinds of compounds, electron-accepting compounds, etc.) are put into the crucible set in the vacuum container (in the case of using more than two kinds of materials, they are usually put into different crucibles respectively), and use After the vacuum pump exhausts the vacuum container to about 10 ^-4 Pa, the crucible is heated (in the case of using two or more materials, the crucible is usually heated separately), and the evaporation rate of the material in the crucible is controlled. This is evaporated (in the case of using two or more materials, the amount of evaporation is usually controlled independently for evaporation), and a hole injection layer 3 is formed on the anode 2 on the substrate placed facing the crucible. When two or more materials are used, the mixture of these materials may be put into a crucible, heated and evaporated to form the hole injection layer 3 .

The degree of vacuum during vapor deposition is not particularly limited as long as the effect of the present invention is not significantly impaired, and is usually 0.1×10 ^-6 Torr (Torr) (0.13×10 ^-4 Pa) or more and 9.0×10 ^-6 Torr ( 12.0×10 ^-4 Pa) or less. The vapor deposition rate is not limited as long as the effect of the present invention is not significantly impaired, and is usually not less than 0.1 Å/sec and not more than 5.0 Å/sec. The film formation 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 and 50° C. or lower.

[Hole transport layer 4] The hole transport layer 4 is a layer that functions to transport holes from the anode 2 side to the light emitting layer 5 side. The hole transport layer 4 is not an essential layer for the organic electroluminescent device of the present invention, but it is preferably provided in terms of enhancing the function of transporting holes from the anode 2 to the light emitting layer 5 . In the case of providing the hole transport layer 4 , the hole transport layer 4 is usually formed between the anode 2 and the light emitting layer 5 . In the presence of the hole injection layer 3 , the hole transport layer 4 is formed between the hole injection layer 3 and the light emitting layer 5 .

The film thickness of the hole transport layer 4 is usually not less than 5 nm, preferably not less than 10 nm, and usually not more than 300 nm, preferably not more than 100 nm.

The method for forming the hole transport layer 4 may be a vacuum evaporation method or a wet film-forming method. It is preferably formed by a wet film-forming method in terms of excellent film-forming properties.

The hole transport layer 4 usually contains a hole transport compound that becomes the hole transport layer 4 . As the hole-transporting compound contained in the hole-transporting layer 4, in particular, compounds containing two compounds represented by 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl can be cited. Aromatic diamines with more than two tertiary amines and two or more condensed aromatic rings substituted on the nitrogen atom (Japanese Patent Laid-Open No. 5-234681); 4,4',4''-three ( Aromatic amine compounds with a starburst structure such as 1-naphthylphenylamino)triphenylamine (J. Lumin., Vol. 72-74, p. 985, 1997); including triphenylamine Tetrameric aromatic amine compounds (Chem. Commun., p. 2175, 1996); 2,2',7,7'-tetra-(diphenylamino)-9,9' - Spiro compounds such as spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997); carbazole derivatives such as 4,4'-N,N'-dicarbazole biphenyl, etc. In addition, for example, polyvinylcarbazole, polyvinyltriphenylamine (Japanese Patent Application Laid-Open No. 7-53953 ), polyarylether ether containing tetraphenylbenzidine (Advanced Technology with polymers (Polymers for Advanced Technologies, Polym. Adv. Tech.), Vol. 7, p. 33, 1996) and the like.

(Formation of hole transport layer 4 by wet film-forming method) In the case of forming the hole transport layer 4 by a wet film-forming method, it is generally performed in the same manner as when forming the hole injection layer 3 by a wet film-forming method, and the composition for forming the hole transport layer is used. material instead of the composition for forming the hole injection layer.

In the case of forming the hole transport layer 4 by a wet film-forming method, the composition for forming a hole transport layer usually further contains a solvent. As the solvent used in the composition for forming a hole transport layer, the same solvent as that used in the composition for forming a hole injection layer can be used. The concentration of the hole transporting compound in the composition for forming a hole transporting layer can be set within the same range as the concentration of the hole transporting compound in the composition for forming a hole injection layer.

(Formation of hole transport layer 4 by vacuum evaporation method) Regarding the case of forming the hole transport layer 4 by the vacuum evaporation method, it can generally be carried out in the same manner as the above-mentioned formation of the hole injection layer 3 by the vacuum evaporation method, and the constituent material of the hole transport layer 4 can be used. It is formed instead of the constituent material of the hole injection layer 3 . Film formation conditions such as vacuum degree, deposition rate, and temperature during vapor deposition can be formed under the same conditions as those during vacuum vapor deposition of the hole injection layer 3 described above.

[luminous layer 5] The light-emitting layer 5 is a layer that functions to emit light by being excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 when an electric field is applied between a pair of electrodes. The light-emitting layer 5 is a layer formed between the anode 2 and the cathode 9, and when the hole injection layer 3 exists on the anode 2, the light-emitting layer 5 is formed between the hole injection layer 3 and the cathode 9, when the anode When the hole transport layer 4 is present on the 2, the light emitting layer 5 is formed between the hole transport layer 4 and the cathode 9.

As long as the effect of the present invention is not significantly impaired, the film thickness of the light emitting layer 5 is arbitrary, but it is preferably thicker in terms of less likely to cause defects in the film, and on the other hand, it is easy to set it to a low driving voltage. On the other hand, it is preferably thin. Therefore, the film thickness of the light-emitting layer 5 is preferably not less than 3 nm, more preferably not less than 5 nm, and usually preferably not more than 200 nm, and more preferably not more than 100 nm.

The light-emitting layer 5 contains at least a material having light-emitting properties (light-emitting material), and preferably a material having charge-transporting properties (charge-transporting material).

The general luminescent material and the method of forming the luminescent layer will be described below, but in the organic electroluminescent device of the present invention, the luminescent layer is preferably formed by wet-forming the composition for the organic electroluminescent device of the present invention. membrane method to form. In addition, as the luminescent material, an iridium complex that is an organometallic complex having iridium as a central element is preferable, but other luminescent materials can also be appropriately used. Hereinafter, other light-emitting materials other than the iridium complex compound will be described in detail.

(Luminescent material) The light-emitting material is not particularly limited as long as it emits light at a desired light-emitting wavelength and does not impair the effects of the present invention, and known light-emitting materials can be used. The luminescent material may be a fluorescent luminescent material or a phosphorescent luminescent material, but is preferably a material with good luminous efficiency, and is preferably a phosphorescent luminescent material from the viewpoint of internal quantum efficiency.

Examples of the fluorescent light emitting material include the following materials. As fluorescent light-emitting materials (blue fluorescent light-emitting materials) that provide blue light emission, for example, naphthalene, perylene, pyrene, anthracene, coumarin, p-bis(2-phenylvinyl)benzene and the some derivatives etc. Examples of fluorescent light-emitting materials (green fluorescent light-emitting materials) that give green light include quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al(C ₉ H ₆ NO) ₃ , and the like. Examples of fluorescent light-emitting materials (yellow fluorescent light-emitting materials) that give yellow light include rubrene, perimidone derivatives, and the like. As a fluorescent light-emitting material (red fluorescent light-emitting material) that provides red light emission, for example, DCM (4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyrene Base)-4H-pyran) series compounds, benzopyran derivatives, rose bengal derivatives, benzothioxanthene derivatives, azabenzothioxanthene, etc.

As the phosphorescent luminescent material, for example, it is possible to include Groups 7 to 10 selected from the long-period periodic table (hereinafter, when referred to as "periodic table", it refers to the long-period periodic table unless otherwise specified). Organometallic complexes of metals in Group 11, etc. As the metal selected from Groups 7 to 11 of the periodic table, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, gold, etc. are preferably mentioned.

As the ligand of organometallic complexes, (hetero)aryl pyridine ligands, (hetero)arylpyrazole ligands and other (hetero)aryl groups are preferably linked with pyridine, pyrazole, phenanthroline, etc. The resulting ligands are especially preferably phenylpyridine ligands and phenylpyrazole ligands. Here, (hetero)aryl means aryl or heteroaryl.

Specific examples of preferred phosphorescent materials include: tris(2-phenylpyridine)iridium, tris(2-phenylpyridine)ruthenium, tris(2-phenylpyridine)palladium, bis(2-phenylpyridine) Pyridine) platinum, tris(2-phenylpyridine) osmium, tris(2-phenylpyridine) rhenium and other phenylpyridine complexes and octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethylpalladium porphyrin Porphyrin complexes such as phyllin, octaphenylpalladium porphyrin, etc.

Examples of polymer-based luminescent materials include: poly(9,9-dioctylfluorene-2,7-diyl), poly[(9,9-dioctylfluorene-2,7-diyl)-co -(4,4'-(N-(4-Second-butylphenyl))diphenylamine)], poly[(9,9-dioctylfluorene-2,7-diyl)-co- (1,4-Benzo-2{2,1'-3}-triazole)] and other polyfluorene materials, poly[2-methoxy-5-(2-ethylhexyloxy)-1, 4-Styrene] and other polystyrene-based materials.

(charge-transporting material) The charge-transporting material is a material having positive charge (hole) or negative charge (electron) transport properties, and is not particularly limited as long as the effects of the present invention are not impaired, and known materials can be used. As the charge-transporting material, compounds previously used in the light-emitting layer 5 of the organic electroluminescent device can be used, and compounds used as a host material of the light-emitting layer 5 are particularly preferable.

Specific examples of charge-transporting materials include aromatic amine-based compounds, phthalocyanine-based compounds, porphyrin-based compounds, oligothiophene-based compounds, polythiophene-based compounds, benzylphenyl-based compounds, fluorenyl-based Compounds formed by linking tertiary amines, hydrazone-based compounds, silazane-based compounds, silylamine-based compounds, phosphoramide-based compounds, quinacridone-based compounds, etc. Exemplary compounds and the like. In addition, electron-transporting compounds such as anthracene-based compounds, pyrene-based compounds, carbazole-based compounds, pyridine-based compounds, phenanthroline-based compounds, oxadiazole-based compounds, and silacyclopentadiene-based compounds, etc. are also exemplified.

In addition, as a charge-transporting material, for example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl containing two or more three Aromatic diamines in which two or more condensed aromatic rings are substituted on the nitrogen atom (Japanese Patent Laid-Open Publication No. 5-234681); 4,4',4''-tri(1-naphthyl Aromatic amine compounds with a starburst structure such as phenylamino)triphenylamine (J. Lumin., Vol. 72-74, p. 985, 1997); tetramers containing triphenylamine (Chem. Commun., p. 2175, 1996); 2,2',7,7'-tetra-(diphenylamino)-9,9'-spiro Fluorene-based compounds such as difluorene (Synth. Metals, Vol. 91, p. 209, 1997); carbazole-based compounds such as 4,4'-N,N'-dicarbazole biphenyl, etc. as hole transport Compounds etc. are exemplified as the hole transporting compound of the layer 4 . In addition, 2-(4-biphenyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD), 2,5 -Oxadiazole compounds such as bis(1-naphthyl)-1,3,4-oxadiazole (BND); 2,5-bis(6'-(2',2''-bipyridyl)) -1,1-Dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy) and other silacyclopentadiene compounds; 4,7-diphenyl-1,10-phenanthroline ( BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproine) and other phenanthroline compounds, etc.

(Formation of light-emitting layer 5 by wet film-forming method) The method for forming the light-emitting layer 5 may be a vacuum evaporation method or a wet film-forming method, but a wet film-forming method is preferable in terms of excellent film-forming properties.

When forming the light-emitting layer 5 by a wet film-forming method, it is generally performed in the same manner as the case of forming the hole injection layer 3 by a wet film-forming method, and the material and the material used to form the light-emitting layer 5 are used. A composition for forming a light-emitting layer prepared by mixing a soluble solvent (solvent for a light-emitting layer) is formed instead of the composition for forming a hole injection layer. In the present invention, it is preferable to use the above-mentioned composition for an organic electroluminescence device of the present invention as the composition for forming a light-emitting layer.

As the solvent, for example, in addition to the ether solvents, ester solvents, aromatic hydrocarbon solvents, and amide solvents mentioned for the formation of the hole injection layer 3, alkane solvents, halogenated aromatic hydrocarbon solvents, etc. , Aliphatic alcohol-based solvents, alicyclic alcohol-based solvents, aliphatic ketone-based solvents, and alicyclic ketone-based solvents. Preferable solvents are exemplified as aliphatic ester solvents having two or more carbonyl groups, aromatic diester solvents, and other solvents contained in the composition for organic electroluminescent devices of the present invention.

The amount of the solvent used is arbitrary as long as the effects of the present invention are not significantly impaired. However, the total content of the light-emitting layer-forming composition is preferably large in terms of ease of film formation due to low viscosity, and preferably in the light of easy film formation with a thick film. few. As described above, the content of the solvent in the composition for forming a light-emitting layer is preferably at least 1% by mass, more preferably at least 10% by mass, particularly preferably at least 50% by mass, and is preferably at most 99.99% by mass, more preferably at most 99.99% by mass. It is 99.9 mass % or less, especially preferably 99 mass % or less.

As a method of removing the solvent after wet film formation, heating or reduced pressure can be employed. As the heating means used in the heating method, a clean oven and a hot plate are preferable in terms of uniformly supplying heat to the entire film. As long as the effect of the present invention is not significantly impaired, the heating temperature in the heating step is arbitrary, but in terms of shortening the drying time, the temperature is preferably high, and the material is less damaged. for low temperature. The upper limit of the heating temperature is usually 250°C or less, preferably 200°C or less, further preferably 150°C or less. The lower limit of the heating temperature is usually 30°C or higher, preferably 50°C or higher, further preferably 80°C or higher. A temperature exceeding the upper limit has higher heat resistance than a generally used charge-transporting material or phosphorescent material, and is not preferable because it may decompose or crystallize. Since it takes a long time to remove a solvent at the temperature below the said lower limit, it is unpreferable. The heating time in the heating step can be appropriately determined according to the boiling point or vapor pressure of the solvent in the light-emitting layer-forming composition, heat resistance of the material, and heating conditions.

(Formation of Light Emitting Layer 5 by Vacuum Evaporation Method) In the case of forming the light emitting layer 5 by vacuum evaporation method, the constituent materials of the light emitting layer 5 (the above-mentioned light emitting material, charge transport compound, etc.) Put one or more than two kinds of materials into the crucible set in the vacuum container (in the case of using more than two kinds of materials, usually put them into different crucibles respectively), and use the vacuum pump to exhaust the vacuum container to 10 After about ^-4 Pa, heat the crucible (in the case of using two or more materials, usually heat the crucible separately), and evaporate the material while controlling the evaporation amount in the crucible (in the case of using two or more materials) In the case of materials, the amount of evaporation is usually controlled independently to evaporate), and the light-emitting layer 5 is formed on the hole injection layer 3 or the hole transport layer 4 placed facing the crucible. When two or more materials are used, the mixture of these materials may be put into a crucible, heated and evaporated to form the light emitting layer 5 .

As long as the effect of the present invention is not significantly impaired, the degree of vacuum during vapor deposition is not limited, and is usually 0.1×10 ^-6 Torr (0.13×10 ^-4 Pa) or more and 9.0×10 ^-6 Torr (12.0×10 -4 Pa ^{) or} higher. ⁴ Pa) or less. The vapor deposition rate is not limited as long as the effect of the present invention is not significantly impaired, and is usually not less than 0.1 Å/sec and not more than 5.0 Å/sec. The film formation 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 and 50° C. or lower.

[Hole blocking layer 6] A hole blocking layer 6 may also be provided between the light emitting layer 5 and the electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole blocking layer 6 has the function of blocking the holes moving from the anode 2 from reaching the cathode 9 and the function of efficiently transporting electrons injected from the cathode 9 to the direction of the light emitting layer 5 . The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility and low hole mobility, the difference between the energy gap (HOMO and the lowest unoccupied molecular orbital (LUMO) ) is large, and the excited triplet energy level (T1) is high.

As the material of the hole blocking layer 6 satisfying this condition, for example, bis(2-methyl-8-quinolinol) (phenol) aluminum, bis(2-methyl-8-quinolinol) ( Triphenylsilanol) aluminum (bis (2-methyl-8-quinolinolato) (triphenyl silanolato) aluminum) and other mixed ligand complexes, bis (2-methyl-8-quinolinolato) aluminum-μ- Oxo-bis-(2-methyl-8-hydroxyquinoline) aluminum dinuclear metal complexes and other metal complexes, distyryl biphenyl derivatives and other styryl compounds (Japanese Patent Laying-Open Hei 11- 242996 bulletin), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole and other triazole derivatives (Japanese patent Kaihei No. 7-41759), phenanthroline derivatives such as bathocuproin (Japanese Patent Laid-Open No. 10-79297), etc. Furthermore, the compound having at least one pyridine ring substituted at positions 2, 4, and 6 described in International Publication No. 2005/022962 is also preferable as the material of the hole blocking layer 6 .

The method for forming the hole blocking layer 6 is not limited, and it can be formed in the same manner as the method for forming the light emitting layer 5 described above. As long as the effect of the present invention is not significantly impaired, the film thickness of the hole blocking layer 6 is arbitrary, but it is usually more than 0.3 nm, preferably more than 0.5 nm, and usually less than 100 nm, preferably less than 50 nm .

[Electron transport layer 7] For the purpose of further improving the current efficiency of the element, the electron transport layer 7 is disposed between the light emitting layer 5 or the hole element layer 6 and the electron injection layer 8 . The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode 9 to the light emitting layer 5 between electrodes to which an electric field is applied. The electron-transporting compound used in the electron-transporting layer 7 needs to be a compound that has high electron injection efficiency from the cathode 9 or the electron injection layer 8 , has high electron mobility, and can efficiently transport injected electrons.

Specific examples of electron-transporting compounds satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Application Laid-Open No. 59-194393 ), 10-hydroxybenzo[h]quinoline metal complexes, oxadiazole derivatives, distyryl biphenyl derivatives, silacyclopentadiene derivatives, 3-hydroxyflavone metal complexes , 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, tribenzimidazolylbenzene (US Patent No. 5645948), quinoxaline compounds (Japanese patent Kaihei No. 6-207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-tert-butyl-9,10-N,N'-dicyanoanthraquinonediimine, n Type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide, etc.

The film thickness of the electron transport layer 7 is usually not less than 1 nm, preferably not less than 5 nm, and usually not more than 300 nm, preferably not more than 100 nm. The electron transport layer 7 is formed by laminating on the light emitting layer 5 or the hole blocking layer 6 by a wet film-forming method or a vacuum deposition method similarly to the light emitting layer 5 . Usually a vacuum evaporation method is used.

[Electron injection layer 8] The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the electron transport layer 7 or the light emitting layer 5 . In order to perform electron injection efficiently, the material forming the electron injection layer 8 is preferably a metal with a low work function. As an example, an alkali metal such as sodium or cesium, an alkaline earth metal such as barium or calcium, or the like can be used. The film thickness of the electron injection layer 8 is preferably 0.1 nm to 5 nm.

Inserting LiF, MgF ₂ , Li ₂ O, Cs ₂ CO ₃ and other ultra-thin insulating films (with a film thickness of about 0.1 nm to 5 nm) at the interface between the cathode 9 and the electron transport layer 7 as the electron injection layer 8 also improves the performance of the element. Effective methods for efficiency (Appl. Phys. Lett., Vol. 70, pp. 152, 1997; Japanese Patent Laid-Open No. 10-74586; IEEE Transactions on Electronic Devices , IEEETrans. Electron. Devices), Volume 44, Page 1245, 1997; Society for Information Display (SID) 04 Abstract (Digest), Page 154). Furthermore, organic electron transport represented by nitrogen-containing heterocyclic compounds such as 4,7-diphenyl-1,10-phenanthroline or metal complexes such as aluminum complexes of 8-hydroxyquinoline The material is doped with alkali metals such as sodium, potassium, cesium, lithium, rubidium, etc. It is preferable since the excellent film quality which can improve both electron injection property and transport property is possible. The film thickness in this case is usually at least 5 nm, preferably at least 10 nm, and usually at most 200 nm, preferably at most 100 nm.

The electron injection layer 8 is formed by laminating on the light emitting layer 5 or the hole blocking layer 6 or the electron transport layer 7 on the light emitting layer 5 by wet film formation method or vacuum evaporation method similarly to the light emitting layer 5 . Details in the case of the wet film-forming method are the same as those in the case of the above-mentioned light-emitting layer 5 .

[Cathode 9] The cathode 9 plays a role of injecting electrons into a layer on the light emitting layer 5 side (the electron injection layer 8 or the light emitting layer 5 , etc.). As the material of the cathode 9, the material used for the above-mentioned anode 2 can be used, but it is preferable to use a metal with a low work function in terms of efficiently performing electron injection. As the metal having a low work function, for example, metals such as tin, magnesium, indium, calcium, aluminum, and silver, or alloys thereof, can be used. Specific examples include low work function alloy electrodes such as magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys.

In terms of device stability, it is preferable to laminate a metal layer having a high work function and stable to the atmosphere on the cathode 9 to protect the cathode 9 including a metal with a low work function. Examples of metals to be laminated include metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum. The film thickness of the cathode is usually the same as that of the anode 2 .

[other structural layers] Above, the device with the layered structure shown in FIG. 1 has been described as a center, but between the anode 2 and the cathode 9 and the light-emitting layer 5 of the organic electroluminescent device of the present invention, as long as the performance is not impaired, except for all In addition to the layer in the above description, it may have arbitrary layers. In addition, arbitrary layers other than the light emitting layer 5 may be omitted.

For example, it is also effective to provide an electron blocking layer between the hole transport layer 4 and the light emitting layer 5 for the same purpose as the hole blocking layer 8 . The electron blocking layer has the following functions: by blocking electrons moving from the light-emitting layer 5 to the hole transport layer 4, the probability of recombination with holes in the light-emitting layer 5 is increased, and the generated excitons are enclosed in the light-emitting layer 5 and the function of efficiently transporting the holes injected from the hole transport layer 4 to the direction of the light emitting layer 5 .

The properties required for the electron blocking layer include high hole transport properties, large energy gap (difference between HOMO and LUMO), and high excited triplet level (T1). When forming the light-emitting layer 5 by a wet film-forming method, it is preferable that the electron blocking layer is also formed by a wet film-forming method because device production becomes easy. Therefore, the electron blocking layer is also preferably suitable for wet film formation. As the material used in this type of electron blocking layer, a copolymer of dioctylfluorene and triphenylamine represented by F8-TFB can be cited. (International Publication No. 2004/084260), etc.

It can also be a structure opposite to that of FIG. 1, that is, a cathode 9, an electron injection layer 8, an electron transport layer 7, a hole blocking layer 6, a light-emitting layer 5, a hole transport layer 4, and a hole layer are sequentially stacked on the substrate 1. Injection layer 3, anode 2. The organic electroluminescence element of the present invention may also be disposed between two substrates at least one of which has high transparency. A structure in which the layer structure shown in FIG. 1 is stacked in multiple stages (a structure in which a plurality of light-emitting units are stacked) may also be used. At this time, if V ₂ O ₅ is used as a charge generation layer instead of the interface layer between the stages (between light-emitting units) (the anode is indium tin oxide (ITO) and the cathode is Al, it means two layers), the number of barriers between stages becomes smaller, which is better from the viewpoint of luminous efficiency and driving voltage.

The present invention can be applied to any one of the organic electroluminescent element being a single element, an element having a structure arranged in an array, and an anode and a cathode arranged in an X-Y matrix.

[Display device and lighting device] The display device and the lighting device of the present invention use the above-mentioned organic electroluminescent element of the present invention. There is no particular limitation on the form or structure of the display device and lighting device of the present invention, and the organic electroluminescent element of the present invention can be used and assembled according to a conventional method.

For example, the display device of the present invention can be formed by the method described in "Organic EL Display" (Ohmsha, published on August 20, 2004, written by Seiji Adachi, Chihaya Adachi, and Hideyuki Murata at the time). and lighting fixtures. [Example]

Hereinafter, an Example is shown and this invention is demonstrated more concretely. The present invention is not limited to the following examples. The present invention can be implemented by arbitrarily changing unless it deviates from the gist of the present invention.

〔Preparation of ink〕 [Example 1] Compound 1 (charge-transporting material) having a structure represented by the following formula (7) and compound 2 (luminescent material) having a structure represented by the following formula (8) were mixed at a mass ratio of 80:20 to prepare into a light-emitting layer material 1. With respect to the light-emitting layer material 1, 2,6-bis-tertiary butylphenol (BHB) corresponding to 2% by mass was added, and further, cyclopentanone-2-methyl carboxylate was added, so that the light-emitting layer material 1 was relatively The total amount of ink was 2.5% by mass (BHB concentration: 500 ppm). After the atmosphere in the container was replaced with nitrogen, it was heated and stirred at 68° C. for 1 hour to dissolve it, and the light-emitting layer ink 1 was prepared.

[chem 33]

[Example 2] Except having added dimethyl phthalate instead of methyl cyclopentanone-2-carboxylate, it carried out similarly to Example 1, and produced the light emitting layer ink 2.

[Comparative example 1] Except having added benzyl benzoate instead of methyl cyclopentanone-2-carboxylate, it carried out similarly to Example 1, and produced the light emitting layer ink 3.

〔Measurement of Surface Tension〕 The surface tension was measured by a pendant drop method using a contact angle meter DM500 manufactured by Kyowa Interface Science. A 3 μL ink droplet was formed at the tip of the syringe, and the shape after 10 seconds was photographed. Using the analysis software FAMAS, the surface tension was calculated from this shape by the Fitting-Laplace method. The preparation and measurement of droplets were repeated 10 times for each ink, and the average value was used as the surface tension of the ink.

〔Measurement and storage〕 After making each emissive layer ink, the nitrogen-sealed ink container vial was cooled to room temperature. The vial was opened to the atmosphere, and half the amount of ink was taken immediately for the initial surface tension measurement (initial surface tension). The remaining half of the ink was sealed again in the atmosphere and stored at room temperature for 28 days. Then, the second surface tension measurement (surface tension after 28 days) was performed using the stored ink.

[Measurement results of surface tension] Table 1 shows the measured values of the surface tensions of the light-emitting layer inks of Example 1, Example 2, and Comparative Example 1 at the initial stage and after 28 days and their changes.

[Table 1] Phenol derivatives solvent Surface tension (mN/m) initial 28 days later Variation Example 1 BHB (500ppm) Methyl cyclopentanone-2-carboxylate 33.9 33.7 0.2 Example 2 BHB (500ppm) Dimethyl phthalate 34.2 34.3 0.1 Comparative example 1 BHB (500ppm) Benzyl Benzoate 36.5 36.9 0.4

As shown in Table 1, by using an aliphatic ester solvent or an aromatic diester solvent having two or more carbonyl groups in an ink containing a specific phenol derivative, the change in surface tension of the ink during long-term storage becomes small, enabling A highly stable composition for an organic electroluminescent device can be obtained.

Although this invention was demonstrated in detail using the specific aspect, it is clear for those skilled in the art that various changes can be added without deviating from the intent and range of this invention. This application is based on Japanese Patent Application No. 2021-078651 filed on May 6, 2021 and Japanese Patent Application No. 2021-078652 filed on May 6, 2021, and the entire contents thereof are incorporated by reference.

1: Substrate 2: anode 3: Hole injection layer 4: Hole transport layer 5: Luminous layer 6: Hole blocking layer 7: Electron transport layer 8: Electron injection layer 9: Cathode 10: Organic electroluminescence element

FIG. 1 is a cross-sectional view schematically showing an example of the structure of the organic electroluminescence device of the present invention.

1: Substrate

2: anode

3: Hole injection layer

4: Hole transport layer

5: Luminous layer

6: Hole blocking layer

7: Electron transport layer

8: Electron injection layer

9: Cathode

10: Organic electroluminescence element

Claims (14)

A composition for an organic electroluminescent device, comprising: a functional material; a compound represented by the following formula (1); and an aliphatic ester solvent and/or an aromatic diester solvent having two or more carbonyl groups,

In the formula, a is an integer of 0 to 4; R ¹ and R ² independently represent an alkyl group with 1 to 12 carbons or an alkoxy group with 1 to 12 carbons; a is an integer of 2 to 4 In the case of , multiple R ² may be the same or different. The composition for an organic electroluminescent device according to claim 1, wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having two ester groups. The composition for an organic electroluminescence device according to claim 1, wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having one ester group and one ketone group. The composition for an organic electroluminescence device according to claim 1, wherein the aliphatic ester solvent having two or more carbonyl groups is represented by the following formula (9-1) or the following formula (9-2) solvent,

In the formula, R ²⁴ represents an alkylene group; R ²⁵ and R ²⁶ independently represent an alkyl group; R ²⁴ and R ²⁵ can be bonded to each other to form a ring,

In the formula, R ²⁷ represents an alkylene group; R ²⁸ and R ²⁹ independently represent an alkyl group; R ²⁷ and R ²⁸ , or R ²⁷ and R ²⁹ may be bonded to each other to form a ring. The composition for an organic electroluminescence element according to claim 4, wherein the aromatic diester solvent is a solvent represented by the following formula (9-3),

In the formula, Ar ³¹ represents an aryl group; R ^30a and R ^30b independently represent an alkyl group; R ^30a and Ar ³¹ may be bonded to each other to form a ring. The composition for an organic electroluminescent element according to any one of claim 1 to claim 5, wherein the compound represented by the formula (1) is a compound represented by the following formula (1-1),

In the formula, b is an integer of 0 to 3; R ³ , R ⁴ , and R ⁵ each independently represent an alkyl group with 1 to 12 carbons or an alkoxy group with 1 to 12 carbons; when b is 2 to 3 In the case of an integer of 3, a plurality of R ⁵ may be the same or different. The composition for an organic electroluminescence element according to Claim 6, wherein the compound represented by the formula (1-1) is a compound represented by the following formula (1-2),

In the formula, b and R ⁵ have the same meanings as b and R ⁵ in the formula (1-1). The composition for an organic electroluminescent device according to any one of claims 1 to 7, wherein the functional material contains an iridium complex. The composition for an organic electroluminescence device according to claim 8, wherein, as the functional material, an iridium complex represented by the following formula (2) is included,

In the above formula, R ⁷ and R ⁸ are independently an alkyl group with 1 to 20 carbons, a (hetero)aralkyl group with 7 to 40 carbons, an alkoxy group with 1 to 20 carbons, or an alkoxy group with 3 to 20 carbons. (hetero)aryloxy group with 20, alkylsilyl group with 1-20 carbons, arylsilyl group with 6-20 carbons, alkylcarbonyl group with 2-20 carbons, aryl group with 7-20 carbons Any one of a carbonyl group, an alkylamino group with 1 to 20 carbons, an arylamino group with 6 to 20 carbons, and a (hetero)aryl group with 3 to 30 carbons, or a combination of these; The group may further have a substituent; when there are multiple R ⁷ and R ⁸ , the multiple R ⁷ and R ⁸ may be the same or different; the adjacent R ⁷ or R ⁸ bonded to the benzene ring may be mutual bonding to form a ring condensed on the benzene ring; d is an integer of 0 to 4; e is an integer of 0 to 3; m is an integer of 1 to 20; n is an integer of 0 to 2; ring A is pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, oxazole ring, thiazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriendene ring, carboline ring Either; ring A may have a substituent, and the substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, Alkoxy with 1 to 20 carbons, (hetero)aryloxy with 3 to 20 carbons, alkylsilyl with 1 to 20 carbons, aryl silyl with 6 to 20 carbons, aryl silyl with 2 to 20 carbons Alkylcarbonyl, arylcarbonyl with 7 to 20 carbons, alkylamino with 2 to 20 carbons, arylamino with 6 to 20 carbons, and (hetero)aryl with 3 to 20 carbons Any one, or a combination of these; adjacent substituents bonded to ring A may be bonded to each other to form a ring condensed on ring A; Z ¹ represents a direct bond or an aromatic linking group with m+1 valence; L ¹ represents an auxiliary ligand; l is an integer of 1 to 3; and when there are a plurality of auxiliary ligands, they may be different or the same. The composition for an organic electroluminescent device according to claim 9, wherein the Z ¹ includes a trivalent group represented by the following formula (2-2A) or formula (2-2B),

. A method for manufacturing an organic electroluminescent device, comprising the step of forming a light emitting layer by a wet film-forming method using the composition for an organic electroluminescent device as described in any one of claim 1 to claim 10. An organic electroluminescent device having a light-emitting layer formed using the composition for an organic electroluminescent device according to any one of claim 1 to claim 10. A display device comprising the organic electroluminescence element as claimed in claim 12. An illuminating device comprising the organic electroluminescence element as claimed in claim 12.

Images