KR20240004358A - Compositions for organic electroluminescent devices, organic electroluminescent devices, display devices and lighting devices - Google Patents

Abstract

[상기 식 중, a 는 0 ∼ 4 의 정수이다. R¹, R² 는, 각각 독립적으로, 탄소수 1 ∼ 12 의 알킬기, 또는 탄소수 1 ∼ 12 의 알콕시기를 나타낸다. a 가 2 ∼ 4 의 정수인 경우, 복수의 R² 는 동일해도 되고, 상이해도 된다.]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 above formula, a is an integer of 0 to 4. R ¹ and R ² each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. When a is an integer of 2 to 4, plural R ² may be the same or different.]

Description

Compositions for organic electroluminescent devices, organic electroluminescent devices, display devices and lighting devices

The present invention relates to a composition for an organic electroluminescent device useful for forming a light-emitting layer of an organic electroluminescent device (hereinafter sometimes referred to as “organic EL device”). The present invention also relates to an organic electroluminescent device having a light-emitting layer formed using the composition for an organic electroluminescent device, a method for manufacturing the same, and a display device and lighting device having the organic electroluminescent device.

Various electronic devices using organic EL elements, such as organic EL lighting and organic EL displays, have been put into practical use. Organic electroluminescent devices consume less power because the applied voltage is low, and they are also capable of emitting light in three primary colors. For this reason, application has begun not only to large display monitors but also to small and medium-sized displays such as mobile phones and smart phones.

Organic electroluminescent devices are manufactured by stacking 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 depositing organic materials under vacuum. However, in the vacuum deposition method, the deposition process becomes complicated and productivity is inferior. In addition, in organic electroluminescent devices manufactured by vacuum deposition, it is very difficult to increase the area of the lighting or display panel.

Recently, the wet film forming method (coating method) has been studied as a process for efficiently manufacturing organic electroluminescent devices that can be used in large-scale displays and lighting. The wet film deposition method has the advantage of being able to easily form a stable layer compared to the vacuum deposition method. For this reason, mass production of displays and lighting devices and application to large devices are expected.

In order to manufacture an organic electroluminescent element using a wet film forming method, it is necessary to dissolve the functional material in an organic solvent and use it as ink. If the solubility of the functional material in the organic solvent is low, the material may deteriorate before use because operations such as heating for a long time are required. Additionally, if a uniform state cannot be maintained in the solution state for a long time, material may precipitate from the solution, making film formation using an inkjet device or the like impossible.

The organic solvent used in ink is required to have solubility in two senses: to quickly dissolve the functional material and to maintain a uniform state after dissolution without precipitating the functional material.

Recently, even when organic electroluminescent devices are manufactured after storing ink for a long period of time, attempts have been made to contain phenol derivatives in the ink for the purpose of suppressing a decrease in the luminous efficiency and driving life of the organic electroluminescent devices. (For example, Patent Documents 1 and 2).

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

Japanese Patent Publication No. 2015-63662 Japanese Patent Publication No. 2015-93938 International Publication No. 2019/212022

Through the above-mentioned prior art, by incorporating a phenol derivative into ink, it has become possible to suppress deterioration of functional materials, which is a factor in lowering luminous efficiency and driving life, even when the ink is stored for a long period of time.

However, the stability of the liquid physical properties of the ink, especially the surface tension stability of the ink, cannot be said to be sufficient, and improvement in the stability of the liquid physical properties has been required.

The object of the present invention is to provide a composition for an organic electroluminescent device with improved stability of liquid properties, especially surface tension stability of ink, for forming a light emitting layer in an organic electroluminescent device by wet film formation.

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

The gist of the present invention is as follows.

[1] 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.

[Formula 1]

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

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

[Formula 2]

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

[Formula 3]

[In the above 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 combine with each other to form a ring.]

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

[Formula 4]

[In the above formula, Ar ³¹ represents an arylene group. R ^30a and R ^30b each independently represent an alkyl group. R ^30a and Ar ³¹ may combine with each other to form a ring.]

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

[Formula 5]

[In the above formula, b is an integer of 0 to 3. R ³ , R ⁴ , and R ⁵ each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. 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 electroluminescent device according to [6], wherein the compound represented by the above formula (1-1) is a compound represented by the following formula (1-2).

[Formula 6]

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

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

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

[Formula 7]

[In the above formula, R ⁷ and R ⁸ are each independently an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, or (hetero) with 3 to 20 carbon atoms. Aryloxy group, alkylsilyl group with 1 to 20 carbon atoms, arylsilyl group with 6 to 20 carbon atoms, alkylcarbonyl group with 2 to 20 carbon atoms, arylcarbonyl group with 7 to 20 carbon atoms, alkylamino group with 1 to 20 carbon atoms, 6 to 20 carbon atoms arylamino group, and (hetero)aryl group having 3 to 30 carbon atoms, or a combination thereof. These groups may further have a substituent. When a plurality of R ⁷ and R ⁸ exist, the plurality of R ⁷ and R ⁸ may be the same or different. Neighboring R ⁷ or R ⁸ bonded to the benzene ring may be bonded to each other to form a ring condensed to the benzene ring.

d is an integer from 0 to 4.

e is an integer from 0 to 3.

m is an integer from 1 to 20.

n is an integer from 0 to 2.

Ring A is a pyridine ring, a pyrazine ring, a pyrimidine ring, an imidazole ring, an oxazole ring, a thiazole ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azatriphenylene ring, and a carboline ring. Which one of them?

Ring A may have a substituent, and the substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, and a carbon number. (hetero)aryloxy group of 3 to 20 carbon atoms, alkylsilyl group of 1 to 20 carbon atoms, arylsilyl group of 6 to 20 carbon atoms, alkylcarbonyl group of 2 to 20 carbon atoms, arylcarbonyl group of 7 to 20 carbon atoms, 2 to 20 carbon atoms It is any of an alkylamino group, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 20 carbon atoms, or a combination thereof. Neighboring substituents bonded to ring A may combine to form a ring condensed to ring A.

Z ¹ represents a direct bond or an m+1 valent aromatic linking group.

L ¹ represents an auxiliary ligand. l is an integer from 1 to 3. When there are multiple auxiliary ligands, they may be different or the same.]

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

[Formula 8]

[11] A method for producing 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 having the organic electroluminescent element according to [12].

[14] A lighting device having the organic electroluminescent element according to [12].

The composition for an organic electroluminescent device of the present invention is excellent in the stability of liquid physical properties, especially in the surface tension stability of ink. For this reason, even if the composition for an organic electroluminescent device of the present invention is stored for a long period of time and then used to manufacture an organic electroluminescent device, there is little decrease in luminous efficiency or driving life, and the change in liquid physical properties is small, so that the display device has little unevenness. I can get a lighting device. That is, the composition for an organic electroluminescent device of the present invention is a composition that can be applied to a large area and can be stored for a long period of time.

In the present invention, the mechanism of action by which such effects are obtained is estimated as follows.

Since the composition for an organic electroluminescent device of the present invention contains the compound represented by the above formula (1), which is a phenol derivative, deterioration of the functional material is suppressed even when the ink is stored for a long period of time. Additionally, since it contains an aliphatic ester and/or aromatic diester solvent having two or more carbonyl groups as a solvent, changes in liquid physical properties accompanying oxidation of the phenol derivative can be reduced.

By containing a phenol derivative in the ink, deterioration due to oxidation of the functional material is suppressed, but the phenol derivative itself is considered to be oxidized. When phenols are oxidized, they usually become phenoxy radicals through proton transfer or hydrogen atom transfer after one-electron oxidation. After that, it is not clear whether phenoxy radicals in the ink are further changed to other substances such as benzoquinones or peroxides, but in any case, the ink has a structure in which no phenolic hydroxy group exists. Phenolic hydroxy groups not only exhibit hydrogen bonding properties but also exhibit acidity due to the resonance effect of the aromatic ring, but their properties are thought to change significantly upon oxidation.

Due to the structural change caused by oxidation of the phenol derivative as described above, it is believed that even if the content of the phenol derivative is small, it affects the liquid physical properties of the ink. However, by containing as a solvent an aliphatic ester and/or aromatic diester solvent having two or more carbonyl groups, which are polar groups, it becomes possible to suppress changes in the physical properties of this liquid.

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

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described in detail. The present invention is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist.

In this specification, (hetero)aralkyl group, (hetero)aryloxy group, and (hetero)aryl group include an aralkyl group that may contain a hetero atom, an aryloxy group that may contain a hetero atom, and a hetero atom, respectively. Indicates an aryl group that may be present.

“May contain a hetero atom” indicates that one or two or more carbon atoms forming the main skeleton of the aryl group, aralkyl group, or aryloxy group are substituted with a hetero atom.

Hetero atoms include nitrogen atoms, oxygen atoms, sulfur atoms, phosphorus atoms, and silicon atoms. Among them, nitrogen atoms are preferable from the viewpoint of durability.

The same goes for (hetero)arylene groups.

In this specification, “aromatic linking group” refers to an aromatic linking group in a broad sense, including 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.

[Composition for organic electroluminescent device]

The composition for an organic electroluminescent 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.

[Formula 9]

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

[Functional materials]

The composition for an organic electroluminescent device of the present invention contains a functional material. A functional material is a light-emitting material or charge-transporting material contained in the light-emitting layer of an organic electroluminescent element.

Since the composition for an organic electroluminescent device of the present invention can contribute the energy of the triplet excited state to light emission, it is preferable to include a phosphorescent organic metal complex as a functional material, and among these, iridium is the central element. It is preferable to include an iridium complex, which is an organic metal complex.

[Iridium complex]

The iridium complex contained in the composition for an organic electroluminescent device of the present invention is preferably represented by the following formula (2) because it has high solubility in organic solvents and high heat resistance.

[Formula 10]

[In the above formula, R ⁷ and R ⁸ are each independently an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, or (hetero) with 3 to 20 carbon atoms. Aryloxy group, alkylsilyl group with 1 to 20 carbon atoms, arylsilyl group with 6 to 20 carbon atoms, alkylcarbonyl group with 2 to 20 carbon atoms, arylcarbonyl group with 7 to 20 carbon atoms, alkylamino group with 1 to 20 carbon atoms, 6 to 20 carbon atoms arylamino group, and (hetero)aryl group having 3 to 30 carbon atoms, or a combination thereof. These groups may further have a substituent. When a plurality of R ⁷ and R ⁸ exist, the plurality of R ⁷ and R ⁸ may be the same or different. Neighboring R ⁷ or R ⁸ bonded to the benzene ring may be bonded to each other to form a ring condensed to the benzene ring.

d is an integer from 0 to 4.

e is an integer from 0 to 3.

m is an integer from 1 to 20.

n is an integer from 0 to 2.

Ring A is a pyridine ring, a pyrazine ring, a pyrimidine ring, an imidazole ring, an oxazole ring, a thiazole ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azatriphenylene ring, and a carboline ring. Which one of them?

Ring A may have a substituent, and the substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, and a carbon number. (hetero)aryloxy group of 3 to 20 carbon atoms, alkylsilyl group of 1 to 20 carbon atoms, arylsilyl group of 6 to 20 carbon atoms, alkylcarbonyl group of 2 to 20 carbon atoms, arylcarbonyl group of 7 to 20 carbon atoms, 2 to 20 carbon atoms It is any of an alkylamino group, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 20 carbon atoms, or a combination thereof. Neighboring substituents bonded to ring A may combine to form a ring condensed to ring A.

Z ¹ represents a direct bond or an m+1 valent aromatic linking group.

L ¹ represents an auxiliary ligand. l is an integer from 1 to 3. When there are multiple auxiliary ligands, they may be different or the same.]

In formula (1), R ⁷ and R ⁸ are each independently an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an arylamino group with 6 to 20 carbon atoms, or It is preferable that it is a (hetero)aryl group with 3 to 30 carbon atoms, and it is more preferable that it is an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, or a (hetero)aryl group with 3 to 20 carbon atoms.

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

d is preferably 0 because it is easy to manufacture. Since solubility is improved, d is preferably 1 or 2, and is more preferably 1.

When two adjacent R ^7s are connected to each other to form a ring, d is preferably 2.

e is preferably 0 because it is easy to manufacture. Since durability and solubility are improved, e is preferably 1 or 2, and is more preferably 1.

When two adjacent R ^8s 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, the substituent includes a fluorine atom, a chlorine atom, a bromine atom, an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, and alkoxy with 1 to 20 carbon atoms. group, (hetero)aryloxy group of 3 to 20 carbon atoms, alkylsilyl group of 1 to 20 carbon atoms, arylsilyl group of 6 to 20 carbon atoms, alkylcarbonyl group of 2 to 20 carbon atoms, arylcarbonyl group of 7 to 20 carbon atoms, 2 carbon atoms Any of an alkylamino group with 20 to 20 carbon atoms, an arylamino group with 6 to 20 carbon atoms, and a (hetero)aryl group with 3 to 20 carbon atoms, or a combination thereof.

Since a phenyl group having a t-butyl group at the terminal increases solubility in organic solvents, m is preferably 2 or more. Since the phenyl group having a t-butyl group at the terminal has little involvement in charge transport or light emission, if there is too much of it, there is a risk that the driving voltage may increase or the light emission efficiency may decrease. For this reason, m is preferably 8 or less, and more preferably 4 or less.

The iridium complex represented by formula (2) has such terminal t-butyl groups as a whole, 4 or more, especially 6 or more, 48 or less, especially 24 or less, so that it has both solubility, low drive voltage, and high luminous efficiency. It is desirable in terms of

n is preferably 0 or 1 because it is easy to manufacture. Since there is little risk of the driving voltage increasing, it is preferable that n is 0. Since solubility is improved, n is preferably 1 or 2.

From the viewpoint of durability, ring A is preferably a pyridine ring, pyrimidine ring, or imidazole ring, and more preferably a pyridine ring.

The hydrogen atom on ring A is substituted with an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, or a (hetero)aryl group having 3 to 20 carbon atoms in order to improve durability and solubility. desirable.

It is preferable that the hydrogen atom on ring A is unsubstituted for ease of production.

The hydrogen atom on ring A is preferably substituted with a phenyl group or naphthyl group, which may have a substituent, because excitons are easily generated when used in an organic electroluminescent device, and luminous efficiency is increased.

Ring A is a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azatriphenylene ring, and a carboline ring, as the substituents on ring A combine with each other to form a condensed ring that condenses with ring A. Because the emission wavelength is longer, it is useful for red light emission. Among them, from the viewpoint of durability and red light emission, it is preferable that ring A forms a quinoline ring, isoquinoline ring, or quinazoline ring.

Z ¹ is preferably a direct bond because it is easy to manufacture.

Z ¹ is preferably an m+1 valent aromatic linking group because there is little risk of the driving voltage becoming high.

When m is 1, from the viewpoint of durability, Z ¹ is preferably a phenylene group, biphenylene group, terphenylene group, or fluorenediyl group, and especially preferably a p-phenylene group.

When m is 2 or more, Z ¹ preferably contains a benzene ring whose bonding position is at the 1,3,5- position or a triazine ring whose bonding position is at the 2,4,6- position from the viewpoint of durability.

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

[Formula 11]

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

L ¹ is an auxiliary ligand. Although there is no particular limitation, L ¹ is preferably a monovalent bidentate ligand, and more preferably is selected from the ligands represented by the following formulas (2A), (2B), and (2C).

The broken lines in the following formulas (2A) to (2C) represent coordination bonds.

When l is 1 and two auxiliary ligands L ¹ exist, the auxiliary ligands L ¹ may be the same as each other or may have different structures.

When l is 3, L ¹ does not exist.

[Formula 12]

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

g is an integer from 0 to 4. h is an integer from 0 to 4. g and h are preferably 0 because of ease of manufacture. Since solubility is improved, g and h are preferably 1 or 2, and more preferably 1.

Ring B is a pyridine ring, a pyrimidine ring, an imidazole ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azatriphenylene ring, a carboline ring, a benzothiazole ring, and a benzoxazole ring. Which one. These may have a substituent.

From the viewpoint of durability, ring B is preferably a pyridine ring, pyrimidine ring, or imidazole ring, and more preferably a pyridine ring.

The hydrogen atom on ring B is substituted with an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, or a (hetero)aryl group having 3 to 20 carbon atoms in order to improve durability and solubility. desirable.

The hydrogen atom on ring B is preferably unsubstituted for ease of production.

The hydrogen atom on ring B is preferably substituted with a phenyl group or naphthyl group, which may have a substituent, because excitons are easily generated when used in an organic electroluminescent device, and luminous efficiency is increased.

Ring B is a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azatriphenylene ring, and a carboline ring, as the substituents on ring B combine with each other to form a condensed ring that condenses to ring B. This is preferable because excitons are easily generated on the assist dopant, thereby increasing luminous efficiency. Among them, from the viewpoint of durability and red light emission, it is preferable that ring B forms a quinoline ring, isoquinoline ring, or quinazoline ring.

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

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

[Formula 13]

[In formula (2-2), R ⁷ , d, m, n, ring A, Z ¹ , L ¹ , l are R ⁷ , d, m, n, ring A, Z in formula (2) ¹ , L ¹ , l has the same meaning.

R ¹⁵ to R ¹⁷ are substituents.]

R ¹⁵ includes the above-mentioned substituents that R ⁸ may have. More preferably, R ¹⁵ is an alkyl group with 1 to 20 carbon atoms or an aromatic hydrocarbon group with 6 to 30 carbon atoms that may be substituted with one or two alkyl groups with 1 to 20 carbon atoms. Here, the aromatic hydrocarbon group having 6 to 30 carbon atoms is a single ring, a two-ring condensed ring, or a three-ring condensed ring, or a group in which a plurality of single rings, a two-ring condensed ring, or a three-ring condensed ring are linked together. R ¹⁵ is more preferably an alkyl group having 1 to 20 carbon atoms, and particularly preferably an alkyl group having 1 to 8 carbon atoms.

R ¹⁶ and R ¹⁷ are part of R ⁸ or a substituent that R ⁸ may have, and are preferably each independently substituted with an alkyl group having 1 to 12 carbon atoms or one or two alkyl groups having 1 to 12 carbon atoms. It is an aromatic hydrocarbon group of 6 to 20 carbon atoms, an alkoxy group of 1 to 12 carbon atoms, or an aromatic hydrocarbon group of 6 to 20 carbon atoms that may be substituted with one or two alkoxy groups of 1 to 12 carbon atoms. Here, the aromatic hydrocarbon group having 6 to 20 carbon atoms is a single ring, a two-ring condensed ring, or a three-ring condensed ring, or a group in which multiple single rings, a two-ring condensed ring, or a three-ring condensed ring are linked together. More preferably, R ¹⁶ and R ¹⁷ are each independently an alkyl group with 1 to 8 carbon atoms, or an aromatic hydrocarbon group with 6 or 12 carbon atoms which may be substituted with one or two alkyl groups with 1 to 8 carbon atoms, especially Preferably, it is an alkyl group with 1 to 8 carbon atoms, or an aromatic hydrocarbon group with 6 carbon atoms that may be substituted with one or two alkyl groups with 1 to 8 carbon atoms. Here, the aromatic hydrocarbon structure with 6 carbon atoms is a benzene structure, and the aromatic hydrocarbon structure with 12 carbon atoms is a biphenyl structure.

Below, preferred specific examples of the compound represented by formula (2), which is an iridium complex that may be included as a functional material in the composition for an organic electroluminescent device of the present invention, are shown.

[Formula 14]

[Formula 15]

[Formula 16]

The composition for an organic electroluminescent device of the present invention may contain only one type of these iridium complexes, or may contain two or more types.

[Charge transport material]

The charge-transporting material that may be included as a functional material in the composition for an organic electroluminescent device of the present invention is a material having positive charge (hole) or negative charge (electron) transport. The charge transport material is not particularly limited and any known material can be applied as long as it does not impair the effect of the present invention.

The charge-transporting material can be a compound conventionally used in the light-emitting layer of an organic electroluminescent device. As the charge-transporting material, compounds used as host materials for the light-emitting layer are particularly preferable.

The charge transport material specifically includes aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, and compounds in which a tertiary amine is linked to a fluorene group. , hydrazone-based compounds, silazane-based compounds, silanamine-based compounds, phosphamine-based compounds, quinacridone-based compounds, and the like, which are exemplified as hole-transporting compounds of the hole injection layer 3 described later. In addition, electron transport compounds such as anthracene-based compounds, pyrene-based compounds, carbazole-based compounds, pyridine-based compounds, phenanthroline-based compounds, oxadiazole-based compounds, and silol-based compounds can be mentioned.

Charge-transporting materials include, for example, two or more tertiary amines such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl and two or more condensed aromatic amines. Aromatic amines having a starburst structure, such as aromatic diamines in which the ring is substituted with a nitrogen atom (Japanese Patent Application Laid-Open No. 5-234681), 4,4',4"-tris(1-naphthylphenylamino)triphenylamine, etc. Compound (J. Lumin., Volume 72-74, Page 985, 1997), Aromatic amine compound consisting of a tetramer of triphenylamine (Chem. Commun., Page 2175, 1996), 2,2',7 Fluorene-based compounds such as ,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth. Metals, Volume 91, Page 209, 1997), 4,4'-N, Compounds exemplified as hole-transporting compounds of the hole-transporting layer 4 described later, such as carbazole-based compounds such as N'-dicarbazole biphenyl, can also be preferably used. As other charge-transporting materials, 2-(4-ratio) Phenylyl)-5-(p-tertibutylphenyl)-1,3,4-oxadiazole (tBu-PBD), 2,5-bis(1-naphthyl)-1,3,4-oxadia Oxadiazole-based compounds such as sol (BND), 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilol (PyPySPyPy), etc. silol-based compounds, phenanthroline-based compounds such as vasophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, vasocuproin), etc. there is.

The charge-transporting material that may be included in the composition for an organic electroluminescent device of the present invention has a repeating unit (hereinafter sometimes referred to as “repeating unit (3)”) containing a structure represented by the following formula (3). It is preferable that it is a high molecular compound in terms of film forming properties.

[Formula 17]

[In formula (3), R ¹⁹ and R ²⁰ are each independently selected from an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, and (hetero) with 3 to 20 carbon atoms. ) Aryloxy group, alkylsilyl group with 1 to 20 carbon atoms, arylsilyl group with 6 to 20 carbon atoms, alkylcarbonyl group with 2 to 20 carbon atoms, arylcarbonyl group with 7 to 20 carbon atoms, alkylamino group with 1 to 20 carbon atoms, 6 to 6 carbon atoms It is either an arylamino group of 20, a (hetero)aryl group of 3 to 30 carbon atoms, or a combination thereof. These groups may additionally have substituents.]

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

The polymer compound having the repeating unit (3), which may be included in the composition for an organic electroluminescent device of the present invention, has a structure represented by the following formula (3-1) in addition to the repeating unit (3) because the charge transport property is increased. It is preferable to include a repeating unit (hereinafter sometimes referred to as “repeating unit (3-1)”). In this case, the repeating unit (3) may be included in the repeating unit (3-1) below.

[Formula 18]

[In formula (3-1), Ar ²¹ to Ar ²³ each independently represent a divalent (hetero)arylene 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 from 0 to 2.]

From the viewpoint of durability, Ar ²¹ to Ar ²³ are each independently preferably a phenylene group, a biphenylene group, a terphenylene group, a fluorenediyl group, or a divalent group having 30 or less carbon atoms in which these groups are arbitrarily selected and connected, In particular, p-phenylene group and biphenylene group are preferable. These groups may have a substituent.

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

From the viewpoint 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 in particular, a phenyl group or a fluorenyl group is preferable. These groups may have a substituent.

The polymer compound having the repeating unit (3) that may be contained in the composition for an organic electroluminescent device of the present invention may contain only one type of the repeating unit (3), or may contain two or more types. Moreover, it may contain only one type of repeating unit (3-1), or may contain two or more types.

The weight average molecular weight (Mw) of the polymer compound having the repeating unit (3) that may be included in the composition for an organic electroluminescent device of the present invention is usually 2,000,000 or less, preferably 500,000 or less, more preferably 100,000 or less, and further. Preferably it is 50,000 or less, usually 2,500 or more, preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 20,000 or more.

If the weight average molecular weight is below the above upper limit, the solubility in the solvent is excellent and the film forming property is also excellent. If the weight average molecular weight is more than the above lower limit, the glass transition temperature, melting point, and vaporization temperature of the polymer compound are high, and heat resistance is excellent.

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

The dispersion degree (Mw/Mn) of the polymer compound having the repeating unit (3) that may be included 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 is 2.0 or less. Since the smaller the dispersion value, the better, the lower limit is ideally 1. If the degree of dispersion of the polymer compound is below the above upper limit, purification is easy and the solubility in solvents and charge transport ability are good.

Usually, the weight average molecular weight of a polymer compound is determined by SEC (size exclusion chromatography) measurement. In SEC measurement, the higher the molecular weight component, the shorter the elution time, and the lower the molecular weight component, the longer the elution time. The weight average molecular weight is calculated by converting the elution time of the sample to the molecular weight using a calibration curve calculated from the elution time of polystyrene (standard sample) whose molecular weight is already known. The same can be obtained for the number average molecular weight.

The method for producing 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 not particularly limited, and is optional as long as the polymer compound having the repeating unit (3) is obtained. For example, it can be produced by a polymerization method by Suzuki reaction, a polymerization method by Grignard reaction, a polymerization method by Yamamoto reaction, a polymerization method by Ullmann reaction, a polymerization method by Buchwald-Hartwig reaction, etc.

[Phenol derivative]

The composition for an organic electroluminescent device of the present invention contains a phenol derivative which is a compound represented by the following formula (1).

[Formula 19]

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

In the compound represented by formula (1), the presence of an alkyl group or alkoxy group, which is an electron donating group, at the o-position of the hydroxy group causes the oxidation-reduction potential of the compound represented by formula (1) to shift to the negative side and the HOMO becomes shallow. , itself becomes prone to oxidation. For this reason, oxidation of the functional materials contained at the same time is suppressed.

a is preferably 1 or 2 because it provides an appropriate oxidation-reduction potential.

Examples of when R ¹ and R ² are an alkyl group having 1 to 12 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, s-butyl group, t-butyl group, pentyl group, They are isopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, and dodecyl group.

Examples of R ¹ and R ² being an alkoxy group having 1 to 12 carbon atoms include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, s-butoxy group, and t-butoxy group. , pentyloxy group, isopentyloxy group, hexyloxy group, cyclohexyloxy group, heptyloxy group, octyloxy group, 2-ethylhexyloxy group, nonyloxy group, decyloxy group, undecyloxy group, and dodecyloxy group. .

R ¹ and R ² are secondary or tertiary alkyl groups because they have large steric hindrance, suppress the coupling reaction between phenoxy radicals generated after oxidation, and can function as antioxidants again. preferred, and a tertiary alkyl group is more preferred. The o- position of the hydroxy group is preferably a t-butyl group, which is the smallest tertiary alkyl group, because it is inexpensive, has a low molecular weight, and is difficult to remain in the light-emitting layer after film formation.

It is preferable that both of the o- positions of the hydroxy groups are alkyl groups or alkoxy groups because this provides an appropriate redox potential and the stability of phenoxy radicals generated after oxidation is high.

That is, the composition for an organic electroluminescent device of the present invention preferably contains a compound represented by the following formula (1-1) as the compound represented by the formula (1).

[Formula 20]

[In the above formula, b is an integer of 0 to 3. R ³ , R ⁴ , and R ⁵ each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. 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 because it provides an appropriate oxidation-reduction potential.

The o-position of the hydroxy group has a large steric hindrance, suppresses the coupling reaction between phenoxy radicals generated after oxidation, and can function as an antioxidant again, so it is a second or third class. An alkyl group is preferable, and a tertiary alkyl group is more preferable. The o- position of the hydroxy group is preferably a t-butyl group, which is the smallest tertiary alkyl group, because it is inexpensive, has a low molecular weight, and is difficult to remain in the light-emitting layer after film formation.

That is, the composition for an organic electroluminescent device of the present invention preferably contains a compound represented by the following formula (1-2) as the compound represented by formula (1).

[Formula 21]

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

As described above, b is preferably 0 or 1 because it provides an appropriate oxidation-reduction potential.

[menstruum]

The composition for an organic electroluminescent 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 electroluminescent device of the present invention is a volatile liquid component used to form a layer containing a functional material by wet film formation. The solvent is preferably a solvent in which functional materials such as light-emitting materials and charge-transporting materials are well dissolved.

<Aliphatic ester solvent having two or more carbonyl groups>

The aliphatic ester solvent having two or more carbonyl groups has one or more carbonyl groups other than the carbonyl group contained in the aliphatic carboxylic acid ester portion. The carbonyl group additionally possessed by the solvent may be an aliphatic carboxylic acid ester group or not an aliphatic carboxylic acid ester group, but the aliphatic carboxylic acid ester group is a change in the liquid physical properties of the ink due to a structural change due to oxidation of the phenol derivative. It is desirable in that it can further suppress.

Examples of carbonyl groups other than aliphatic carboxylic acid ester groups include aromatic carboxylic acid ester groups, aliphatic carboxylic acid amide groups, aromatic carboxylic acid amide groups, ketone groups, and aldehyde groups. However, ketone groups are responsible for the oxidation of phenol derivatives. This is desirable in that it can further suppress changes in the liquid physical properties of ink due to structural changes.

The aliphatic ester solvent having two or more carbonyl groups is preferably a compound having two ester groups because it can further suppress changes in the liquid physical properties of the ink due to structural changes due to oxidation of the phenol derivative. In addition, since light-emitting materials and charge-transporting materials, which are functional materials, are more readily dissolved, it is preferable that the compound has one ester group and one ketone group.

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.

[Formula 22]

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

R ²⁴ is preferably an alkylene group having 1 to 20 carbon atoms, and more preferably an alkylene group having 2 to 12 carbon atoms because it has appropriate volatility as a solvent. Since R ²⁵ and R ²⁶ have appropriate volatility as a solvent, each independently is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably is an alkyl group having 1 to 6 carbon atoms.

R ²⁴ , which is an alkylene group, may be linear, branched, or cyclic. R ²⁴ is preferably a linear alkylene group because it increases the viscosity of the ink and reduces flow after application. R ²⁴ is preferably a branched alkylene group because the viscosity of the ink is lowered and the ejection properties are stable when applied by the inkjet method. R ²⁴ is preferably a cyclic alkylene group because the viscosity of the ink is lowered and the ejection properties are stable when applied by the inkjet method.

R ²⁵ and R ²⁶ , which are alkyl groups, may be the same or different from each other. Additionally, R ²⁵ and R ²⁶ may be linear, branched, or cyclic. R ²⁵ and R ²⁶ are preferably linear alkyl groups because the viscosity of the ink increases and flow after application can be reduced. R ²⁵ and R ²⁶ are preferably branched alkyl groups because the viscosity of the ink is lowered and the discharge properties are stable when applied by the inkjet method. R ²⁵ and R ²⁶ are preferably cyclic alkyl groups because the viscosity of the ink is lowered and the discharge properties are stable when applied by the inkjet method.

The compound represented by the above formula (9-1) is preferably an aliphatic dicarboxylic acid ester containing a cyclic structure because it is easy to dissolve the solute and facilitates the production of high-concentration ink.

The composition for an organic electroluminescent 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.

[Formula 23]

[In the above 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 combine with each other to form a ring.]

Since R ²⁷ has appropriate volatility as a solvent, an alkylene group having 1 to 20 carbon atoms is preferable, and an alkylene group having 2 to 12 carbon atoms is more preferable. Since R ²⁸ and R ²⁹ have appropriate volatility as a solvent, each independently is preferably an alkyl group having 1 to 20 carbon atoms, and more preferably is an alkyl group having 1 to 6 carbon atoms.

R ²⁷ , which is an alkylene group, may be linear, branched, or cyclic. R ²⁷ is preferably a linear alkylene group because it increases the viscosity of the ink and reduces flow after application. R ²⁷ is preferably a branched alkylene group because the viscosity of the ink is lowered and the ejection properties are stable when applied by the inkjet method. R ²⁷ is preferably a cyclic alkylene group because the viscosity of the ink is lowered and the ejection properties are stable when applied by the inkjet method.

R ²⁸ and R ²⁹ , which are alkyl groups, may be the same or different from each other. Additionally, R ²⁸ and R ²⁹ may be linear, branched, or cyclic. R ²⁸ and R ²⁹ are preferably linear alkyl groups because the viscosity of the ink increases and flow after application can be reduced. R ²⁸ and R ²⁹ are preferably branched alkyl groups because the viscosity of the ink is lowered and the discharge properties are stable when applied by the inkjet method. R ²⁸ and R ²⁹ are preferably cyclic alkyl groups because the viscosity of the ink is lowered and the ejection properties are stable when applied by the inkjet method.

The compound represented by the above formula (9-2) is preferably an aliphatic carboxylic acid ester containing a cyclic structure and having a ketone group because it is easy to dissolve the solute and facilitates the production of high-concentration ink.

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

＜Aromatic diester solvent＞

Aromatic diester solvents are preferred because they can effectively suppress changes in the liquid physical properties of ink due to structural changes due to oxidation of phenol derivatives. Aromatic diester solvents are also preferable because they can easily dissolve the solute.

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

[Formula 24]

[In the above formula, Ar ³¹ represents an arylene group, and R ^30a and R ^30b each independently represent an alkyl group. R ^30a and Ar ³¹ may combine with each other to form a ring.]

Ar ³¹ is preferably a phenylene group or naphthalenediyl group, and more preferably a phenylene group, because it has appropriate volatility as a solvent. Ar ³¹ is preferably an o-phenylene group or an m-phenylene group, and more preferably an m-phenylene group, since the viscosity of the ink is lowered and the discharge properties are stable when applied by the inkjet method.

Since R ^30a and R ^30b have appropriate volatility as a solvent, an alkyl group having 1 to 20 carbon atoms is preferable, and an alkyl group having 1 to 6 carbon atoms is more preferable.

R ^30a and R ^30b , which are alkyl groups, may be the same or different from each other. Additionally, R ^30a and R ^30b may be straight chain, branched, or cyclic. R ^30a and R ^30b are preferably linear alkyl groups because the viscosity of the ink increases and flow after application can be reduced. R ^30a and R ^30b are preferably branched alkyl groups because the viscosity of the ink is lowered and the discharge properties are stable when applied by the inkjet method. R ^30a and R ^30b are preferably cyclic alkyl groups because the viscosity of the ink is lowered and the discharge properties are stable when applied by the inkjet method. R ^30a and R ^30b are preferably an alkyl group containing a cyclic structure because it is easy to dissolve the solute and facilitate the production of high-concentration ink.

These aromatic diester solvents may be used individually, or two or more types may be used in any combination and ratio.

Additionally, the composition for an organic electroluminescent device of the present invention optionally contains one or two or more types of aliphatic ester solvents having two or more carbonyl groups as described above and one or two or more types of aromatic diester solvents as described above. It may be included in a combination and ratio.

＜Other solvents＞

The composition for an organic electroluminescent device of the present invention may contain a solvent other than an aliphatic ester solvent and an aromatic diester solvent having two or more carbonyl groups.

As other solvents, alkylated biphenyls, aromatic ethers, and aromatic monoesters are preferable because they have an appropriate boiling point and are easy to dissolve the solute.

As other solvents, alkylated biphenyls that may be included in the composition for organic electroluminescent devices of the present invention may be monoalkylated biphenyls having one alkyl group, dialkylated biphenyls having two alkyl groups, or three or more alkyl groups. It may be trialkylated biphenyl, tetraalkylated biphenyl, heptaalkylated biphenyl, hexaalkylated biphenyl, etc.

Because of its low boiling point and high volatility, monoalkylated biphenyls or dialkylated biphenyls are preferred, and monoalkylated biphenyls are more preferred.

Since the melting point is high and there is little risk of coagulation when the composition is placed at a low temperature, dialkylated biphenyls and trialkylated biphenyls are preferable, and trialkylated biphenyls are more preferable.

Dealkylated biphenyls are preferred because they have appropriate boiling and melting points.

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

[Formula 25]

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

R ³¹ , the alkyl group substituted by biphenyl, is preferably an alkyl group having 1 to 12 carbon atoms, and examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, and t-butyl. group, pentyl group, isopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, and dodecyl group. Among these, methyl group, ethyl group, propyl group, and isopropyl group are particularly preferable because they have a low boiling point and can ensure high volatility. R ³¹ may have a phenyl group as a substituent. In this case, the alkyl group having a substituent is preferably a benzyl group or a 2-phenylethyl group.

Monoalkylated biphenyl includes, for example, 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, 2-ethylbiphenyl, 3-ethylbiphenyl, 4-ethylbiphenyl, 2-propyl. Biphenyl, 3-propylbiphenyl, 4-propylbiphenyl, 2-isopropylbiphenyl, 3-isopropylbiphenyl, 4-isopropylbiphenyl, 2-butylbiphenyl, 3-butylbiphenyl, 4- Butyl biphenyl, 4-cyclohexyl biphenyl, etc. are mentioned.

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

[Formula 26]

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

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

Examples of dialkylated biphenyl include 2,3-dimethylbiphenyl, 3,4-dimethylbiphenyl, 3,3'-dimethylbiphenyl, 2,4-diethylbiphenyl, 2,3'- Diethyl biphenyl, 3,4'-diethyl biphenyl, 2,2'-dipropyl biphenyl, 2,4-dipropyl biphenyl, 2,4'-dipropyl biphenyl, 3,4-diiso Propyl biphenyl, 3,4'-diisopropyl biphenyl, 3,5-diisopropyl biphenyl, 3,3'-butyl biphenyl, 3,4'-butyl biphenyl, 4,4'-butyl biphenyl Phenyl, etc. can be mentioned.

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

[Formula 27]

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

Preferred examples of R ³⁶ to R ⁴¹ are the same as those of R ³¹ .

Examples of trialkylated biphenyl 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'-tripropyl biphenyl, 2,3',4-triisopropyl biphenyl, 2,3',5-triisopropyl biphenyl, 3,4,4'-triisopropyl ratio. Phenyl, etc. can be mentioned.

These alkylated biphenyls may be used individually, or two or more types may be used in any combination and ratio.

As another solvent, an aromatic ether that may be included in the composition for an organic electroluminescent device of the present invention is preferably an alkoxybenzene which may have an alkyl group represented by the following formula (5) because it has high solubility.

[Formula 28]

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

Since i has a low boiling point and high volatility, an integer of 0 to 3 is preferable, and 0 or 1 is more preferable.

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

As other solvents, aromatic ethers that may be included in the composition for an organic electroluminescent device of the present invention include phenocyl which may have an alkyl group represented by the following formula (5-1) because it has a high boiling point and is suitable for large-area application. Sibenzene is preferred.

[Formula 29]

[In the above formula, j and k represent integers from 0 to 5. R ⁵³ and R ⁵⁴ each independently represent an alkyl group that may have a substituent.]

Since j and k have a low boiling point and high volatility, an integer of 0 to 2 is preferable, and 0 or 1 is more preferable.

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

As another solvent, an aromatic monoester that may be included in the composition for an organic electroluminescent device of the present invention is preferably a benzoic acid monoester that may have an alkyl group represented by the following formula (6).

[Formula 30]

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

Since q has a low boiling point and high volatility, an integer of 0 to 2 is preferable, and 0 or 1 is more preferable.

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

These aromatic ethers and/or aromatic monoesters may be used individually, or two or more types may be used in any combination and ratio. That is, only one type of aromatic ether may be used, only one type of aromatic monoester may be used, or any combination of one or two or more types of aromatic ether and one or two or more types of aromatic monoester, and You can also use it as a ratio.

The composition for an organic electroluminescent device of the present invention includes solvents other than aliphatic ester solvents and aromatic diester solvents having two or more carbonyl groups, and includes solvents other than the alkylated biphenyls, aromatic ethers, and aromatic monoesters. You can do it.

Other preferred solvents other than alkylated biphenyls, aromatic ethers, and aromatic monoesters include alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; Aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene (phenylcyclohexane), and tetralin; Halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, and trichlorobenzene; Alicyclic ketones such as cyclohexanone, cyclooctanone, and fenchone; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; and aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA).

These other solvents may be used individually, or two or more types may be used in any combination and ratio.

＜Boiling point of solvent＞

The boiling point of the solvent is usually 80°C or higher, preferably 100°C or higher, more preferably 150°C or higher, particularly preferably 200°C or higher, and usually 350°C or lower, preferably 320°C or lower, more preferably It is below 300℃. If the boiling point is below this range, film formation stability may decrease due to solvent evaporation 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 is 0.1 mass% or more, more preferably 0.2 mass% or more, preferably 8.0 mass% or less, more preferably 4.0 mass% or less, and even more preferably 2.0 mass% or less.

If the concentration of the light emitting material is more than the above lower limit, a layer containing sufficient light emitting material can be formed. If the concentration of the light emitting material is below the above upper limit, it is easy to maintain a uniform state without precipitating the dissolved light emitting material.

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% by mass or more. Preferably it is 0.2 mass% or more, more preferably 0.4 mass% or more, preferably 16 mass% or less, more preferably 8.0 mass% or less, and even more preferably 4.0 mass% or less.

If the concentration of the charge-transporting material is more than the above lower limit, a layer containing sufficient charge-transporting material can be formed. If the concentration of the charge-transporting material is below the above upper limit, it is easy to maintain a uniform state without precipitating the dissolved charge-transporting material.

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% by mass or more, More preferably, it is 0.2 mass% or more, more preferably 0.4 mass% or more, preferably 16 mass% or less, more preferably 8.0 mass% or less, and even more preferably 4.0 mass% or less.

If the total concentration of functional materials is more than the above lower limit, a layer containing sufficient functional materials can be formed. If the total concentration of the functional materials is below the above upper limit, it is easy to maintain a uniform state without precipitating the dissolved functional materials.

The mass ratio of the content of the light-emitting material and the charge-transporting material = light-emitting material:charge-transporting material is preferably in the range of 1:0.8 to 16, especially in the range of 1:1.2 to 8.0, especially in the range of 1:1.6 to 4.0. If the mass ratio of the contents of the light-emitting material and the charge-transporting material is within the above range, it is possible to manufacture an organic electroluminescent device with a low driving voltage and high luminous efficiency.

The content (concentration) of the phenol derivative, which is a compound represented by the above formula (1), contained in the composition for an organic electroluminescent device of the present invention is preferably 5 mass ppm or more, more preferably 10 mass ppm or more, even more preferably is 20 ppm by mass or more, preferably 4000 ppm by mass or less, more preferably 2000 ppm by mass or less, and even more preferably 1000 ppm by mass or less.

If the concentration of the phenol derivative is more than the above lower limit, the effect of suppressing the deterioration of the functional material due to the phenol derivative can be sufficiently obtained. If the concentration of the phenol derivative is below the above upper limit, it is easy to remove the phenol derivative and its oxide along with the solvent when forming the light-emitting layer.

The content of the aliphatic ester solvent and/or aromatic diester solvent having two or more carbonyl groups contained in the composition for an organic electroluminescent device of the present invention is preferably 2.0% by mass or more, more preferably 5.0% by mass or more. Preferably it is 10% by mass or more. If the content of the aliphatic ester solvent and/or aromatic diester solvent having two or more carbonyl groups is more than the above lower limit, the change in liquid physical properties when the ink is stored for a long time can be reduced.

The composition for an organic electroluminescent device of the present invention may further contain the other solvents described above in addition to the aliphatic ester solvent and/or aromatic diester solvent having two or more carbonyl groups. When the device composition contains other solvents, the content of the other solvents in the total solvent is determined by determining the effect of the present invention by using an aliphatic ester solvent and/or an aromatic diester solvent having two or more carbonyl groups. In order to obtain it effectively, it is preferably 95% by mass or less, especially 85% by mass or less.

The total solvent content in the composition for an organic electroluminescent device of the present invention is preferably large because it has low viscosity and makes it easy to form a film, and is preferably small because it is easy to form a thick film. The total solvent content of the composition for an organic electroluminescent device of the present invention is preferably 1% by mass or more, more preferably 10% by mass or more, particularly preferably 50% by mass or more, and preferably 99.99% by mass. % or less, more preferably 99.9 mass% or less, particularly preferably 99 mass% or less.

[Usage]

The composition for an organic electroluminescent device of the present invention is particularly preferably used as a composition for forming a light-emitting layer containing a light-emitting material and a charge-transporting material as a functional material.

[Organic electroluminescent device]

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 device of the present invention preferably has at least an anode, a cathode, and at least one organic layer between the anode and the cathode on a substrate, and at least one layer of the organic layer is the organic electric field of the present invention. This is a light-emitting layer formed by a wet film forming method using a composition for light-emitting devices.

In the present invention, the wet film forming method refers to a film forming method, that is, an application method, including, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, A method of forming a film by employing a wet film forming method such as a capillary coating method, inkjet method, nozzle printing method, screen printing method, gravure printing method, or flexo printing method, and drying the film formed by these methods. says

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

Materials applied to these structures may be known materials and are not particularly limited. Representative materials and manufacturing methods for each layer are described below as examples. When citing publications, papers, etc., it is assumed that the relevant content can be appropriately applied and applied within the scope of common sense of a person skilled in the art.

[Substrate (1)]

The substrate 1 serves as a support for the organic electroluminescent element, and usually a quartz or glass plate, a metal plate or metal foil, a plastic film or sheet, etc. are used. Among these, glass plates and plates of transparent synthetic resins such as polyester, polymethacrylate, polycarbonate, and polysulfone are preferable. The substrate 1 is preferably made of a material with high gas barrier properties because deterioration of the organic electroluminescent element due to external air is unlikely to occur. For this reason, especially when using a material with low gas barrier properties, such as a synthetic resin substrate, it is desirable to form a dense silicon oxide film or the like on at least one side of the substrate 1 to increase the gas barrier properties.

[Anode (2)]

The anode 2 serves the function of injecting holes into the layer on the light-emitting layer side.

Anode (2) Metals such as silver, cylindrical, aluminum, gold, silver, nickel, palladium, and platinum; Metal oxides such as oxides of indium and/or tin; Halogenated metals such as copper iodide; It is composed of carbon black or conductive polymers such as poly(3-methylthiophene), polypyrrole, and polyaniline.

The formation of the anode 2 is usually performed by dry methods such as sputtering and vacuum deposition. When 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., they are dispersed in an appropriate binder resin solution and applied on the substrate. It can also be formed by doing. In the case of conductive polymers, a thin film can be formed directly on the substrate by electrolytic polymerization, or the anode (2) can be formed by applying the conductive polymer on the substrate (Appl. Phys. Lett., Vol. 60, Page 2711, 1992).

The anode 2 usually has a single-layer structure, but may also have a laminated structure, as appropriate. When the anode 2 has a laminated structure, different conductive materials may be laminated on the first layer anode.

The thickness of the anode 2 may be determined depending on the required transparency, material, etc. In particular, when high transparency is required, a thickness with a visible light transmittance of 60% or more is preferable, and a thickness of 80% or more is more preferable. The thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably 500 nm or less.

When transparency is not required, the thickness of the anode 2 may be any thickness depending on the 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, before forming the film, treatment with ultraviolet rays + ozone, oxygen plasma, argon plasma, etc. is performed to remove impurities on the anode and adjust the ionization potential to improve hole injection properties. It is desirable to improve .

[Hole injection layer (3)]

The layer responsible for transporting holes from the anode 2 side to the light emitting layer 5 side is usually called a hole injection and transport layer or a hole transport layer. When there are two or more layers responsible for transporting holes from the anode (2) side to the light emitting layer (5) side, the layer closer to the anode (2) side is called the hole injection layer (3). There is. The hole injection layer 3 is preferably used because it enhances the function of transporting holes from the anode 2 to the light emitting layer 5 side. When 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 1 nm or more, preferably 5 nm or more, usually 1000 nm or less, and preferably 500 nm or less.

The method for forming the hole injection layer 3 may be a vacuum deposition method or a wet film forming method. In terms of excellent film forming properties, it is preferable to form by a wet film forming method.

The hole injection layer 3 preferably contains a hole-transporting compound, and more preferably contains a hole-transporting compound and an electron-accepting compound. Furthermore, it is preferable that the hole injection layer 3 contains a cation radical compound, and it is especially preferable that it contains a cation radical compound and a hole transport compound.

(Hole transport compound)

The composition for forming a hole injection layer usually contains a hole-transporting compound that becomes the hole injection layer (3). In addition, in the case of a wet film forming method, a solvent is usually additionally contained. The hole-transporting compound preferably has high hole-transporting properties and is capable of efficiently transporting injected holes. For this reason, it is preferable that the hole-transporting compound has high hole mobility and that impurities that become traps are unlikely to be generated during production or use. In addition, the hole-transporting compound is preferably excellent in stability, has a small ionization potential, and has high transparency to visible light. In particular, when the hole injection layer 3 is in contact with the light-emitting layer 5, it is desirable not to quench the light emission from the light-emitting layer 5 or to form an exciplex with the light-emitting layer 5 and not reduce the light emission efficiency. .

As the hole-transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable from the viewpoint of the charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole-transporting compounds include aromatic amine-based compounds, phthalocyanine-based compounds, porphyrin-based compounds, oligothiophene-based compounds, polythiophene-based compounds, benzylphenyl-based compounds, compounds in which a tertiary amine is linked to a fluorene group, and hydra. Examples include zonal compounds, silazane-based compounds, and quinacridone-based compounds.

Among the above-mentioned exemplary compounds, aromatic amine compounds are preferable, and aromatic tertiary amine compounds are particularly preferable from the viewpoint of amorphousness and visible light transparency. Here, the aromatic tertiary amine compound refers to a compound having an aromatic tertiary amine structure, and also includes a compound having a group derived from an aromatic tertiary amine.

The type of aromatic tertiary amine compound is not particularly limited, but since it is easy to obtain uniform light emission due to the surface smoothing effect, a polymer compound (polymerized compound with a series of repeating units) with a weight average molecular weight of 1,000 to 1,000,000 is used. It is desirable.

Preferred examples of aromatic tertiary amine polymer compounds include polymer compounds having a repeating unit represented by the following formula (I).

[Formula 31]

[In the above formula, Ar ¹ and Ar ² each independently represent an aromatic group that may have a substituent or a heteroaromatic group that may have a substituent. Ar ³ to Ar ⁵ each independently represent an aromatic group that may have a substituent or a heteroaromatic group that 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.]

The linking group is shown below.

[Formula 32]

[In each of the above formulas, Ar ⁶ to Ar ¹⁶ each independently represent an aromatic group that may have a substituent or a heteroaromatic group that 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 groups derived from a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene ring, or a pyridine ring, from the viewpoint of solubility of the polymer compound, heat resistance, and hole injection and transport properties, Groups derived from a benzene ring or a naphthalene ring are more preferable.

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

(electron-accepting compound)

The hole injection layer 3 preferably contains an electron-accepting compound because the conductivity of the hole injection layer 3 can be improved by oxidation of the hole-transporting compound.

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

Such electron-accepting compounds include, for example, one selected from the group consisting of triaryl boron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. A species or two or more types of compounds can be mentioned. Specifically, substituted onium salts of organic groups such as 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate and triphenylsulfonium tetrafluoroborate (International Publication No. 2005) /089024) ; High-valence inorganic compounds such as iron (III) chloride (Japanese Patent Application Publication No. Hei 11-251067) and ammonium peroxo di sulfate; Cyano compounds such as tetracyanoethylene; Aromatic boron compounds such as tris(pentafluorophenyl)borane (Japanese Patent Application Laid-Open No. 2003-31365); Fullerene derivatives, iodine, etc. can be mentioned.

(cation radical compound)

The cation radical compound is preferably an ionic compound composed of a cation radical and a counter anion, which are chemical species in which one electron has been removed from the hole-transporting compound. However, when the cation radical is derived from a hole-transporting polymer compound, the cation radical has a structure in which one electron is removed from the repeating unit of the polymer compound.

The cation radical is preferably a chemical species obtained by removing one electron from the compound described above as the hole-transporting compound. A chemical species obtained by removing one electron from a compound preferred as a hole-transporting compound is preferable in terms of amorphousness, visible light transmittance, heat resistance, and solubility.

The cation radical compound can be produced by mixing the above-mentioned hole transporting compound and the electron accepting compound. That is, by mixing the hole-transporting compound and the electron-accepting compound described above, electron transfer occurs from the hole-transporting compound to the electron-accepting compound, and a cation ion compound composed of the cation radical and counter anion of the hole-transporting compound is generated.

Cation radical compounds derived from polymer compounds such as PEDOT/PSS (Adv. Mater., 2000, Volume 12, Page 481) or emeraldine hydrochloride (J. Phys. Chem., 1990, Volume 94, Page 7716) are , It can also be produced through oxidative polymerization (dehydrogenation polymerization).

Oxidative polymerization as referred to here means chemically or electrochemically oxidizing a monomer using peroxo disulfate or the like in an acidic solution. In the case of this oxidation polymerization (dehydrogenation polymerization), the monomer is oxidized to become a polymer, and a cation radical with one electron removed from the repeating unit of the polymer, which uses the anion derived from the acidic solution as a counter anion, is generated.

(Formation of hole injection layer 3 by wet film formation method)

When forming the hole injection layer 3 by a wet film formation method, the material forming the hole injection layer 3 is usually mixed with a soluble solvent (solvent for the hole injection layer) to form a composition for film formation (for forming the hole injection layer). composition) is prepared, and this composition for forming a hole injection layer is formed into a film on the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by a wet film forming method, and then dried. Drying of the formed film can be performed in the same manner as the drying method for forming the light emitting layer 5 by the wet film forming method described later.

The concentration of the hole-transporting compound in the composition for forming a hole injection layer is arbitrary as long as it does not significantly impair the effect of the present invention, but in terms of film thickness uniformity, it is preferable to be low, and the concentration of the hole-transporting compound in the hole injection layer 3 A higher value is preferable in that defects are less likely to occur. Specifically, the concentration of the hole transporting compound in the composition for forming a hole injection layer is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, particularly preferably 0.5 mass% or more, and 70 mass% or less. It is preferable, it is more preferable that it is 60 mass % or less, and it is especially preferable that it is 50 mass % or less.

Examples of solvents include ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and amide-based solvents.

Ether-based solvents include, for example, aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA), and 1,2-dimethoxybenzene, 1,3- Aromatic ethers such as dimethoxybenzene, anisole, phenetol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole. You can.

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, 1,4-diisopropylbenzene, and methylnaphthalene. etc. can be mentioned.

Examples of amide-based solvents include N,N-dimethylformamide, N,N-dimethylacetamide, and the like.

In addition to these, dimethyl sulfoxide and the like can also be used.

The formation of the hole injection layer 3 by a wet film formation method usually involves preparing a composition for forming the hole injection layer, and then applying this to a layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2). This is carried out by applying a film onto the surface and drying it. After the hole injection layer 3 is formed, the coating film is usually dried by heating or reduced-pressure drying.

(Formation of hole injection layer 3 by vacuum deposition method)

When forming the hole injection layer 3 by a vacuum deposition method, usually one or two or more types of constituent materials of the hole injection layer 3 (the above-mentioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum container. Put them in an installed crucible (when using two or more types of materials, usually put each in a different crucible), evacuate the inside of the vacuum container to about 10 ^-4 Pa with a vacuum pump, and then heat the crucible (two or more types of materials). When using, usually by heating each crucible), evaporating while controlling the evaporation amount of the material in the crucible (when using two or more types of materials, usually evaporating while controlling the evaporation amount independently), and evaporating the crucible A hole injection layer (3) is formed on the anode (2) on the substrate facing each other. When two or more types of materials are used, the hole injection layer 3 can be formed by placing their mixture in a crucible, heating and evaporating it.

The degree of vacuum during deposition is not limited as long as it does not significantly impair the effect of the present invention, but is usually 0.1 × 10 ^-6 Torr (0.13 × 10 ^-4 Pa) or more, 9.0 × 10 ^-6 Torr (12.0 × 10 ^-4 Pa) or less. The deposition rate is not limited as long as it does not significantly impair the effect of the present invention, but is usually 0.1 Å/sec or more and 5.0 Å/sec or less. The film formation temperature during vapor deposition is not limited as long as it does not significantly impair the effect of the present invention, 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. Although the hole transport layer 4 is not an essential layer in the organic electroluminescent device of the present invention, it is preferable to form this layer in terms of enhancing the function of transporting holes from the anode 2 to the light emitting layer 5. do. When forming the hole transport layer 4, the hole transport layer 4 is usually formed between the anode 2 and the light emitting layer 5. When the hole injection layer 3 described above is present, 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 5 nm or more, preferably 10 nm or more, and is usually 300 nm or less, preferably 100 nm or less.

The method for forming the hole transport layer 4 may be a vacuum deposition method or a wet film forming method. In terms of excellent film forming properties, it is preferable to form by a wet film forming method.

The hole transport layer 4 usually contains a hole transport compound that serves as the hole transport layer 4. Hole transport compounds contained in the hole transport layer 4 include, in particular, two or more tertiary amines represented by 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl. aromatic diamines in which two or more condensed aromatic rings are substituted with nitrogen atoms (Japanese Patent Application Laid-Open No. 5-234681), 4,4',4"-tris(1-naphthylphenylamino)triphenylamine, etc. Aromatic amine compound having a burst structure (J. Lumin., Volume 72-74, Page 985, 1997), Aromatic amine compound consisting of a tetramer of triphenylamine (Chem. Commun., Page 2175, 1996), 2 Spiro compounds such as ,2',7,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth. Metals, Volume 91, Page 209, 1997), 4,4' -N,N'-dicarbazole derivatives such as biphenyl, etc. Also, examples include polyvinylcarbazole, polyvinyltriphenylamine (Japanese Patent Application Laid-Open No. 7-53953), and tetraphenyl. Polyarylene ether sulfone containing benzidine (Polym. Adv. Tech., Volume 7, Page 33, 1996) can also be preferably used.

(Formation of hole transport layer 4 by wet film forming method)

When forming the hole transport layer 4 by a wet film formation method, the hole transport layer is usually formed in the same manner as in the case of forming the above-described hole injection layer 3 by a wet film formation method, instead of using the composition for forming the hole injection layer. It is formed using a composition.

When forming the hole transport layer 4 by a wet film forming method, the composition for forming the hole transport layer usually further contains a solvent. The solvent used in the composition for forming a hole transport layer can be the same as the solvent used in the composition for forming a hole injection layer described above.

The concentration of the hole transporting compound in the composition for forming a hole transport layer can be 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 deposition method)

In the case of forming the hole transport layer 4 by a vacuum deposition method, it is usually the same as the case of forming the hole injection layer 3 described above by a vacuum deposition method, and instead of the constituent material of the hole injection layer 3, a hole injection layer 3 is used. It can be formed using the constituent materials of the transport layer 4. Film formation conditions such as vacuum degree, deposition rate, and temperature during deposition can be the same as those for vacuum deposition of the hole injection layer 3.

[Luminous layer (5)]

The light-emitting layer 5 is a layer that performs the function of being excited and emitting light when holes injected from the anode 2 and electrons injected from the cathode 9 recombine 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 is on the anode 2, the light-emitting layer 5 is a hole injection layer ( 3) and the cathode 9, and when the hole transport layer 4 is on the anode 2, it is formed between the hole transport layer 4 and the cathode 9.

The film thickness of the light-emitting layer 5 is arbitrary as long as it does not significantly impair the effect of the present invention, but it is preferable to be thick because it is difficult for defects to occur in the film, and on the other hand, it is preferable to be thin because it is easy to achieve a low driving voltage. . For this reason, the film thickness of the light emitting layer 5 is preferably 3 nm or more, more preferably 5 nm or more, usually 200 nm or less, and even more preferably 100 nm or less.

The light-emitting layer 5 contains at least a material (light-emitting material) that has the property of emitting light, and preferably contains a material (charge-transport material) that has charge-transporting properties.

General light-emitting materials and methods for forming the light-emitting layer are described below. However, in the organic electroluminescent device of the present invention, the light-emitting layer is formed by a wet film forming method using the composition for an organic electroluminescent device of the present invention described above. desirable.

Also, as the light-emitting material, an iridium complex, which is an organic metal complex containing iridium as a central element, is preferable, but other light-emitting materials may be used as appropriate.

Hereinafter, light emitting materials other than the iridium complex compound will be described in detail.

(Luminescent material)

The luminescent material is not particularly limited as long as it emits light at a desired luminescent wavelength and does not impair the effect of the present invention, and any known luminescent material can be applied. The luminescent material may be a fluorescent luminescent material or a phosphorescent luminescent material, but a material with good luminous efficiency is preferable, and a phosphorescent luminescent material is preferable from the viewpoint of internal quantum efficiency.

Examples of the fluorescent material include the following materials.

Fluorescent materials that emit blue light (blue fluorescent materials) include, for example, naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis(2-phenylethenyl)benzene, and their derivatives. I can hear it.

Examples of fluorescent materials that impart green light emission (green fluorescent materials) include quinacridone derivatives, coumarin derivatives, and aluminum complexes such as Al(C ₉ H ₆ NO) ₃ .

Examples of fluorescent materials that emit yellow light (yellow fluorescent materials) include rubrene and perimidone derivatives.

Fluorescent materials that emit red light (red fluorescent materials) include, for example, DCM (4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran)-based compounds and benzopyran derivatives. , rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene, etc.

As the phosphorescent material, for example, a material selected from groups 7 to 11 of the long periodic table (hereinafter, unless otherwise specified, the term “periodic table” refers to the long periodic table). and organometallic complexes containing metals. Metals selected from groups 7 to 11 of the periodic table are preferably ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

As the ligand for the organometallic complex, a ligand in which a (hetero)aryl group, such as a (hetero)arylpyridine ligand or a (hetero)arylpyrazole ligand, is linked to a pyridine, pyrazole, or phenanthroline, is preferable, and in particular, a phenylpyridine ligand, Phenylpyrazole ligands are preferred. Here, (hetero)aryl refers to an aryl group or heteroaryl group.

Preferred phosphorescent materials include, specifically, tris(2-phenylpyridine)iridium, tris(2-phenylpyridine)ruthenium, tris(2-phenylpyridine)palladium, bis(2-phenylpyridine)platinum, and tris(2-phenylpyridine)palladium. Phenylpyridine complexes such as phenylpyridine)osmium and tris(2-phenylpyridine)rhenium, and porphyrin complexes such as octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethylpalladiumporphyrin, and octaphenylpalladiumporphyrin.

Polymer-based luminescent materials include poly(9,9-dioctylfluorene-2,7-diyl), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4, 4'-(N-(4-sec-butylphenyl))diphenylamine)], poly[(9,9-dioctylfluorene-2,7-diyl)-co-(1,4-benzo-2 {2,1'-3}-triazole)], polyfluorene-based materials, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], etc. Examples include polyphenylene vinylene-based materials.

(charge transport material)

The charge-transporting material is a material having positive charge (hole) or negative charge (electron) transportability. There is no particular limitation, and any known material can be applied as long as it does not impair the effect of the present invention.

As the charge-transporting material, compounds conventionally used in the light-emitting layer 5 of an organic electroluminescent device can be used. In particular, compounds used as a host material for the light-emitting layer 5 are preferable.

The charge transport material specifically includes aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, and compounds in which a tertiary amine is linked to a fluorene group. , compounds exemplified as hole transport compounds of the hole injection layer 3, such as hydrazone-based compounds, silazane-based compounds, silanamine-based compounds, phosphamine-based compounds, and quinacridone-based compounds. In addition, electron transport compounds such as anthracene-based compounds, pyrene-based compounds, carbazole-based compounds, pyridine-based compounds, phenanthroline-based compounds, oxadiazole-based compounds, and silol-based compounds can be mentioned.

In addition, the charge transport material includes, for example, two or more tertiary amines such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, and two or more tertiary amines. Aromatics with a starburst structure, such as aromatic diamines in which the condensed aromatic ring is replaced with a nitrogen atom (Japanese Patent Application Laid-Open No. 5-234681), 4,4',4"-tris(1-naphthylphenylamino)triphenylamine, etc. Amine compound (J. Lumin., Volume 72-74, Page 985, 1997), Aromatic amine compound consisting of a tetramer of triphenylamine (Chem. Commun., Page 2175, 1996), 2,2' , 7,7'-Tetrakis-(diphenylamino)-9,9'-spirobifluorene and other fluorene compounds (Synth. Metals, Volume 91, Page 209, 1997), 4,4'- Compounds exemplified as hole-transporting compounds of the hole-transporting layer 4, such as carbazole-based compounds such as N,N'-dicarbazolbiphenyl, can also be preferably used. In addition, 2-(4-biphenylyl )-5-(p-tertiarybutylphenyl)-1,3,4-oxadiazole (tBu-PBD), 2,5-bis(1-naphthyl)-1,3,4-oxadiazole ( Oxadiazole-based compounds such as BND), 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilol (PyPySPyPy), etc. Also included are phenanthroline-based compounds such as rol-based compounds, vasophenanthroline (BPhen), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, vasocuproin).

(Formation of light-emitting layer 5 by wet film forming method)

The method for forming the light emitting layer 5 may be a vacuum deposition method or a wet film forming method, but the wet film forming method is preferable because of excellent film forming properties.

When forming the light-emitting layer 5 by a wet film forming method, normally, in the same manner as in the case of forming the above-mentioned hole injection layer 3 by a wet film forming method, instead of the composition for forming the hole injection layer, the light emitting layer ( 5) It is formed using a composition for forming a light-emitting layer prepared by mixing the above materials with a soluble solvent (solvent for the light-emitting layer).

In the present invention, it is preferable to use the composition for an organic electroluminescent device of the present invention described above as the composition for forming the light emitting layer.

Solvents include, for example, ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and amide-based solvents mentioned for the formation of the hole injection layer 3, as well as alkane-based solvents, halogenated aromatic hydrocarbon-based solvents, and aliphatic alcohol-based solvents. Solvents, alicyclic alcohol-based solvents, aliphatic ketone-based solvents, and alicyclic ketone-based solvents can be mentioned. Preferred solvents are as exemplified as aliphatic ester solvents, aromatic diester solvents, and other solvents having two or more carbonyl groups contained in the composition for an organic electroluminescent device of the present invention.

The amount of solvent used is arbitrary as long as it does not significantly impair the effect of the present invention. The total content in the composition for forming a light-emitting layer is preferably large because it has low viscosity and makes it easy to form a film, and is preferably small because it is easy to form a thick film. As described above, the solvent content of the composition for forming an emitting layer is preferably 1 mass% or more, more preferably 10 mass% or more, particularly preferably 50 mass% or more, and preferably 99.99 mass% or less. , more preferably 99.9 mass% or less, particularly preferably 99 mass% or less.

Heating or reduced pressure can be used as a solvent removal method after wet film formation. The heating means used in the heating method is preferably a clean oven or a hot plate because it applies heat evenly to the entire film. The heating temperature in the heating process is arbitrary as long as it does not significantly impair the effect of the present invention, but a higher temperature is preferable in terms of shortening the drying time, and a lower temperature is preferable in that it causes less damage to the material. The upper limit of the heating temperature is usually 250°C or lower, preferably 200°C or lower, and more preferably 150°C or lower. The lower limit of the heating temperature is usually 30°C or higher, preferably 50°C or higher, and more preferably 80°C or higher. Temperatures exceeding the above upper limit are undesirable because they are higher than the heat resistance of commonly used charge-transporting materials or phosphorescent materials, and may cause decomposition or crystallization. Temperatures below the above lower limit are not preferable because removal of the solvent requires a long time. The heating time in the heating process is appropriately determined depending on the boiling point or vapor pressure of the solvent in the composition for forming a light-emitting layer, the heat resistance of the material, and heating conditions.

(Formation of light-emitting layer 5 by vacuum deposition method)

When forming the light-emitting layer 5 by a vacuum deposition method, usually one or two or more types of constituent materials of the light-emitting layer 5 (the above-mentioned light-emitting material, charge-transporting compound, etc.) are placed in a crucible installed in a vacuum container ( When two or more types of materials are used, each is usually placed in a different crucible), the inside of the vacuum container is evacuated to about 10 ^-4 Pa with a vacuum pump, and then the crucible is heated (when two or more types of materials are used) , usually by heating each crucible), evaporate while controlling the evaporation amount of the material in the crucible (when using two or more types of materials, usually evaporate while controlling the evaporation amount independently), and inject holes placed facing the crucibles. The light-emitting layer (5) is formed on the layer (3) or the hole transport layer (4). When two or more types of materials are used, the light-emitting layer 5 may be formed by placing their mixture in a crucible, heating, and evaporating.

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

[Hole blocking layer (6)]

A hole blocking layer 6 may be formed 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 on the cathode 9 side of the light emitting layer 5.

The hole blocking layer (6) serves to prevent holes moving from the anode (2) from reaching the cathode (9) and to efficiently transport electrons injected from the cathode (9) in the direction of the light emitting layer (5). It has a role. The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility and low hole mobility, a large energy gap (difference between HOMO and LUMO), and an excitation triplet level (T1). You can lift something high.

Materials for the hole blocking layer 6 that satisfy these conditions include, for example, bis(2-methyl-8-quinolinolato)(phenolato)aluminum, bis(2-methyl-8-quinoli), and Mixed ligand complexes such as nolato)(triphenylsilanolato)aluminum, bis(2-methyl-8-quinolinolato)aluminum-μ-oxo-bis-(2-methyl-8-quinolinolato)aluminum Metal complexes such as dinuclear metal complexes, styryl compounds such as distyrylbiphenyl derivatives (Japanese Patent Application Laid-Open No. 11-242996), 3-(4-biphenylyl)-4-phenyl-5(4-tert- Triazole derivatives such as butylphenyl)-1,2,4-triazole (Japanese Patent Application Laid-open No. 7-41759), phenanthroline derivatives such as vasocuproin (Japanese Patent Application Laid-Open No. 10-79297) etc. can be mentioned. Additionally, compounds having at least one pyridine ring substituted at the 2, 4, and 6 positions described in International Publication No. 2005/022962 are also preferable as a material for the hole blocking layer 6.

There is no limitation to the method of forming the hole blocking layer 6, and it can be formed in the same manner as the method of forming the light emitting layer 5 described above.

The film thickness of the hole blocking layer 6 is arbitrary as long as it does not significantly impair the effect of the present invention, but is usually 0.3 nm or more, preferably 0.5 nm or more, and is usually 100 nm or less, preferably 50 nm or less. .

[Electron transport layer (7)]

The electron transport layer 7 is formed between the light emitting layer 5 or the hole blocking layer 6 and the electron injection layer 8 for the purpose of further improving the current efficiency of the device.

The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode 9 in the direction of the light emitting layer 5 between electrodes to which an electric field is applied. The electron transport compound used in the electron transport layer 7 has a high electron injection efficiency from the cathode 9 or the electron injection layer 8, and has high electron mobility and can efficiently transport the injected electrons. It is necessary to have a compound that exists.

Electron-transporting compounds that satisfy these conditions include, specifically, metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Application Laid-Open No. 59-194393), 10-hydroxybenzo[ h]metal complex of quinoline, oxadiazole derivative, distyrylbiphenyl derivative, silol derivative, 3-hydroxyflavone metal complex, 5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenz Imidazolylbenzene (US Patent No. 5645948 specification), quinoxaline compound (Japanese Patent Application Laid-Open No. 6-207169), phenanthroline derivative (Japanese Patent Application Laid-Open No. 5-331459), 2-t-butyl- Examples include 9,10-N,N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide.

The film thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more, and is usually 300 nm or less, preferably 100 nm or less.

The electron transport layer 7 is formed in the same manner as the light emitting layer 5 by laminating it on the light emitting layer 5 or the hole blocking layer 6 by a wet film forming method or a vacuum evaporation method. Usually, a vacuum deposition method is used.

[Electron injection layer (8)]

The electron injection layer 8 serves to efficiently inject 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. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium.

The film thickness of the electron injection layer 8 is preferably 0.1 to 5 nm.

An ultra-thin insulating film (about 0.1 to 5 nm thick) such as LiF, MgF ₂ , Li ₂ O, or Cs ₂ CO ₃ is inserted as the electron injection layer 8 at the interface between the cathode 9 and the electron transport layer 7. It is also an effective way to improve the efficiency of devices (Appl. Phys. Lett., Volume 70, Page 152, 1997; Japanese Patent Publication No. 10-74586; IEEE Trans. Electron. Devices, Volume 44, Page 1245, 1997; SID 04 Digest, page 154).

Additionally, organic electron transport materials such as nitrogen-containing heterocyclic compounds such as vasophenanthroline and metal complexes such as aluminum complexes of 8-hydroxyquinoline are doped with alkali metals such as sodium, potassium, cesium, lithium, and rubidium. As a result (described in Japanese Patent Application Laid-Open No. 10-270171, Japanese Patent Application Publication No. 2002-100478, Japanese Patent Application Publication No. 2002-100482, etc.), electron injection and transport properties are improved, making it possible to achieve both excellent film quality. desirable. The film thickness in this case is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

The electron injection layer 8 is formed by laminating the light emitting layer 5 or the hole blocking layer 6 or electron transport layer 7 thereon by a wet film forming method or a vacuum evaporation method in the same manner as the light emitting layer 5. do.

The details in the case of the wet film forming method are the same as in the case of the above-described light-emitting layer 5.

[Cathode (9)]

The cathode 9 serves to inject electrons into a layer on the light-emitting layer 5 side (electron injection layer 8 or light-emitting layer 5, etc.). As the material for the cathode 9, it is possible to use the material used for the anode 2, but in order to efficiently inject electrons, it is preferable to use a metal with a low work function. As metals with a low work function, for example, metals such as tin, magnesium, indium, calcium, aluminum, silver, or alloys thereof are used. Specific examples include alloy electrodes with low work functions, such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

In terms of device stability, it is desirable to protect the cathode 9 made of a metal with a low work function by laminating a metal layer with a high work function and stable to the atmosphere on the cathode 9. 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 constituent layers]

Although the description has been made focusing on the element having the layer structure shown in FIG. 1, between the anode 2 and the cathode 9 and the light emitting layer 5 in the organic electroluminescent device of the present invention, there is a layer that does not impair the performance. As long as it is possible to have any layers in addition to the layers described above. Additionally, any layer other than the light-emitting layer 5 may be omitted.

For example, for the same purpose as the hole blocking layer 6, it is also effective to form an electron blocking layer between the hole transport layer 4 and the light emitting layer 5. The electron blocking layer prevents electrons moving from the light-emitting layer (5) from reaching the hole transport layer (4), thereby increasing the probability of recombination with holes in the light-emitting layer (5) and trapping the generated excitons in the light-emitting layer (5). has a role of efficiently transporting holes injected from the hole transport layer 4 in the direction of the light emitting layer 5.

Characteristics required for the electron blocking layer include high hole transport, a large energy gap (difference between HOMO and LUMO), and a high triplet excitation level (T1).

When the light emitting layer 5 is formed 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 manufacturing becomes easier.

For this reason, it is desirable that the electron blocking layer also has wet film forming compatibility, and materials used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine represented by F8-TFB (International Publication No. 2004) /084260), etc.

A structure opposite to that of Figure 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), and a hole transport layer (4) on the substrate (1). ), the hole injection layer (3), and the anode (2) may be laminated in that order. It is also possible to form the organic electroluminescent device of the present invention between two substrates, at least one of which has high transparency.

The layer structure shown in FIG. 1 can also be a multi-stage overlapping structure (a structure in which multiple light-emitting units are stacked). In that case, if, for example, V ₂ O ₅ or the like is used as a charge generation layer instead of the interface layer between stages (between light-emitting units) (the two layers if the anode is ITO and the cathode is Al), the barrier between stages is reduced. , it is more preferable from the viewpoint of luminous efficiency and driving voltage.

The present invention can be applied to any of the organic electroluminescent devices: a single device, a device with a structure in which an anode and a cathode are arranged in an array, and a structure in which an anode and a cathode are arranged in an X-Y matrix.

〔Display device and lighting device〕

The display device and lighting device of the present invention use the organic electroluminescent element of the present invention as described above. There are no particular restrictions on the form or structure of the display device and lighting device of the present invention, and they can be assembled by conventional methods using the organic electroluminescent device of the present invention.

For example, the display device and lighting device of the present invention can be formed by the method described in “Organic EL Display” (published by Ohm Corporation on August 20, 2016, by Shizuo Tokito, Chihaya Adachi, and Hideyuki Murata). You can.

Example

Hereinafter, the present invention will be described in more detail by referring to examples. The present invention is not limited to the following examples. The present invention may be implemented with any modification as long as it does not deviate from the gist of the invention.

[Preparation of ink]

[Example 1]

Compound 1 (charge transport material) having a structure represented by the following formula (7) and Compound 2 (light-emitting material) having a structure represented by the following formula (8) were mixed at a mass ratio of 80:20 to obtain light-emitting layer material 1. To the light-emitting layer material 1, 2,6-di-tert-butylphenol (BHB) equivalent to 2 mass% was added, and cyclopentanone-2- was added so that the light-emitting layer material 1 was 2.5 mass% based on the total amount of ink. Methyl carboxylate was added (BHB concentration 500 ppm).

After replacing the atmosphere in the container with nitrogen, the ink was dissolved by heating and stirring at 68°C for 1 hour to produce light-emitting layer ink 1.

[Formula 33]

[Example 2]

Emissive layer ink 2 was produced in the same manner as in Example 1, except that dimethyl phthalate was added instead of methyl cyclopentanone-2-carboxylate.

[Comparative Example 1]

Emissive layer ink 3 was produced in the same manner as in Example 1, except that benzyl benzoate was added instead of methyl cyclopentanone-2-carboxylate.

[Measurement of surface tension]

The surface tension was measured by the 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 10 seconds later was photographed. Using the analysis software FAMAS, the surface tension was calculated from this shape by the Fitting-Laplace method.

For each ink, the production and measurement of droplets were repeated 10 times each, and the average was taken as the surface tension of the ink.

〔Measurement and storage〕

After producing each emitting layer ink, the vial of the nitrogen-filled ink container was cooled to room temperature. The vial was opened to the atmosphere, half the ink was immediately taken, and the first surface tension measurement was performed (initial surface tension). The remaining half amount of ink was resealed in an atmospheric atmosphere and stored in a room temperature environment for 28 days. Afterwards, a second surface tension measurement was performed using the stored ink (surface tension after 28 days).

[Surface tension measurement results]

For the emitting layer inks of Examples 1 and 2 and Comparative Example 1, the measured values of surface tension and the amount of change at the initial stage and after 28 days are shown in Table 1.

As shown in Table 1, in the ink containing a specific phenol derivative, by using an aliphatic ester solvent or an aromatic diester solvent having two or more carbonyl groups, the change in surface tension of the ink during long-term storage is reduced, thereby improving stability. This high-performance composition for an organic electroluminescent device was obtained.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various changes can be made without departing from the intent and scope of the present invention.

This application is based on Japanese Patent Application 2021-078651 filed on May 6, 2021 and Japanese Patent Application 2021-078652 filed on May 6, 2021, which are incorporated by reference in their entirety.

1: substrate
2: anode
3: hole injection layer
4: hole transport layer
5: light emitting layer
6: hole blocking layer
7: electron transport layer
8: electron injection layer
9: cathode
10: Organic electroluminescent device

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 above formula, a is an integer of 0 to 4. R ¹ and R ² each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. When a is an integer of 2 to 4, plural R ² may be the same or different.] According to claim 1,
A composition for an organic electroluminescent device wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having two ester groups. According to claim 1,
A composition for an organic electroluminescent device wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having one ester group and one ketone group. According to claim 1,
A composition for an organic electroluminescent device wherein the aliphatic ester solvent having two or more carbonyl groups is a solvent represented by the following formula (9-1) or the following formula (9-2).

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

[In the above 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 combine with each other to form a ring.] According to claim 4,
A composition for an organic electroluminescent device wherein the aromatic diester solvent is a solvent represented by the following formula (9-3).

[In the above formula, Ar ³¹ represents an arylene group. R ^30a and R ^30b each independently represent an alkyl group. R ^30a and Ar ³¹ may combine with each other to form a ring.] The method according to any one of claims 1 to 5,
A composition for an organic electroluminescent device wherein the compound represented by the above formula (1) is a compound represented by the following formula (1-1).

[In the above formula, b is an integer of 0 to 3. R ³ , R ⁴ , and R ⁵ each independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. When b is an integer of 2 to 3, a plurality of R ⁵ may be the same or different.] According to claim 6,
A composition for an organic electroluminescent device wherein the compound represented by the above formula (1-1) is a compound represented by the following formula (1-2).

[In the above formula, b, R ⁵ have the same meaning as b, R ⁵ in the above formula (1-1).] The method according to any one of claims 1 to 7,
A composition for an organic electroluminescent device comprising an iridium complex as the functional material. According to claim 8,
A composition for an organic electroluminescent device containing an iridium complex represented by the following formula (2) as the functional material.

[In the above formula, R ⁷ and R ⁸ are each independently an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, or (hetero) with 3 to 20 carbon atoms. Aryloxy group, alkylsilyl group with 1 to 20 carbon atoms, arylsilyl group with 6 to 20 carbon atoms, alkylcarbonyl group with 2 to 20 carbon atoms, arylcarbonyl group with 7 to 20 carbon atoms, alkylamino group with 1 to 20 carbon atoms, 6 to 20 carbon atoms arylamino group, and (hetero)aryl group having 3 to 30 carbon atoms, or a combination thereof. These groups may further have a substituent. When a plurality of R ⁷ and R ⁸ exist, the plurality of R ⁷ and R ⁸ may be the same or different. Neighboring R ⁷ or R ⁸ bonded to the benzene ring may be bonded to each other to form a ring condensed to the benzene ring.
d is an integer from 0 to 4.
e is an integer from 0 to 3.
m is an integer from 1 to 20.
n is an integer from 0 to 2.
Ring A is a pyridine ring, a pyrazine ring, a pyrimidine ring, an imidazole ring, an oxazole ring, a thiazole ring, a quinoline ring, an isoquinoline ring, a quinazoline ring, a quinoxaline ring, an azatriphenylene ring, and a carboline ring. Which one of them?
Ring A may have a substituent, and the substituent is a fluorine atom, a chlorine atom, a bromine atom, an alkyl group with 1 to 20 carbon atoms, a (hetero)aralkyl group with 7 to 40 carbon atoms, an alkoxy group with 1 to 20 carbon atoms, and a carbon number. (hetero)aryloxy group of 3 to 20 carbon atoms, alkylsilyl group of 1 to 20 carbon atoms, arylsilyl group of 6 to 20 carbon atoms, alkylcarbonyl group of 2 to 20 carbon atoms, arylcarbonyl group of 7 to 20 carbon atoms, 2 to 20 carbon atoms It is any of an alkylamino group, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 20 carbon atoms, or a combination thereof. Neighboring substituents bonded to ring A may combine to form a ring condensed to ring A.
Z ¹ represents a direct bond or an m+1 valent aromatic linking group.
L ¹ represents an auxiliary ligand. l is an integer from 1 to 3. When there are multiple auxiliary ligands, they may be different or the same.] According to clause 9,
A composition for an organic electroluminescent device, wherein Z ¹ contains a trivalent group represented by the following formula (2-2A) or (2-2B).

A method for producing 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 claims 1 to 10. An organic electroluminescent device having a light-emitting layer formed using the composition for an organic electroluminescent device according to any one of claims 1 to 10. A display device having the organic electroluminescent element according to claim 12. A lighting device having the organic electroluminescent element according to claim 12.

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