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

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent element composition useful for forming the light-emitting layer of an organic electroluminescent element (hereinafter sometimes referred to as an "organic EL element"). The present invention also relates to an organic electroluminescent element having a light-emitting layer formed using the organic electroluminescent element composition, a method for manufacturing the same, and a display device and lighting device having the organic electroluminescent element. [Background technology]

[0002] Various electronic devices utilizing organic electroluminescent (OLED) elements, such as OLED lighting and OLED displays, have been put into practical use. Because organic electroluminescent elements (OLEDs) consume little power due to the low applied voltage, they can also emit light in all three primary colors. For this reason, their application is beginning not only in large display monitors but also in small and medium-sized displays, such as those found in mobile phones and smartphones.

[0003] Organic electroluminescent devices are manufactured by stacking multiple layers, such as an emissive layer, a charge injection layer, and a charge transport layer. Currently, most organic electroluminescent devices are manufactured by depositing organic materials under vacuum. However, the vacuum deposition method is complicated and has low productivity. Furthermore, it is extremely difficult to produce large-area lighting and display panels using organic electroluminescent devices manufactured by the vacuum deposition method.

[0004] In recent years, wet deposition (coating) has been studied as an efficient process for manufacturing organic electroluminescent devices that can be used in large displays and lighting. Wet deposition has the advantage of easily forming stable layers compared to vacuum deposition. For this reason, it is expected to be used for mass production of displays and lighting devices, as well as for application to large devices.

[0005] To manufacture organic electroluminescent devices using the wet deposition method, functional materials must be dissolved in an organic solvent and used as an ink. If the functional materials have low solubility in organic solvents, operations such as prolonged heating may be required, potentially causing the materials to degrade before use. Furthermore, if a uniform state cannot be maintained in the solution for an extended period, precipitation of the material will occur from the solution, making film formation using inkjet devices or similar equipment impossible. The organic solvents used in inks require solubility in two senses: to quickly dissolve the functional materials, and to maintain a uniform state without precipitating the functional materials after dissolution.

[0006] In recent years, attempts have been made to include phenol derivatives in inks with the aim of suppressing the decrease in luminous efficiency and operating life of organic electroluminescent devices even when the organic electroluminescent device is manufactured after the ink has been stored for a long period of time (for example, Patent Documents 1 and 2).

[0007] It has been disclosed that aromatic esters are used as organic solvents in inks to improve the flatness of films formed by wet film deposition (for example, Patent Document 3).

[0008] [Patent Document 1] Japanese Patent Publication No. 2015-63662 [Patent Document 2] Japanese Patent Publication No. 2015-93938 [Patent Document 3] International Publication No. 2019 / 212022

[0009] As described above, by incorporating phenol derivatives into the ink, it is now possible to suppress the degradation of functional materials, which is one of the causes of decreased luminescence efficiency and operating life, even when the ink is stored for a long period of time. However, the stability of the ink's liquid properties, particularly its surface tension stability, was insufficient, and improvements in liquid property stability were needed. [Overview of the project]

[0010] The object of the present invention is to provide an organic electroluminescent device composition with improved liquid stability, particularly the surface tension stability of the ink, for forming the light-emitting layer of the organic electroluminescent device by wet film deposition.

[0011] The inventors have found that by using an aliphatic ester and / or aromatic diester solvent having two or more carbonyl groups as the solvent, changes in liquid properties are reduced even when a phenol derivative is included.

[0012] The gist of this invention is as follows:

[0013] [1] A composition for an organic electroluminescent element comprising a functional material, a compound represented by the following formula (1), and an aliphatic ester solvent and / or aromatic diester solvent having two or more carbonyl groups.

[0014] [ka]

[0015] [In the above formula, a is an integer from 0 to 4, R 1 , R 2 Each independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When a is an integer from 2 to 4, multiple R 2 They may be the same or they may be different.

[0016] [2] The organic electroluminescent element composition according to [1], wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having two ester groups.

[0017] [3] The organic electroluminescent element composition 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.

[0018] [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).

[0019]

Chemical formula

[0020] [In the above formula, R 24 represents an alkylene group. R 25 , R 26 each independently represents an alkyl group. R 24 and R 25 may be bonded to each other to form a ring.]

[0021]

Chemical formula

[0022] [In the above formula, R 27 represents an alkylene group. R 28 , R 29 each independently represents an alkyl group. R 27 and R 28 , or, R 27 and R 29 may be bonded to each other to form a ring.]

[0023] [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).

[0024]

Chemical formula

[0025] [In the above formula, Ar 31 represents an arylene group. R 30a , R 30b each independently represents an alkyl group. R 30a y]] and Ar 31 may be bonded to each other to form a ring.]

[0026] [6] The organic electroluminescent element composition according to any one of [1] to [5], wherein the compound represented by formula (1) is the compound represented by the following formula (1-1).

[0027] [ka]

[0028] [In the above formula, b is an integer from 0 to 3. R 3 , R 4 , R 5 Each of these independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When b is an integer between 2 and 3, multiple R groups are represented. 5 They may be the same or they may be different.

[0029] [7] The organic electroluminescent element composition according to [6], wherein the compound represented by formula (1-1) is the compound represented by the following formula (1-2).

[0030] [ka]

[0031] [In the above formula, b, R 5 b, R in the above formula (1-1) are 5 This is synonymous with [the above].

[0032] [8] The organic electroluminescent element composition according to any one of [1] to [7], comprising an iridium complex as the functional material.

[0033] [9] The organic electroluminescent element composition according to [8], comprising an iridium complex represented by the following formula (2) as the functional material.

[0034] [ka]

[0035] [In the above formula, R 7 , R 8 Each of these groups is independently one or a combination of the following: an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 30 carbon atoms. These groups may also have substituents. 7 , R 8 If multiple R 7 , R 8 They may be the same or different. Adjacent R atoms bonded to the benzene ring. 7 or R 8 These elements may be bonded to each other to form a ring that condenses around the benzene ring. d is an integer between 0 and 4. e is an integer between 0 and 3. m is an integer between 1 and 20. n is an integer between 0 and 2. Ring A is one of the following: pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, oxazole ring, thiazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, or carboline ring. Ring A may have substituents, which may be any of the following, or combinations thereof: a fluorine atom, a chlorine atom, a bromine atom, a C1-C20 alkyl group, a C7-C40 (hetero)aralkyl group, a C1-C20 alkoxy group, a C3-C20 (hetero)aryloxy group, a C1-C20 alkylsilyl group, a C6-C20 arylsilyl group, a C2-C20 alkylcarbonyl group, a C7-C20 arylcarbonyl group, a C2-C20 alkylamino group, a C6-C20 arylamino group, and a C3-C20 (hetero)aryl group. Adjacent substituents bonded to ring A may bond to each other to form a condensed ring with ring A. Z 1 This represents a directly bonded or m+1 valent aromatic linking group. L 1 represents an auxiliary ligand. l is an integer between 1 and 3. If there are multiple auxiliary ligands, they may be different or identical.

[0036]

[10] Said Z 1 The organic electroluminescent element composition according to [9], comprising a trivalent group represented by the following formula (2-2A) or (2-2B).

[0037] [ka]

[0038] A method for manufacturing an organic electroluminescent element, comprising the step of forming a light-emitting layer by a wet film deposition method using an organic electroluminescent element composition described in any of

[11] [1] to

[10] .

[0039] An organic electroluminescent element having a light-emitting layer formed using an organic electroluminescent element composition described in any of

[12] [1] to

[10] .

[0040] A display device having the organic electroluminescent element described in

[13]

[12] .

[0041] A lighting device having the organic electroluminescent element described in

[14] and

[12] . [Effects of the Invention]

[0042] The organic electroluminescent element composition of the present invention exhibits excellent stability of liquid properties, particularly the surface tension stability of the ink. Therefore, even when the organic electroluminescent element composition of the present invention is used to manufacture an organic electroluminescent element after long-term storage, the decrease in luminous efficiency and operating life is small, and furthermore, because the change in liquid properties is small, it is possible to obtain a display device or lighting device with less uniformity. In other words, the organic electroluminescent element composition of the present invention is applicable to large-area coating and is a composition that can be stored for a long period of time.

[0043] In the present invention, the mechanism by which such effects are obtained is presumed to be as follows. The organic electroluminescent element composition of the present invention contains a compound represented by formula (1), which is a phenol derivative, and therefore suppresses the deterioration of the functional material even when the ink is stored for a long time. Furthermore, because it contains an aliphatic ester and / or aromatic diester solvent having two or more carbonyl groups as a solvent, it is possible to reduce the change in liquid properties due to the oxidation of the phenol derivative.

[0044] While the inclusion of phenol derivatives in ink suppresses the degradation of functional materials due to oxidation, the phenol derivatives themselves are thought to be oxidized. When phenols are oxidized, they typically undergo one-electron oxidation followed by proton transfer or hydrogen atom transfer to become phenoxy radicals. It is unclear whether these phenoxy radicals then transform into other substances such as benzoquinones or peroxides in the ink, but in any case, the resulting structure lacks a phenolic hydroxyl group. Phenolic hydroxyl groups exhibit hydrogen bonding properties and acidity due to the resonance effect of aromatic rings, but these properties are thought to change significantly upon oxidation.

[0045] As described above, the structural changes caused by the oxidation of phenol derivatives can affect the liquid properties of the ink, even if the phenol derivative content is small. However, by including an aliphatic ester and / or aromatic diester solvent having two or more polar carbonyl groups as the solvent, it is possible to suppress this change in liquid properties. [Brief explanation of the drawing]

[0046] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the structure of the organic electroluminescent element of the present invention. [Modes for carrying out the invention]

[0047] The embodiments of the present invention will be described in detail below. The present invention is not limited to the embodiments described below, and can be implemented in various ways within the scope of its gist.

[0048] In this specification, (hetero)aralkyl group, (hetero)aryloxy group, and (hetero)aryl group refer to an aralkyl group which may contain a heteroatom, an aryloxy group which may contain a heteroatom, and an aryl group which may contain a heteroatom, respectively. "May contain heteroatoms" means that one or more carbon atoms among the carbon atoms forming the main skeleton of the aryl group, aralkyl group, or aryloxy group are substituted with heteroatoms. Examples of heteroatoms include nitrogen, oxygen, sulfur, phosphorus, and silicon atoms. Among these, nitrogen atoms are preferred from the viewpoint of durability. The same applies to the (hetero)arylene group.

[0049] In this specification, "aromatic linking group" refers to a broad range of aromatic linking groups, including not only aromatic hydrocarbon linking groups, i.e., linking groups having an aromatic hydrocarbon ring, but also heteroaromatic linking groups, i.e., linking groups having a heteroaromatic ring.

[0050] [Composition for Organic Electroluminescent Devices] The present invention provides an organic electroluminescent element composition comprising a functional material, a compound represented by the following formula (1), and an aliphatic ester solvent and / or aromatic diester solvent having two or more carbonyl groups.

[0051] [ka]

[0052] [In the above formula, a is an integer from 0 to 4. R 1 , R 2 Each independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When a is an integer from 2 to 4, multiple R 2They may be the same or they may be different.

[0053] [Functional materials] The organic electroluminescent element composition of the present invention includes a functional material. The functional material is a light-emitting material or a charge-transporting material contained in the light-emitting layer of the organic electroluminescent element.

[0054] The organic electroluminescent light-emitting composition of the present invention preferably contains a phosphorescent organometallic complex as a functional material, and more preferably contains an iridium complex, which is an organometallic complex with iridium as the central element, in order to allow the energy of the excited triplet state to contribute to light emission.

[0055] [Iridium complex] The iridium complex contained in the organic electroluminescent element composition of the present invention is preferably represented by the following formula (2) in terms of its high solubility in organic solvents and heat resistance.

[0056] [ka]

[0057] [In the above formula, R 7 , R 8 Each of these groups is independently one or a combination of the following: an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 30 carbon atoms. These groups may also have substituents. 7 , R 8 If multiple R 7 , R 8 They may be the same or different. Adjacent R atoms bonded to the benzene ring. 7 or R 8These elements may be bonded to each other to form a ring that condenses around the benzene ring. d is an integer between 0 and 4. e is an integer between 0 and 3. m is an integer between 1 and 20. n is an integer between 0 and 2. Ring A is one of the following: pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, oxazole ring, thiazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, or carboline ring. Ring A may have substituents, which may be any of the following, or combinations thereof: a fluorine atom, a chlorine atom, a bromine atom, a C1-C20 alkyl group, a C7-C40 (hetero)aralkyl group, a C1-C20 alkoxy group, a C3-C20 (hetero)aryloxy group, a C1-C20 alkylsilyl group, a C6-C20 arylsilyl group, a C2-C20 alkylcarbonyl group, a C7-C20 arylcarbonyl group, a C2-C20 alkylamino group, a C6-C20 arylamino group, and a C3-C20 (hetero)aryl group. Adjacent substituents bonded to ring A may bond to each other to form a condensed ring with ring A. Z 1 This represents a directly bonded or m+1 valent aromatic linking group. L 1 represents an auxiliary ligand. l is an integer between 1 and 3. If there are multiple auxiliary ligands, they may be different or identical.

[0058] In equation (1), R 7 , R 8 From the standpoint of durability, each of these is preferably an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, an arylamino group having 6 to 20 carbon atoms, or a (hetero)aryl group having 3 to 30 carbon atoms, and more preferably 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.

[0059] Two adjacent R7 Allies, R 8 These groups may be linked together to form a ring that is fused to the benzene ring to which these groups are bonded.

[0060] d is preferably 0 for ease of manufacturing. d is preferably 1 or 2, and more preferably 1, for improved solubility. Two adjacent R 7 When the elements are connected to each other to form a ring, it is preferable that d is 2.

[0061] e is preferably 0 for ease of manufacturing. e is preferably 1 or 2, and more preferably 1, for improved durability and solubility. Two adjacent R 8 When the elements are connected to each other to form a ring, e is preferably 2 or 3.

[0062] R 7 ,R 8 If the compound further has substituents, these substituents may be any of the following, or combinations thereof: a fluorine atom, a chlorine atom, a bromine atom, a C1-C20 alkyl group, a C7-C40 (hetero)aralkyl group, a C1-C20 alkoxy group, a C3-C20 (hetero)aryloxy group, a C1-C20 alkylsilyl group, a C6-C20 arylsilyl group, a C2-C20 alkylcarbonyl group, a C7-C20 arylcarbonyl group, a C2-C20 alkylamino group, a C6-C20 arylamino group, and a C3-C20 (hetero)aryl group.

[0063] Since phenyl groups with t-butyl groups at their terminals enhance solubility in organic solvents, it is preferable that m be 2 or greater. However, because phenyl groups with t-butyl groups at their terminals have little involvement in charge transport or luminescence, too many of them may lead to increased driving voltage or decreased luminescence efficiency. For this reason, it is preferable that m be 8 or less, and more preferably 4 or less.

[0064] In iridium complexes represented by formula (2), it is preferable that the total number of such terminal t-butyl groups is 4 or more, particularly 6 or more, and 48 or less, particularly 24 or less, in terms of achieving both solubility, low driving voltage, and high luminescence efficiency.

[0065] n is preferably 0 or 1 because it is easy to manufacture. n is preferably 0 because there is little concern about the drive voltage becoming high. n is preferably 1 or 2 because solubility can be improved.

[0066] From the viewpoint of durability, ring A is preferably a pyridine ring, a pyrimidine ring, or an imidazole ring, and more preferably a pyridine ring.

[0067] The hydrogen atoms on ring A are preferably substituted with C1-C20 alkyl groups, C7-C40 (hetero)aralkyl groups, or C3-C20 (hetero)aryl groups, in terms of durability and improved solubility. It is preferable that the hydrogen atoms on ring A are not substituted, as this facilitates manufacturing. It is preferable that the hydrogen atoms on ring A are substituted with a phenyl group or naphthyl group, which may have substituents, because this facilitates exciton generation when used in an organic electroluminescent device, thereby increasing the luminescence efficiency.

[0068] Ring A is useful for red emission applications because the emission wavelength is longer when substituents on ring A bond to each other and form fused rings, such as quinoline rings, isoquinoline rings, quinazoline rings, quinoxaline rings, azatriphenylene rings, and carboline rings. In particular, ring A that forms quinoline rings, isoquinoline rings, and quinazoline rings is preferred in terms of durability and exhibiting red emission.

[0069] Z 1 Direct bonding is preferable because it is easier to manufacture. Z 1 It is preferable that the aromatic linking group is in the m+1 valence state, as this reduces the concern about the driving voltage becoming too high.

[0070] If m is 1, then Z 1 In terms of durability, phenylene groups, biphenylene groups, terphenylene groups, and fluoroorangeyl groups are preferred, with p-phenylene groups being particularly preferred.

[0071] If m is 2 or greater, Z 1 In terms of durability, it is preferable that the material contains a benzene ring with the bonded position at the 1,3,5-position or a triazine ring with the bonded position at the 2,4,6-position.

[0072] Z 1 It is preferable that it contains a trivalent group represented by the following formula (2-2A) or (2-2B).

[0073] [ka]

[0074] It is even more preferable that the group represented by formula (2-2A) or (2-2B) is bonded to iridium, specifically to a benzene ring or ring A.

[0075] L 1 is an auxiliary ligand. There are no particular restrictions, but L 1 The ligand is preferably a monovalent bidentate ligand, and more preferably selected from ligands represented by the following formulas (2A), (2B), and (2C). In equations (2A) to (2C) below, the dashed lines represent coordinate covalent bonds. l is 1 and there are two auxiliary ligands L 1 If present, auxiliary ligand L 1 These elements may be identical to each other, or they may have different structures. When l is 3, L 1 It does not exist.

[0076] [ka]

[0077] In the above formulas (2A) and (2B), R9 , R 10 is the aforementioned R 7 , R 8 The preferred examples are selected from a similar group, and the same applies to the preferred examples.

[0078] g is an integer between 0 and 4. h is an integer between 0 and 4. g and h are preferably 0 for ease of manufacturing. g and h are preferably 1 or 2, and more preferably 1, for improved solubility.

[0079] Ring B is one of the following: pyridine ring, pyrimidine ring, imidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, carboline ring, benzothiazole ring, or benzoxazole ring. These may have substituents. From the viewpoint of durability, ring B is preferably a pyridine ring, a pyrimidine ring, or an imidazole ring, and more preferably a pyridine ring.

[0080] The hydrogen atoms on ring B are preferably substituted with C1-C20 alkyl groups, C7-C40 (hetero)aralkyl groups, or C3-C20 (hetero)aryl groups, in terms of durability and improved solubility. It is preferable that the hydrogen atoms on ring B are not substituted, as this facilitates manufacturing. It is preferable that the hydrogen atoms on ring B are substituted with a phenyl group or naphthyl group, which may have substituents, because this facilitates exciton generation when used in an organic electroluminescent device, thereby increasing the luminescence efficiency.

[0081] Ring B is preferable in that the substituents on ring B bond to each other to form a condensed ring, thereby forming a quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, or carboline ring, as this facilitates exciton generation on the assist dopant and thus increases luminescence efficiency. In particular, ring B is preferred to be a quinoline ring, isoquinoline ring, or quinazoline ring in terms of durability and exhibiting red luminescence.

[0082] In formula (2C), R 11 ~R 13 each independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms which may be substituted with a fluorine atom, a phenyl group which may be substituted with an alkyl group having 1 to 20 carbon atoms, or a halogen atom. More preferably, R 11 and R 13 are a methyl group or a t-butyl group, and R 12 is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a phenyl group.

[0083] The compound represented by formula (2) is preferably a compound represented by the following formula (2-2) in which adjacent R 8 are bonded to each other to form a fluorene ring.

[0084] [Chemical formula]

[0085] [In formula (2-2), R 7 , d, m, n, ring A, Z 1 , L 1 , l have the same meanings as R 7 , d, m, n, ring A, Z 1 , L 1 , l in formula (2). R 15 ~R 17 are substituents.]

[0086] Examples of R 15 include the aforementioned substituents that R 8 may have. More preferably, R 15 is an alkyl group having 1 to 20 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms which may be substituted with one or two alkyl groups having 1 to 20 carbon atoms. Here, the aromatic hydrocarbon group having 6 to 30 carbon atoms is a monocyclic, bicyclic condensed ring, or tricyclic condensed ring, or a group in which a plurality of monocyclic, bicyclic condensed rings, or tricyclic condensed rings are linked. R 15 is more preferably an alkyl group having 1 to 20 carbon atoms, and particularly preferably an alkyl group having 1 to 8 carbon atoms.

[0087] R 16 , R 17 is the aforementioned R 8 A part of or the R 8 The substituents that may be present are preferably, independently, a C1-C12 alkyl group, a C6-C20 aromatic hydrocarbon group which may be substituted with one or two C1-C12 alkyl groups, a C1-C12 alkoxy group, or a C6-C20 aromatic hydrocarbon group which may be substituted with one or two C1-C12 alkoxy groups. Here, a C6-C20 aromatic hydrocarbon group is a monocyclic, dicyclic fused, or tricyclic fused ring, or a group in which multiple monocyclic, dicyclic fused, or tricyclic fused rings are linked together. 16 , R 17 More preferably, each is independently a C1-C8 alkyl group, or a C6 or C12 aromatic hydrocarbon group which may be substituted with one or two C1-C8 alkyl groups, and particularly preferably a C6 aromatic hydrocarbon group which may be substituted with a C1-C8 alkyl group, or one or two C1-C8 alkyl groups. Here, the C6 aromatic hydrocarbon structure is a benzene structure, and the C12 aromatic hydrocarbon structure is a biphenyl structure.

[0088] The following are preferred specific examples of compounds represented by formula (2), which are iridium complexes that may be included as functional materials in the organic electroluminescent element composition of the present invention.

[0089] [ka]

[0090] [ka]

[0091] [ka]

[0092] The organic electroluminescent light-emitting composition of the present invention may contain only one of these iridium complexes, or it may contain two or more of them.

[0093] [Charge transport material] The charge-transporting material that may be included as a functional material in the organic electroluminescent element composition of the present invention is a material having positive charge (hole) or negative charge (electron) transport properties. The charge-transporting material is not particularly limited as long as it does not impair the effects of the present invention, and known materials can be used.

[0094] The charge-transporting material can be a compound that has been conventionally used in the light-emitting layer of an organic electroluminescent device. In particular, compounds used as host materials for the light-emitting layer are preferred as the charge-transporting material.

[0095] Examples of charge-transporting materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by fluorene groups, hydrazone compounds, silazane compounds, silanamine compounds, phosphatamine compounds, quinacridone compounds, and other compounds exemplified as hole-transporting compounds for hole injection layer 3 described later. Other examples of electron-transporting compounds include anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, and silole compounds.

[0096] As the charge transport material, for example, aromatic diamines containing two or more tertiary amines represented by 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), aromatic amine compounds having a starburst structure such as 4,4',4''-tris(1-naphthylphenylamino)triphenylamine (J. Lumin., Vol. 72-74, p. 985, 1997), aromatic amine compounds composed of tetramers of triphenylamine (Chem. Commun., p. 2175, 1996), fluorene compounds such as 2,2',7,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997), and carbazole compounds such as 4,4'-N,N'-dicarbazolebiphenyl, and the compounds exemplified as the hole transport compounds of the hole transport layer 4 described below can also be preferably used. As other charge transport materials, oxadiazole compounds such as 2-(4-biphenylyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD) and 2,5-bis(1-naphthyl)-1,3,4-oxadiazole (BND), silole compounds such as 2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), and phenanthroline compounds such as bathophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin) can also be mentioned.

[0097] The charge transport material that may be contained in the composition for an organic electroluminescent device of the present invention is preferably a polymer compound having a repeating unit containing a structure represented by the following formula (3) (hereinafter, may be referred to as "repeating unit (3)") from the viewpoint of film-forming properties.

[0098] [Chemical formula]

[0099] [In formula (3), R 19 , R20 Each of these groups is independently one or a combination of the following: an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 30 carbon atoms. These groups may also have substituents.

[0100] In formula (3), R 19 , R 20 From the viewpoint of solubility, a C1-C20 alkyl group and a C7-C40 (hetero)aralkyl group are preferred, independently of each other. 19 , R 20 In terms of heat resistance, (hetero)aryl groups having 3 to 30 carbon atoms are preferred for each component.

[0101] The polymer compound having repeating units (3) that may be included in the organic electroluminescent element composition of the present invention preferably includes, in addition to repeating units (3), repeating units (hereinafter sometimes referred to as "repeating units (3-1)") that include a structure represented by the following formula (3-1), in order to enhance charge transportability. In this case, repeating units (3) may be those included in the following repeating units (3-1).

[0102] [ka]

[0103] [In formula (3-1), Ar 21 ~Ar 23 Each of these independently represents a divalent (hetero)arylene group having 3 to 30 carbon atoms, which may have substituents. Ar 24 Ar 25 Each of these independently represents a (hetero)aryl group having 3 to 30 carbon atoms, which may have substituents. r represents an integer between 0 and 2.

[0104] Ar 21 ~Ar 23 In terms of durability, each group is independently preferably a phenylene group, a biphenylene group, a terphenylene group, a fluoroorangeyl group, or a divalent group with 30 or fewer carbon atoms obtained by arbitrarily selecting and linking these groups, with p-phenylene groups and biphenylene groups being particularly preferred. These groups may also have substituents.

[0105] If equation (3-1) includes the structure represented by equation (3), then Ar 21 Ar 22 , or if r is 1 or greater, at least one Ar 23 At least one selected from , is a fluorenyl group represented by formula (3), which may have substituents at the 9,9' position.

[0106] Ar 24 Ar 25 In terms of durability, phenyl, biphenyl, terphenyl, and fluorenyl groups are preferred, with phenyl and fluorenyl groups being particularly preferred. These groups may also have substituents.

[0107] The polymer compound having repeating units (3) that may be included in the organic electroluminescent light-emitting device composition of the present invention may contain only one type of repeating unit (3), or it may contain two or more types. Furthermore, it may contain only one type of repeating unit (3-1), or it may contain two or more types.

[0108] The weight-average molecular weight (Mw) of the polymer compound having repeating units (3) that may be included in the organic electroluminescent element composition of the present invention is usually 2,000,000 or less, preferably 500,000 or less, more preferably 100,000 or less, and even more preferably 50,000 or less, and 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 upper limit, it exhibits excellent solubility in solvents and film-forming properties. If the weight-average molecular weight is above the lower limit, the polymer compound has a high glass transition temperature, melting point, and vaporization temperature, and exhibits excellent heat resistance.

[0109] The number-average molecular weight (Mn) of the polymer compound having repeating units (3) that may be included in the organic electroluminescent element composition of the present invention is usually 1,000,000 or less, preferably 250,000 or less, more preferably 50,000 or less, and even more preferably 25,000 or less, and usually 2,000 or more, preferably 4,000 or more, more preferably 8,000 or more, and even more preferably 15,000 or more.

[0110] The dispersion degree (Mw / Mn) of the polymer compound having repeating units (3) that may be included in the organic electroluminescent element composition of the present invention is preferably 3.5 or less, more preferably 2.5 or less, and particularly preferably 2.0 or less. Since a smaller dispersion degree is better, the lower limit is ideally 1. When the dispersion degree of the polymer compound is below the above upper limit, purification is easy, and solubility in the solvent and charge transport ability are good.

[0111] Typically, the weight-average molecular weight of a polymer compound is determined by SEC (size exclusion chromatography) measurement. In SEC measurement, higher molecular weight components have shorter elution times, while lower molecular weight components have longer elution times. The weight-average molecular weight is calculated by converting the sample's elution time to molecular weight using a calibration curve derived from the elution time of polystyrene (standard sample) with a known molecular weight. The number-average molecular weight can be determined in a similar manner.

[0112] The method for producing the polymer compound having repeating units (3), which may be included in the organic electroluminescent element composition of the present invention, is not particularly limited and is arbitrary as long as a polymer compound having repeating units (3) can be obtained. For example, it can be produced by polymerization methods such as the Suzuki reaction, the Grignard reaction, the Yamamoto reaction, the Ullmann reaction, the Buchwald-Hartwig reaction, etc.

[0113] [Phenol derivatives] The organic electroluminescent element composition of the present invention contains a phenol derivative which is a compound represented by the following formula (1).

[0114] [ka]

[0115] [In the above formula, a is an integer from 0 to 4. R 1 , R 2 Each independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When a is an integer from 2 to 4, multiple R 2 They may be the same or they may be different.

[0116] In the compound represented by formula (1), the presence of an electron-donating alkyl group or alkoxy group at the ortho-position of the hydroxyl group shifts the redox potential of the compound represented by formula (1) to the negative side, resulting in a shallower HOMO and increased susceptibility to oxidation. Consequently, the oxidation of any functional materials contained within is suppressed.

[0117] For a, 1 or 2 is preferable in that it results in a moderate oxidation-reduction potential.

[0118] R 1 , R 2However, examples of alkyl groups 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, isopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, and dodecyl group.

[0119] R 1 , R 2 However, examples of alkoxy groups having 1 to 12 carbon atoms include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, s-butoxy, t-butoxy, pentyloxy, isopentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, 2-ethylhexyloxy, nonyloxy, decyloxy, undecyloxy, and dodecyloxy groups.

[0120] R 1 , R 2 Secondary or tertiary alkyl groups are preferred, with tertiary alkyl groups being more preferred, because they have significant steric hindrance, suppressing coupling reactions between phenoxy radicals generated after oxidation, and allowing them to function again as antioxidants. The ortho-position of the hydroxyl group is preferably a t-butyl group, which is the smallest tertiary alkyl group, because it is inexpensive and has a small molecular weight, making it less likely to remain in the luminescent layer after film formation.

[0121] It is preferable that both ortho-positions of the hydroxyl group are alkyl or alkoxy groups, as this results in a suitable redox potential and high stability of the phenoxy radicals generated after oxidation. In other words, the organic electroluminescent element composition of the present invention preferably contains the compound represented by formula (1-1) below as the compound represented by formula (1).

[0122] [ka]

[0123] [In the above formula, b is an integer from 0 to 3. R 3 , R 4 , R 5 Each of these independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When b is an integer between 2 and 3, multiple R groups are represented. 5 They may be the same or they may be different.

[0124] b is preferably 0 or 1, as this results in a suitable oxidation-reduction potential.

[0125] The ortho-position of the hydroxyl group is preferably a secondary or tertiary alkyl group, with a tertiary alkyl group being more preferable, because the steric hindrance is significant, suppressing the coupling reaction between phenoxy radicals generated after oxidation, and allowing the group to function again as an antioxidant. The ortho-position of the hydroxyl group is preferably a t-butyl group, which is the smallest tertiary alkyl group, because it is inexpensive and has a small molecular weight, making it less likely to remain in the luminescent layer after film formation. In other words, the organic electroluminescent element composition of the present invention preferably contains a compound represented by formula (1-2) below as the compound represented by formula (1).

[0126] [ka]

[0127] [In the above formula, b, R 5 b, R in the above formula (1-1) are 5 This is synonymous with [the above].

[0128] As mentioned above, b is preferably 0 or 1 in that it provides an appropriate oxidation-reduction potential.

[0129] [solvent] The organic electroluminescent light-emitting element composition of the present invention comprises an aliphatic ester solvent and / or an aromatic diester solvent having two or more carbonyl groups.

[0130] The solvent contained in the organic electroluminescent element composition of the present invention is a volatile liquid component used to form a layer containing a functional material by wet film deposition. Preferably, the solvent is one that readily dissolves the functional material, such as a light-emitting material or a charge-transporting material.

[0131] <Aliphatic ester solvents having two or more carbonyl groups> An aliphatic ester solvent having two or more carbonyl groups has one or more additional carbonyl groups in addition to the carbonyl groups contained in the aliphatic carboxylic acid ester portion. The carbonyl groups further present in the solvent may be aliphatic carboxylic acid ester groups or not, but it is preferable that they be aliphatic carboxylic acid ester groups in that they can further suppress changes in the liquid properties of the ink due to structural changes caused by oxidation of the phenol derivative.

[0132] 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, being a ketone group is preferable because it can further suppress changes in the liquid properties of the ink due to structural changes caused by oxidation of the phenol derivative.

[0133] As an aliphatic ester solvent having two or more carbonyl groups, it is preferable that the compound has two ester groups, as this can further suppress changes in the liquid properties of the ink due to structural changes caused by the oxidation of phenol derivatives. Furthermore, it is preferable that the compound has one ester group and one ketone group, as this allows for even better dissolution of functional materials such as luminescent materials and charge transport materials.

[0134] The organic electroluminescent element composition of the present invention preferably contains a compound represented by the following formula (9-1) as an aliphatic dicarboxylic acid ester.

[0135] [ka]

[0136] [In the above formula, R 24 R indicates an alkylene group. 25 , R 26 Each of these independently represents an alkyl group. 24 and R 25 These elements may also be joined together to form a ring.

[0137] R 24 In terms of having appropriate volatility as a solvent, alkylene groups having 1 to 20 carbon atoms are preferred, and alkylene groups having 2 to 12 carbon atoms are more preferred. 25 , R 26 In terms of having appropriate volatility as a solvent, alkyl groups having 1 to 20 carbon atoms are preferred, and alkyl groups having 1 to 6 carbon atoms are more preferred.

[0138] The alkylene group R 24 It may be linear, branched, or cyclic. 24 It is preferable that the group is a linear alkylene group, as this increases the viscosity of the ink and reduces flow after application. 24 It is preferable that the branched alkylene group is used because it lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method. 24 It is preferable that the group be a cyclic alkylene group, as this reduces the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method.

[0139] R is an alkyl group 25 , R 26 They may be the same or different from each other. Also, R 25 , R 26 It may be linear, branched, or cyclic. 25 , R 26 It is preferable that the alkyl group is a linear chain, as this increases the viscosity of the ink and reduces flow after application. 25 , R 26 It is preferable that the R is a branched alkyl group, as this lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method. 25 , R 26It is preferable that the alkyl group be a cyclic alkyl group, as this lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method.

[0140] The compound represented by formula (9-1) is preferably an aliphatic dicarboxylic acid ester containing a cyclic structure, as it readily dissolves solutes and facilitates the creation of high-concentration inks.

[0141] The organic electroluminescent element composition 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.

[0142] [ka]

[0143] [In the above formula, R 27 R indicates an alkylene group. 28 , R 29 Each of these independently represents an alkyl group. 27 and R 28 , or R 27 and R 29 These elements may also be joined together to form a ring.

[0144] R 27 In terms of having appropriate volatility as a solvent, alkylene groups having 1 to 20 carbon atoms are preferred, and alkylene groups having 2 to 12 carbon atoms are more preferred. 28 , R 29 In terms of having appropriate volatility as a solvent, alkyl groups having 1 to 20 carbon atoms are preferred, and alkyl groups having 1 to 6 carbon atoms are more preferred.

[0145] The alkylene group R 27 It may be linear, branched, or cyclic. 27 It is preferable that the group is a linear alkylene group, as this increases the viscosity of the ink and reduces flow after application. 27It is preferable that the branched alkylene group is used because it lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method. 27 It is preferable that the group be a cyclic alkylene group, as this reduces the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method.

[0146] R is an alkyl group 28 , R 29 They may be the same or different from each other. Also, R 28 , R 29 It may be linear, branched, or cyclic. 28 , R 29 It is preferable that the alkyl group is a linear chain, as this increases the viscosity of the ink and reduces flow after application. 28 , R 29 It is preferable that the R is a branched alkyl group, as this lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method. 28 , R 29 It is preferable that the alkyl group be a cyclic alkyl group, as this lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method.

[0147] The compound represented by formula (9-2) is preferably an aliphatic carboxylic acid ester having a ketone group and containing a cyclic structure, as this facilitates the dissolution of solutes and the creation of high-concentration inks.

[0148] These aliphatic ester solvents having two or more carbonyl groups may be used individually, or two or more may be used in any combination and ratio.

[0149] <Aromatic diester solvents> Aromatic diester solvents are preferred because they can effectively suppress changes in the liquid properties of the ink due to structural changes caused by the oxidation of phenol derivatives. Aromatic diester solvents are also preferred because they can easily dissolve solutes.

[0150] The organic electroluminescent element composition of the present invention preferably contains a compound represented by the following formula (9-3) as an aromatic diel solvent.

[0151] [ka]

[0152] [In the above formula, Ar 31 This indicates an arylene group, R 30a , R 30b Each of these independently represents an alkyl group. 30a and Ar 31 These elements may also be joined together to form a ring.

[0153] Ar 31 In terms of having a suitable volatility as a solvent, phenylene groups and naphthalenediyl groups are preferred, and phenylene groups are more preferred. 31 In terms of lower ink viscosity and stable ejection performance when applied by inkjet method, o-phenylene groups and m-phenylene groups are preferred, with m-phenylene groups being more preferred.

[0154] R 30a , R 30b Alkyl alkyl groups having 1 to 20 carbon atoms are preferred, and alkyl groups having 1 to 6 carbon atoms are more preferred, as they have appropriate volatility as a solvent.

[0155] R is an alkyl group 30a , R 30b They may be the same or different from each other. Also, R 30a , R 30b It may be linear, branched, or cyclic. 30a , R 30b It is preferable that the alkyl group is a linear chain, as this increases the viscosity of the ink and reduces flow after application. 30a , R 30b It is preferable that the R is a branched alkyl group, as this lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method. 30a , R 30bIt is preferable that the R is a cyclic alkyl group because it lowers the viscosity of the ink and stabilizes the ejection performance when applied by the inkjet method. 30a , R 30b It is preferable that the alkyl group contains a cyclic structure, as this facilitates the dissolution of solutes and makes it easier to create high-concentration inks.

[0156] These aromatic diester solvents may be used individually, or two or more may be used in any combination and ratio.

[0157] Furthermore, the organic electroluminescent element composition of the present invention may contain one or more aliphatic ester solvents having two or more carbonyl groups as described above, and one or more aromatic diester solvents as described above, in any combination and ratio.

[0158] <Other Solvents> The organic electroluminescent element composition of the present invention may also contain other solvents other than aliphatic ester solvents and aromatic diester solvents having two or more carbonyl groups.

[0159] Other preferred solvents include alkylated biphenyls, aromatic ethers, and aromatic monoesters, which have appropriate boiling points and readily dissolve solutes.

[0160] Other solvents that may be included in the organic electroluminescent element composition of the present invention include monoalkylated biphenyls having one alkyl group, dialkylated biphenyls having two alkyl groups, or trialkylated biphenyls, tetraalkylated biphenyls, heptaalkylated biphenyls, hexaalkylated biphenyls, etc., having three or more alkyl groups.

[0161] Due to their low boiling point and high volatility, monoalkylated biphenyls or dialkylated biphenyls are preferred, with monoalkylated biphenyls being more preferred. Dialkylated biphenyls and trialkylated biphenyls are preferred because they have a high melting point and little risk of solidification when the composition is placed at a low temperature, and trialkylated biphenyls are more preferred. Dialkylated biphenyls are preferred because they have appropriate boiling and melting points.

[0162] Monoalkylated biphenyls are represented by the following formula (4).

[0163] [In the above formula, R 31 represents an alkyl group which may have a substituent. ]

[0165] As the alkyl group R 31 substituting biphenyl, an alkyl group having 1 to 12 carbon atoms is preferred. Examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. Among these, a methyl group, an ethyl group, a propyl group, and an isopropyl group are particularly preferred in that they have a low boiling point and can ensure high volatility. R 31 may have a phenyl group as a substituent. In this case, as the alkyl group having a substituent, a benzyl group and a 2-phenylethyl group are preferred.

[0166] Examples of monoalkylated biphenyls include 2-methylbiphenyl, 3-methylbiphenyl, 4-methylbiphenyl, 2-ethylbiphenyl, 3-ethylbiphenyl, 4-ethylbiphenyl, 2-propylbiphenyl, 3-propylbiphenyl, 4-propylbiphenyl, 2-isopropylbiphenyl, 3-isopropylbiphenyl, 4-isopropylbiphenyl, 2-butylbiphenyl, 3-butylbiphenyl, 4-butylbiphenyl, 4-cyclohexylbiphenyl, and the like.​​​​​​​

[0167] Dialkylated biphenyls are represented by the following formulas (4-1) or (4-2).

[0168] [ka]

[0169] [In the above formula, R 32 ~R 35 Each of these independently represents an alkyl group that may have substituents.

[0170] R 32 ~R 35 A preferred example is R 31 This is the same as a preferred example.

[0171] Examples of dialkylated biphenyls include 2,3-dimethylbiphenyl, 3,4-dimethylbiphenyl, 3,3'-dimethylbiphenyl, 2,4-diethylbiphenyl, 2,3'-diethylbiphenyl, 3,4'-diethylbiphenyl, 2,2'-dipropylbiphenyl, 2,4-dipropylbiphenyl, 2,4'-dipropylbiphenyl, 3,4-diisopropylbiphenyl, 3,4'-diisopropylbiphenyl, 3,5-diisopropylbiphenyl, 3,3'-butylbiphenyl, 3,4'-butylbiphenyl, and 4,4'-butylbiphenyl.

[0172] Trialkylated biphenyls are represented by the following formulas (4-3) or (4-4).

[0173] [ka]

[0174] [In the above formula, R 36 ~R 41 Each of these independently represents an alkyl group that may have substituents.

[0175] R 32 ~R35 A preferred example of R 31 is the same as the preferred example of R

[0176] Examples of the trialkylated biphenyl include, for example, 2,3,4-trimethylbiphenyl, 2,3,3'-trimethylbiphenyl, 3,3',4-trimethylbiphenyl, 2,4,4'-triethylbiphenyl, 3,4,5-triethylbiphenyl, 3,4',5-triethylbiphenyl, 2,2',4-tripropylbiphenyl, 2,4,5-dipropylbiphenyl, 2,3,4'-tripropylbiphenyl, 2,3',4-triisopropylbiphenyl, 2,3',5-triisopropylbiphenyl, 3,4,4'-triisopropylbiphenyl, and the like.

[0177] These alkylated biphenyls may be used alone, or two or more of them may be used in any combination and ratio.

[0178] As other solvents, the aromatic ether that may be included in the composition for an organic electroluminescent device of the present invention is preferably an alkoxybenzene that may have an alkyl group represented by the following formula (5) in terms of having high solubility.

[0179] [In the above formula, i represents an integer of 0 to 5. R

[0180] [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.]

[0181] In terms of having a low boiling point and high volatility, i is preferably an integer of 0 to 3, and more preferably 0 or 1.

[0182] R 51 and R 52Preferably, the alkyl group has 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, pentyl group, isopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, and dodecyl group. 51 , R 52 The alkyl group may have a phenyl group as a substituent, in which case benzyl group and 2-phenylethyl group are preferred as the substituted alkyl group.

[0183] As for other solvents, phenoxybenzene is preferred as an aromatic ether that may be included in the organic electroluminescent element composition of the present invention, because it has a high boiling point and is suitable for large-area coating, and may have an alkyl group represented by the following formula (5-1).

[0184] [ka]

[0185] [In the above formula, j and k represent integers from 0 to 5. R 53 , R 54 Each of these independently represents an alkyl group that may have substituents.

[0186] j and k are integers between 0 and 2, and more preferably 0 or 1, as they have low boiling points and high volatility.

[0187] R 53 , R 54 Preferably, the alkyl group has 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, pentyl group, isopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, and dodecyl group. 53 , R 54The alkyl group may have a phenyl group as a substituent, in which case benzyl group and 2-phenylethyl group are preferred as the substituted alkyl group.

[0188] As other solvents, a preferred aromatic monoester that may be included in the organic electroluminescent element composition of the present invention is a benzoic acid monoester which may have an alkyl group represented by the following formula (6).

[0189] [ka]

[0190] [In the above formula, q represents an integer from 0 to 5. R 55 , R 56 Each of these independently represents an alkyl group that may have substituents.

[0191] q is preferably an integer between 0 and 2, and more preferably 0 or 1, given its low boiling point and high volatility.

[0192] R 55 , R 56 Preferably, the alkyl group has 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, pentyl group, isopentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, and dodecyl group. 55 , R 56 The alkyl group may have a phenyl group as a substituent, in which case benzyl group and 2-phenylethyl group are preferred as the substituted alkyl group.

[0193] These aromatic ethers and / or aromatic monoesters may be used individually or in any combination and ratio of two or more types. That is, only one type of aromatic ether may be used, only one type of aromatic monoester may be used, or one or more types of aromatic ethers and one or more types of aromatic monoesters may be used in any combination and ratio.

[0194] The organic electroluminescent element composition of the present invention may also contain, as a solvent other than the aliphatic ester solvent and aromatic diester solvent having two or more carbonyl groups, other solvents other than the alkylated biphenyl, aromatic ether, and aromatic monoester mentioned above.

[0195] Other preferred solvents besides alkylated biphenyls, aromatic ethers, and aromatic monoesters include, for example, 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 fencone; 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).

[0196] These other solvents may be used individually or in any combination and ratio of two or more types.

[0197] <T point of the solvent> The boiling point of the solvent is typically 80°C or higher, preferably 100°C or higher, more preferably 150°C or higher, and particularly preferably 200°C or higher, and typically 350°C or lower, preferably 320°C or lower, and more preferably 300°C or lower. If the boiling point falls below this range, the film formation stability may decrease during wet film formation due to solvent evaporation from the composition.

[0198] [Content of each ingredient] When the organic electroluminescent element composition of the present invention contains a light-emitting material as a functional material, the content (concentration) of the light-emitting material in the organic electroluminescent element composition of the present invention is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, preferably 8.0% by mass or less, more preferably 4.0% by mass or less, and even more preferably 2.0% by mass or less. If the concentration of the luminescent material is above the lower limit mentioned above, a layer containing sufficient luminescent material can be formed. If the concentration of the luminescent material is below the upper limit mentioned above, it is easy to maintain a uniform state without precipitating the dissolved luminescent material.

[0199] When the organic electroluminescent element composition of the present invention contains a charge transporting material as a functional material, the content (concentration) of the charge transporting material in the organic electroluminescent element composition of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, preferably 16% by mass or less, more preferably 8.0% by mass or less, and even more preferably 4.0% by mass or less. If the concentration of the charge-transporting material is above the lower limit mentioned above, a layer containing sufficient charge-transporting material can be formed. If the concentration of the charge-transporting material is below the upper limit mentioned above, it is easy to maintain a uniform state without precipitating the dissolved charge-transporting material.

[0200] When the organic electroluminescent element composition of the present invention includes a light-emitting material and a charge-transporting material as functional materials, the total content (concentration) of these materials in the organic electroluminescent element composition of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.4% by mass or more, preferably 16% by mass or less, more preferably 8.0% by mass or less, and even more preferably 4.0% by mass or less. If the total concentration of the functional materials is above the lower limit, a layer containing sufficient functional materials can be formed. If the total concentration of the functional materials is below the upper limit, it is easy to maintain a uniform state without precipitating the dissolved functional materials.

[0201] The mass ratio of the luminescent material to the charge transport material is preferably in the range of luminescent material:charge transport material = 1:0.8 to 16, particularly in the range of 1:1.2 to 8.0, and especially in the range of 1:1.6 to 4.0. If the mass ratio of the luminescent material to the charge transport material is within the above range, it is possible to create an organic electroluminescent element with a low driving voltage and high luminous efficiency.

[0202] The content (concentration) of the phenol derivative represented by formula (1) in the organic electroluminescent element composition of the present invention is preferably 5 ppm by mass or more, more preferably 10 ppm by mass or more, even more preferably 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 above the lower limit mentioned above, the effect of suppressing the degradation of the functional material by the phenol derivative can be sufficiently obtained. If the concentration of the phenol derivative is below the upper limit mentioned above, it is easy to remove the phenol derivative and its oxides together with the solvent when forming the light-emitting layer.

[0203] The content of the aliphatic ester solvent and / or aromatic diester solvent having two or more carbonyl groups in the organic electroluminescent light-emitting element composition of the present invention is preferably 2.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 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 above the lower limit mentioned above, the change in liquid properties when the ink is stored for a long period of time can be reduced.

[0204] The organic electroluminescent element composition of the present invention may further contain the aforementioned other solvents in addition to the aliphatic ester solvent and / or aromatic diester solvent having two or more carbonyl groups. However, if the organic electroluminescent element composition of the present invention contains other solvents, the content of the other solvents in the total solvent is preferably 95% by mass or less, and particularly 85% by mass or less, in order to more effectively obtain the effects of the present invention by using the aliphatic ester solvent and / or aromatic diester solvent having two or more carbonyl groups.

[0205] The total solvent content in the organic electroluminescent element composition of the present invention is preferably high in order to facilitate film formation due to its low viscosity, and preferably low in order to facilitate the formation of thick films. The total solvent content in the organic electroluminescent element composition 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 also preferably 99.99% by mass or less, more preferably 99.9% by mass or less, and particularly preferably 99% by mass or less.

[0206] [Application] The organic electroluminescent light-emitting composition of the present invention is particularly suitable for use as a composition for forming a light-emitting layer, which includes a light-emitting material and a charge-transporting material as functional materials.

[0207] [Organic electroluminescent device] The organic electroluminescent element of the present invention has a light-emitting layer formed using the organic electroluminescent element composition of the present invention.

[0208] The organic electroluminescent element 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, wherein at least one of the organic layers is a light-emitting layer formed by a wet film deposition method using the organic electroluminescent element composition of the present invention.

[0209] In the present invention, the wet film formation method refers to a method in which a film is formed in a wet manner, such as spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, inkjet, nozzle printing, screen printing, gravure printing, or flexographic printing, and the film formed by these methods is dried to form the final film.

[0210] Figure 1 is a schematic cross-sectional view showing a suitable structural example for the organic electroluminescent element 10 of the present invention. In Figure 1, reference numeral 1 denotes the substrate, reference numeral 2 denotes the anode, reference numeral 3 denotes the hole injection layer, reference numeral 4 denotes the hole transport layer, reference numeral 5 denotes the light-emitting layer, reference numeral 6 denotes the hole blocking layer, reference numeral 7 denotes the electron transport layer, reference numeral 8 denotes the electron injection layer, and reference numeral 9 denotes the cathode.

[0211] The materials used for these structures can be any known materials, and there are no particular restrictions. Representative materials and manufacturing methods for each layer are described below as examples. Where publications or papers are cited, the relevant content may be applied and adapted as appropriate within the bounds of common sense of those skilled in the art.

[0212] [Circuit board 1] The substrate 1 serves as a support for the organic electroluminescent element, and is typically made of quartz, glass, metal, metal foil, plastic film, or sheet. Of these, glass plates and transparent synthetic resin plates such as polyester, polymethacrylate, polycarbonate, or polysulfone are preferred. The substrate 1 is preferably made of a material with high gas barrier properties to prevent degradation of the organic electroluminescent element by the outside air. Therefore, especially when using a material with low gas barrier properties, such as a synthetic resin substrate, it is preferable to provide a dense silicon oxide film or the like on at least one side of the substrate 1 to improve its gas barrier properties.

[0213] [Anode 2] Anode 2 is responsible for injecting holes into the light-emitting layer.

[0214] Anode 2 is typically composed of metals such as aluminum, gold, silver, nickel, palladium, and platinum; metal oxides such as indium and / or tin oxides; metal halides such as copper iodide; or conductive polymers such as carbon black, poly(3-methylthiophene), polypyrrole, and polyaniline.

[0215] The formation of anode 2 is usually carried out by dry methods such as sputtering or vacuum deposition. When forming anode 2 using metal nanoparticles such as silver, nanoparticles such as copper iodide, carbon black, conductive metal oxide nanoparticles, or conductive polymer fine powder, it can also be formed by dispersing them in a suitable binder resin solution and coating it onto a substrate. In the case of conductive polymers, a thin film can be formed directly on the substrate by electrolytic polymerization, or anode 2 can be formed by coating the substrate with conductive polymer (Appl. Phys. Lett., Vol. 60, p. 2711, 1992).

[0216] Anode 2 is usually a single-layer structure, but it may be a multilayer structure as appropriate. If anode 2 is a multilayer structure, different conductive materials may be laminated on the first layer of anode.

[0217] The thickness of anode 2 should be determined according to the required transparency and material. When particularly high transparency is required, a thickness that allows for a visible light transmittance of 60% or more is preferable, and a thickness that allows for a visible light transmittance of 80% or more is even more preferable. The thickness of anode 2 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less. If transparency is not required, the thickness of anode 2 can be set arbitrarily according to the required strength, etc., and in this case, anode 2 may be the same thickness as substrate 1.

[0218] When forming a film on the surface of anode 2, it is preferable to remove impurities from the anode and adjust its ionization potential to improve hole injection properties by treating it with ultraviolet light + ozone, oxygen plasma, argon plasma, etc., before film formation.

[0219] [Hole injection layer 3] The layer responsible for transporting holes from the anode 2 to the light-emitting layer 5 is usually called a hole injection transport layer or hole transport layer. When there are two or more layers responsible for transporting holes from the anode 2 to the light-emitting layer 5, the layer closer to the anode 2 is sometimes called the hole injection layer 3. The hole injection layer 3 is preferable to use because it enhances the function of transporting holes from the anode 2 to the light-emitting layer 5. When the hole injection layer 3 is used, it is usually formed on the anode 2.

[0220] The thickness of the hole injection layer 3 is typically 1 nm or more, preferably 5 nm or more, typically 1000 nm or less, and preferably 500 nm or less.

[0221] The hole injection layer 3 can be formed by either vacuum deposition or wet deposition. Wet deposition is preferable because it offers superior film formation properties.

[0222] The hole injection layer 3 preferably contains a hole transport compound, and more preferably contains both a hole transport compound and an electron acceptor compound. Furthermore, the hole injection layer 3 preferably contains a cationic radical compound, and particularly preferably contains both a cationic radical compound and a hole transport compound.

[0223] (Hole transport compounds) Compositions for forming hole injection layers typically contain a hole-transporting compound that forms the hole injection layer 3. In the case of wet film formation, a solvent is also usually included. The hole-transporting compound preferably has high hole transportability and can efficiently transport the injected holes. For this reason, it is preferable that the hole-transporting compound has high hole mobility and does not easily generate trapping impurities during manufacturing or use. Furthermore, it is preferable that the hole-transporting compound has excellent stability, low ionization potential, and high transparency to visible light. In particular, when the hole injection layer 3 is in contact with the light-emitting layer 5, it is preferable that the hole-transporting compound does not quench the light emitted from the light-emitting layer 5 or forms an excyplex with the light-emitting layer 5, thereby not reducing the luminescence efficiency.

[0224] As hole-transporting compounds, compounds having an ionization potential of 4.5 eV to 6.0 eV are preferred from the viewpoint of a charge injection barrier from anode 2 to hole injection layer 3. Examples of hole-transporting compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by fluorene groups, hydrazone compounds, silazane compounds, quinacridone compounds, and the like.

[0225] Of the example compounds described above, aromatic amine compounds are preferred, and aromatic tertiary amine compounds are particularly preferred, from the viewpoint of amorphousness and visible light transmittance. Here, aromatic tertiary amine compounds are compounds having an aromatic tertiary amine structure, and also include compounds having a group derived from an aromatic tertiary amine.

[0226] The type of aromatic tertiary amine compound is not particularly limited, but it is preferable to use a polymer compound (polymerized compound with repeating units) with a weight-average molecular weight of 1,000 to 1,000,000, as it is easier to obtain uniform luminescence due to the surface smoothing effect.

[0227] Preferred examples of aromatic tertiary amine polymer compounds include polymer compounds having repeating units represented by the following formula (I).

[0228] [ka]

[0229] [In the above formula, Ar 1 and Ar 2 Each of these independently represents an optionally substituted aromatic group or an optionally substituted heteroaromatic group. 3 ~Ar 5 Each of these independently represents an aromatic group that may have substituents or a heteroaromatic group that may have substituents. Q represents a linking group selected from the following group of linking groups. Ar 1 ~Ar 5 Of these, two groups bonded to the same N atom may bond to each other to form a ring.

[0230] The linking group is shown below.

[0231] [ka]

[0232] [In each of the above formulas, Ar 6 ~Ar 16 Each of these independently represents an optionally substituted aromatic group or an optionally substituted heteroaromatic group. a ~R b Each of these independently represents a hydrogen atom or any substituent.

[0233] Ar 1 ~Ar 16 As for the aromatic and heteroaromatic groups, from the viewpoint of solubility, heat resistance, and hole injection transport of the polymer compound, groups derived from a benzene ring, naphthalene ring, phenanthrene ring, thiophene ring, or pyridine ring are preferred, and groups derived from a benzene ring or naphthalene ring are more preferred.

[0234] Specific examples of aromatic tertiary amine polymer compounds having repeating units represented by formula (I) include those described in International Publication No. 2005 / 089024.

[0235] (Electron-accepting compounds) The hole injection layer 3 preferably contains an electron-accepting compound, as the conductivity of the hole injection layer 3 can be improved by oxidation of the hole-transporting compound.

[0236] Preferred electron-accepting compounds are those that possess oxidizing power and the ability to accept one electron from the hole-transporting compound described above. Specifically, preferred electron-accepting compounds are those with an electron affinity of 4 eV or more, and even more preferred are those with an electron affinity of 5 eV or more.

[0237] Examples of such electron-accepting compounds include one or more compounds selected from the group consisting of triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Specifically, examples include onium salts with organic groups substituted, 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 Publication No. 11-251067) and ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris(pentafluorophenyl)borane (Japanese Patent Publication No. 2003-31365); fullerene derivatives and iodine.

[0238] (Cationic radical compounds) As the cationic radical compound, an ionic compound consisting of a cationic radical, which is a chemical species obtained by removing one electron from a hole-transporting compound, and a counter anion is preferred. However, if the cationic radical is derived from a hole-transporting polymer compound, the cationic radical will have a structure obtained by removing one electron from the repeating unit of the polymer compound.

[0239] The cation radical is preferably a species obtained by removing one electron from the aforementioned hole-transporting compound. This is preferable from the viewpoints of amorphousness, visible light transmittance, heat resistance, and solubility.

[0240] Cationic radical compounds can be produced by mixing the aforementioned hole-transporting compound and electron-accepting compound. That is, by mixing the aforementioned hole-transporting compound and electron-accepting compound, electron transfer occurs from the hole-transporting compound to the electron-accepting compound, and a cationic ion compound consisting of the cation radical and counter anion of the hole-transporting compound is produced.

[0241] Cationic radical compounds derived from polymer compounds such as PEDOT / PSS (Adv. Mater., 2000, Vol. 12, p. 481) and emeraldine hydrochloride (J. Phys. Chem., 1990, Vol. 94, p. 7716) can also be generated by oxidative polymerization (dehydrogenation polymerization). Oxidative polymerization, as used here, involves chemically or electrochemically oxidizing monomers in an acidic solution using peroxodisulfate or the like. In this oxidative polymerization (dehydrogenation polymerization), the monomers are oxidized to form polymers, and at the same time, cationic radicals are generated, which have one electron removed from the repeating units of the polymer, with an anion from the acidic solution acting as a counter-anion.

[0242] (Formation of hole injection layer 3 by wet deposition method) When forming the hole injection layer 3 by a wet deposition method, a composition for film formation (hole injection layer forming composition) is usually prepared by mixing the material that will become the hole injection layer 3 with a soluble solvent (solvent for the hole injection layer). This hole injection layer forming composition is then deposited on the layer corresponding to the layer below the hole injection layer 3 (usually the anode 2) by a wet deposition method and dried to form the layer. The dried film can be carried out in the same way as the drying method used in the formation of the light-emitting layer 5 by the wet deposition method described later.

[0243] The concentration of the hole transporting compound in the hole injection layer forming composition is arbitrary as long as it does not significantly impair the effects of the present invention. However, a lower concentration is preferable in terms of uniformity of film thickness, and a higher concentration is preferable in terms of preventing defects from occurring in the hole injection layer 3. Specifically, the concentration of the hole transporting compound in the hole injection layer forming composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

[0244] Examples of solvents include ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and amide-based solvents.

[0245] Examples of ether-based solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA), and aromatic ethers such as 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenethole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, and 2,4-dimethylanisole.

[0246] Examples of ester solvents 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.

[0247] Examples of amide solvents include N,N-dimethylformamide and N,N-dimethylacetamide. In addition to these, dimethyl sulfoxide and the like can also be used.

[0248] The hole injection layer 3 is typically formed by a wet deposition method, which involves preparing a hole injection layer formation composition, coating it onto the layer below the hole injection layer 3 (usually the anode 2), and then drying it. After deposition, the hole injection layer 3 is usually dried by heating or reduced-pressure drying.

[0249] (Formation of hole injection layer 3 by vacuum deposition method) When forming the hole injection layer 3 by vacuum deposition, typically one or more of the constituent materials of the hole injection layer 3 (such as the aforementioned hole transporting compound and electron-accepting compound) are placed in a crucible set up inside a vacuum chamber (if more than two materials are used, each is usually placed in a separate crucible), and the inside of the vacuum chamber is vacuumed with a vacuum pump for 10°C. -4 After evacuating to approximately Pa, the crucible is heated (if two or more materials are used, each crucible is usually heated) to evaporate the materials in the crucible while controlling the evaporation rate (if two or more materials are used, each is usually evaporated independently) to form a hole injection layer 3 on the anode 2 on the substrate placed facing the crucible. If two or more materials are used, a mixture of these materials can also be placed in the crucible, heated, and evaporated to form the hole injection layer 3.

[0250] The vacuum level during deposition is not limited as long as it does not significantly impair the effects of the present invention, but is typically 0.1 × 10⁻⁶. -6 Torr(0.13×10 -4 Pa) or above, 9.0×10 -6 Torr(12.0×10 -4The pressure is less than or equal to Pa. The deposition rate is not limited as long as it does not significantly impair the effects of the present invention, but is usually 0.1 Å / sec or more and 5.0 Å / sec or less. The film deposition temperature during deposition is not limited as long as it does not significantly impair the effects of the present invention, but is preferably 10°C or more and 50°C or less.

[0251] [Hole transport layer 4] The hole transport layer 4 is a layer responsible for transporting holes from the anode 2 to the light-emitting layer 5. Although the hole transport layer 4 is not an essential layer in the organic electroluminescent device of the present invention, it is preferable to provide this layer in order to enhance the function of transporting holes from the anode 2 to the light-emitting layer 5. When the hole transport layer 4 is provided, it 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.

[0252] The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[0253] The hole transport layer 4 can be formed by either vacuum deposition or a wet deposition method. However, wet deposition is preferable due to its superior film-forming properties.

[0254] The hole transport layer 4 typically contains a hole-transporting compound that forms the hole transport layer 4. Examples of hole-transporting compounds included in the hole transport layer 4 include, in particular, aromatic diamines containing two or more tertiary amines and in which two or more condensed aromatic rings are substituted with nitrogen atoms, such as 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (Japanese Patent Publication No. 5-234681), aromatic amine compounds having a starburst structure such as 4,4',4”-tris(1-naphthylphenylamino)triphenylamine (J. Lumin., Vol. 72-74, p. 985, 1997), and aromatic amine compounds consisting of a tetramer of triphenylamine (Chem. Commun., 2 Examples include spiro compounds such as 2,2',7,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997), and carbazole derivatives such as 4,4'-N,N'-dicarbazolebiphenyl. In addition, polyvinylcarbazole, polyvinyltriphenylamine (Japanese Patent Publication No. 7-53953), and polyarylene ethersulfone containing tetraphenylbenzidine (Polym. Adv. Tech., Vol. 7, p. 33, 1996) can also be preferably used.

[0255] (Formation of hole transport layer 4 by wet film deposition method) When forming the hole transport layer 4 by a wet deposition method, it is usually formed using a hole transport layer forming composition instead of a hole injection layer forming composition, in the same manner as when forming the hole injection layer 3 by a wet deposition method described above.

[0256] When forming the hole transport layer 4 by a wet film deposition method, the hole transport layer forming composition usually further contains a solvent. The solvent used in the hole transport layer forming composition can be the same solvent used in the hole injection layer forming composition described above. The concentration of the hole-transporting compound in the hole-transporting layer-forming composition can be within the same range as the concentration of the hole-transporting compound in the hole-injection layer-forming composition.

[0257] (Formation of hole transport layer 4 by vacuum deposition method) When forming the hole transport layer 4 by vacuum deposition, it can usually be formed using the same method as when forming the hole injection layer 3 by vacuum deposition, but instead of the constituent materials of the hole injection layer 3. The deposition conditions, such as the degree of vacuum, deposition rate, and temperature, can be the same as those used for vacuum deposition of the hole injection layer 3.

[0258] [Luminous layer 5] The light-emitting layer 5 is a layer that is excited and emits light when an electric field is applied between a pair of electrodes, by the recombination of holes injected from the anode 2 and electrons injected from the cathode 9. The light-emitting layer 5 is formed between the anode 2 and the cathode 9. If there is a hole injection layer 3 on the anode 2, the light-emitting layer 5 is formed between the hole injection layer 3 and the cathode 9. If there is a hole transport layer 4 on the anode 2, the light-emitting layer 5 is formed between the hole transport layer 4 and the cathode 9.

[0259] The film thickness of the light-emitting layer 5 is arbitrary as long as it does not significantly impair the effects of the present invention. However, a thicker film is preferable in that defects are less likely to occur in the film, while a thinner film is preferable in that it is easier 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 preferably 200 nm or less, and even more preferably 100 nm or less.

[0260] The light-emitting layer 5 contains at least a material having light-emitting properties (light-emitting material), and preferably a material having charge-transporting properties (charge-transporting material).

[0261] The following describes general light-emitting materials and methods for forming light-emitting layers. In the organic electroluminescent device of the present invention, it is preferable that the light-emitting layer be formed by a wet film deposition method using the organic electroluminescent device composition of the present invention described above. Furthermore, while iridium complexes, which are organometallic complexes with iridium as the central element, are preferred as the luminescent material, other luminescent materials may be used as appropriate. The following provides a detailed description of other luminescent materials besides iridium complex compounds.

[0262] (Luminescent material) The luminescent material is not particularly limited as long as it emits light at a desired emission wavelength and does not impair the effects of the present invention; known luminescent materials can be used. The luminescent material may be a fluorescent material or a phosphorescent material, but a material with good luminescence efficiency is preferred, and a phosphorescent material is preferred from the viewpoint of internal quantum efficiency.

[0263] Examples of fluorescent materials include the following: Examples of fluorescent materials that emit blue light (blue fluorescent materials) include naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis(2-phenylethenyl)benzene, and their derivatives. Examples of fluorescent materials that emit green light (green fluorescent materials) include quinacridone derivatives, coumarin derivatives, and aluminum complexes such as Al(C9H6NO)3. Examples of fluorescent materials that emit yellow light (yellow fluorescent materials) include rubrene and perimidone derivatives. Examples of fluorescent materials that emit red light (red fluorescent materials) include DCM(4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, and azabenzothioxanthene.

[0264] Examples of phosphorescent materials include organometallic complexes containing metals selected from groups 7 to 11 of the long-period periodic table (hereinafter, unless otherwise specified, "periodic table" refers to the long-period periodic table). Preferred metals selected from groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.

[0265] Preferred ligands for organometallic complexes include (hetero)arylpyridine ligands and (hetero)arylpyrazole ligands, which are ligands in which a (hetero)aryl group is linked to pyridine, pyrazole, phenanthroline, etc., with phenylpyridine ligands and phenylpyrazole ligands being particularly preferred. Here, (hetero)aryl refers to an aryl group or a heteroaryl group.

[0266] Preferred phosphorescent materials include, specifically, phenylpyridine complexes such as tris(2-phenylpyridine)iridium, tris(2-phenylpyridine)ruthenium, tris(2-phenylpyridine)palladium, bis(2-phenylpyridine)platinum, tris(2-phenylpyridine)osmium, and tris(2-phenylpyridine)rhenium, as well as porphyrin complexes such as octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethylpalladium porphyrin, and octaphenylpalladium porphyrin.

[0267] Examples of polymer-based luminescent materials include polyfluorene-based materials such as poly(9,9-dioctylfluorene-2,7-diyl), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl))diphenylamine)], and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(1,4-benzo-2{2,1'-3}-triazole)], and polyphenylene vinylene-based materials such as poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene].

[0268] (charge transport material) A charge-transporting material is a material that has the ability to transport positive charges (holes) or negative charges (electrons), and there are no particular limitations as long as the effects of the present invention are not impaired; known materials can be used. The charge transport material can be a compound that has been conventionally used in the light-emitting layer 5 of an organic electroluminescent device, and in particular, a compound used as the host material for the light-emitting layer 5 is preferred.

[0269] Examples of charge-transporting materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by fluorene groups, hydrazone compounds, silazane compounds, silanamine compounds, phosphatamine compounds, quinacridone compounds, and other compounds exemplified as hole-transporting compounds for hole injection layer 3. Other examples of electron-transporting compounds include anthracene compounds, pyrene compounds, carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds, and silole compounds.

[0270] Furthermore, as charge transport materials, for example, aromatic diamines containing two or more tertiary amines, represented by 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, in which two or more condensed aromatic rings are substituted with nitrogen atoms (Japanese Patent Publication No. 5-234681), aromatic amine compounds having a starburst structure such as 4,4',4”-tris(1-naphthylphenylamino)triphenylamine (J. Lumin., Vol. 72-74, p. 985, 1997), aromatic amine compounds consisting of a tetramer of triphenylamine (Chem. Commun., p. 2175, 1996), fluorene compounds such as 2,2',7,7'-tetrakis-(diphenylamino)-9,9'-spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997), 4, Compounds exemplified as hole transporting compounds for hole transport layer 4, such as carbazole compounds like 4'-N,N'-dicarbazole biphenyl, can also be preferably used. In addition, other examples include oxadiazole compounds such as 2-(4-biphenylyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD) and 2,5-bis(1-naphthyl)-1,3,4-oxadiazole (BND), silole compounds such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), and phenanthroline compounds such as basophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, basocuproine).

[0271] (Formation of the light-emitting layer 5 by wet film deposition method) The method for forming the light-emitting layer 5 may be either vacuum deposition or wet deposition, but wet deposition is preferred because it offers superior film-forming properties.

[0272] When forming the light-emitting layer 5 by a wet film deposition method, it is usually done in the same way as when forming the hole-injection layer 3 by the wet film deposition method described above, but instead of using the hole-injection layer forming composition, a light-emitting layer forming composition is used, which is prepared by mixing the material that will become the light-emitting layer 5 with a soluble solvent (light-emitting layer solvent). In the present invention, it is preferable to use the aforementioned organic electroluminescent element composition of the present invention as the light-emitting layer forming composition.

[0273] Examples of solvents include 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, aliphatic alcohol-based solvents, alicyclic alcohol-based solvents, aliphatic ketone-based solvents, and alicyclic ketone-based solvents. Preferred solvents are aliphatic ester solvents having two or more carbonyl groups, aromatic diester solvents, and other solvents as exemplified in the organic electroluminescent element composition of the present invention.

[0274] The amount of solvent used is arbitrary as long as it does not significantly impair the effects of the present invention. The total content in the light-emitting layer forming composition is preferably high in terms of ease of film formation due to its low viscosity, and preferably low in terms of ease of forming a thick film. As described above, the solvent content of the light-emitting layer forming composition is preferably 1% by mass or more, more preferably 10% by mass or more, particularly preferably 50% by mass or more, and also preferably 99.99% by mass or less, more preferably 99.9% by mass or less, and particularly preferably 99% by mass or less.

[0275] As a method for removing the solvent after wet film formation, heating or reduced pressure can be used. As a heating means, a clean oven or hot plate is preferred because it evenly heats the entire film. The heating temperature in the heating process is arbitrary as long as it does not significantly impair the effects of the present invention, but a higher temperature is preferable in terms of shortening the drying time, and a lower temperature is preferable in terms of minimizing damage to the material. The upper limit of the heating temperature is usually 250°C or less, preferably 200°C or less, and more preferably 150°C or less. 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 undesirable because it takes a long time to remove the solvent. The heating time in the heating process is appropriately determined by the boiling point and vapor pressure of the solvent in the light-emitting layer forming composition, the heat resistance of the material, and the heating conditions.

[0276] (Formation of the light-emitting layer 5 by vacuum deposition) When forming the light-emitting layer 5 by vacuum deposition, one or more of the constituent materials of the light-emitting layer 5 (the aforementioned light-emitting material, charge-transporting compound, etc.) are usually placed in a crucible set up inside a vacuum container (when using two or more materials, each is usually placed in a separate crucible), and the inside of the vacuum container is vacuumed with a vacuum pump for 10°C. -4 After evacuating to approximately Pa, the crucible is heated (if two or more materials are used, each crucible is usually heated) to evaporate the materials in the crucible while controlling the evaporation rate (if two or more materials are used, each is usually evaporated independently) to form a light-emitting layer 5 on the hole injection layer 3 or hole transport layer 4 placed facing the crucible. If two or more materials are used, a mixture of these materials can also be placed in the crucible, heated, and evaporated to form the light-emitting layer 5.

[0277] The vacuum level during deposition is not limited as long as it does not significantly impair the effects of the present invention, but is typically 0.1 × 10⁻⁶. -6 Torr(0.13×10 -4 Pa) or above, 9.0×10 -6 Torr(12.0×10-4 The pressure is less than or equal to Pa. The deposition rate is not limited as long as it does not significantly impair the effects of the present invention, but is usually 0.1 Å / sec or more and 5.0 Å / sec or less. The film deposition temperature during deposition is not limited as long as it does not significantly impair the effects of the present invention, but is preferably 10°C or more and 50°C or less.

[0278] [Hole Blocking Layer 6] A hole-blocking layer 6 may be provided between the light-emitting layer 5 and the electron injection layer 8, which will be described later. The hole-blocking layer 6 is a layer that is laminated on top of the light-emitting layer 5 so as to be in contact with the interface of the light-emitting layer 5 on the cathode 9 side.

[0279] The hole blocking layer 6 has two roles: preventing holes moving from the anode 2 from reaching the cathode 9, and efficiently transporting electrons injected from the cathode 9 towards the light-emitting layer 5. The required properties 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 a high excited triplet level (T1).

[0280] Examples of materials for the hole blocking layer 6 that satisfy these conditions include mixed ligand complexes such as bis(2-methyl-8-quinolinolato)(phenolato)aluminum and bis(2-methyl-8-quinolinolato)(triphenylsilanolato)aluminum, metal complexes such as bis(2-methyl-8-quinolato)aluminum-μ-oxo-bis-(2-methyl-8-quinolinolato)aluminum dinuclear metal complex, styryl compounds such as distyrylbiphenyl derivatives (Japanese Patent Publication No. 11-242996), triazole derivatives such as 3-(4-biphenylyl)-4-phenyl-5(4-tert-butylphenyl)-1,2,4-triazole (Japanese Patent Publication No. 7-41759), and phenanthroline derivatives such as basocproine (Japanese Patent Publication No. 10-79297). Furthermore, compounds having at least one pyridine ring substituted at the 2,4, and 6 positions, as described in International Publication No. 2005 / 022962, are also preferred as materials for the hole blocking layer 6.

[0281] There are no restrictions on the method of forming the hole blocking layer 6; it can be formed in the same manner as the method of forming the light-emitting layer 5 described above. The thickness of the hole blocking layer 6 is arbitrary as long as it does not significantly impair the effects of the present invention, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

[0282] [Electron transport layer 7] The electron transport layer 7 is provided between the light-emitting layer 5 or hole element layer 6 and the electron injection layer 8 with the aim of further improving the current efficiency of the device. The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode 9 towards the light-emitting layer 5 between electrodes under an applied electric field. The electron transport compound used in the electron transport layer 7 must have high electron injection efficiency from the cathode 9 or the electron injection layer 8, and high electron mobility, enabling it to efficiently transport the injected electrons.

[0283] Examples of electron-transporting compounds that satisfy these conditions include, for example, metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Publication No. 59-194393), metal complexes of 10-hydroxybenzo[h]quinoline, oxadiazole derivatives, distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolbenzene (U.S. Patent No. 5645948), quinoxaline compounds (Japanese Patent Publication No. 6-207169), phenanthroline derivatives (Japanese Patent Publication No. 5-331459), 2-t-butyl-9,10-N,N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide.

[0284] The thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less. The electron transport layer 7 is formed by laminating it onto the light-emitting layer 5 or hole-blocking layer 6 using a wet deposition method or vacuum deposition method, similar to the light-emitting layer 5. Vacuum deposition is usually used.

[0285] [Electron injection layer 8] The electron injection layer 8 plays the role of efficiently injecting electrons injected from the cathode 9 into the electron transport layer 7 or the light-emitting layer 5. To efficiently perform electron injection, 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.

[0286] Inserting an ultrathin insulating film (thickness of about 0.1 to 5 nm) of LiF, MgF2, Li2O, Cs2CO3, etc. as an electron injection layer 8 at the interface between the cathode 9 and the electron transport layer 7 is also an effective method to improve the efficiency of the device (Appl. Phys. Lett., Vol. 70, p. 152, 1997; Japanese Patent Publication No. 10-74586; IEEE Trans. Electron. Devices, Vol. 44, p. 1245, 1997; SID 04 Digest, p. 154). Furthermore, doping organic electron transport materials, such as nitrogen-containing heterocyclic compounds like bathophenanthroline and metal complexes like aluminum complexes of 8-hydroxyquinoline, with alkali metals such as sodium, potassium, cesium, lithium, and rubidium (as described in Japanese Patent Publication No. 10-270171, Japanese Patent Publication No. 2002-100478, Japanese Patent Publication No. 2002-100482, etc.) is preferable because it improves electron injection and transport properties and allows for the simultaneous achievement of excellent film quality. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

[0287] The electron injection layer 8 is formed by laminating it onto the light-emitting layer 5 or the hole-blocking layer 6 or electron transport layer 7 located thereon, using a wet deposition method or vacuum deposition method, similar to the light-emitting layer 5. The details for the wet film deposition method are the same as those for the light-emitting layer 5 described above.

[0288] [Cathode 9] The cathode 9 plays the role of injecting electrons into the layer on the light-emitting layer 5 side (such as the electron injection layer 8 or the light-emitting layer 5). While the material used for the anode 2 can be used for the cathode 9, it is preferable to use a metal with a low work function for efficient electron injection. Examples of metals with low work functions include tin, magnesium, indium, calcium, aluminum, silver, and their alloys. Specific examples include low-work-function alloy electrodes such as magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys.

[0289] In terms of the stability of the element, it is preferable to protect the cathode 9, which is made of a metal with a low work function, by laminating a metal layer with a high work function and stability to the atmosphere on top of the cathode 9. Examples of metals to be laminated include aluminum, silver, copper, nickel, chromium, gold, and platinum. The film thickness of the cathode is usually the same as that of anode 2.

[0290] [Other components] The above explanation has focused on the element with the layer configuration shown in Figure 1. However, in the organic electroluminescent element of the present invention, any other layer may be present between the anode 2 and cathode 9 and the light-emitting layer 5, as long as it does not impair the performance. Furthermore, any layer other than the light-emitting layer 5 may be omitted.

[0291] For example, for a similar purpose to the hole blocking layer 8, it is also effective to provide an electron blocking layer between the hole transport layer 4 and the light-emitting layer 5. The electron blocking layer has two roles: it prevents electrons moving from the light-emitting layer 5 from reaching the hole transport layer 4, thereby increasing the probability of recombination with holes within the light-emitting layer 5 and confining the generated excitons within the light-emitting layer 5; and it efficiently transports holes injected from the hole transport layer 4 toward the light-emitting layer 5.

[0292] The characteristics required for an electron stopping layer include high hole transport capability, a large energy gap (the difference between HOMO and LUMO), and a high excited triplet level (T1). When the light-emitting layer 5 is formed by a wet deposition method, it is preferable to also form the electron blocking layer by a wet deposition method, as this facilitates device manufacturing. Therefore, it is preferable that the electron blocking layer also has suitability for wet film deposition. Examples of materials used for such an electron blocking layer include copolymers of dioctylfluorene and triphenylamine, such as F8-TFB (International Publication No. 2004 / 084260).

[0293] It is also possible to stack the cathode 9, electron injection layer 8, electron transport layer 7, hole blocking layer 6, light-emitting layer 5, hole transport layer 4, hole injection layer 3, and anode 2 on a substrate 1 in that order. It is also possible to place the organic electroluminescent element of the present invention between two substrates, at least one of which is highly transparent. It is also possible to create a structure with multiple layers of the layer configuration shown in Figure 1 (a structure in which multiple light-emitting units are stacked). In this case, instead of using inter-stage (inter-light-emitting unit) interface layers (two layers if the anode is ITO and the cathode is Al), using a charge generation layer such as V2O5 reduces the barriers between stages, which is more preferable from the viewpoint of luminous efficiency and driving voltage.

[0294] The present invention can be applied to any of the following types of organic electroluminescent devices: a single element, an element consisting of an array-like structure, or a structure in which the anode and cathode are arranged in an XY matrix.

[0295] [Display devices and lighting devices] The display device and lighting device of the present invention utilize 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 according to conventional methods using the organic electroluminescent element of the present invention.

[0296] For example, the display device and lighting device of the present invention can be formed by a method such as that described in "Organic EL Display" (Ohmsha, published August 20, 2004, authored by Shizuka Tokito, Chihaya Adachi, and Hideyuki Murata). [Examples]

[0297] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples. The present invention can be modified and implemented as such without departing from its spirit.

[0298] [Ink preparation] [Example 1] Compound 1 (charge transport material) having the structure shown in formula (7) below and compound 2 (luminescent material) having the structure shown in formula (8) below were mixed in a mass ratio of 80:20 to obtain luminescent layer material 1. To luminescent layer material 1, 2% by mass of 2,6-di-tert-butylphenol (BHB) was added, and then methyl cyclopentanone-2-carboxylate was added so that luminescent layer material 1 accounted for 2.5% by mass of the total ink amount (BHB concentration 500 ppm). After replacing the atmosphere inside the container with nitrogen, the mixture was heated and stirred at 68°C for 1 hour to dissolve it, and luminescent layer ink 1 was prepared.

[0299] [ka]

[0300] [Example 2] Luminescent layer ink 2 was prepared in the same manner as in Example 1, except that dimethyl phthalate was added instead of methyl cyclopentanone-2-carboxylate.

[0301] [Comparative Example 1] A light-emitting layer ink 3 was prepared in the same manner as in Example 1, except that benzyl benzoate was added instead of methyl cyclopentanone-2-carboxylate.

[0302] [Measurement of surface tension] Surface tension was measured using the pendant drop method with a contact angle meter DM500 manufactured by Kyowa Interface Science Co., Ltd. A 3 μL droplet of ink was formed on the tip of a syringe, and its shape was photographed after 10 seconds. Using the analysis software FAMAS, the surface tension was calculated from this shape using the Fitting-Laplace method. For each ink, droplet creation and measurement were repeated 10 times, and the average was used as the surface tension of the ink.

[0303] [Measurement and Storage] After preparing each luminescent layer ink, the nitrogen-filled ink vials were cooled to room temperature. The vials were then opened to the atmosphere, and half of the ink was immediately taken out for the first surface tension measurement (initial surface tension). The remaining half of the ink was resealed in an atmospheric environment and stored at room temperature for 28 days. After that, a second surface tension measurement was performed on the stored ink (surface tension after 28 days).

[0304] [Surface tension measurement results] Table 1 shows the measured surface tension values ​​and their changes after the initial measurement and 28 days for the luminescent layer inks of Examples 1 and 2 and Comparative Example 1.

[0305] [Table 1]

[0306] As shown in Table 1, by using an aliphatic ester solvent or aromatic diester solvent having two or more carbonyl groups in an ink containing a specific phenol derivative, the change in surface tension of the ink during long-term storage was reduced, and a highly stable organic electroluminescent light-emitting element composition was obtained.

[0307] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible without departing from the intent and scope of the invention. This application is based on Japanese Patent Application No. 2021-078651 and Japanese Patent Application No. 2021-078652, both filed on May 6, 2021, which are incorporated herein by reference in their entirety. [Explanation of symbols]

[0308] 1 circuit board 2 Anode 3. Hole injection layer 4. Hole transport layer 5. Emitting layer 6. Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Organic electroluminescent element

Claims

1. The material comprises a functional material, a compound represented by the following formula (1), and an aliphatic ester solvent having two or more carbonyl groups. A composition for an organic electroluminescent element, wherein the aliphatic ester solvent having two or more carbonyl groups is a compound having one ester group and one ketone group. 【Chemistry 1】 [In the above formula, a is an integer from 0 to 4. R １ , R ２ Each of these independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. If a is an integer between 2 and 4, multiple R ２ They may be the same or they may be different.

2. The organic electroluminescent element composition according to claim 1, wherein the aliphatic ester solvent having two or more carbonyl groups is a solvent represented by the following formula (9-2). 【Chemistry 2】 [In the above formula, R ２７ represents an alkylene group. R ２８ , R ２９ each independently represents an alkyl group. R ２７ and R ２８ , or R ２７ and R ２９ may combine with each other to form a ring. ]

3. The organic electroluminescent element composition according to claim 1, wherein the compound represented by formula (1) is the compound represented by the following formula (1-1). 【Transformation 3】 [In the above formula, b is an integer from 0 to 3. R ３ , R ４ , R ５ Each independently represents an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms. When b is an integer between 2 and 3, multiple R ５ They may be the same or they may be different.

4. The organic electroluminescent element composition according to claim 3, wherein the compound represented by formula (1-1) is the compound represented by the following formula (1-2). 【Chemistry 4】 [In the above formula, b, R ５ b, R in formula (1-1) above. ５ This is synonymous with [the above].

5. The organic electroluminescent element composition according to claim 1, comprising an iridium complex as the functional material.

6. The organic electroluminescent element composition according to claim 5, comprising an iridium complex represented by the following formula (2) as the functional material. 【Transformation 5】 [In the above formula, R ７ , R ８ Each of these is independently one of the following, or a combination thereof: an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylsilyl group having 1 to 20 carbon atoms, an arylsilyl group having 6 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 1 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 30 carbon atoms. These groups may further have substituents. ７ , R ８ If multiple R ７ , R ８ They may be the same or different. Adjacent R atoms bonded to the benzene ring. ７ or R ８ These elements may be bonded to each other to form a ring that condenses around the benzene ring. d is an integer between 0 and 4. e is an integer between 0 and 3. m is an integer between 1 and 20. n is an integer between 0 and 2. Ring A is one of the following: pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, oxazole ring, thiazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, azatriphenylene ring, or carboline ring. Ring A may have substituents, which may be any of the following, or combinations thereof: a fluorine atom, a chlorine atom, a bromine atom, a C1-C20 alkyl group, a C7-C40 (hetero)aralkyl group, a C1-C20 alkoxy group, a C3-C20 (hetero)aryloxy group, a C1-C20 alkylsilyl group, a C6-C20 arylsilyl group, a C2-C20 alkylcarbonyl group, a C7-C20 arylcarbonyl group, a C2-C20 alkylamino group, a C6-C20 arylamino group, and a C3-C20 (hetero)aryl group. Adjacent substituents bonded to ring A may bond to each other to form a condensed ring with ring A. Z １ This represents a directly bonded or m+1 valent aromatic linking group. L １ represents an auxiliary ligand. l is an integer between 1 and 3. If there are multiple auxiliary ligands, they may be different or identical.

7. Said Z １ The organic electroluminescent element composition according to claim 6, wherein it contains a trivalent group represented by the following formula (2-2A) or (2-2B). 【Transformation 6】

8. A method for manufacturing an organic electroluminescent element, comprising the step of forming an emissive layer by a wet film deposition method using the organic electroluminescent element composition described in any one of claims 1 to 7.

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