JP2018111751A - Light emitting material, compound and organic light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting material that emits light of a deep blue color with efficiency.SOLUTION: The present invention provides a light emitting material in which: to position 1 of a benzene ring, bound is a carbazole group at N, and to position 4, bound is position 2 of 1,3,5-triazine substituted with a substituted/unsubstituted phenyl group at positions 4,6. The position 2 of the benzene ring represents a substituted/unsubstituted alkyl group, and the others represent a hydrogen atom or a substituent, where at least one of position 2 to position 4 of carbazole is a substituted/unsubstituted alkyl group, and at least one of position 5 to position 7 is a substituted/unsubstituted alkyl group.SELECTED DRAWING: None

Description

  The present invention relates to a light emitting material having high luminous efficiency and an organic light emitting device such as an organic electroluminescence device (organic EL device) using the same.

  Researches for increasing the light emission efficiency of organic light-emitting devices such as organic electroluminescence devices are being actively conducted. In particular, various efforts have been made to increase the light emission efficiency by newly developing and combining electron transport materials, hole transport materials, light emitting materials, and the like constituting the organic electroluminescence element. Among them, research on organic electroluminescence devices using compounds containing a carbazole structure or a 2,4,6-triphenyl-1,3,5-triazine structure can be found, and several proposals have been made so far. Has been made.

For example, Patent Document 1 describes that a compound having a structure represented by the following general formula is used as an electron transport material of an electron transport layer of an organic electroluminescence element. In the following general formula, n is 1 or 2, Ar is an arylene group or heteroarylene group, R ₃ and R ₄ are a hydrogen atom or an aryl group, and X _{1 to} X ₃ are ═CR— or ═ N-, R is a hydrogen atom or a substituent, and Cz is defined as a carbazolyl group.

As a compound represented by the above general formula, Patent Document 1 exemplifies Compound A having the following structure, and also describes an example of an organic electroluminescence device using the compound for an electron transport layer. However, no investigation has been made on compounds in which a substituent is introduced into the carbazolyl group of Compound A. Also, Patent Document 1 does not discuss the usefulness of Compound A as a light emitting material.

Patent Document 2 describes that a compound having a structure represented by the following general formula emits blue fluorescence, and that the compound is useful as a light emitting device material. In the following general formula, R ¹¹ and R ¹² are a hydrogen atom, an aliphatic hydrocarbon group, an aryl group or a heterocyclic group, R ¹ and R ² are substituents not containing a hydrogen atom or an amino group, and L Is defined as a linking group. Patent Document 2 describes that an organic light-emitting device using Compound A as a light-emitting material emits blue fluorescence. However, even in Patent Document 2, no study is made on a compound in which a substituent is introduced into the carbazolyl group of Compound A.

Patent Document 3 describes that a compound having a structure represented by the following general formula can emit blue delayed fluorescence and that the compound is useful as a light emitting device material. However, the general formula described in Patent Document 3 includes a very wide range of compounds, and the relationship between the substituent and the light emission efficiency, and the relationship between the substituent and the light emission color have not been sufficiently studied. .

JP 2009-21336 A JP 2002-193952 A WO2015 / 175678

As described above, compounds having a carbazole structure and a 2,4,6-triphenyl-1,3,5-triazine structure have been proposed as materials for organic EL devices. Patent Document 2 describes that the compound A emits blue fluorescence. However, when the present inventors have evaluated the light emission characteristics of Compound A, the light emission characteristics are not sufficiently satisfactory, and it is necessary to provide a light emitting material that can efficiently emit deep blue light. found.
Therefore, the present inventors pay attention to the substituents of the compound containing a carbazole structure and a 2,4,6-triphenyl-1,3,5-triazine structure, and variously change the type and position of the substituent, The relationship between the type of substituent and the position of substitution and the light emission characteristics was investigated. As a result, there is a fixed relationship between the type and position of the substituent and the light emission characteristics, and by specifying the type and position of the substituent, the target light emission efficiency in deep blue can be significantly increased. I found that there is sex. As described above, the compounds described in Patent Documents 1 and 2 including a carbazole structure and a 2,4,6-triphenyl-1,3,5-triazine structure do not have a substituent. Further, although Patent Document 3 evaluates the light emission characteristics of a large number of compound examples included in the above general formula, focusing on specific substituents, the relationship between the substitution position, light emission efficiency, and light emission color is examined. It has not been described. For this reason, it cannot be predicted from these documents that the luminous efficiency in deep blue is remarkably improved by specifying the type and position of the substituent.

  Under such circumstances, the present inventors aim to further increase the luminous efficiency of deep blue light for a compound containing a carbazole structure and a 2,4,6-triphenyl-1,3,5-triazine structure. Repeated research. In addition, a general formula of a compound that has a high emission efficiency in deep blue and is useful as a light-emitting material has been derived, and studies have been conducted with the aim of generalizing the structure of an organic light-emitting device that can provide high emission efficiency even in deep blue. It was.

  As a result of intensive studies, the present inventors have found that a substituted or unsubstituted alkyl group is present at a specific position of a compound containing a carbazole structure and a 2,4,6-triphenyl-1,3,5-triazine structure. As a result of the introduction, the inventors have found that the emission color becomes deep blue, and extremely high luminous efficiency can be obtained with the deep blue. In addition, it has been found that such a group of compounds is useful as a delayed fluorescent material, and it has been clarified that an organic light-emitting device having high emission efficiency can be provided at low cost. The present invention has been proposed based on such knowledge, and specifically has the following configuration.

［一般式（１）において、Ｒ^１〜Ｒ^８、Ｒ^１２およびＲ^１４〜Ｒ^２５は各々独立に水素原子または置換基を表し、Ｒ^１１は置換もしくは無置換のアルキル基を表す。ただし、Ｒ^２〜Ｒ^４の少なくとも１つは置換もしくは無置換のアルキル基であり、Ｒ^５〜Ｒ^７の少なくとも１つは置換もしくは無置換のアルキル基である。］
［２］ 前記一般式（１）のＲ^３およびＲ^６の少なくとも一方が、置換もしくは無置換のアルキル基である、［１］に記載の発光材料。
［３］ 前記一般式（１）のＲ^２〜Ｒ^４のうちの１つとＲ^５〜Ｒ^７のうちの１つが、置換もしくは無置換のアルキル基である、［１］または［２］に記載の発光材料。
［４］ 前記一般式（１）のＲ^１およびＲ^８の少なくとも一方が、水素原子である、［１］〜［３］のいずれか１項に記載の発光材料。
［５］ 前記一般式（１）のＲ^１２、Ｒ^１４、Ｒ^１５の少なくとも１つが、置換もしくは無置換のアルキル基である、［１］〜［４］のいずれか１項に記載の発光材料。
［６］ 前記一般式（１）のＲ^１５が置換もしくは無置換のアルキル基である、［５］に記載の発光材料。
［７］ 前記アルキル基が無置換のアルキル基である、［１］〜［６］のいずれか１項に記載の発光材料。
［８］ 前記置換もしくは無置換のアルキル基におけるアルキル基の炭素数が１〜３である、［１］〜［７］のいずれか１項に記載の発光材料。
［９］ 下記一般式（１）で表される化合物。

［一般式（１）において、Ｒ^１〜Ｒ^８、Ｒ^１２およびＲ^１４〜Ｒ^２５は各々独立に水素原子または置換基を表し、Ｒ^１１は置換もしくは無置換のアルキル基を表す。ただし、Ｒ^２〜Ｒ^４の少なくとも１つは置換もしくは無置換のアルキル基であり、Ｒ^５〜Ｒ^７の少なくとも１つは置換もしくは無置換のアルキル基である。］
［１０］ 下記一般式（１）で表される構造を有する遅延蛍光体。

［一般式（１）において、Ｒ^１〜Ｒ^８、Ｒ^１２およびＲ^１４〜Ｒ^２５は各々独立に水素原子または置換基を表し、Ｒ^１１は置換もしくは無置換のアルキル基を表す。ただし、Ｒ^２〜Ｒ^４の少なくとも１つは置換もしくは無置換のアルキル基であり、Ｒ^５〜Ｒ^７の少なくとも１つは置換もしくは無置換のアルキル基である。］
［１１］ 下記一般式（１）で表される化合物を含む発光層を基板上に有する有機発光素子。

［一般式（１）において、Ｒ^１〜Ｒ^８、Ｒ^１２およびＲ^１４〜Ｒ^２５は各々独立に水素原子または置換基を表し、Ｒ^１１は置換もしくは無置換のアルキル基を表す。ただし、Ｒ^２〜Ｒ^４の少なくとも１つは置換もしくは無置換のアルキル基であり、Ｒ^５〜Ｒ^７の少なくとも１つは置換もしくは無置換のアルキル基である。］
［１２］ 遅延蛍光を放射する、［１１］に記載の有機発光素子。
［１３］ 前記発光層にホスト材料を含む、［１１］または［１２］に記載の有機発光素子。
［１４］ 前記発光層における一般式（１）で表される化合物の含有量が５０重量％未満である、［１１］〜［１３］のいずれか１項に記載の有機発光素子。 [1] A light emitting material comprising a compound represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ]
[2] The light emitting material according to [1], wherein at least one of R ³ and R ^{6 in} the general formula (1) is a substituted or unsubstituted alkyl group.
[3] As described in [1] or [2], one of R ^{2 to} R ⁴ and one of R ^{5 to} R ^{7 in} the general formula (1) is a substituted or unsubstituted alkyl group. Luminescent material.
[4] The luminescent material according to any one of [1] to [3], wherein at least one of R ¹ and R ^{8 in} the general formula (1) is a hydrogen atom.
[5] The luminescent material according to any one of [1] to [4], wherein at least one of R ¹² , R ¹⁴ , and R ^{15 in} the general formula (1) is a substituted or unsubstituted alkyl group. .
[6] The luminescent material according to [5], wherein R ^{15 in the} general formula (1) is a substituted or unsubstituted alkyl group.
[7] The luminescent material according to any one of [1] to [6], wherein the alkyl group is an unsubstituted alkyl group.
[8] The light emitting material according to any one of [1] to [7], wherein the alkyl group in the substituted or unsubstituted alkyl group has 1 to 3 carbon atoms.
[9] A compound represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ]
[10] A delayed phosphor having a structure represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ]
[11] An organic light emitting device having a light emitting layer containing a compound represented by the following general formula (1) on a substrate.

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ]
[12] The organic light-emitting device according to [11], which emits delayed fluorescence.
[13] The organic light emitting device according to [11] or [12], wherein the light emitting layer contains a host material.
[14] The organic light-emitting device according to any one of [11] to [13], wherein the content of the compound represented by the general formula (1) in the light-emitting layer is less than 50% by weight.

  The compound of the present invention is deep blue and has high luminous efficiency, and is useful as a light emitting material. The compounds of the present invention include those that emit delayed fluorescence. An organic light emitting device using the compound of the present invention as a light emitting material can realize high luminous efficiency.

It is a schematic sectional drawing which shows the layer structural example of an organic electroluminescent element. It is an ultraviolet-visible absorption spectrum, an emission spectrum, and a phosphorescence spectrum of the compounds 1 and 2 and the comparative compounds 1 and 2. It is a transient decay curve of light emission of each doped film doped with compounds 1 and 2 and comparative compounds 1 and 2, respectively. It is the emission spectrum of the elements 1 and 2 and the comparative elements 1 and 2. 4 is a graph showing external quantum efficiency-current density characteristics of elements 1 and 2 and comparative elements 1 and 2.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. In addition, the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all the hydrogen atoms in the molecule may be ¹ H, or a part or all of the hydrogen atoms are ² H. (Deuterium D) may be used.
The “electron donating group” in the present specification means a substituent having a negative Hammett σ _p value. The numerical description and the substituents for Hammett sigma _p value, Hansch, C.et.al., Chem.Rev., Reference may be made to the description of sigma _p value of 91,165-195 (1991).

[Compound represented by general formula (1)]
The luminescent material of the present invention is characterized by comprising a compound represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. Among R ^{1 to} R ⁸ , R ¹¹ , R ^12, and R ^{14 to} R ²⁵ , a plurality of substituents including the above substituted or unsubstituted alkyl group may be the same as or different from each other.

Of R ^{2 to} R ⁴ , the number of substituted or unsubstituted alkyl groups may be only one or two or more, but one of R ^{2 to} R ⁴ Or it is preferable that two are a substituted or unsubstituted alkyl group. Among R ^{2 to} R ⁴ , it is preferable that at least R ³ is a substituted or unsubstituted alkyl group. That is, when only one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, R ³ is preferably a substituted or unsubstituted alkyl group. When ^{two of} R ^{2 to} R ⁴ are substituted or unsubstituted alkyl groups, any combination of R ² and R ³ , R ² and R ⁴ , R ³ and R ⁴ is substituted or Although it may be an unsubstituted alkyl group, it is preferable that R ² and R ³ are substituted or unsubstituted alkyl groups, or R ³ and R ⁴ are substituted or unsubstituted alkyl groups. Further, all of R ^{2 to} R ⁴ may be substituted or unsubstituted alkyl groups.
Of R ^{5 to} R ⁷ , the number of substituted or unsubstituted alkyl groups may be only one or two or more, but one of R ^{5 to} R ^7. Or it is preferable that two are a substituted or unsubstituted alkyl group. Among R ^{5 to} R ⁷ , it is preferable that at least R ⁶ is a substituted or unsubstituted alkyl group. That is, when only one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group, R ⁶ is preferably a substituted or unsubstituted alkyl group. When two of R ^{5 to} R ⁷ are substituted or unsubstituted alkyl groups, any combination of R ⁵ and R ⁶ , R ⁵ and R ⁷ , R ⁶ and R ⁷ is substituted or Although it may be an unsubstituted alkyl group, it is preferable that R ⁵ and R ⁶ are substituted or unsubstituted alkyl groups, or R ⁶ and R ⁷ are substituted or unsubstituted alkyl groups. Also, all of R ^{5 to} R ⁷ may be substituted or unsubstituted alkyl groups.
The number of R ^{2 to} R ⁴ that are substituted or unsubstituted alkyl groups and the number of R ^{5 to} R ⁷ that are substituted or unsubstituted alkyl groups may be the same or different. Good, but preferably the same.

Of R ^{2 to} R ⁴ and R ^{5 to} R ⁷ , those that are not substituted or unsubstituted alkyl groups may be hydrogen atoms or substituents. R ¹ and R ⁸ may be a hydrogen atom or a substituent, but are preferably not an electron donating group such as an alkyl group, and more preferably a hydrogen atom. This avoids an increase in the HOMO level of the compound represented by the general formula (1) due to the electron donating properties of R ¹ and R ⁸ , widens the gap between HOMO-LUMO, and improves the emission color. It becomes easy to make deeper blue.

R ¹¹ represents a substituted or unsubstituted alkyl group. Since R ¹¹ is a substituted or unsubstituted alkyl group, the difference ΔE _ST between the lowest excited singlet energy E _S1 and the lowest excited triplet energy level E _T1 of the compound represented by the general formula (1) is small. Therefore, high luminous efficiency can be obtained.

R ¹² and R ^{14 to} R ²⁵ may be a hydrogen atom or a substituent, but R ¹² , R ¹⁴ , and R ¹⁵ are preferably a hydrogen atom or a substituted or unsubstituted alkyl group. , ^{R 12,} and more preferably at least ^{R 15} of R ^{14, R 15} is a substituted or unsubstituted alkyl group. Specifically, R ¹⁵ is a substituted or unsubstituted alkyl group, R ¹² and R ¹⁵ or R ¹⁴ and R ¹⁵ are substituted or unsubstituted alkyl groups, or R ¹² , R ¹⁴ , R ^15. All of these are preferably substituted or unsubstituted alkyl groups. When at least R ^{15 of} R ¹² , R ¹⁴ and R ¹⁵ is a substituted or unsubstituted alkyl group, ΔE _{ST of the} compound represented by the general formula (1) tends to be smaller.

Alkyl in the substituted or unsubstituted alkyl group represented by R ¹¹ , the substituted or unsubstituted alkyl group represented by at least one of R ^{2 to} R ⁴ , and the substituted or unsubstituted alkyl group represented by at least one of R ^{5 to} R ⁷ The group may be linear, branched or cyclic. The carbon number of the alkyl group is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 or 2. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The alkyl group may be substituted with a substituent or may be unsubstituted, but is preferably unsubstituted. For preferred ranges and specific examples of groups that can be substituted on the alkyl group, explanations and preferred ranges of substituents that can be taken by R ^{1 to} R ^{8 and the} like can be referred to, and among these, an alkoxy group is preferred.
In addition, a substituted or unsubstituted alkyl group represented by R ¹¹ , a substituted or unsubstituted alkyl group represented by at least one of R ^{2 to} R ⁴ , and a substituted or unsubstituted alkyl group represented by at least one of R ^{5 to} R ⁷ May be the same or different from each other, but when both R ³ and R ⁶ , both R ¹² and R ¹⁴ , or R ¹⁵ represents a substituted or unsubstituted alkyl group, Alternatively, the unsubstituted alkyl group is preferably the same for R ³ and R ⁶ , preferably the same for R ¹² and R ¹⁴ , and preferably the same for R ¹¹ and R ¹⁵ .

Examples of the substituent that R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ can take include, for example, a hydroxy group, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and 1 to 1 carbon atoms. 20 alkylthio groups, C1-C20 alkyl-substituted amino groups, C1-C20 aryl-substituted amino groups, C6-C40 aryl groups, C3-C40 heteroaryl groups, C2-C2 10 alkenyl group, C2-C10 alkynyl group, C2-C20 alkylamide group, C7-C21 arylamide group, C3-C20 trialkylsilyl group, etc. are mentioned. Among these specific examples, those that can be substituted with a substituent may be further substituted. More preferable substituents are an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an alkyl-substituted amino group having 1 to 20 carbon atoms, and an alkyl group having 1 to 20 carbon atoms. An aryl-substituted amino group, an aryl group having 6 to 40 carbon atoms, and a heteroaryl group having 3 to 40 carbon atoms.

The compound represented by the general formula (1) preferably has a line-symmetric structure. R ¹ and R ⁸ , R ² and R ⁷ , R ³ and R ⁶ , R ⁴ and R ⁵ , R ¹¹ and R ¹⁵ , R ¹² and R ¹⁴ , R ¹⁶ and R ²⁵ , R ¹⁷ and R ²⁴ , R ¹⁸ and R ²³ , R ¹⁹ and R ²² , R ²⁰ and R ²¹ are preferably the same.

Below, the specific example of a compound represented by General formula (1) is illustrated. However, the compound represented by the general formula (1) that can be used in the present invention should not be limitedly interpreted by these specific examples.

The molecular weight of the compound represented by the general formula (1) is, for example, 1500 or less when the organic layer containing the compound represented by the general formula (1) is intended to be formed by vapor deposition. Preferably, it is preferably 1200 or less, more preferably 1000 or less, and even more preferably 900 or less. The lower limit of the molecular weight is the molecular weight of the minimum compound represented by the general formula (1).
The compound represented by the general formula (1) may be formed by a coating method regardless of the molecular weight. If a coating method is used, a film can be formed even with a compound having a relatively large molecular weight.

By applying the present invention, it is also conceivable to use a compound containing a plurality of structures represented by the general formula (1) in the molecule as a light emitting material.
For example, it is conceivable to use a polymer obtained by previously polymerizing a polymerizable group in the structure represented by the general formula (1) and polymerizing the polymerizable group as a light emitting material. Specifically, a monomer containing a polymerizable functional group is prepared in any of R ^{1 to} R ⁸ , R ¹¹ , R ¹² and R ^{14 to} R ^{25 in} the general formula (1), and this is polymerized alone. Alternatively, it is conceivable to obtain a polymer having a repeating unit by copolymerization with other monomers and to use the polymer as a light emitting material. Alternatively, it is also possible to obtain a dimer or trimer by coupling compounds having a structure represented by the general formula (1) and use them as a light emitting material.

As an example of the polymer having a repeating unit including the structure represented by the general formula (1), a polymer including a structure represented by the following general formula (11) or (12) can be given.

In the general formula (11) or (12), Q represents a group including the structure represented by the general formula (1), and L ¹ and L ² represent a linking group. Carbon number of a coupling group becomes like this. Preferably it is 0-20, More preferably, it is 1-15, More preferably, it is 2-10. And preferably has a structure represented by - linking group ^-X 11 ^{-L 11.} Here, X ¹¹ represents an oxygen atom or a sulfur atom, and is preferably an oxygen atom. L ¹¹ represents a linking group, and is preferably a substituted or unsubstituted alkylene group, or a substituted or unsubstituted arylene group, and is a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, or a substituted or unsubstituted group A phenylene group is more preferable.
In General Formula (11) or (12), R ¹⁰¹ , R ¹⁰² , R ¹⁰³ and R ¹⁰⁴ each independently represent a substituent. Preferably, it is a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 6 carbon atoms, or a halogen atom, more preferably an unsubstituted alkyl group having 1 to 3 carbon atoms. An unsubstituted alkoxy group having 1 to 3 carbon atoms, a fluorine atom, and a chlorine atom, and more preferably an unsubstituted alkyl group having 1 to 3 carbon atoms and an unsubstituted alkoxy group having 1 to 3 carbon atoms.
The linking group represented by L ¹ and L ² may be bonded to any of R ^{1 to} R ⁸ , R ¹¹ , R ¹² and R ^{14 to} R ²⁵ in the structure of the general formula (1) constituting Q. it can. Two or more linking groups may be linked to one Q to form a crosslinked structure or a network structure.

Specific examples of the structure of the repeating unit include structures represented by the following formulas (13) to (16).

A polymer having a repeating unit containing these formulas (13) to (16) is hydroxy in any of R ^{1 to} R ⁸ , R ¹¹ , R ¹² and R ^{14 to} R ²⁵ having the structure of the general formula (1). It can be synthesized by introducing a group, reacting the following compound as a linker to introduce a polymerizable group, and polymerizing the polymerizable group.

  The polymer containing the structure represented by the general formula (1) in the molecule may be a polymer composed only of repeating units having the structure represented by the general formula (1), or other structures may be used. It may be a polymer containing repeating units. The repeating unit having a structure represented by the general formula (1) contained in the polymer may be a single type or two or more types. Examples of the repeating unit not having the structure represented by the general formula (1) include those derived from monomers used in ordinary copolymerization. Examples thereof include a repeating unit derived from a monomer having an ethylenically unsaturated bond such as ethylene and styrene.

[Synthesis Method of Compound Represented by General Formula (1)]
The compound represented by the general formula (1) is a novel compound.
The compound represented by the general formula (1) can be synthesized by combining known reactions. For example, it can be synthesized by reacting the following two compounds.

For the explanation of R ^{1 to} R ⁸ , R ¹¹ , R ¹² and R ^{14 to} R ^{25 in} the above reaction formula, the corresponding description in general formula (1) can be referred to. X represents a halogen atom, and examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atom is preferable.
The above reaction is an application of a known coupling reaction, and known reaction conditions can be appropriately selected and used. The details of the above reaction can be referred to the synthesis examples described below. The compound represented by the general formula (1) can also be synthesized by combining other known synthesis reactions.

[Organic light emitting device]
The compound represented by the general formula (1) of the present invention is deep blue and has high luminous efficiency, and is useful as a light emitting material for an organic light emitting device. For this reason, the compound represented by General formula (1) of this invention can be effectively used as a luminescent material for the light emitting layer of an organic light emitting element. Moreover, you may use the compound represented by General formula (1) of this invention as a host or an assist dopant.
The compound represented by the general formula (1) includes a delayed fluorescent material (delayed phosphor) that emits delayed fluorescence. That is, the present invention relates to a delayed phosphor having a structure represented by the general formula (1), an invention using a compound represented by the general formula (1) as a delayed phosphor, and a general formula (1). An invention of a method for emitting delayed fluorescence using the represented compound is also provided. An organic light emitting device using such a compound as a light emitting material emits delayed fluorescence and has a feature of high luminous efficiency. The principle will be described below by taking an organic electroluminescence element as an example.

  In an organic electroluminescence element, carriers are injected into a light emitting material from both positive and negative electrodes to generate an excited light emitting material and emit light. In general, in the case of a carrier injection type organic electroluminescence element, 25% of the generated excitons are excited to the excited singlet state, and the remaining 75% are excited to the excited triplet state. Therefore, the use efficiency of energy is higher when phosphorescence, which is light emission from an excited triplet state, is used. However, since the excited triplet state has a long lifetime, energy saturation occurs due to saturation of the excited state and interaction with excitons in the excited triplet state, and in general, the quantum yield of phosphorescence is often not high. On the other hand, the delayed fluorescent material transitions to the excited triplet state due to intersystem crossing, etc., and then crosses back to the excited singlet state due to triplet-triplet annihilation or absorption of thermal energy, and emits fluorescence. To do. In the organic electroluminescence device, it is considered that a thermally activated delayed fluorescent material by absorption of thermal energy is particularly useful. When a delayed fluorescent material is used for the organic electroluminescence element, excitons in the excited singlet state emit fluorescence as usual. On the other hand, excitons in the excited triplet state absorb heat generated by the device and cross between the excited singlets to emit fluorescence. At this time, since the light is emitted from the excited singlet, the light is emitted at the same wavelength as the fluorescence, but the light lifetime (luminescence lifetime) generated by the reverse intersystem crossing from the excited triplet state to the excited singlet state is normal. Since the fluorescence becomes longer than the fluorescence and phosphorescence, it is observed as fluorescence delayed from these. This can be defined as delayed fluorescence. If such a heat-activated exciton transfer mechanism is used, the ratio of the compound in an excited singlet state, which normally generated only 25%, is increased to 25% or more by absorbing thermal energy after carrier injection. It can be raised. If a compound that emits strong fluorescence and delayed fluorescence even at a low temperature of less than 100 ° C is used, the heat of the device will sufficiently cause intersystem crossing from the excited triplet state to the excited singlet state and emit delayed fluorescence. Efficiency can be improved dramatically.

By using the compound represented by the general formula (1) of the present invention as a light-emitting material of a light-emitting layer, excellent organic light-emitting devices such as an organic photoluminescence device (organic PL device) and an organic electroluminescence device (organic EL device) Can be provided. The organic photoluminescence element has a structure in which at least a light emitting layer is formed on a substrate. The organic electroluminescence element has a structure in which an organic layer is formed at least between an anode, a cathode, and an anode and a cathode. The organic layer includes at least a light emitting layer, and may consist of only the light emitting layer, or may have one or more organic layers in addition to the light emitting layer. Examples of such other organic layers include a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, and an exciton blocking layer. The hole transport layer may be a hole injection / transport layer having a hole injection function, and the electron transport layer may be an electron injection / transport layer having an electron injection function. A specific example of the structure of an organic electroluminescence element is shown in FIG. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is an electron transport layer, and 7 is a cathode.
Below, each member and each layer of an organic electroluminescent element are demonstrated. In addition, description of a board | substrate and a light emitting layer corresponds also to the board | substrate and light emitting layer of an organic photo-luminescence element.

(substrate)
The organic electroluminescence device of the present invention is preferably supported on a substrate. The substrate is not particularly limited and may be any substrate conventionally used for organic electroluminescence elements. For example, a substrate made of glass, transparent plastic, quartz, silicon, or the like can be used.

(anode)
As the anode in the organic electroluminescence element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the material which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

(cathode)
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic electroluminescence element is transparent or translucent, the emission luminance is advantageously improved.
In addition, by using the conductive transparent material mentioned in the description of the anode as a cathode, a transparent or semi-transparent cathode can be produced. By applying this, an element in which both the anode and the cathode are transparent is used. Can be produced.

(Light emitting layer)
The light emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode, and the light emitting material may be used alone for the light emitting layer. , Preferably including a luminescent material and a host material. As a luminescent material, the 1 type (s) or 2 or more types chosen from the compound group of this invention represented by General formula (1) can be used. In order for the organic electroluminescent device and the organic photoluminescent device of the present invention to exhibit high luminous efficiency, it is important to confine singlet excitons and triplet excitons generated in the light emitting material in the light emitting material. Therefore, it is preferable to use a host material in addition to the light emitting material in the light emitting layer. As the host material, an organic compound having at least one of excited singlet energy and excited triplet energy higher than that of the light emitting material of the present invention can be used. As a result, singlet excitons and triplet excitons generated in the light emitting material of the present invention can be confined in the molecules of the light emitting material of the present invention, and the light emission efficiency can be sufficiently extracted. However, even if singlet excitons and triplet excitons cannot be sufficiently confined, there are cases where high luminous efficiency can be obtained, so that host materials that can achieve high luminous efficiency are particularly limited. And can be used in the present invention. In the organic light emitting device or organic electroluminescent device of the present invention, light emission is generated from the light emitting material of the present invention contained in the light emitting layer. This emission includes both fluorescence and delayed fluorescence. However, light emission from the host material may be partly or partly emitted.
The content of the compound represented by the general formula (1) in the light emitting layer is preferably less than 50% by weight. Furthermore, the upper limit of the content of the compound represented by the general formula (1) is preferably less than 30% by weight, and the upper limit of the content is, for example, less than 20% by weight, less than 10% by weight, and 5% by weight. %, Less than 3%, less than 1%, less than 0.5% by weight. The lower limit is preferably 0.001% by weight or more, and for example, may be more than 0.01% by weight, more than 0.1% by weight, more than 0.5% by weight, and more than 1% by weight.
The host material in the light-emitting layer is preferably an organic compound that has a hole transporting ability and an electron transporting ability, prevents the emission of longer wavelengths, and has a high glass transition temperature.

Further, as another embodiment of the light emitting layer, an embodiment may be mentioned that includes a light emitting material and a host material, and further includes a compound represented by the general formula (1) as an assist dopant. As an assist dopant, 1 type (s) or 2 or more types chosen from the compound group represented by General formula (1) can be used. The compound represented by the general formula (1) used as the assist dopant preferably has a lowest excited singlet energy level higher than that of the light emitting material and a lower lowest excited singlet energy level than that of the host material. As a result, the excited singlet energy generated in the host material easily moves to the assist dopant and the light emitting material, and the excited singlet energy generated in the assist dopant and the excited singlet energy transferred from the host material to the assist dopant emits light. Move easily to material. As a result, a light emitting material in an excited singlet state is efficiently generated, and high light emission efficiency can be obtained. Further, the compound represented by the general formula (1) used as the assist dopant has a lowest excited triplet energy level lower than that of the host material, and has a lowest excited singlet energy level and a lowest excited triplet energy level. it is more preferable that the difference Delta] E _ST is less than 0.35 eV. As a result, the excited triplet energy generated in the host material easily moves to the assist dopant, and the assist dopant transitions to the excited triplet state. It can easily occur and transition to an excited singlet state. As a result of the excitation singlet energy of the assist dopant being transferred to the light emitting material, the light emitting material in the excited singlet state is generated more efficiently, and extremely high light emission efficiency can be obtained. In other words, the excited triplet energy generated by the host material or assist dopant can be effectively used for light emission of the light emitting material.
As the light-emitting material used in this embodiment, a known material can be adopted, and a fluorescent light-emitting material is preferably used, and a delayed phosphor may be used. For the description of the host material, reference can be made to the description of the host material in an embodiment in which the compound represented by the general formula (1) is used for the light emitting material.
When the compound represented by the general formula (1) is used as an assist dopant, the content of the compound represented by the general formula (1) in the light emitting layer is less than the content of the host material, and more than the content of the light emitting material. In other words, it is preferable that the relationship of “content of light emitting material <content of assist dopant <content of host material” is satisfied. Specifically, the content of the compound represented by the general formula (1) in the light emitting layer in this embodiment is preferably less than 50% by weight. Furthermore, the upper limit of the content of the compound represented by the general formula (1) is preferably less than 40% by weight, and the upper limit of the content is, for example, less than 30% by weight, less than 20% by weight, 10% by weight. It can also be less than%. The lower limit is preferably 1% by weight or more, and may be, for example, more than 3% by weight and more than 4% by weight.

(Injection layer)
The injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of light emission. There are a hole injection layer and an electron injection layer, and between the anode and the light emitting layer or the hole transport layer. Further, it may be present between the cathode and the light emitting layer or the electron transport layer. The injection layer can be provided as necessary.

(Blocking layer)
The blocking layer is a layer that can prevent diffusion of charges (electrons or holes) and / or excitons existing in the light emitting layer to the outside of the light emitting layer. The electron blocking layer can be disposed between the light emitting layer and the hole transport layer and blocks electrons from passing through the light emitting layer toward the hole transport layer. Similarly, a hole blocking layer can be disposed between the light emitting layer and the electron transporting layer to prevent holes from passing through the light emitting layer toward the electron transporting layer. The blocking layer can also be used to block excitons from diffusing outside the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also function as an exciton blocking layer. The term “electron blocking layer” or “exciton blocking layer” as used herein is used in the sense of including a layer having the functions of an electron blocking layer and an exciton blocking layer in one layer.

(Hole blocking layer)
The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer has a role of blocking holes from reaching the electron transport layer while transporting electrons, thereby improving the recombination probability of electrons and holes in the light emitting layer. As the material for the hole blocking layer, the material for the electron transport layer described later can be used as necessary.

(Electron blocking layer)
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role to block electrons from reaching the hole transport layer while transporting holes, thereby improving the probability of recombination of electrons and holes in the light emitting layer. .

(Exciton blocking layer)
The exciton blocking layer is a layer for preventing excitons generated by recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer. It becomes possible to efficiently confine in the light emitting layer, and the light emission efficiency of the device can be improved. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both can be inserted simultaneously. That is, when the exciton blocking layer is provided on the anode side, the layer can be inserted adjacent to the light emitting layer between the hole transport layer and the light emitting layer, and when inserted on the cathode side, the light emitting layer and the cathode Between the luminescent layer and the light-emitting layer. Further, a hole injection layer, an electron blocking layer, or the like can be provided between the anode and the exciton blocking layer adjacent to the anode side of the light emitting layer, and the excitation adjacent to the cathode and the cathode side of the light emitting layer can be provided. Between the child blocking layer, an electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided. When the blocking layer is disposed, at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is preferably higher than the excited singlet energy and the excited triplet energy of the light emitting material.

(Hole transport layer)
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. Known hole transport materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, Examples include amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. An aromatic tertiary amine compound and an styrylamine compound are preferably used, and an aromatic tertiary amine compound is more preferably used.

(Electron transport layer)
The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer can be provided as a single layer or a plurality of layers.
The electron transport material (which may also serve as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light emitting layer. Examples of the electron transport layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide oxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  When producing an organic electroluminescence element, the compound represented by the general formula (1) may be used not only for one organic layer (for example, an electron transport layer) but also for a plurality of organic layers. . In that case, the compound represented by General formula (1) used for each organic layer may be the same as or different from each other. For example, in addition to the electron transport layer and the light emitting layer, the injection layer, the blocking layer, the hole blocking layer, the electron blocking layer, the exciton blocking layer, the hole transport layer, and the like are also represented by the general formula (1). A compound may be used. The method for forming these layers is not particularly limited, and the layer may be formed by either a dry process or a wet process.

Below, the preferable material which can be used for an organic electroluminescent element is illustrated concretely. However, the material that can be used in the present invention is not limited to the following exemplary compounds. Moreover, even if it is a compound illustrated as a material which has a specific function, it can also be diverted as a material which has another function. In addition, R, R ′, and R _{1 to} R ₁₀ in the structural formulas of the following exemplary compounds each independently represent a hydrogen atom or a substituent. X represents a carbon atom or a hetero atom forming a ring skeleton, n represents an integer of 3 to 5, Y represents a substituent, and m represents an integer of 0 or more.

  First, preferred compounds that can also be used as a host material for the light emitting layer are listed.

  Examples of preferred compounds that can be used as the hole injection material are given below.

  Next, examples of preferred compounds that can be used as a hole transport material are listed.

  Next, examples of preferable compounds that can be used as an electron blocking material are given.

  Next, preferred compound examples that can be used as a hole blocking material are listed.

  Next, examples of preferable compounds that can be used as an electron transporting material will be given.

  Next, examples of preferable compounds that can be used as the electron injection material are given.

  Furthermore, preferable compound examples are given as materials that can be added. For example, adding as a stabilizing material can be considered.

The organic electroluminescence device produced by the above-described method emits light by applying an electric field between the anode and the cathode of the obtained device. At this time, if the light is emitted by excited singlet energy, light having a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. In addition, in the case of light emission by excited triplet energy, a wavelength corresponding to the energy level is confirmed as phosphorescence. Since normal fluorescence has a shorter fluorescence lifetime than delayed fluorescence, the emission lifetime can be distinguished from fluorescence and delayed fluorescence.
On the other hand, with regard to phosphorescence, in ordinary organic compounds such as the compounds of the present invention, the excited triplet energy is unstable, the thermal deactivation rate constant is large, and the luminescence rate constant is small. Therefore, it is hardly observable at room temperature. In order to measure the excited triplet energy of a normal organic compound, it can be measured by observing light emission under extremely low temperature conditions.

  The organic electroluminescence element of the present invention can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the present invention, an organic light emitting device with greatly improved light emission efficiency can be obtained by containing the compound represented by the general formula (1) in the light emitting layer. The organic light emitting device such as the organic electroluminescence device of the present invention can be further applied to various uses. For example, it is possible to produce an organic electroluminescence display device using the organic electroluminescence element of the present invention. For details, see “Organic EL Display” (Ohm Co., Ltd.) written by Shizushi Tokito, Chiba Adachi and Hideyuki Murata. ) Can be referred to. In particular, the organic electroluminescence device of the present invention can be applied to organic electroluminescence illumination and backlights that are in great demand.

  The features of the present invention will be described more specifically with reference to synthesis examples and examples. The following materials, processing details, processing procedures, and the like can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. The UV absorption spectrum was measured using LAMBDA950-PKA (manufactured by Perkin Elmer), the emission spectrum was measured using Fluoromax-4 (manufactured by Horiba Joban Yvon), and the transient attenuation curve was measured using Quantaurus. -Tau (manufactured by Hamamatsu Photonics) was used, and photoluminescence quantum efficiency (PL quantum efficiency) was measured using C11347-11 (manufactured by Hamamatsu Photonics). In this example, fluorescence having a light emission lifetime of 0.05 μs or more was determined as delayed fluorescence.

The difference (ΔE _ST ) between the singlet energy (E _S1 ) and the triplet energy (E _T1 ) of each material is calculated by the following method to calculate the singlet energy (E _S1 ) and the triplet energy, and ΔE _ST = E _S1 Determined by -E _T1 .
(1) Singlet energy E _S1
A sample having a thickness of 100 nm was prepared on a Si substrate by co-evaporating the measurement target compound and mCP so that the measurement target compound had a concentration of 6% by weight. The fluorescence spectrum of this sample was measured at room temperature (300K). By integrating the luminescence from immediately after the excitation light incidence to 100 nanoseconds after the incidence, a fluorescence spectrum having a luminescence intensity on the vertical axis and a wavelength on the horizontal axis was obtained. In the fluorescence spectrum, the vertical axis represents light emission and the horizontal axis represents wavelength. A tangent line was drawn with respect to the short-wave rise of the emission spectrum, and the wavelength value λedge [nm] at the intersection of the tangent line and the horizontal axis was obtained. A value obtained by converting this wavelength value into an energy value by the following conversion formula was defined as _ES1 .
Conversion formula: E _S1 [eV] = 1239.85 / λedge
For the measurement of the emission spectrum, a nitrogen laser (Lasertechnik Berlin, MNL200) was used as an excitation light source, and a streak camera (Hamamatsu Photonics, C4334) was used as a detector.
(2) Triplet energy E _T1
The same sample as the singlet energy E _S1 was cooled to 5 [K], the sample for phosphorescence measurement was irradiated with excitation light (337 nm), and the phosphorescence intensity was measured using a streak camera. By integrating the luminescence from 1 millisecond after the excitation light incidence to 10 milliseconds after the incidence, a phosphorescence spectrum having the luminescence intensity on the vertical axis and the wavelength on the horizontal axis was obtained. A tangent line was drawn with respect to the rising edge of the phosphorescence spectrum on the short wavelength side, and a wavelength value λ edge [nm] at the intersection of the tangent line and the horizontal axis was obtained. A value obtained by converting this wavelength value into an energy value by the following conversion formula was defined as _ET1 .
Conversion formula: E _T1 [eV] = 1239.85 / λedge
The tangent to the short wavelength rising edge of the phosphorescence spectrum was drawn as follows. When moving on the spectrum curve from the short wavelength side of the phosphorescence spectrum to the maximum value on the shortest wavelength side among the maximum values of the spectrum, tangents at each point on the curve are considered toward the long wavelength side. The slope of this tangent line increases as the curve rises (that is, as the vertical axis increases). The tangent drawn at the point where the value of the slope takes the maximum value was taken as the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side.
In addition, the maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the above-mentioned maximum value on the shortest wavelength side, and has the maximum slope value closest to the maximum value on the shortest wavelength side. The tangent drawn at the point where the value was taken was taken as the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side.

Synthesis Example 1 Synthesis of Compound 1

Under an argon atmosphere, 3,6-dimethylcarbazole (1.50 g, 7.68 mmol) was placed in a two-necked round bottom flask equipped with a reflux condenser, and cesium carbonate (12.5 g, 38.4 mmol) and DMF ( 100 ml) was added to obtain a suspension. After stirring for 30 minutes at room temperature, 2- (4-fluorophenyl) -4,6-diphenyl-1,3,5-triazine (2.62 g, 7.68 mmol) was poured in one portion and the reaction mixture was at 155 ° C. Stir for 12 hours. It was then diluted with water and the crude product was extracted with chloroform (3 × 30 ml). The organic phase was dried over sodium sulfate and the solvent was removed. Silica gel column chromatography was performed using dichloromethane / petroleum (1: 4) as eluent to isolate compound 1 (3.26 g, 6.68 mmol, 87%) as a white solid.
¹ H NMR (500 MHz, CDCl ₃ ) δ (ppm): 8.89-8.78 (m, 6H) 7.97 (s, 2H) 7.71-7.57 (m, 7H) 7.25 (d, J = 8.5 Hz, 2H) 7.03 ( d, J = 8.5 Hz, 2H) 2.58 (s, 6H) 2.19 (s, 3H). ¹³ C NMR (125 MHz, CDCl ₃ ) δ (ppm): 171.8, 171.2, 140.3, 139.4, 137.5, 136.2, 136.1 , 132.6, 132.0, 129.4, 129.0, 128.9, 127.9, 123.2, 120.3, 109.5, 21.4, 18.1.HRMS m / z: 516.18 [M] ⁺ . Anal. Calcd for C ₃₆ H ₂₈ N ₄ (%): C 83.69 , H 5.46, N 10.84; found: C 83.82, H 5.45, N 10.91.

Synthesis Example 2 Synthesis of Compound 2

Instead of 2- (4-fluorophenyl) -4,6-diphenyl-1,3,5-triazine used in Synthesis Example 1, 2- (4-fluoro-3,5-dimethylphenyl) -4,6- Compound 2 was synthesized according to the same procedure as in Synthesis Example 1 using diphenyl-1,3,5-triazine (2.73 g, 7.68 mmol). After evaporation of the solvent, the crude product was subjected to silica gel column chromatography using dichloromethane / petroleum (1: 4) as an eluent to obtain a yellow solid of Compound 2 in a yield of 76%.
¹ H NMR (500 MHz, CDCl3) δ (ppm): 8.85 (d, J = 8.5 Hz, 4H) 8.67 (s, 2H) 7.78 (s, 1H) 7.67-7.61 (m, 6H) 7.24 (d, J = 8.5 Hz, 2H) 6.90 (d, J = 8.5 Hz, 2H) 2.58 (s, 6H) 2.06 (s, 6H). ¹³ C NMR (125 MHz, CDCl ₃ ) δ (ppm): 138.6, 136.1, 132.6 HRMS m / z: 530.18 [M] ⁺ . Anal. Calcd for C37H30N4 (%): C 83.74, H 5.70, N 10.56; found: C 83.68, H 5.70, N 10.62.
When the thermal properties of the compounds 1 and 2 were evaluated by mass spectrometry (TGA), the temperature (decomposition temperature Td) when the mass reduction rate was 5% was more than 405 ° C., and the thermal stability was improved. It was confirmed that it was excellent.

Example 1 Production of Organic Photoluminescence Element Using Compound 1 A toluene solution of Compound 1 (concentration 1 × 10 ⁻⁵ mol / L) was prepared in a glove box under an Ar atmosphere.
Further, a thin film in which compound 1 and DPEPO are vapor-deposited from different vapor deposition sources on a quartz substrate by a vacuum vapor deposition method under a vacuum degree of 2 to 3 × 10 ⁻⁴ Pa or less, and the concentration of compound 1 is 6 mass%. (Hereinafter referred to as “compound 1 doped film”) was formed to a thickness of 60 nm to obtain an organic photoluminescence device.

Example 2 Production of Organic Photoluminescence Device Using Compound 2 Except for using Compound 2 instead of Compound 1, a toluene solution of Compound 2 and a thin film of Compound 2 and DPEPO ( Hereinafter, the “dope film of compound 2”) was prepared.

(Comparative Examples 1 and 2) Preparation of Organic Photoluminescence Device Using Comparative Compounds 1 and 2 The same procedure as in Example 1 was conducted except that Comparative Compound 1 or Comparative Compound 2 having the following structure was used instead of Compound 1. Comparative Compound 1 toluene solution, Comparative Compound 1 and DPEPO thin film (hereinafter referred to as “Comparative Compound 1 doped film”), Comparative Compound 2 toluene solution, and Comparative Compound 2 and DPEPO thin film (hereinafter referred to as “Comparative Compound 2 ") was prepared.

[Evaluation of luminous characteristics]
FIG. 2 shows an ultraviolet-visible absorption spectrum of the toluene solution prepared in each example and each comparative example, an emission spectrum at 298 K measured using 320 nm excitation light, and a phosphorescence spectrum at 77 K. In FIG. 2, “Uv-Vis” indicates an ultraviolet-visible absorption spectrum, “PL” indicates an emission spectrum, and “Phos” indicates a phosphorescence spectrum. FIG. 3 shows a transient decay curve of light emission at room temperature measured using 365 nm excitation light for the doped films prepared in each Example and each Comparative Example.
In addition, the emission maximum wavelength of each compound, singlet energy E _S1 , triplet energy E _T1 , difference ΔE _ST between E _S1 and E _T1 , photoluminescence quantum yield (PL quantum yield) of toluene solution and doped film, The emission lifetime τ _d obtained from FIG. 3 and the oxidation potential and reduction potential measured in a mixed solvent of dichloromethane and dimethylformamide are shown in Table 1.

As shown in Table 1, Compounds 1 and 2 had a maximum emission wavelength of 432 nm and a short wavelength, and had high emission efficiency. Compounds 1 and 2 have a small ΔE _ST and a long emission lifetime τ _d of 13.0 μs and 10.3 μs, confirming that they emit delayed fluorescence. On the other hand, Comparative Compound 1 had a low triplet energy E _T1 , a large ΔE _ST value, and a long emission lifetime τ _d . Therefore, it was estimated that the comparative compound 1 does not emit delayed fluorescence or is negligible even if it emits. On the other hand, Comparative Compound 2 had an emission maximum wavelength of 465 nm and a longer wavelength than Compounds 1 and 2.
Here, the twist angle of the carbazole structure and the 2,4,6-triphenyl-1,3,5-triazine structure in each compound was determined by density functional theory calculation. As a result, Compound 1, 2 and Comparative Compound 2 were compared. Compared with compound 1, it has a larger twist angle. Introduction of an alkyl group into the central phenylene group in compounds 1 and 2 and introduction of an alkyl group into 1- and 8-positions of carbazole structure in comparative compound 2 It was suggested that there is an action to increase the twist of the carbazole structure and the 2,4,6-triphenyl-1,3,5-triazine structure. Thereby, in the compounds 1 and 2, it is considered that the charge transfer excitation state is stabilized, the energy of the local excitation triplet energy state ³ LE (minimum excitation triplet energy E _T1 ) is increased, and the ΔEst is reduced.
On the other hand, as shown in Table 1, the oxidation potential of Comparative Compound 2 is lower than that of Comparative Compound 1. Therefore, the introduction of alkyl groups at the 1-position and 8-position of the carbazole structure has the effect of increasing the twist of the carbazole structure and the 2,4,6-triphenyl-1,3,5-triazine structure, and the alkyl group. It was suggested that the electron donating property has an action of lowering the oxidation potential of the carbazole structure which is a donor part. Here, the oxidation potential corresponds to the HOMO level, the reduction potential corresponds to the LUMO level, and lowering the oxidation potential means that the gap between HOMO-LUMO is narrowed. Thereby, it is considered that the emission wavelength of Comparative Compound 2 is shifted to the longer wavelength side than other compounds.

(Example 3) Production of organic electroluminescence device using compound 1 Each thin film was vacuum-deposited by vacuum deposition on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. The degree of lamination was 2 to 3 × 10 ⁻⁴ Pa. First, HAT-CN was deposited on ITO to a thickness of 5 nm to form a hole injection layer. Next, α-NPD was vapor-deposited to a thickness of 20 nm, and TCTA was vapor-deposited to a thickness of 20 nm to form a hole transport layer. Subsequently, mCP was deposited to a thickness of 10 nm to form an exciton blocking layer. Next, Compound 1 and DPEPO were co-evaporated from different vapor deposition sources to form a 20 nm thick layer as a light emitting layer. At this time, the concentration of Compound 1 was 6.0% by mass. Next, DPEPO was vapor-deposited to a thickness of 10 nm to form an exciton blocking layer, and TPBi was vapor-deposited to a thickness of 30 nm to form an electron transport layer. Subsequently, lithium fluoride (LiF) was vapor-deposited to a thickness of 0.8 nm to form an electron injection layer, and aluminum (Al) was vapor-deposited to a thickness of 120 nm thereon to form a cathode. Through the above steps, [ITO / HAT-CN (5 nm) / α-NPD (20 nm) / TCTA (20 nm) / mCP (10 nm) / DPEPO and 6% by mass of Compound 1 (20 nm) / DPEPO (10 nm) / TPBi (30 nm) / LiF (0.8 nm) / Al (120 nm)], an organic electroluminescence element (element 1) having a multilayer structure was obtained. In addition, “/” in the above square brackets represents a layer boundary, and is written on the right side of [/] on the layer made of the film thickness (nm) and material described on the left side of “/”. It means that layers of film thickness (nm) and material are laminated.

(Example 4) Production of organic electroluminescence device using compound 2 An organic electroluminescence device (device 2) was produced in the same manner as in Example 3 except that compound 2 was used instead of compound 1.

(Comparative Examples 3 and 4) Preparation of Organic Electroluminescent Device Using Comparative Compounds 1 and 2 An organic electroluminescent device (Comparative Device 1) was prepared in the same manner as in Example 3 except that Comparative Compound 1 was used instead of Compound 1. The organic electroluminescence element (comparative element 2) was produced in the same manner as in Example 3 except that the comparative compound 2 was used instead of the compound 1.

[Evaluation of device characteristics]
The emission spectrum of the organic electroluminescent element produced in each Example and each comparative example is shown in FIG. 4, and external quantum efficiency (EQE) -current density characteristics are shown in FIG. Table 2 shows the maximum external quantum efficiency of each organic electroluminescence element.

As shown in FIG. 5 and Table 2, both of the device 1 using the compound 1 and the device 2 using the compound 2 had high external quantum efficiency. The CIE color coordinates of the emission colors of the element 1 and the element 2 were (0.148, 0.098) and (0.150, 0.097), respectively, and were deep blue. On the other hand, the comparative element 1 has a maximum external quantum efficiency of 7.2%, which is lower in luminous efficiency than the elements 1 and 2. On the other hand, from FIG. 4, the comparative element 2 has a large emission maximum wavelength with respect to the elements 1 and 2 and is shifted to the long wavelength side, and blue light emission cannot be obtained.

  The compound of the present invention is useful as a light emitting material. For this reason, the compound of this invention is effectively used as a luminescent material for organic light emitting elements, such as an organic electroluminescent element. Since the compounds of the present invention include those that emit delayed fluorescence, it is also possible to provide an organic light-emitting device with high luminous efficiency. For this reason, this invention has high industrial applicability.

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

Claims (14)

A luminescent material comprising a compound represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ] The luminescent material according to claim 1, wherein at least one of R ³ and R ^{6 in} the general formula (1) is a substituted or unsubstituted alkyl group. The luminescent material according to claim 1 or 2, wherein one of R ^{2 to} R ⁴ and one of R ^{5 to} R ^{7 in} the general formula (1) is a substituted or unsubstituted alkyl group. The luminescent material according to claim 1, wherein at least one of R ¹ and R ^{8 in} the general formula (1) is a hydrogen atom. The luminescent material according to claim 1, wherein at least one of R ¹² , R ¹⁴ , and R ^{15 in} the general formula (1) is a substituted or unsubstituted alkyl group. The luminescent material according to claim 5, wherein R ^{15 in the} general formula (1) is a substituted or unsubstituted alkyl group.   The luminescent material according to any one of claims 1 to 6, wherein the alkyl group is an unsubstituted alkyl group.   The luminescent material according to claim 1, wherein the alkyl group in the substituted or unsubstituted alkyl group has 1 to 3 carbon atoms. A compound represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ] A delayed phosphor having a structure represented by the following general formula (1).

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ] The organic light emitting element which has a light emitting layer containing the compound represented by following General formula (1) on a board | substrate.

[In General Formula (1), R ^{1 to} R ⁸ , R ¹² and R ^{14 to} R ²⁵ each independently represent a hydrogen atom or a substituent, and R ¹¹ represents a substituted or unsubstituted alkyl group. However, at least one of R ^{2 to} R ⁴ is a substituted or unsubstituted alkyl group, and at least one of R ^{5 to} R ⁷ is a substituted or unsubstituted alkyl group. ]   The organic light-emitting device according to claim 11, which emits delayed fluorescence.   The organic light emitting device according to claim 11, wherein the light emitting layer contains a host material.   The organic light emitting device according to any one of claims 11 to 13, wherein the content of the compound represented by the general formula (1) in the light emitting layer is less than 50% by weight.

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