JP6647514B2 - Organic light emitting device and light emitting material and compound used therefor - Google Patents

Description

  The present invention relates to an organic light emitting device having high luminous efficiency and high weather resistance. The present invention also relates to a light emitting material and a compound used for the organic light emitting device.

  Research for increasing the luminous efficiency of organic light-emitting devices such as organic electroluminescence devices (organic EL devices) has been actively conducted. In particular, various measures have been taken to increase the luminous efficiency by newly developing and combining an electron transporting material, a hole transporting material, a light emitting material, and the like that constitute the organic electroluminescence element. Among them, researches on organic electroluminescence devices using cyanobenzene derivatives having a carbazole structure are also found.

For example, Patent Literature 1 describes that a cyanobenzene derivative represented by the following general formula (3) is used as a light emitting material of an organic light emitting device. Here, in the general formula (3), one of R ^{81 to} R ⁸⁵ is a cyano group, two of R ^{81 to} R ⁸⁵ are a substituted or unsubstituted 9-carbazolyl group, and the other two are It is prescribed to represent a hydrogen atom. In addition, in the same document, the 9-carbazolyl group in the general formula (3) and the substituents (1,2,3,4-tetrahydro-9-carbazolyl group, 1-indolyl group, diaryl As an example of a substituent that can be substituted on the amino group), a cyano group is mentioned.

JP 2014-135466 A

As described above, Patent Document 1 proposes that a cyanobenzene derivative having a carbazolyl group be applied to a light emitting material of an organic electroluminescence device. As an example of a substituent that can be substituted for the carbazolyl group or the like, cyanobenzene is proposed. Groups are listed. However, the document does not describe the fact that a cyano group was actually introduced into the carbazolyl group of the cyanobenzene derivative to produce a compound, or the result of evaluating its usefulness.
For example, as described in paragraphs [0021] and [0035] of JP-A-7-26265, it is well known that light resistance generally decreases when a cyano group is introduced into a compound molecule. Therefore, when a cyano group is introduced into a molecule, it is usual to design the molecule while minimizing the number of the cyano group. In particular, the introduction of a cyano group into an organic electroluminescent device material which is expected to be used outdoors has to be reluctant. Therefore, in the compound of Patent Document 1 in which it is essential that one cyano group already exists in the molecule, it is generally attempted to avoid introducing a second or more cyano group into the molecule. It is a target.

On the other hand, the present inventors have studied and found that the compound described in Patent Document 1 is more useful if the HOMO level and the LUMO level can be further reduced. Oxidation is difficult if the HOMO level and the LUMO level are lowered. In particular, when the LUMO level of the light-emitting material is lowered, deterioration of radical species and excitons generated in the light-emitting process due to reaction with water and oxygen is suppressed. It is expected to be. In addition, when the HOMO level is lowered together with the LUMO level, a longer wavelength of light emission due to a narrower HOMO-LUMO gap is suppressed, and oxidation resistance is imparted in consideration of a shorter wavelength of light emission. It will be advantageous. Therefore, by lowering both the HOMO level and the LUMO level, it is expected that a more useful light-emitting material will be realized. However, Patent Document 1 does not describe a measure for further lowering the HOMO level and the LUMO level.
The present inventors have studied the cyanobenzene derivative having a carbazolyl group in view of these prior art problems with the aim of maintaining light fastness while lowering the HOMO level and the LUMO level. Further, the present inventors have conducted intensive studies for the purpose of deriving a general formula of a compound having such characteristics and being useful as a light emitting material, and further generalizing a configuration of an organic light emitting device having high luminous efficiency and high weather resistance.

［一般式（１）において、Ｒ¹〜Ｒ⁵の少なくとも１つはシアノ基を表し、Ｒ¹〜Ｒ⁵の少なくとも１つは２位及び７位の少なくとも一方がシアノ基で置換されたカルバゾリル基（ただし、２位がシアノ基で置換されている場合は３位が無置換であるかシアノ基以外の置換基で置換されており、また、７位がシアノ基で置換されている場合は６位が無置換であるかシアノ基以外の置換基で置換されている）を表し、残りのＲ¹〜Ｒ⁵は水素原子または置換基を表す。］
［２］ 前記２位及び７位の少なくとも一方がシアノ基で置換されたカルバゾリル基は、２位及び７位の両方がシアノ基で置換されていることを特徴とする［１］に記載の発光材料。
［３］ 前記一般式(１)のＲ¹がシアノ基であることを特徴とする［１］または［２］に記載の発光材料。
［４］ 前記一般式（１）のＲ²とＲ³またはＲ³とＲ⁴が、前記２位及び７位の少なくとも一方がシアノ基で置換されたカルバゾリル基であることを特徴とする［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Ｒ²がシアノ基であり、Ｒ¹、Ｒ³〜Ｒ⁵が前記２位及び７位の少なくとも一方がシアノ基で置換されたカルバゾリル基であることを特徴とする［１］に記載の発光材料。
［６］ 前記２位及び７位の少なくとも一方がシアノ基で置換されたカルバゾリル基が、下記一般式（１１）で表される構造を有することを特徴とする［１］に記載の発光材料。

［一般式（１１）において、Ｒ²¹、Ｒ²³〜Ｒ²⁸は、各々独立に水素原子または置換基を表し、Ｒ²²はシアノ基を表す。］
［７］ 前記一般式（１１）のＲ²⁷がシアノ基であることを特徴とする［６］に記載の発光材料。
［８］ 前記一般式（１１）のＲ²¹、Ｒ²³〜Ｒ²⁶、Ｒ²⁸の少なくとも１つが置換もしくは無置換のカルバゾリル基であることを特徴とする［６］または［７］に記載の発光材料。
［９］ 前記一般式（１１）のＲ²³が置換もしくは無置換のカルバゾリル基であることを特徴とする［８］に記載の発光材料。
［１０］ 前記一般式（１１）のＲ²³及びＲ²⁶が置換もしくは無置換のカルバゾリル基であることを特徴とする［８］に記載の発光材料。
［１１］ 前記カルバゾリル基がシアノ基で置換されていることを特徴とする［８］〜［１０］のいずれか１項に記載の発光材料。
［１２］ 一般式（１）で表される化合物の分子内に存在するカルバゾール環の数が４つ以下であることを特徴とする［１］〜［１１］のいずれか１項に記載の発光材料。 As a result of intensive studies to achieve the above object, the present inventors have found that in a cyanobenzene derivative having a carbazolyl group, when at least one of the 2- and 7-positions of the carbazolyl group is substituted with a cyano group, a carbazolyl group is obtained. It has been found that both the HOMO level and the LUMO level decrease while maintaining the same light resistance as a cyanobenzene derivative in which the group is not substituted with a cyano group. And, it has been clarified that such a cyanobenzene derivative having a carbazolyl group in which a specific position is substituted with a cyano group is extremely useful as a light emitting material for an organic electroluminescence device. Furthermore, they found that among these cyanobenzene derivatives, there was a compound useful as a delayed fluorescent material, and clarified that an organic light-emitting device having high luminous efficiency and high weather resistance could be provided at low cost. Based on these findings, the present inventors have provided the following present invention as means for solving the above-mentioned problems.
[1] A luminescent material containing a compound represented by the following general formula (1).

[In the general formula (1), at least one of a cyano group, at least one carbazolyl group in which at least one of the 2- and 7-position is substituted with a cyano group R ¹ to R ⁵ of R ¹ to R ⁵ (However, when the 2-position is substituted with a cyano group, the 3-position is unsubstituted or substituted with a substituent other than a cyano group, and when the 7-position is substituted with a cyano group, 6-position is substituted. Position is unsubstituted or substituted with a substituent other than a cyano group), and the remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]
[2] The luminescence according to [1], wherein the carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group has both the 2-position and the 7-position substituted with a cyano group. material.
[3] The luminescent material according to [1] or [2], wherein R ^{1 in the} general formula (1) is a cyano group.
[4] In the general formula (1), R ² and R ³ or R ³ and R ⁴ are a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group. ] The luminescent material according to any one of [3] to [3].
[5] R ^{2 in the} general formula (1) is a cyano group, and R ¹ and R ^{3 to} R ⁵ are carbazolyl groups in which at least one of the 2-position and the 7-position is substituted with a cyano group. The luminescent material according to [1].
[6] The luminescent material according to [1], wherein the carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group has a structure represented by the following general formula (11).

[In the general formula (11), R ²¹ , R ^{23 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and R ²² represents a cyano group. ]
[7] The luminescent material according to [6], wherein R ^{27 in the} general formula (11) is a cyano group.
[8] The emission according to [6] or [7], wherein at least one of R ²¹ , R ^{23 to} R ²⁶ , and R ^{28 in} the general formula (11) is a substituted or unsubstituted carbazolyl group. material.
[9] The luminescent material according to [8], wherein R ^{23 in the} general formula (11) is a substituted or unsubstituted carbazolyl group.
[10] The light emitting material according to [8], wherein R ²³ and R ^{26 in} the general formula (11) are a substituted or unsubstituted carbazolyl group.
[11] The light emitting material according to any one of [8] to [10], wherein the carbazolyl group is substituted with a cyano group.
[12] The luminescence according to any one of [1] to [11], wherein the number of carbazole rings present in the molecule of the compound represented by the general formula (1) is four or less. material.

[13] A compound represented by the general formula (1).
[14] An organic light emitting device having a light emitting layer containing the light emitting material according to any one of [1] to [12] on a substrate.
[15] The organic light-emitting device according to [14], which emits delayed fluorescence.
[16] The organic light-emitting device according to [14] or [15], which is an organic electroluminescence device.
[17] A delayed phosphor having a structure represented by the general formula (1).

  The compound of the present invention has good light-emitting properties, a deep HOMO level and a deep LUMO level, and high light resistance and high heat resistance. Therefore, the compound of the present invention is extremely useful as a light emitting material, and by using it as a light emitting material of an organic light emitting device, an organic light emitting device having excellent light emitting characteristics and weather resistance can be realized. Further, since the compound of the present invention can emit delayed fluorescence, it can be used as a delayed fluorescent substance. By using a delayed fluorescent substance comprising the compound of the present invention in an organic light emitting device, it is possible to realize an organic light emitting device having excellent light emitting characteristics and weather resistance and extremely high luminous efficiency.

FIG. 3 is a schematic cross-sectional view illustrating a layer configuration example of an organic electroluminescence element. 1 is a ¹ H NMR spectrum of a DMSO-d6 solution of Compound 1. 4 is a graph showing the change over time in the emission intensity of Compound 1, Comparative Compound 1 and Comparative Compound 2 when continuously irradiated with 350 nm excitation light under a nitrogen atmosphere. 4 is a graph showing the change over time in the emission intensity of Compound 1, Comparative Compound 1 and Comparative Compound 2 when continuously irradiated with 350 nm excitation light in the atmosphere. 4 is an emission spectrum of a toluene solution of Compound 1. 4 is a transient decay curve of a toluene solution of Compound 1. 3 is an emission spectrum of a thin film of Compound 1. 4 is a transient decay curve of a thin film of Compound 1. 3 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device using Compound 1. 4 is a graph showing voltage-luminance-external quantum efficiency characteristics of an organic electroluminescence device using Compound 1.

  Hereinafter, the contents of the present invention will be described in detail. The description of the components 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 this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.

[Compound represented by Formula (1)]
The luminescent material of the present invention is characterized by containing a compound represented by the following general formula (1). Further, the organic light emitting device of the present invention is characterized in that a compound represented by the following general formula (1) is contained as a light emitting material of a light emitting layer. Therefore, the compound represented by the general formula (1) will be described first.

In the general formula (1), at least one of R ^{1 to} R ⁵ represents a cyano group. When any one is a cyano group, it may be any of R ^{1 to} R ³ . When any two are a cyano group, a combination of R ¹ and R ^{3 or} a combination of R ² and R ⁴ can be exemplified. When any three are cyano groups, examples of combinations of R ¹ , R ^3, and R ⁴ can be given. Among these, a case where R ¹ or R ² is a cyano group is preferable, and a case where R ¹ is a cyano group is more preferable.

In the general formula (1), at least one of R ^{1 to} R ⁵ is a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group (however, when the 2-position is substituted with a cyano group, 3 Position is unsubstituted or substituted with a substituent other than a cyano group, and when the 7-position is substituted with a cyano group, the 6-position is unsubstituted or substituted with a substituent other than a cyano group. Represents). When two or more of R ^{1 to} R ⁵ represent a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, they may be the same or different, but must be the same. Is more preferred.

The carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group is bonded to the benzene ring in the general formula (1) at its nitrogen atom or carbon atom. The binding site to the benzene ring in the carbazolyl group may be any of the 1 to 9 positions except for at least one of the 2 and 7 positions substituted with a cyano group, Preferably, there is.
In the carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, only one of the 2- and 7-positions may be substituted with a cyano group, or both the 2- and 7-positions may be substituted. May be substituted with a cyano group, but it is preferred that both the 2-position and the 7-position are substituted with a cyano group.
Of the carbazolyl group's 1 to 9 positions, the above-mentioned binding site to the benzene ring and the remaining site except at least one of the 2- and 7-positions substituted with a cyano group are substituted even if they are unsubstituted. May be substituted. Regarding the preferred range and specific examples of the substituent, preferred ranges and specific examples of the substituent which R ²¹ and R ^{23 to} R ²⁸ in the following general formula (11) can take, and R ²¹ and R in the following general formula (11) ²³ to R ^26, at least one carbazolyl group representing the R ^28, reference can be made to the descriptions of substituted carbazolyl group with a cyano group.

  The carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group preferably has, for example, a structure represented by the following general formula (11).

In the general formula (11), R ²¹ and R ^{23 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and R ²² represents a cyano group.
When R ²¹ and R ^{23 to} R ²⁸ have a substituent, any may be a substituent and the number of substituents is not particularly limited. For example, the number of substituents in R ²¹ , R ^{23 to} R ²⁸ is preferably 0 to 5, more preferably 0 to 3, for example, 0 to 1 is also preferable. When two or more of R ²¹ and R ^{23 to} R ²⁸ are substituents, the two or more substituents may be the same or different, but are preferably the same. When R ²¹ and R ^{23 to} R ²⁸ have a substituent, at least one of R ^{23 to} R ²⁷ is preferably a substituent. For example, preferably, R ²⁷ is a substituent, R ²³ and R ²⁶ are substituents, and R ²⁴ and R ²⁵ are substituents.

Examples of the substituent that R ²¹ and R ^{23 to} R ^{28 in the} general formula (11) can have include, for example, a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and a carbon atom. An alkylthio group having 1 to 20 carbon atoms, an alkyl-substituted amino group having 1 to 20 carbon atoms, an acyl group having 2 to 20 carbon atoms, an aryl group having 6 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, and 12 carbon atoms -40 diarylamino group, a substituted or unsubstituted carbazolyl group having 12 to 40 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, carbon An alkylsulfonyl group having 1 to 10 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an amide group, an alkylamide group having 2 to 10 carbon atoms, a trialkylsilyl group having 3 to 20 carbon atoms, 4-20 trialkylsilyl group, the trialkylsilyl alkenyl group having 5 to 20 carbon atoms and an trialkylsilyl alkynyl group and a nitro group having 5 to 20 carbon atoms. Among these specific examples, those that can be further substituted by a substituent may be substituted. More preferred substituents include a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, A substituted or unsubstituted heteroaryl group having 3 to 40 carbon atoms; a substituted or unsubstituted diarylamino group having 12 to 40 carbon atoms; and a substituted or unsubstituted carbazolyl group having 12 to 40 carbon atoms. More preferred substituents are a fluorine atom, a chlorine atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms. Or an unsubstituted dialkylamino group, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, or a substituted or unsubstituted heteroaryl group having 3 to 12 carbon atoms.
Among them, R ²³ and R ²⁶ in the general formula (11) are preferably a substituent, more preferably an alkyl group having 1 to 20 carbon atoms, and an aryl group having 6 to 40 carbon atoms, and more preferably 1 to 2 carbon atoms. More preferably, it is an alkyl group having 10 or an aryl group having 6 to 15 carbon atoms. If R ²³ and R ²⁶ are substituents, they are less susceptible to oxidation and can suppress dimerization, which is preferable in terms of stability.

  The alkyl group referred to in the present specification may be linear, branched, or cyclic, and more preferably has 1 to 6 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, and a butyl group. Group, t-butyl group, pentyl group, hexyl group and isopropyl group. The aryl group may be a single ring or a fused ring, and specific examples include a phenyl group and a naphthyl group. The alkoxy group may be linear, branched, or cyclic, and more preferably has 1 to 6 carbon atoms. Specific examples include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a t-butoxy group. Groups, a pentyloxy group, a hexyloxy group, and an isopropoxy group. The two alkyl groups of the dialkylamino group may be the same or different from each other, but are preferably the same. The two alkyl groups of the dialkylamino group may be each independently linear, branched, or cyclic, more preferably 1 to 6 carbon atoms, and specific examples include a methyl group, an ethyl group, Examples thereof include a propyl group, a butyl group, a pentyl group, a hexyl group, and an isopropyl group. The aryl group may be a single ring or a fused ring, and specific examples include a phenyl group and a naphthyl group. The heteroaryl group may be a single ring or a fused ring, and specific examples include a pyridyl group, a pyridazyl group, a pyrimidyl group, a triazyl group, a triazolyl group, a benzotriazolyl group, and a carbazolyl group. These heteroaryl groups may be groups bonded via a hetero atom or groups bonded via carbon atoms constituting a heteroaryl ring.

Among them, R ²⁷ in the general formula (11) is preferably a cyano group. That is, in the carbazolyl group represented by the general formula (11), it is preferable that both R ²² and R ²⁷ are cyano groups.

Also, R ^21, it is preferable that at least one of R ²³ ~R ^26, R ²⁸ is a carbazolyl group, 2-carbazolyl group, 3-carbazolyl group, more preferably a 9-carbazolyl group. When at least one of R ²¹ , R ^{23 to} R ²⁶ , and R ²⁸ is a carbazolyl group, the HOMO level and the LUMO level of the compound represented by the general formula (1) can be further reduced. When at least one of ^{R 21, R 23 ~R 26,} R 28 is a carbazolyl group, the carbazolyl group may be unsubstituted or may be substituted with a substituent, but is substituted by a cyano group Is preferred. When the carbazolyl group represented by R ²¹ , R ^{23 to} R ²⁶ or R ²⁸ is substituted with a cyano group, the substitution position of the cyano group may be at least one of the 6-position and the 8-position in the 2-carbazolyl group. The 3-carbazolyl group is preferably at the 7-position, and the 9-carbazolyl group is preferably at least one of the 2- and 7-positions. Among them, the carbazolyl group represented by at least one of R ²¹ , R ^{23 to} R ²⁶ , and R ²⁸ is more preferably a 2-carbazolyl group in which at least one of the 6-position and the 8-position is substituted with a cyano group. . The carbazolyl group represented by R ²¹ , R ^{23 to} R ²⁶ , and R ²⁸ is preferably substituted when the 3-, 6-, and 9-positions are substitutable. It is more preferably an alkyl group or an aryl group having 6 to 40 carbon atoms, and further preferably an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 15 carbon atoms. Substitution at the 3-, 6-, and 9-positions is preferable in terms of stability because oxidation is less likely to occur and dimerization can be suppressed. Moreover, what is carbazolyl group among ^{R 21, R 23 ~R 26,} R 28 is more preferably is preferably at least one of R ²³ to R ^26, a R ²³ and R ^26. However, from the viewpoint of practicality, the number of carbazole rings present in the molecule of the compound represented by the general formula (1) is preferably four or less.

As described above, in the general formula (1), at least one of R ^{1 to} R ⁵ is a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group. When any one of R ^{1 to} R ⁵ is a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, it may be any of R ^{1 to} R ³ . When any two are a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, a combination of R ¹ and R ^2, a combination of R ² and R ^3, a combination of R ³ and R ⁴ , R ¹ and R ³ , R ² and R ⁴ , and the like, and preferably a combination of R ² and R ³ or a combination of R ³ and R ⁴ . When any three are a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, a combination of R ¹ , R ³ and R ⁴ can be exemplified. When any four are a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, a combination of R ¹ , R ³ , R ⁴ and R ⁵ can be exemplified.

  The para-position of the benzene ring to which the carbazolyl group in which at least one of the 2-position and the 7-position is substituted by a cyano group is preferably a cyano group. Further, when two or more carbazolyl groups in which at least one of the 2-position and the 7-position is substituted with a cyano group are bonded to a benzene ring, at least two of them are bonded to the benzene ring to which each is bonded. Preferably, the condition that the para position is a cyano group is satisfied.

In the general formula (1), at least one of a cyano group, a carbazolyl group in which at least one of the at least one the 2-position and 7-position of the R ¹ to R ⁵ is a cyano group R ¹ to R ⁵ Wherein R ^{1 to} R ⁵ represent a hydrogen atom or a substituent.

Preferred substituents that R ^{1 to} R ⁵ may have 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, an alkylthio group having 1 to 20 carbon atoms, -20 alkyl-substituted amino group, C2-C20 acyl group, C6-C40 aryl group, C3-C40 heteroaryl group, C2-C10 alkenyl group, C2-C10 An alkynyl group, an alkoxycarbonyl group having 2 to 10 carbon atoms, an alkylsulfonyl group having 1 to 10 carbon atoms, an amide group, an alkylamide group having 2 to 10 carbon atoms, a trialkylsilyl group having 3 to 20 carbon atoms, and a carbon number 4-20 trialkylsilylalkyl groups, 5-20 carbon atoms trialkylsilylalkenyl groups, 5-20 carbon atoms trialkylsilylalkynyl groups and nitro groups And the like. Among these specific examples, those that can be further substituted by a substituent may be substituted. More preferred substituents are a hydroxy group, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, and a substituted or unsubstituted 1 to 20 carbon atoms. A substituted or unsubstituted aryl group having 6 to 40 carbon atoms, and a substituted or unsubstituted heteroaryl group having 3 to 40 carbon atoms. More preferred substituents are a hydroxy group, a fluorine atom, a chlorine atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms. Or an unsubstituted dialkylamino group, a substituted or unsubstituted aryl group having 6 to 15 carbon atoms, or a substituted or unsubstituted heteroaryl group having 3 to 12 carbon atoms. Still more preferably, they are a hydroxy group, a fluorine atom and a chlorine atom.

Examples of preferable substituents that R ^{1 to} R ⁵ can take also include groups represented by the following general formulas (12) to (15).

In the general formula (12), R ^{31 to} R ³⁸ each independently represent a hydrogen atom or a substituent. In the general formulas (13) to (15), R ^{41 to} R ⁴⁶ , R ^{51 to} R ⁶² and R ^{71 to} R ⁸⁰ each independently represent a hydrogen atom or a substituent. When the groups represented by formulas (12) to (15) have a substituent, the substitution position and the number of substitution are not particularly limited. The number of substitution of each group is preferably from 0 to 6, more preferably from 0 to 4, and for example, preferably from 0 to 2. When it has a plurality of substituents, they may be the same or different, but are preferably the same.
When the group represented by the general formula (12) has a substituent, it is preferably one of R ³² to R ³⁷ is a substituent. For example, when ^R32 and ^R37 are substituents, when ^R33 and ^R36 are substituents, and when ^R34 and ^R35 are substituents, preferred examples can be preferably given.
When the group represented by the general formula (13) has a substituent, any one of R ^{42 to} R ⁴⁶ is preferably a substituent. For example, the case where R ⁴² is a substituent and the case where R ⁴³ is a substituent can be preferably exemplified.
When the group represented by the general formula (14) has a substituent, any of R ^{52 to} R ⁶⁰ is preferably a substituent. For example, when any of R ^{52 to} R ⁵⁴ is a substituent, the case where any of R ^{55 to} R ⁶⁰ is a substituent can be preferably exemplified.
When the group represented by the general formula (15) has a substituent, it is preferable that any one of R ^{72 to} R ⁷⁴ and R ^{77 to} R ⁷⁹ is a substituent. For example, when R ⁷² and R ⁷⁹ are substituents, when R ⁷³ and R ⁷⁸ are substituents, when R ⁷⁴ and R ⁷⁷ are substituents, R ⁷² , R ⁷⁴ , R ⁷⁷ and R ⁷⁹ are The case where it is a substituent can be preferably exemplified. In particular, when R ⁷⁴ and R ⁷⁷ are substituents, the case where R ⁷² , R ⁷⁴ , R ⁷⁷ and R ⁷⁹ are substituents can be more preferably exemplified. The substituents at this time are particularly preferably each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 40 carbon atoms. And further preferably an unsubstituted alkyl group, an unsubstituted aryl group having 6 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms substituted with an aryl group having 6 to 10 carbon atoms.

R ^{31 to} R ^{38 of} the general formula (12), R ^{41 to} R ^{46 of} the general formula (13), R ^{51 to} R ⁶² of the general formula (14), and R ^{71 to} R ⁸⁰ of the general formula (15) For preferred ranges and specific examples of the possible substituents, reference can be made to the preferred ranges and specific examples of the substituents that can be taken by R ²¹ and R ^{23 to} R ²⁸ in the general formula (11).

In the general formula (1), the number of hydrogen atoms out of R ^{1 to} R ⁵ is preferably 3 or less, more preferably 2 or less, and even more preferably 0.

As a preferable combination, for example, when R ^{1 in the} general formula (1) is a cyano group, and at least one of R ³ and R ⁴ is a carbazolyl group in which at least one of the 2- and 7-positions is substituted with a cyano group. Can be mentioned. Another preferred combination is that R ² is a cyano group and at least one of R ¹ , R ^{3 to} R ⁵ is a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group. Can also. As a more preferable combination, for example, when R ^{1 in the} general formula (1) is a cyano group, and both R ⁴ and R ⁵ are a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group. Can be mentioned. Another more preferred combination includes the case where R ² is a cyano group and all of R ¹ , R ^{3 to} R ⁵ are carbazolyl groups in which at least one of the 2-position and the 7-position is substituted with a cyano group. Can also.

  The compound represented by the general formula (1) includes a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group, the substitution position and the number of substitution on the benzene ring, and the binding of the carbazolyl group to the benzene ring. The symmetry and linearity of the molecular structure can be controlled by selecting the site, the substitution position and the number of the carbazolyl group to be introduced into the carbazolyl group, the binding site of the carbazolyl group to the carbazolyl group, and the like. For example, if the symmetry of the molecule is high, there is an advantage that the electron transition property is high. On the other hand, it is preferable that the molecule is linear because polarization increases and the quantum yield increases, but electron transition properties decrease. The introduction of a cyano group acts in a direction to increase the polarization of a molecule.

  Hereinafter, specific examples of the compound represented by the general formula (1) will be exemplified, but the compound represented by the general formula (1) that can be used in the present invention is limitedly interpreted by these specific examples. It should not be.

The molecular weight of the compound represented by the general formula (1) is, for example, 1500 or less when an organic layer containing the compound represented by the general formula (1) is intended to be formed by a vapor deposition method and used. Preferably, it is not more than 1200, more preferably not more than 1,000, and even more preferably not more than 800. The lower limit of the molecular weight is usually 247 or more, preferably 290 or more.
The compound represented by the general formula (1) may be formed into a film by a coating method regardless of the molecular weight. By using a coating method, it is possible to form a film even with a compound having a relatively large molecular weight.

By applying the present invention, it is conceivable to use a compound containing a plurality of structures represented by the general formula (1) in a molecule in a light emitting layer of an organic light emitting device.
For example, a polymer obtained by polymerizing a polymerizable monomer having a structure represented by the general formula (1) may be used for the light emitting layer of the organic light emitting device. Specifically, by preparing a monomer having a polymerizable functional group at any of R ^{1 to} R ^{5 in} the general formula (1), and polymerizing it alone or copolymerizing it with another monomer, It is conceivable to obtain a polymer having a repeating unit and use the polymer for a light emitting layer of an organic light emitting device. Alternatively, a dimer or a trimer may be obtained by coupling compounds having a structure represented by the general formula (1), and these may be used for a light emitting layer of an organic light emitting device.

As an example of the structure of the repeating unit constituting the polymer having the structure represented by the general formula (1), any of R ^{1 to} R ^{5 in} the general formula (1) is represented by the following general formula (17) or (18) What is represented structure can be mentioned.

In the general formulas (17) and (18), L ¹ and L ² represent a linking group. The number of carbon atoms in the linking group is preferably from 0 to 20, more preferably from 1 to 15, and even more preferably from 2 to 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, preferably a substituted or unsubstituted alkylene group, or a substituted or unsubstituted arylene group, and a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, or a substituted or unsubstituted alkylene group. More preferably, it is a phenylene group.
In the general formulas (17) and (18), 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. And an unsubstituted alkoxy group having 1 to 3 carbon atoms, a fluorine atom and a chlorine atom, more preferably an unsubstituted alkyl group having 1 to 3 carbon atoms and an unsubstituted alkoxy group having 1 to 3 carbon atoms.

Specific examples of the structure of the repeating unit include those in which any one of R ^{1 to} R ^{5 in} the general formula (1) is represented by the following formulas (21) to (24). Two or more of R ^{1 to} R ⁵ may be the following formulas (21) to (24), but ^one of R ^{1 to} R ⁵ is preferably one of the following formulas (21) to (24). ).

The polymer having a repeating unit containing these formulas (21) to (24) is prepared by reacting at least one of R ^{1 to} R ^{5 in} the general formula (1) with a hydroxy group, and reacting the compound with the hydroxy group as a linker. Then, a polymerizable group is introduced, and the compound can be synthesized by polymerizing the polymerizable group.

  The polymer having a structure represented by the general formula (1) in the molecule may be a polymer composed of only a repeating unit having the structure represented by the general formula (1), or a polymer having another structure. It may be a polymer containing a repeating unit having the same. Further, the repeating unit having the structure represented by the general formula (1) contained in the polymer may be a single type or a combination of two or more types. Examples of the repeating unit having no structure represented by the general formula (1) include those derived from a monomer used for ordinary copolymerization. For example, a repeating unit derived from a monomer having an ethylenically unsaturated bond such as ethylene and styrene can be mentioned.

[Synthesis method of compound represented by general formula (1)]
The compound represented by the general formula (1) is a novel compound.
The method for synthesizing the compound represented by the general formula (1) is not particularly limited. The compound represented by the general formula (1) can be synthesized by appropriately combining known synthesis methods and conditions.
For example, as a preferred synthesis method, there is a method in which difluorodicyanobenzene is prepared and reacted with carbazole in which at least one of the 2-position and the 7-position is substituted with a cyano group. Thus, a compound in which one of R ^{1 to} R ^{5 in} the general formula (1) is a cyano group and the remaining two are carbazolyl groups in which at least one of the 2-position and the 7-position is substituted with a cyano group. can do. The compound thus synthesized can be easily purified by washing with a solvent. When tetrafluorodicyanobenzene is used as a starting material, any ^one of R ^{1 to} R ^{5 in} the general formula (1) is a cyano group, and the rest is carbazolyl in which at least one of the 2-position and the 7-position is substituted with a cyano group. Compounds that are groups can be synthesized. Further, by changing the number of cyano groups and fluoro groups in cyanobenzene in accordance with the number of cyano groups and carbazolyl groups in which at least one of the 2- and 7-positions in the benzene ring of the target compound is substituted with a cyano group. The desired compound represented by the general formula (1) can be synthesized. Further, a hydroxy group can be introduced into the benzene ring by performing a step of adding water and irradiating ultrasonic waves. The above-described synthesis method is suitable for large-scale production at an industrial level because a high yield can be obtained with relatively simple steps.
For details of the above reaction, the following Synthesis Examples can be referred to. 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 has good light emitting properties and is useful as a light emitting material of an organic light emitting device. In addition, the compound represented by the general formula (1) has high thermal stability and a high HOMO level due to the carbazolyl group substituted on the benzene ring substituted with the cyano group being substituted with the cyano group. It is considered that both the energy level and the LUMO level are deep, and the deterioration of radical species and excitons generated during the light emission process due to the reaction with moisture and oxygen is suppressed. Further, the compound represented by the general formula (1) includes a cyanobenzene in which the carbazolyl group is not substituted with a cyano group because the substitution position of the cyano group in the carbazolyl group is at least one of the 2-position and the 7-position. It has the same high light resistance as derivatives. Therefore, an organic light-emitting element using the compound represented by the general formula (1) of the present invention as a light-emitting material of a light-emitting layer has extremely high weather resistance (heat resistance, oxidation resistance, and light resistance) and can be used outdoors. Even when used, the light emission characteristics can be maintained.
Furthermore, the compound represented by the general formula (1) includes a delayed fluorescent material (delayed fluorescent material) that emits delayed fluorescent light. That is, the present invention relates to the invention of a delayed fluorescent substance having a structure represented by the general formula (1), the invention using a compound represented by the general formula (1) as a delayed fluorescent substance, There is also provided an invention of a method for emitting delayed fluorescence using the compound represented. An organic light-emitting element using such a compound as a light-emitting material has characteristics of emitting delayed fluorescence and having 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 luminescent material from both positive and negative electrodes to generate a luminescent material in an excited state and emit light. Normally, in the case of a carrier injection type organic electroluminescence device, 25% of the generated excitons are excited to an excited singlet state, and the remaining 75% are excited to an excited triplet state. Therefore, energy utilization efficiency is higher when phosphorescent light emitted from the excited triplet state is used. However, since the excited triplet state has a long lifetime, saturation of the excited state or deactivation of energy due to interaction with an exciton in the excited triplet state occurs, and the quantum yield of phosphorescence is generally not high in many cases. On the other hand, in the delayed fluorescent material, after the energy transitions to the excited triplet state due to intersystem crossing, etc., the triplet-triplet annihilation or the inverse intersystem crossing to the excited singlet state due to absorption of heat energy causes emission of fluorescence. I do. In an organic electroluminescence device, a thermally activated delayed fluorescent material due to absorption of thermal energy is considered to be particularly useful. When a delayed fluorescent material is used in an organic electroluminescence device, an exciton in an excited singlet state emits fluorescence as usual. On the other hand, the exciton in the excited triplet state absorbs heat generated by the device, intersects with the excited singlet, and emits fluorescence. At this time, although the light is emitted from the excited singlet, the light is emitted at the same wavelength as the fluorescence, but the lifetime (emission lifetime) of the light generated by the inverse intersystem crossing from the excited triplet state to the excited singlet state is usually Is longer than the fluorescence or phosphorescence of the above, and is observed as fluorescence delayed from these. This can be defined as delayed fluorescence. By using such a thermally activated exciton transfer mechanism, the ratio of the compound in the excited singlet state, which normally produces only 25%, is increased to 25% or more through thermal energy absorption after carrier injection. It can be raised. When 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 sufficiently causes an intersystem crossing from the excited triplet state to the excited singlet state to emit delayed fluorescence, so that light emission is performed. The efficiency can be dramatically improved.

By using the compound represented by the general formula (1) of the present invention as a light-emitting material of a light-emitting layer, an excellent organic light-emitting element such as an organic photoluminescence element (organic PL element) or an organic electroluminescence element (organic EL element) is obtained. Can be provided. The organic photoluminescence element has a structure in which at least a light emitting layer is formed on a substrate. Further, the organic electroluminescence element has a structure in which at least an anode, a cathode, and an organic layer are formed between the anode and the cathode. The organic layer includes at least the light emitting layer, and may be composed 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. FIG. 1 shows a specific example of the structure of an organic electroluminescence element. 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.
Hereinafter, each member and each layer of the organic electroluminescence element will be described. Note that the description of the substrate and the light emitting layer also applies to the substrate and the light emitting layer of the organic photoluminescence element.

(substrate)
The organic electroluminescence device of the present invention is preferably supported on a substrate. This substrate is not particularly limited, and may be any substrate conventionally used in organic electroluminescent elements, and 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, a material using a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) as an electrode material 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, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous and transparent conductive film may be used. The anode may be formed by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering, and forming a pattern of a desired shape by a photolithography method, or when the pattern accuracy is not required so much (about 100 μm or more). ), A pattern may be formed via a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Alternatively, when a material that can be applied such as an organic conductive compound is used, a wet film forming method such as a printing method and a coating method can be used. When light is extracted from the anode, the transmittance is desirably greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. Further, the thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

(cathode)
On the other hand, as a cathode, a metal having a small work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used as an electrode material. Specific examples of such an electrode material 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 them, a mixture of an electron-injecting metal and a second metal which is a stable metal having a large work function value, such as a magnesium / silver mixture, from the viewpoint of durability against electron injection and oxidation. Preferred are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be manufactured by forming a thin film from these electrode materials by a method such as evaporation or sputtering. Further, 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 emitted light, if either 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 for the cathode, a transparent or translucent cathode can be produced, and by applying this, an element in which both the anode and the cathode are transmissive can be used. Can be made.

(Light emitting layer)
The light-emitting layer is a layer that emits light after the exciton is 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 a luminescent material and a host material. As the light emitting material, one or more selected from the group of compounds of the present invention represented by the general formula (1) can be used. In order for the organic electroluminescence device and the organic photoluminescence device of the present invention to exhibit high luminous efficiency, it is important to confine singlet and triplet excitons generated in the luminescent material in the luminescent material. Therefore, it is preferable to use a host material in the light emitting layer in addition to the light emitting material. As a host material, an organic compound in which at least one of excited singlet energy and excited triplet energy has a higher value than the light-emitting material of the present invention can be used. As a result, the singlet exciton and the triplet exciton 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 luminous efficiency can be sufficiently obtained. However, even if the singlet exciton and the triplet exciton cannot be sufficiently confined, high luminous efficiency can be obtained in some cases. Therefore, a host material that can realize high luminous efficiency is particularly limited. And can be used in the present invention. In the organic light emitting device or the organic electroluminescence 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 emission and delayed fluorescence emission. Note that light emission from the host material may be partially or partially emitted.
When a host material is used, the amount of the compound of the present invention, which is a light emitting material, contained in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and 50% by weight or more. % By weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.
The host material in the light-emitting layer is preferably an organic compound having a hole-transporting ability and an electron-transporting ability, preventing a long wavelength of light emission, and having a high glass transition temperature.

(Injection layer)
The injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the light emission luminance.There is a hole injection layer and an electron injection layer, and between the anode and the light emitting layer or the hole transport layer, And between the cathode and the light emitting layer or the electron transporting layer. An injection layer can be provided as needed.

(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 out 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 transport layer, and blocks holes from passing through the light emitting layer toward the electron transport layer. The blocking layer can also be used to prevent excitons from diffusing out of the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also have a function as an exciton blocking layer. The electron blocking layer or the exciton blocking layer referred to in the present specification is used in a sense that a single layer includes a layer having the functions of an electron blocking layer and an exciton blocking layer.

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

(Electron blocking layer)
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role of transporting holes and preventing electrons from reaching the hole transporting layer, 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. The light emitting layer can be efficiently confined in the light emitting layer, and the light emitting efficiency of the element 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 at the same time. That is, when the exciton blocking layer is provided on the anode side, the layer can be inserted between the hole transport layer and the light emitting layer adjacent to the light emitting layer, and when the layer is inserted on the cathode side, the light emitting layer and the cathode Can be inserted adjacent to the light emitting layer. A hole injection layer, an electron blocking layer, and the like can be provided between the anode and the exciton blocking layer adjacent to the light emitting layer on the anode side. An electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided between the electron blocking layer and the electron blocking layer. When a blocking layer is provided, it is preferable that at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is 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 transporting material has any of hole injection or transport and electron barrier properties, and may be any of an organic substance and an inorganic substance. 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, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, and conductive polymer oligomers, particularly thiophene oligomers. It is preferable to use an aromatic tertiary amine compound and a styrylamine compound, and it is more preferable to use an aromatic tertiary amine compound.

(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 transporting 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 usable electron transporting layers include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, and oxadiazole derivatives. Further, in the oxadiazole derivative, a thiadiazole derivative in which an 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 the electron transporting material. Further, a polymer material in which these materials are introduced into a polymer chain, or a polymer material in which these materials are used as a polymer main chain can be used.

  When producing an organic electroluminescence element, the compound represented by the general formula (1) may be used not only for the light emitting layer but also for layers other than the light emitting layer. At that time, the compound represented by the general formula (1) used for the light emitting layer and the compound represented by the general formula (1) used for layers other than the light emitting layer may be the same or different. For example, the compound represented by the general formula (1) may be used in the above injection layer, blocking layer, hole blocking layer, electron blocking layer, exciton blocking layer, hole transport layer, electron transport layer, and the like. . The method for forming these layers is not particularly limited, and they may be formed by either a dry process or a wet process.

Hereinafter, preferable materials that can be used for the organic electroluminescence device will be specifically exemplified. However, materials that can be used in the present invention are not limited to the following exemplified compounds. Further, even a compound exemplified as a material having a specific function can be diverted as a material having another function. Incidentally, R in the structural formula of the following exemplary compounds, R ', R ₁ ~R ₁₀ each independently represent a hydrogen atom or a substituent. X represents a carbon atom or a heteroatom 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, preferable compounds that can be used as a host material of the light-emitting layer are described.

  Next, preferable compound examples that can be used as the hole injection material are described.

  Next, preferable compound examples that can be used as a hole transport material are described.

  Next, preferred examples of compounds that can be used as an electron blocking material will be described.

  Next, examples of preferable compounds that can be used as the hole blocking material will be described.

  Next, preferable compound examples that can be used as an electron transport material are described.

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

  Preferred examples of compounds that can be further added are given below. For example, it may be added as a stabilizing material.

The organic electroluminescence device manufactured by the above method emits light by applying an electric field between the anode and the cathode of the obtained device. At this time, if the light emission is due to the excited singlet energy, light having a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. 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 emission, the emission lifetime can be distinguished between fluorescence and delayed fluorescence.
On the other hand, phosphorescence is hardly observed at room temperature because ordinary triplet compounds such as the compound of the present invention have excited triplet energies which are unstable and are converted to heat and the like, and have a short life and are immediately deactivated. In order to measure the excited triplet energy of an ordinary organic compound, it can be measured by observing light emission at a very low temperature.

  The organic electroluminescence device of the present invention can be applied to any of a single device, a device 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 having significantly improved luminous efficiency can be obtained by including a compound represented by the general formula (1) in a 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 manufacture an organic electroluminescence display device using the organic electroluminescence device of the present invention. ) Can be referred to. In particular, the organic electroluminescent device of the present invention can be applied to organic electroluminescent lighting and backlight, which are in great demand.

Hereinafter, the features of the present invention will be described more specifically with reference to Synthesis Examples and Examples. The materials, processing contents, processing procedures, and the like described below can be appropriately changed 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 described below. The measurement of the HOMO level and the LUMO level was performed using an atmospheric photoelectron spectrometer (manufactured by Riken Keiki: AC3) and a UV / Vis / NIR spectrophotometer (manufactured by PerkinElmer: LAMBDA950) to evaluate the thermal stability. Was performed using TGA-DTA (manufactured by Bruker: TG-DTA2400SA) and DSC (NETZSCH Say: DSC204 F1 Phoenix), and the measurement of the change over time in the emission intensity was performed using a fluorescence spectrophotometer (manufactured by Horiba: FluoroMax-4). The light emission characteristics were evaluated using a source meter (Keisley: 2400 series), a semiconductor parameter analyzer (Agilent Technology: E5273A), an optical power meter measurement device (Newport: 1930C), and optical Spectrometer (Ocean Optics, Inc.) : USB2000), spectroradiometer (manufactured by TOPCON CORPORATION: SR-3) and a streak camera (Hamamatsu Photonics (Ltd.) C4334 type manufactured) was used.
In this example, the sublimation temperature and the decomposition temperature were measured by vacuum / normal pressure TGA-DTA (TG-DTA2400SA manufactured by Bruker). The sublimation temperature was 1 Pa, the temperature at which 5% weight loss occurred after the solvent and water, etc., contained in the compound were removed and the weight was stabilized. The decomposition temperature was the temperature at which 10% weight loss occurred at 1 atm.

(Synthesis example 1)

A 1 L eggplant flask was charged with 2,7-dibromocarbazole (15.9 g) and copper (I) cyanide (21.9 g), and DMF (500 mL) was added. After heating at 150 ° C. for 24 hours, the mixture was allowed to cool and poured into an aqueous solution of ethylenediamine. The precipitate was collected by filtration to obtain 2,7-dicyanocarbazole (10.4 g).
Sodium hydride (240 mg) was placed in a 200 mL eggplant flask, and washed with hexane. After adding tetrahydrofuran (75 mL) and 2,7-dicyanocarbazole (1.09 g) and stirring at room temperature for 1.5 hours, 4,5-difluorophthalonitrile (330 mg) was added and the mixture was further stirred at room temperature for 22 hours. Water (25 mL) was added, and the precipitate was collected by filtration. The filtrate was purified by subjecting it to silica gel column chromatography to obtain compound 1 (475 mg, yield 43%).
FIG. 2 shows the ¹ H NMR spectrum of a DMSO-d6 solution of Compound 1.

(Synthesis example 2)

A 1 L eggplant flask was charged with 2,7-dibromocarbazole (15.9 g) and copper (I) cyanide (21.9 g), and DMF (500 mL) was added. After heating at 150 ° C. for 24 hours, the mixture was allowed to cool and poured into an aqueous solution of ethylenediamine. The precipitate was collected by filtration to obtain 2,7-dicyanocarbazole (10.4 g).
Sodium hydride (480 mg) was placed in a 200 mL eggplant flask, and washed with hexane. After adding tetrahydrofuran (150 mL) and 2,7-dicyanocarbazole (2.17 g) and stirring at room temperature for 1.5 hours, tetrafluoroisophthalonitrile (400 mg) was added and the mixture was further stirred at room temperature for 60 hours. After the reaction solution was concentrated, it was purified by subjecting it to silica gel column chromatography to obtain compound 2 (494 mg, yield: 25%).

[Evaluation of weather resistance]
(Example 1)
Table 1 shows the results of measuring the HOMO level and the LUMO level of Compound 1 synthesized in Synthesis Example 1, and Table 2 shows the results of measuring the sublimation temperature and the decomposition temperature.
Further, Compound 1 was vacuum-deposited on quartz glass so as to have a thickness of 100 nm, and continuously irradiated with excitation light of 350 nm in a nitrogen atmosphere or the atmosphere, and a change with time of the emission intensity was measured. FIG. 3 shows the change over time in the light emission intensity in a nitrogen atmosphere, and FIG. 4 shows the change over time in the light emission intensity under the atmosphere.

(Comparative Examples 1 and 2)
For Comparative Compound 1 and Comparative Compound 2 represented by the following formulas, HOMO level and LUMO level measured under the same conditions as in Example 1 are shown in Table 1, sublimation temperature and decomposition temperature are shown in Table 2, and 350 nm FIGS. 3 and 3 show the change with time in the emission intensity when the excitation light is continuously irradiated.

As shown in Table 1, Compound 1 in which the carbazolyl group was substituted with a cyano group and Comparative Compound 2 both had a lower HOMO level and lower LUMO level than Comparative Compound 1 in which the carbazolyl group was not substituted with a cyano group. It has become something. Further, as shown in Table 2, Compound 1 and Comparative Compound 2 have a higher sublimation temperature and decomposition temperature than Comparative Compound 1, and are excellent in thermal stability. From these results, it was found that when a cyano group was introduced into the carbazolyl group substituted for cyanobenzene, the levels of HOMO and LUMO were lowered, and the heat resistance was improved.
On the other hand, as shown in FIGS. 3 and 3, Compound 1 in which the substitution position of the cyano group is the 2-position and the 7-position of the carbazolyl group shows the same photostability as Comparative Compound 1 in any environment. On the other hand, Comparative Compound 2 in which the substitution position of the cyano group is at the 3- and 6-positions of the carbazolyl group shows a large decrease in emission intensity over time as compared with Compound 1 and Comparative Compound 1, and in particular, the decrease under the atmosphere. The degree becomes significant. From these results, it was shown that the introduction of a cyano group only at the 3- and 6-positions of the carbazolyl group rather reduced the photostability. It has been found that a deep HOMO / LUMO level and high heat resistance can be achieved without impairing the properties.

[Production of organic light-emitting device and evaluation of light-emitting characteristics]
(Example 2)
A toluene solution of Compound 1 (concentration: 10 ⁻⁵ mol / L) was prepared in a glove box under an Ar atmosphere.
Further, a thin film of Compound 1 was formed to a thickness of 100 nm on a quartz substrate at a degree of vacuum of 5 × 10 ⁻⁴ Pa or less by a vacuum evaporation method to obtain an organic photoluminescence device.
Separately, Compound 1 and DPEPO are vapor-deposited on a quartz substrate by a vacuum vapor deposition method at a degree of vacuum of 5 × 10 ⁻⁴ Pa or less from different vapor deposition sources, and the concentration of Compound 1 is 6.0% by mass. A certain thin film was formed with a thickness of 100 nm to obtain an organic photoluminescence device.
FIG. 5 shows the measurement result of the emission spectrum of the toluene solution of the compound 1 by 330 nm excitation light, and FIG. 6 shows the measurement result of the transient decay curve of 402 nm emission by 280 nm excitation light. FIG. 7 shows the results of measuring the emission spectrum of the thin film of Compound 1 using 350 nm excitation light, and FIG. 8 shows the results of measuring the transient decay curve of 458 nm emission using 340 nm excitation light. FIG. 6 also shows a transient decay curve measured without nitrogen bubbling and a transient decay curve measured after nitrogen bubbling. In FIGS. 6 and 8, a component having a short emission life was determined to be fluorescence, and a component having a long emission life was determined to be delayed fluorescence.
The toluene solution of the compound 1 had an emission wavelength of 410 nm, and the photoluminescence quantum efficiency was 18.0% when bubbling air, and 32.0% when bubbling nitrogen. The thin film of Compound 1 had an emission wavelength of 458 nm and a photoluminescence quantum efficiency of 22.5% in the air and 33.5% in a nitrogen atmosphere. The thin film of Compound 1 and DPEPO had an emission wavelength of 432 nm, and the photoluminescence quantum efficiency was 34.4% under air and 35.4% under nitrogen atmosphere.
The emission lifetime of a toluene solution of Compound 1 was measured without nitrogen bubbling. The fluorescence lifetime τ ₁ was 8 ns, no delayed fluorescence was observed, and the fluorescence lifetime τ ₁ was measured after nitrogen bubbling. 8 ns, and the delayed fluorescence lifetime τ ₂ was 43 ns. The thin film of Compound ₁ had a fluorescence lifetime τ ₁ of 8.8 ns and a delayed fluorescence lifetime τ ₂ of 22.6 ns. From the above results, emission of delayed fluorescence of Compound 1 was confirmed.

(Example 3)
On a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed, each thin film was laminated at a degree of vacuum of 4 × 10 ⁻⁴ Pa by a vacuum evaporation method. First, NPD was formed to a thickness of 40 nm on ITO, and mCP was formed thereon to a thickness of 10 nm. Next, compound 1 and UGH-3 were co-evaporated from different evaporation sources to form a layer having a thickness of 25 nm, which was used as a light emitting layer. At this time, the concentration of compound 1 was 6% by weight. Next, TPBi was formed to a thickness of 50 nm, lithium fluoride (LiF) was vacuum-deposited thereon to 0.8 nm, and then aluminum (Al) was deposited to a thickness of 100 nm to form a cathode. Through the above steps, an organic electroluminescence device was manufactured.
The prepared organic electroluminescence device has a light emission maximum wavelength at 500 nm, and shows current density-external quantum efficiency characteristics in FIG. 9 and voltage-luminance-external quantum efficiency characteristics in FIG. The produced organic electroluminescence device achieved an external quantum efficiency exceeding 5%, and was confirmed to be an excellent device.

  The compound of the present invention has good light-emitting properties, a deep HOMO level and a deep LUMO level, and high light resistance and high heat resistance. Therefore, the compound of the present invention is useful as a light emitting material for an organic light emitting device. Further, since the organic light emitting device of the present invention contains a light emitting material, it can realize high luminous efficiency and excellent weather resistance. Therefore, the present invention has high industrial applicability.

Reference Signs List 1 substrate 2 anode 3 hole injection layer 4 hole transport layer 5 light emitting layer 6 electron transport layer 7 cathode

Claims (17)

A light-emitting material containing a compound represented by the following general formula (1).

[In the general formula (1), at least one of a cyano group, at least one carbazolyl group in which at least one of the 2- and 7-position is substituted with a cyano group R ¹ to R ⁵ of R ¹ to R ⁵ (However, when the 2-position is substituted with a cyano group, the 3-position is unsubstituted or substituted with a substituent other than a cyano group, and when the 7-position is substituted with a cyano group, 6-position is substituted. Position is unsubstituted or substituted with a substituent other than a cyano group), and the remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]   The light emitting material according to claim 1, wherein the carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group has both the 2-position and the 7-position substituted with a cyano group. The luminescent material according to claim 1, wherein R ^{1 in the} general formula (1) is a cyano group. R ² and R ³ or R ³ and R ^{4 in the} general formula (1) are a carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group. The luminescent material according to any one of the above. R ^{2 in the} general formula (1) is a cyano group, and R ¹ and R ^{3 to} R ⁵ are carbazolyl groups in which at least one of the 2-position and the 7-position is substituted with a cyano group. Item 7. A luminescent material according to Item 1. The luminescent material according to claim 1, wherein the carbazolyl group in which at least one of the 2-position and the 7-position is substituted with a cyano group has a structure represented by the following general formula (11).

[In the general formula (11), R ²¹ and R ^{23 to} R ²⁸ each independently represent a hydrogen atom or a substituent, and R ²² represents a cyano group. ] Luminescent material according to claim 6 in which R ²⁷ in the general formula (11) is characterized in that it is a cyano group. The luminescent material according to claim 6, wherein at least one of R ²¹ , R ^{23 to} R ²⁶ , and R ^{28 in} the general formula (11) is a substituted or unsubstituted carbazolyl group. Luminescent material according to claim 8, wherein R ²³ in formula (11) is characterized in that it is a substituted or unsubstituted carbazolyl group. Luminescent material according to claim 8, R ²³ and R ²⁶ in the general formula (11) is characterized in that it is a substituted or unsubstituted carbazolyl group.   The luminescent material according to any one of claims 8 to 10, wherein the carbazolyl group is substituted with a cyano group.   The luminescent material according to any one of claims 1 to 11, wherein the number of carbazole rings present in the molecule of the compound represented by the general formula (1) is four or less. A compound represented by the following general formula (1).

[In the general formula (1), at least one of a cyano group, at least one carbazolyl group in which at least one of the 2- and 7-position is substituted with a cyano group R ¹ to R ⁵ of R ¹ to R ⁵ (However, when the 2-position is substituted with a cyano group, the 3-position is unsubstituted or substituted with a substituent other than a cyano group, and when the 7-position is substituted with a cyano group, 6 Position is unsubstituted or substituted with a substituent other than a cyano group), and the remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]   An organic light-emitting device comprising a light-emitting layer containing the light-emitting material according to claim 1 on a substrate.   The organic light emitting device according to claim 14, which emits delayed fluorescence.   The organic light-emitting device according to claim 14, wherein the organic light-emitting device is an organic electroluminescence device. A delayed phosphor having a structure represented by the following general formula (1).

[In the general formula (1), at least one of a cyano group, at least one carbazolyl group in which at least one of the 2- and 7-position is substituted with a cyano group R ¹ to R ⁵ of R ¹ to R ⁵ (However, when the 2-position is substituted with a cyano group, the 3-position is unsubstituted or substituted with a substituent other than a cyano group, and when the 7-position is substituted with a cyano group, 6 is substituted. Position is unsubstituted or substituted with a substituent other than a cyano group), and the remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]

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