TECHNICAL FIELD

The present invention relates to a novel compound containing an azoline ring (oxazoline ring, thiazoline ring, or imidazoline ring), an electron transport/injection layer material containing the compound, an organic electroluminescent element (hereinafter, referred to as an organic EL element or simply abbreviated as an “element”) using the material, and the like.

BACKGROUND ART

In recent years, an organic EL element has attracted attention as a next-generation full color flat panel display, and active studies have been conducted. In order to promote practical application of the organic EL element, it is indispensable to reduce power consumption of the element (reduction in voltage and increase in external quantum yield) and to prolong lifetime of the element. In order to achieve these, a new electron transport/injection layer material has been developed.

Particularly, an object is to reduce power consumption of a blue electroluminescent element and to prolong lifetime thereof, and various electron transport/injection layer materials have been studied. For example, as described in Patent Literature 1 and Non Patent Literature 1, it is known that an organic EL element can be driven at a low voltage by using a pyridine derivative or a bipyridine derivative as an electron transport/injection layer material. Some of the organic EL elements have been put into practical use. However, characteristics thereof are insufficient for the organic EL elements to be adopted in more displays.

In addition, studies using benzimidazole or a benzothiazole derivative as an electron transport/injection layer material for an organic EL element have also been made (see Patent Literatures 2 to 4). Like the organic EL element using a pyridine derivative and a bipyridine derivative, some of the organic EL elements using benzimidazole and a benzothiazole derivative have been put into practical use. However, characteristics thereof are insufficient and further improvement is required.

CITATION LIST

Patent Literature

Patent Literature 1: JP 2003-123983 APatent Literature 2: US 2003/215667 APatent Literature 3: WO 2003/060956 APatent Literature 4: WO 2008/117976 A

Non Patent Literature

Non Patent Literature 1: Proceedings of the 10thInternational Workshop on Inorganic and Organic Electroluminescence (2000)

SUMMARY OF INVENTION

Technical Problem

As described above, generally, a compound used for the electron transport/injection layer material is a nitrogen-containing aromatic ring-based compound such as a pyridine-based compound, a benzimidazole-based compound, or a benzothiazole-based compound, and an aliphatic ring-based compound has not been studied. The present invention has been achieved in view of such related art and problems of the related art. One object of the present invention is to provide an electron transport/injection layer material which achieves characteristics required for an organic EL element, such as a driving voltage, a quantum efficiency, and element lifetime in a well-balanced manner, and can obtain a high quantum efficiency particularly. Another object of the present invention is to provide an organic EL element using the material.

Solution to Problem

As a result of intensive studies, the present inventors have succeeded in synthesizing a novel compound containing an azoline ring (oxazoline ring, thiazoline ring, or imidazoline ring), have found that characteristics such as a driving voltage, a quantum efficiency, and element lifetime are improved, particularly the quantum efficiency is improved by using this compound for an electron transport/injection layer of an organic EL element, and have completed the present invention based on this finding.

The above object is achieved by the following items.

[1] An azoline ring-containing compound represented by the following general formula (1).



In formula (1), φ represents an m-valent group derived from an aromatic hydrocarbon having 6 to 40 carbon atoms or an m-valent group derived from an aromatic heterocyclic ring having 2 to 40 carbon atoms, and at least one hydrogen atom of φ may be substituted by an alkyl having 1 to 6 carbon atoms, an aryl having 6 to 18 carbon atoms, or a heteroaryl having 2 to 18 carbon atoms,

Y's each independently represent —O—, —S—, or >N—Ar, Ar represents an aryl having 6 to 12 carbon atoms or a heteroaryl having 2 to 12 carbon atoms, at least one hydrogen atom of Ar may be substituted by an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 12 carbon atoms, or a heteroaryl having 2 to 12 carbon atoms, and R1to R5each independently represent a hydrogen atom or an alkyl having 1 to 4 carbon atoms, with the proviso that at least one of Ar in the >N—Ar and the R1to R5is a moiety bonded to L,

L's are each independently selected from the group consisting of a divalent group represented by the following formula (L-1) and a divalent group represented by the following formula (L-2),



in formula (L-1), X1to X6each independently represent ═CR6— or ═N—, at least two of X1to X6each represent ═CR6—, R6's in two ═CR6's in X1to X6are each a moiety bonded to φ or an azoline ring, and R6's in the other ═CR6's- each represent a hydrogen atom,

in formula (L-2), X7to X14each independently represent ═CR6— or ═N—, at least two of X7to X14each represent ═CR6—, R6's in two ═CR6's in X7to X14are each a moiety bonded to φ or an azoline ring, and R6's in the other ═CR6—'s each represent a hydrogen atom,

at least one hydrogen atom of L may be substituted by an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 10 carbon atoms, or a heteroaryl having 2 to 10 carbon atoms,

m represents an integer of 1 to 4, and when m represents 2 to 4, groups formed by an azoline ring and L may be the same as or different from one another, and

at least one hydrogen atom in a compound represented by formula (1) may be substituted by a deuterium atom.

[2] The azoline ring-containing compound according to [1], represented by the following general formula (2-1) or (2-2).



In formulas (2-1) and (2-2), φ represents an m-valent group derived from an aromatic hydrocarbon having 6 to 40 carbon atoms or an m-valent group derived from an aromatic heterocyclic ring having 2 to 40 carbon atoms, and at least one hydrogen atom of φ may be substituted by an alkyl having 1 to 6 carbon atoms, an aryl having 6 to 18 carbon atoms, or a heteroaryl having 2 to 18 carbon atoms,

in formula (2-1), Y's each independently represent —O—, —S—, or >N—Ar, Ar represents an aryl having 6 to 12 carbon atoms or a heteroaryl having 2 to 12 carbon atoms, and at least one hydrogen atom of Ar may be substituted by an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 12 carbon atoms, or a heteroaryl having 2 to 12 carbon atoms,

in formula (2-1), R1to R4each independently represent a hydrogen atom or an alkyl having 1 to 4 carbon atoms, with the proviso that R1and R2are the same as each other and R3and R4are the same as each other,

in formula (2-2), R4to R5each independently represent a hydrogen atom or an alkyl having 1 to 4 carbon atoms, with the proviso that R1and R2are the same as each other and R3and R4are the same as each other,

in formulas (2-1) and (2-2), L's are each independently selected from the group consisting of a divalent group represented by the following formula (L-1) and a divalent group represented by the following formula (L-2),



in formula (L-1), X1to X6each independently represent ═CR6— or ═N—, at least two of X1to X6each represent ═CR6—, R6's in two ═CR6's in X1to X6are each a moiety bonded to φ or an azoline ring, and R6's in the other ═CR6—'s each represent a hydrogen atom,

in formula (L-2), X7to X14each independently represent ═CR6— or ═N—, at least two of X7to X14each represent ═CR6—, R6's in two ═CR6's in X7to X14are each a moiety bonded to φ or an azoline ring, and R6's in the other ═CR6—'s each represent a hydrogen atom,

at least one hydrogen atom of L may be substituted by an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 10 carbon atoms, or a heteroaryl having 2 to 10 carbon atoms,

m represents an integer of 1 to 4, and when m represents 2 to 4, groups formed by an azoline ring and L may be the same as or different from one another, and

at least one hydrogen atom in a compound represented by formula (2-1) or (2-2) may be substituted by a deuterium atom.

[3] The azoline ring-containing compound according to [1] or [2], in which φ is selected from the group consisting of monovalent groups represented by the following formulas (φ1-1) to (φ1-18), divalent groups represented by the following formulas (φ2-1) to (φ2-34), trivalent groups represented by the following formulas (φ3-1) to (φ3-3), and tetravalent groups represented by the following formulas (φ4-1) and (φ4-2), and at least one hydrogen atom of φ may be substituted by an alkyl having 1 to 6 carbon atoms, an aryl having 6 to 18 carbon atoms, or a heteroaryl having 2 to 18 carbon atoms.



Z in the above formulas represents >CR2, >N—Ar, >N-L, —O—, or —S—, R's in >CR2each independently represent an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 12 carbon atoms, or a heteroaryl having 2 to 12 carbon atoms, R's may be bonded to each other to form a ring, Ar in >N—Ar represents an aryl having 6 to 12 carbon atoms or a heteroaryl having 2 to 12 carbon atoms, and L in >N-L represents L in the above general formula (1), (2-1), or (2-2).

[4] The azoline ring-containing compound according to any one of [1] to [3], in which L represents a divalent group of a ring selected from the group consisting of benzene, naphthalene, pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, isoquinoline, naphthyridine, phthalazine, quinoxaline, quinazoline, cinnoline, and pteridine, and at least one hydrogen atom of L may be substituted by an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 10 carbon atoms, or a heteroaryl having 2 to 10 carbon atoms.

[5] The azoline ring-containing compound according to any one of [1] to [4], in which Ar in >N—Ar as Y or Z is selected from the group consisting of phenyl, naphthyl, pyridinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, quinolinyl, isoquinolinyl, naphthyridinyl, phthalazinyl, quinoxalinyl, quinazolinyl, cinnolinyl, and pteridinyl, and at least one hydrogen atom of Ar in >N—Ar as Y may be substituted by an alkyl having 1 to 4 carbon atoms or an aryl having 6 to 10 carbon atoms.

[6] The azoline ring-containing compound according to any one of [1] to [5], in which R1to R4each independently represent a hydrogen atom or an alkyl having 1 to 4 carbon atoms, with the proviso that R1and R2are the same as each other, R3and R4are the same as each other, and not all of R1to R4represent hydrogen atoms simultaneously, and

m represents 1 or 2, and when m represents 2, groups formed by an azoline ring and L are the same as each other.

[7] The azoline ring-containing compound according to [1], represented by any one of the following formulas (1-1-108), (1-2-1), (1-2-2), (1-2-102), and (1-3-2).



[8] The azoline ring-containing compound according to [1], represented by any one of the following formulas (1-2-22), (1-2-146), (1-2-402), (1-2-522), and (1-3-8).



[9] The azoline ring-containing compound according to any one of [1] to [3], in which

φ is selected from the group consisting of divalent groups represented by the following formulas (φ2-1), (φ2-31), (φ2-32), (φ2-33), and (φ2-34), and at least one hydrogen atom of φ may be substituted by an aryl having 6 to 18 carbon atoms,



L represents a divalent group of a ring selected from the group consisting of benzene, pyridine, pyrazine, pyrimidine, pyridazine, and triazine, and at least one hydrogen atom of L may be substituted by an alkyl having 1 to 4 carbon atoms, an aryl having 6 to 10 carbon atoms, or a heteroaryl having 2 to 14 carbon atoms,

Ar in >N—Ar as Y is selected from the group consisting of phenyl, pyridinyl, pyrazinyl, pyrimidinyl, pyridazinyl, and triazinyl, and at least one hydrogen atom of the Ar may be substituted by an alkyl having 1 to 4 carbon atoms or an aryl having 6 to 10 carbon atoms,

R1to R4each independently represent a hydrogen atom or an alkyl having 1 to 4 carbon atoms, with the proviso that R1and R2are the same as each other, R3and R4are the same as each other, and not all of R1to R4represent hydrogen atoms simultaneously, and

m represents 2, and groups formed by an azoline ring and L are the same as each other.

[10] The azoline ring-containing compound according to [1], represented by any one of the following formulas (1-2-1022), (1-2-1025), (1-2-1026), (1-2-1027), (1-2-1031), and (1-2-1035).



[11] An electron transport material or an electron injection layer material, containing the azoline ring-containing compound according to any one of [1] to [10].

[12] An organic electroluminescent element including: a pair of electrodes formed of an anode and a cathode; a light emitting layer disposed between the pair of electrodes; and an electron transport layer and/or an electron injection layer disposed between the cathode and the light emitting layer and containing the material according to [11].

[13] The organic electroluminescent element according to [12], in which at least one of the electron transport layer and the electron injection layer further contains at least one selected from the group consisting of a quinolinol-based metal complex, a bipyridine derivative, a phenanthroline derivative, and a borane derivative.

[14] The organic electroluminescent element according to [12] or [13], in which at least one of the electron transport layer and the electron injection layer further contains at least one selected from the group consisting of an alkali metal, an alkaline earth metal, a rare earth metal, an oxide of an alkali metal, a halide of an alkali metal, an oxide of an alkaline earth metal, a halide of an alkaline earth metal, an oxide of a rare earth metal, a halide of a rare earth metal, an organic complex of an alkali metal, an organic complex of an alkaline earth metal, and an organic complex of a rare earth metal.

[15] A display apparatus or a lighting apparatus including the organic electroluminescent element according to any one of [12] to [14].

ADVANTAGEOUS EFFECTS OF INVENTION

According to a particularly preferred embodiment of the present invention, the novel compound of the present invention is characterized by being stable even when a voltage is applied to the compound in a thin film state, and having high charge transport ability. The compound is suitable, for example, as a charge transport material in an organic EL element. Use of the compound for an electron transport/injection layer of the organic EL element makes it possible to improve characteristics such as a driving voltage, a quantum efficiency, and element lifetime in a well-balanced manner. Among these characteristics, the compound particularly contributes to improvement of the quantum efficiency. In addition, use of this organic EL element makes it possible to manufacture a high-performance display apparatus such as a full-color display.

