JP2021155350A - Cyclic azine compound, material for organic electroluminescent elements, electron transport material for organic electroluminescent elements, and organic electroluminescent element - Google Patents

Abstract

To provide a cyclic azine compound that contributes to making an organic electroluminescent element having excellent drive voltage properties and current efficiency.SOLUTION: A cyclic azine compound has a specific structure represented by formula (1).SELECTED DRAWING: Figure 1

Description

The present invention relates to a cyclic azine compound, a material for an organic electroluminescent element, an electron transport material for an organic electroluminescent element, and an organic electroluminescent element.

Organic electroluminescent devices are used not only for small displays but also for large televisions, lighting, and the like, and their development is being vigorously carried out.
For example, Patent Document 1 describes a cyclic azine having 2', 3', 5', 6'-tetramethyl-1,1': 4', 1 "-terphenylene ring, etc. as a material for an organic electroluminescent device. The compound is disclosed.

International Publication No. 2017/150930

However, in recent years, the market demand for organic electroluminescent devices has been increasing, and there is a demand for materials having excellent current efficiency characteristics, drive voltage characteristics, and long life characteristics.
Here, the organic electroluminescent device using the cyclic azine compound disclosed in Patent Document 1 is required to be further improved in terms of drive voltage characteristics and current efficiency.

One aspect of the present invention aims to provide a cyclic azine compound, a material for an organic electroluminescent element, and an electron transport material for an organic electroluminescent element that contribute to the production of an organic electroluminescent element having excellent drive voltage characteristics and current efficiency. Has been done.
Another aspect of the present invention is directed to providing an organic electroluminescent device having excellent drive voltage characteristics and current efficiency.

According to one aspect of the present invention, the cyclic azine compound represented by the formula (1) is provided:

In equation (1),
Ar ¹ and Ar ² are independent of each other.
Phenyl group, 1-naphthyl group, or 2-naphthyl group, or
These groups are
Alkyl groups with 1 to 12 carbon atoms,
Cycloalkyl group with 3 to 20 carbon atoms,
An aryl group having 6 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group.
Diarylboryl group,
Cyano group and
Represents a diarylphosphine oxide group, a group substituted with one or more selected from the group consisting of;
B ^{1 to} B ³ are
Any one forms a single bond with any ^{one of R 1 to} R ⁵ in the formula (2).
The remaining two both represent hydrogen atoms;

In equation (2),
R ^{1 to} R ⁵ are
Any one forms a single bond with any one of B ^{1 to} B ^{3 and forms a single bond.}
The remaining four are independently hydrogen atom, methyl group, phenyl group, 1-naphthyl group, 2-naphthyl group, 2-biphenyl group, 3-biphenyl group, 4-biphenyl group, 2-pyridyl group, 3 -Pyridyl group, 4-pyridyl group, 2- (2-pyridyl) phenyl group, 2- (3-pyridyl) phenyl group, 2- (4-pyridyl) phenyl group, 3- (2-pyridyl) phenyl group, 3 -(3-Pyridyl) phenyl group, 3- (4-pyridyl) phenyl group, 4- (2-pyridyl) phenyl group, 4- (3-pyridyl) phenyl group, or 4- (4-pyridyl) phenyl group show.

According to another aspect of the present invention, a material for an organic electroluminescent device containing the cyclic azine compound is provided.
According to another aspect of the present invention, an electron transport material for an organic electroluminescent device containing the cyclic azine compound is provided.
According to another aspect of the present invention, an organic electroluminescent device containing the cyclic azine compound is provided.

According to one aspect of the present invention, it is possible to provide a cyclic azine compound, a material for an organic electroluminescent element, and an electron transport material for an organic electroluminescent element that contribute to the production of an organic electroluminescent element having excellent drive voltage characteristics and current efficiency. can.
According to another aspect of the present invention, it is possible to provide an organic electroluminescent device having excellent drive voltage characteristics and current efficiency.

It is a schematic cross-sectional view which shows an example of the laminated structure of the organic electroluminescent element containing the cyclic azine compound which concerns on one aspect of this invention. It is a schematic cross-sectional view which shows an example (element Example-1) of the laminated structure of the organic electroluminescent device containing the cyclic azine compound which concerns on one aspect of this invention.

Hereinafter, the cyclic azine compound according to one aspect of the present invention will be described in detail.

<Cyclic azine compound>
The cyclic azine compound according to one aspect of the present invention is represented by the formula (1):

In equation (1),
Ar ¹ and Ar ² are independent of each other.
Phenyl group, 1-naphthyl group, or 2-naphthyl group, or
These groups are
Alkyl groups with 1 to 12 carbon atoms,
Cycloalkyl group with 3 to 20 carbon atoms,
An aryl group having 6 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group.
Diarylboryl group,
Cyano group and
Represents a diarylphosphine oxide group, a group substituted with one or more selected from the group consisting of;
B ^{1 to} B ³ are
Any one forms a single bond with any ^{one of R 1 to} R ⁵ in the formula (2).
The remaining two both represent hydrogen atoms;

In equation (2),
R ^{1 to} R ⁵ are
Any one forms a single bond with any one of B ^{1 to} B ^{3 and forms a single bond.}
The remaining four are independently hydrogen atom, methyl group, phenyl group, 1-naphthyl group, 2-naphthyl group, 2-biphenyl group, 3-biphenyl group, 4-biphenyl group, 2-pyridyl group, 3 -Pyridyl group, 4-pyridyl group, 2- (2-pyridyl) phenyl group, 2- (3-pyridyl) phenyl group, 2- (4-pyridyl) phenyl group, 3- (2-pyridyl) phenyl group, 3 -(3-Pyridyl) phenyl group, 3- (4-pyridyl) phenyl group, 4- (2-pyridyl) phenyl group, 4- (3-pyridyl) phenyl group, or 4- (4-pyridyl) phenyl group show.

Hereinafter, the cyclic azine compound represented by the formula (1) may be referred to as a cyclic azine compound (1). Definitions of substituents in the cyclic azine compound (1) and preferred specific examples thereof are as follows.

Ar ¹ and Ar ² are independent of each other.
Phenyl group, 1-naphthyl group, or 2-naphthyl group, or
These groups are
Alkyl groups with 1 to 12 carbon atoms,
Cycloalkyl group with 3 to 20 carbon atoms,
An aryl group having 6 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group.
Diarylboryl group,
Cyano group and
Represents a diarylphosphine oxide group, a group substituted with one or more selected from the group consisting of.
Ar ¹ and Ar ² are independent of each other in that they have excellent electron-transporting material properties.
Unsubstituted phenyl group or
It is preferably an aryl-substituted phenyl group having 6 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group.

The alkyl group having 1 to 12 carbon atoms which may be substituted with a phenyl group, a 1-naphthyl group, or a 2-naphthyl group in Ar ¹ and Ar ^{2 may be either a straight chain or a branched chain.} That is, it is a straight chain alkyl group having 1 to 12 carbon atoms or a branched chain alkyl group having 3 to 12 carbon atoms. It is preferably a straight chain alkyl group having 1 to 4 carbon atoms or a branched chain alkyl group having 3 to 4 carbon atoms. Preferred specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group and a t-butyl group.

Specific examples of the cycloalkyl group having 3 to 20 carbon atoms which may be substituted with a phenyl group, a 1-naphthyl group, or a 2-naphthyl group in Ar ¹ and Ar ^{2 include a cyclopropyl group and a cyclobutyl group.} Cyclopentyl group, cyclohexyl group, adamantyl group and diamantyl group can be mentioned.

Ar ¹ and Ar ² may be substituted with a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, and may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group. Specific examples of the 20 aryl groups include a phenyl group, a biphenylyl group, a naphthyl group, an anthrasenyl group, a phenanthryl group, a fluorenyl group, or a triphenylenyl group. The alkyl group having 1 to 12 carbon atoms which may be substituted with the aryl group having 1 to 20 carbon atoms is a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 to 4 carbon atoms. It is preferably a group. The linear alkyl group having 1 to 4 carbon atoms or the branched alkyl group having 3 to 4 carbon atoms includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and an s-. Specific examples include a butyl group and a t-butyl group.

Diarylboryl which may be substituted with a phenyl group, 1-naphthyl group, or 2-naphthyl group in Ar ¹ and Ar ^{2 includes dimethylboryl.}

Examples of the diarylphosphine oxide that may be substituted with a phenyl group, a 1-naphthyl group, or a 2-naphthyl group in ^{Ar 1} and Ar ^{2 include diphenylphosphine oxide.}

B ^{1 to} B ³ independently form a single bond together with ^{a hydrogen atom or R 1 to} R ⁵ in the above formula (2) ^{, and any one of B 1 to} B ^{3 is R 1} in the formula (2). to form a single bond together to R ^5.

In equation (2), R ^{1 to} R ⁵ are
Any one forms a single bond with any ^{one of B 1 to} B ³ in the formula (1).
The remaining four are independently hydrogen atom, methyl group, phenyl group, 1-naphthyl group, 2-naphthyl group, 2-biphenyl group, 3-biphenyl group, 4-biphenyl group, 2-pyridyl group, 3 -Pyridyl group, 4-pyridyl group, 2- (2-pyridyl) phenyl group, 2- (3-pyridyl) phenyl group, 2- (4-pyridyl) phenyl group, 3- (2-pyridyl) phenyl group, 3 -(3-Pyridyl) phenyl group, 3- (4-pyridyl) phenyl group, 4- (2-pyridyl) phenyl group, 4- (3-pyridyl) phenyl group, or 4- (4-pyridyl) phenyl group show.

R ^{1 to} R ⁵ are
Any one forms a single bond with any one of B ^{1 to} B ^{3 and forms a single bond.}
The remaining four are preferably hydrogen atoms, methyl groups, phenyl groups, or 4-biphenyl groups, respectively.

The first aspect of R ^{1 to} R ^{5 is}
One is to form a single bond together with B ^1,
The remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group.

The second aspect of R ^{1 to} R ^{5 is}
Any one forms a single bond with ^{B 2 and}
The remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group.

The third aspect of R ^{1 to} R ^{5 is}
One is to form a single bond together with B ^3,
The remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group.

Specific examples of the group represented by the formula (2) include the following (2-1) to (2-33) as preferable examples.

[Specific example of cyclic azine compound (1)]
Among the cyclic azine compounds according to one aspect of the present invention represented by the formula (1), specific examples of particularly preferable compounds include the following (1-1) to (1-40) of the present invention. The cyclic azine compound according to one embodiment is not limited to these.

Hereinafter, the use of the cyclic azine compound (1) will be described.
<Materials for organic electroluminescent devices, electron transport materials for organic electroluminescent devices>
The cyclic azine compound (1) is not particularly limited, but can be used, for example, as a material for an organic electroluminescent device. Further, the cyclic azine compound (1) can be used, for example, as an electron transport material for an organic electroluminescent device.
That is, the material for an organic electroluminescent device according to one aspect of the present invention contains the cyclic azine compound (1). Further, the electron transport material for an organic electroluminescent device according to one aspect of the present invention contains a cyclic azine compound (1). The material for an organic electroluminescent element and the electron transporting material for an organic electroluminescent element containing the cyclic azine compound (1) contribute to the production of an organic electroluminescent element having excellent drive voltage characteristics and current efficiency.

<Organic electroluminescent device>
The organic electroluminescent device according to one aspect of the present invention contains a cyclic azine compound (1).
The configuration of the organic electroluminescent device is not particularly limited, and examples thereof include the configurations (i) to (vi) shown below.
(I): anode / light emitting layer / cathode (ii): anode / hole transport layer / light emitting layer / cathode (iii): anode / light emitting layer / electron transport layer / cathode (iv): anode / hole transport layer / Light emitting layer / electron transport layer / cathode (v): anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (vi): anode / hole injection layer / charge generation layer / Hole transport layer / Light emitting layer / Electron transport layer / Cathode

Hereinafter, the organic electroluminescent device according to one aspect of the present invention will be described in more detail with reference to FIG. 1 by taking the configuration of the above (vi) as an example. FIG. 1 is a schematic cross-sectional view showing an example of a laminated structure of an organic electroluminescent device containing a cyclic azine compound according to one aspect of the present invention.
The organic electroluminescence device shown in FIG. 1 has a so-called bottom emission type element configuration, but the organic electroluminescence device according to one aspect of the present invention is limited to the bottom emission type element configuration. is not it. That is, the organic electroluminescence device according to one aspect of the present invention may have a top emission type device configuration or another known device configuration.

The organic electroluminescent device 100 includes a substrate 1, an anode 2, a hole injection layer 3, a charge generation layer 4, a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, and a cathode 8 in this order. However, some of these layers may be omitted, and conversely, other layers may be added. For example, an electron injection layer may be provided between the electron transport layer 7 and the cathode 8, the charge generation layer 4 is omitted, and the hole transport layer 5 is directly provided on the hole injection layer 3. May be good. Further, for example, a single layer having a function of a plurality of layers, such as an electron injection / transport layer having a function of an electron injection layer and a function of an electron transport layer in a single layer, is formed into the plurality of layers. It may be a configuration provided instead of. Further, for example, the single-layer hole transport layer 5 and the single-layer electron transport layer 7 may each be composed of a plurality of layers.

[Layer containing a cyclic azine compound represented by the formula (1)]
The organic electroluminescent device contains a cyclic azine compound represented by the above formula (1) in one or more layers selected from the group consisting of a light emitting layer and a layer between the light emitting layer and the cathode. Therefore, in the configuration example shown in FIG. 1, the organic electroluminescent device 100 contains the cyclic azine compound (1) in at least one layer selected from the group consisting of the light emitting layer 6 and the electron transport layer 7. In particular, it is preferable that the electron transport layer 7 contains the cyclic azine compound (1). The cyclic azine compound (1) may be contained in a plurality of layers included in the organic electroluminescent element, and when an electron injection layer is provided between the electron transport layer and the cathode, the electron injection layer is provided. The cyclic azine compound (1) may be contained.
In the following, the organic electroluminescent device 100 in which the electron transport layer 7 contains the cyclic azine compound (1) will be described.

[Board 1]
The substrate is not particularly limited, and examples thereof include a glass plate, a quartz plate, and a plastic plate. Further, in the case of a configuration in which light emission is taken out from the substrate 1 side, the substrate 1 is transparent with respect to the wavelength of light.

Examples of the light-transmitting plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, and polycarbonate (Plastic film). PC), a film composed of cellulose triacetate (TAC), cellulose acetate propionate (CAP) and the like can be mentioned.

[Anode 2]
An anode 2 is provided on the substrate 1 (on the hole injection layer 3 side).
In the case of an organic electroluminescent device in which light emission is taken out through an anode, the anode is formed of a material that allows or substantially passes the light emission.

The transparent material used for the anode is not particularly limited, but for example, indium-tin oxide (ITO; Indium Tin Oxide), indium-zinc oxide (IZO; Indium Zinc Oxide), tin oxide, and aluminum.・ Dope-type tin oxide, magnesium-indium oxide, nickel-tungsten oxide, other metal oxides, metal nitrides such as gallium nitride, metal serene products such as zinc selenium, and metal sulfides such as zinc sulfide. Can be mentioned.
In the case of an organic electroluminescent device having a configuration in which light is extracted only from the cathode side, the transmission characteristics of the anode are not important. Therefore, examples of the material used for the anode in this case include gold, iridium, molybdenum, palladium, platinum and the like.
A buffer layer (electrode interface layer) may be provided on the anode.

[Hole injection layer 3, hole transport layer 5]
Between the anode 2 and the light emitting layer 6 described later, a hole injection layer 3, a charge generating layer 4 described later, and a hole transport layer 5 are provided in this order from the anode 2 side.
The hole injection layer and the hole transport layer have a function of transmitting holes injected from the anode to the light emitting layer, and the hole injection layer and the hole transport layer are interposed between the anode and the light emitting layer. As a result, more holes are injected into the light emitting layer at a lower electric field.

The hole injection layer and the hole transport layer also function as electron barrier layers. That is, the electrons injected from the cathode and transported from the electron injecting layer and / or the electron transporting layer to the light emitting layer are generated by the electron barrier existing at the interface between the light emitting layer and the hole injecting layer and / or the hole transporting layer. , Leakage into the hole injection layer and / or the hole transport layer is suppressed. As a result, the electrons are accumulated at the interface in the light emitting layer, which has the effect of improving the current efficiency and the like, and an organic electroluminescent device having excellent light emitting performance can be obtained.

The material of the hole injection layer and the hole transport layer has at least one of hole injection property, hole transport property, and electron barrier property. The material of the hole injection layer and the hole transport layer may be either an organic substance or an inorganic substance.

Specific examples of materials for the hole injection layer and the hole transport layer include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, and amino-substituted chalcones. Derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilben derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers (particularly thiophene oligomers), porphyrin compounds, aromatic tertiary amine compounds, styryl Examples include amine compounds. Among these, a porphyrin compound, an aromatic tertiary amine compound, and a styrylamine compound are preferable, and an aromatic tertiary amine compound is particularly preferable.

Specific examples of the aromatic tertiary amine compound and the styrylamine compound include N, N, N', N'-tetraphenyl-4,4'-diaminophenyl, N, N'-diphenyl-N, N'-. Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD), 2,2-bis (4-di-p-tolylaminophenyl) propane, 1,1-bis (4-Di-p-tolylaminophenyl) cyclohexane, N, N, N', N'-tetra-p-tolyl-4,4'-diaminobiphenyl, 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane, bis (4-dimethylamino-2-methylphenyl) phenylmethane, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N'-diphenyl-N, N' -Di (4-methoxyphenyl) -4,4'-diaminobiphenyl, N, N, N', N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'-bis (diphenylamino) quadri Phenyl, N, N, N-tri (p-tolyl) amine, 4- (di-p-tolylamino) -4'-[4- (di-p-tolylamino) styryl] Stilben, 4-N, N-diphenyl Amino- (2-diphenylvinyl) benzene, 3-methoxy-4'-N, N-diphenylaminostillbenzene, N-phenylcarbazole, 4,4'-bis [N- (1-naphthyl) -N-phenylamino ] Biphenyl (NPD), 4,4', 4''-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA) and the like.
Inorganic compounds such as p-type-Si and p-type-SiC can also be mentioned as examples of the material of the hole injection layer and the material of the hole transport layer.

The hole injection layer and the hole transport layer may have a single-layer structure made of one or more kinds of materials, or may have a laminated structure made of a plurality of layers having the same composition or different compositions.

[Charge generation layer 4]
A charge generation layer 4 may be provided between the hole injection layer 3 and the hole transport layer 5.
The material of the charge generation layer is not particularly limited, but for example, dipyrazino [2,3-f: 2', 3'-h] quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT). -CN).
The charge generation layer may have a single-layer structure made of one or more kinds of materials, or may have a laminated structure made of a plurality of layers having the same composition or different compositions.

[Light emitting layer 6]
A light emitting layer 6 is provided between the hole transport layer 5 and the electron transport layer 7, which will be described later.
Examples of the material of the light emitting layer include a phosphorescent light emitting material, a fluorescent light emitting material, and a thermal activated delayed fluorescent light emitting material. In the light emitting layer, electron-hole pairs are recombined, resulting in light emission.

The light emitting layer may consist of a single low molecular weight material or a single polymer material, but more generally it consists of a host material doped with a guest compound. The luminescence comes primarily from the dopant and can have any color.

Examples of the host material include compounds having a biphenyl group, a fluorenyl group, a triphenylsilyl group, a carbazole group, a pyrenyl group, and an anthryl group. More specifically, DPVBi (4,4'-bis (2,2-diphenylvinyl) -1,1'-biphenyl), BCzVBi (4,4'-bis (9-ethyl-3-carbazobinylene) 1, 1'-biphenyl), TBADN (2-talshalbutyl-9,10-di (2-naphthyl) anthracene), ADN (9,10-di (2-naphthyl) anthracene), CBP (4,4'-bis) (Carbazole-9-yl) biphenyl), CDBP (4,4'-bis (carbazole-9-yl) -2,2'-dimethylbiphenyl), 2- (9-phenylcarbazole-3-yl) -9- [Examples include 4- (4-phenylphenylquinazoline-2-yl) carbazole, 9,10-bis (biphenyl) anthracene and the like.

Examples of the fluorescent dopant include anthracene, pyrene, tetracene, xanthene, perylene, lubrene, coumarin, rhodamine, quinacridone, dicyanomethylenepyran compound, thiopyran compound, polymethine compound, pyrylium, thiapyrrylium compound, fluorene derivative, perifrantene derivative and indenoperylene. Examples thereof include derivatives, bis (azinyl) amine boron compounds, bis (azinyl) methane compounds, carbostyryl compounds, and the like. The fluorescent dopant may be a combination of two or more selected from these.

Examples of the phosphorescent dopant include organic metal complexes of transition metals such as iridium, platinum, palladium, and osmium.

Specific examples of the fluorescent dopant and phosphorescent dopant include Alq3 (tris (8-hydroxyquinoline) aluminum), DPAVBi (4,5'-bis [4- (di-p-tolylamino) styryl] biphenyl), perylene, and bis [ 2- (4-n-hexylphenyl) quinoline] (acetylacetonate) iridium (III), Ir (PPy) 3 (tris (2-phenylpyridine) iridium (III)), and FIrPic (bis (3,5-) Difluoro-2- (2-pyridyl) phenyl- (2-carboxypyridyl) iridium (III))) and the like can be mentioned.

Further, the light emitting material is not limited to being contained only in the light emitting layer. For example, the light emitting material may contain a layer (hole transport layer 5 or electron transport layer 7) adjacent to the light emitting layer. This makes it possible to further increase the current efficiency of the organic electroluminescent device.

The light emitting layer may have a single layer structure made of one or more kinds of materials, or may have a laminated structure made of a plurality of layers having the same composition or different compositions.

[Electron transport layer 7]
An electron transport layer 7 is provided between the light emitting layer 6 and the cathode 8 described later.
The electron transport layer has a function of transferring electrons injected from the cathode to the light emitting layer. By interposing the electron transport layer between the cathode and the light emitting layer, electrons are injected into the light emitting layer with a lower electric field.

As described above, the electron transport layer preferably contains the cyclic azine compound represented by the above formula (1).

Further, the electron transport layer may further contain a conventionally known electron transport material in addition to the cyclic azine compound (1). Conventionally known electron transport materials include, for example, 8-hydroxyquinolinate lithium (Liq), bis (8-hydroxyquinolinate) zinc, bis (8-hydroxyquinolinate) copper, and bis (8-hydroxyquinoli). Nart) manganese, tris (8-hydroxyquinolinate) aluminum, tris (2-methyl-8-hydroxyquinolinate) aluminum, tris (8-hydroxyquinolinate) gallium, bis (10-hydroxybenzo [h]] Kinolinate) berylium, bis (10-hydroxybenzo [h] quinolinate) zinc, bis (2-methyl-8-quinolinate) chlorogallium, bis (2-methyl-8-quinolinate) (o-cresolate) gallium, bis (2) -Methyl-8-quinolinate) -1-naphtholate aluminum, or bis (2-methyl-8-quinolinate) -2-naphtholate gallium, 2- [3- (9-phenanthrenyl) -5- (3-pyridinyl) Phenyl] -4,6-diphenyl-1,3,5-triazine, and 2- (4,''-di-2-pyridinyl [1,1': 3', 1''-terphenyl] -5- Il) -4,6-diphenyl-1,3,5-triazine, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), Bphenyl (4,7-diphenyl-1,10-) Phenantroline), BAlq (bis (2-methyl-8-quinolinolate) -4- (phenylphenolate) aluminum), bis (10-hydroxybenzo [h] quinolinate) berylium) and the like.

The electron transport layer may have a single-layer structure composed of one or more kinds of materials, or may have a laminated structure composed of a plurality of layers having the same composition or a different composition.
When the electron transport layer has a two-layer structure in which the light emitting layer side is the first electron transport layer and the cathode side is the second electron transport layer, the second electron transport layer preferably contains the cyclic azine compound (1).

[Cathode 8]
A cathode 8 is provided on the electron transport layer 7.
In the case of an organic electroluminescence device having a configuration in which only light emitted through the anode is extracted, the cathode can be formed from any conductive material.
Materials for the cathode 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 ) mixture, indium. , Lithium / aluminum mixture, rare earth metals and the like.
A buffer layer (electrode interface layer) may be provided on the cathode (electron transport layer side).

[Formation method of each layer]
For each layer except the electrodes (anode, cathode) described above, the material of each layer (with a material such as a binder resin and a solvent if necessary) can be used, for example, by vacuum deposition method, spin coating method, casting method, LB ( It can be formed by thinning by a known method such as the Langmuir-Blodgett method).
The film thickness of each layer thus formed is not particularly limited and may be appropriately selected depending on the situation, but is usually in the range of 5 nm to 5 μm.

The anode and cathode can be formed by thinning the electrode material by a method such as vapor deposition or sputtering. A pattern may be formed through a mask having a desired shape during vapor deposition or sputtering, or a thin film may be formed by vapor deposition or sputtering, and then a pattern having a desired shape may be formed by photolithography.

The film thickness of the anode and the cathode is preferably 1 μm or less, and more preferably 10 nm or more and 200 nm or less.

The organic electroluminescent element according to one aspect of the present invention may be used as a kind of lamp such as an illumination or an exposure light source, a projection device of a type for projecting an image, or a still image or a moving image is directly visually recognized. It may be used as a display device (display) of the type to be used. When used as a display device for video reproduction, the drive method may be either a simple matrix (passive matrix) method or an active matrix method. Further, a full-color display device can be manufactured by using two or more kinds of organic electroluminescent devices of this embodiment having different emission colors.

The cyclic azine compound (1) according to one aspect of the present invention can be synthesized by appropriately combining known reactions (for example, Suzuki-Miyaura cross-coupling reaction).

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited to these examples.

^{1 1} H-NMR measurement was carried out using Gemini200 (manufactured by Varian).
The glass transition temperature was measured using DSC7020 (manufactured by Hitachi High-Tech Science Corporation).
The light emitting characteristics of the organic electroluminescent element were evaluated by applying a direct current to the manufactured element at room temperature and using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse Co., Ltd.).

Synthesis Example-1 Synthesis of compound (1-5)

2- [1,1'-biphenyl] -4-yl-4- [4'-chloro (1,1'-biphenyl) -4-yl] -6-phenylpyridine (2.00 g, 4) under a nitrogen stream .05 mmol), 2,4-diphenyl-6- [3- (4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) phenyltriazine (1.94 g, 4.45 mmol) , Palladium acetate (30 mg, 0.12 mmol), and 2-dicyclohexylphosphino-2', 4', 6'-triisopropylbiphenyl (X-Phos) (120 mg, 0.24 mmol) dissolved in tetrahydrofuran (40 mL). rice field. To this was added a 2 M aqueous potassium phosphate solution (6 mL, 12.1 mmol), and the mixture was stirred at 70 ° C. for 18 hours. After allowing to cool to room temperature, adding water to the suspension and stirring at room temperature, the solid was collected by suction filtration. The resulting solid was washed with water and then ethanol. This solid was dissolved in toluene (600 mL), activated carbon was added, and the mixture was stirred, filtered through Celite, and the solvent was evaporated under reduced pressure. The obtained solid was recrystallized from chlorobenzene (150 ml) to obtain a white solid (yield 2.0 g, yield 64%) of compound (1-5).

The glass transition temperature of compound (1-5) was 134 ° C.

Synthesis Example-2 Synthesis of compound (1-9)

Under a nitrogen stream, 4- [4'-chloro (1,1'-biphenyl) -3-yl] -2,6-diphenyltriazine (6.10 g, 14.53 mmol), 2,4-diphenyl-6- [ 3- (4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) phenylpyridine (6.92 g, 15.98 mmol), palladium acetate (65 mg, 0.29 mmol), and 2 -Dicyclohexylphosphino-2', 4', 6'-triisopropylbiphenyl (X-Phos) (277 mg, 0.58 mmol) was dissolved in tetrahydrofuran (145 mL). To this was added a 2 M aqueous potassium phosphate solution (22 mL, 43.6 mmol), and the mixture was stirred at 70 ° C. for 24 hours. After allowing to cool to room temperature, adding water to the suspension and stirring at room temperature, the solid was collected by suction filtration. The resulting solid was washed with water and then ethanol. This solid was dissolved in chlorobenzene (400 mL), activated carbon was added, and the mixture was stirred, filtered through Celite, and the solvent was evaporated under reduced pressure. The obtained solid was washed with toluene (600 ml) heated to the reflux temperature to obtain a white solid of compound (1-9) (yield 8.1 g, yield 64%).

The glass transition temperature of compound (1-9) was 111 ° C.

Then, the device evaluation was carried out using the obtained compound.

Device Example-1 (see FIG. 2)
(Preparation of substrate 101 and anode 102)
As a substrate having an anode on its surface, a glass substrate with an ITO transparent electrode in which a 2 mm wide indium tin oxide (ITO) film (thickness 110 nm) was patterned in a stripe shape was prepared. Then, after cleaning this substrate with isopropyl alcohol, surface treatment was performed by ozone ultraviolet cleaning.

(Preparation for vacuum deposition)
Each layer was vacuum-deposited by a vacuum-film deposition method on the surface-treated substrate after cleaning, and each layer was laminated and formed.
First, the glass substrate was introduced into a vacuum vapor deposition tank, and the pressure was reduced to ^{1.0 × 10 -4 Pa.} Then, each layer was produced in the following order according to the film forming conditions of each layer.

(Preparation of hole injection layer 103)
Sublimated and purified N- [1,1'-biphenyl] -4-yl-9,9-dimethyl-N- [4- (9-phenyl-9H-carbazole-3-yl) phenyl] -9H-fluorene-2 -Amine and 1,2,3-tris [(4-cyano-2,3,5,6-tetrafluorophenyl) methylene] cyclopropane were deposited at a rate of 0.15 nm / sec at 10 nm, and a hole injection layer was formed. 103 was prepared.

(Preparation of the first hole transport layer 1051)
Sublimated and purified N- [1,1'-biphenyl] -4-yl-9,9-dimethyl-N- [4- (9-phenyl-9H-carbazole-3-yl) phenyl] -9H-fluorene-2 -Amine was formed into a film at 85 nm at a rate of 0.15 nm / sec to prepare a first hole transport layer 1051.

(Preparation of the second hole transport layer 1052)
Sublimated and purified N-phenyl-N- (9,9-diphenylfluorene-2-yl) -N- (1,1'-biphenyl-4-yl) amine was deposited at a rate of 0.15 nm / sec to 5 nm. , The second hole transport layer 1052 was prepared.

(Preparation of light emitting layer 106)
Sublimated and purified 3- (10-phenyl-9-anthril) -dibenzofuran and 2,7-bis [N, N-di- (4-tertbutylphenyl)] amino-bisbenzofurano-9,9'-spirofluorene Was formed at a ratio of 95: 5 (mass ratio) at 20 nm to prepare a light emitting layer 106. The film forming rate was 0.18 nm / sec.

(Preparation of the first electron transport layer 1071)
Sublimated and purified 2- [3'-(9,9-dimethyl-9H-fluorene-2-yl) [1,1'-biphenyl] -3-yl] -4,6-diphenyl-1,3,5- Triazine was formed into a 6 nm film at a rate of 0.05 nm / sec to prepare a first electron transport layer 1071.

(Preparation of the second electron transport layer 1072)
Synthesis The compound (1-5) and Liq synthesized in Example-1 were formed into a film at a ratio of 50:50 (mass ratio) at 25 nm to prepare a second electron transport layer 1072. The film forming rate was 0.15 nm / sec.

(Preparation of cathode 108)
Finally, a metal mask was arranged so as to be orthogonal to the ITO stripe on the substrate, and a cathode 108 was formed. As the cathode, silver / magnesium (mass ratio 1/10) and silver were formed in this order at 80 nm and 20 nm, respectively, to form a two-layer structure. The film formation rate of silver / magnesium was 0.5 nm / sec, and the film formation rate of silver was 0.2 nm / sec.

^{As described above, the 2} organic electroluminescent device 100 having a light emitting area of 4 mm as shown in FIG. 2 was manufactured. Each film thickness was measured with a stylus type film thickness measuring meter (DEKTAK, manufactured by Bruker).

Further, this element was sealed in a nitrogen atmosphere glove box having an oxygen and water concentration of 1 ppm or less. Sealing was performed by using a glass sealing cap and a film-forming substrate (element) with a bisphenol F type epoxy resin (manufactured by Nagase ChemteX Corporation).

A direct current was applied to the organic electroluminescent element produced as described above, and the emission characteristics were evaluated using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse Co., Ltd.). As a light emitting characteristic, the current efficiency (cd / A) when a current density of 10 mA / cm ² was passed was measured, and the element life (h) at the time of continuous lighting was measured. The drive voltage and the current efficiency are relative values using the result in the device reference example 1 described later as a reference value (100). The obtained measurement results are shown in Table 1.

Element Example-2
An organic electroluminescent device in the same manner as in Device Example-1 except that compound (1-9) synthesized in Synthesis Example-2 was used instead of compound (1-5) in Device Example-2. Was prepared and evaluated. The obtained measurement results are shown in Table 1.

Element reference example-1
Device Example-1 except that the compound (ETL-1) described in Patent Document 1 (International Publication No. 2017/150930) was used instead of the compound (1-5). An organic electroluminescent device was produced and evaluated in the same manner as in the above. The obtained measurement results are shown in Table 1.

Since the cyclic azine compound (1) according to one aspect of the present invention has a wide bandgap and a high triplet excitation level, it is used not only for conventional fluorescent devices but also for phosphorescent devices and thermal activated delayed fluorescence (TADF). ) Can be suitably used for an organic electroluminescent element.

1,101 Substrate 2,102 Anode 3,103 Hole injection layer
4 Charge generation layer 5,105 Hole transport layer 6,106 Light emitting layer 7,107 Electron transport layer 8,108 Cathode 51,1051 First hole transport layer 52,1052 Second hole transport layer 71,1071 First electron Transport layer 72,1072 Second electron transport layer 100 Organic electroluminescent element

Claims (9)

Cyclic azine compound represented by the formula (1):

In equation (1),
Ar ¹ and Ar ² are independent of each other.
Phenyl group, 1-naphthyl group, or 2-naphthyl group, or
These groups are
Alkyl groups with 1 to 12 carbon atoms,
Cycloalkyl group with 3 to 20 carbon atoms,
An aryl group having 6 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group.
Diarylboryl group,
Cyano group and
Represents a diarylphosphine oxide group, a group substituted with one or more selected from the group consisting of;
B ^{1 to} B ³ are
Any one forms a single bond with any ^{one of R 1 to} R ⁵ in the formula (2).
The remaining two both represent hydrogen atoms;

In equation (2),
R ^{1 to} R ⁵ are
Any one forms a single bond with any one of B ^{1 to} B ^{3 and forms a single bond.}
The remaining four are independently hydrogen atom, methyl group, phenyl group, 1-naphthyl group, 2-naphthyl group, 2-biphenyl group, 3-biphenyl group, 4-biphenyl group, 2-pyridyl group, 3 -Pyridyl group, 4-pyridyl group, 2- (2-pyridyl) phenyl group, 2- (3-pyridyl) phenyl group, 2- (4-pyridyl) phenyl group, 3- (2-pyridyl) phenyl group, 3 -(3-Pyridyl) phenyl group, 3- (4-pyridyl) phenyl group, 4- (2-pyridyl) phenyl group, 4- (3-pyridyl) phenyl group, or 4- (4-pyridyl) phenyl group show. Ar ¹ and Ar ² are independent of each other.
Phenyl group or
The cyclic azine compound according to claim 1, which is an aryl-substituted phenyl group having 6 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group. R ^{1 to} R ⁵ are
Any one forms a single bond with any one of B ^{1 to} B ^{3 and forms a single bond.}
The cyclic azine compound according to claim 1 or 2, wherein the remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group. R ^{1 to} R ⁵ are
One is to form a single bond together with B ^1,
The cyclic azine compound according to claim 1 or 2, wherein the remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group. R ^{1 to} R ⁵ are
Any one forms a single bond with ^{B 2 and}
The cyclic azine compound according to claim 1 or 2, wherein the remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group. R ^{1 to} R ⁵ are
One is to form a single bond together with B ^3,
The cyclic azine compound according to claim 1 or 2, wherein the remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group. A material for an organic electroluminescent device containing the cyclic azine compound according to any one of claims 1 to 6. An electron transport material for an organic electroluminescent device containing the cyclic azine compound according to any one of claims 1 to 6. An organic electroluminescent device containing the cyclic azine compound according to any one of claims 1 to 6.

Images