JP2024007333A - Organic electroluminescent element - Google Patents

Abstract

To provide organic electroluminescent element that has both excellent drive voltage characteristics and current efficiency characteristics, and that has small efficiency change and efficiency change after continuous driving.SOLUTION: An organic electroluminescent element has an anode, a cathode opposite the anode, a light emitting layer disposed between the anode and the cathode, and an electron transport region disposed between the light emitting layer and the cathode, and the light emitting layer contains a boron compound represented by formula (1) and the electron transport region contains a specific triazine compound.SELECTED DRAWING: None

Description

The present disclosure relates to organic electroluminescent devices.

Organic electroluminescent devices can extract light of any wavelength by using appropriate light-emitting materials, and due to their usefulness, they are being applied not only to small display devices but also to lighting and other uses. , its development is being actively carried out. In any application, it is possible to express any color tone by combining red, green, and blue light emissions at appropriate intensities.

Conventionally, it has been desired that organic electroluminescent devices be driven at low voltage and emit light with high efficiency, and materials for organic electroluminescent devices have been gradually improved in recent years.

For example, Patent Documents 1 and 2 disclose organic electroluminescent elements with low driving voltage, high efficiency, and long life.

International Publication No. 2020/117026 JP2020-033264

However, in recent years, market demands for organic electroluminescent devices have become increasingly high, and there is a need to develop organic electroluminescent devices that not only have excellent drive voltage characteristics and current efficiency characteristics, but also allow precise control of color tone. . In order to enable detailed adjustment and control of color tone, it is desirable that the efficiency be high even in a wide range from low brightness to high brightness, and that the change in efficiency be small (hereinafter, the change in efficiency is (also simply called "efficiency change"). Furthermore, in order to enable fine adjustment and control of color tone, it is desirable that there be no change in efficiency before and after the element is driven continuously (hereinafter, this change in efficiency is simply referred to as "change in efficiency after continuous driving"). (also called)
One aspect of the present disclosure is directed to providing an organic electroluminescent device that has excellent drive voltage characteristics and current efficiency characteristics, and small changes in efficiency and small changes in efficiency after continuous driving.

An organic electroluminescent device according to one embodiment of the present disclosure includes:
1.
an anode;
a cathode facing the anode;
a light emitting layer disposed between the anode and the cathode;
an electron transport region disposed between the light emitting layer and the cathode;
The light emitting layer contains a boron compound represented by formula (1),
An organic electroluminescent device in which the electron transport region contains a triazine compound represented by formula (2).

In formula (1),
Ring A, Ring B, and Ring C may each independently have a substituent,
aromatic hydrocarbon ring having 6 to 20 ring atoms;
or represents an aromatic heterocycle having 5 to 20 ring atoms;
Ra, Rb, and Rc are each independently,
deuterium,
cyano group,
an alkyl group having 1 to 20 carbon atoms,
an optionally substituted amino group,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
a, b, c are each independently an integer of 0 to 4,
Ring A and ring B may be connected via an oxygen atom, a sulfur atom, NR', Ra or Rb,
R ¹ , R ² , R' may each independently have a substituent,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
R ¹ may be linked to ring A or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Ra, or Rc to form a ring structure,
R ² may be linked to ring B or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Rb, or Rc to form a ring structure.

In formula (2),
Ar ¹ represents a phenyl group, a naphthyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 6 carbon atoms;
Ar ² represents a phenyl group, a pyridyl group, a phenylpyridyl group, a pyridylphenyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 4 carbon atoms.
Ar ³ represents a phenyl group or a biphenylyl group which may be substituted with an alkyl group having 1 to 4 carbon atoms.
2.
In formula (1), at least one of rings A to C is a benzene ring which may have a substituent; 1. The organic electroluminescent device described in .
3.
In formula (1), rings A to C are rings containing a benzene structure which may have a substituent, 1. or 2. The organic electroluminescent device described in .
4.
In formula (1), at least one of Ra, Rb, and Rc is an alkyl group having 1 to 4 carbon atoms; 1. ~3. The organic electroluminescent device according to any one of the above.
5.
The boron compound represented by formula (1) is selected from the following: 1. ~4. The organic electroluminescent device according to any one of the above.

6.
5. The boron compound represented by formula (1) is the compound of 1-1 above. The organic electroluminescent device described in .
7.
The electron transport region includes a first electron transport layer;
at least a second electron transport layer disposed between the first electron transport layer and the cathode,
1. The second electron transport layer contains a triazine compound represented by formula (2). ~6. The organic electroluminescent device according to any one of the above.
8.
The triazine compound represented by formula (2) is as follows: 1. ~7. The organic electroluminescent device according to any one of the above.

9.
7. The second electron transport layer contains a compound represented by formula (2) and lithium quinolate (Liq). or 8. The organic electroluminescent device described in .

An organic electroluminescent element that is an embodiment of the present disclosure has both excellent drive voltage characteristics and current efficiency characteristics, and can further reduce efficiency changes and efficiency changes after continuous driving, and can be used in display devices and lighting devices. An element suitable for color tone reproduction can be realized.

1 is a schematic cross-sectional view showing an example of a stacked structure of an organic electroluminescent device including a cyclic azine compound according to one embodiment of the present disclosure.

Hereinafter, an organic electroluminescent device according to one embodiment of the present disclosure will be described in detail.
<Organic electroluminescent device>
The organic electric field device according to one aspect of the present disclosure includes:
an anode;
a cathode facing the anode;
a light emitting layer disposed between the anode and the cathode;
an electron transport region disposed between the light emitting layer and the cathode;
The light emitting layer contains a boron compound represented by formula (1),
An organic electroluminescent device in which the electron transport region contains a triazine compound represented by formula (2).

In formula (1),
Ring A, Ring B, and Ring C may each independently have a substituent,
aromatic hydrocarbon ring having 6 to 20 ring atoms;
or represents an aromatic heterocycle having 5 to 20 ring atoms;
Ra, Rb, and Rc are each independently,
deuterium,
cyano group,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
a, b, c are each independently an integer of 0 to 4,
Ring A and ring B may be connected via an oxygen atom, a sulfur atom, NR', Ra or Rb,
R ¹ , R ² , R' may each independently have a substituent,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
R ¹ may be linked to ring A or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Ra, or Rc to form a ring structure,
R ² may be linked to ring B or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Rb, or Rc to form a ring structure.

In formula (2),
Ar ¹ represents a phenyl group, a naphthyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 6 carbon atoms;
Ar ² represents a phenyl group, a pyridyl group, a phenylpyridyl group, a pyridylphenyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 4 carbon atoms.
Ar ³ represents a phenyl group or a biphenylyl group which may be substituted with an alkyl group having 1 to 4 carbon atoms. [About the structure of organic electroluminescent device]
The region between the anode and the light emitting layer is defined as a hole transport region. The hole transport region has the function of transmitting holes injected from the anode or holes generated within the hole transport region to the light emitting layer, and the hole transport region is connected between the anode and the light emitting layer. By intervening, many holes are injected into the light emitting layer with a lower electric field.

The hole transport region may be formed by multiple layers. The hole transport region preferably has a laminated structure of two or more layers, more preferably a laminated structure of four or less layers, and particularly preferably a laminated structure of three layers. When the hole transport region forms a laminated structure of three layers, the first hole transport layer, the second hole transport layer, and the third hole transport layer are formed in order from the anode side, and each of these layers independently performs hole injection. It is preferable to have one or more functions selected from the group consisting of a layer, a hole-generating layer, a hole-transporting layer, and an electron-blocking layer.

The region between the cathode and the light emitting layer is an electron transport region. The electron transport region has the function of transmitting electrons injected from the cathode or electrons generated within the electron transport region to the light emitting layer, and by interposing this electron transport region between the light emitting layer and the cathode, , more electrons are injected into the emissive layer at a lower electric field.

The electron transport region may be formed by multiple layers. The electron transport region preferably has a laminated structure of two or more layers, more preferably a laminated structure of four or less layers, and particularly preferably a laminated structure of three or less layers. When the electron transport region forms a three-layer laminated structure, the first electron transport layer, the second electron transport layer, and the third electron transport layer are formed in order from the anode side, and these are each independently a hole blocking layer, an electron transport layer, and a third electron transport layer. layer, and an electron injection layer.

Further, a charge generation layer may be provided between the anode and the cathode, and a light emitting layer, an electron transport region, etc. may be further provided as a separate unit.

The structure of the organic electroluminescent device according to one embodiment of the present disclosure is not particularly limited, and examples thereof include structures (i) to (vi) shown below.
(i): Anode/Emissive layer/Electron transport region/Cathode (ii): Anode/Hole transport layer/Emissive layer/Electron transport layer/Cathode (iii): Anode/Hole injection layer/Hole transport layer/Emissive Layer / electron transport layer / electron injection layer / cathode (iv): anode / hole injection layer / hole generation layer / hole transport layer / light emitting layer / electron transport layer / cathode (v): anode / hole injection layer /Hole transport layer/Electron blocking layer/Emissive layer/Hole blocking layer/Electron transport layer/Electron injection layer/Cathode (vi): Anode/Hole transport region/Emissive layer/Electron transport region/Charge generation layer/Positive Hole Transport Region/Light Emitting Layer/Electron Transport Region/Cathode Hereinafter, an organic electroluminescent device according to one embodiment of the present disclosure will be described in more detail with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view showing an example of a stacked structure of an organic electroluminescent element according to one embodiment of the present disclosure.
The organic electroluminescent device according to one aspect of the present disclosure may have a bottom emission type device configuration, a top emission type device configuration, or any other known device configuration.

The organic electroluminescent device 100 includes a substrate 1, an anode 2, a hole transport region 3, a light emitting layer 4, an electron transport region 5, and a cathode 6 in this order. The hole transport region 3 may have a laminated structure of a first hole transport layer 31, a second hole transport layer 32, and a third hole transport layer 33 in order from the anode side. The electron transport region 5 may have a laminated structure of a first electron transport layer 51, a second electron transport layer 52, and a third electron transport layer 53 in this order from the anode 2 side.
However, some of these layers and/or regions may be omitted, or other layers may be added. For example, a charge generation layer may be provided between the electron transport region 5 and the cathode 6, or the hole transport region 3 may be omitted and the light emitting layer 4 may be provided directly on the anode 2. In addition, a single layer that has the functions of multiple layers, such as an electron injection/transport layer that has both the functions of an electron injection layer and an electron transport layer in a single layer, may be used as a layer. A configuration may be provided instead of. Furthermore, 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.
[Substrate 1]
The substrate is not particularly limited, and examples include glass plates, quartz plates, plastic plates, and plastic films. Further, in the case of a configuration in which light is extracted from the substrate 1 side, the substrate 1 is transparent to the wavelength of light emitted from the light emitting layer 4. Further, in the case of a configuration in which light is emitted from the cathode 6 side, the base 1 may be provided with a reflecting plate that reflects light emitted from the light emitting layer 4 to the cathode 6 side.

Examples of optically transparent plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, and polycarbonate ( PC), cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like.
[Anode 2]
An anode 2 is provided between the substrate 1 and the hole transport region 3 . The anode 2 can function as an anode when current is passed through the organic electroluminescent element, which is one embodiment of the present disclosure.

In the case of a configuration in which the emitted light is extracted from the substrate 1 side, the anode 2 is formed of a material that allows the emitted light to pass through or substantially passes through it, or is formed with a film thickness sufficient to allow the emitted light to pass through. Further, in the case of a configuration in which light is extracted from the cathode 6 side, the anode 2 may have a function of reflecting light emitted from the light emitting layer 4 to the cathode 6 side. Specifically, the anode 2 may be formed of a material that can sufficiently reflect the wavelength of light emitted from the light emitting layer 4, or a laminated structure of a material with high reflectance and an appropriate material with high transmittance may be formed.

The material used for the anode 2 is not particularly limited in the case of a structure in which light emission is extracted from the substrate 1 side, but for example, indium-tin oxide (ITO), indium-zinc oxide, etc. (IZO; Indium Zinc Oxide), tin oxide, aluminum-doped tin oxide, magnesium-indium oxide, nickel-tungsten oxide, other metal oxides, metal nitrides such as gallium nitride, metals such as zinc selenide Selenide, metal sulfides such as zinc sulfide, etc. can be mentioned as electrode materials for the time being.

Note that in the case of an organic electroluminescent element configured to extract light only from the cathode 6 side, the transmission characteristics of the anode are not important. Therefore, examples of materials used for the anode in this case include gold, silver, iridium, molybdenum, palladium, platinum, or alloys thereof.
[Hole transport region 3]
A hole transport region 3 is provided between the anode 2 and a light emitting layer 4, which will be described later. A laminated structure may be formed in which the transport layers 33 are provided in this order.

The first hole transport layer 31, the second hole transport layer 32, and the third hole transport layer 33 forming the hole transport region 3 are each independently a hole injection layer, a hole generation layer, and a hole transport layer. , an electron blocking layer. Details of these functions will be described later. The hole injection layer has a function of efficiently injecting holes from the anode 2 and also has a function of efficiently injecting holes into an adjacent layer.

Specific examples of materials for the hole injection layer include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, Examples include styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers (especially thiophene oligomers), porphyrin compounds, aromatic tertiary amine compounds, and styryl amine compounds. It will be done. Among these, porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds are preferred, and aromatic tertiary amine compounds are particularly preferred. Further, the hole injection layer may contain a radialene compound (3) described below. Alternatively, it may be a composition containing the above-mentioned materials and a radialene compound (3) described below.

The hole-generating layer obtains electrons from the occupied orbits of the compound forming the adjacent layer by applying an electric field, and generates holes in the adjacent layer (synonymous with injecting holes into the adjacent layer). , and has the function of transporting the electrons obtained by itself to the anode 2 side.

Specific examples of materials for the hole generating layer include radialene compound (3) and dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarboxylate. Nitrile (HAT-CN), 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4 -TCNQ), 11,11,12,12-tetracyano-2,6-naphthoquinodimethane (TNAP), and 15,15,16,16-tetracyanoanthraquinodimethane (TCAQ). Further, the hole generating layer may contain a radialene compound (3) described below. Alternatively, it may be a composition containing the above-mentioned materials and a radialene compound (3) described below.

The hole transport layer has the function of transporting holes injected from the anode 2, the hole injection layer, and the hole generation layer, and injecting the holes into the adjacent layer.

The electron blocking layer has the function of preventing electrons from being injected into the layer from an adjacent layer. In particular, by blocking electron injection from the light-emitting layer, it is possible to increase the total number of charges that contribute to light emission within the light-emitting layer, which in turn contributes to increasing the light-emitting efficiency of the organic electroluminescent device.

Specific examples of materials for the hole transport layer and electron blocking layer include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, and amino-substituted chalcone derivatives. , oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers (especially thiophene oligomers), porphyrin compounds, aromatic tertiary amine compounds, styryl amines Examples include compounds. Among these, porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds are preferred, and aromatic tertiary amine compounds are particularly preferred. Further, the hole transport layer or the electron transport layer may contain a radialene compound (3) described below.

The first hole transport layer 31 preferably functions as a hole injection layer and/or a hole generation layer, and more preferably functions as a hole injection layer.

The second hole transport layer 32 preferably functions as a hole generation layer, a hole transport layer, and/or an electron blocking layer, and more preferably functions as a hole transport layer.

The third hole transport layer 33 preferably functions as a hole transport layer and/or an electron blocking layer, and more preferably functions as an electron blocking layer.

Specific examples of aromatic tertiary amine compounds and styrylamine compounds used in the hole injection layer, hole transport layer, and electron blocking layer 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-tolylaminophenyl)-4-phenylcyclohexane, bis(4-dimethylamino-2-methylphenyl)phenylmethane, bis(4-di-p-tolylamino phenyl)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)quadrifhenyl, N,N,N-tri(p-tolyl)amine, 4-(di-p-tolylamino)-4'-[4-(diphenylamino) -p-tolylamino)styryl]stilbene, 4-N,N-diphenylamino-(2-diphenylvinyl)benzene, 3-methoxy-4'-N,N-diphenylaminostilbenzene, 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 following compounds.

<Radialene compound>
The radialene compound that can be included in the hole transport region 3 is represented by formula (3):

In formula (3),
^R3 each independently represents a cyano group, a halogen atom, a fluoroalkyl group, an acyl group, a sulfonyl group, a phosphoryl group, an optionally substituted aromatic hydrocarbon group, or an optionally substituted aromatic heterocyclic group. represent.

Hereinafter, the radialene compound represented by formula (3) may be referred to as radialene compound (3). Preferred forms, definitions of substituents, and preferred specific examples of the radialene compound (3) are as follows.

Examples of the halogen atom represented by R ³ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Among these, a fluorine atom and a chlorine atom are preferred, and a fluorine atom is more preferred.

The acyl group represented by R ³ is preferably an acyl group having 2 to 10 carbon atoms containing a carbon at the carbonyl site, more preferably an acyl group having 2 to 10 carbon atoms substituted with a fluorine atom, and all hydrogen atoms are substituted with a fluorine atom. An acyl group having 2 to 10 carbon atoms in which is substituted with a fluorine atom is more preferable, and an acyl group having 2 to 6 carbon atoms in which all hydrogen atoms are substituted with fluorine atoms is particularly preferable.

The fluoroalkyl group represented by R ³ is an alkyl group having 1 to 20 carbon atoms in which one or more hydrogen atoms of the alkyl group are substituted with fluorine atoms, and all hydrogen atoms are substituted with fluorine atoms. A fluoroalkyl group having 1 to 20 carbon atoms is preferred, a fluoroalkyl group having 1 to 10 carbon atoms is more preferred, a fluoroalkyl group having 1 to 6 carbon atoms is even more preferred, and a fluoroalkyl group having 1 to 3 carbon atoms is particularly preferred. .

The optionally substituted aromatic hydrocarbon group represented by R ³ has 6 to 6 ring carbon atoms and may be substituted with one or more cyano group, halogen atom, acyl group, sulfonyl group, or phosphoryl group. An aromatic hydrocarbon group having 20 carbon atoms which may be connected or fused together is preferable, and an aromatic hydrocarbon group which may be connected or fused to a ring having 6 to 20 ring carbon atoms which may be substituted with a cyano group and/or a halogen atom. A hydrogen group is more preferable, and a phenyl group and a biphenylyl group substituted with a cyano group and/or a fluorine atom are particularly preferable.

The optionally substituted aromatic heterocyclic group represented by R ³ has 6 to 6 ring atoms that may be substituted with one or more cyano group, halogen atom, acyl group, sulfonyl group, or phosphoryl group. An aromatic heterocyclic group having 20 atoms, which may be connected or condensed, is preferable, and an aromatic heterocyclic group having 6 to 20 ring members, which may be substituted with a cyano group and/or a halogen atom, which may be connected or condensed. A cyclic group is more preferable, and a pyridyl group, pyrimidyl group, pyrazyl group, and triazinyl group substituted with a cyano group and/or a fluorine atom are particularly preferable.
[About formula (3-1)]
The radialene compound (3) preferably has a structure represented by formula (3-a).

In formula (3-a),
Ar ⁴ each independently represents an optionally substituted aromatic hydrocarbon group or an optionally substituted aromatic heterocyclic group.

The substituents of the optionally substituted aromatic hydrocarbon group and the optionally substituted aromatic heterocyclic group represented by R ³ and Ar ⁴ are each independently:
selected from deuterium, cyano group, halogen atom, fluoroalkyl group, acyl group, sulfonyl group, and phosphoryl group.

The preferred form of R ³ is the same as in formula (3).

The substituted aromatic hydrocarbon group represented by Ar ⁴ has 6 to 20 ring carbon atoms which may be substituted with one or more cyano group, halogen atom, acyl group, sulfonyl group, or phosphoryl group. An aromatic hydrocarbon group which may be linked or fused together is preferable, and an aromatic hydrocarbon group having 6 to 20 ring carbon atoms which may be substituted with a cyano group and/or a halogen atom, which may be linked or fused together. The group is more preferable, and a phenyl group and a biphenylyl group substituted with a cyano group and/or a fluorine atom are particularly preferable.

The optionally substituted aromatic heterocyclic group represented by Ar ⁴ has 6 to 6 ring atoms that may be substituted with one or more cyano group, halogen atom, acyl group, sulfonyl group, or phosphoryl group. An aromatic heterocyclic group having 20 atoms, which may be connected or condensed, is preferable, and an aromatic heterocyclic group having 6 to 20 ring members, which may be substituted with a cyano group and/or a halogen atom, which may be connected or condensed. A cyclic group is more preferable, and a pyridyl group, pyrimidyl group, pyrazyl group, and triazinyl group substituted with a cyano group and/or a fluorine atom are particularly preferable.
[About formula (3-b)]
Radialene compounds (3) and (3-a) preferably have a structure represented by formula (3-b).

In formula (3-b),
Each R ³¹ is independently selected from deuterium, a cyano group, a halogen atom, a fluoroalkyl group, an acyl group, a sulfonyl group, and a phosphoryl group.

Each s is independently an integer from 1 to 5.

Preferred forms of the halogen atom, fluoroalkyl group, and acyl group represented by R ³¹ are the same as those for R ³ .

R ³¹ is preferably selected from a cyano group, a fluorine atom, and a fluoroalkyl group, more preferably a cyano group and/or a fluorine atom, and even more preferably a cyano group and a fluorine atom.
[Light-emitting layer 4]
A light emitting layer 4 is provided between the hole transport region 3 and the electron transport region 5, which will be described later.

Examples of materials for the light-emitting layer include phosphorescent materials, fluorescent materials, and thermally activated delayed fluorescent materials. In the light-emitting layer, excitons are electrically generated by recombination of electron-hole pairs, and light is generated when the excitons are deactivated.

The light emitting layer 4 contains a boron compound (1) whose details will be described later. The emissive layer 4 may consist of a single low molecule material, but more commonly it consists of a host material doped with a guest compound. Examples of the guest material include fluorescent compounds, phosphorescent compounds, delayed fluorescent compounds, and the like. The light emission primarily comes from the guest material and can emit 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, a dibenzofuryl group, a dibenzothienyl group, and an anthryl group. More specifically, DPVBi (4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl), BCzVBi (4,4'-bis(9-ethyl-3-carbazovinylene) 1, 1'-biphenyl), TBADN (2-tert-butyl-9,10-di(2-naphthyl)anthracene), ADN (9,10-di(2-naphthyl)anthracene), CBP (4,4'-bis (carbazol-9-yl)biphenyl), CDBP (4,4'-bis(carbazol-9-yl)-2,2'-dimethylbiphenyl), 2-(9-phenylcarbazol-3-yl)-9- [4-(4-phenylphenylquinazolin-2-yl)carbazole, 9,10-bis(biphenyl)anthracene, etc.].

Examples of the fluorescent compound include boron compound (1), anthracene, pyrene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine, quinacridone, dicyanomethylenepyran compound, thiopyran compound, polymethine compound, pyrylium, thiapyrylium compound, and fluorene derivative. , periflanthene derivatives, indenoperylene 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 compound include metal complexes such as iridium complexes, platinum complexes, palladium complexes, and osmium complexes.

Specific examples of fluorescent compounds and phosphorescent compounds include Alq3 (tris(8-hydroxyquinolinolato)aluminum), DPAVBi (4,4'-bis[4-(di-p-tolylamino)styryl]biphenyl), perylene, bis[2-(4-n-hexylphenyl)quinoline](acetylacetonato)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.

The thermally activated delayed fluorescence emitting material can be used as either the host material or the guest material described above. In addition, the thermally activated delayed fluorescence emitting material does not itself emit light, but can play the role of efficiently transferring excitation energy to the fluorescent compound that forms the emissive layer at the same time as the thermally activated delayed fluorescence emitting material. .

Specific examples of thermally activated delayed fluorescence include boron compound (1), 4Cz-IPN (2,4,5,6-tetra(9-carbazolyl)-isophthalonitrile), 5Cz-BN (2,3, 4,5,6-penta(9-carbazolyl)-benzonitrile), DACTII(2-[3,6-bis(diphenylamino)carbazol-9-ylphenyl]-4,6-diphenyl-1,3,5 -triazine), etc.

Furthermore, the luminescent material is not limited to being contained only in the luminescent layer. For example, the luminescent material may be contained in a layer adjacent to the luminescent layer (hole transport layer 5 or electron transport layer 7). This further increases 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 multiple layers having the same composition or different compositions.
<Boron compound>
A boron compound included in the light emitting layer according to one embodiment of the present disclosure is represented by formula (1).

In formula (1),
Ring A, Ring B, and Ring C may each independently have a substituent,
aromatic hydrocarbon ring having 6 to 20 ring atoms;
or represents an aromatic heterocycle having 5 to 20 ring atoms;
Ra, Rb, and Rc are each independently,
deuterium,
cyano group,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
a, b, c are each independently an integer of 0 to 4,
Ring A and ring B may be connected via an oxygen atom, a sulfur atom, NR', Ra or Rb,
R ¹ , R ² , R' may each independently have a substituent,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
R ¹ may be linked to ring A or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Ra, or Rc to form a ring structure,
R ² may be linked to ring B or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Rb, or Rc to form a ring structure.

Hereinafter, the boron compound represented by formula (1) may be referred to as compound (1). The ring structure formed in compound (1), definitions of substituents, and preferred specific examples thereof are as follows.
[About rings A to C]
Ring A, Ring B, and Ring C may each independently have a substituent,
aromatic hydrocarbon ring having 6 to 20 ring atoms;
It is selected from aromatic heterocycles having 5 to 20 ring atoms.

Ring A, Ring B, and Ring C are each independently an aromatic hydrocarbon ring having 6 to 18 ring atoms or an aromatic heterocycle having 5 to 18 ring atoms, which may have a substituent. is preferable, an aromatic hydrocarbon ring having 6 to 12 ring atoms or an aromatic heterocycle having 5 to 12 ring atoms, more preferably an aromatic hydrocarbon ring having 6 to 9 ring atoms or ring atoms Aromatic heterocycles having a number of 5 to 9 are more preferred, benzene, benzofuran, benzothiophene, indole, benzimidazole, benzothiazole, and benzoxazole are more preferred, and benzene is particularly preferred.

Ring A and ring B may be connected via an oxygen atom, a sulfur atom, NR', Ra or Rb described below, and ring A and ring B may be connected through NR' or not connected. A structure in which ring A and ring B are not connected is preferable, and a structure in which ring A and ring B are not connected is more preferable.
[About Ra, Rb, and Rc]
Ra, Rb, and Rc are each independently,
deuterium,
cyano group,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
It is selected from heteroaromatic groups having 5 to 20 ring atoms.

Ra, Rb, and Rc are each independently preferably deuterium, an alkyl group having 1 to 20 carbon atoms, or a heteroaromatic group having 5 to 20 ring atoms; More preferred is an alkyl group having 1 to 20 carbon atoms.
[About a, b, c]
a, b, and c are each independently an integer of 0 to 4, each independently preferably 0 to 2, each independently more preferably 0 to 1, and even more preferably 1.
[About R ¹ , R ² , R']
R ¹ , R ² , R' may each independently have a substituent,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
R ¹ , R ² , and R' are each independently an aromatic hydrocarbon group having 6 to 20 ring atoms that may have a substituent, or a ring atom that may have a substituent. A heteroaromatic group having 5 to 20 ring atoms is preferable, an aromatic hydrocarbon group having 6 to 20 ring atoms which may have a substituent is more preferable, and a heteroaromatic group having 6 to 20 ring atoms substituted with an alkyl group is more preferable. 20 aromatic hydrocarbon groups are more preferred, and phenyl groups substituted with alkyl groups are particularly preferred.

R ¹ may be linked to ring A or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Ra, or Rc to form a ring structure,
R ² may be bonded to ring B or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Rb, or Rc to form a ring structure.
[Preferred example of boron compound (1)]
A boron compound represented by any one of compounds 1-1 to 1-54 is more preferred in terms of achieving both excellent drive voltage characteristics and current efficiency characteristics.

Among them, the boron compounds shown by 1-1, 1-2, 1-11, 1-12, 1-17, 1-18, 1-21, and 1-22 have particularly excellent driving voltage characteristics and current Preferred in terms of achieving both efficiency characteristics and efficiency change characteristics, 1-1, 1-11, and 1-17 are more preferred, and 1-1 is particularly preferred.
[Electron transport region 5]
An electron transport layer 5 is provided between the light emitting layer 4 and a cathode 6 to be described later, and from the anode 2 side, a first electron transport layer 51, a second electron transport layer 52, and a third electron transport layer 53 are arranged. A laminated structure provided in this order may be formed.

The electron transport region 5 contains a triazine compound represented by formula (2). The triazine compound may be included in multiple layers present in the electron transport region.

The first electron transport layer 51, second electron transport layer 52, and third electron transport layer 53 forming the electron transport region 5 each independently include an electron injection layer, an electron generation layer, an electron transport layer, and a hole blocking layer. one or more functions selected from the group. Details of these functions will be described later.

The electron injection layer has a function of efficiently injecting electrons from the cathode 6 or the charge generation layer, and also has a function of efficiently injecting electrons into an adjacent layer.

Specific examples of materials for the electron injection layer include metals such as lithium (Li), potassium (K), cesium (Cs), and ytterbium (Yb), lithium fluoride (LiF), sodium fluoride (NaF), and fluoride. Inorganic salts such as potassium (KF), lithium carbonate (Li2CO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), cesium carbonate (Cs2CO3), 8-hydroxyquinolinolatolithium (Liq), bis(8-hydroxyquino Examples include organometallic complexes such as zinc linolato, and compositions of these and a triazine compound represented by formula (2).

The electron transport layer has the function of transporting electrons injected from the charge generation layer, the cathode, and the electron injection layer, and injecting the electrons into adjacent layers.

The hole blocking layer has the function of blocking holes from being injected into the layer from an adjacent layer. In particular, by blocking hole injection from the light-emitting layer, it is possible to increase the total number of charges that contribute to light emission within the light-emitting layer, which in turn contributes to increasing the light-emitting efficiency of the organic electroluminescent device.

The electron transport layer and the hole blocking layer may contain a triazine compound represented by formula (2). As a specific example of the material for the electron transport layer and the hole blocking layer, in addition to the triazine compound (2) represented by formula (2), the material may further contain a conventionally known electron transport material. Conventionally known electron transport materials include, for example, 8-hydroxyquinolinolatolithium (Liq), bis(8-hydroxyquinolinolato)zinc, bis(8-hydroxyquinolinolato)copper, and bis(8-hydroxyquinolinolato). linolato) manganese, tris(8-hydroxyquinolinolato)aluminum, tris(2-methyl-8-hydroxyquinolinolato)aluminum, tris(8-hydroxyquinolinolato)gallium, bis(10-hydroxybenzo[h ] quinolinolato) beryllium, bis(10-hydroxybenzo[h]quinolinolato)zinc, bis(2-methyl-8-quinolinolato)chlorogallium, bis(2-methyl-8-quinolinolato)(o-cresolate) gallium, bis( 2-Methyl-8-quinolinolato)-1-naphtholate aluminum, or bis(2-methyl-8-quinolinolato)-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 -yl)-4,6-diphenyl-1,3,5-triazine, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), Bphen (4,7-diphenyl-1,10 -phenanthroline), BAlq (bis(2-methyl-8-quinolinolato)-4-(phenylphenolate)aluminum), and bis(10-hydroxybenzo[h]quinolinolato)beryllium), and compositions thereof. It will be done. Alternatively, a composition doped with these compounds and Liq may be used.
<Triazine compound>
The triazine compound included in the electron transport region according to one embodiment of the present disclosure is represented by formula (2):

In formula (2),
Ar ¹ represents a phenyl group, a naphthyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 6 carbon atoms;
Ar ² represents a phenyl group, a pyridyl group, a phenylpyridyl group, a pyridylphenyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 4 carbon atoms.
Ar ³ represents a phenyl group or a biphenylyl group which may be substituted with an alkyl group having 1 to 4 carbon atoms.

Hereinafter, the triazine compound represented by formula (2) may be referred to as triazine compound (2). Definitions of the substituents in the triazine compound (2) and preferred specific examples thereof are as follows.
[About Ar ¹ ]
Ar ¹ is selected from phenyl, naphthyl, biphenylyl.
Ar ¹ is preferably a phenyl group or a biphenylyl group, more preferably a phenyl group or a biphenyl-4-yl group, from the viewpoint of achieving both excellent drive voltage characteristics and current efficiency characteristics.
[About Ar ² ]
Ar ² is selected from a phenyl group, a pyridyl group, a phenylpyridyl group, a pyridylphenyl group, and a biphenylyl group, which may be substituted with an alkyl group having 1 to 4 carbon atoms.
Ar ² is preferably a phenyl group, a pyridyl group, or a biphenylyl group, more preferably a phenyl group or a biphenylyl group, and particularly preferably a phenyl group, from the viewpoint of achieving both excellent drive voltage characteristics and current efficiency characteristics.
[About Ar ³ ]
Ar ³ is selected from a phenyl group and a biphenylyl group, which may be substituted with an alkyl group having 1 to 4 carbon atoms.
Ar ³ is preferably a phenyl group, a biphenyl-2-yl group, or a biphenyl-4-yl group in terms of achieving both excellent drive voltage characteristics and current efficiency characteristics.
[Preferred example of triazine compound (2)]
The triazine compound (2) which is one embodiment of the present disclosure is more preferably a triazine compound represented by any one of the following compounds 2-1 to 2-80.

Among them, the triazine compounds represented by formulas 2-1, 2-2, 2-4, 2-5, 2-9, 2-22, and 2-24 are particularly suitable for providing excellent driving voltage characteristics, current efficiency characteristics, and This is preferable in terms of achieving both efficiency change characteristics.
[About application of triazine compound (2) to organic electroluminescent device]
The triazine compound (2) according to one embodiment of the present disclosure is used in the electron transport region. It is preferable that the electron transport region forms a laminated structure consisting of a plurality of layers, and among these, the triazine compound (2) is more preferably used in the layer that functions as the above-mentioned electron transport layer and hole blocking layer. , more preferably used in the electron transport layer.

When the triazine compound (2) is used in the electron transport layer, the electron transport layer may be formed of the triazine compound (2) alone or may be formed of a composition with other compounds. In particular, from the viewpoint of exhibiting an excellent driving voltage of the device, it is preferably formed of a composition with other compounds. In this case, the weight composition ratio of the triazine compound (2) is more preferably 20 to 80%, more preferably 30 to 80%. 70% is more preferred, and 40 to 60% is particularly preferred.

The layer formed by the composition of the triazine compound (2) and another compound may be formed by a co-evaporation method in which the triazine compound (2) and the other compound are heated and vapor-deposited simultaneously. A mixture of compound (2) and another compound may be heated and deposited. From the viewpoint of controlling the composition ratio of the triazine compound (2) in the formed layer, it is preferable to form the layer by co-evaporation.

As the compound that is deposited together with the triazine compound (2) to form the composition, the compounds shown as specific examples of the materials used for the electron transport and hole blocking layer described above or Liq are preferable, and Liq is more preferable.

Note that the triazine compound (2) according to one embodiment of the present disclosure can be synthesized by appropriately combining known reactions (for example, Suzuki-Miyaura cross-coupling reaction, etc.).

For example, the triazine compound (2) according to one embodiment of the present disclosure can be synthesized according to the production method shown in any one of reaction formulas (a) to (c) shown below, but these examples do not impose any limitations. It is not intended to be interpreted as such.

In reaction formulas (a) to (c), Ar ¹ , Ar ² and Ar ³ have the same definitions as in formula (1).

Each X independently represents a leaving group. Examples of the leaving group include, but are not limited to, a chlorine atom, a bromine atom, an iodine atom, a trifluoromethanesulfonyloxy group, and the like. Among these, bromine atom or chlorine atom is preferred from the viewpoint of good reaction yield. However, it may be preferable to use a trifluoromethanesulfonyloxy group in view of the availability of raw materials.

M each independently represents a metal-containing group ZnR ¹ , MgR ² , or Sn(R ³ ) ₃ ; or a boron-containing group B(OR ⁴ ) ₂ ; However, R ¹ and R ² each independently represent a chlorine atom, a bromine atom, or an iodine atom; R ³ represents an alkyl group having 1 to 4 carbon atoms or a phenyl group; R ⁴ represents a hydrogen atom, a carbon number Represents 1 to 4 alkyl groups or phenyl groups; two R ⁴ of B(OR ⁴ ) ₂ may be the same or different. Furthermore, two R ^4s can be combined to form a ring containing an oxygen atom and a boron atom.

Examples of ZnR ¹ and MgR ² include ZnCl, ZnBr, ZnI, MgCl, MgBr, MgI, and the like.

Examples of Sn(R ³ ) ₃ include Sn(Me) ₃ and Sn(Bu) ₃ .

Examples of B(OR ⁴ ) ₂ include B(OH) ₂ , B(OMe) ₂ , B(O ⁱ Pr) ₂ , and B(OBu) ₂ . In addition, examples of B(OR ⁴ ) ₂ in which two R ⁴ are combined to form a ring containing an oxygen atom and a boron atom include, but are not particularly limited to, the following (I) Examples include groups represented by (VI), and the group represented by (II) is preferred in terms of good yield.

The production methods shown by reaction formulas (a) to (c) will be explained in more detail by taking the production method shown by reaction formula (b) as an example. The production method shown by reaction formula (b) represents obtaining the triazine compound (2) by sequentially using an organometallic compound containing Ar ² or Ar ³ in a reaction in the presence of a palladium catalyst. The organometallic compound containing Ar ² or Ar ³ used in the reaction can be used simultaneously for the reaction, or the intermediate product obtained by the reaction using the organometallic compound containing Ar ² can be isolated once. The triazine compound (2) can also be obtained by subsequently reacting with an organometallic compound containing Ar ³ in the presence of a palladium catalyst. Alternatively, the triazine compound (2) can also be obtained by first using an organometallic compound containing Ar ³ in the reaction.
[Cathode 6]
A cathode 6 opposing the anode 2 is provided with the electron transport region 5 interposed therebetween. The cathode 6 can function as a cathode when current is passed through the organic electroluminescent element, which is one embodiment of the present disclosure.

In the case of an organic electroluminescent device having a configuration in which only light emitted from the anode 2 is extracted, the cathode 6 can be formed from any conductive material.

Materials for the cathode 6 include lithium, sodium, sodium-potassium alloy, magnesium, silver, magnesium/copper mixture, magnesium/silver mixture, magnesium/aluminum mixture, magnesium/indium mixture, aluminum/aluminum oxide (Al ₂ O ₃ ). Examples include mixtures of indium, indium-zinc oxide (IZO), lithium/aluminum mixtures, and rare earth metals such as ytterbium.

In the case of an organic electroluminescent device configured to extract light only from the cathode 6 side, a transparent electrode material such as indium zinc oxide (IZO) or a metal such as silver, aluminum, or a silver/magnesium mixture is used. An example of this is to form the material to a thickness that allows sufficient transmission of the emitted light.
[Formation method of each layer]
Each layer except for the electrodes (anode, cathode) described above is prepared by applying the material for each layer (along with materials such as binder resin and solvent as necessary) using, for example, vacuum evaporation, spin coating, casting, LB ( It can be formed by forming a thin film using a known method such as the Langmuir-Blodgett method.

The thickness of each layer formed in this way is not particularly limited and can be appropriately selected depending on the situation, but is usually in the range of 1 nm to 5 μm.

The anode 2 and the cathode 6 can be formed by forming an electrode material into a thin film 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 2 and the cathode 6 is preferably 1 μm or less, more preferably 5 nm or more and 200 nm or less. In general, when a material with low transmittance is used for the electrode on the side from which light is extracted, the transmittance can be ensured by forming a film with a thickness of 30 nm or less, and it is possible to function as a transparent electrode.

The organic electroluminescent device according to one embodiment of the present disclosure may be used as a type of lamp for illumination or as an exposure light source, or may be used as a type of projection device that projects an image, or for direct viewing of still images or moving images. It may also be used as a type of display device. When used as a display device for video playback, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. Further, by using two or more types of organic electroluminescent elements of this embodiment having different emission colors, it is possible to produce a full-color display device.

Hereinafter, the present disclosure will be explained in more detail based on Examples, but the present disclosure is not to be construed as being limited by these Examples in any way.

¹ H-NMR spectra were measured using Gemini 200 (manufactured by Varian) or Bruker ASCEND 400 (400 MHz; manufactured by BRUKER).

The luminescent properties of the organic electroluminescent device were evaluated using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse) by applying a direct current to the fabricated device at room temperature.
Synthesis example-1 (synthesis of compound 2-1)

Under argon atmosphere, 2-chloro-4,6-bis(biphenyl-4-yl)-1,3,5-triazine (11.0 g, 26.2 mmol), 5'-(5,5-dimethyl-1, 3,2-dioxaborinan-2-yl)-1,1':3',1'':2'',1'''-quaterphenyl (12.1 g, 28.8 mmol), tetrakis(triphenylphosphine) ) Palladium (0.91 g, 0.79 mmol) and 2M aqueous potassium phosphate solution (39.3 mL) were suspended in THF (349 mL) and refluxed for 3 hours. After cooling, water and methanol were added to the reaction mixture, the solid was collected by filtration, and washed with water and methanol to obtain 2-(1,1':3',1'':2'',1'''-quaterphenyl-5'-yl)-4,6-bis(biphenyl-4-yl)-1,3,5-triazine (2-1) was obtained (yield: 17.9 g, yield 99%) .
Synthesis example-2 (synthesis of compound 2-2)

Under argon atmosphere, 2-(3-bromo-5-chlorophenyl)-4,6-bis(biphenyl-4-yl)-1,3,5-triazine (5.75 g, 10.0 mmol), 2-biphenylboron Acid (4.75 g, 24.0 mmol), 3M potassium carbonate aqueous solution (16 mL), palladium acetate (22.4 mg, 0.1 mmol) and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (XPhos, 95.3 mg, 0.2 mmol) was suspended in THF (100 mL) and refluxed for 96 hours. After cooling, water and methanol were added to the reaction mixture, the solid was collected by filtration, and washed with water and methanol to obtain 2-(1,1':2',1'':3'',1''':2''',1''''-quinphenyl-5''-yl)-4,6-bis(biphenyl-4-yl)-1,3,5-triazine (2-2) was obtained. (Yield: 7.18 g, yield: 94%).
Synthesis example-3 (synthesis of compound 2-22)

Under argon atmosphere, 1,3-dibrumo-5-chlorobenzene (20.0 g, 74.0 mmol), 2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)- Biphenyl (42.5 g, 151.7 mmol), 3M aqueous potassium carbonate solution (110 mL) and tetrakistriphenylphosphine palladium (2.56 g, 2.22 mmol) were suspended in THF (245 mL) and refluxed for 122 hours. After cooling, toluene was added to the reaction mixture to separate and extract the organic layer. The obtained organic layer was distilled off under reduced pressure, and the obtained solid was recrystallized with toluene to obtain 5''-chloro-(1,1':2',1'':3'', 1''':2''',1''''-quinphenyl was obtained (yield: 29.7 g, yield 96%).

Under an argon atmosphere, 5''-chloro-(1,1':2',1'':3'',1''':2''',1''''-quinphenyl (29.7 g, 71.2 mmol), bis(neopentyl glycolate) diboron (17.7 g, 78.3 mmol), potassium acetate (0.16 g, 0.71 mmol), palladium acetate (20.9 g, 213.5 mmol) and 2-dicyclohexyl Phosphino-2',4',6'-triisopropylbiphenyl (XPhos, 0.67 mg, 1.42 mmol) was suspended in THF (356 mL) and refluxed for 27 hours.Then, the solvent was distilled off under reduced pressure and the obtained Methanol was added to the resulting residue.The resulting solid was collected by filtration and dried under reduced pressure to obtain the desired 5''-(5,5-dimethyl-1,3,2-dioxaborinan-2-yl). -1,1':2',1'':3'',1''':2''',1''''-quinphenyl was obtained (yield: 14.7 g, yield: 42).

Under argon atmosphere, 2-chloro-4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine (5.56 g, 16.2 mmol), 5''-(5,5-dimethyl- 1,3,2-dioxaborinan-2-yl)-1,1':2',1'':3'',1''':2''',1''''-quinphenyl (24. 0 g, 48.5 mmol), tetrakis(triphenylphosphine)palladium (0.56 g, 0.49 mmol), and 2M aqueous potassium phosphate solution (24.0 mL) were suspended in THF (324 mL) and refluxed for 23 hours. After cooling, water and methanol were added to the reaction mixture, and the solid was collected by filtration and washed with water and methanol. By recrystallizing the obtained solid with toluene, 2-(1,1':2',1'':3'',1''':2''',1''''-quinphenyl- 5''-yl)-4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine (2-22) was obtained (yield: 11.1 g, yield 99%).
Synthesis example-4 (synthesis of compound 2-24)

Under an argon atmosphere, 3-bromo-5-chloro-1,1':2',1''-terphenyl (g, mmol), 4-biphenylboronic acid (g, mmol), tetrakistriphenylphosphine palladium (g , mmol) and a 2M aqueous potassium phosphate solution (58.9 mL) were suspended in THF (393 mL) and refluxed for 21 hours. After cooling, the organic layer was separated and extracted, and the obtained organic layer was distilled off under reduced pressure. By adding ethanol to the obtained residue and collecting the obtained solid by filtration, the desired 5''-chloro-1,1':2',1'':3'',1''' :4''',1''''-quinphenyl was obtained (yield 24 g, yield 100%)

Under an alkone atmosphere, 5''-chloro-1,1':2',1'':3'',1''':4''',1''''-quinphenyl (23.1 g, 55 .5 mmol), bis(pinacolato)diboron (16.9 g, 66.5 mmol), potassium acetate (16.3 g, 166.4 mmol), palladium acetate (0.25 g, 1.11 mmol) and 2-dicyclohexylphosphino-2 ',4',6'-triisopropylbiphenyl (XPhos, 1.06 mg, 2.22 mmol) was suspended in THF (555 mL) and refluxed for 19 hours. Thereafter, the solvent was distilled off under reduced pressure, and methanol was added to the resulting residue. The obtained solid was collected by filtration and dried under reduced pressure to obtain the desired 5''-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,1'. :2',1'':3'',1''':4''',1''''-quinphenyl was obtained (yield 22.0 g, yield 78%)

Under argon atmosphere, 2-chloro-4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine (13.5 g, 39.3 mmol), 5''-(4,4,5, 5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,1':2',1'':3'',1''':4''',1''''- Quinphenyl (22.0 g, 43.2 mmol), tetrakis(triphenylphosphine)palladium (0.91 g, 0.79 mmol) and 2M potassium phosphate aqueous solution (58.9 mL) were suspended in THF (393 mL), It was refluxed for 21 hours. After cooling, water and methanol were added to the reaction mixture, and the solid was collected by filtration and washed with water and methanol. By recrystallizing the obtained solid with toluene, 2-(1,1':2',1'':3'',1''':4''',1''''-quinphenyl- 5''-yl)-4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazine (2-24) was obtained (21.1 g, yield 85%).

Furthermore, triazine compound 2-4 was synthesized by the same method as the production method shown in Synthesis Example-1.

The structural formulas and abbreviations of compounds used for the production and performance evaluation of organic electroluminescent devices are shown below.

Example-1 (see Figure 1)
(Preparation of substrate 1 and anode 2)
A glass substrate with an ITO transparent electrode on which a 2 mm wide indium-tin oxide (ITO) film (film thickness: 110 nm) was patterned in stripes was prepared as a substrate having an anode on its surface. Next, this substrate was cleaned with isopropyl alcohol, and then surface-treated by ozone ultraviolet cleaning.
(Preparation for vacuum deposition)
Each layer was vacuum-deposited using a vacuum evaporation method on the surface-treated substrate after cleaning, and each layer was laminated.

First, the glass substrate was introduced into a vacuum deposition tank, and the pressure was reduced to 1.0×10 ⁻⁴ Pa. Then, each layer was manufactured according to the film forming conditions in the following order.
(Preparation of first hole transport layer 31)
HTL-1 purified by sublimation and Compound 3-1 were deposited to a thickness of 10 nm at a rate of 0.15 nm/sec to produce a first hole transport layer 31.
(Preparation of second hole transport layer 32)
HTL-1 purified by sublimation was deposited to a thickness of 85 nm at a rate of 0.15 nm/sec to produce a second hole transport layer 32.
(Preparation of third hole transport layer 33)
EBL-1 purified by sublimation was deposited to a thickness of 5 nm at a rate of 0.15 nm/sec to produce a third hole transport layer 33.
(Preparation of light emitting layer 4)
BH-1 purified by sublimation and Compound 1-1, which is an embodiment of the present disclosure, were formed into a 20 nm film at a ratio of 95:5 (mass ratio) to produce a light-emitting layer 4. The film deposition rate was 0.18 nm/sec.
(Preparation of first electron transport layer 51)
HBL-1 purified by sublimation was deposited to a thickness of 6 nm at a rate of 0.05 nm/sec to produce the first electron transport layer 51.
(Preparation of second electron transport layer 52)
Compound 2-1 and Liq were formed into a 25 nm film at a ratio of 50:50 (mass ratio) to produce the second electron transport layer 52. The film deposition rate was 0.15 nm/sec.
(Preparation of third electron transport layer 53)
A 2 nm film of ytterbium was formed to form the third electron transport layer 53. The film formation rate was 0.01 nm/sec.
(Preparation of cathode 6)
Finally, a metal mask was placed so as to be perpendicular to the ITO stripes on the substrate, and the cathode 6 was formed. The cathode had a two-layer structure by forming silver/magnesium (mass ratio 9/1) and silver in this order to have a thickness of 12 nm and a thickness of 90 nm, respectively. The deposition rate of silver/magnesium was 0.5 nm/sec, and the deposition rate of silver was 0.2 nm/sec.

As described above, an organic electroluminescent device 100 having a light emitting area of 4 mm ² as shown in FIG. 1 was manufactured. The thickness of each film was measured using a stylus-type film thickness meter (DEKTAK, manufactured by Bruker).

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

A direct current was applied to the organic electroluminescent device produced as described above, and its luminescence characteristics were evaluated using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse). As the light emitting characteristics, the driving voltage (V) and current efficiency (cd/A) were measured when a voltage was applied and a luminance of 1000 cd/m ² was exhibited. Note that the driving voltage and current efficiency are relative values with the results in Comparative Example-1 described later as a reference value (100). In addition, the efficiency change was calculated based on the following definition.

Efficiency change = (current efficiency at 1000 cd/m ² o'clock) / (current efficiency at 10 cd/m ² o'clock)

The closer the value calculated by the above equation is to 1.0, the smaller the change in efficiency is in a wide luminance region.
Furthermore, after continuously driving the device manufactured as above for 50 hours at a brightness of 1000 cd/m ² , voltage was applied again and the current efficiency (cd/A) after continuous driving was measured when a brightness of 1000 cd/m ² was obtained. did. Furthermore, the change in efficiency after continuous driving was calculated based on the following definition.

Efficiency change after continuous driving =
(Current efficiency after continuous driving at 1000 cd/m ² o'clock) / (Current efficiency at 1000 cd/m ² o'clock)

The closer the value calculated by the above equation is to 1.0, the smaller the change in the efficiency of the element before and after continuous driving.

The measurement results obtained are shown in Table 1.
Example-2
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that Compound 2-2 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Example-3
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that Compound 2-22 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Example-4
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that Compound 2-24 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Example-5
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that Compound 2-4 was used instead of Compound 2-1. Comparative example-1 whose measurement results are shown in Table 1
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that ETL-1 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Comparative example-2
An organic electroluminescent device was produced in the same manner as Example 1, except that BD-1 was used instead of Compound 1-1 and Compound 2-4 was used instead of Compound 2-1 in Device Example 1. ,evaluated. The measurement results obtained are shown in Table 1.
Comparative example-3
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that ETL-2 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Comparative example-4
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that ETL-3 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Comparative example-5
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that ETL-4 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Comparative example-6
In Device Example 1, an organic electroluminescent device was produced and evaluated in the same manner as in Example 1, except that ETL-5 was used instead of Compound 2-1. The measurement results obtained are shown in Table 1.
Comparative example-7
In device example 1, an organic electroluminescent device was produced and evaluated in the same manner as in example 1, except that ETL-6 was used instead of compound 2-1. The measurement results obtained are shown in Table 1.
Comparative example-8
An organic electroluminescent device was produced in the same manner as Example 1, except that BD-1 was used instead of Compound 1-1 and Compound 2-24 was used instead of Compound 2-1. ,evaluated. The measurement results obtained are shown in Table 1.

From Table 1, the configuration in which the light-emitting layer according to one embodiment of the present disclosure contains the boron compound represented by the above formula (1), and the electron transport region contains the triazine compound represented by the above formula (2) is conventional. It is possible to provide an organic electroluminescent device that not only has superior drive voltage characteristics and current efficiency characteristics compared to known configurations, but also has small efficiency changes and small efficiency changes after continuous driving.

1 Substrate 2 Anode 3 Hole transport region 31 First hole transport layer 32 Second hole transport layer 33 Third hole transport layer 4 Light emitting layer 5 Electron transport region 51 First electron transport layer 52 Second electron transport layer 53 Third electron transport layer 6 Cathode 100 Organic electroluminescent device

Claims (9)

an anode;
a cathode facing the anode;
a light emitting layer disposed between the anode and the cathode;
an electron transport region disposed between the light emitting layer and the cathode;
The light emitting layer contains a boron compound represented by formula (1),
An organic electroluminescent device in which the electron transport region contains a triazine compound represented by formula (2).
In formula (1),
Ring A, Ring B, and Ring C may each independently have a substituent,
aromatic hydrocarbon ring having 6 to 20 ring atoms;
or represents an aromatic heterocycle having 5 to 20 ring atoms;
Ra, Rb, and Rc are each independently,
deuterium,
cyano group,
an alkyl group having 1 to 20 carbon atoms,
an optionally substituted amino group,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or a heteroaromatic group having 5 to 20 ring atoms; a, b, and c are each independently an integer of 0 to 4;
Ring A and ring B may be connected via an oxygen atom, a sulfur atom, NR', Ra or Rb,
R ¹ , R ² , R' may each independently have a substituent,
an alkyl group having 1 to 20 carbon atoms,
aromatic hydrocarbon group having 6 to 20 ring atoms;
or represents a heteroaromatic group having 5 to 20 ring atoms;
R ¹ may be linked to ring A or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Ra, or Rc to form a ring structure,
R ² may be linked to ring B or ring C via an oxygen atom, a sulfur atom, an optionally substituted nitrogen atom, Rb, or Rc to form a ring structure.
In formula (2),
Ar ¹ represents a phenyl group, a naphthyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 6 carbon atoms;
Ar ² represents a phenyl group, a pyridyl group, a phenylpyridyl group, a pyridylphenyl group, or a biphenylyl group, which may be substituted with an alkyl group having 1 to 4 carbon atoms.
Ar ³ represents a phenyl group or a biphenylyl group which may be substituted with an alkyl group having 1 to 4 carbon atoms. The organic electroluminescent device according to claim 1, wherein in formula (1), at least one of rings A to C is a benzene ring which may have a substituent. 3. The organic electroluminescent device according to claim 1, wherein in formula (1), rings A to C are rings containing a benzene structure which may have a substituent. The organic electroluminescent device according to claim 1 or 2, wherein in formula (1), at least one of Ra, Rb, and Rc is an alkyl group having 1 to 4 carbon atoms. The organic electroluminescent device according to claim 1 or 2, wherein the boron compound represented by formula (1) is selected from the following.
The organic electroluminescent device according to claim 5, wherein the boron compound represented by formula (1) is the compound 1-1. The electron transport region includes a first electron transport layer;
at least a second electron transport layer disposed between the first electron transport layer and the cathode,
The organic electroluminescent device according to claim 1 or 2, wherein the second electron transport layer contains a triazine compound represented by formula (2). The organic electroluminescent device according to claim 1 or 2, wherein the triazine compound represented by formula (2) is as follows.
The organic electroluminescent device according to claim 7, wherein the second electron transport layer contains a compound represented by formula (2) and lithium quinolate (Liq).