JP7494511B2 - Cyclic azine compound, material for organic electroluminescent device, electron transport material for organic electroluminescent device, and organic electroluminescent device - Google Patents

Description

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

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

International Publication No. 2017/150930

However, in recent years, market demands for organic electroluminescent devices have become increasingly high, and materials that are excellent in all respects of current efficiency characteristics, driving voltage characteristics, and long life characteristics are being sought.
Here, the organic electroluminescent device using the cyclic azine compound disclosed in Patent Document 1 is required to have further improvements in drive voltage characteristics and current efficiency.

One aspect of the present invention is directed to providing a cyclic azine compound, a material for an organic electroluminescent device, and an electron transport material for an organic electroluminescent device, which are useful for producing an organic electroluminescent device having excellent driving voltage characteristics and current efficiency.
Another aspect of the present invention is to provide an organic electroluminescent device having excellent driving voltage characteristics and current efficiency.

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

In formula (1),
Ar ¹ and Ar ² each independently represent
a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, or
These groups are
an alkyl group having 1 to 12 carbon atoms,
a cycloalkyl group having 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 groups,
A cyano group, and
a diarylphosphine oxide group;
^B1 to ^B3 are
any one of them forms a single bond together with any one of R ¹ to R ⁵ in formula (2);
The remaining two each represent a hydrogen atom;

In formula (2),
R ¹ to R ⁵ are
any one of B ¹ to B 3 forms a single bond together with any one of B 1 to B ³ ;
The remaining four each independently represent a hydrogen atom, a methyl group, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-(2-pyridyl)phenyl group, a 2-(3-pyridyl)phenyl group, a 2-(4-pyridyl)phenyl group, a 3-(2-pyridyl)phenyl group, a 3-(3-pyridyl)phenyl group, a 3-(4-pyridyl)phenyl group, a 4-(2-pyridyl)phenyl group, a 4-(3-pyridyl)phenyl group, or a 4-(4-pyridyl)phenyl group.

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

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, which are useful for producing an organic electroluminescent element having excellent driving voltage characteristics and current efficiency.
According to another aspect of the present invention, it is possible to provide an organic electroluminescent device having excellent driving voltage characteristics and current efficiency.

FIG. 1 is a schematic cross-sectional view showing an example of a layered structure of an organic electroluminescent device containing a cyclic azine compound according to one embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing an example of a layered structure of an organic electroluminescent element containing a cyclic azine compound according to one embodiment of the present invention (Element Example 1).

The cyclic azine compound according to one embodiment of the present invention is described in detail below.

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

In formula (1),
Ar ¹ and Ar ² each independently represent
a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, or
These groups are
an alkyl group having 1 to 12 carbon atoms,
a cycloalkyl group having 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 groups,
A cyano group, and
a diarylphosphine oxide group;
^B1 to ^B3 are
any one of them forms a single bond together with any one of R ¹ to R ⁵ in formula (2);
The remaining two each represent a hydrogen atom;

In formula (2),
R ¹ to R ⁵ are
any one of B ¹ to B 3 forms a single bond together with any one of B 1 to B ³ ;
The remaining four each independently represent a hydrogen atom, a methyl group, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-(2-pyridyl)phenyl group, a 2-(3-pyridyl)phenyl group, a 2-(4-pyridyl)phenyl group, a 3-(2-pyridyl)phenyl group, a 3-(3-pyridyl)phenyl group, a 3-(4-pyridyl)phenyl group, a 4-(2-pyridyl)phenyl group, a 4-(3-pyridyl)phenyl group, or a 4-(4-pyridyl)phenyl group.

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

Ar ¹ and Ar ² each independently represent
a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, or
These groups are
an alkyl group having 1 to 12 carbon atoms,
a cycloalkyl group having 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 groups,
A cyano group, and
and diarylphosphine oxide groups.
Ar ¹ and Ar ² each independently represent one of the following in terms of excellent electron transporting material properties:
an unsubstituted phenyl group, or
It is preferably a phenyl group substituted with 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.

The alkyl group having 1 to 12 carbon atoms which may substitute for the phenyl group, 1-naphthyl group, or 2-naphthyl group in Ar ¹ and Ar ² may be either linear or branched. That is, it is a linear alkyl group having 1 to 12 carbon atoms, or a branched alkyl group having 3 to 12 carbon atoms. It is preferably a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 3 to 4 carbon atoms. Preferable 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 substitute for the phenyl group, 1-naphthyl group, or 2-naphthyl group in Ar ¹ and Ar ² include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, an adamantyl group, and a diamantyl group.

Specific examples of the aryl group having 1 to 20 carbon atoms, which may be substituted with an alkyl group having 1 to 12 carbon atoms or a cyano group, in Ar ¹ and Ar ² , which may be substituted with a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, include a phenyl group, a biphenylyl group, a naphthyl group, an anthracenyl group, a phenanthryl group, a fluorenyl group, and 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 preferably a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 to 4 carbon atoms. Specific examples of the linear alkyl group having 1 to 4 carbon atoms or the branched alkyl group having 3 to 4 carbon atoms 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.

The diarylboryl which may substitute the phenyl group, 1-naphthyl group, or 2-naphthyl group in Ar ¹ and Ar ² includes dimesitylboryl.

The diarylphosphine oxide which may substitute the phenyl group, 1-naphthyl group, or 2-naphthyl group in Ar ¹ and Ar ² includes diphenylphosphine oxide.

B ¹ to B ³ each independently form a hydrogen atom or a single bond together with R ¹ to R ⁵ in formula (2), and any one of B ¹ to B ³ forms a single bond together with R ¹ to R ⁵ in formula (2).

In formula (2), R ¹ to R ⁵ are
any one of them forms a single bond together with any one of B ¹ to B ³ in formula (1);
The remaining four each independently represent a hydrogen atom, a methyl group, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-(2-pyridyl)phenyl group, a 2-(3-pyridyl)phenyl group, a 2-(4-pyridyl)phenyl group, a 3-(2-pyridyl)phenyl group, a 3-(3-pyridyl)phenyl group, a 3-(4-pyridyl)phenyl group, a 4-(2-pyridyl)phenyl group, a 4-(3-pyridyl)phenyl group, or a 4-(4-pyridyl)phenyl group.

R ¹ to R ⁵ are
any one of B ¹ to B 3 forms a single bond together with any one of B 1 to B ³ ;
The remaining four are preferably each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group.

A first aspect of R ¹ to R ⁵ is
any one of them forms a single bond together with ^B1 ;
The remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group.

A second aspect of R ¹ to R ⁵ is
one of them forms a single bond with ^B2 ,
The remaining four are each independently a hydrogen atom, a methyl group, a phenyl group, or a 4-biphenyl group.

A third aspect of R ¹ to R ⁵ is
any one of them forms a single bond together with ^B3 ;
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 formula (2) include the following (2-1) to (2-33).

[Specific examples of cyclic azine compound (1)]
Among the cyclic azine compounds according to one embodiment of the present invention represented by formula (1), specific examples of particularly preferred compounds include the following (1-1) to (1-40), but the cyclic azine compounds according to one embodiment of the present invention are not limited thereto.

The uses of the cyclic azine compound (1) will be described below.
<Material for organic electroluminescence device, electron transport material for organic electroluminescence device>
The cyclic azine compound (1) can be used, for example, as a material for an organic electroluminescent device, although it is not particularly limited thereto. The cyclic azine compound (1) can also be used, for example, as an electron transport material for an organic electroluminescent device.
That is, the material for organic electroluminescence elements according to one embodiment of the present invention contains the cyclic azine compound (1). Also, the electron transport material for organic electroluminescence elements according to one embodiment of the present invention contains the cyclic azine compound (1). The material for organic electroluminescence elements and the electron transport material for organic electroluminescence elements containing the cyclic azine compound (1) contribute to the production of organic electroluminescence elements having excellent driving 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 structure of the organic electroluminescent device is not particularly limited, but examples thereof include the following structures (i) to (vi).
(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-generating layer/hole-transport layer/light-emitting layer/electron-transport layer/cathode

Hereinafter, an organic electroluminescence device according to one embodiment of the present invention will be described in more detail by taking the above-mentioned configuration (vi) as an example with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of a layered configuration of an organic electroluminescence device containing a cyclic azine compound according to one embodiment of the present invention.
1 has a so-called bottom-emission type element configuration, the organic electroluminescence element according to one embodiment of the present invention is not limited to the bottom-emission type element configuration. That is, the organic electroluminescence element according to one embodiment of the present invention may have a top-emission type element configuration or another known element 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, or other layers may be added. For example, an electron injection layer may be provided between the electron transport layer 7 and the cathode 8, or the charge generation layer 4 may be omitted and the hole transport layer 5 may be provided directly on the hole injection layer 3. In addition, a single layer having the functions of multiple layers, such as an electron injection/transport layer having the functions of both the electron injection layer and the electron transport layer in a single layer, may be provided instead of the multiple layers. Furthermore, for example, the single-layer hole transport layer 5 and the single-layer electron transport layer 7 may each be made up of multiple layers.

[Layer containing a cyclic azine compound represented by formula (1)]
The organic electroluminescent device contains the cyclic azine compound represented by the above formula (1) in one or more layers selected from the group consisting of the light-emitting layer and the layer between the light-emitting layer and the cathode. Thus, 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 provided in the organic electroluminescent device, and when an electron injection layer is provided between the electron transport layer and the cathode, the electron injection layer may contain the cyclic azine compound (1).
In the following, an organic electroluminescent device 100 in which the electron transport layer 7 contains the cyclic azine compound (1) will be described.

[Substrate 1]
There is no particular limitation on the substrate, and examples thereof include a glass plate, a quartz plate, a plastic plate, etc. In addition, in the case of a configuration in which light emission is extracted from the substrate 1 side, the substrate 1 is transparent to the wavelength of light.

Examples of light-transmitting plastic films include films made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate (CAP), etc.

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

The transparent material used for the anode is not particularly limited, but examples thereof include indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide, aluminum-doped tin oxide, magnesium-indium oxide, nickel-tungsten oxide, other metal oxides, metal nitrides such as gallium nitride, metal selenides such as zinc selenide, and metal sulfides such as zinc sulfide.
In the case of an organic electroluminescent device in which light is extracted only from the cathode side, the transmittance characteristics of the anode are not important. Therefore, examples of materials used for the anode in this case include gold, iridium, molybdenum, palladium, platinum, etc.
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 a light-emitting layer 6 described later, a hole injection layer 3, a charge generation 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 the function of transporting holes injected from the anode to the light-emitting layer. By interposing this hole injection layer and hole transport layer between the anode and the light-emitting layer, a large number of holes can be injected into the light-emitting layer with 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 injection layer and/or the electron transport layer to the light-emitting layer are prevented from leaking to the hole injection layer and/or the hole transport layer due to the electron barrier present at the interface between the light-emitting layer and the hole injection layer and/or the hole transport layer. As a result, the electrons are accumulated at the interface within the light-emitting layer, which brings about effects such as improved current efficiency, and an organic electroluminescent element with excellent light-emitting performance is obtained.

The material for 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 for the hole injection layer and the hole transport layer may be either organic or inorganic.

Specific examples of materials for the hole injection layer and hole transport layer include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline-based copolymers, conductive polymer oligomers (particularly thiophene oligomers), porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds. Among these, porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds are preferred, and aromatic tertiary amine compounds are particularly preferred.

Specific examples of aromatic tertiary amine compounds and styrylamine compounds 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-tolylaminophenyl)phenylmethane, N,N'-diphenyl-N,N'- Examples of the di(4-methoxyphenyl)-4,4'-diaminobiphenyl include N,N,N',N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'-bis(diphenylamino)quadriphenyl, N,N,N-tri(p-tolyl)amine, 4-(di-p-tolylamino)-4'-[4-(di-p-tolylamino)styryl]stilbene, 4-N,N-diphenylamino-(2-diphenylvinyl)benzene, 3-methoxy-4'-N,N-diphenylaminostilbene, N-phenylcarbazole, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD), and 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MTDATA).
Furthermore, inorganic compounds such as p-type Si and p-type SiC can also be given as examples of materials for the hole injection layer and the hole transport layer.

The hole injection layer and the hole transport layer may be a single layer structure made of one or more materials, or a laminate structure made of multiple layers of the same or different compositions.

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

[Light-emitting layer 6]
The light-emitting layer 6 is provided between the hole transport layer 5 and the electron transport layer 7 described below.
The material of the light-emitting layer includes a phosphorescent material, a fluorescent material, and a thermally activated delayed fluorescent material. In the light-emitting layer, electron-hole pairs are recombined, resulting in light emission.

The light-emitting layer may consist of a single small molecule material or a single polymeric material, but more commonly consists of a host material doped with a guest compound. Emission comes primarily from the dopant and can be of any color.

Examples of host materials include compounds having a biphenyl group, a fluorenyl group, a triphenylsilyl group, a carbazole group, a pyrenyl group, and an anthryl group. More specifically, examples of the compound include DPVBi (4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl), BCzVBi (4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl), TBADN (2-tertiarybutyl-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, and the like.

Examples of fluorescent dopants include anthracene, pyrene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine, quinacridone, dicyanomethylenepyran compounds, thiopyran compounds, polymethine compounds, pyrylium, thiapyrylium compounds, fluorene derivatives, periflanthene derivatives, indenoperylene derivatives, bis(azinyl)amine boron compounds, bis(azinyl)methane compounds, carbostyril compounds, and the like. The fluorescent dopant may be a combination of two or more selected from these.

Examples of phosphorescent dopants include organometallic complexes of transition metals such as iridium, platinum, palladium, and osmium.

Specific examples of fluorescent and phosphorescent dopants include Alq3 (tris(8-hydroxyquinoline)aluminum), DPAVBi (4,4'-bis[4-(di-p-tolylamino)styryl]biphenyl), perylene, 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))).

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

The light-emitting layer may be a single layer structure made of one or more materials, or a laminate structure made of multiple layers of the same or different compositions.

[Electron transport layer 7]
An electron transport layer 7 is provided between the light emitting layer 6 and a cathode 8 which will be described later.
The electron transport layer has a function of transporting 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 at a lower electric field.

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

In addition to the cyclic azine compound (1), the electron transport layer may further contain a conventionally known electron transport material. Examples of conventionally known electron transport materials include 8-hydroxyquinolinato lithium (Liq), bis(8-hydroxyquinolinato) zinc, bis(8-hydroxyquinolinato) copper, bis(8-hydroxyquinolinato) manganese, tris(8-hydroxyquinolinato) aluminum, tris(2-methyl-8-hydroxyquinolinato) aluminum, tris(8-hydroxyquinolinato) gallium, bis(10-hydroxybenzo[h]quinolinato) beryllium, bis(10-hydroxybenzo[h]quinolinato) zinc, bis(2-methyl-8-quinolinato) chlorogallium, bis(2-methyl-8-quinolinato) (o-cresolate) gallium, and bis(2-methyl-8-quinolinato)-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-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-quinolinate)-4-(phenylphenolate)aluminum), and bis(10-hydroxybenzo[h]quinolinate)beryllium).

The electron transport layer may have a single layer structure made of one or more materials, or a laminate structure made of multiple layers of the same or different compositions.
When the electron transport layer has a two-layer structure in which a first electron transport layer is on the light emitting layer side and a second electron transport layer is on the cathode side, it is preferable that the second electron transport layer contains a cyclic azine compound (1).

[Cathode 8]
A cathode 8 is provided on the electron transport layer 7 .
In the case of an organic electroluminescence element having a configuration in which only light emitted through the anode is extracted, the cathode can be formed from any conductive material.
Cathode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium/copper mixtures, magnesium/silver mixtures, magnesium/aluminum mixtures, magnesium/indium mixtures, aluminum/aluminum oxide (Al ₂ O ₃ ) mixtures, indium, lithium/aluminum mixtures, rare earth metals, and the like.
A buffer layer (electrode interface layer) may be provided on the cathode (on the electron transport layer side).

[Method of forming each layer]
Each layer except for the electrodes (anode and cathode) described above can be formed by forming a thin film from the material of each layer (together with a material such as a binder resin and a solvent, if necessary) by a known method such as a vacuum deposition method, a spin coating method, a casting method, or a Langmuir-Blodgett method (LB method).
There is no particular limitation on the thickness of each layer thus formed, and it can be appropriately selected depending on the circumstances, but it is usually in the range of 5 nm to 5 μm.

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

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

The organic electroluminescent device according to one embodiment of the present invention may be used as a type of lamp for illumination or exposure light source, or as a projection device for projecting images, or as a display device for directly viewing still images or moving images. When used as a display device for playing moving images, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. In addition, by using two or more types of organic electroluminescent devices according to this embodiment having different emission colors, it is possible to produce a full-color display device.

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

The present invention will be described in more detail below with reference to examples, but the present invention should not be construed as being limited in any way by these examples.

¹ H-NMR measurements were carried out using Gemini 200 (Varian).
The glass transition temperature was measured using a DSC7020 (manufactured by Hitachi High-Tech Science Corporation).
The light emitting characteristics of the organic electroluminescent device were evaluated by applying a direct current to the prepared device at room temperature using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse).

Synthesis Example 1 Synthesis of Compound (1-5)

Under a nitrogen stream, 2-[1,1'-biphenyl]-4-yl-4-[4'-chloro(1,1'-biphenyl)-4-yl]-6-phenylpyridine (2.00 g, 4.05 mmol), 2,4-diphenyl-6-[3-(4,4,5,5-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) were dissolved in tetrahydrofuran (40 mL). To this was added 2M potassium phosphate aqueous solution (6 mL, 12.1 mmol), and the mixture was stirred at 70°C for 18 hours. The mixture was allowed to cool to room temperature, water was added to the suspension, and the mixture was stirred at room temperature, after which the solid was collected by suction filtration. The obtained solid was washed with water and then with ethanol. This solid was dissolved in toluene (600 mL), activated carbon was added, and the mixture was stirred. The mixture was then filtered through Celite and the solvent was distilled off under reduced pressure. The obtained solid was recrystallized from chlorobenzene (150 ml) to obtain a white solid of compound (1-5) (yield: 2.0 g, 64%).

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) were dissolved in tetrahydrofuran (145 mL). To this was added 2M potassium phosphate aqueous solution (22 mL, 43.6 mmol), and the mixture was stirred at 70°C for 24 hours. The mixture was allowed to cool to room temperature, water was added to the suspension, and the mixture was stirred at room temperature, after which the solid was collected by suction filtration. The obtained solid was washed with water and then with ethanol. This solid was dissolved in chlorobenzene (400 mL), activated carbon was added, and the mixture was stirred. The mixture was then filtered through Celite and the solvent was distilled off under reduced pressure. The resulting solid was washed with toluene (600 ml) heated to reflux temperature to obtain a white solid of compound (1-9) (yield: 8.1 g, 64%).

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

Then, the obtained compound was used to carry out element evaluation.

Element Example 1 (see FIG. 2)
(Preparation of Substrate 101 and Anode 102)
A glass substrate with an indium-tin oxide (ITO) transparent electrode, on which a 2 mm wide ITO film (thickness: 110 nm) was patterned in stripes, was prepared as a substrate having an anode on its surface. The substrate was then washed with isopropyl alcohol and then subjected to surface treatment by ozone ultraviolet cleaning.

(Preparation for vacuum deposition)
After cleaning and surface treatment, each layer was deposited by vacuum deposition on the substrate by vacuum deposition, forming a laminate of each layer.
First, the glass substrate was placed in a vacuum deposition chamber, and the pressure was reduced to 1.0×10 ⁻⁴ Pa. Then, each layer was prepared according to the film formation conditions in the following order.

(Fabrication of Hole Injection Layer 103)
Sublimation purified N-[1,1'-biphenyl]-4-yl-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine and 1,2,3-tris[(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropane were formed into a film of 10 nm at a rate of 0.15 nm/sec to prepare hole injection layer 103.

(Preparation of First Hole Transport Layer 1051)
Sublimation purified N-[1,1′-biphenyl]-4-yl-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine was formed into a film of 85 nm at a rate of 0.15 nm/sec to prepare a first hole transport layer 1051 .

(Preparation of second hole transport layer 1052)
Sublimation-purified N-phenyl-N-(9,9-diphenylfluoren-2-yl)-N-(1,1′-biphenyl-4-yl)amine was formed into a film having a thickness of 5 nm at a rate of 0.15 nm/sec to prepare a second hole transport layer 1052 .

(Fabrication of Light-Emitting Layer 106)
Sublimation-purified 3-(10-phenyl-9-anthryl)-dibenzofuran and 2,7-bis[N,N-di-(4-tertbutylphenyl)]amino-bisbenzofurano-9,9′-spirofluorene were mixed in a ratio of 95:5 (mass ratio) to form a film of 20 nm, thereby producing the light-emitting layer 106. The film formation rate was 0.18 nm/sec.

(Preparation of First Electron Transport Layer 1071)
Sublimation-purified 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)[1,1′-biphenyl]-3-yl]-4,6-diphenyl-1,3,5-triazine was formed into a film having a thickness of 6 nm at a rate of 0.05 nm/sec to form a first electron transport layer 1071 .

(Preparation of second electron transport layer 1072)
The compound (1-5) synthesized in Synthesis Example-1 and Liq were mixed in a ratio of 50:50 (mass ratio) to form a film having a thickness of 25 nm, thereby preparing a second electron transport layer 1072. The film formation rate was 0.15 nm/sec.

(Fabrication of cathode 108)
Finally, a metal mask was placed perpendicular to the ITO stripes on the substrate, and the cathode 108 was formed. The cathode had a two-layer structure in which silver/magnesium (mass ratio 1/10) and silver were formed in this order to thicknesses of 80 nm and 20 nm, respectively. The silver/magnesium film formation rate was 0.5 nm/sec, and the silver film formation rate was 0.2 nm/sec.

In this manner, an organic electroluminescent device 100 having a light-emitting area of 4 ^mm2 was produced as shown in Fig. 2. The thickness of each film was measured using a stylus film thickness gauge (DEKTAK, manufactured by Bruker).

The device was then sealed in a nitrogen atmosphere glove box with oxygen and moisture concentrations of 1 ppm or less. The glass sealing cap and the film-formed substrate (device) were sealed using bisphenol F epoxy resin (manufactured by Nagase ChemteX Corporation).

A direct current was applied to the organic electroluminescent device prepared as described above, and the light emission characteristics were evaluated using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse). As the light emission characteristics, the current efficiency (cd/A) when a current density of 10 mA/ ^cm2 was applied was measured, and the element life (h) during continuous lighting was measured. The driving voltage and current efficiency are relative values with the result in the below-described element reference example 1 taken as the reference value (100). The obtained measurement results are shown in Table 1.

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

Element Reference Example 1
An organic electroluminescent device was produced and evaluated in the same manner as in Element Example-1, except that the compound (ETL-1) described in Patent Document 1 (WO 2017/150930) was used instead of the compound (1-5) in Element Example-1. The obtained measurement results are shown in Table 1.

The cyclic azine compound (1) according to one embodiment of the present invention has a wide band gap and a high triplet excitation level, and therefore can be suitably used not only in conventional fluorescent device applications, but also in phosphorescent devices and organic electroluminescent devices using thermally activated delayed fluorescence (TADF).

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 device

Claims (9)

A cyclic azine compound represented by formula (1):

In formula (1),
Ar ¹ and Ar ² each independently represent
a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, or
These groups are
an alkyl group having 1 to 12 carbon atoms,
a cycloalkyl group having 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 groups,
A cyano group, and
a diarylphosphine oxide group;
^B1 to ^B3 are
any one of them forms a single bond together with any one of R ¹ to R ⁵ in formula (2);
The remaining two each represent a hydrogen atom;

In formula (2),
R ¹ to R ⁵ are
any one of B ¹ to B 3 forms a single bond together with any one of B 1 to B ³ ;
The remaining four each independently represent a hydrogen atom, a methyl group, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-(2-pyridyl)phenyl group, a 2-(3-pyridyl)phenyl group, a 2-(4-pyridyl)phenyl group, a 3-(2-pyridyl)phenyl group, a 3-(3-pyridyl)phenyl group, a 3-(4-pyridyl)phenyl group, a 4-(2-pyridyl)phenyl group, a 4-(3-pyridyl)phenyl group, or a 4-(4-pyridyl)phenyl group. Ar ¹ and Ar ² each independently represent
a phenyl group, or
2. The cyclic azine compound according to claim 1, which is a phenyl group substituted with 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. R ¹ to R ⁵ are
any one of B ¹ to B 3 forms a single bond together with any one of B 1 to B ³ ;
3. The cyclic azine compound according to claim 1, 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 of them forms a single bond together with ^B1 ;
3. The cyclic azine compound according to claim 1, 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 of them forms a single bond with ^B2 ,
3. The cyclic azine compound according to claim 1, 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 of them forms a single bond together with ^B3 ;
3. The cyclic azine compound according to claim 1, 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 comprising the cyclic azine compound according to any one of claims 1 to 6. An electron transport material for organic electroluminescent devices comprising the cyclic azine compound according to any one of claims 1 to 6. An organic electroluminescent device comprising the cyclic azine compound according to any one of claims 1 to 6.

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