JP7826766B2 - 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 an 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 other applications, and their development is being actively pursued.
In recent years, market demands for organic electroluminescent devices have become increasingly high, and materials that are excellent in current efficiency, driving voltage, and long life are being sought.
Here, Patent Document 1 discloses azine compounds substituted with different substituents at the 2-, 4-, and 6-positions.

Special Publication No. 2019-512499

However, organic electroluminescent devices using the compound disclosed in Patent Document 1 in the electron transport layer have insufficient characteristics in terms of driving voltage, luminous efficiency, and driving life, and further improvements are required.

One aspect of the present invention is to provide an azine compound having high solubility, a material for an organic electroluminescent device, and an electron-transporting material for an organic electroluminescent device, which are useful for producing an organic electroluminescent device having a low driving voltage and excellent luminous efficiency and life characteristics.
Another aspect of the present invention is to provide an organic electroluminescent device that has a low driving voltage and excellent luminous efficiency and life characteristics.

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

In formula (1),
A represents any one group selected from formulas (A-1) to (A-18):

B represents a phenyl group;
^Ar1 is
represents a phenyl group or a biphenylyl group which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group;
^Ar2 is
an aryl group having 6 to 30 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group, or
It represents a pyridyl group which may be substituted with one or more groups selected from the group consisting of a methyl group and a phenyl group.

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

According to one aspect of the present invention, it is possible to provide an azine compound, a material for an organic electroluminescent element, and an electron-transporting material for an organic electroluminescent element, which contribute to the production of an organic electroluminescent element having a low driving voltage and excellent luminous efficiency and life characteristics, and which has high solubility and can be easily subjected to extraction and purification procedures after synthesis.
According to another aspect of the present invention, it is possible to provide an organic electroluminescent device that has a low driving voltage and excellent luminous efficiency and life characteristics.

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

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

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

In formula (1),
A represents any one group selected from formulas (A-1) to (A-18):

B represents a phenyl group;
^Ar1 is
represents a phenyl group or a biphenylyl group which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group;
^Ar2 is
an aryl group having 6 to 30 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group, or
It represents a pyridyl group which may be substituted with one or more groups selected from the group consisting of a methyl group and a phenyl group.

[Regarding A and B]
In formula (1),
A represents any one group selected from formulas (A-1) to (A-18):

B represents a phenyl group.

A represents any one group selected from formulas (A-1) to (A-18), and preferably any one group selected from formulas (A-1) to (A-8).

[Regarding Ar ¹ and Ar ² ]
^Ar1 is
represents a phenyl group or a biphenylyl group which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group;
Ar ¹ is more preferably an unsubstituted phenyl group, a 2-biphenylyl group, a 3-biphenylyl group, or a 4-biphenylyl group.
^Ar2 is
an aryl group having 6 to 30 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group, or
It represents a pyridyl group which may be substituted with one or more groups selected from the group consisting of a methyl group and a phenyl group.

Ar ² is a phenyl group, a 1-naphthalenyl group, a 2-naphthalenyl group, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group, a 2-(1-naphthalenyl)phenyl group, a 3-(1-naphthalenyl)phenyl group, a 4-(1-naphthalenyl)phenyl group, a 2-( Ar 2 is preferably an unsubstituted phenyl group, a 1-naphthalenyl group, a 2-naphthalenyl group, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group, or a ⁹ -phenanthrenyl group, and particularly preferably an unsubstituted phenyl group, a 2-naphthalenyl group, a 2-biphenylyl group, a 4-biphenylyl group, or a 9-phenanthrenyl group.

[Preferable combinations of A and ^Ar2 ]
A represents any one group selected from formulas (A-1) to (A-8),
It is preferable that ^Ar2 represents an aryl group having 6 to 30 carbon atoms which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group.
A represents any one group selected from formulas (A-2) to (A-6),
Ar ² is more preferably an unsubstituted phenyl group, a 1-naphthalenyl group, a 2-naphthalenyl group, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group, or a 9-phenanthrenyl group;
A represents any one group selected from formulas (A-2) to (A-6),
It is particularly preferred that Ar ² is an unsubstituted phenyl group, a 2-naphthalenyl group, a 2-biphenylyl group, a 4-biphenylyl group, or a 9-phenanthrenyl group.

[Specific examples of azine compound (1)]
Among the azine compounds represented by formula (1) according to one embodiment of the present invention, particularly preferred specific examples include those represented by the following formulas (1-1) to (1-96); however, the azine compounds according to one embodiment of the present invention are not limited thereto.

Of the compounds represented by formulas (1-1) to (1-96), compounds represented by formulas (1-3), (1-15), (1-27), (1-39), and (1-94) are particularly preferred.

The uses of the azine compound (1) will be described below.
<Material for organic electroluminescent device, electron transport material for organic electroluminescent device>
Although not particularly limited, the azine compound (1) can be used, for example, as a material for an organic electroluminescent device, and the azine compound (1) can be used, for example, as an electron transport material for an organic electroluminescent device.
That is, a material for organic electroluminescent elements according to one aspect of the present invention contains azine compound (1). Also, an electron-transporting material for organic electroluminescent elements according to one aspect of the present invention contains azine compound (1). The material for organic electroluminescent elements and the electron-transporting material for organic electroluminescent elements containing azine compound (1) contribute to the production of organic electroluminescent elements excellent in driving voltage, luminous efficiency, and life characteristics.

<Organic electroluminescent device>
The organic electroluminescent device according to one aspect of the present invention contains an azine compound (1).
The configuration of the organic electroluminescent device is not particularly limited, but examples thereof include the following configurations (i) to (vi).
(i): anode/light-emitting layer/cathode (ii): anode/hole-transporting layer/light-emitting layer/cathode (iii): anode/light-emitting layer/electron-transporting layer/cathode (iv): anode/hole-transporting layer/light-emitting layer/electron-transporting layer/cathode (v): anode/hole-injection layer/hole-transporting layer/light-emitting layer/electron-transporting layer/electron-injection layer/cathode (vi): anode/hole-injection layer/charge-generating layer/hole-transporting layer/light-emitting layer/electron-transporting layer/cathode

An organic electroluminescent device according to one embodiment of the present invention will be described in more detail below, taking the above-mentioned structure (vi) as an example, with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the layer structure of an organic electroluminescent device containing an 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 any other known element configuration.

The organic electroluminescent device 100 comprises, in this order, a substrate 1, an anode 2, a hole injection layer 3, a charge generation layer 4, a hole transport layer 5, an emissive layer 6, an electron transport layer 7, and a cathode 8. 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. Alternatively, a single layer that combines the functions of multiple layers, such as an electron injection/transport layer that combines the functions of both an electron injection layer and an electron transport 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 composed of multiple layers.

[Layer containing an azine compound represented by formula (1)]
An organic electroluminescent device contains the azine compound represented by formula (1) in one or more layers selected from the group consisting of an emitting layer and a layer between the emitting layer and a cathode. Accordingly, in the exemplary configuration shown in FIG. 1 , the organic electroluminescent device 100 contains the azine compound (1) in at least one layer selected from the group consisting of the emitting layer 6 and the electron transport layer 7. It is particularly preferred that the electron transport layer 7 contains the azine compound (1). The azine compound (1) may be contained in multiple layers of 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 azine compound (1).
In the following, an organic electroluminescent device 100 in which the electron transport layer 7 contains the azine compound (1) will be described.

[Substrate 1]
There are no particular limitations on the substrate, and examples include a glass plate, a quartz plate, a plastic plate, etc. In addition, 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.

Examples of optically transparent 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 hole injection layer 3 side).
In the case of an organic electroluminescent device in which light is extracted through the anode, the anode is formed from 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 configured to extract light only from the cathode side, the transmittance characteristics of the anode are not important, and therefore, examples of materials that can be 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 the hole injection layer and the 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 hole transport layer also function as electron blocking layers. That is, electrons injected from the cathode and transported from the electron injection layer and/or electron transport layer to the light-emitting layer are prevented from leaking into the hole injection layer and/or hole transport layer by the electron barrier present at the interface between the light-emitting layer and the hole injection layer and/or hole transport layer. As a result, the electrons accumulate at the interface within the light-emitting layer, resulting in effects such as improved current efficiency and an organic electroluminescent device with excellent light-emitting performance.

The materials for the hole injection layer and hole transport layer have at least one of hole injection, hole transport, and electron barrier properties. The materials for the hole injection layer and 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 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, with aromatic tertiary amine compounds being particularly preferred.

Specific examples of the aromatic tertiary amine compound and the styrylamine compound include N,N,N',N'-tetraphenyl-4,4'-diaminophenyl, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD), 2,2-bis(4-di-p-tolylaminophenyl)propane, 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane, N,N,N',N'-tetra-p-tolyl-4,4'-diaminobiphenyl, 1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane, bis(4-dimethylamino-2-methylphenyl)phenylmethane, bis(4-di-p-tolylaminophenyl)phenylmethane, N,N'-diphenyl-N,N'- Examples thereof include di(4-methoxyphenyl)-4,4'-diaminobiphenyl, 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-diphenylaminostilbenzene, 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 hole 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.

[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 an example thereof is 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 light-emitting layer may be made of a phosphorescent material, a fluorescent material, or a thermally activated delayed fluorescent material. In the light-emitting layer, electron-hole pairs recombine, resulting in light emission.

The light-emitting layer may consist of a single small molecule material or a single polymer material, but more commonly consists of a host material doped with a guest compound. Light emission comes primarily from the dopant and can be of any color. There are two types of dopants: fluorescent dopants and phosphorescent dopants.

Examples of host materials include compounds having a biphenyl group, a fluorenyl group, a triphenylsilyl group, a carbazole group, a pyrenyl group, or an anthryl group. More specific examples 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, and carbostyril compounds. The fluorescent dopant may be a combination of two or more selected from these.

Phosphorescent dopants include, for example, organometallic complexes of transition metals such as iridium, platinum, palladium, and osmium.

Specific examples of fluorescent dopants 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))).

Furthermore, 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 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.

[Electron transport layer 7]
An electron transport layer 7 is provided between the light-emitting layer 6 and a cathode 8 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 mentioned above, the electron transport layer preferably contains an azine compound represented by formula (1) above.

In addition to the 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-hydroxyquinolinatolithium (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-naphtho. Examples include bis(2-methyl-8-quinolinato)-2-naphtholatogallium, 2-[3-(9-phenanthrenyl)-5-(3-pyridinyl)phenyl]-4,6-diphenyl-1,3,5-azine, and 2-(4,''-di-2-pyridinyl[1,1':3',1''-terphenyl]-5-yl)-4,6-diphenyl-1,3,5-azine, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), Bphen (4,7-diphenyl-1,10-phenanthroline), BAlq (bis(2-methyl-8-quinolinolato)-4-(phenylphenolato)aluminum), and bis(10-hydroxybenzo[h]quinolinato)beryllium).

The electron transport 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.
When the electron transport layer has a two-layer structure with a first electron transport layer on the light-emitting layer side and a second electron transport layer on the cathode side, it is preferable that the second electron transport layer contains the 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, and rare earth metals.
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 vacuum deposition, spin coating, casting, or LB (Langmuir-Blodgett) method.
There are no particular limitations on the thickness of each layer formed in this way, and it can be selected appropriately depending on the situation, but it is usually in the range of 5 nm to 5 μm.

Anodes and cathodes can be formed by forming a thin film of electrode material using methods such as vapor deposition or sputtering. A pattern can be formed using a mask of the desired shape during vapor deposition or sputtering, or a thin film can be formed by vapor deposition or sputtering, and then a pattern of the desired shape can be formed using photolithography.

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

An organic electroluminescent device according to one embodiment of the present invention may be used as a type of lamp for illumination or as an exposure light source, or as a projection device that projects images, or as a display device that directly views still or moving images. When used as a display device for playing moving images, the driving method may be either a passive matrix method or an active matrix method. Furthermore, by using two or more types of organic electroluminescent devices according to this embodiment that emit different light colors, it is possible to produce a full-color display device.

Note that the 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 explained in more detail below based on examples, but the present invention should not be construed as being limited to 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 fabricated device at room temperature using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse Co., Ltd.).

Synthesis Example 1 Synthesis of Compound (1-3)

Under an argon stream, tetrahydrofuran (300 ml) was added to a flask containing 2-(biphenyl-4-yl)-4-chloro-6-phenyl-1,3,5-triazine (5.2 g, 15.1 mmol), 2-[4-(9-phenanthrenyl)[1,1'-biphenyl]-2-yl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (8.3 g, 18.2 mmol), and Pd(PPh ₃ ) ₄ (524 mg, 0.45 mmol). Furthermore, a 2 M aqueous potassium phosphate solution (23 ml, 45.4 mmol) was added, and the mixture was stirred at 70°C for 20 hours. After cooling to room temperature, water and toluene were added, and the mixture was separated. After distilling off the solvent under reduced pressure, water was added, and the precipitated solid was collected by suction filtration. The resulting solid was washed with water and acetone. The obtained solid was dissolved in toluene (200 ml), activated carbon (1.0 g) was added, and the mixture was heated and stirred at 100°C for 1 hour. The activated carbon was filtered off by suction filtration using a Kiriyama funnel lined with Celite, and the solvent was distilled off under reduced pressure. Recrystallization with toluene gave compound (1-3) as a white solid (yield 7.7 g). The glass transition temperature was 125°C.
¹ H-NMR (CDCl ₃ ) δ (ppm): 8.86 (d, J = 8.1 Hz, 1H), 8.80 (d, J = 8.8 Hz, 1H), 8.57 (d, J = 1.6 Hz, 1H), 8.38-8.41 (m, 4H), 8.12 (m, 1H), 8.00 (m, 1H), 7.89 (s, 1H), 7.83 (dd, J=2.0Hz, 8.0, 1H), 7.61-7.71 (m, 9H), 7.34-7.58 (m, 11H).

Synthesis Reference Example 2: Synthesis of Compound (1-94)
Under an argon stream, tetrahydrofuran (165 ml) was added to a flask containing 2-chloro-4-(4-chlorophenyl)-6-phenyl-1,3,5-triazine (5.00 g, 16.5 mmol), 2-[(1,1':4',1''-terphenyl)-5'-yl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7.66 g, 21.5 mmol), and Pd(PPh ₃ ) ₄ (574 mg, 0.496 mmol). Furthermore, a 2 M aqueous potassium phosphate solution (24.8 ml, 49.6 mmol) was added, and the mixture was stirred at 70°C for 19 hours. After allowing to cool to room temperature, water and toluene were added, and the mixture was separated. The solvent was evaporated under reduced pressure, and water was added. The precipitated solid was collected by suction filtration, and the resulting solid was washed with water and methanol. The obtained solid was recrystallized from toluene to obtain 2-(4-chlorophenyl)-4-phenyl-6-[(1,1':4',1''-terphenyl)-5'-yl]-1,3,5-triazine as a white solid (yield: 4.39 g).
Under an argon atmosphere, tetrahydrofuran (40 ml) was added to a flask containing 2-(4-chlorophenyl)-4-phenyl-6-[(1,1':4',1''-terphenyl)-5'-yl]-1,3,5-triazine (3.00 g, 4.03 mmol), 2-naphthylboronic acid (0.902 g, 5.24 mmol), palladium acetate (18.1 mg, 0.0806 mmol), and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (X-Phos) (76.9 mg, 0.161 mmol). Further, a 2 M aqueous potassium phosphate solution (6.05 ml, 12.1 mmol) was added, and the mixture was stirred at 70°C for 5 hours. After allowing the mixture to cool to room temperature, the precipitated solid was collected by suction filtration and washed with water and acetone. The obtained solid was dissolved in toluene (20 ml), activated carbon (0.3 g) was added, and the mixture was heated and stirred at 100°C for 1 hour. The activated carbon was separated by suction filtration using a Kiriyama funnel lined with Celite, and the solvent was distilled off under reduced pressure. The mixture was recrystallized from toluene to obtain compound (1-94) as a white solid (yield 0.7 g).
¹ H-NMR (CDCl ₃ ) δ (ppm): 8.54 (d, J = 2.4 Hz, 1H), 8.33 (d, J = 8.4 Hz, 2H), 8.21 (d, J = 8.8 Hz, 2H), 7.81-7.85 (m, 2H), 7 .68-7.78 (m, 6H), 7.60 (d, J=7.6Hz, 1H), 7.49-7.56 (m, 7H), 7.30-7.45 (m, 6H), 7.23-7.25 (m, 2H).

Comparative Example 1 Synthesis of Compound (ETL-1)

Under an argon atmosphere, tetrahydrofuran (100 ml) was added to a flask containing 2-(biphenyl-4-yl)-4-chloro-6-phenyl-1,3,5-triazine (3.5 g, 10.2 mmol), 2-[2,5-di(naphthalen-2-yl)phenyl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (5.6 g, 12.2 mmol), and Pd(PPh ₃ ) ₄ (235 mg, 0.20 mmol). Furthermore, 2 M aqueous potassium phosphate solution (15 ml, 30.5 mmol) was added, and the mixture was stirred at 70°C for 20 hours. After cooling to room temperature, the precipitated solid was collected by suction filtration and washed with water and acetone. The resulting solid was dissolved in toluene (420 ml), activated carbon (0.7 g) was added, and the mixture was heated and stirred at 100°C for 1 hour. The activated carbon was removed by suction filtration using a Kiriyama funnel lined with Celite, and the solvent was removed by distillation under reduced pressure. The residue was recrystallized from toluene to obtain a white solid of compound (ETL-1) (yield: 5.3 g). The glass transition temperature was 104°C.
¹ H-NMR (CDCl ₃ ) δ (ppm): 8.76 (d, J = 2.0Hz, 1H), 8.12-8.18 (m, 5H), 8.00-8.09 (m, 7H), 7.75 (d, J = 8.8Hz, 1H), 7.70 (d, J=8.0Hz, 1H), 7.66 (d, J=8.4Hz, 1H), 7.37-7.57 (m, 11H), 7.24-7.38 (m, 2H), 7.18-7.22 (m, 2H).

Below are the solubility data (g/ml-toluene) at 100°C for the azine compounds (1-3), (1-94), and compound (ETL-1) synthesized above.

It can be seen that the azine compound of this example has greater solubility and higher solubility than ETL-1.

The resulting compound was then used for device evaluation.

Element Example 1 (see Figure 2)
(Preparation of the substrate 101 and the anode 102)
A glass substrate with an indium-tin oxide (ITO) transparent electrode, on which a 2 mm wide stripe-patterned ITO film (thickness: 110 nm) was formed, 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 using ozone and ultraviolet light.

(Preparation for vacuum deposition)
After cleaning, each layer was deposited on the surface-treated substrate by vacuum deposition using a vacuum deposition method, and each layer was laminated.
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 formed in the following order according to the film formation conditions.

(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 deposited at a rate of 0.15 nm/sec to form a 10 nm thick film, thereby forming a hole injection layer 103.

(Fabrication 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 form a first hole transport layer 1051.

(Fabrication of Second Hole Transport Layer 1052)
Sublimation-purified N-phenyl-N-(9,9-diphenylfluoren-2-yl)-N-(1,1′-biphenyl-4-yl)amine was deposited at a rate of 0.15 nm/sec to form a film of 5 nm, thereby forming 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 mass ratio of 95:5 to form a 20 nm film, thereby producing the light-emitting layer 106. The film formation rate was 0.18 nm/sec.

(Fabrication 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-azine was deposited at a rate of 0.05 nm/sec to form a 6 nm film, thereby forming a first electron transport layer 1071 .

(Fabrication of Second Electron Transport Layer 1072)
The compound (1-3) synthesized in Synthesis Example 1 and Liq were mixed in a mass ratio of 50:50 to form a 25 nm film, thereby forming a second electron transport layer 1072. The film formation rate was 0.15 nm/sec.

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

As a result of the above, an organic electroluminescent device 100 having a light-emitting area of 4 mm ² was produced as shown in Figure 2. The thickness of each film was measured using a stylus film thickness measuring instrument (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-type epoxy resin (manufactured by Nagase ChemteX Corporation).

A direct current was applied to the organic electroluminescent device fabricated as described above, and the light-emitting characteristics were evaluated using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse). As the light-emitting characteristics, the current efficiency (cd/A) and driving voltage (V) when a current density of 10 mA/ ^cm2 was applied were measured. The current efficiency and driving voltage are relative values, with the result in Device Reference Example 1 described below being set as the reference value (100). The measurement results obtained are shown in Table 2.

Element Reference Example 2
An organic electroluminescent device was produced and evaluated in the same manner as in Element Example 1, except that compound (1-94) was used instead of compound (1-3) in Element Example 1. The measurement results obtained are shown in Table 2.
Element Reference Example 1
An organic electroluminescent device was produced and evaluated in the same manner as in Element Example 1, except that compound (ETL-1) described in JP-A-2019-534548 was used instead of compound (1-3). The measurement results are shown in Table 2.

The azine compound according to one embodiment of the present invention can provide an organic electroluminescent device that exhibits excellent driving voltage, luminous efficiency, and lifespan characteristics.

REFERENCE SIGNS LIST 1,101 Substrate 2,102 Anode 3,103 Hole injection layer 4,104 Charge generation layer 5,105 Hole transport layer 6,106 Light-emitting layer 7,107 Electron transport layer 8,108 Cathode 51,1051 First hole transport layer 52,1052 Second hole transport layer 71,1071 First electron transport layer 72,1072 Second electron transport layer 100 Organic electroluminescent element

Claims (9)

An azine compound represented by formula (1):
In formula (1),
A represents any one group selected from formulas (A-1) to (A-18):
B represents a phenyl group;
^Ar1 is
a phenyl group or a biphenylyl group which may be substituted with one or more groups selected from the group consisting of an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a cyano group, a diarylboryl group, and a phosphine oxide group ;
^Ar2 is
It represents a 2-phenanthrenyl group, a 3-phenanthrenyl group, or a 9-phenanthrenyl group . Ar ² The azine compound according to claim 1, wherein represents a 9-phenanthrenyl group. 3. The azine compound according to claim 1, wherein A represents any one group selected from the formulae (A-1) to (A-8) and (A-10) to (A-18). The azine compound according to any one of claims 1 to 3 , wherein A represents any one group selected from formulas (A-1) to (A-8): The azine compound according to any one of claims 1 to 4, wherein A represents any one group selected from formulas (A-2) to (A-6): The azine compound according to claim 1, represented by formula (1-3), (1-15), (1-27), or (1-39).
A material for organic electroluminescent devices comprising the azine compound according to any one of claims 1 to 6. An electron transport material for organic electroluminescent devices, comprising the azine compound according to any one of claims 1 to 6. An organic electroluminescent device comprising the azine compound according to any one of claims 1 to 6.