JP7243268B2 - Cyclic azine compound, material for organic electroluminescence device, electron transport material for organic electroluminescence device, and organic electroluminescence device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cyclic azine compound, a material for organic electroluminescent devices, an electron-transporting material for organic electroluminescent devices, and an organic electroluminescent device.

Organic electroluminescence devices are used not only for small displays but also for large-sized televisions, lighting, and the like, and are being vigorously developed.
For example, Patent Document 1 discloses a cyclic azine compound having a specific substituent, which contributes to the provision of an organic electroluminescent device having excellent heat resistance, a low driving voltage, and a long life as a material for an organic electroluminescent device. .
Patent Document 2 discloses a cyclic azine compound having a diarylpyridine structure.

JP 2011-063584 A WO2017/221974

In recent years, however, the demand for organic electroluminescence devices from the market has increased more and more, and materials that are excellent in all of current efficiency characteristics, drive voltage characteristics, and long life characteristics are in demand.
Here, although the organic electroluminescence device using the cyclic azine compound disclosed in Patent Document 1 exhibits excellent driving voltage characteristics, further improvements are required for long life characteristics and current efficiency characteristics.
In addition, although the organic electroluminescent device using the cyclic azine compound disclosed in Patent Document 2 exhibits current efficiency characteristics and long life characteristics superior to those of the cyclic azine compound disclosed in Patent Document 1, the driving voltage characteristics and long life There is a demand for further improvements in properties. Especially in recent years, since the number of years of use of smartphones tends to increase, organic electroluminescent elements are required to be able to withstand long-term use. is extremely high.

One aspect of the present invention is a cyclic azine compound that contributes to the formation of a stable amorphous film with excellent driving voltage characteristics and long life characteristics, low crystallinity, a material for an organic electroluminescence device, and an electron transport for an organic electroluminescence device. aimed at providing materials.
Furthermore, another aspect of the present invention is directed to providing an organic electroluminescence device excellent in driving voltage characteristics and long life characteristics.

A cyclic azine compound according to an aspect of the present invention is
represented by formula (1),
A molecular weight of 751 or more and less than 1000:

式（１）中、
Ａｒは、メチル基を有していてもよいフェニル基、ビフェニル基、ターフェニル基、クアテルフェニル基、又はキンキフェニル基を表し；
ｎ１、ｎ２は、それぞれ独立に、０～３の整数を表し；
ｎ３は、１～３の整数を表し；
ｎ３が２以上の整数である場合、複数のＡｒは、同一であっても異なっていてもよい。

In formula (1),
Ar represents a phenyl group optionally having a methyl group, a biphenyl group, a terphenyl group, a quaterphenyl group, or a kinkyphenyl group;
n1 and n2 each independently represent an integer of 0 to 3;
n3 represents an integer of 1 to 3;
When n3 is an integer of 2 or more, multiple Ars may be the same or different.

A cyclic azine compound according to another aspect of the present invention is a cyclic azine compound represented by any one of formulas (1-A) to (1-C):

wherein ^Ra is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
optionally having one or more methyl groups, and three phenyl rings directly or indirectly linked to the unsubstituted phenylene group;

wherein R ^b is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
A group consisting of four phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group;

wherein R ^c is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
It is a group consisting of five phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group.

A material for an organic electroluminescence device according to still another aspect of the present invention contains the cyclic azine compound.
An electron-transporting material for an organic electroluminescence device according to still another aspect of the present invention contains the cyclic azine compound.
An organic electroluminescent device according to still another aspect of the present invention contains the cyclic azine compound.

According to one aspect of the present invention, a cyclic azine compound, a material for an organic electroluminescence device, and a material for an organic electroluminescence device, which has excellent driving voltage characteristics and long life characteristics, has low crystallinity, and contributes to the formation of a stable amorphous film. An electron transport material can be provided.
According to another aspect of the present invention, it is possible to provide an organic electroluminescence device having excellent driving voltage characteristics and long life characteristics.

1 is a schematic cross-sectional view showing an example of a lamination structure of an organic electroluminescence device containing a cyclic azine compound according to one embodiment of the present invention; FIG. 1 is a graph showing DSC measurement results in second heating of compound (1A-29) (Synthesis Example-1). FIG. 4 is a graph showing DSC measurement results in second heating of ETL-1 (Comparative Synthesis Example-1). FIG. FIG. 10 is a graph showing DSC measurement results in second heating of ETL-2 (comparative synthesis example-2). FIG. 1 is a schematic cross-sectional view showing an example of a lamination structure of an organic electroluminescence device containing a cyclic azine compound according to one aspect of the present invention (Device Example-1). FIG.

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

<Cyclic azine compound>
A cyclic azine compound according to an aspect of the present invention is
represented by formula (1),
A molecular weight of 751 or more and less than 1000:

In formula (1),
Ar represents a phenyl group optionally having a methyl group, a biphenyl group, a terphenyl group, a quaterphenyl group, or a kinkyphenyl group;
n1 and n2 each independently represent an integer of 0 to 3;
n3 represents an integer of 1 to 3;
When n3 is an integer of 2 or more, multiple Ars may be the same or different.

A cyclic azine compound according to another aspect of the present invention is a cyclic azine compound represented by any one of formulas (1-A) to (1-C):

wherein ^Ra is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
optionally having one or more methyl groups, and three phenyl rings directly or indirectly linked to the unsubstituted phenylene group;

wherein R ^b is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
A group consisting of four phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group;

wherein R ^c is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
It is a group consisting of five phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group.

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

<<About n1 to n3>>
n1 and n2 each independently represent an integer of 0 to 3; From the viewpoint of raw material availability, n1 and n2 are each independently preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and particularly preferably an integer of 1.
n3 represents an integer of 1-3. In addition, when n3 is an integer of 2 or more, a plurality of Ar may be the same or different.

When n1 and n2 are integers of 1, Ar is preferably a phenyl group, a biphenyl group, or a terphenyl group which may have a methyl group. Here, when n3 is 3, each of the plurality of Ars is preferably a phenyl group or a biphenyl group, each independently optionally having a methyl group. Further, here, when n3 is 2, the plurality of Ars are each independently a phenyl group, a biphenyl group, or a terphenyl group optionally having a methyl group, and at least one of the plurality of Ars is A biphenyl group or a terphenyl group is preferred. Furthermore, here, when n is 1, Ar is preferably a terphenyl group optionally having a methyl group.

When n1 is an integer of 0 and n2 is 1, Ar is preferably a phenyl group, a biphenyl group, a terphenyl group, or a quaterphenyl group which may have a methyl group. Here, when n3 is 3, the plurality of Ars are each independently a phenyl group, a biphenyl group or a terphenyl group which may have a methyl group, and at least one of the plurality of Ars is a biphenyl group. , or a terphenyl group. Further, when n3 is 2, each of the plurality of Ars is preferably a biphenyl group or a terphenyl group which may have a methyl group. Furthermore, here, when n is 1, Ar is preferably a quaterphenyl group optionally having a methyl group.

When n1 and n2 are integers of 0, Ar is preferably a phenyl group, a biphenyl group, a terphenyl group, a quaterphenyl group, or a kinkyphenyl group, which may have a methyl group. Here, when n3 is 3, each of the plurality of Ars is independently a phenyl group, a biphenyl group, a terphenyl group, or a quaterphenyl group which may have a methyl group; At least two are biphenyl groups or terphenyl groups, or at least one of the plurality of Ars is preferably a terphenyl group or a quaterphenyl group. Further, here, when n3 is 2, the plurality of Ars are each independently a biphenyl group, a terphenyl group, or a quaterphenyl group which may have a methyl group, and among the plurality of Ars, at least One is preferably a terphenyl group or a quaterphenyl group. Furthermore, here, when n is 1, Ar is preferably a kinkyphenyl group optionally having a methyl group.

<<Regarding the molecular weight of the cyclic azine compound>>
The molecular weight of the cyclic azine compound represented by formula (1) is 751 or more and less than 1,000. When the molecular weight of the cyclic azine compound is 751 or more, the cyclic azine compound easily forms a stable amorphous film, and in addition, a high glass transition temperature can be achieved, which is preferable. Further, when the molecular weight of the cyclic azine compound is less than 1000, thermal decomposition of the cyclic azine compound can be suppressed during sublimation purification or deposition film formation, which is preferable. Among these, the molecular weight range is preferably 751 or more and less than 950, more preferably 751 or more and less than 875, and particularly preferably 751 or more and less than 800.

Specific examples of the group represented by Ar are not particularly limited, but preferable examples include groups (1) to (5) shown below.

(1): Phenyl group, p-tolyl group, m-tolyl group, o-tolyl group, 2,4-dimethylphenyl group, 3,5-dimethylphenyl group, mesityl group.

(2): biphenyl-2-yl group, biphenyl-3-yl group, biphenyl-4-yl group, 3-methylbiphenyl-4-yl group, 2'-methylbiphenyl-4-yl group, 4'-methyl biphenyl-4-yl group, 2,2'-dimethylbiphenyl-4-yl group, 6-methylbiphenyl-3-yl group, 5-methylbiphenyl-3-yl group, 2'-methylbiphenyl-3-yl group , 4'-methylbiphenyl-3-yl group, 6,2'-dimethylbiphenyl-3-yl group, 5-methylbiphenyl-2-yl group, 6-methylbiphenyl-2-yl group, 2'-methylbiphenyl -2-yl group, 4'-methylbiphenyl-2-yl group, 6,2'-dimethylbiphenyl-2-yl group.

(3): p-terphenyl-4yl group, p-terphenyl-3yl group, p-terphenyl-2yl group, m-terphenyl-4yl group, m-terphenyl-3yl group, m -terphenyl-2yl group, o-terphenyl-4yl group, o-terphenyl-3yl group, o-terphenyl-2yl group.

(4): p-quaterphenyl-4yl group, p-quaterphenyl-3yl group, p-quaterphenyl-2yl group, 1,1′:3′,1″:4″, 1'''-quaterphenyl,6'-yl group, 1,1':3',1'':4'',1'''-quaterphenyl,5'-yl group, 1,1' : 3′,1″:4″,1′″-quaterphenyl,4′-yl group, 1,1′:3′,1″:4″,1′″-quater phenyl,2′-yl group, 1,1′:3′,1″:3″,1′″-quaterphenyl,6′-yl group, 1,1′:3′,1″ : 3'',1'''-quaterphenyl,5'-yl group, 1,1':3',1'':3'',1'''-quaterphenyl,4'-yl group , 1,1′:3′,1″:3″,1′″-quaterphenyl,2′-yl groups.

(5): p-quinkiphenyl-4-yl group, p-quinkiphenyl-3-yl group, p-quinkiphenyl-2-yl group, 1,1′:4′,1″:3″, 1''': 4''', 1'''-quinkiphenyl, 5''-yl group, 1,1': 4', 1'': 3'', 1''': 4'' ',1'''-quinkiphenyl,4''-yl group, 1,1':4',1'':3'',1''':4''',1''''- quinkiphenyl,2''-yl group, 1,1':3',1'':3'',1''':3''',1''''-quinkiphenyl,5''-yl group, 1,1′:3′, 1″:3″, 1′″:3′″, 1′″-quinkiphenyl, 4″-yl group, 1,1′:3 ',1'':3'',1''':3''',1''''-quinkiphenyl,2''-yl group.

Among these substituents, phenyl group, p-tolyl group, biphenyl-2-yl group, biphenyl-3-yl group, biphenyl-4-yl group, p-terphenyl -4yl group, p-terphenyl-3yl group, p-terphenyl-2yl group, m-terphenyl-4yl group, m-terphenyl-3yl group, m-terphenyl-2yl group, o-terphenyl-4yl, o-terphenyl-3yl, o-terphenyl-2yl, 1,1′:3′,1″:4″,1′″-quater phenyl,5′-yl group, 1,1′:3′,1″:3″,1′″-quaterphenyl,5′-yl group, 1,1′:4′,1″ : 3'', 1''': 4''', 1'''-quinkiphenyl, 5''-yl group, 1,1': 3', 1'': 3'', 1'' ': 3''', 1'''-quinkiphenyl, preferably 5''-yl group, phenyl group, p-tolyl group, biphenyl-2-yl group, biphenyl-3-yl group, biphenyl-4-yl group, p-terphenyl-4yl group, p-terphenyl-3yl group, m-terphenyl-4yl group, m-terphenyl-3yl group, o-terphenyl-4yl is more preferably an o-terphenyl-3yl group.

Among these substituents, phenyl group, p-tolyl group, biphenyl-2-yl group, biphenyl-3-yl group, biphenyl-4-yl group, p-terphenyl -4yl group, p-terphenyl-3yl group, p-terphenyl-2yl group, m-terphenyl-4yl group, m-terphenyl-3yl group, m-terphenyl-2yl group, It is more preferably o-terphenyl-4yl, o-terphenyl-3yl, o-terphenyl-2yl, phenyl, p-tolyl, biphenyl-2-yl, biphenyl- 3-yl group, biphenyl-4-yl group, p-terphenyl-4yl group, p-terphenyl-3yl group, m-terphenyl-4yl group, m-terphenyl-3yl group, o- Terphenyl-4yl group and o-terphenyl-3yl group are particularly preferred.

<<About ^Ra >>
^Ra is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
It is a group consisting of three phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group.
That is, R ^a is composed of a total of four phenyl rings. Of these four phenyl rings, one phenyl ring linked to the triazine ring through another phenylene group is unsubstituted, and the remaining three phenyl rings may be substituted with methyl groups.

<<About ^Rb >>
^Rb is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
It is a group consisting of four phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group.
That is, R ^b is composed of a total of five phenyl rings. Of these five phenyl rings, one phenyl ring linked to the triazine ring through another phenylene group is unsubstituted, and the remaining four phenyl rings may be substituted with methyl groups.

<<About ^Rc >>
^Rc is
an unsubstituted phenylene group directly linked to a phenylene ring that is directly linked to a triazine ring;
It is a group consisting of five phenyl rings that may have one or more methyl groups and are directly or indirectly linked to the unsubstituted phenylene group.
That is, R ^c consists of a total of 6 phenyl rings. Of these six phenyl rings, one phenyl ring linked to the triazine ring through another phenylene group is unsubstituted, and the remaining five phenyl rings may be substituted with methyl groups.

When the cyclic azine compound (1) is used as a component of an organic light emitting diode (OLED), effects such as lower voltage and longer life can be obtained. In particular, these effects are exhibited even more when the cyclic azine compound (1) is used as the electron transport layer.

<<Specific examples of preferred cyclic azine compound (1)>>
Preferred specific examples of the cyclic azine compound (1) are shown below, but the present invention is not limited to these compounds.

The cyclic azine compounds shown in Tables 1-1 to 1-4 have a skeleton of formula (1-A) shown below, and the substituent R ^a of the skeleton is -4 shows compounds (1A-1) to (1A-66).
In Tables 1-1 to 1-4, m represents any number from 1 to 66. Therefore, for example, the compound (1-A2) has the skeleton of (1-A), and the substituent R ^a of the skeleton is a p-quaterphenyl-3-yl group (1-A2 ) are shown.

Among the cyclic azine compounds shown in Tables 1-1 to 1-4, the cyclic azine compounds represented by (1-A28) to (1-A50) are preferable from the viewpoint of producing a cyclic azine compound in good yield, and (1 -A28) to (1-A38) are more preferred.

Preferable specific examples of the cyclic azine compound (1) are also shown in Tables 1-5 and 1-6, but the present invention is not limited to these compounds.
The cyclic azine compounds shown in Tables 1-5 and 1-6 have a skeleton of formula (1-B) shown below, and the substituent R ^b possessed by the skeleton is The compounds (1-B1) to (1-B36), which are the groups shown in -6, are shown. The definition of m in Tables 1-5 and 1-6 is the same as in Tables 1-4, except that m represents any number from 1 to 36.

Among the cyclic azine compounds shown in Tables 1-5 and 1-6, the cyclic azine compounds represented by (1-B1) to (1-B15) are preferable from the viewpoint of producing a cyclic azine compound with good yield, and (1 Cyclic azine compounds represented by -B1) to (1-B9) are more preferred.

Furthermore, preferred specific examples of the cyclic azine compound (1) are also shown in Tables 1-7 and 1-8, but the present invention is not limited to these compounds.
The cyclic azine compounds shown in Tables 1-7 to 1-8 have a skeleton of formula (1-C) shown below, and the substituent R ^c possessed by the skeleton is It shows the compounds (1-C1) to (1-C36), which are the groups shown in -8. The definition of m in Tables 1-7 to 1-8 is the same as in Tables 1 to 4, except that m represents any number from 1 to 36.

Among the cyclic azine compounds shown in Tables 1-7 to 1-8, the cyclic azine compounds represented by (1-C1) to (1-C21) are preferable from the viewpoint of producing a cyclic azine compound in good yield, and (1 Cyclic azine compounds represented by -C1) to (1-C15) are more preferred.

Applications of the cyclic azine compound (1) are described below.
<Material for Organic Electroluminescent Device, Electron Transport Material for Organic Electroluminescent Device>
Although the cyclic azine compound (1) is not particularly limited, it can be used, for example, as a material for organic electroluminescence devices. Moreover, the cyclic azine compound (1) can be used, for example, as an electron-transporting material for an organic electroluminescence device.
That is, the material for an organic electroluminescence device according to one aspect of the present invention contains the cyclic azine compound (1). Further, an electron transport material for an organic electroluminescent device according to one aspect of the present invention contains a cyclic azine compound (1). The organic electroluminescent device material and the organic electroluminescent device electron-transporting material containing the cyclic azine compound (1) contribute to the production of organic electroluminescent devices with excellent long-life characteristics and driving voltage characteristics.

<Organic electroluminescent device>
An organic electroluminescent device according to one aspect of the present invention contains a cyclic azine compound (1).
The structure of the organic electroluminescence device is not particularly limited, but includes, for example, 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 generation layer /hole transport layer/light emitting layer/electron transport layer/cathode

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

The organic electroluminescent device 100 comprises 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 conversely, other layers may be added. For example, an electron injection layer may be provided between the electron transport layer 7 and the cathode 8, the charge generation layer 4 may be omitted, and the hole transport layer 5 may be provided directly on the hole injection layer 3. good too. Also, a single layer having the functions of a plurality of layers, such as an electron injection/transport layer having both the function of an electron injection layer and the function of an electron transport layer in a single layer. It may be a configuration provided instead of. Further, for example, the single-layer hole transport layer 5 and the single-layer electron transport layer 7 may each consist of a plurality of layers.

[Layer containing 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 layers between the light-emitting layer and the cathode. Therefore, in the configuration example shown in FIG. 1, the organic electroluminescence 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, the electron transport layer 7 preferably contains the cyclic azine compound (1). The cyclic azine compound (1) may be contained in a plurality of layers included 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 is It may contain a cyclic azine compound (1).
In addition, the organic electroluminescence device 100 in which the electron transport layer 7 contains the cyclic azine compound (1) will be described below.

[Substrate 1]
The substrate is not particularly limited, and examples thereof include a glass plate, a quartz plate, a plastic plate and the like. Further, in the case of a configuration in which emitted light is extracted from the substrate 1 side, the substrate 1 is transparent to the wavelength of light.

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

[Anode 2]
An anode 2 is provided on the substrate 1 (on the hole injection layer 3 side).
For organic electroluminescent devices configured such that emitted 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 include indium-tin oxide (ITO; Indium Tin Oxide), indium-zinc oxide (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, metal selenides such as zinc selenide, metal sulfides such as zinc sulfide, etc. is mentioned.
In the case of an organic electroluminescence device configured to extract light only from the cathode side, the transmission characteristics of the anode are not important. Accordingly, examples of materials used for the anode in this case include gold, iridium, molybdenum, palladium, platinum, and the like.
A buffer layer (electrode interface layer) may be provided on the anode.

[Hole injection layer 3, hole transport layer 5]
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 between the anode 2 and a light emitting layer 6 described later.
The hole injection layer and the hole transport layer have a function of transferring holes injected from the anode to the light emitting layer, and the hole injection layer and the hole transport layer are interposed between the anode and the light emitting layer. As a result, more holes are injected into the light-emitting layer at a lower electric field.

Moreover, the hole injection layer and the 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 the electron transport layer to the light-emitting layer are blocked by the electron barrier present at the interface between the light-emitting layer and the hole injection layer and/or the hole transport layer. , leakage into the hole injection layer and/or the hole transport layer is suppressed. As a result, the electrons are accumulated at the interface in the light-emitting layer, resulting in an effect such as an improvement in current efficiency, and an organic electroluminescence device with excellent light-emitting performance can be obtained.

Materials for the hole injection layer and the hole transport layer have at least one of hole injection properties, hole transport properties, and electron blocking properties. Materials 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, and amino-substituted chalcone. derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers (especially thiophene oligomers), porphyrin compounds, aromatic tertiary amine compounds, styryl Examples include amine 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-tolyl aminophenyl)-4-phenylcyclohexane, bis(4-dimethylamino-2-methylphenyl)phenylmethane, bis(4-di-p-tolylaminophenyl)phenylmethane, N,N'-diphenyl-N,N'-di(4-methoxyphenyl)-4,4'-diaminobiphenyl,N,N,N',N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'-bis(diphenylamino) quadri Phenyl, N,N,N-tri(p-tolyl)amine, 4-(di-p-tolylamino)-4'-[4-(di-p-tolylamino)styryl]stilbene, 4-N,N-diphenyl amino-(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 like.
Inorganic compounds such as p-type-Si and p-type-SiC can also be cited as examples of the material for the hole injection layer and the material for the hole transport layer.

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

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

[Light emitting layer 6]
A light-emitting layer 6 is provided between the hole-transporting layer 5 and an electron-transporting layer 7 to be described later.
Materials for the light-emitting layer include phosphorescent light-emitting materials, fluorescent light-emitting materials, and thermally activated delayed fluorescent light-emitting materials. In the light-emitting layer, electron-hole pairs recombine, resulting in light emission.

The emissive 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 dopants and can have 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, 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 and the like can be mentioned.

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, and indenoperylenes. 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 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](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.

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

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

[Electron transport layer 7]
An electron transport layer 7 is provided between the light emitting layer 6 and a cathode 8 which will be described later.
The electron transport layer has a function of transmitting electrons injected from the cathode to the light emitting layer. By interposing an electron-transporting 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 the cyclic azine compound represented by the above formula (1).

The electron transport layer may further contain a conventionally known electron transport material in addition to the cyclic azine compound (1). Conventionally known electron transport materials include, for example, 8-hydroxyquinolinate lithium (Liq), bis(8-hydroxyquinolinate) zinc, bis(8-hydroxyquinolinate) copper, bis(8-hydroxyquinolinate), 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-cresolato)gallium, bis(2 -methyl-8-quinolinato)-1-naphtholatoaluminum, or bis(2-methyl-8-quinolinato)-2-naphtholatogallium, 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-(phenylphenolato)aluminum), and bis(10-hydroxybenzo[h]quinolinato)beryllium).

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

[Cathode 8]
A cathode 8 is provided on the electron transport layer 7 .
In the case of an organic electroluminescence device configured so that only light emitted through the anode is taken out, the cathode can be made of 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 (electron transport layer side).

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

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

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

The organic electroluminescence element according to one aspect of the present invention may be used as a kind of lamp such as an illumination light source or an exposure light source, a type of projection device that projects an image, or a still image or a moving image that can be directly viewed. You may use it as a display apparatus (display) of the type to carry out. When used as a display device for reproducing moving images, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. Further, by using two or more kinds of organic electroluminescence elements of this embodiment having different emission colors, a full-color display device can be produced.

The cyclic azine compound (1) according to one aspect of the present invention can be synthesized by appropriately combining known reactions (eg, Suzuki-Miyaura cross-coupling reaction, etc.).
For example, the cyclic azine compound (1) according to one aspect of the present invention can be synthesized according to any one of the following reaction formulas (a) to (d), but these examples are not to be construed as limiting. not a thing

In reaction formulas (a) to (d), Ar and n1 to n3 have the same definitions as in formula (1).

Y represents a leaving group, which is not particularly limited and includes, for example, chlorine atom, bromine atom, iodine atom and triflate. Among these, a bromine atom or a chlorine atom is preferable in that the reaction yield is good. However, in some cases, it is preferable to use triflate from the availability of raw materials.

Each M independently represents ZnR ¹ , MgR ² , Sn(R ³ ) ₃ or 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 and 1 carbon atom represents 4 alkyl groups or phenyl groups, and two R ⁴ in B(OR ⁴ ) ₂ may be the same or different. Also, two ^R4 's may be combined to form a ring containing an oxygen atom and/or a boron atom.

Examples of ZnR ¹ and MgR ² include ZnCl, ZnBr, ZnI, MgCl, MgBr and MgI.
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 . Further, examples of B(OR ⁴ ) ₂ when two R ⁴ are combined to form a ring containing an oxygen atom and/or a boron atom include the following (C-1) to (C-6 ) can be exemplified, and the group represented by (C-2) is preferable in that the yield is good.

Among these reaction formulas, reaction formula (a), (b) or (d) is preferable because the purity of the resulting cyclic azine compound (1) is high.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited by these examples.

¹ H-NMR measurement was performed using Gemini200 (manufactured by Varian).
The luminous properties of the organic electroluminescent device were evaluated by applying a direct current to the fabricated device at room temperature and using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse Co., Ltd.).

The glass transition temperature and cold crystallization temperature were measured by DSC (Differential Scanning Calorimetry) using DSC7020 (manufactured by Hitachi High-Tech Science).
The DSC measurement conditions are as follows. Note that the measurement was performed in a nitrogen atmosphere (flow rate: 50 ml/min). First heating, first cooling, and second heating were performed in this order, and the glass transition temperature during the second heating was defined as the glass transition temperature of the sample.
Sample amount: 5 to 10 mg
Measurement condition:
<Fast heating>
Heating rate: 10°C/min
Measurement temperature range: 30°C to 400°C
<Fast Cooling>
Rapid cooling with dry ice <second heating>
Heating rate: 5°C/min
Measurement temperature range: 30°C to 400°C

<Synthesis Example-1: Synthesis of compound (1-A29)>

2,4-bis[(1,1′-biphenyl)-4-yl]-6-(3-chlorophenyl)-1,3,5-triazine (2. 00 g, 4.03 mmol), 4,4,5,5-tetramethyl-2-[5′-phenyl(1,1′:3′,1″-tetraphenyl)-3-yl)]-1, 3,2-Dioxaborolane (2.10 g, 4.86 mmol) was dissolved in tetrahydrofuran (40 mL). To this was added palladium acetate (18 mg, 0.08 mmol) and 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (77 mg, 0.16 mmol; X-Phos) dissolved in tetrahydrofuran (5 mL). The resulting solution was added followed by 2M aqueous potassium carbonate solution (3 mL, 6 mmol) and stirred at 70° C. for 17 hours. After allowing to cool to room temperature, methanol (100 mL) was added, and the precipitated solid was separated by filtration. The solid obtained was washed with water (50 mL) and methanol (50 mL). This solid was dissolved in toluene, added with activated carbon and stirred, and then filtered through celite. A solid precipitated by recrystallization was collected by filtration to obtain the target compound (1-A29) as a white solid (yield: 1.96 g, yield: 63.5%, HPLC purity: 99.8%).

¹ H-NMR (CDCl ₃ ) δ (ppm): 9.09 (t, 1H), 8.87 (dt, 4H), 8.83 (td, 1H), 8.07 (t, 1H), 7 .94-7.90 (m, 3H), 7.84 (t, 1H), 7.82-7.64 (m, 16H), 7.54-7.34 (m, 12H)
The glass transition temperature of compound (1-A29) was 111° C. and no cold crystallization temperature was observed.

<Synthesis Comparative Example-1>
4,6-diphenyl-2-[2′-(4,6-diphenylpyridin-2-yl)-biphenyl-3-yl]-1 described in Patent Document 2 (International Publication No. 2017/221974) , 3,5-triazine (ETL-1) was prepared by the method described in said patent document 2.
The glass transition temperature of compound ETL-1 was 91°C and the cold crystallization temperature was 155°C.
<Synthesis Comparative Example-2>
Journal of Materials Chemistry, 2009, 19, p. 8112-8118, was prepared by the method described therein.
The glass transition temperature of compound ETL-2 was 54°C and the cold crystallization temperatures were 89°C and 136°C.
<Synthesis Comparative Example-3>
Chemistry Letters, 2004, 33, p. 1244-1245, was prepared by the method described therein.
No glass transition temperature was observed for compound ETL-3.

Table 2 summarizes the glass transition temperatures and cold crystallization temperatures of the compounds obtained in Synthesis Example-1 and Synthesis Comparative Examples-1 to 3.

Further, FIG. 2 shows the DSC measurement results of the compound (1-A29: Synthesis Example-1) in the second heating. 3 and 4 show the DSC measurement results in the second heating of ETL-1 (Comparative Synthesis-1) and ETL-2 (Comparative Synthesis-2), respectively. Both the glass transition temperature and the cold crystallization temperature are calculated from the temperature at the start of the phase transition, that is, the onset temperature.
2 to 4 show that the compound (1A-29) according to one embodiment of the present invention has a higher glass transition temperature than ETL-1 and ETL-2. Furthermore, it can be seen that a cold crystallization peak is observed in ETL-1 and ETL-2, but not observed in the compound (1-A29) according to one embodiment of the present invention. Cold crystallization is a phenomenon in which a sample recrystallizes during heating. On the other hand, since ETL-3 is easily crystallized, the glass transition temperature is not observed, indicating that the film quality is unstable.

That is, the cyclic azine compound according to one embodiment of the present invention is less likely to be crystallized and has stable film quality. The cyclic azine compound according to one aspect of the present invention has a high glass transition temperature due to its large molecular weight. In addition, it is believed that the cyclic azine compound according to one aspect of the present invention has low molecular symmetry due to the effect of Ar groups at appropriate positions, inhibits crystallization, and satisfactorily maintains amorphousness. be done.

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

<Device example-1 (see FIG. 5)>
(Preparation of substrate 101 and anode 102)
As a substrate having an anode on its surface, a glass substrate with an ITO transparent electrode, in which an indium-tin oxide (ITO) film (thickness: 110 nm) with a width of 2 mm was patterned in stripes, was prepared. Then, after washing the substrate with isopropyl alcohol, the surface was treated by ozone ultraviolet washing.

(Preparation for vacuum deposition)
Each layer was vacuum-deposited on the surface-treated substrate after cleaning by a vacuum deposition method to laminate each layer.
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 produced in the following order according to the film forming conditions of each layer.

(Preparation 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-fluorene-2 - amine and 1,2,3-tris[(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropane were deposited at a rate of 0.15 nm/sec to form a film of 10 nm, forming a hole injection layer; 103 was made.

(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-fluorene-2 -Amine was deposited at a rate of 0.15 nm/sec to a thickness of 85 nm 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 deposited at a rate of 0.15 nm/sec to form a 5 nm film. , a second hole transport layer 1052 was produced.

(Production of light-emitting layer 106)
3-(10-phenyl-9-anthryl)-dibenzofuran and 2,7-bis[N,N-di-(4-tertbutylphenyl)]amino-bisbenzofurano-9,9′-spirofluorene purified by sublimation was deposited at a ratio of 95:5 (mass ratio) to a thickness of 20 nm to prepare the light-emitting layer 106 . The deposition 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 deposited to a thickness of 6 nm at a rate of 0.05 nm/sec to form the first electron transport layer 1071 .

(Preparation of second electron transport layer 1072)
The compound (1-A29) synthesized in Synthesis Example-1 and Liq were deposited at a ratio of 50:50 (mass ratio) to a thickness of 25 nm to prepare a second electron transport layer 1072 . The deposition rate was 0.15 nm/sec.

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

As described above, an organic electroluminescence device 100 having a light emitting area of 4 mm ² as shown in FIG. 5 was produced. Each film thickness was measured with a stylus film thickness meter (DEKTAK, manufactured by Bruker).

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

A direct current was applied to the organic electroluminescence device produced as described above, and the luminescence characteristics were evaluated using a luminance meter (product name: BM-9, manufactured by Topcon Technohouse). As light emission characteristics, current efficiency (cd/A) was measured when a current density of 10 mA/cm ² was applied, and element life (h) during continuous lighting was measured. The device life (h) in Table 4 is measured by measuring the luminance decay time during continuous lighting when the manufactured device is driven at an initial luminance of 1000 cd/m ² , and until the luminance (cd/m ² ) decreases by 5%. was measured. The drive voltage, current efficiency, and device life are relative values with the result of device reference example 2 described later as a reference value (100). Table 3 shows the measurement results obtained.

<Element reference example-1>
An organic electroluminescence device was produced and evaluated in the same manner as in Device Example-1, except that ETL-1 synthesized in Comparative Synthesis Example-1 was used instead of the compound (1-A29) in Device Example-1. bottom. Table 3 shows the measurement results obtained.

<Element reference example-2>
In Element Example-1, 2-[5-(9-phenanthryl)-4′-(2- Pyrimidyl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (ETL-4) was used to prepare an organic electroluminescent device in the same manner as in Device Example-1, evaluated. Table 3 shows the measurement results obtained.

The cyclic azine compound (1) according to one aspect of the present invention is extremely excellent in heat resistance during film formation, and by using the compound, it is possible to provide an organic electroluminescence device excellent in driving voltage characteristics and long life characteristics.
Moreover, the cyclic azine compound (1) according to one aspect of the present invention is used as an electron-transporting material for organic electroluminescence devices, which is excellent in low driving voltage. Furthermore, according to the cyclic azine compound (1), it is possible to provide an organic electroluminescence device with low power consumption.
In addition, the cyclic azine compound according to one aspect of the present invention can provide a long-life organic electroluminescence device because the stability of the deposited film is excellent.
In addition, since the thin film made of the cyclic azine compound (1) according to one aspect of the present invention is excellent in electron-transporting ability, hole-blocking ability, redox resistance, water resistance, oxygen resistance, electron injection characteristics, etc., it is It is useful as a material for devices, and as an electron transport material, a hole block material, a light emitting host material, and the like. It is especially useful when used as an electron transport material.
Further, the cyclic azine compound (1) according to one aspect of the present invention has a wide bandgap and a high triplet excitation level. TADF) can be suitably used for an organic electroluminescence device.

Reference Signs List 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 electroluminescence device

Claims (4)

A cyclic azine compound having a molecular weight of 751 or more and less than 1000, represented by formula (1-A) or formula (1-B):

In the formula, R ^a is any one of the groups listed in Tables 1-1 to 1-4.

In the formula, R ^b is any one of the groups listed in Tables 1-5 to 1-6.

A material for an organic electroluminescence device comprising the cyclic azine compound according to claim 1 . An electron transport material for an organic electroluminescence device, comprising the cyclic azine compound according to claim 1 . An organic electroluminescence device comprising the cyclic azine compound according to claim 1 .

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