JP7732181B2 - Azine compound, organic electroluminescent device material containing the azine compound, and organic electroluminescent device - Google Patents

Description

The present invention relates to an azine compound, a material for organic electroluminescent devices containing the azine compound, and an organic electroluminescent device.

Organic electroluminescent devices are beginning to be put to practical use, primarily in small mobile devices. However, further expansion of their applications requires improved performance, and materials with low driving voltages, high luminous efficiency, and long life are required. Therefore, materials for organic electroluminescent devices must have low crystallization temperatures and melting points.

Patent documents 1 to 3 disclose azine compounds that are materials for organic electroluminescent devices that are highly efficient and can reduce driving voltage.

WO 2007/023840 Japanese Patent Application Laid-Open No. 2019-99513 Japanese Patent Application Laid-Open No. 2019-147791

There is strong market demand for expanded applications and environments in which they can be used, and the azine compounds disclosed in Patent Documents 1 to 3 do not fully satisfy the three characteristics of drive voltage, luminous efficiency, and lifespan characteristics. Therefore, there is a demand for compounds that achieve these three characteristics at an even higher level.

Therefore, one aspect of the present invention aims to provide an azine compound with a low crystallization temperature and melting point that forms an organic electroluminescent device with excellent driving voltage characteristics and lifespan characteristics, and a material for an organic electroluminescent device that contains the azine compound.

Furthermore, another aspect of the present invention aims to provide an organic electroluminescent device that exhibits high luminous efficiency and can be used in a variety of applications or in a variety of environments.

The objects of each aspect of the present invention have been achieved as follows.
1) An azine compound represented by the following formula (1):
Formula (1)
During the ceremony,
Ar ¹ and Ar ² independently represent a phenyl group, a biphenyl group, or a naphthyl group.
Ar ³ represents a group having 4 to 25 carbon atoms and having a group selected from the following (a) and (b):
(a) an aromatic hydrocarbon group having 6 to 18 carbon atoms and 1 to 3 rings; (b) a heteroaromatic group L having 4 to 18 carbon atoms and composed of atoms selected from the group consisting of H, C, O, and divalent S; and ¹ represents a divalent 6-membered ring linking group.
Each X independently represents C—H, C— _CH3 , or N, provided that the number of N in ^L1 is 1 or 2.
ⁿ¹ represents an integer of 1 to 3.
ⁿ² represents an integer of 0 to 2.
2) A material for organic electroluminescent devices, comprising the azine compound described in 1 above.
3) An organic electroluminescent device comprising the azine compound described in 1) above.

One aspect of the present invention provides an azine compound with a low crystallization temperature and melting point, which allows the formation of an organic electroluminescent device that exhibits excellent driving voltage characteristics and lifespan characteristics, and a material for the organic electroluminescent device that contains the azine compound.

Furthermore, according to another aspect of the present invention, it is possible to provide an organic electroluminescent device that exhibits high luminous efficiency and can be used for a variety of applications.

1 is a schematic cross-sectional view showing an example of a layered structure of an organic electroluminescence element according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of a laminated structure of an organic electroluminescence element according to one embodiment of the present invention (structure of element example 1).

The azine compound according to one embodiment of the present invention will be described in detail below.
<Azine compounds>

An azine compound according to one embodiment of the present invention is an azine compound represented by formula (1).
Formula (1)
During the ceremony,
Ar ¹ and Ar ² independently represent a phenyl group, a biphenyl group, or a naphthyl group.
Ar ³ represents a group having 4 to 25 carbon atoms and having a group selected from the following (a) and (b):
(a) an aromatic hydrocarbon group having 6 to 18 carbon atoms and 1 to 3 rings; (b) a heteroaromatic group L having 4 to 18 carbon atoms and composed of atoms selected from the group consisting of H, C, O, and divalent S; and ¹ represents a divalent 6-membered ring linking group.
Each X independently represents C—H, C— _CH3 , or N, provided that the number of N in ^L1 is 1 or 2.
ⁿ¹ represents an integer of 1 to 3.
ⁿ² represents an integer of 0 to 2.

Hereinafter, the azine compound represented by formula (1) may be referred to as azine compound (1).

The definitions of the substituents in the azine compound (1) and preferred examples thereof are as follows:
[Regarding ^Ar1 and ^Ar2 ]

Ar ¹ and Ar ² independently represent a phenyl group, a biphenyl group, or a naphthyl group, and each of Ar ¹ and Ar ² independently may be substituted with one or more groups selected from a fluorine atom, a methyl group, and a phenyl group.
[Regarding ^Ar3 ]

Ar ³ represents a group having 4 to 25 carbon atoms and having a group selected from the following (a) and (b):
(a) an aromatic hydrocarbon group having 6 to 18 carbon atoms and 1 to 3 rings; (b) a heteroaromatic group having 4 to 18 carbon atoms and composed of atoms selected from the group consisting of H, C, O, and divalent S;

Ar ³ preferably has 6 to 25 carbon atoms.

It is more preferable that Ar ³ represents a group selected from the following (a′) to (c′):
(a') an unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms and having 1 to 3 rings; (b') an unsubstituted heteroaromatic group having 4 to 18 carbon atoms and composed of atoms selected from the group consisting of H, C, O and divalent S; (c') a group in which (a') or (b') is substituted with one or more groups selected from the group consisting of methyl groups and phenyl groups.

^Ar3 is preferably a phenyl group, a naphthyl group, a fluorenyl group, an anthranyl group, a phenanthrenyl group, a dibenzofuranyl group, or a dibenzothiophenyl group.
[Regarding ^L1 ]

^L1 represents a divalent 6-membered ring linking group. Each of the four Xs independently represents -C-H, C- _CH3 , or N. However, the number of N in ^L1 is 1 or 2. When N is 2, it is preferable that the two Ns are not adjacent to each other. In particular, it is preferable that the number of N in ^L1 is 1.

Examples of ^L1 include a 1,4-phenylene group, a 2,5-pyridylene group, a 3,6-pyridylene group, a 2,5-pyrazylene group, a 2,5-pyrimidylene group, and a 2,5-pyridazylene group.
[Regarding ⁿ¹ and ⁿ² ]

ⁿ¹ represents an integer of 1 to 3. It is preferable that ⁿ¹ is 1 or 2.
ⁿ² represents an integer of 0 to 2. ⁿ² is preferably 0 or 1.
[Specific examples of azine compound (1)]

Specific examples of azine compound (1) are shown below, but the present invention is not limited to these.

The azine compound (1) according to one embodiment of the present invention can be produced by appropriately combining known reactions (for example, Suzuki-Miyaura cross-coupling reaction, etc.).
<Materials for organic electroluminescent devices>

Azine compound (1) is useful as a material for organic electroluminescent devices. Azine compound (1) can be used, for example, as an electron transport material for organic electroluminescent devices. A material for organic electroluminescent devices containing azine compound (1) exhibits high luminous efficiency and long lifetime characteristics, and can be used to produce organic electroluminescent devices that can be used for various purposes or in various environments.
<Organic electroluminescent device>

The following describes an organic electroluminescent device containing azine compound (1) (hereinafter sometimes simply referred to as an organic electroluminescent device).

An organic electroluminescent device according to one embodiment 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 (v).
(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

Azine compound (1) may be contained in any of the above layers, but in terms of achieving excellent light-emitting properties in the organic electroluminescent device, it is preferably contained in one or more layers selected from the group consisting of the light-emitting layer and the layer between the light-emitting layer and the cathode.

Therefore, in the configurations (i) to (v) above, it is preferable that the azine compound (1) be contained in one or more layers selected from the group consisting of the light-emitting layer, the electron-transporting layer, and the electron-injecting layer.

The organic electroluminescent device according to one aspect of the present invention will be described in more detail below, taking the above configuration (v) as an example, with reference to Figure 1.

Note that the organic electroluminescent element shown in Figure 1 has a so-called bottom-emission element configuration, but the organic electroluminescent element according to one aspect of the present invention is not limited to a bottom-emission element configuration. In other words, the organic electroluminescent element according to one aspect of the present invention may have other known element configurations, such as a top-emission type.

Figure 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.

The organic electroluminescent device 100 comprises, in this order, a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, an emitting layer 5, an electron transport layer 6, an electron injection layer 7, and a cathode 8. However, some of these layers may be omitted, or other layers may be added. For example, a hole blocking layer may be provided between the emitting layer 5 and the electron transport layer 6, or the hole injection layer 3 may be omitted and the hole transport layer 4 may be provided directly on the anode 2.

Alternatively, a single layer having the functions of both the electron injection layer and the electron transport layer, such as an electron injection/transport layer having the functions of both the electron injection layer and the electron transport layer, may be provided instead of the multiple layers.Furthermore, for example, the single-layer hole transport layer 4 and the single-layer electron transport layer 6 may each be made up of multiple layers.
<<Layer Containing Azine Compound (1)>>

In the configuration example shown in FIG. 1, the organic electroluminescent device 100 contains an azine compound (1) in one or more layers selected from the group consisting of the light-emitting layer 5, the electron transport layer 6, and the electron injection layer 7. In particular, it is preferable that the electron transport layer 6 contains the azine compound (1). Note that the azine compound (1) may be contained in multiple layers of the organic electroluminescent device.

The organic electroluminescent device 100 in which the electron transport layer 6 contains the azine compound (1) will be described below.
[Substrate 1]

There are no particular limitations on the substrate 1, and examples include a glass plate, a quartz plate, and a plastic plate.

Examples of the substrate 1 include a glass plate, a quartz plate, a plastic plate, and a plastic film. Of these, a glass plate, a quartz plate, and a light-transmitting plastic film are preferred.

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

In the case where light is extracted from the substrate 1 side, the substrate 1 is transparent to the wavelength of the light.
[Anode 2]

An anode 2 is provided on the substrate 1 (on the hole injection layer 3 side).

Examples of anode materials include metals, alloys, electrically conductive compounds, and mixtures thereof, each having a large work function (for example, 4 eV or more). Specific examples of anode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO.

In the case of an organic electroluminescent device configured so that light is extracted through the anode, the anode is formed from a conductive transparent material that is transparent or substantially transparent to the light emitted.
[Hole injection layer 3, hole transport layer 4]

Between the anode 2 and the light-emitting layer 5, a hole injection layer 3 and a hole transport layer 4 are provided in this order from the anode 2 side.

The hole injection layer and hole transport layer have the function of transporting holes injected from the anode to the light-emitting layer. By placing these hole injection layer and hole transport layer between the anode and light-emitting layer, more 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 barrier 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 to 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 light-emitting 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 because of the good performance of the organic electroluminescent device, with aromatic tertiary amine compounds being 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(m-tolyl)-[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 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-(m-tolyl)-N-phenylamino]triphenylamine (MTDATA).

Inorganic compounds such as p-type Si and p-type SiC can also be used as examples of materials for the hole injection layer and hole transport layer.

The hole injection layer and the hole transport layer may have a single 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 5]

The light-emitting layer 5 is provided between the hole transport layer 4 and the electron transport layer 6.

Materials for the light-emitting layer include phosphorescent materials, fluorescent materials, and thermally activated delayed fluorescent materials. 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.

Examples of host materials include compounds having a biphenylyl 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-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.

Examples of fluorescent dopants include anthracene, pyrene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine, quinacridone, dicyanomethylenepyran compounds, thiopyran compounds, polymethine compounds, pyrylium, thiapyrylium compounds, fluorene derivatives, periflanthene derivatives, indenoperylene derivatives, bis(azinyl)amine boron compounds, bis(azinyl)methane compounds, carbostyril compounds, boron compounds, and cyclic amine 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 luminescent material is not limited to being contained only in the luminescent layer. For example, the luminescent material may be contained in a layer adjacent to the luminescent layer (hole transport layer 4 or electron transport layer 6). This can further increase the luminous efficiency of the organic electroluminescent element.

The light-emitting 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.
[Electron transport layer 6]

An electron transport layer 6 is provided between the light-emitting layer 5 and the electron injection layer 7.

The electron transport layer has the function of transporting electrons injected from the cathode to the light-emitting layer. By interposing the electron transport layer between the cathode and the light-emitting layer, electrons are injected into the light-emitting layer at a lower electric field.

As described above, the electron transport layer preferably contains azine compound (1). Furthermore, in addition to azine compound (1), the electron transport layer may further contain one or more types selected from conventionally known electron transport materials.

When the azine compound (1) is not contained in the electron transport layer but is contained in another layer, one or more electron transport materials selected from conventionally known electron transport materials can be used as the electron transport material constituting the electron transport layer.

Conventionally known electron transport materials include alkali metal complexes, alkaline earth metal complexes, and earth metal complexes. Examples of alkali metal complexes, alkaline earth metal complexes, and earth metal complexes 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, and tris(8-hydroxyquinolinato). Examples include 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, bis(2-methyl-8-quinolinato)-1-naphtholatealuminum, and bis(2-methyl-8-quinolinato)-2-naphtholategallium.

The electron transport layer may have a single layer structure made of one or more materials, or a laminate structure made of multiple layers of the same or different compositions.

In the organic electroluminescent device according to one aspect of the present invention, an electron injection layer may be provided for the purpose of improving electron injection properties and improving device characteristics (e.g., luminous efficiency, low-voltage driving, or high durability).
[Electron injection layer 7]

An electron injection layer 7 is provided between the electron transport layer 6 and the cathode 8. The electron injection layer has the function of transporting electrons injected from the cathode to the light-emitting layer. By interposing the electron injection layer between the cathode and the light-emitting layer, electrons are injected into the light-emitting layer at a lower electric field.

Examples of materials for the electron injection layer include organic compounds such as fluorenone, anthraquinodimethane, diphenoquinone, thiopyran dioxide, oxazole, oxadiazole, triazole, imidazole, perylene tetracarboxylic acid, fluorenylidenemethane, anthraquinodimethane, and anthrone.

Further, examples of materials for the electron injection layer include inorganic compounds such as various oxides, fluorides, nitrides, and oxynitrides, such as _SiO2 , AlO, SiN, SiON, AlON, GeO, LiO, LiON, TiO, TiON, TaO, TaON, TaN, LiF, C, and Yb.
[Cathode 8]

A cathode 8 is provided on the electron injection layer 7. In the case of an organic electroluminescent element configured so that only light emitted through the anode is extracted, the cathode can be made of any conductive material.

Cathode materials include, for example, metals with a low work function (hereinafter also referred to as electron-injecting metals), alloys, electrically conductive compounds, and mixtures thereof. Here, a metal with a low work function is, for example, a metal with a work function of 4 eV or less.

Specific examples of 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.

Among these, from the viewpoints of electron injection properties and durability against oxidation, etc., mixtures of an electron injection metal and a second metal that has a larger and more stable work function than the electron injection metal, such as magnesium/silver mixtures, magnesium/aluminum mixtures, magnesium/indium mixtures, aluminum/aluminum oxide (Al ₂ O ₃ ) mixtures, and lithium/aluminum mixtures, are preferred.
[Method of forming each layer]

The layers described above, excluding the electrodes (anode and cathode), can be formed by thinning using known methods such as vacuum deposition, spin coating, casting, and the Langmuir-Blodgett (LB) method. The materials for each layer may be used alone or, if necessary, together with materials such as binder resins and solvents.

There are no particular restrictions on the film 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 thinning the 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.

The layer containing azine compound (1) may be formed in combination with the above-mentioned conventionally known electron transport material. Therefore, for example, azine compound (1) and a conventionally known electron transport material may be co-deposited, or a layer of a conventionally known electron transport material may be laminated on a layer of azine compound (1).

Organic electroluminescent devices can be used as a type of lamp for illumination or as an exposure light source, or as a projection device that projects images onto a screen, or as a display device that displays still or moving images directly.

When organic electroluminescent elements are used as display devices for video playback, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. Furthermore, by using two or more types of organic electroluminescent elements that emit different colors, it is possible to create a full-color display device.

When used as an electron transport layer, azine compound (1) can provide organic electroluminescent devices with significantly superior luminous efficiency and long life characteristics compared to conventionally known azine compounds. Furthermore, azine compound (1) has a linear three-dimensional skeleton, which results in high amorphousness and high film stability.

This is expected to improve the driving stability and luminous efficiency of organic electroluminescent devices. Furthermore, due to its distinctive skeleton, azine compound (1) has high chemical stability and can contribute to extending the life of organic electroluminescent devices.

Azine compound (1) can be used as an electron transport layer in an organic electroluminescent device to provide an azine compound that can achieve low-voltage operation, high efficiency, and long life of the device at a high level. Furthermore, organic electroluminescent devices that use azine compound (1) can be provided that can achieve low-voltage operation, high efficiency, and long life.

The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited to these examples.
[ ¹ H-NMR measurement]

Gemini 200 (Varian) was used for ¹ H-NMR measurements. ¹ H-NMR measurements were performed using deuterated chloroform (CDCl ₃ ) as the measurement solvent and tetramethylsilane (TMS) as the internal standard. Commercially available reagents were used.
[DSC Measurement (Glass Transition Temperature, Crystallization Temperature, Melting Point)]

Measurements of glass transition temperature, crystallization temperature, and melting point were performed using a DSC7020 (product name, manufactured by Hitachi High-Tech Science Corporation).

The DSC measurement conditions were as follows. The measurement was carried out under a nitrogen atmosphere (flow rate 50 ml/min). First cooling and second heating were carried out in this order, and the glass transition temperature, crystallization temperature, and melting point during the second heating were taken as the glass transition temperature, crystallization temperature, and melting point of the sample, respectively.
Sample amount: 5 to 10 mg
Measurement conditions:
<First heating>
Temperature increase rate: 15°C/min
Measurement temperature range: 30℃ to 360℃
<First cooling>
Rapid cooling with dry ice (second heating)
Temperature increase rate: 5°C/min
Measurement temperature range: 30℃ to 360℃
[Measurement of luminescence characteristics]

The light emitting characteristics of the organic electroluminescent device were evaluated by applying a direct current to the fabricated device in an environment of 25° C. using a luminance meter BM-9 (product name, manufactured by Topcon Technohouse Co., Ltd.).
(Synthesis Example 1: Synthesis of A-67)

Under an argon atmosphere, 2-[4'-{(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,1'-biphenyl-4-yl}]-4,6-diphenyl-1,3,5-triazine (6.0 g, 11.7 mmol), 5-chloro-2-(1-naphthyl)pyridine (3.37 g, 14.1 mmol), palladium acetate (105 mg, 0.939 mmol), and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (447 mg, 0.469 mmol; X-Phos) were dissolved in tetrahydrofuran (120 mL). To this was added 2 M aqueous potassium phosphate solution (17.6 mL, 35.2 mmol), and the mixture was stirred at 75°C for 15 hours. After allowing to cool to room temperature, the precipitated solid was collected by filtration. The resulting solid was washed with water (100 mL) and methanol (100 mL). This solid was suspended in toluene (500 mL), stirred at 100°C, and then allowed to cool. The precipitated solid was filtered and washed with toluene (40 mL) and methanol (30 mL), yielding the desired white solid of 4,6-diphenyl-2-[4'-{2-(1-naphthyl)pyridin-5-yl}-1,1'-biphenyl-4-yl]-1,3,5-triazine (Compound A-67) (yield: 5.38 g, 78%).

¹ H-NMR (CDCl ₃ ) δ (ppm): 9.14 (d, J = 2.2Hz, 1H), 8.92 (d, J = 8.6Hz, 2H), 8.84 (d, J = 8.1Hz, 4H), 8.22 (t, J = 3.9Hz, 1H), 8.14 (dd, J = 8.2Hz, 2.3 Hz, 1H), 7.94 (d, J = 8.2Hz, 2H), 7.93-7.86 (m, 6H), 7.73 (dd, J = 14.5Hz, 8.9Hz, 2H), 7.67-7.60 (m, 7H), 7.54 (t, J = 5.8Hz, 2H)

The structure of Compound A-67 was identified by ¹ H-NMR, but the glass transition temperature could not be determined because no clear peak was observed.
(Synthesis Example 2: Synthesis of A-70)

The same experimental procedure as in Synthesis Example 1 was performed, except that 5-chloro-2-(1-naphthyl)pyridine was replaced with 5-chloro-2-(phenanthrene-9-yl)pyridine. The desired 4,6-diphenyl-2-[4'-{2-(phenanthrene-9-yl)pyridin-5-yl}-1,1'-biphenyl-4-yl]-1,3,5-triazine (A-70) was obtained as a white solid (yield: 4.4 g, 53%).

¹ H-NMR (CDCl ₃ ) δ (ppm): 7.42-7.50 (m, 8H), 7.55 (t, J = 7.8Hz, 2H), 7.62 (d, J = 8.1H z, 1H), 7.68-7.75 (m, 6H), 7.78 (s, 1H), 7.80 (d, J=8.1Hz, 1H), 7.98 (dd, J=2.4Hz, 8.1Hz, 1H), 8.05 (d, J=8.3Hz, 1H), 8.59 (d, J=8.3Hz, 1H), 8.64-8.67 (m, 5H), 8.74 (d, J = 8.6Hz, 2H), 8.98 (d, J = 2.4Hz, 1H)

The structure of compound A-70 was identified by ¹ H-NMR, and the glass transition temperature was 119°C.
(Synthesis Example 3: Synthesis of A-91)

Under an argon stream, 2-[4-{(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl}]-4,6-diphenyl-1,3,5-triazine (1.31 g, 3.0 mmol), 1-chloro-4-{4-(naphthalen-1-yl)pyrimidin-2-yl}phenyl (1.14 g, 3.6 mmol), palladium acetate (20.4 mg, 0.09 mmol), and X-Phos (85.8 mg, 0.18 mmol) were dissolved in tetrahydrofuran (15 mL). To this was added 2 M aqueous potassium carbonate solution (18 mL, 36 mmol), and the mixture was stirred at 75°C for 18 hours. After allowing to cool to room temperature, the precipitated solid was filtered off. The resulting solid was washed with water (50 mL) and ethanol (50 mL). The resulting solid was dissolved in 50 mL of toluene. Activated carbon was added to the solution and stirred, then filtered through Celite. The filtrate was concentrated under reduced pressure. The concentrated solution was dried to obtain the desired white solid (yield: 1.38 g, 78%) of 4,6-diphenyl-2-[4'-{5-(naphthalen-1-yl)pyrimidin-2-yl}-1,1'-biphenyl-4-yl]1,3,5-triazine (A-91).

1H-NMR (CDCl3) δ (ppm): 7.46-7.67 (m, 12H), 7.92 (t, J = 8.2Hz, 2H), 7.99 (d, J = 7.6, 2H) , 8.69 (d, J=8.5Hz, 2H), 8.82 (dd, J=7.8, 4Hz, 4H), 8.90 (d, J=8.5Hz, 2H), 9.01 (s, 2H).

The structure of Compound A-91 was identified by ¹ H-NMR, and the glass transition temperature was 102°C.
(Synthesis Example 4: Synthesis of A-148)

Under an argon atmosphere, 2,4-bis[(1,1'-biphenyl)-4-yl]-6-[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-phenyl]-1,3,5-triazine (5.05 g, 8.6 mmol) (3.40 g, 5.8 mmol), 3-chloro-2-methyl-6-phenylpyridine (1.41 g, 6.9 mmol), palladium acetate (26.0 mg, 0.12 mmol), and X-Phos (110.0 mg, 0.23 mmol) were dissolved in tetrahydrofuran (58 mL). To this was added 2 M aqueous potassium carbonate solution (8.7 mL, 17 mmol), and the mixture was stirred at 75°C for 22 hours. After allowing to cool to room temperature, the precipitated solid was filtered off. The resulting solid was washed with water (100 mL) and ethanol (100 mL). The resulting solid was dissolved in 400 mL of toluene. Activated carbon was added to the solution and stirred, then filtered through Celite, and the filtrate was concentrated under reduced pressure. The concentrated liquid was dried to obtain the desired white solid (yield: 2.38 g, 65%) of 4,6-bis[(1,1'-biphenyl)-4-yl]-2-[(2-methyl-6-phenylpyridin-3-yl)-phenyl-4-yl]-1,3,5-triazine (A-148).

1H-NMR (CDCl3) δ (ppm): 7.34-7.40 (m, 6H), 6.57-6.53 (m, 2H), 6.34-6.28 (m, 4H), 6.25-5.88 (m, 17H), 1.11 (s, 3H).

The structure of compound A-148 was identified by ¹ H-NMR, and the glass transition temperature was 107°C.

Below are the measurement data for the crystallization temperature and melting point of the azine compound (1) prepared above.

The azine compound according to one embodiment of the present invention has a lower crystallization temperature and melting point than the following ETL-1 described in Patent Document 1.

<Fabrication of Organic Electric Field Element>

Next, the obtained compound was used to carry out 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 and surface treatment, each layer was deposited by vacuum deposition using the vacuum deposition method onto the substrate, forming a laminate of layers.

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 55 nm thick film to form a hole injection layer.
(Fabrication of First Hole Transport Layer 1051)

A 10 nm thick film of N-[1,1'-biphenyl]-4-yl-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine was formed at a rate of 0.15 nm/sec to form a first hole transport layer.
(Fabrication of Second Hole Transport Layer 1052)

A 10 nm thick film of N-phenyl-N-(9,9-diphenylfluoren-2-yl)-N-(1,1′-biphenyl-4-yl)amine was formed at a rate of 0.15 nm/sec to form a second hole transport layer.
(Fabrication of Light-Emitting Layer 106)

A 25 nm thick film was formed by mixing 3-(10-phenyl-9-anthryl)-dibenzofuran and 2,7-bis[N,N-di-(4-tertbutylphenyl)]amino-bisbenzofurano-9,9′-spirofluorene in a mass ratio of 95:5 to form a light-emitting layer. 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-triazine was deposited at a rate of 0.15 nm/sec to form a 5 nm film to form a first electron transport layer.
(Fabrication of Second Electron Transport Layer 1072)

A second electron-transporting layer was formed by depositing a 25 nm thick film using 4,6-diphenyl-2-[4'-{2-(1-naphthyl)pyridin-5-yl}-1,1'-biphenyl-4-yl]-1,3,5-triazine (Compound A-67) synthesized in Synthesis Example 1 and 8-hydroxyquinolinolatolithium (hereinafter, Liq) in a mass ratio of 50:50. The film deposition 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 the cathode 108 was deposited. The cathode had a two-layer structure, with silver/magnesium (mass ratio 1/10) and silver deposited in that order to thicknesses of 80 nm and 20 nm, respectively. The deposition rate for silver/magnesium was 0.5 nm/sec, and the deposition rate for silver 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 Co., Ltd.). As the light-emitting characteristics, the current efficiency (cd/A) when a current density of 10 mA/ ^cm2 was applied was measured.

The voltage and current efficiencies are relative values, with the result of Comparative Example Element 1 set as the reference value (100). The measurement results are shown in Table 2.
<Element Example 2>

An organic electroluminescent device was produced and evaluated in the same manner as in Element Example 1, except that compound (A-70) synthesized in Synthesis Example 2 was used instead of compound (A-65) in Element Example 1. The measurement results obtained are shown in Table 2.
<Element Example 3>

An organic electroluminescent device was produced and evaluated in the same manner as in Element Example 1, except that compound (A-91) synthesized in Synthesis Example 3 was used instead of compound (A-65) in Element Example 1. The measurement results obtained are shown in Table 2.
<Comparative element example 1>

An organic electroluminescent device was fabricated and evaluated in the same manner as in Element Example 1, except that 2,4-bis[(1,1'-biphenyl)-4-yl]-6-[4'-(4-pyridyl)1,1'-biphenyl-4-yl]-1,3,5-triazine (ETL-1), described in Patent Document 1, was used instead of compound (A-65). The measurement results obtained are shown in Table 2.

The cyclic azine compound (1) according to one embodiment of the present invention can provide an organic electroluminescent device with excellent driving voltage and luminous efficiency.

Furthermore, the cyclic azine compound (1) according to one embodiment of the present invention can be used as an electron transport material for organic electroluminescent devices, which contributes to the production of organic electroluminescent devices with low driving voltage and excellent luminous efficiency. Furthermore, the cyclic azine compound (1) can provide organic electroluminescent devices with low power consumption and high luminous efficiency.

100. Organic electroluminescent device

REFERENCE SIGNS LIST 1 substrate 2 anode 3 hole injection layer 4 hole transport layer 5 light emitting layer 6 electron transport layer 7 electron injection layer 8 cathode

101 Substrate 102 Anode 103 Hole injection layer 1051 First hole transport layer 1052 Second hole transport layer 106 Light emitting layer 1071 First electron transport layer 1072 Second electron transport layer 108 Cathode

Claims (4)

An azine compound represented by the following formula (1):
Formula (1)
During the ceremony,
Ar ¹ and Ar ² independently represent a phenyl group or a biphenyl group.
^Ar3 represents a phenyl group, a naphthyl group, or a phenanthrenyl group .
L1 represents a divalent 6-membered ^ring linking group .
The divalent 6-membered ring linking group is a 3,6-pyridylene group or a 2,5-pyrimidylene group which may be substituted with a methyl group.
ⁿ¹ represents an integer of 1 or 2 .
ⁿ² represents an integer of 0 or 1 . 2. The azine compound according to claim 1, wherein the divalent 6-membered ring linking group is a 3,6-pyridylene group or a 2,5-pyrimidylene group optionally substituted with a methyl group at the 2-position. A material for an organic electroluminescent device, comprising the azine compound according to claim 1 or 2 . An organic electroluminescent device comprising the azine compound according to claim 1 or 2 .