JP2022136017A - Aromatic compound - Google Patents

Abstract

To provide an aromatic compound having excellent thermostability, high solubility, and a large band gap.SOLUTION: An aromatic compound is represented by the following formula (1). (In the formula (1), Ar11-Ar14, R1-R4, n11-n14, and ma-md each have the same definitions as those in the specifications).SELECTED DRAWING: Figure 1

Description

The present invention provides an aromatic compound that can be used in an organic electroluminescent device (hereinafter sometimes referred to as "OLED" or "device"), an organic electroluminescent device having the compound, and the organic electroluminescent device. The present invention relates to a display device and a lighting device, a composition containing the compound and the solvent, a method for forming a thin film, and a method for manufacturing an organic electroluminescent device.

In recent years, as a thin-film type electroluminescence element, an organic electroluminescence element using an organic thin film has been developed in place of the one using an inorganic material. An organic electroluminescent device (OLED) typically has a hole-injection layer, a hole-transport layer, an organic light-emitting layer, an electron-transport layer, etc. between an anode and a cathode. Materials suitable for each of these layers are being developed, and the development of red, green, and blue emission colors is progressing. In addition, research is being conducted on coating-type OLEDs, which are more efficient in material utilization than conventional evaporation-type OLEDs and can reduce manufacturing costs.

Coating-type OLEDs are required to have a longer life and be driven with lower power consumption. There are various factors that can affect the life of an element and the improvement in power consumption, but with regard to life, for example, the thermal durability and crystallinity of the materials that make up the element are thought to have a major effect. .

Moreover, in order to manufacture an organic electroluminescence device by a wet film-forming method, all the materials used must be soluble in an organic solvent and used as an ink. If the material to be used has poor solubility, the material may deteriorate before use because an operation such as heating for a long period of time is required. Furthermore, if the uniform state cannot be maintained for a long time in a solution state, the material will precipitate out of the solution, making it impossible to form a film using an inkjet device or the like. Materials used in the wet film-forming method are required to have solubility in two senses: rapid dissolution in an organic solvent and maintenance of a homogeneous state without precipitating after dissolution.

In an organic electroluminescent element using an organic thin film composed of a plurality of low-molecular-weight materials formed by a wet film-forming method, Patent Document 1 describes an element utilizing phosphorescence emission in order to increase the luminous efficiency of the element. there is Biphenyl derivatives shown below are used for the charge transport material of the organic electroluminescence device described in Non-Patent Document 1.

Further, Patent Document 2 reports an OLED material using the following hydrocarbon compound as a charge transport material for a phosphorescent compound.

WO2015/014434 WO2007/043357

Japanese Journal of Applied Physics Vol.44,No.1B, 2005, pp.626-629

However, the compound described in Non-Patent Document 1 and the compound described in Patent Document 1 have an unnecessarily high charge transport property in the light-emitting layer, and the life of the organic electroluminescent device having the compound may be shortened. .

In addition, the compound described in Patent Document 2 has high solubility and a large bandgap, but has a low glass transition temperature of 87° C. and does not have sufficient heat resistance.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide an aromatic compound having excellent heat resistance, high solubility, and a large bandgap.

The present invention also provides an organic electroluminescent device containing the compound, a display device and a lighting device comprising the organic electroluminescent device, a composition containing the compound and a solvent, a method for forming a thin film, and a method for manufacturing an organic electroluminescent device. The task is to provide

As a result of intensive studies by the present inventors, it was found that by using an aromatic compound having a specific structure containing a tetraphenylene structure, the aromatic compound has excellent heat resistance, high solubility, and a large bandgap. We have found that and arrived at the present invention.

That is, the gist of the present invention resides in the following <1> to <14>.
<1> An aromatic compound represented by the following formula (1).

(In formula (1),
Ar ¹¹ to Ar ¹⁴ each independently represent the following formula (2),
R ¹ to R ⁴ each independently represent a substituent,
n11 is an integer from 1 to 4,
n12 to n14 are each independently an integer of 0 to 3,
The sum of n11 to n14 is 4 or less,
ma to md are each independently an integer of 0 to 4; )

(In formula (2),
The asterisk (*) represents a bond with formula (1),
L ¹ and L ² each independently represent an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms, or an optionally substituted divalent carbon atom of 30 or less or an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms and an optionally substituted divalent heteroaromatic group having 30 or less carbon atoms is a group in which a plurality of groups selected from groups are linked,
Ar ² is each independently an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms, or an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms or an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms and an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms is a group in which a plurality of groups are linked,
each R ⁵ independently represents a substituent,
a and b each independently represents an integer of 0 to 5,
me represents an integer of 0 to 4; )
<2> The aromatic compound according to <1>, wherein in formula (2), Ar ² is represented by any one of formulas (3) to (5) below.

(In formulas (3) to (5),
The asterisk (*) represents a bond with formula (2),
R ⁶ to R ⁴⁴ each independently represent a hydrogen atom or a substituent,
Adjacent R ⁶ to R ⁴⁴ may combine with each other to form a condensed ring. )
<3> The aromatic compound according to <2>, wherein the substituents that L ¹ and L ² may have and the substituents in R ¹ to R ⁴⁴ are each independently an aromatic hydrocarbon group.
<4> The aromatic compound according to <2> or <3>, wherein in formula (2), Ar ² is represented by formula (3) or (4).
<5> The aromatic compound according to any one of <1> to <4>, wherein in formula (2), L ¹ is not a condensed ring.
<6> An organic electroluminescence device having an anode and a cathode on a substrate and an organic layer between the anode and the cathode,
The organic layer has a layer containing an organic electroluminescence device material,
An organic electroluminescent device, wherein the organic electroluminescent device material is the aromatic compound according to any one of <1> to <5>.
<7> The organic electroluminescence device according to <6>, wherein the layer containing the material for an organic electroluminescence device is a light-emitting layer.
<8> the light-emitting layer comprises the aromatic compound according to any one of <1> to <5>, a charge transport material, and a light-emitting material;
The organic electroluminescence device according to <7>, wherein the content of the aromatic compound is 0.1% by mass or more and 50% by mass or less with respect to the total amount of the aromatic compound and the charge transport material.
<9> A display device comprising the organic electroluminescence device according to any one of <6> to <8>.
<10> A lighting device comprising the organic electroluminescent element according to any one of <6> to <8>.
<11> A composition for an organic electroluminescence device, comprising the aromatic compound according to any one of <1> to <5> and a solvent.
<12> The composition for an organic electroluminescence device according to <11>, further comprising a phosphorescent material and a charge-transporting material.
<13> A method for forming a thin film, comprising forming a film from the composition for an organic electroluminescence device according to <11> or <12> by a wet film-forming method.
<14> A method for producing an organic electroluminescence device having an anode and a cathode on a substrate and an organic layer between the anode and the cathode,
A method for producing an organic electroluminescent device, comprising forming the organic layer by a wet film-forming method using the composition for an organic electroluminescent device according to <11> or <12>.
<15> The method for producing an organic electroluminescent device according to <14>, wherein the organic layer is a light-emitting layer.

INDUSTRIAL APPLICABILITY According to the present invention, an aromatic compound having excellent heat resistance, high solubility, and a large bandgap can be provided.

In addition, according to the present invention, an organic electroluminescent device having the compound, a display device and a lighting device having the organic electroluminescent device, a composition containing the compound and a solvent, a method for forming a thin film, and a method for manufacturing an organic electroluminescent device are provided. can provide.

FIG. 1 is a cross-sectional view schematically showing an example of the structure of the organic electroluminescence device of the present invention.

Embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be modified in various ways within the scope of the gist thereof.

In the present invention, "optionally having a substituent" means that one or more substituents may be present.

<Aromatic compound of the present invention>
The aromatic compound of the present invention is an aromatic compound characterized by having a structure containing a tetraphenylene structure represented by the following formula (1).

(In formula (1),
Ar ¹¹ to Ar ¹⁴ each independently represent the following formula (2),
R ¹ to R ⁴ each independently represent a substituent,
n11 is an integer from 1 to 4,
n12 to n14 are each independently an integer of 0 to 3,
The sum of n11 to n14 is 4 or less,
ma to md are each independently an integer of 0 to 4; )

(In formula (2),
The asterisk (*) represents a bond with formula (1),
L ¹ and L ² each independently represent an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms, or an optionally substituted divalent carbon atom of 30 or less or an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms and an optionally substituted divalent heteroaromatic group having 30 or less carbon atoms is a group in which a plurality of groups selected from groups are linked,
Ar ² is each independently an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms, or an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms or an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms and an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms is a group in which a plurality of groups are linked,
each R ⁵ independently represents a substituent,
a and b each independently represents an integer of 0 to 5,
me represents an integer of 0 to 4; )

In the present invention, the action mechanism by which effective effects are obtained is presumed as follows.

Since the aromatic compound of the present invention has a condensed ring structure of tetraphenylene represented by formula (1), it has a high glass transition temperature.

In addition, since the aromatic compound of the present invention has one or more meta-bonded aromatic hydrocarbon groups or heteroaromatic groups as represented by formula (2), the spread of the π-conjugated system is suppressed, the bandgap is large, and the excited triplet energy level (T1) is high.

Furthermore, as represented by formula (2), the aromatic compound of the present invention has reduced intermolecular interaction due to steric hindrance due to the meta-position bond of the aromatic hydrocarbon group or heteroaromatic group, resulting in reduced solubility. High and low crystallinity.

By using the tetraphenylene structure represented by the formula (1) to improve the glass transition temperature, it is considered that both the effect of increasing the bandgap and the heat resistance can be achieved.

In addition, since the tetraphenylene structure represented by formula (1) has the structure represented by formula (2), HOMO and LUMO are difficult to ride on the tetraphenylene structure represented by formula (1), so durability is improved. can be improved.

Using the aromatic compound of the present invention, it is possible to easily provide an organic electroluminescence device that is excellent in driving stability and that can be driven with a low driving voltage and high efficiency.

The organic electroluminescent device of the present invention containing the aromatic compound of the present invention has excellent electrochemical stability, low driving voltage and high efficiency. Therefore, the organic electroluminescence device of the present invention can be used as a flat panel display (for example, an OA computer display or a wall-mounted TV), an in-vehicle display device, a mobile phone display, or a light source (for example, a copier (light sources for liquid crystal displays and instruments, backlight sources for instruments), display boards, and indicator lamps, and their technical value is great.

<Ar ¹¹ to Ar ¹⁴ >
Ar ¹¹ to Ar ¹⁴ are each independently represented by formula (2). Ar ¹¹ to Ar ¹⁴ may be bonded to the tetraphenylene structure at any point, preferably the 2-position carbon from the viewpoint of stability.

<n11 to n14>
n11 is an integer from 1 to 4,
n12 to n14 are each independently an integer of 0 to 3,
The sum of n11 to n14 is 4 or less.

When the sum of n11 to n14 is 2 or more, the binding sites of Ar ¹¹ to Ar ¹⁴ to the tetraphenylene structure are 2-, 3-, 6-, 7-, 10-, 11- and 14-positions from the viewpoint of stability. It is preferably selected from 15-position and 15-position carbons.

From the viewpoint of solubility and durability of the compound, n11 is preferably 3 or less, more preferably 2 or less, and particularly preferably 1.

When the sum of n11 to n14 is 2 or more, a plurality of Ar ¹¹ to Ar ¹⁴ may be the same or different.

Further, when the sum of n11 to n14 is 2 or more, the structures represented by formula (2), which are present in plurality, may be the same or different. In other words, when the sum of n11 to n14 is 2 or more, a plurality of Ar ² , R ⁵ , L ¹ , L ² , a, b and me may be the same or different.

<R ¹ to R ⁴ >
R ¹ to R ⁴ each independently represent a substituent. As the substituent, those selected from the substituent group Z described later can be used. From the viewpoint of heat resistance and durability, R ¹ to R ⁴ are preferably an alkyl group, an alkoxy group, an aralkyl group, or an aromatic hydrocarbon group. Group hydrocarbon groups are particularly preferred. Among these, aromatic hydrocarbon groups are most preferred, and aromatic hydrocarbon groups having 30 or less carbon atoms are more preferred.

<ma to md>
ma to md are each independently an integer of 0 to 4; ma to md are preferably 3 or less, more preferably 2 or less, particularly preferably 1, and most preferably 0, from the viewpoint of solubility and durability of the compound.

When ma to md are 2 or more, a plurality of R ¹ to R ⁴ may be the same or different.

< ^Ar2 >
Ar ² is each independently an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms, or an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms or an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms and an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms represents a group in which multiple groups are linked.

Examples of monovalent aromatic hydrocarbon groups having 60 or less carbon atoms include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, tetraphenylene ring, chrysene ring, pyrene ring, benzanthracene ring, perylene ring, biphenyl ring, or a monovalent group of a terphenyl ring.

Examples of monovalent heteroaromatic groups having 60 or less carbon atoms include furan ring, benzofuran ring, dibenzofuran ring, thiophene ring, benzothiophene ring, dibenzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring , pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, cinnoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring or azulene ring.

As the substituent, those selected from the substituent group Z described later can be used.

< ^L1 , ^L2 >
L ¹ and L ² each independently represent an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms, or an optionally substituted divalent carbon atom of 30 or less or an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms and an optionally substituted divalent heteroaromatic group having 30 or less carbon atoms represents a group in which a plurality of groups selected from groups are linked;

Examples of divalent aromatic hydrocarbon groups having 30 or less carbon atoms include divalent benzene ring, naphthalene ring, anthracene ring, tetraphenylene ring, phenanthrene ring, chrysene ring, pyrene ring, benzanthracene ring, or perylene ring. group.

Examples of divalent heteroaromatic groups having 30 or less carbon atoms include furan ring, benzofuran ring, dibenzofuran ring, thiophene ring, benzothiophene ring, dibenzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring , pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, cinnoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring or azulene ring.

As the substituent, those selected from the group of substituents Z described later can be used, and an aromatic hydrocarbon group is particularly preferred.

L ¹ and L ² are preferably a divalent group of a benzene ring or a naphthalene ring, more preferably a divalent group of a benzene ring, from the viewpoint of compound solubility and durability.

Also, L1 is preferably not ^a condensed ring because of the bandgap and the size of the T1 level.

<a, b>
a and b each independently represents an integer of 0 to 5;
From the viewpoint of solubility and durability of the compound, a is preferably 1 or more, preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less.

b is preferably 4 or less, more preferably 3 or less, even more preferably 2 or less, particularly preferably 1 or less, and most preferably 0, from the viewpoint of the solubility and durability of the compound.

When a is 2 or more, multiple L ^1s may be the same or different. When b is 2 or more, multiple L ² may be the same or different.

< ^R5 >
Each ^R5 independently represents a substituent. As the substituent, those selected from the substituent group Z described later can be used. From the viewpoint of heat resistance and durability, an alkyl group, an alkoxy group, an aralkyl group, and an aromatic hydrocarbon group are preferable, and an alkyl group having 10 or less carbon atoms, an aralkyl group having 30 or less carbon atoms, and an aromatic hydrocarbon group are more preferable. . Among these, an aromatic hydrocarbon group is most preferred, an aromatic hydrocarbon group having 30 or less carbon atoms is more preferred, and a benzene ring or a group having 2 to 5 linked benzene rings is particularly preferred.

<me>
me represents an integer of 0 to 4; me is preferably 0 or 1, most preferably 1, from the viewpoint of solubility and durability of the compound.

When me is 2 or more, multiple R5 may be the ^same or different.

From the viewpoint of durability of the compound, Ar ² in formula (2) is preferably represented by any one of formulas (3) to (5) below.

Among these, the following formula (3) or the following formula (4) is more preferable in order to cut conjugation and increase the bandgap, and the following formula (4) is more preferable from the viewpoint of stability.

(In formulas (3) to (5),
The asterisk (*) represents a bond with formula (2),
R ⁶ to R ⁴⁴ each independently represent a hydrogen atom or a substituent,
Adjacent R ⁶ to R ⁴⁴ may combine with each other to form a condensed ring. )

< ^{R6 to R44 >}
R ⁶ to R ⁴⁴ each independently represent a hydrogen atom or a substituent, and adjacent R ⁶ to R ⁴⁴ may combine with each other to form a condensed ring. As the substituent, those selected from the substituent group Z described later can be used. From the viewpoint of durability, R ⁶ to R ⁴⁴ are preferably a hydrogen atom, an aromatic hydrocarbon group or a heteroaromatic group, more preferably an aromatic hydrocarbon group or a hydrogen atom.

Examples of structures in which adjacent R ⁶ to R ⁴⁴ are bonded together to form a condensed ring include carbazole, dibenzofuran, dibenzothiophene, fluorene, and spirobifluorene. R ⁶ to R ⁴⁴ preferably do not form a condensed ring from the viewpoint of bandgap.

[Substituent group Z]
Substituent group Z includes an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, and a cyano group. , an aralkyl group, an aromatic hydrocarbon group, or a heteroaromatic group.

The alkyl group includes, for example, a methyl group, an ethyl group, a branched, straight-chain or cyclic propyl group, a branched, straight-chain or cyclic butyl group, a branched, straight-chain or cyclic pentyl group, a branched, straight-chain or cyclic A hexyl group, a branched, straight-chain or cyclic octyl group, a branched, straight-chain or cyclic nonyl group, a branched, straight-chain or cyclic dodecyl group, etc., usually having 1 or more carbon atoms, preferably 4 or more, and usually Linear, branched or cyclic alkyl groups with 24 or less, preferably 10 or less are mentioned. From the viewpoint of compound stability, a methyl group, an ethyl group, a branched, linear or cyclic propyl group, and a branched, linear or cyclic butyl group are preferred, and a branched propyl group is particularly preferred.

Examples of alkenyl groups include alkenyl groups having usually 2 or more carbon atoms and usually 24 or less carbon atoms, preferably 12 or less carbon atoms such as vinyl groups.

Examples of alkynyl groups include alkynyl groups having usually 2 or more carbon atoms and usually 24 or less, preferably 12 or less carbon atoms such as ethynyl groups.

Examples of alkoxy groups include alkoxy groups having usually 1 or more carbon atoms and usually 24 or less, preferably 12 or less carbon atoms such as methoxy and ethoxy groups.

The aryloxy group includes, for example, an aryloxy group or heteroaryl having usually 4 or more, preferably 5 or more carbon atoms and usually 36 or less, preferably 24 or less, such as phenoxy group, naphthoxy group, pyridyloxy group, etc. An oxy group can be mentioned.

Examples of alkoxycarbonyl groups include alkoxycarbonyl groups having usually 2 or more carbon atoms and usually 24 or less, preferably 12 or less carbon atoms such as methoxycarbonyl and ethoxycarbonyl groups.

The acyl group includes, for example, an acyl group having usually 2 or more carbon atoms and usually 24 or less, preferably 12 or less carbon atoms such as acetyl group and benzoyl group.

Halogen atoms include, for example, halogen atoms such as fluorine and chlorine atoms.

The haloalkyl group includes, for example, a haloalkyl group having usually 1 or more carbon atoms and usually 12 or less, preferably 6 or less carbon atoms such as a trifluoromethyl group.

Examples of alkylthio groups include alkylthio groups having usually 1 or more carbon atoms and usually 24 or less, preferably 12 or less carbon atoms such as methylthio and ethylthio groups.

Examples of the arylthio group include arylthio groups having usually 4 or more, preferably 5 or more carbon atoms and usually 36 or less, preferably 24 or less carbon atoms such as phenylthio, naphthylthio and pyridylthio groups.

Silyl groups include, for example, silyl groups having usually 2 or more, preferably 3 or more carbon atoms and usually 36 or less, preferably 24 or less carbon atoms such as trimethylsilyl and triphenylsilyl groups.

Siloxy groups include, for example, siloxy groups having usually 2 or more, preferably 3 or more carbon atoms and usually 36 or less, preferably 24 or less carbon atoms such as trimethylsiloxy and triphenylsiloxy groups.

Examples of aralkyl groups include benzyl, 2-phenylethyl, 2-phenylpropyl-2-yl, 2-phenylbutyl-2-yl, 3-phenylpentyl-3-yl, 3-phenyl- 1-propyl group, 4-phenyl-1-butyl group, 5-phenyl-1-pentyl group, 6-phenyl-1-hexyl group, 7-phenyl-1-heptyl group, 8-phenyl-1-octyl group, etc. and an aralkyl group having usually 7 or more, preferably 9 or more carbon atoms and usually 30 or less, preferably 18 or less, more preferably 10 or less carbon atoms.

Examples of the aromatic hydrocarbon group include, for example, benzene ring, naphthalene ring, anthracene ring, tetraphenylene ring, phenanthrene ring, chrysene ring, pyrene ring, benzanthracene ring, or perylene ring. An aromatic hydrocarbon group having a number of 30 or less, preferably 18 or less, more preferably 10 or less can be mentioned.

Examples of heteroaromatic groups include furan ring, benzofuran ring, dibenzofuran ring, thiophene ring, benzothiophene ring, dibenzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, pyrrolo imidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring, A pyrimidine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a cinnoline ring, a quinoxaline ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, or an azulene ring having usually 4 or more carbon atoms, usually 30 or less, preferably 18 or less, and further Heteroaromatic groups, preferably 12 or less, are mentioned.

Further, each substituent in the substituent group Z may further have a substituent. As such additional substituents, the same substituents as those described above (substituent group Z) can be used.

<Specific example>
Specific examples of the aromatic compound of the invention are shown below, but the invention is not limited thereto.

<Method for producing aromatic compound>
The aromatic compound of the present invention can be produced, for example, according to the method described in Examples.

<Uses of aromatic compounds>
The aromatic compound of the present invention can be suitably used as a material used in organic electroluminescent devices, that is, as a host material in organic electroluminescent devices, and can also be suitably used as a charge-transporting material in other light-emitting devices. is.

In particular, the aromatic compound of the present invention has a tetraphenylene structure as a basic skeleton and has one or more meta-bonded aromatic hydrocarbon groups or heteroaromatic groups. By having a tetraphenylene structure, the glass transition temperature is high and the heat resistance is high. Having one or more meta-bonded aromatic hydrocarbon groups or heteroaromatic groups suppresses the spread of the π-conjugated system. Furthermore, it is believed that the meta-bonding of the aromatic hydrocarbon group or the heteroaromatic group improves the solubility and reduces the crystallinity.

Therefore, the aromatic compound of the present invention has high solubility, a large bandgap (difference between HOMO and LUMO), and a high excited triplet level (T1). , particularly useful as a host material for phosphorescent materials.

In particular, the aromatic compound of the present invention can be used for the production of an organic electroluminescent device by a vacuum deposition method, and can also be used for thin film formation by a wet film formation method. It is also suitable as a material for electroluminescence devices.

Therefore, if it is possible to manufacture an organic electroluminescent device by vacuum deposition using the material for organic electroluminescent devices comprising the aromatic compound of the present invention, the composition for organic electroluminescent devices containing the aromatic compound of the present invention can be used. Alternatively, an organic electroluminescence device can be manufactured by a wet film-forming method.
The obtained organic electroluminescence device has excellent driving stability and can be driven with a low driving voltage and high efficiency.

Moreover, the glass transition temperature of the aromatic compound of the present invention is preferably 125° C. or higher, more preferably 130° C. or higher, and even more preferably 140° C. or higher, from the viewpoint of heat resistance.

<Materials for Organic Electroluminescent Devices>
The material for an organic electroluminescence device of the present invention comprises the aromatic compound of the present invention, and preferably dissolves in cyclohexylbenzene or toluene in an amount of 2% by mass or more, more preferably cyclohexylbenzene or toluene. It dissolves at least 5% by mass with respect to

As will be described later, aromatic hydrocarbons are preferred as the solvent contained in the composition for organic electroluminescence devices. Cyclohexylbenzene and toluene are typical examples of aromatic hydrocarbons, and the solubility in cyclohexylbenzene or toluene is used as an indicator of the solubility of materials for organic electroluminescence devices.

When the solubility in cyclohexylbenzene or toluene of the material for an organic electroluminescence device of the present invention is 2% by mass or more, the layers constituting the organic electroluminescence device can be easily formed by a wet film-forming method, which is preferable. . Although the upper limit of the solubility is not particularly limited, it is usually about 50% by mass.

<Composition for organic electroluminescence device>
The composition for organic electroluminescence elements of the present invention usually contains the aromatic compound and solvent of the present invention, and preferably further contains a luminescent material and a charge transport material.

[1] Solvent The solvent contained in the composition for organic electroluminescence elements of the present invention is not particularly limited as long as it is a solvent in which the aromatic compound or the like of the present invention, which is a solute, dissolves satisfactorily.

Since the aromatic compound of the present invention has high solubility, various solvents are applicable. For example, aromatic hydrocarbons such as toluene, xylene, methylene, cyclohexylbenzene, tetralin; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, trichlorobenzene; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole aromatic ethers; phenyl acetate, phenyl propionate, methyl benzoate, benzoic acid aromatic esters such as ethyl, propyl benzoate and n-butyl benzoate; ketones having an alicyclic ring such as cyclohexanone and cyclooctanone; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; aliphatic alcohols such as butanol and hexanol; aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); ethyl acetate, n-butyl acetate, ethyl lactate, Aliphatic esters such as n-butyl lactate can be used. Among these, aromatic hydrocarbons such as toluene, xylene, methysylene, cyclohexylbenzene, and tetralin are preferable because they have low solubility in water and are not easily degraded.

Since organic electroluminescence elements use many materials such as cathodes that are significantly deteriorated by moisture, the presence of moisture in the composition for organic electroluminescence elements of the present invention may cause moisture to remain in the film after drying. However, it is not preferable because there is a possibility of degrading the characteristics of the device.

Methods for reducing the amount of water in the composition for organic electroluminescent elements of the present invention include, for example, a method of using a nitrogen gas seal, a method of using a desiccant, a method of preliminarily dehydrating a solvent, and a method having low water solubility. A method using a solvent and the like can be mentioned. Among them, the method of using a solvent with low water solubility is preferable because it can prevent the solution film from whitening due to absorption of moisture in the air during the wet film formation process.

From such a point of view, the composition for an organic electroluminescence element of the present invention includes, for example, a solvent having a solubility in water at 25° C. of 1% by mass or less, preferably 0.1% by mass or less. It is preferably contained in an amount of 10% by mass or more in the composition for an electroluminescence device.

Further, in order to reduce the deterioration of film formation stability due to solvent evaporation from the composition for organic electroluminescence elements of the present invention during wet film formation, the solvent for the composition for organic electroluminescence elements of the present invention is: It is effective to use a solvent having a boiling point of 100° C. or higher, preferably 150° C. or higher, more preferably 200° C. or higher.

In order to obtain a more uniform film, it is necessary to evaporate the solvent from the liquid film immediately after film formation at an appropriate rate. More preferably, it is effective to use a solvent having a boiling point of 120°C or higher and usually a boiling point of lower than 270°C, preferably lower than 250°C, and more preferably lower than 230°C.

Solvents that satisfy the above-mentioned conditions, ie, solute solubility, evaporation rate, and water solubility, may be used alone, or two or more solvents may be mixed and used.

[2] Luminescent Material The composition for organic electroluminescence elements of the present invention preferably further contains a luminescent material. A luminescent material refers to a component that mainly emits light in the composition for an organic electroluminescent element of the present invention, and corresponds to a dopant component in an organic electroluminescent device. That is, it is usually 10 to 100%, preferably 20 to 100%, more preferably 50 to 100%, most preferably 50 to 100% of the amount of light (unit: cd/m ² ) emitted from the composition for organic electroluminescent elements of the present invention. defines a luminescent material if 80-100% of the emission is identified as coming from a certain component material.

As the light-emitting material, a known material can be applied, and a fluorescent light-emitting material or a phosphorescent light-emitting material can be used singly or in combination. From the viewpoint of internal quantum efficiency, the phosphorescent light-emitting material is preferable.

When used in the composition for organic electroluminescent elements of the present invention, the maximum emission peak wavelength of this luminescent material is preferably in the range of 390 to 490 nm.

For the purpose of improving the solubility in solvents, it is also important to lower the symmetry and rigidity of the light-emitting material molecules, or to introduce lipophilic substituents such as alkyl groups.

Fluorescent dyes that emit blue light (blue fluorescent dyes) include perylene, pyrene, anthracene, coumarin, p-bis(2-phenylethenyl)benzene and derivatives thereof.

A quinacridone derivative, a coumarin derivative, etc. are mentioned as a fluorescent dye (green fluorescent dye) which gives green light emission.

Examples of fluorescent dyes that emit yellow light (yellow fluorescent dyes) include rubrene and perimidone derivatives.

Fluorescent dyes that emit red light (red fluorescent dyes) include DCM compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthenes, and the like.

(Phosphorescent material)
A phosphorescent material is a material that emits light from an excited triplet state. For example, metal complex compounds containing Ir, Pt, Eu, etc. are typical examples, and materials containing metal complexes are preferable as the structure of the material.

Among metal complexes, the long-period periodic table (unless otherwise specified, the long-period periodic table ) include Werner-type complexes or organometallic complex compounds containing a metal selected from Groups 7 to 11 as a central metal. As such a phosphorescent material, a compound represented by the following formula (201) or a compound represented by the following formula (205) is preferable, and a compound represented by the following formula (201) is more preferable.

M is a metal selected from Groups 7 to 11 of the periodic table, such as ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, gold, and europium.

Ring A1 represents an optionally substituted aromatic hydrocarbon ring structure or an optionally substituted aromatic heterocyclic ring structure.

Ring A2 represents an aromatic heterocyclic structure optionally having a substituent.

R ²⁰¹ and R ²⁰² each independently represent a structure represented by formula (202) above, and "*" represents bonding to ring A1 or ring A2. R ²⁰¹ and R ²⁰² may be the same or different, and when multiple R ²⁰¹ and R ²⁰² are present, they may be the same or different.

Ar ²⁰¹ and Ar ²⁰³ each independently represent an optionally substituted aromatic hydrocarbon ring structure or an optionally substituted aromatic heterocyclic ring structure.

Ar ²⁰² is an optionally substituted aromatic hydrocarbon ring structure, an optionally substituted aromatic heterocyclic ring structure, or an optionally substituted aliphatic hydrocarbon structure represents

The substituents bonded to ring A1, the substituents bonded to ring A2, or the substituents bonded to ring A1 and the substituents bonded to ring A2 may be bonded to each other to form a ring.

B ²⁰¹ -L ²⁰⁰ -B ²⁰² represents an anionic bidentate ligand. B ²⁰¹ and B ²⁰² each independently represent a carbon atom, an oxygen atom or a nitrogen atom, and these atoms may be atoms constituting a ring. L ²⁰⁰ represents a single bond or an atomic group forming a bidentate ligand together with B ²⁰¹ and B ²⁰² . When there are multiple groups of B ²⁰¹ -L ²⁰⁰ -B ²⁰² , they may be the same or different.

i1 and i2 each independently represent an integer of 0 or more and 12 or less.
i3 is an integer greater than or equal to 0 up to the number that can be substituted for Ar ²⁰² .
j is an integer greater than or equal to 0 up to the number that can be substituted for Ar ²⁰¹ .
k1 and k2 are each independently an integer of 0 or more, with the upper limit being the number that can be substituted on ring A1 and ring A2.
m is an integer of 1-3.

The aromatic hydrocarbon ring for ring A1 is preferably an aromatic hydrocarbon ring having 6 to 30 carbon atoms, and specifically includes a benzene ring, naphthalene ring, anthracene ring, triphenylyl ring, acenaphthene ring, fluoranthene ring, A fluorene ring is preferred.

The aromatic heterocyclic ring in ring A1 is preferably an aromatic heterocyclic ring having 3 to 30 carbon atoms containing any one of a nitrogen atom, an oxygen atom, or a sulfur atom as a heteroatom, more preferably a furan ring or a benzofuran ring. , thiophene ring, and benzothiophene ring.

Ring A1 is more preferably a benzene ring, a naphthalene ring or a fluorene ring, particularly preferably a benzene ring or a fluorene ring, most preferably a benzene ring.

The aromatic heterocyclic ring in ring A2 is preferably an aromatic heterocyclic ring having 3 to 30 carbon atoms containing either a nitrogen atom, an oxygen atom, or a sulfur atom as a heteroatom,
Specifically, pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, imidazole ring, oxazole ring, thiazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinoxaline ring, quinazoline ring, Naphthyridine ring, phenanthridine ring,
More preferred are pyridine ring, pyrazine ring, pyrimidine ring, imidazole ring, benzothiazole ring, benzoxazole ring, quinoline ring, isoquinoline ring, quinoxaline ring and quinazoline ring,
More preferred are pyridine ring, imidazole ring, benzothiazole ring, quinoline ring, isoquinoline ring, quinoxaline ring and quinazoline ring,
Most preferred are pyridine ring, imidazole ring, benzothiazole ring, quinoline ring, quinoxaline ring and quinazoline ring.

A preferred combination of ring A1 and ring A2 is represented by (ring A1-ring A2),
(benzene ring-pyridine ring), (benzene ring-quinoline ring), (benzene ring-quinoxaline ring), (benzene ring-quinazoline ring), (benzene ring-imidazole ring), (benzene ring-benzothiazole ring) .

The substituents that the ring A1 and the ring A2 may have can be optionally selected, but are preferably one or more substituents selected from the group S of substituents described below.

When any of Ar ²⁰¹ , Ar ²⁰² and Ar ²⁰³ is an optionally substituted aromatic hydrocarbon ring structure,
The aromatic hydrocarbon ring structure is preferably an aromatic hydrocarbon ring having 6 to 30 carbon atoms,
Specifically, benzene ring, naphthalene ring, anthracene ring, triphenylyl ring, acenaphthene ring, fluoranthene ring, and fluorene ring are preferred.
More preferably, a benzene ring, a naphthalene ring, or a fluorene ring,
A benzene ring is most preferred.

When any of Ar ²⁰¹ , Ar ²⁰² and Ar ²⁰³ is a fluorene ring optionally having a substituent, the 9- and 9′-positions of the fluorene ring have a substituent or are bonded to the adjacent structure. preferably.

When any one of Ar ²⁰¹ , Ar ²⁰² and Ar ²⁰³ is a benzene ring optionally having a substituent, at least one benzene ring is preferably bonded to the adjacent structure at the ortho- or meta-position. , more preferably, at least one benzene ring is attached to the adjacent structure at the meta position.

When any of Ar ²⁰¹ , Ar ²⁰² and Ar ²⁰³ is an aromatic heterocyclic structure optionally having a substituent,
The aromatic heterocyclic ring structure is preferably an aromatic heterocyclic ring having 3 to 30 carbon atoms containing either a nitrogen atom, an oxygen atom, or a sulfur atom as a heteroatom,
Specifically, pyridine ring, pyrimidine ring, pyrazine ring, triazine ring, imidazole ring, oxazole ring, thiazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinoxaline ring, quinazoline ring, naphthyridine ring, phenanthridine ring, carbazole ring, dibenzofuran ring, dibenzothiophene ring,
More preferred are pyridine ring, pyrimidine ring, triazine ring, carbazole ring, dibenzofuran ring and dibenzothiophene ring.

When any of Ar ²⁰¹ , Ar ²⁰² and Ar ²⁰³ is a carbazole ring optionally having a substituent, the N-position of the carbazole ring may have a substituent or be bonded to an adjacent structure. preferable.

When Ar ²⁰² is an optionally substituted aliphatic hydrocarbon structure,
The aliphatic hydrocarbon structure is an aliphatic hydrocarbon structure having a linear, branched, or cyclic structure,
preferably an aliphatic hydrocarbon having 1 to 24 carbon atoms,
more preferably aliphatic hydrocarbons having 1 to 12 carbon atoms,
More preferred are aliphatic hydrocarbons having 1 to 8 carbon atoms.

i1 and i2 are each independently preferably an integer of 1-12, more preferably an integer of 1-8, more preferably an integer of 1-6. Within this range, improved solubility and improved charge transport properties can be expected.

i3 preferably represents an integer of 0-5, more preferably an integer of 0-2, more preferably 0 or 1.

j preferably represents an integer of 0 to 2, more preferably 0 or 1;

k1 and k2 preferably represent an integer of 0 to 3, more preferably an integer of 1 to 3, more preferably 1 or 2, and particularly preferably 1.

The substituents that Ar ²⁰¹ , Ar ²⁰² and Ar ²⁰³ may have can be arbitrarily selected, but are preferably one or more substituents selected from the group S of substituents described later, more preferably hydrogen It is an atom, an alkyl group or an aryl group, particularly preferably a hydrogen atom or an alkyl group, most preferably unsubstituted (hydrogen atom).

Unless otherwise specified, the substituent is preferably a group selected from the following substituent group S.

<Substituent group S>
- an alkyl group, preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 6 carbon atoms .
- An alkoxy group, preferably an alkoxy group having 1 to 20 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, and still more preferably an alkoxy group having 1 to 6 carbon atoms.
- an aryloxy group, preferably an aryloxy group having 6 to 20 carbon atoms, more preferably an aryloxy group having 6 to 14 carbon atoms, still more preferably an aryloxy group having 6 to 12 carbon atoms, particularly preferably an aryloxy group having 6 carbon atoms; aryloxy group;
- A heteroaryloxy group, preferably a heteroaryloxy group having 3 to 20 carbon atoms, more preferably a heteroaryloxy group having 3 to 12 carbon atoms.
- an alkylamino group, preferably an alkylamino group having 1 to 20 carbon atoms, more preferably an alkylamino group having 1 to 12 carbon atoms;
- An arylamino group, preferably an arylamino group having 6 to 36 carbon atoms, more preferably an arylamino group having 6 to 24 carbon atoms.
- An aralkyl group, preferably an aralkyl group having 7 to 40 carbon atoms, more preferably an aralkyl group having 7 to 18 carbon atoms, and still more preferably an aralkyl group having 7 to 12 carbon atoms.
- heteroaralkyl group, preferably heteroaralkyl group having 7 to 40 carbon atoms, more preferably heteroaralkyl group having 7 to 18 carbon atoms, - alkenyl group, preferably alkenyl group having 2 to 20 carbon atoms, more preferably carbon number An alkenyl group having 2 to 12 carbon atoms, more preferably an alkenyl group having 2 to 8 carbon atoms, particularly preferably an alkenyl group having 2 to 6 carbon atoms.
- an alkynyl group, preferably an alkynyl group having 2 to 20 carbon atoms, more preferably an alkynyl group having 2 to 12 carbon atoms;
- An aryl group, preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 24 carbon atoms, still more preferably an aryl group having 6 to 18 carbon atoms, particularly preferably an aryl group having 6 to 14 carbon atoms .
- a heteroaryl group, preferably a heteroaryl group having 3 to 30 carbon atoms, more preferably a heteroaryl group having 3 to 24 carbon atoms, still more preferably a heteroaryl group having 3 to 18 carbon atoms, particularly preferably 3 to 3 carbon atoms 14 heteroaryl groups.
An alkylsilyl group, preferably an alkylsilyl group having 1 to 20 carbon atoms, more preferably an alkylsilyl group having 1 to 12 carbon atoms.
- An arylsilyl group, preferably an arylsilyl group in which the aryl group has 6 to 20 carbon atoms, more preferably an arylsilyl group in which the aryl group has 6 to 14 carbon atoms.
- an alkylcarbonyl group, preferably an alkylcarbonyl group having 2 to 20 carbon atoms;
- an arylcarbonyl group, preferably an arylcarbonyl group having 7 to 20 carbon atoms;
- A hydrogen atom, a deuterium atom, a fluorine atom, a cyano group, or -SF ₅ .

In the above groups, one or more hydrogen atoms may be replaced with fluorine atoms, or one or more hydrogen atoms may be replaced with deuterium atoms.

Unless otherwise specified, aryl is aromatic hydrocarbon and heteroaryl is heteroaromatic ring.

(Preferred Group in Substituent Group S)
Among these substituent group S,
Preferably, an alkyl group, an alkoxy group, an aryloxy group, an arylamino group, an aralkyl group, an alkenyl group, an aryl group, a heteroaryl group, an alkylsilyl group, an arylsilyl group, and at least one hydrogen atom of these groups is fluorine. a group substituted with an atom, a fluorine atom, a cyano group, or _-SF5 ,
More preferably, an alkyl group, an arylamino group, an aralkyl group, an alkenyl group, an aryl group, a heteroaryl group, a group in which one or more hydrogen atoms of these groups are replaced with a fluorine atom, a fluorine atom, a cyano group, or , −SF ₅ , and
more preferably an alkyl group, an alkoxy group, an aryloxy group, an arylamino group, an aralkyl group, an alkenyl group, an aryl group, a heteroaryl group, an alkylsilyl group, an arylsilyl group,
Particularly preferred are alkyl groups, arylamino groups, aralkyl groups, alkenyl groups, aryl groups and heteroaryl groups,
Most preferred are alkyl groups, arylamino groups, aralkyl groups, aryl groups and heteroaryl groups.

These substituent group S may further have a substituent selected from the substituent group S as a substituent. Preferred groups, more preferred groups, further preferred groups, particularly preferred groups, and most preferred groups of the substituents which may be present are the same as the preferred groups in Substituent Group S and the like.

(preferred structure of formula (201))
Among the structures represented by the above formula (202) in the above formula (201), a structure having a group to which a benzene ring is linked, an aromatic hydrocarbon in which an alkyl group or an aralkyl group is bonded to ring A1 or ring A2 A structure having a group or an aromatic heterocyclic group, and a structure in which a dendron is bonded to ring A1 or ring A2 are preferred.

In a structure having a group to which a benzene ring is linked,
Ar ²⁰¹ is a benzene ring structure, i1 is 1 to 6, and at least one of the benzene rings is bonded to the adjacent structure at the ortho- or meta-position.
This structure is expected to improve the solubility and the charge transport property.

In a structure having an aromatic hydrocarbon group or aromatic heterocyclic group to which an alkyl group or an aralkyl group is bonded to ring A1 or ring A2,
Ar ²⁰¹ is an aromatic hydrocarbon structure or an aromatic heterocyclic structure, i1 is 1 to 6,
Ar ²⁰² is an aliphatic hydrocarbon structure, i2 is 1-12, preferably 3-8,
Ar ²⁰³ is a benzene ring structure and i3 is 0 or 1.
In this structure, Ar ²⁰¹ is preferably the above aromatic hydrocarbon structure, more preferably a structure in which 1 to 5 benzene rings are linked, and more preferably one benzene ring.
This structure is expected to improve the solubility and the charge transport property.

In a structure in which a dendron is bound to ring A1 or ring A2,
Ar ²⁰¹ and Ar ²⁰² are benzene ring structures,
Ar ²⁰³ is a biphenyl or terphenyl structure,
i1 and i2 are 1 to 6, i3 is 2, and j is 2.
This structure is expected to improve the solubility and the charge transport property.

Among the structures represented by B ²⁰¹ -L ²⁰⁰ -B ²⁰² , structures represented by the following formula (203) or (204) are preferable.

R ²¹¹ , R ²¹² and R ²¹³ represent substituents.
Although the substituent is not particularly limited, it is preferably a group selected from the substituent group S described above.

Ring B3 represents an aromatic heterocyclic structure containing a nitrogen atom, which may have a substituent.
Ring B3 is preferably a pyridine ring.
Although the substituent that ring B3 may have is not particularly limited, it is preferably a group selected from the substituent group S described above.

Although the phosphorescent material represented by formula (201) is not particularly limited, specific examples include the following structures.
In addition, Me means a methyl group and Ph means a phenyl group.

Here, the compound represented by the following formula (205) will be explained.

In formula (205), ^M2 represents a metal and T represents a carbon or nitrogen atom. R ⁹² to R ⁹⁵ each independently represent a substituent. However, when T is a nitrogen atom, ^R94 and ^R95 do not exist.

In formula (205), ^M2 represents a metal. Specific examples include metals selected from groups 7 to 11 of the periodic table. Among them, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum and gold are preferred, and divalent metals such as platinum and palladium are particularly preferred.

In formula (205), R ⁹² and R ⁹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, represents an alkoxy group, an alkylamino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group;

Furthermore, when T is a carbon atom, ^R94 and ^R95 each independently represent a substituent represented by the same examples as ^R92 and ^R93 . Also, when T is a nitrogen atom, there is no ^R94 or ^R95 directly bonded to said T.

In addition, R ⁹² to R ⁹⁵ may further have a substituent. Substituents can be the aforementioned substituents exemplified for R ⁹² and R ⁹³ . Furthermore, any two or more groups selected from R ⁹² to R ⁹⁵ may be linked together to form a ring.

(molecular weight)
The molecular weight of the phosphorescent material is preferably 5,000 or less, more preferably 4,000 or less, and particularly preferably 3,000 or less. Further, the molecular weight of the phosphorescent material is usually 800 or more, preferably 1000 or more, more preferably 1200 or more. It is believed that within this molecular weight range, the phosphorescent light-emitting material is not agglomerated and uniformly mixed with the charge-transporting material, making it possible to obtain a light-emitting layer with high light-emitting efficiency.

The molecular weight of the phosphorescent light-emitting material has a high Tg, melting point, decomposition temperature, etc., and the phosphorescent light-emitting material and the formed light-emitting layer have excellent heat resistance, and the film quality due to gas generation, recrystallization, molecular migration, etc. A large value is preferable from the viewpoint that it is difficult to cause a decrease in the concentration of impurities and an increase in the concentration of impurities due to thermal decomposition of the material. On the other hand, the molecular weight of the phosphorescent light-emitting material is preferably small in terms of facilitating purification of the organic compound.

[3] Charge Transport Material The composition for organic electroluminescence elements of the present invention preferably contains a charge transport material as a second host material in addition to the aromatic compound represented by Formula (1).

In the light-emitting layer, the charge-transporting material transports electrons and holes, and the compound of formula (1) suppresses the transport of electrons and holes, thereby adjusting the carrier balance in the light-emitting layer. In addition, the compound of formula (1) suppresses aggregation of the charge transport material and moderately disperses the charge transport material. These improve the efficiency and durability of the organic electroluminescent device.

The charge-transporting material used as the second host material of the light-emitting layer is a material having a skeleton with excellent charge-transporting properties, and includes an electron-transporting material, a hole-transporting material, and a bipolar material capable of transporting both electrons and holes. It is preferably selected from flexible materials.

Specific examples of skeletons with excellent charge transport properties include aromatic structures, aromatic amine structures, triarylamine structures, dibenzofuran structures, naphthalene structures, phenanthrene structures, phthalocyanine structures, porphyrin structures, thiophene structures, benzylphenyl structures, fluorene structure, quinacridone structure, triphenylene structure, carbazole structure, pyrene structure, anthracene structure, phenanthroline structure, quinoline structure, pyridine structure, pyrimidine structure, triazine structure, oxadiazole structure, imidazole structure, and the like.

As the electron-transporting material, a compound having a pyridine structure, a pyrimidine structure, and/or a triazine structure, which is excellent in electron-transporting properties and has a relatively stable structure, is more preferable, and a compound having a pyrimidine structure and/or a triazine structure is further preferable. preferable.

A hole-transporting material is a compound having a structure with excellent hole-transporting properties, and among the skeletons with excellent charge-transporting properties, a carbazole structure, a dibenzofuran structure, a triarylamine structure, a naphthalene structure, a phenanthrene structure, or a pyrene structure. is preferable as a structure having excellent hole-transporting properties, and a carbazole structure, a dibenzofuran structure, or a triarylamine structure is more preferable.

The charge-transporting material used as the host material of the light-emitting layer is preferably a compound having a condensed ring structure of three or more rings, and at least a compound having two or more condensed ring structures of three or more rings or a condensed ring of five or more rings. Compounds having one are more preferred. These compounds increase the rigidity of the molecules, making it easier to obtain the effect of suppressing the degree of molecular motion in response to heat. Further, the 3 or more condensed rings and the 5 or more condensed rings preferably have an aromatic hydrocarbon ring or an aromatic heterocyclic ring from the viewpoint of charge transportability and material durability.

Specific examples of condensed ring structures having three or more rings include anthracene structure, phenanthrene structure, pyrene structure, chrysene structure, naphthacene structure, triphenylene structure, fluorene structure, benzofluorene structure, indenofluorene structure, indolofluorene structure, Carbazole structure, indenocarbazole structure, indolocarbazole structure, dibenzofuran structure, dibenzothiophene structure and the like.

At least one selected from the group consisting of a phenanthrene structure, a fluorene structure, an indenofluorene structure, a carbazole structure, an indenocarbazole structure, an indolocarbazole structure, a dibenzofuran structure, and a dibenzothiophene structure, from the viewpoints of charge transportability and solubility. A carbazole structure or an indolocarbazole structure is more preferred from the viewpoint of resistance to electric charge.

In the present invention, at least one of the host materials in the light-emitting layer is preferably a material having a pyrimidine skeleton or a triazine skeleton, from the viewpoint of the durability of the organic electroluminescent device against charges.

The electron-transporting host having a pyrimidine skeleton or triazine skeleton is preferably a compound represented by the following formula (40).

In formula (40), X ¹ represents C or N;
R ⁵⁵ to R ⁵⁷ each independently represents an alkyl group having 1 to 20 carbon atoms, a (hetero)aralkyl group having 7 to 40 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a (hetero) group having 3 to 20 carbon atoms. aryloxy group, alkylsilyl group having 1 to 20 carbon atoms, arylsilyl group having 6 to 20 carbon atoms, alkylcarbonyl group having 2 to 20 carbon atoms, arylcarbonyl group having 7 to 20 carbon atoms, arylcarbonyl group having 1 to 20 carbon atoms Any one of an alkylamino group, an arylamino group having 6 to 20 carbon atoms, and a (hetero)aryl group having 3 to 30 carbon atoms, or a combination thereof. These groups may further have a substituent selected from the substituent group Z described above. When multiple R ⁵⁵ are present, the multiple R ⁵⁵ may be the same or different. Adjacent R ^55s bonded to a benzene ring may be bonded to each other to form a ring condensed to the benzene ring.
c is an integer from 0 to 5;

In terms of charge transport properties, R ⁵⁵ to R ⁵⁷ are each independently preferably a (hetero)aryl group having 3 to 20 carbon atoms. The (hetero)aryl group having 3 to 20 carbon atoms is at least selected from the group consisting of a monocyclic or condensed ring aryl group, a monocyclic or condensed ring heteroaryl group, and a monocyclic or condensed ring aryl group. Structures in which multiple groups of one type are linked, structures in which multiple monocyclic or condensed-ring heteroaryl groups are linked, and monocyclic or condensed-ring aryl groups or monocyclic or condensed-ring heteroaryl groups are optionally linked contains a structure that More preferably, each of R ⁵⁵ to R ⁵⁷ is independently selected from a phenyl group, a naphthyl group, a fluorenyl group, a carbazolyl group, an indolocarbazolyl group, an indenocarbazolyl group and an indenofluorenyl group. or a group having 3 to 20 carbon atoms in which a plurality of groups selected from a phenyl group, a naphthyl group, a fluorenyl group and a carbazolyl group are arbitrarily linked. Particularly preferably, R ⁵⁵ to R ⁵⁷ are each independently an indolocarbazolyl group, an indenocarbazolyl group, an indenofluorenyl group, a phenyl group or a group in which 2 or 3 phenyl groups are linked. be. These groups may further have a substituent selected from the substituent group Z described above.
From the standpoint of durability, c is preferably an integer of 0 to 2.

The compound represented by the following formula (40) is preferably a low-molecular-weight compound and has a molecular weight of usually 5,000 or less, preferably 3,000 or less, more preferably 2,000 or less, and still more preferably 1,000 or less. and is usually 400 or more, preferably 500 or more, more preferably 600 or more.

Preferred specific examples of the compound represented by the formula (40) contained as the charge-transporting material in the composition for organic electroluminescent elements of the present invention are shown below, but the present invention is not limited thereto.

The charge-transporting material used as the host material of the light-emitting layer is preferably a polymeric material from the viewpoint of excellent flexibility. A light-emitting layer formed using a material having excellent flexibility is preferable as a light-emitting layer of an organic electroluminescent device formed on a flexible substrate. When the charge-transporting material used as the host material contained in the light-emitting layer is a polymeric material, the molecular weight is preferably 5,000 or more and 1,000,000 or less, more preferably 10,000 or more and 500,000 or less, It is more preferably 10,000 or more and 100,000 or less.

In addition, the charge transport material used as the host material of the light emitting layer is easy to synthesize and purify, easy to design the electron transport performance and hole transport performance, and easy to adjust the viscosity when dissolved in a solvent. From the viewpoint of, it is preferably a low molecular weight. When the charge-transporting material used as the host material contained in the light-emitting layer is a low-molecular-weight material, the molecular weight is preferably 5,000 or less, more preferably 4,000 or less, and particularly preferably 3,000 or less. , most preferably 2,000 or less, usually 300 or more, preferably 350 or more, more preferably 400 or more.

[4] Other Components The composition for organic electroluminescence elements of the present invention may optionally contain various other solvents in addition to the solvent and luminescent material described above. Examples of such other solvents include amides such as N,N-dimethylformamide and N,N-dimethylacetamide, and dimethylsulfoxide.

Moreover, the composition for organic electroluminescence elements of the present invention may contain various additives such as a leveling agent and an antifoaming agent.
Furthermore, when laminating two or more layers by a wet film formation method, in order to prevent these layers from becoming compatible, a photocurable resin or a thermosetting resin is used for the purpose of curing and insolubilizing after film formation. can also be included.

[5] Concentration and blending ratio of materials in the composition for organic electroluminescent elements Solid content concentration in the composition for organic electroluminescent elements Concentration of all solids including components (leveling agent, etc.)] is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and still more preferably 0.1% by mass or more. 5% by mass or more, most preferably 1% by mass or more, usually 80% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, most preferably 20% by mass It is below. When the solid content concentration is within this range, it is easy to form a thin film having a desired film thickness with a uniform thickness, which is preferable.

Further, in the composition for an organic electroluminescent element of the present invention, the mass mixing ratio of the mass of the luminescent material/[the mass of the aromatic compound of the present invention+the mass of the host material] is usually 0.1/99.9 or more. , more preferably 0.5/99.5 or more, still more preferably 1/99 or more, most preferably 2/98 or more, usually 50/50 or less, more preferably 40/ It is 60 or less, more preferably 30/70 or less, and most preferably 20/80 or less. If this ratio falls below the lower limit or exceeds the upper limit, the luminous efficiency may drop significantly.

In addition, in the composition for an organic electroluminescent element of the present invention, the compounding ratio of the compound of formula (1) to the second host material is usually 1 mol% or more, more preferably 10 mol% or more. preferably 20 mol% or more, most preferably 30 mol% or more, usually 90 mol% or less, preferably 80 mol% or less, more preferably 70 mol% or less, most preferably 60 mol% or less.

[6] Method for preparing a composition for organic electroluminescence elements The composition for organic electroluminescence elements of the present invention comprises the aromatic compound of the present invention, the light-emitting material described above as necessary, and leveling that can be added as necessary. It is prepared by dissolving a solute comprising various additives such as agents and antifoaming agents in a suitable solvent.

In order to shorten the time required for the dissolution step and to keep the solute concentration in the composition for organic electroluminescent elements of the present invention uniform, the solute is usually dissolved while stirring the liquid. The dissolution step may be performed at room temperature, but if the dissolution rate is slow, the dissolution may be performed by heating. After completion of the dissolving step, a filtering step such as filtering may be performed as necessary.

[7] Properties, physical properties, etc. of the composition for organic electroluminescent elements (water concentration)
When an organic electroluminescent element is produced by forming a layer by a wet film-forming method using the composition for an organic electroluminescent element of the present invention, if moisture is present in the composition for an organic electroluminescent element used, the formed film The moisture content in the composition for organic electroluminescence elements of the present invention is preferably as low as possible, because moisture is mixed in the composition to impair the uniformity of the film. In general, organic electroluminescence devices use many materials such as cathodes that are significantly degraded by moisture. It is not preferable because it may remain and degrade the characteristics of the device.

Specifically, the amount of water contained in the composition for organic electroluminescent elements of the present invention is usually 1% by mass or less, preferably 0.1% by mass or less, and more preferably 0.01% by mass or less.

As a method for measuring the water concentration in the composition for organic electroluminescent elements, the method described in Japanese Industrial Standards "Method for measuring water content in chemical products" (JIS K0068: 2001) is preferable. -1348) and the like.

(uniformity)
The composition for an organic electroluminescence device of the present invention is preferably in a uniform liquid state at room temperature in order to improve stability in a wet film formation process, for example, ejection stability from a nozzle in an inkjet film formation method. . The uniform liquid state at room temperature means that the composition for organic electroluminescence elements is a liquid consisting of a uniform phase and does not contain particle components having a particle size of 0.1 μm or more in the composition for organic electroluminescence elements.

(physical properties)
If the viscosity of the composition for an organic electroluminescence device of the present invention is extremely low, for example, excessive liquid film flow in the film formation process tends to cause non-uniformity of the coated surface, nozzle discharge failure in ink jet film formation, and the like. If the viscosity of the composition for an organic electroluminescence device of the present invention is extremely high, clogging of nozzles and the like tend to occur during inkjet film formation.

Therefore, the viscosity at 25° C. of the composition for organic electroluminescence elements of the present invention is usually 2 mPa·s or more, preferably 3 mPa·s or more, more preferably 5 mPa·s or more, and usually 1000 mPa·s or less, preferably 1000 mPa·s or more. is 100 mPa·s or less, more preferably 50 mPa·s or less.

Further, when the composition for organic electroluminescence elements of the present invention has a high surface tension, the wettability of the film-forming liquid to the substrate is lowered, the leveling property of the liquid film is poor, and the film-forming surface is disturbed during drying. Problems such as becoming easier may occur

Therefore, the surface tension at 20° C. of the composition for organic electroluminescent elements of the present invention is usually less than 50 mN/m, preferably less than 40 mN/m.

Furthermore, when the vapor pressure of the composition for organic electroluminescence elements of the present invention is high, problems such as a change in solute concentration due to evaporation of the solvent may easily occur.

Therefore, the vapor pressure at 25° C. of the composition for organic electroluminescent elements of the present invention is usually 50 mmHg or less, preferably 10 mmHg or less, more preferably 1 mmHg or less.

<Organic electroluminescent element>
The organic electroluminescent device of the present invention has an anode and a cathode on a substrate, and an organic layer between the anode and the cathode, the organic layer being a layer containing a material for an organic electroluminescent device. and the material for an organic electroluminescence device contains the aromatic compound of the present invention.

The layer containing the aromatic compound is preferably formed using the material for organic electroluminescent elements or the composition for organic electroluminescent elements of the present invention.
Further, the layer containing the material for organic electroluminescence device is preferably a light-emitting layer.

Furthermore, it is preferable that the layer containing the aromatic compound is doped with an organometallic complex. As the organometallic complex, those exemplified as the light-emitting materials can be used.

In addition, since the aromatic compound of the present invention has a large energy gap (difference between HOMO and LUMO), a high excited triplet level (T1), and a high hole transport property, it may be included in the electron blocking layer. preferable. The layer structure of the organic electroluminescence device of the present invention, a general method for forming the same, and the like will be described below with reference to FIG.

FIG. 1 is a schematic cross-sectional view showing a structural example of the organic electroluminescence device of the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is a hole blocking layer, 7 is an electron transport layer, 8 is an electron injection layer, 9 represents a cathode, and 10 represents an organic electroluminescence device.

In the present invention, the wet film formation method includes, for example, spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, ink jet, and screen printing. method, gravure printing method, flexographic printing method, and other wet film forming methods. Among these film forming methods, the spin coating method, the spray coating method, and the inkjet method are preferable. This is because the spin coating method, the spray coating method, and the ink jet method are suitable for the liquid properties peculiar to the coating composition used for the organic electroluminescence device.

[1] Substrate The substrate 1 serves as a support for the organic electroluminescence element, and a quartz or glass plate, a metal plate or metal foil, a plastic film or sheet, or the like is used. Glass plates and transparent synthetic resin plates such as polyester, polymethacrylate, polycarbonate and polysulfone are particularly preferred. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too low, the organic electroluminescence device may be deteriorated by outside air passing through the substrate. Therefore, a method of providing a dense silicon oxide film or the like on at least one surface of a synthetic resin substrate to ensure gas barrier properties is also one of the preferable methods.

[2] Anode The anode 2 plays a role of injecting holes into the layer on the light-emitting layer side.
The anode 2 is usually composed of metals such as aluminum, gold, silver, nickel, palladium, and platinum, metal oxides such as indium and/or tin oxides, metal halides such as copper iodide, carbon black, or It is composed of conductive polymers such as poly(3-methylthiophene), polypyrrole and polyaniline.

The formation of the anode 2 is usually carried out by a sputtering method, a vacuum deposition method, or the like. In addition, when forming the anode 2 using metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., a suitable binder resin solution It is also possible to form the anode 2 by dispersing it in , and coating it on the substrate 1 . Furthermore, in the case of a conductive polymer, a thin film can be formed directly on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by coating the conductive polymer on the substrate 1 (Appl. Phys. Lett. ., 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it may have a laminated structure consisting of a plurality of materials, if desired.

The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably about 500 nm or less. The thickness of the anode 2 is arbitrary as long as it is opaque, and the thickness of the anode 2 may be the same as the thickness of the substrate 1 . Further, it is also possible to laminate a different conductive material on the anode 2 described above.

For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve hole injection properties, the surface of the anode 2 is subjected to ultraviolet (UV)/ozone treatment, oxygen plasma treatment, or argon plasma treatment. It is preferable to

[3] Hole-Injection Layer The hole-injection layer 3 is a layer that transports holes from the anode 2 to the light-emitting layer 5 and is usually formed on the anode 2 .

The method for forming the hole injection layer 3 of the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but from the viewpoint of reducing dark spots, the hole injection layer 3 may be formed by a wet film formation method. is preferred.

The film thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

(Formation of hole injection layer by wet film formation method)
When the hole injection layer 3 is formed by a wet film formation method, the material constituting the hole injection layer 3 is usually mixed with an appropriate solvent (solvent for the hole injection layer) to form a film formation composition ( A composition for forming a hole injection layer) is prepared, and this composition for forming a hole injection layer is applied onto a layer corresponding to the lower layer of the hole injection layer 3 (usually the anode) by an appropriate method. The hole injection layer 3 is formed by forming a film and drying it.

(Hole-transporting compound)
The composition for forming a hole injection layer usually contains a hole transport compound and a solvent as constituent materials of the hole injection layer.

The hole-transporting compound is a compound having a hole-transporting property that is usually used in the hole injection layer of an organic electroluminescent device, and may be a polymer compound such as a polymer, or a monomer or the like. Although it may be a low-molecular-weight compound, it is preferably a high-molecular-weight compound.

As the hole-transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3 . Examples of hole-transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked with fluorene groups, hydrazone derivatives, silazane derivatives, and silanamine. derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylenevinylene derivatives, polythienylenevinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

In the present invention, derivatives include, for example, aromatic amine derivatives, aromatic amines themselves and compounds having an aromatic amine as a main skeleton. It may be a polymer.

The hole-transporting compound used as the material for the hole-injection layer 3 may contain any one of such compounds alone, or may contain two or more thereof. When two or more hole-transporting compounds are contained, the combination is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two other hole-transporting compounds It is preferable to use the above together.

Among the compounds exemplified above, aromatic amine compounds are preferable, and aromatic tertiary amine compounds are particularly preferable, from the viewpoint of amorphousness and visible light transmittance. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.

The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound (polymeric compound in which repeating units are linked) having a weight average molecular weight of 1000 or more and 1000000 or less is further used. preferable. Preferred examples of aromatic tertiary amine polymer compounds include polymer compounds having repeating units represented by the following formula (I).

(In formula (I), Ar ⁵¹ and Ar ⁵² each independently represent an optionally substituted aromatic hydrocarbon group or an optionally substituted aromatic heterocyclic group Ar ⁵³ to Ar ⁵⁵ each independently represent an optionally substituted aromatic hydrocarbon group or an optionally substituted aromatic heterocyclic group, Y is the following: represents a linking group selected from a group of linking groups.In addition, two groups among Ar ⁵¹ to Ar ⁵⁵ that are bonded to the same N atom may be bonded to each other to form a ring.)

(In the above formulas, Ar ⁵⁶ to Ar ⁶⁶ each independently represent an optionally substituted aromatic hydrocarbon group or an optionally substituted aromatic heterocyclic group. R ³¹ and R ³² each independently represent a hydrogen atom or any substituent.)

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ⁵⁶ to Ar ⁶⁶ include benzene ring, naphthalene ring, phenanthrene ring, and thiophene ring, from the viewpoints of solubility, heat resistance, and hole injection/transport properties of polymer compounds. A group derived from a ring or a pyridine ring is preferable, and a group derived from a benzene ring or a naphthalene ring is more preferable.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ⁵⁶ to Ar ⁶⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. Preferred substituents include alkyl groups, alkenyl groups, alkoxy groups, aromatic hydrocarbon groups, and aromatic heterocyclic groups.

When R ³¹ and R ³² are optional substituents, the substituents include alkyl groups, alkenyl groups, alkoxy groups, silyl groups, siloxy groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like. .

Specific examples of aromatic tertiary amine polymer compounds having repeating units represented by formula (I) include those described in International Publication No. 2005/089024.

As the hole-transporting compound, a conductive polymer (PEDOT/PSS) obtained by polymerizing 3,4-ethylenedioxythiophene, which is a derivative of polythiophene, in high-molecular-weight polystyrene sulfonic acid. is also preferred. Also, the terminal of this polymer may be capped with methacrylate or the like.

The concentration of the hole-transporting compound in the composition for forming a hole-injection layer is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually 0.01% by mass or more, preferably 0.01% by mass or more, from the viewpoint of uniformity of the film thickness. is 0.1% by mass or more, more preferably 0.5% by mass or more, and is usually 70% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron-accepting compound as a constituent material of the hole injection layer. Here, the electron-accepting compound is preferably a compound having an oxidizing power and an ability to accept one electron from the above-described hole-transporting compound. Specifically, a compound having an electron affinity of 4 eV or more is preferable. , a compound having an electron affinity of 5 eV or more is more preferable.

Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. One or two or more compounds selected from the group are included.

Specifically, onium salts substituted with organic groups such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis(pendafluorophenyl)borate, triphenylsulfonium tetrafluoroborate (WO 2005/089024); Iron (III) (JP-A-11-251067), high-valence inorganic compounds such as ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris(pendafluorophenyl)borane (JP-A-2003-31365) fullerene derivatives; iodine; sulfonate ions such as polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate ions, and the like.

These electron-accepting compounds can improve the electrical conductivity of the hole-injecting layer by oxidizing the hole-transporting compound.

The content of the electron-accepting compound relative to the hole-transporting compound in the hole injection layer or the composition for forming the hole injection layer is usually 0.1 mol % or more, preferably 1 mol % or more. It is 100 mol % or less, preferably 40 mol % or less.

(Other constituent materials)
In addition to the hole-transporting compound and electron-accepting compound described above, the material for the hole-injecting layer may contain other components as long as the effects of the present invention are not significantly impaired. Examples of other components include various light-emitting materials, electron-transporting compounds, binder resins, coatability improvers, and the like. In addition, other components may use only 1 type and may use 2 or more types together by arbitrary combinations and ratios.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film-forming method is preferably a compound capable of dissolving the constituent materials of the hole injection layer. The boiling point of this solvent is usually 110° C. or higher, preferably 140° C. or higher, more preferably 200° C. or higher, and usually 400° C. or lower, preferably 300° C. or lower. If the boiling point of the solvent is too low, the drying speed will be too fast, possibly deteriorating the film quality. Also, if the boiling point of the solvent is too high, the temperature of the drying process must be raised, and other layers and substrates may be adversely affected.

Examples of solvents include ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and amide-based solvents.

Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole and 2,4-dimethylanisole.

Examples of ester-based solvents include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate and n-butyl benzoate.

Examples of aromatic hydrocarbon solvents include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. mentioned.

Examples of amide solvents include N,N-dimethylformamide and N,N-dimethylacetamide.

In addition, dimethylsulfoxide and the like can also be used.
Only one of these solvents may be used, or two or more of them may be used in any combination and ratio.

(Film formation method)
After preparing the composition for forming a hole injection layer, the composition is coated on a layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film formation, and dried. A hole injection layer 3 is formed.

The temperature in the film formation step is preferably 10° C. or higher and preferably 50° C. or lower in order to prevent film defects due to crystal formation in the composition.

The relative humidity in the film formation step is not limited as long as it does not significantly impair the effects of the present invention, but is usually 0.01 ppm or more and usually 80% or less.

After the film formation, the film of the hole injection layer forming composition is usually dried by heating or the like. Examples of heating means used in the heating step include clean ovens, hot plates, infrared rays, halogen heaters, and microwave irradiation. Among them, a clean oven and a hot plate are preferable in order to evenly apply heat to the entire film.

The heating temperature in the heating step is preferably a temperature equal to or higher than the boiling point of the solvent used in the composition for forming the hole injection layer, as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more solvents used in the hole injection layer, it is preferable that at least one of the solvents is heated at a temperature equal to or higher than the boiling point of the solvent. Considering the increase in the boiling point of the solvent, it is preferable to heat at 120° C. or higher and 410° C. or lower in the heating step.

In the heating step, the heating time is not limited as long as the heating temperature is equal to or higher than the boiling point of the solvent of the hole injection layer-forming composition and the coating film is not sufficiently insolubilized, but is preferably 10 seconds or more, usually 180 seconds. minutes or less. If the heating time is too long, the components of other layers will tend to diffuse, and if it is too short, the hole injection layer will tend to be inhomogeneous. Heating may be performed in two steps.

(Formation of hole injection layer by vacuum evaporation method)
When the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole-transporting compound, electron-accepting compound, etc.) are placed in a vacuum vessel. (When using two or more materials, put them in each crucible), evacuate the inside of the vacuum container to about 10 ^-4 Pa with a suitable vacuum pump, and then heat the crucible (2 When using more than one kind of material, heat each crucible), evaporate by controlling the evaporation amount (when using two or more kinds of materials, evaporate by controlling the evaporation amount independently), and A hole injection layer 3 is formed on the anode 2 of the facing substrates. When using two or more kinds of materials, the hole injection layer 3 can also be formed by putting a mixture of them in a crucible, heating and evaporating them.

The degree of vacuum during vapor deposition is not limited as long as it does not ^{significantly impair} the ^effects of the present invention. (12.0×10 ⁻⁴ Pa) or less. The vapor deposition rate is not limited as long as it does not significantly impair the effects of the present invention, but is usually 0.1 Å/second or more and usually 5.0 Å/second or less. The film formation temperature during vapor deposition is not particularly limited as long as the effects of the present invention are not significantly impaired, but is preferably 10° C. or higher and preferably 50° C. or lower.

[4] Hole transport layer The method for forming the hole transport layer 4 of the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited. It is preferably formed by a film forming method.

The hole-transporting layer 4 can be formed on the hole-injecting layer 3 if there is a hole-injecting layer, or on the anode 2 if there is no hole-injecting layer 3 . Further, the organic electroluminescence device of the present invention may have a structure in which the hole transport layer is omitted.

A material for forming the hole transport layer 4 is preferably a material that has a high hole transport property and can efficiently transport the injected holes. Therefore, it is preferable that the ionization potential is low, the transparency to visible light is high, the hole mobility is high, the stability is excellent, and impurities that act as traps are less likely to occur during manufacture or use. In many cases, since the hole transport layer 4 is in contact with the light emitting layer 5, it does not quench the light emitted from the light emitting layer 5 or form an exciplex with the light emitting layer 5 to reduce the efficiency. is preferred.

As the material for such a hole transport layer 4, any material can be used as long as it is a material conventionally used as a constituent material of a hole transport layer. Examples of compounds include those exemplified. Also, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatic group derivatives, metal complexes, and the like.

Also, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes. derivatives, poly(p-phenylene vinylene) derivatives and the like. These may be alternating copolymers, random polymers, block polymers or graft copolymers. Also, a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer may be used.

Among them, polyarylamine derivatives and polyarylene derivatives are preferred.
As the polyarylamine derivative, a polymer containing a repeating unit represented by the following formula (II) is preferred. In particular, a polymer composed of repeating units represented by the following formula (II) is preferable, and in this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In formula (II), Ar ^a and Ar ^b each independently represent an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group.)

Examples of aromatic hydrocarbon groups which may have substituents include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and acenaphthene. A group derived from a 6-membered monocyclic ring or 2 to 5 condensed rings, such as a ring, a fluoranthene ring, and a fluorene ring, and a group in which two or more of these rings are directly linked.

The aromatic heterocyclic group which may have a substituent includes, for example, a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzisoxazole ring, benzisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine 5- or 6-membered single ring such as ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, shinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. A ring, a group derived from 2 to 4 condensed rings, and a group in which two or more of these rings are directly linked by a bond are included.

From the viewpoint of solubility and heat resistance, Ar ^a and Ar ^b are each independently selected from the group consisting of benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring and fluorene ring. A selected ring-derived group or a group formed by connecting two or more benzene rings (for example, a biphenyl group or a terphenyl group) is preferable. Among them, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.

Examples of substituents that the aromatic hydrocarbon group and aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl group. amino group, diarylamino group, acyl group, halogen atom, haloalkyl group, alkylthio group, arylthio group, silyl group, siloxy group, cyano group, aromatic hydrocarbon ring group, aromatic heterocyclic group and the like.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group, which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II), is used as a repeating unit. A polymer having

As the polyarylene derivative, a polymer having repeating units represented by the following formula (III-1) and/or the following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group or a carboxy group, and t and s each independently represents an integer of 0 to 3. When t or s is 2 or more, a plurality of groups contained in one molecule may be the same or different, and adjacent ^Ra or ^Rb may form ^a ring. ⁾

(In formula (III-2), R ^e and R ^f are each independently synonymous with R ^a , R ^b , R ^c or R ^d in formula (III-1) above. r and u are each independently represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R ^f may form a ring together, and X represents an atom or a group of atoms constituting a 5- or 6-membered ring.)

Specific examples of X include an oxygen atom, an optionally substituted boron atom, an optionally substituted nitrogen atom, an optionally substituted silicon atom, and an optionally substituted an optionally substituted phosphorus atom, an optionally substituted sulfur atom, an optionally substituted carbon atom, or a group formed by combining these atoms.

Further, the polyarylene derivative has a repeating unit represented by the following formula (III-3) in addition to the repeating unit represented by the above formula (III-1) and/or the above formula (III-2). is preferred.

(In formula (III-3), Ar ^c to Ar ⁱ each independently represent an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group. v and w are each represents 0 or 1 independently.)

Specific examples of Ar ^c to Ar ⁱ are the same as Ar ^a and Ar ^b in formula (II) above.

Specific examples of the above formulas (III-1) to (III-3) and specific examples of the polyarylene derivative include those described in JP-A-2008-98619.

When the hole transport layer 4 is formed by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as in the formation of the hole injection layer 3, and after wet film formation, heat drying is performed. .

The hole-transporting layer-forming composition contains a solvent in addition to the hole-transporting compound described above. The solvent to be used is the same as that used for the composition for forming the hole injection layer. Further, the film formation conditions, heat drying conditions, etc. are the same as in the case of forming the hole injection layer 3 .

When the hole transport layer is formed by the vacuum vapor deposition method, the film forming conditions and the like are the same as those for forming the hole injection layer 3 described above.

The hole-transporting layer 4 may contain various light-emitting materials, electron-transporting compounds, binder resins, coatability improvers, etc., in addition to the hole-transporting compounds described above.

Further, the hole transport layer 4 may be a layer formed by cross-linking a cross-linkable compound. The crosslinkable compound is a compound having a crosslinkable group, and forms a network polymer compound by crosslinking.

Examples of crosslinkable groups include groups derived from cyclic ethers such as oxetane and epoxy; groups derived from unsaturated double bonds such as vinyl, trifluorovinyl, styryl, acryl, methacryloyl, and cinnamoyl; Examples thereof include groups derived from cyclobutene.

The crosslinkable compound may be a monomer, oligomer, or polymer. The crosslinkable compound may have only one type, or may have two or more types in any combination and ratio.

A hole-transporting compound having a crosslinkable group is preferably used as the crosslinkable compound.
Examples of the hole-transporting compound include those exemplified above, and examples of the cross-linking compound include those in which a cross-linking group is bonded to the main chain or side chain of these hole-transporting compounds. be done. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole-transporting compound is preferably a polymer containing a repeating unit having a crosslinkable group. is preferably a polymer having repeating units linked directly or via a linking group.

A hole-transporting compound having a crosslinkable group is preferably used as the crosslinkable compound.
Examples of hole-transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; silole derivatives; oligothiophene derivatives; condensed polycyclic aromatic derivatives; and metal complexes.

Among them, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, nitrogen-containing aromatic derivatives such as carbazole derivatives; triphenylamine derivatives; silole derivatives; condensed polycyclic aromatic derivatives; Triphenylamine derivatives are preferred, and triphenylamine derivatives are particularly preferred.

In order to form the hole transport layer 4 by cross-linking the cross-linking compound, a composition for forming a hole transport layer is usually prepared by dissolving or dispersing the cross-linking compound in a solvent, and the film is formed by wet film formation. to cross-link.

The composition for forming a hole transport layer may contain an additive that accelerates the cross-linking reaction in addition to the cross-linkable compound. Examples of additives that promote the cross-linking reaction include polymerization initiators and accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, and onium salts; condensed polycyclic hydrocarbons; porphyrin compounds; and photosensitizers such as diarylketone compounds.

Further, the composition for forming a hole transport layer may further contain coatability improvers such as leveling agents and antifoaming agents; electron-accepting compounds; binder resins and the like.

The composition for forming a hole transport layer usually contains 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more of the crosslinkable compound. In addition, the composition for forming a hole transport layer usually contains 50% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less of the crosslinkable compound.

After forming a film of a composition for forming a hole transport layer containing a crosslinkable compound at such a concentration on the lower layer (usually the hole injection layer 3), the crosslinkable compound is heated and/or irradiated with electromagnetic energy such as light. is crosslinked to form a network polymer compound.

Conditions such as temperature and humidity during film formation are the same as those for the wet film formation of the hole injection layer 3 . The method of heating after film formation is not particularly limited. The heating temperature condition is usually 120° C. or higher, preferably 400° C. or lower.

The heating time is usually 1 minute or more, preferably 24 hours or less. The heating means is not particularly limited, but means such as placing the laminate having the deposited layers on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120° C. or higher for 1 minute or longer can be used.

In the case of electromagnetic energy irradiation such as light, a method of directly using ultraviolet/visible/infrared light sources such as ultra-high pressure mercury lamps, high pressure mercury lamps, halogen lamps, and infrared lamps, or incorporating the aforementioned light source Examples thereof include a method of irradiation using a mask aligner and a conveyor type light irradiation device. Electromagnetic energy irradiation other than light includes, for example, a method of irradiation using a device for irradiating microwaves generated by a magnetron, a so-called microwave oven.

As for the irradiation time, it is preferable to set the conditions necessary to reduce the solubility of the film, but the irradiation is usually performed for 0.1 seconds or more, preferably 10 hours or less.

Heating and irradiation of electromagnetic energy such as light may be performed alone or in combination. When combining, the order of implementation is not particularly limited.

The thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[5] Light Emitting Layer A light emitting layer 5 is provided on the hole injection layer 3 or on the hole transport layer 4 when the hole transport layer 4 is provided. The light-emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between electrodes to which an electric field is applied, and becomes a main light source.

(Material of light-emitting layer)
The light-emitting layer 5 preferably contains the aromatic compound of the present invention, the charge-transporting material, and the light-emitting material (material having light-emitting properties), more preferably a compound having hole-transporting properties (hole transporting compound) or a compound having an electron transporting property (electron transporting compound) is contained as a charge transporting material. A light-emitting material may be used as a dopant material, and a hole-transporting compound, an electron-transporting compound, or the like may be used as a host material.

The content of the aromatic compound of the present invention with respect to the sum of the aromatic compound of the present invention and the charge transport material is preferably 0.1% by mass or more and 50% by mass or less, more preferably 0.5% by mass or more and 40% by mass or less, It is more preferably 1% by mass or more and 30% by mass or less.

The light-emitting material is not particularly limited, and a substance that emits light at a desired emission wavelength and has good light-emitting efficiency may be used. In the present invention, it is preferable to use the light-emitting material described above. On the other hand, it is preferable to use the aromatic compound of the present invention as a host material, especially as a hole-transporting compound.

Particularly, in the organic electroluminescent device of the present invention, the light-emitting layer is preferably formed by a wet film-forming method using the composition for an organic electroluminescent device of the present invention.

Furthermore, the light-emitting layer 5 may contain other components as long as the effects of the present invention are not significantly impaired. When the light-emitting layer 5 is formed by a wet film-forming method, it is preferable to use a low-molecular-weight material (normally 10,000 or less, preferably 5,000 or less).

<Formation of Light Emitting Layer>
When the light-emitting layer 5 is formed by a wet film-forming method, the material used for the light-emitting layer is dissolved in an appropriate solvent, and the composition for forming the light-emitting layer (when the aromatic compound of the present invention is included, the composition for organic electroluminescent elements object) and using it to form a film.

As the light-emitting layer solvent to be contained in the light-emitting layer-forming composition for forming the light-emitting layer 5 by a wet film-forming method, the same solvents as those described above as those contained in the composition for organic electroluminescence elements of the present invention can be used. It is the same.

In addition, the solid content concentration of the light-emitting material, charge-transporting compound, etc. in the light-emitting layer-forming composition is usually 0.01% by mass or more and usually 70% by mass or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the film.

After the composition for forming a light-emitting layer is wet film-formed, the obtained coating film is dried to remove the solvent, thereby forming the light-emitting layer. Specifically, it is the same as the method described in the formation of the hole injection layer. The wet film-forming method is not limited as long as it does not significantly impair the effects of the present invention, and any of the methods described above can be used.

The thickness of the light-emitting layer 5 is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the film thickness of the light-emitting layer 5 is too thin, defects may occur in the film, and if it is too thick, the drive voltage may increase.

[6] Hole Blocking Layer In the organic electroluminescence device of the present invention, it is preferable to provide a hole blocking layer 6 between the light emitting layer 5 and the electron injection layer 8 which will be described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

The hole-blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light-emitting layer 5. have

Physical properties required for the material constituting the hole blocking layer 6 include high electron mobility and low hole mobility, a large energy gap (difference between HOMO and LUMO), and an excited triplet level (T1). is high.

Examples of materials for the hole blocking layer that satisfy these conditions include bis(2-methyl-8-quinolinolato)(phenolato)aluminum, bis(2-methyl-8-quinolinolato)(triphenylsilanolate)aluminum, and the like. mixed ligand complexes, bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolato) aluminum binuclear metal complexes such as metal complexes, distyrylbiphenyl derivatives and the like Styryl compounds (JP-A-11-242996), triazole derivatives such as 3-(4-biphenylyl)-4-phenyl-5(4-tert-butylphenyl)-1,2,4-triazole (JP-A-7 -41759), and phenanthroline derivatives such as bathocuproine (JP-A-10-79297). Further, the compound having at least one pyridine ring substituted at the 2,4,6 positions described in International Publication No. 2005/022962 is also preferable as the material for the hole blocking layer 6 .

The materials for the hole blocking layer 6 may be used alone, or two or more of them may be used in any combination and ratio.

The method for forming the hole blocking layer 6 is not limited. Therefore, the hole blocking layer 6 can be formed by a wet film forming method, a vacuum deposition method, or other methods.

The film thickness of the hole blocking layer 6 is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less. be.

A hole relaxation layer may be provided instead of the hole blocking layer.

[7] Electron transport layer An electron transport layer 7 may be provided between the light emitting layer 5 and the electron injection layer 8 described below.
The electron transport layer 7 is provided for the purpose of further improving the luminous efficiency of the device, and efficiently transports electrons injected from the cathode 9 toward the luminescent layer 5 between the electrodes to which an electric field is applied. It is formed by a compound that can

The electron-transporting compound used in the electron-transporting layer 7 usually has a high electron injection efficiency from the cathode 9 or the electron-injecting layer 8, and has a high electron mobility and efficiently transports the injected electrons. Use a compound that can Compounds satisfying these conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (JP-A-59-194393), metal complexes of 10-hydroxybenzo[h]quinoline, and oxadiazole derivatives. , distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-tert-butyl-9,10-N,N'-dicyanoanthraquinone diimine, n-type hydrogenated amorphous silicon carbide , n-type zinc sulfide, n-type zinc selenide, and the like.

Only one material may be used for the electron transport layer 7, or two or more materials may be used in any combination and ratio.

The method for forming the electron transport layer 7 is not limited. Therefore, the electron transport layer 7 can be formed by a wet film-forming method, a vapor deposition method, or other methods.

The thickness of the electron transport layer 7 is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

[8] Electron injection layer The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5 . For efficient electron injection, the material forming the electron injection layer 8 is preferably a metal with a low work function. Examples thereof include alkali metals such as sodium and cesium, alkaline earth metals such as barium and calcium, and the like.

For example, lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium (II) carbonate (CsCO ₃ ), etc. (Applied Physics Letters, 1997, 70, 152 pages). ; JP-A-10-74586; IEEE Transactions on Electron Devices, 1997, Vol.44, p.1245; SID 04 Digest, p.154, etc.).

The film thickness of the electron injection layer is preferably 0.1 nm or more and 5 nm or less.

Furthermore, an organic electron transport compound represented by a nitrogen-containing heterocyclic compound such as bathophenanthroline or a metal complex such as an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( JP-A-10-270171, JP-A-2002-100478, JP-A-2002-100482, etc.), it is possible to improve electron injection and transport properties and achieve excellent film quality, which is preferable. . In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

Only one material may be used for the electron injection layer 8, or two or more materials may be used in any combination and ratio.

The method for forming the electron injection layer 8 is not limited. Therefore, the electron injection layer 8 can be formed by a wet film-forming method, a vapor deposition method, or other methods.

[9] Cathode The cathode 9 plays a role of injecting electrons into the layer on the light emitting layer 5 side (the electron injection layer 8, the light emitting layer 5, or the like).

As the material of the cathode 9, it is possible to use the material used for the anode 2, but in order to perform electron injection efficiently, a metal with a low work function is preferable, such as tin, magnesium, indium, Appropriate metals such as calcium, aluminum, silver or alloys thereof are used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy and aluminum-lithium alloy.

In addition, the material of the cathode 9 may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The film thickness of the cathode 9 is generally similar to that of the anode 2 .

Furthermore, for the purpose of protecting the cathode 9 made of a metal with a low work function, it is preferable to further laminate a metal layer that has a high work function and is stable to the atmosphere, since this increases the stability of the device. Metals such as, for example, aluminium, silver, copper, nickel, chromium, gold, platinum, etc. are used for this purpose. These materials may be used alone, or two or more of them may be used in any combination and ratio.

[10] Other Layers The organic electroluminescence device of the present invention may have other structures within the scope of the invention. For example, as long as the performance is not impaired, any layer other than the layers described above may be provided between the anode 2 and the cathode 9, or any layer may be omitted. .

[11] Electron blocking layer An example of the optional layer is an electron blocking layer. The electron blocking layer is provided between the hole injection layer 3 or the hole transport layer 4 and the light emitting layer 5 . The electron-blocking layer prevents electrons moving from the light-emitting layer 5 from reaching the hole-injecting layer 3, thereby increasing the probability of recombination between holes and electrons in the light-emitting layer 5. It has a role of confining excitons in the light emitting layer 5 and a role of efficiently transporting the holes injected from the hole injection layer 3 toward the light emitting layer 5 . In particular, it is effective to provide an electron blocking layer when a phosphorescent material or a blue light emitting material is used as the light emitting material.

Properties required for the electron blocking layer include high hole transportability, large energy gap (difference between HOMO and LUMO), and high excited triplet level (T1). Furthermore, when the light-emitting layer 5 is produced by a wet film-forming method, the electron blocking layer is also required to be compatible with the wet film-forming method. Materials used for such an electron-blocking layer include the aromatic compound of the present invention, a copolymer of dioctylfluorene and triphenylamine represented by F8-TFB (International Publication No. 2004/084260), and the like. .

In addition, only one material may be used for the electron blocking layer, or two or more materials may be used in any combination and ratio.

There are no restrictions on the method of forming the electron blocking layer. Therefore, the electron blocking layer can be formed by a wet film forming method, a vapor deposition method, or other methods.

Moreover, in the layer structure described above, it is also possible to stack components other than the substrate in the reverse order. For example, in the layer structure of FIG. The hole injection layer 3 and the anode 2 may be provided in this order.

Furthermore, the organic electroluminescence device of the present invention can be constructed by laminating components other than the substrates between two substrates, at least one of which is transparent.

It is also possible to adopt a structure in which constituent elements (light-emitting units) other than the substrate are stacked in multiple stages (structure in which multiple light-emitting units are stacked). In that case, instead of the interfacial layer between the stages (between the light emitting units) (when the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like Providing a carrier generation layer (CGL) reduces barriers between stages, and is more preferable from the viewpoint of luminous efficiency and driving voltage.

Furthermore, the organic electroluminescence device of the present invention may be configured as a single organic electroluminescence device, or may be applied to a configuration in which a plurality of organic electroluminescence devices are arranged in an array. are arranged in an XY matrix.
In addition, each layer described above may contain components other than those described as materials as long as the effects of the present invention are not significantly impaired.

The organic electroluminescence device of the present invention is used in display devices such as organic EL displays and lighting devices such as organic EL lighting. Using the organic electroluminescent device of the present invention, for example, by the method described in "Organic EL Display" (Ohmsha, August 20, 2004, by Shizuo Tokito, Chihaya Adachi, Hideyuki Murata) Organic EL displays and organic EL lighting can be formed.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Various conditions and values of evaluation results in the following examples have the meaning of preferable upper or lower limit values in the embodiments of the present invention. It may be a range defined by a value in an example or a combination of values between examples.

In the present specification, Ac means an acetyl group, Ph means a phenyl group, dppf means 1,1′-bis(diphenylphosphino)ferrocene, DMSO means dimethylsulfoxide, THF means tetrahydrofuran, DCM means dichloromethane and Tf means a trifluoromethylsulfonyl group (CF ₃ SO ₂ —). Intermediate 1 was synthesized according to the method described in Scientific Reports Vol.6, 33131; doi:10.1038/srep33131 (2016). Comparative compound 1 was synthesized according to the method described in Patent Document 2 (WO 2007/043357) mentioned above.

<Example 1: Synthesis example of compound 1>
(Synthesis of Intermediate 2)

Under a nitrogen atmosphere, Intermediate 1 (4.8 g, 14.4 mmol) was dissolved in 200 mL DCM and cooled to -70.degree. A 1 M solution of boron tribromide in dichloromethane (57.4 mL, 57.4 mmol) was slowly added dropwise, and the mixture was stirred at −70° C. for 1 hour and at room temperature for 12 hours. Water was added to the reaction solution for liquid separation washing, and the organic layer was dried over magnesium sulfate. After suction filtration, the solvent of the filtrate was distilled off to obtain Intermediate 2 (yield: 4.5 g, yield: 99%).

(Synthesis of Intermediate 3)

Intermediate 2 (4.5 g, 14.0 mmol) was dissolved in 70 mL of DCM under a nitrogen atmosphere and cooled to -10.degree. Anhydrous pyridine (2.3 mL, 28.8 mmol) was added, followed by slow dropwise addition of trifluoromethanesulfonic anhydride (2.8 mL, 17.2 mmol) diluted with 30 mL of DCM. The mixture was warmed to room temperature and stirred for 12 hours. Water was added to the reaction solution for liquid separation washing, and the organic layer was dried over magnesium sulfate. After suction filtration, the solvent of the filtrate was distilled off, and the residue was subjected to silica gel column chromatography to obtain Intermediate 3 (yield: 5.8 g, yield: 89%).

(Synthesis of Intermediate 4)

3,5-Dibromo-1-para-terphenylbenzene (14.1 g, 30.4 mmol), 3-meta-terphenyl boronic acid ester (7.2 g, 20.3 mmol) were subjected to nitrogen bubbling toluene (60 mL). and heated to 55°C. Ethanol (30 mL), potassium phosphate aqueous solution (2.0 mol/L, 30 mL), and Pd(PPh ₃ ) ₄ (0.23 g, 0.20 mmol) were added in order, and stirred at 90° C. for 3 hours. After cooling to room temperature, a saturated aqueous sodium chloride solution was added, the liquids were separated and washed, and the organic layer was dried over magnesium sulfate.
After suction filtration, the solvent of the filtrate was distilled off, and the residue was subjected to silica gel column chromatography to obtain Intermediate 4 (9.0 g, 72% yield).

(Synthesis of Intermediate 5)

To intermediate 4 (5.9 g, 9.62 mmol), bis(pinacolatodiboron) (3.7 g, 14.4 mmol), potassium acetate (2.8 g, 28.9 mmol) was added dry DMSO (100 mL), Heated to 50°C. PdCl ₂ (dppf)CH ₂ Cl ₂ (0.39 g, 0.48 mmol) was added and stirred at 90° C. for 5 hours. After cooling to room temperature, distilled water was added and suction filtration was performed. The filtrate was dissolved in dichloromethane, washed with a saturated aqueous sodium chloride solution, dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was subjected to silica gel column chromatography to obtain Intermediate 5 (yield 5.2 g, yield 82%).

(Synthesis of Intermediate 6)

Intermediate 5 (5.2 g, 7.87 mmol), 3-bromo-3′-iodo-1,1′-biphenyl (3.1 g, 8.66 mmol) was subjected to nitrogen bubbling toluene (80 mL), ethanol ( 30 mL) and an aqueous tripotassium phosphate solution (2.0 mol/L, 30 mL) were added in that order and heated to 60°C. PdCl ₂ (PPh ₃ ) ₂ (0.055 g, 0.079 mmol) was then added and stirred at 65° C. for 2 hours. After cooling to room temperature, a saturated sodium chloride aqueous solution was added, and extraction was performed using toluene. The organic layer was washed with a saturated aqueous sodium chloride solution, dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was subjected to silica gel column chromatography to obtain Intermediate 6 (yield 5.9 g, yield 98%).

(Synthesis of Intermediate 7)

To intermediate 6 (3.5 g, 4.61 mmol), bis(pinacolatodiboron) (1.8 g, 6.91 mmol), potassium acetate (1.4 g, 13.8 mmol) was added dry DMSO (100 mL), Heated to 50°C. PdCl ₂ (dppf)CH ₂ Cl ₂ (0.19 g, 0.23 mmol) was added and stirred at 90° C. for 4 hours. After cooling to room temperature, distilled water was added and suction filtration was performed. The filtrate was dissolved in dichloromethane, washed with a saturated aqueous sodium chloride solution, dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was subjected to silica gel column chromatography to obtain Intermediate 7 (2.3 g, 61% yield).

(Synthesis of Compound 1)

Nitrogen-bubbled toluene (20 mL) was added to Intermediate 3 (0.88 g, 1.94 mmol) and Intermediate 7 (1.9 g, 2.33 mmol) and heated to 55°C. Ethanol (10 mL), potassium phosphate aqueous solution (2.0 mol/L, 10 mL) and Pd(PPh ₃ ) ₄ (0.11 g, 0.097 mmol) were sequentially added and stirred at 90° C. for 8 hours. After cooling to room temperature, a saturated aqueous sodium chloride solution was added, the liquids were separated and washed, and the organic layer was dried over magnesium sulfate. After suction filtration, the solvent of the filtrate was distilled off, and the residue was subjected to silica gel column chromatography to obtain compound 1 (yield: 1.7 g, yield: 86%).

<Example 2: Synthesis example of compound 2>
(Synthesis of intermediate 8)

Nitrogen-bubbled toluene (100 mL) was added to 3,5-dibromo-1-para-terphenylbenzene (9.8 g, 21.2 mmol) and 3-biphenylboronic acid (2.8 g, 14.1 mmol). °C. Ethanol (50 mL), potassium phosphate aqueous solution (2.0 mol/L, 50 mL) and Pd(PPh ₃ ) ₄ (0.16 g, 0.14 mmol) were added in that order, and stirred at 90° C. for 6 hours. After cooling to room temperature, a saturated aqueous sodium chloride solution was added, the liquids were separated and washed, and the organic layer was dried over magnesium sulfate. After suction filtration, the solvent of the filtrate was distilled off, and the residue was subjected to silica gel column chromatography to obtain Intermediate 8 (yield 5.3 g, yield 70%).

(Synthesis of Intermediate 9)

To intermediate 8 (5.3 g, 9.86 mmol), bis(pinacolatodiboron) (3.8 g, 14.8 mmol), potassium acetate (2.9 g, 29.6 mmol) was added dry DMSO (100 mL), Heated to 50°C. PdCl ₂ (dppf)CH ₂ Cl ₂ (0.40 g, 0.49 mmol) was added and stirred at 90° C. for 4 hours. After cooling to room temperature, distilled water was added and suction filtration was performed. The filtrate was dissolved in dichloromethane, washed with a saturated aqueous sodium chloride solution, dried over magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was subjected to silica gel column chromatography to obtain Intermediate 9 (4.0 g, 69% yield).

(Synthesis of compound 2)

Nitrogen-bubbled toluene (50 mL) was added to Intermediate 3 (1.8 g, 3.87 mmol) and Intermediate 9 (2.3 g, 3.87 mmol) and heated to 55°C. Ethanol (25 mL), potassium phosphate aqueous solution (2.0 mol/L, 25 mL) and Pd(PPh ₃ ) ₄ (0.22 g, 0.19 mmol) were sequentially added and stirred at 90° C. for 9 hours. After cooling to room temperature, a saturated aqueous sodium chloride solution was added, the liquids were separated and washed, and the organic layer was dried over magnesium sulfate. After suction filtration, the solvent of the filtrate was distilled off, and the residue was subjected to silica gel column chromatography to obtain compound 2 (yield: 2.6 g, yield: 87%).

<Evaluation of Compounds 1 to 2 and Comparative Compound 1>
The glass transition temperature (Tg) of each compound was evaluated by differential scanning calorimetry (DSC).
The ionization potential (Ip) of each compound was evaluated by photoelectron spectroscopy.
The electron affinity (EA) of each compound was calculated by subtracting Ip from the bandgap (Eg) calculated from the absorption edge of the absorption spectrum.
The solubility of each compound in cyclohexylbenzene (CHB) was evaluated.
Table 1 shows the results.

In addition, the comparative compound 1 used what is shown below.

In addition, the solubility in cyclohexylbenzene (CHB) was evaluated by preparing a cyclohexylbenzene solution of about 1 to 2 mL (concentration of each compound: 2.0% by mass), and determining whether each compound was dissolved in the solution. I judged by.
">2.0% by mass" in Table 1 means that the compound was dissolved in the solution.

From Table 1, it was found that the aromatic compounds of the present invention have excellent heat resistance, high solubility, and a large bandgap.

<Example 3>
An organic electroluminescence device was produced by the following method.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate to a thickness of 50 nm (manufactured by Geomatec, a sputter-deposited product) was subjected to a 2 mm-wide stripe using ordinary photolithography and etching with hydrochloric acid. was patterned to form an anode. The substrate on which the ITO pattern is formed in this manner is washed with ultrasonic waves using an aqueous solution of surfactant, washed with ultrapure water, ultrasonically washed with ultrapure water, and washed with ultrapure water in this order, and then dried with compressed air. , and finally performed ultraviolet ozone cleaning.

As a composition for forming a hole injection layer, 3.0% by mass of a hole-transporting polymer compound having a repeating structure of the following formula (P-1) and an electron represented by the following structural formula (HI-1) A solution was prepared by dissolving 0.6% by weight of the receptive compound in ethyl benzoate.

This solution was spin-coated on the substrate in the atmosphere and dried on a hot plate in the atmosphere at 240° C. for 30 minutes to form a uniform thin film with a thickness of 40 nm, which was used as a hole injection layer.

Next, a charge-transporting polymer compound having the following structural formula (HT-1) was dissolved in 1,3,5-trimethylbenzene to prepare a 2.0% by mass solution.

This solution was spin-coated on the substrate on which the hole injection layer was coated in a nitrogen glove box, and dried on a hot plate in the nitrogen glove box at 230° C. for 30 minutes to form a uniform thin film with a thickness of 40 nm. was formed to form a hole transport layer.

Subsequently, as materials for the light-emitting layer, 2.3% by mass of the compound 1 obtained in Example 1, 1.15% by mass of the compound represented by the following structural formula (EH-1), and the following structural formula ( EH-2) at a concentration of 1.15% by mass and a compound represented by the following structural formula (D-1) at a concentration of 1.4% by mass in cyclohexylbenzene to obtain a light-emitting layer forming solution. was prepared.

This solution was spin-coated in a nitrogen glove box onto the substrate on which the hole transport layer had been applied and dried on a hot plate in the nitrogen glove box at 120° C. for 20 minutes to form a uniform thin film with a thickness of 40 nm. was formed to form a light-emitting layer.

The substrate on which up to the light-emitting layer was formed was placed in a vacuum deposition apparatus, and the inside of the apparatus was evacuated to 2×10 ⁻⁴ Pa or less.

Next, a compound represented by the following structural formula (ET-1) and 8-hydroxyquinolinolatritium are co-deposited on the light-emitting layer at a film thickness ratio of 2:3 by a vacuum vapor deposition method to obtain a film thickness. A 30 nm electron transport layer was formed.

Subsequently, a striped shadow mask with a width of 2 mm was adhered to the substrate so as to be orthogonal to the ITO stripes of the anode as a mask for cathode evaporation, and aluminum was heated with a molybdenum boat to form an aluminum layer with a thickness of 80 nm. formed to form the cathode.
As described above, an organic electroluminescence device having a light-emitting area of 2 mm×2 mm was obtained.

<Example 4>
An organic electroluminescence device was produced in the same manner as in Example 3, except that Compound 2 obtained in Example 2 was used instead of Compound 1 as a material for the light-emitting layer.

<Comparative Example 1>
An organic electroluminescence device was produced in the same manner as in Example 3, except that the above-described comparative compound 1 was used instead of compound 1 as the material of the light-emitting layer.

<Evaluation of Organic Electroluminescent Device>
The time required for the luminance to decrease to 95% of the initial luminance ( ^LT95 ) was measured. These measurement results are shown in Table 2. In Table 2, the values of Examples 3 and 4 are relative values with the value of Comparative Example 1 set to 1.

From the results in Table 2, it was found that the performance of the organic electroluminescence devices (Examples 3 and 4) using Compound 1 and Compound 2, which are aromatic compounds of the present invention, was improved.

REFERENCE SIGNS LIST 1 substrate 2 anode 3 hole injection layer 4 hole transport layer 5 light emitting layer 6 hole blocking layer 7 electron transport layer 8 electron injection layer 9 cathode 10 organic electroluminescent element

Claims (15)

An aromatic compound represented by the following formula (1).

(In formula (1),
Ar ¹¹ to Ar ¹⁴ each independently represent the following formula (2),
R ¹ to R ⁴ each independently represent a substituent,
n11 is an integer from 1 to 4,
n12 to n14 are each independently an integer of 0 to 3,
The sum of n11 to n14 is 4 or less,
ma to md are each independently an integer of 0 to 4; )

(In formula (2),
The asterisk (*) represents a bond with formula (1),
L ¹ and L ² each independently represent an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms, or an optionally substituted divalent carbon atom of 30 or less or an optionally substituted divalent aromatic hydrocarbon group having 30 or less carbon atoms and an optionally substituted divalent heteroaromatic group having 30 or less carbon atoms is a group in which a plurality of groups selected from groups are linked,
Ar ² is each independently an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms, or an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms or an optionally substituted monovalent aromatic hydrocarbon group having 60 or less carbon atoms and an optionally substituted monovalent heteroaromatic group having 60 or less carbon atoms is a group in which a plurality of groups are linked,
each R ⁵ independently represents a substituent,
a and b each independently represent an integer of 0 to 5,
me represents an integer of 0 to 4; ) 2. The aromatic compound according to claim 1, wherein Ar ² in formula (2) is represented by any one of formulas (3) to (5) below.

(In formulas (3) to (5),
The asterisk (*) represents a bond with formula (2),
R ⁶ to R ⁴⁴ each independently represent a hydrogen atom or a substituent,
Adjacent R ⁶ to R ⁴⁴ may combine with each other to form a condensed ring. ) 3. The aromatic compound according to claim 2, wherein the substituents that L ¹ and L ² may have and the substituents in R ¹ to R ⁴⁴ are each independently an aromatic hydrocarbon group. 4. The aromatic compound according to claim 2 or 3, wherein in formula ( ² ), Ar2 is represented by formula (3) or formula (4). 5. The aromatic compound according to any one of claims 1 to 4, wherein in formula (2), L ¹ is not a condensed ring. An organic electroluminescence device having an anode and a cathode on a substrate and an organic layer between the anode and the cathode,
The organic layer has a layer containing an organic electroluminescence device material,
An organic electroluminescence device, wherein the material for organic electroluminescence device is the aromatic compound according to any one of claims 1 to 5. 7. The organic electroluminescent device according to claim 6, wherein the layer containing the organic electroluminescent device material is a light-emitting layer. The light-emitting layer comprises the aromatic compound according to any one of claims 1 to 5, a charge transport material, and a light-emitting material,
8. The organic electroluminescence device according to claim 7, wherein the content of said aromatic compound with respect to the sum of said aromatic compound and said charge transport material is 0.1% by mass or more and 50% by mass or less. A display device comprising the organic electroluminescence device according to any one of claims 6 to 8. A lighting device comprising the organic electroluminescence device according to any one of claims 6 to 8. A composition for organic electroluminescence devices, comprising the aromatic compound according to any one of claims 1 to 5 and a solvent. 12. The composition for an organic electroluminescence device according to claim 11, further comprising a phosphorescent material and a charge transport material. 13. A method for forming a thin film, comprising the step of forming a film from the composition for organic electroluminescence elements according to claim 11 or 12 by a wet film-forming method. A method for producing an organic electroluminescence device having an anode and a cathode on a substrate and an organic layer between the anode and the cathode, the method comprising:
A method for producing an organic electroluminescent device, comprising forming the organic layer by a wet film-forming method using the composition for an organic electroluminescent device according to claim 11 or 12. 15. The method of manufacturing an organic electroluminescent device according to claim 14, wherein the organic layer is a light-emitting layer.

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