JP7491302B2 - Arylamine compounds and their uses - Google Patents

Description

The present invention relates to arylamine compounds and their uses.

Organic electroluminescence (hereinafter referred to as organic EL) elements are expected to be put to practical use in fields such as displays and lighting, and various developments have been made on materials and element structures with the aim of achieving low-voltage operation, high brightness, long life, etc.
This organic EL element uses a number of functional thin films. One of these, the hole injection layer, is responsible for the exchange of charges between the anode and the hole transport layer or the light-emitting layer, and plays an important role in achieving low-voltage operation and high brightness of the organic EL element.

The methods for producing this hole injection layer are roughly divided into dry processes, such as deposition, and wet processes, such as spin coating. Compared to these processes, wet processes are more efficient at producing thin films with high flatness over a large area.
For this reason, as organic EL displays are currently being made larger in area, there is a demand for hole injection layers that can be formed by wet processes.

In light of these circumstances, the inventors have developed charge transport materials that can be applied to various wet processes and that, when applied to the hole injection layer of an organic EL element, give thin films that can realize excellent EL element characteristics, as well as compounds that have good solubility in the organic solvents used therein (see Patent Documents 1 to 3).

Meanwhile, various efforts have been made to improve the performance of organic EL elements, and efforts have been made to adjust the refractive index of the functional film used for the purpose of improving light extraction efficiency, etc. Specifically, attempts have been made to improve the efficiency of elements by using hole injection layers and hole transport layers with relatively high or low refractive indexes in consideration of the overall configuration of the element and the refractive indexes of other adjacent members (see Patent Documents 4 and 5).
Thus, the refractive index is an important factor in designing an organic EL device, and is considered to be an important physical property value that should be taken into consideration in materials for organic EL devices.

Furthermore, because coloring of a charge-transporting thin film used in an organic EL element reduces the color purity and color reproducibility of the organic EL element, in recent years, it has been desired that a charge-transporting thin film for an organic EL element has a high transmittance in the visible region and is highly transparent (see Patent Document 6).
As described above, as organic EL displays are currently being made larger in area, vigorous development is being carried out toward the practical application of organic EL displays using wet processes, and there is a constant demand for wet process materials that can provide charge-transporting thin films with good transparency.

International Publication No. 2008/129947 International Publication No. 2015/050253 International Publication No. 2017/217457 JP 2007-536718 A JP 2017-501585 A International Publication No. 2013/042623

The present invention has been made in consideration of these circumstances, and aims to provide an arylamine compound that has good solubility in organic solvents and gives a thin film with good optical properties, and when this thin film is applied to a hole injection layer or the like, it can realize an organic EL element with good properties.

As a result of extensive research into achieving the above-mentioned object, the inventors discovered that a specific arylamine compound having an arylcarbazole skeleton has good solubility in organic solvents, and that a varnish containing said compound gives a thin film with excellent optical properties, and that when this thin film is applied to a hole injection layer or the like, an organic EL element with good properties is obtained, thus completing the present invention.

（式中、Ｒ¹は、それぞれ独立して、炭素数６～２０のアリール基を表し、Ｒ²は、それぞれ独立して、水素原子、ハロゲン原子、ニトロ基、シアノ基、炭素数１～２０のアルキル基、炭素数１～２０のハロゲン化アルキル基、炭素数１～２０のアルコキシ基、または炭素数６～２０のアリール基を表す。）
２． 下記式（１－１）で表される１のアリールアミン化合物、

（式中、Ｒ¹およびＲ²は、前記と同じ意味を表す。）
３． 下記式（１－１Ａ）または（１－１Ｂ）で表される２のアリールアミン化合物、

（式中、Ｒ¹およびＲ²は、前記と同じ意味を表す。）
４． 前記Ｒ¹が、フェニル基、１－ナフチル基または２－ナフチル基である１～３のいずれかのアリールアミン化合物、
５． 前記Ｒ¹が、すべてフェニル基である４のアリールアミン化合物、
６． 前記Ｒ²が、すべて水素原子である１～５のいずれかのアリールアミン化合物、
７． １～６のいずれかのアリールアミン化合物と、有機溶媒とを含む電荷輸送性ワニス、
８． ドーパント物質を含む７の電荷輸送性ワニス、
９． 前記ドーパント物質が、アリールスルホン酸エステル化合物である８の電荷輸送性ワニス、
１０． ７～９のいずれかの電荷輸送性ワニスを用いて作製される電荷輸送性薄膜、
１１． １０の電荷輸送性薄膜を備える電子素子、
１２． １０の電荷輸送性薄膜を備える有機エレクトロルミネッセンス素子、
１３． 前記電荷輸送性薄膜が、正孔注入層または正孔輸送層である１２の有機エレクトロルミネッセンス素子
を提供する。 That is, the present invention provides
1. An arylamine compound represented by the following formula (1):

(In the formula, each R ¹ independently represents an aryl group having 6 to 20 carbon atoms, and each R ² independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)
2. An arylamine compound represented by the following formula (1-1):

(In the formula, ^R1 and ^R2 have the same meanings as defined above.)
3. An arylamine compound represented by the following formula (1-1A) or (1-1B):

(In the formula, ^R1 and ^R2 have the same meanings as defined above.)
4. The arylamine compound according to any one of 1 to 3, wherein R ¹ is a phenyl group, a 1-naphthyl group, or a 2-naphthyl group.
5. The arylamine compound according to 4, wherein all of the R ¹ 's are phenyl groups.
6. The arylamine compound according to any one of 1 to 5, wherein all of the R ^2's are hydrogen atoms.
7. A charge-transporting varnish comprising an arylamine compound according to any one of 1 to 6 and an organic solvent.
8. The charge transport varnish of 7 containing a dopant material;
9. The charge transporting varnish according to 8, wherein the dopant substance is an arylsulfonic acid ester compound.
10. A charge-transporting thin film produced by using the charge-transporting varnish according to any one of 7 to 9.
11. An electronic device comprising the charge transport thin film of 10.
12. An organic electroluminescence device comprising the charge transport thin film of 10.
13. The organic electroluminescence device of 12, wherein the charge transporting thin film is a hole injection layer or a hole transport layer.

The arylamine compound of the present invention has good solubility in organic solvents, and by using a charge-transporting varnish containing this arylamine compound, a charge-transporting thin film having high transparency (low k (extinction coefficient)) and a high refractive index (high n) can be obtained.
This charge transporting thin film can be suitably used as a thin film for electronic devices such as organic EL devices. In particular, by applying the charge transporting thin film of the present invention to a hole injection layer or the like of an organic EL device, a device having good characteristics can be produced.

The present invention will be described in further detail below.
The arylamine compound according to the present invention is characterized by being represented by the following formula (1), and in a preferred embodiment, is represented by formula (1-1).

In formulas (1) and (1-1), R ¹ 's each independently represent an aryl group having 6 to 20 carbon atoms, and R ² 's each independently represent a hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and examples thereof include linear or branched alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups; and cyclic alkyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, bicyclobutyl, bicyclopentyl, bicyclohexyl, bicycloheptyl, bicyclooctyl, bicyclononyl, and bicyclodecyl groups.

The alkyl group in the alkoxy group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, s-butoxy, t-butoxy, n-pentoxy, n-hexyloxy, n-octyloxy, n-decyloxy, 2-methylhexyloxy, 2-ethylhexyloxy, 2-n-propylhexyloxy, 2-n-butylhexyloxy, 2-ethyldecyloxy, and 3-ethylhexyloxy groups.

Specific examples of aryl groups having 6 to 20 carbon atoms include phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, and 9-phenanthryl groups.

A halogenated alkyl group having 1 to 20 carbon atoms is a group in which at least one hydrogen atom of the alkyl group having 1 to 20 carbon atoms is replaced with a halogen atom, and specific examples include fluoromethyl, difluoromethyl, trifluoromethyl, bromodifluoromethyl, 2-chloroethyl, 2-bromoethyl, 1,1-difluoroethyl, 2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, 2-chloro-1,1,2-trifluoroethyl, pentafluoroethyl, 3-bromopropyl, 2,2,3,3-tetrafluoropropyl, 1,1,2,3,3,3-hexafluoropropyl, 1,1,1,3,3,3-hexafluoropropan-2-yl, 3-bromo-2-methylpropyl, 4-bromobutyl, perfluoropentyl, and 2-(perfluorohexyl)ethyl groups.

In particular, taking into consideration the solubility of the compound in an organic solvent, R ¹ is preferably an aryl group having 6 to 14 carbon atoms, more preferably a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, still more preferably any of the above groups being a phenyl group, a 1-naphthyl group, or a 2-naphthyl group, and still more preferably any of the above groups being a phenyl group.

In consideration of the solubility of the compound in an organic solvent, ^R2 is preferably a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and even more preferably all hydrogen atoms.

In formula (1-1), the bonding positions of the three nitrogen atoms in the central carbazole skeleton and the carbazole rings of the arylcarbazole skeleton are not particularly limited, and they may be bonded at the same position or different positions, but as shown in formula (1-1A) or (1-1B) below, it is preferable for them to be bonded at the 3rd position (meta position) or 4th position (para position) relative to the nitrogen atom of the arylcarbazole skeleton, and it is more preferable for them to be bonded at the 3rd position.

（式中、Ｒ¹およびＲ²は、上記と同じ意味を表す。）

(In the formula, ^R1 and ^R2 have the same meanings as above.)

Arylamine compounds suitable for use in the present invention include those represented by the following formula (2) or (3), but are not limited thereto.

As shown in the scheme below, the arylamine compound represented by formula (1) or (1-1) can be produced by reacting a diaminocarbazole compound [Ia] or [Ib] with a halogenated arylcarbazole compound [II] in the presence of a catalyst.

（式中、Ｘは、ハロゲン原子または擬ハロゲン基を表し、Ｒ¹およびＲ²は、上記と同じ意味を表す。）

(In the formula, X represents a halogen atom or a pseudohalogen group, and ^R1 and ^R2 have the same meanings as above.)

（式中、Ｘ、Ｒ¹およびＲ²は、上記と同じ意味を表す。）

(In the formula, X, ^R1 and ^R2 have the same meanings as above.)

The halogen atom includes the same as those mentioned above.
Examples of the pseudohalogen group include (fluoro)alkylsulfonyloxy groups such as methanesulfonyloxy, trifluoromethanesulfonyloxy, and nonafluorobutanesulfonyloxy groups; and aromatic sulfonyloxy groups such as benzenesulfonyloxy and toluenesulfonyloxy groups.

The charging ratio of the diaminocarbazole compound [Ia] or [Ib] to the halogenated arylcarbazole compound [II] can be 5 equivalents or more of the halogenated arylcarbazole compound relative to the amount of all NH groups in the diaminocarbazole compound, but a ratio of about 5 to 5.5 equivalents is preferable.

Examples of the catalyst used in the above reaction include copper catalysts such as copper chloride, copper bromide, and copper iodide; and palladium catalysts such as Pd(PPh ₃ ) ₄ (tetrakis(triphenylphosphine)palladium), Pd(PPh ₃ ) ₂ Cl ₂ (bis(triphenylphosphine)dichloropalladium), Pd(dba) ₂ (bis(dibenzylideneacetone)palladium), Pd ₂ (dba) ₃ (tris(dibenzylideneacetone)dipalladium), Pd(P-t-Bu ₃ ) ₂ (bis(tri(t-butylphosphine))palladium), and Pd(OAc) ₂ (palladium acetate). These catalysts may be used alone or in combination of two or more. These catalysts may also be used together with a known appropriate ligand.

Examples of such ligands include tertiary phosphines such as triphenylphosphine, tri-o-tolylphosphine, diphenylmethylphosphine, phenyldimethylphosphine, trimethylphosphine, triethylphosphine, tributylphosphine, tri-t-butylphosphine, di-t-butyl(phenyl)phosphine, di-t-butyl(4-dimethylaminophenyl)phosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, and 1,1'-bis(diphenylphosphino)ferrocene; tertiary phosphites such as trimethylphosphite, triethylphosphite, and triphenylphosphite; JohnPhos, CyjohnPhos, DavePhos, XPhos, SPhos, tBuXPhos, RuPhos, Me4tBuXPhos, sSPhos, tBuMePhos, MePhos, Examples include biphenylphosphine compounds such as tBuDavePhos, PhDavePhos, 2'-Dicyclohexylphosphino-2,4,6-trimethoxybiphenyl, BrettPhos, tBuBrettPhos, AdBrettPhos, _Me3 (OMe)tBuXPhos, (2-Biphenyl)di-1-adamantylphosphine, RockPhos, and CPhos.

The amount of the catalyst used may be about 0.01 mol to about 0.5 mol, preferably about 0.05 to about 0.2 mol, per mol of the halogenated arylcarbazole compound [II].
When a ligand is used, the amount of the ligand used may be 0.1 to 5 equivalents relative to the metal complex used, and preferably 1 to 2 equivalents.

In addition, a base may be used in the above reaction. Examples of the base include alkali metals such as lithium, sodium, potassium, lithium hydride, sodium hydride, lithium hydroxide, potassium hydroxide, t-butoxylithium, t-butoxysodium, t-butoxypotassium, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogencarbonate, and potassium hydrogencarbonate, alkali metal hydrides, alkali metal hydroxides, alkoxy alkali metals, alkali metal carbonates, and alkali metal hydrogencarbonates; alkaline earth metal carbonates such as calcium carbonate; organic lithiums such as n-butyllithium, s-butyllithium, t-butyllithium, lithium diisopropylamide (LDA), lithium 2,2,6,6-tetramethylpiperidine (LiTMP), and lithium hexamethyldisilazane (LHMDS); and amines such as triethylamine, diisopropylethylamine, tetramethylethylenediamine, triethylenediamine, and pyridine.
When a base is used, the amount of the base used may be 0.1 to 5 equivalents relative to the halogenated arylcarbazole compound [II] used, and preferably 1 to 2 equivalents.

When all the raw materials are solid or from the viewpoint of efficiently obtaining the desired arylamine compound, each of the above reactions is carried out in a solvent. When using a solvent, there are no particular limitations on the type of solvent as long as it does not adversely affect the reaction. Specific examples include aliphatic hydrocarbons (pentane, n-hexane, n-octane, n-decane, decalin, etc.), halogenated aliphatic hydrocarbons (chloroform, dichloromethane, dichloroethane, carbon tetrachloride, etc.), aromatic hydrocarbons (benzene, nitrobenzene, toluene, o-xylene, m-xylene, p-xylene, mesitylene, etc.), halogenated aromatic hydrocarbons (chlorobenzene, bromobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, etc.), ethers (diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, dioxane, 1,2-dimeth- yl ether, tetrahydrofuran, dioxane, tetrahydrofuran, di ... Examples of suitable solvents include dimethyl ketones (dimethyl ether, 1,2-diethoxyethane, 1,2-diethoxyethane, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, di-n-butyl ketone, cyclohexanone, etc.), amides (N,N-dimethylformamide, N,N-dimethylacetamide, etc.), lactams and lactones (N-methylpyrrolidone, γ-butyrolactone, etc.), ureas (N,N-dimethylimidazolidinone, tetramethylurea, etc.), sulfoxides (dimethyl sulfoxide, sulfolane, etc.), and nitriles (acetonitrile, propionitrile, butyronitrile, etc.). These solvents may be used alone or in combination of two or more.

The reaction temperature may be appropriately set within the range from the melting point to the boiling point of the solvent used, but is preferably about 0 to 200°C, more preferably 20 to 150°C.
After completion of the reaction, the reaction mixture is worked up in a conventional manner to give the desired arylamine compound.

The above-mentioned arylamine compound of the present invention can be suitably used as a charge transporting material.In this case, it can be used as a charge transporting varnish containing the arylamine compound of the present invention and an organic solvent, and this charge transporting varnish may contain a dopant material for the purpose of improving the charge transporting ability, etc., depending on the application of the thin film obtained.In addition, the arylamine compound of the present invention can also be used in combination with other conventionally known charge transporting materials such as aniline derivatives and thiophene derivatives, but it is preferable to use the arylamine compound of the present invention alone as a charge transporting material.
In the present invention, the term "charge transporting property" is synonymous with "electrical conductivity." The charge transporting varnish may be one which itself has charge transporting property, or one which produces a solid film having charge transporting property.

There are no particular limitations on the dopant substance, so long as it dissolves in at least one solvent used in the varnish, and both inorganic and organic dopant substances can be used.
The inorganic and organic dopant substances may be used alone or in combination of two or more.
Furthermore, the dopant substance may be a substance whose function as a dopant substance is first expressed or improved by, for example, removing a part of its molecule due to an external stimulus, such as heating during baking, in the process of obtaining a charge-transporting thin film, which is a solid film, from the varnish, such as an arylsulfonate compound protected by a group from which the sulfonic acid group is easily removed.

In the present invention, heteropolyacids are particularly preferred as inorganic dopant substances.
Heteropolyacids are polyacids that have a structure in which a heteroatom is located at the center of the molecule, typically represented by a Keggin type chemical structure represented by formula (H1) or a Dawson type chemical structure represented by formula (H2), and are formed by condensing an isopolyacid, which is an oxyacid of vanadium (V), molybdenum (Mo), tungsten (W), etc., with an oxyacid of a different element. Examples of such oxyacids of different elements include oxyacids of silicon (Si), phosphorus (P), and arsenic (As).

Specific examples of heteropolyacids include phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid, phosphotungstomolybdic acid, etc., which may be used alone or in combination of two or more. These heteropolyacids are commercially available or can be synthesized by known methods.
In particular, when one type of heteropolyacid is used, the one type of heteropolyacid is preferably phosphotungstic acid or phosphomolybdic acid, and most preferably phosphotungstic acid. When two or more types of heteropolyacids are used, one of the two or more types of heteropolyacids is preferably phosphotungstic acid or phosphomolybdic acid, and more preferably phosphotungstic acid.
In addition, the heteropolyacid may be used in the present invention even if the number of elements in the structure represented by the general formula is large or small in quantitative analysis such as elemental analysis, as long as it is a commercially available product or is appropriately synthesized according to a known synthesis method.
That is, for example, phosphotungstic acid is generally represented by the chemical formula _H3 ( _{PW12O40 ) nH2O} , and phosphomolybdic acid is represented by the chemical formula _H3 ( _PMo12O40 ) _nH2O , but in quantitative analysis, even if the number of P ( _phosphorus ), O (oxygen), W (tungsten), or Mo (molybdenum) in this formula is large or small, they can be used in the present invention as long as they are commercially available or appropriately synthesized according to a known synthesis method. In this case, the mass of the heteropolyacid specified in the present invention does not mean the mass of pure phosphotungstic acid (phosphotungstic acid content) in a synthesized product or a commercially available product, but means the total mass in a state including hydration water and other impurities in a form available as a commercially available product or in a form that can be isolated by a known synthesis method.

The amount of heteropolyacid used can be, in mass ratio, about 0.001 to 50.0 per 1 charge transport substance, but is preferably about 0.01 to 20.0, and more preferably about 0.1 to 10.0.

On the other hand, as organic dopant substances, in particular, tetracyanoquinodimethane derivatives and benzoquinone derivatives can be used.
Specific examples of the tetracyanoquinodimethane derivative include 7,7,8,8-tetracyanoquinodimethane (TCNQ) and a halotetracyanoquinodimethane represented by the formula (H3).
Specific examples of benzoquinone derivatives include tetrafluoro-1,4-benzoquinone (F4BQ), tetrachloro-1,4-benzoquinone (chloranil), tetrabromo-1,4-benzoquinone, and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).

In the formula, R ⁵⁰⁰ to R ⁵⁰³ each independently represent a hydrogen atom or a halogen atom, and at least one of them is a halogen atom, preferably at least two of them are halogen atoms, more preferably at least three of them are halogen atoms, and most preferably all of them are halogen atoms.
Examples of the halogen atom include the same as those mentioned above, but a fluorine atom or a chlorine atom is preferred, and a fluorine atom is more preferred.

Specific examples of such halotetracyanoquinodimethanes include 2-fluoro-7,7,8,8-tetracyanoquinodimethane, 2-chloro-7,7,8,8-tetracyanoquinodimethane, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane, 2,5-dichloro-7,7,8,8-tetracyanoquinodimethane, 2,3,5,6-tetrachloro-7,7,8,8-tetracyanoquinodimethane, and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ).

The amount of the tetracyanoquinodimethane derivative and the benzoquinone derivative used is preferably 0.0001 to 100 equivalents, more preferably 0.01 to 50 equivalents, and even more preferably 1 to 20 equivalents relative to the charge transport substance.

In addition, as an organic dopant substance, electrically neutral onium borate salts consisting of a monovalent or divalent anion represented by the following formula (a1) and a counter cation represented by the formulas (c1) to (c5) can also be used.

（式中、Ａｒは、それぞれ独立して、置換基を有してもよい炭素数６～２０のアリール基または置換基を有してもよい炭素数２～２０のヘテロアリール基を表し、Ｌは、炭素数１～２０のアルキレン基、－ＮＨ－、酸素原子、硫黄原子または－ＣＮ⁺－を表す。）

(In the formula, each Ar independently represents an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 2 to 20 carbon atoms which may have a substituent, and L represents an alkylene group having 1 to 20 carbon atoms, -NH-, an oxygen atom, a sulfur atom, or -CN ⁺ -.)

In formula (a1), the alkylene group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methylene, methylmethylene, dimethylmethylene, ethylene, trimethylene, propylene, tetramethylene, pentamethylene, and hexamethylene groups. Examples of aryl and heteroaryl groups include those described above.

Suitable examples of the anion of formula (a1) above include, but are not limited to, those represented by formula (a2).

The amount of the onium borate salt used may be about 0.1 to 10 in terms of the mole ratio to the charge transporting substance.
The onium borate salt can be synthesized by referring to the known method described in, for example, JP-A-2005-314682.

In addition, arylsulfonic acid compounds and arylsulfonic acid ester compounds can also be suitably used as organic dopant substances.

Specific examples of arylsulfonic acid compounds include benzenesulfonic acid, tosylic acid, p-styrenesulfonic acid, 2-naphthalenesulfonic acid, 4-hydroxybenzenesulfonic acid, 5-sulfosalicylic acid, p-dodecylbenzenesulfonic acid, dihexylbenzenesulfonic acid, 2,5-dihexylbenzenesulfonic acid, dibutylnaphthalenesulfonic acid, 6,7-dibutyl-2-naphthalenesulfonic acid, dodecylnaphthalenesulfonic acid, 3-dodecyl-2-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 4-hexyl-1-naphthalenesulfonic acid, octylnaphthalenesulfonic acid, 2- ... Examples of the sulfonic acid include 1-octyl-1-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 7-hexyl-1-naphthalenesulfonic acid, 6-hexyl-2-naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, 2,7-dinonyl-4-naphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, 2,7-dinonyl-4,5-naphthalenedisulfonic acid, 1,4-benzodioxanedisulfonic acid compounds described in WO 2005/000832, arylsulfonic acid compounds described in WO 2006/025342, and arylsulfonic acid compounds described in WO 2009/096352.

Examples of preferred arylsulfonic acid compounds include arylsulfonic acid compounds represented by formula (H4) or (H5).

A ¹ represents O or S, with O being preferred.
^A2 represents a naphthalene ring or an anthracene ring, with a naphthalene ring being preferred.
^A3 represents a divalent to tetravalent perfluorobiphenyl group, p represents the number of bonds between ^A1 and ^A3 and is an integer satisfying 2≦p≦4, but it is preferable that ^A3 is a perfluorobiphenyldiyl group, preferably a perfluorobiphenyl-4,4'-diyl group, and p is 2.
q represents the number of sulfonic acid groups bonded to ^A2 and is an integer satisfying 1≦q≦4, with 2 being optimal.

A ⁴ to A ⁸ each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, or a halogenated alkenyl group having 2 to 20 carbon atoms, provided that at least three of A ⁴ to A ⁸ are halogen atoms.

Examples of halogenated alkyl groups having 1 to 20 carbon atoms include trifluoromethyl, 2,2,2-trifluoroethyl, 1,1,2,2,2-pentafluoroethyl, 3,3,3-trifluoropropyl, 2,2,3,3,3-pentafluoropropyl, 1,1,2,2,3,3,3-heptafluoropropyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl, 2,2,3,3,4,4,4-heptafluorobutyl, and 1,1,2,2,3,3,4,4,4-nonafluorobutyl groups.

Examples of the halogenated alkenyl group having 2 to 20 carbon atoms include perfluorovinyl, perfluoropropenyl (allyl), and perfluorobutenyl groups.
Other examples of the halogen atom and the alkyl group having 1 to 20 carbon atoms include those similar to those mentioned above, with the halogen atom being preferably a fluorine atom.

Among these, it is preferable that A ⁴ to A ⁸ are a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, or a halogenated alkenyl group having 2 to 10 carbon atoms, and at least three of A ⁴ to A ⁸ are fluorine atoms, and it is more preferable that A ⁴ to A ^{8 are a hydrogen atom, a fluorine atom, a cyano group, an alkyl group having 1 to 5 carbon atoms, a fluorinated alkyl group having 1 to 5 carbon atoms, or a fluorinated alkenyl group having 2 to 5 carbon atoms, and at least three of A 4 to A 8} are fluorine atoms, and it is even more preferable that A ⁴ , A ⁵ and A ⁸ are fluorine atoms.
The perfluoroalkyl group is an alkyl group in which all hydrogen atoms have been substituted with fluorine atoms, and the perfluoroalkenyl group is an alkenyl group in which all hydrogen atoms have been substituted with fluorine atoms.

r represents the number of sulfonic acid groups bonded to the naphthalene ring and is an integer satisfying 1≦r≦4, with 2 to 4 being preferred and 2 being optimal.

The molecular weight of the arylsulfonic acid compound used as a dopant substance is not particularly limited, but taking into consideration its solubility in organic solvents when used together with the arylamine compound of the present invention, it is preferably 2000 or less, more preferably 1500 or less.

Specific examples of suitable aryl sulfonic acid compounds are given below, but are not limited to these.

The amount of the arylsulfonic acid compound used is preferably about 0.01 to 20.0, more preferably about 0.4 to 5.0, per 1 part of the charge transporting substance (molar ratio).
Although commercially available arylsulfonic acid compounds may be used, they can also be synthesized by known methods described in WO 2006/025342, WO 2009/096352, and the like.

On the other hand, examples of arylsulfonic acid ester compounds include the arylsulfonic acid ester compounds disclosed in WO 2017/217455, the arylsulfonic acid ester compounds disclosed in WO 2017/217457, and the arylsulfonic acid ester compounds described in Japanese Patent Application No. 2017-243631. Specifically, those represented by any of the following formulae (H6) to (H8) are preferred.

（式中、ｍは、１≦ｍ≦４を満たす整数であるが、２が好ましい。ｎは、１≦ｎ≦４を満たす整数であるが、２が好ましい。）

(In the formula, m is an integer satisfying 1≦m≦4, and is preferably 2. n is an integer satisfying 1≦n≦4, and is preferably 2.)

In formula (H6), A ¹¹ is an m-valent group derived from perfluorobiphenyl.
A ¹² is —O— or —S—, with —O— being preferred.
A ¹³ is an (n+1)-valent group derived from naphthalene or anthracene, and is preferably a group derived from naphthalene.
R ^s1 to R ^s4 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ^s5 is an optionally substituted monovalent hydrocarbon group having 2 to 20 carbon atoms.

Specific examples of the linear or branched alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, and n-hexyl groups, with alkyl groups having 1 to 3 carbon atoms being preferred.
The monovalent hydrocarbon group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and t-butyl groups; and aryl groups such as phenyl, naphthyl, and phenanthryl groups.

In particular, among R ^s1 to R ^s4 , it is preferred that R ^s1 or R ^s3 is a linear alkyl group having 1 to 3 carbon atoms and the remainder is a hydrogen atom, or that R ^s1 is a linear alkyl group having 1 to 3 carbon atoms and R ^s2 to R ^s4 are hydrogen atoms. In this case, the linear alkyl group having 1 to 3 carbon atoms is preferably a methyl group.
Furthermore, R ^s5 is preferably a linear alkyl group having 2 to 4 carbon atoms or a phenyl group.

In formula (H7), A ¹⁴ is an optionally substituted hydrocarbon group having 6 to 20 carbon atoms, containing one or more aromatic rings, and having a valence of m, and this hydrocarbon group is a group obtained by removing m hydrogen atoms from a hydrocarbon compound having 6 to 20 carbon atoms and containing one or more aromatic rings.
Examples of such hydrocarbon compounds include benzene, toluene, xylene, ethylbenzene, biphenyl, naphthalene, anthracene, and phenanthrene.
In addition, the above-mentioned hydrocarbon groups may have some or all of their hydrogen atoms further substituted with a substituent. Examples of such substituents include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, nitro, cyano, hydroxy, amino, silanol, thiol, carboxy, sulfonate ester, phosphoric acid, phosphate ester, ester, thioester, amide, organooxy, organoamino, organosilyl, organothio, acyl, sulfo, and monovalent hydrocarbon groups.
Among these, A ¹⁴ is preferably a group derived from benzene, biphenyl, or the like.

Furthermore, A ¹⁵ is --O-- or --S--, with --O-- being preferred.
^A16 is an aromatic hydrocarbon group having 6 to 20 carbon atoms and a valence of (n+1), which is a group obtained by removing (n+1) hydrogen atoms from the aromatic ring of an aromatic hydrocarbon compound having 6 to 20 carbon atoms.
Examples of such aromatic hydrocarbon compounds include benzene, toluene, xylene, biphenyl, naphthalene, anthracene, and pyrene.
Among these, A ¹⁶ is preferably a group derived from naphthalene or anthracene, and more preferably a group derived from naphthalene.

R ^s6 and R ^s7 are each independently a hydrogen atom or a linear or branched monovalent aliphatic hydrocarbon group, and R ^s8 is a linear or branched monovalent aliphatic hydrocarbon group, provided that the total number of carbon atoms in R ^s6 , R ^s7 and R ^s8 is 6 or more. There is no particular upper limit to the total number of carbon atoms in R ^s6 , R ^s7 and R ^s8 , but it is preferably 20 or less, more preferably 10 or less.
Specific examples of the linear or branched monovalent aliphatic hydrocarbon group include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-hexyl, n-octyl, 2-ethylhexyl, and decyl groups; and alkenyl groups having 2 to 20 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-methyl-2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, and hexenyl groups.
Among these, R ^s6 is preferably a hydrogen atom, and R ^s7 and R ^s8 are each preferably an alkyl group having 1 to 6 carbon atoms.

In formula (H8), R ^s9 to R ^s13 each independently represent a hydrogen atom, a nitro group, a cyano group, a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, or a halogenated alkenyl group having 2 to 10 carbon atoms.
The alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups.

The halogenated alkyl group having 1 to 10 carbon atoms is not particularly limited as long as it is a group in which some or all of the hydrogen atoms of the alkyl group having 1 to 10 carbon atoms are substituted with halogen atoms, and specific examples include trifluoromethyl, 2,2,2-trifluoroethyl, 1,1,2,2,2-pentafluoroethyl, 3,3,3-trifluoropropyl, 2,2,3,3,3-pentafluoropropyl, 1,1,2,2,3,3,3-heptafluoropropyl, 4,4,4-trifluorobutyl, 3,3,4,4,4-pentafluorobutyl, 2,2,3,3,4,4,4-heptafluorobutyl, and 1,1,2,2,3,3,4,4,4-nonafluorobutyl groups.

The halogenated alkenyl group having 2 to 10 carbon atoms is not particularly limited as long as it is an alkenyl group having 2 to 10 carbon atoms in which some or all of the hydrogen atoms have been replaced with halogen atoms, and specific examples include perfluorovinyl, perfluoro-1-propenyl, perfluoro-2-propenyl, perfluoro-1-butenyl, perfluoro-2-butenyl, and perfluoro-3-butenyl groups.

Among these, R ^s9 is preferably a nitro group, a cyano group, a halogenated alkyl group having 1 to 10 carbon atoms, or a halogenated alkenyl group having 2 to 10 carbon atoms, more preferably a nitro group, a cyano group, a halogenated alkyl group having 1 to 4 carbon atoms, or a halogenated alkenyl group having 2 to 4 carbon atoms, and still more preferably a nitro group, a cyano group, a trifluoromethyl group, or a perfluoropropenyl group.
R ^s10 to R ^s13 are preferably a halogen atom, more preferably a fluorine atom.

A ¹⁷ is --O--, --S-- or --NH--, with --O-- being preferred.
^A18 is an aromatic hydrocarbon group having 6 to 20 carbon atoms and a valence of (n+1), which is a group obtained by removing (n+1) hydrogen atoms from the aromatic ring of an aromatic hydrocarbon compound having 6 to 20 carbon atoms.
Examples of such aromatic hydrocarbon compounds include benzene, toluene, xylene, biphenyl, naphthalene, anthracene, and pyrene.
Among these, A ¹⁸ is preferably a group derived from naphthalene or anthracene, more preferably a group derived from naphthalene.

R ^s14 to R ^s17 each independently represent a hydrogen atom or a linear or branched monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.
Specific examples of monovalent aliphatic hydrocarbon groups include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl groups; and alkenyl groups having 2 to 20 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-methyl-2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, and hexenyl groups. Of these, alkyl groups having 1 to 20 carbon atoms are preferred, alkyl groups having 1 to 10 carbon atoms are more preferred, and alkyl groups having 1 to 8 carbon atoms are even more preferred.

R ^s18 is a linear or branched monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or OR ^s19 . R ^s19 is an optionally substituted monovalent hydrocarbon group having 2 to 20 carbon atoms.
Examples of the linear or branched monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms for R ^s18 include the same as those mentioned above.
When R ^s18 is a monovalent aliphatic hydrocarbon group, R ^s18 is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably an alkyl group having 1 to 8 carbon atoms.
Examples of the monovalent hydrocarbon group having 2 to 20 carbon atoms for R ^s19 include the monovalent aliphatic hydrocarbon groups mentioned above except for methyl groups, as well as aryl groups such as phenyl, naphthyl, and phenanthryl groups.
Among these, R ^s19 is preferably a linear alkyl group having 2 to 4 carbon atoms or a phenyl group.
Examples of the substituent that the monovalent hydrocarbon group may have include a fluorine atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group, and a cyano group.

Specific examples of suitable aryl sulfonate ester compounds include, but are not limited to, those shown below.

The amount of the arylsulfonic acid ester compound used is, in terms of mole ratio, preferably about 0.01 to 20 parts by mass, and more preferably about 0.05 to 10 parts by mass, per 1 part by mass of the charge transporting substance.

In the present invention, in consideration of producing a charge transport thin film having excellent transparency and a high refractive index, it is preferable to use an aryl sulfonic acid compound or an aryl sulfonic acid ester compound as a dopant substance, and in consideration of solubility in a solvent and obtaining a thin film with a smaller extinction coefficient, it is more preferable to use an aryl sulfonic acid ester compound.

Furthermore, when the resulting thin film is used as a hole injection layer of an organic EL device, the charge transport varnish may contain an organosilane compound for the purpose of improving the injection into the hole transport layer and improving the life characteristics of the device. The content of the organosilane compound is usually about 1 to 30% by mass based on the total mass of the charge transport material and the dopant material.

As the organic solvent used in preparing the charge transport varnish of the present invention, a highly polar solvent capable of dissolving the arylamine compound of the present invention can be used. The arylamine compound of the present invention can be dissolved in a solvent regardless of the polarity of the solvent. If necessary, a low polar solvent may be used because it has better process compatibility than a high polar solvent. In the present invention, a low polar solvent is defined as a solvent having a relative dielectric constant of less than 7 at a frequency of 100 kHz, and a high polar solvent is defined as a solvent having a relative dielectric constant of 7 or more at a frequency of 100 kHz.

Examples of low polarity solvents include
Chlorinated solvents such as chloroform and chlorobenzene;
Aromatic hydrocarbon solvents such as toluene, xylene, tetralin, cyclohexylbenzene, and decylbenzene;
Aliphatic alcohol solvents such as 1-octanol, 1-nonanol, and 1-decanol;
Ether solvents such as tetrahydrofuran, dioxane, anisole, 4-methoxytoluene, 3-phenoxytoluene, dibenzyl ether, diethylene glycol dimethyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, and triethylene glycol butyl methyl ether;
Examples of the solvent include ester-based solvents such as methyl benzoate, ethyl benzoate, butyl benzoate, isoamyl benzoate, bis(2-ethylhexyl) phthalate, dibutyl maleate, dibutyl oxalate, hexyl acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

Examples of highly polar solvents include
Amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylisobutyramide, N-methylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone;
Ketone solvents such as ethyl methyl ketone, isophorone, and cyclohexanone;
Cyano-based solvents such as acetonitrile and 3-methoxypropionitrile;
Polyhydric alcohol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1,3-butanediol, and 2,3-butanediol;
monohydric alcohol solvents other than aliphatic alcohols, such as diethylene glycol monomethyl ether, diethylene glycol monophenyl ether, triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, benzyl alcohol, 2-phenoxyethanol, 2-benzyloxyethanol, 3-phenoxybenzyl alcohol, and tetrahydrofurfuryl alcohol;
Examples of the solvent include sulfoxide solvents such as dimethyl sulfoxide.

The viscosity of the charge-transporting varnish is determined appropriately depending on the thickness of the thin film to be produced and the solid content concentration, but is usually 1 to 50 mPa·s at 25° C. In the present invention, the solid content means the components other than the solvent contained in the charge-transporting varnish.
The solids concentration of the charge-transporting varnish is appropriately set taking into consideration the viscosity and surface tension of the varnish, the thickness of the thin film to be produced, and the like, but is usually about 0.1 to 10.0 mass %, and in consideration of improving the coatability of the varnish, it is preferably about 0.5 to 5.0 mass %, and more preferably about 1.0 to 3.0 mass %.

The method for preparing the charge transporting varnish is not particularly limited, but examples include a method in which a solid component such as a charge transporting substance containing the arylamine compound of the present invention is dissolved in a high polarity solvent and a low polarity solvent is added thereto, or a method in which a high polarity solvent and a low polarity solvent are mixed and the charge transporting substance is dissolved therein.

In particular, when preparing a charge-transporting varnish, in order to reproducibly obtain a thin film with higher flatness, it is desirable to dissolve the charge-transporting substance, dopant substance, etc. in an organic solvent and then filter the resultant solution using a sub-micrometer-order filter, etc.

The charge transporting varnish described above can be used to easily produce a charge transporting thin film, and is therefore suitable for use in producing electronic devices, particularly organic EL devices.
In this case, the charge transporting thin film can be formed by applying the above-mentioned charge transporting varnish onto a substrate and baking it.
The method for applying the varnish is not particularly limited, and examples thereof include dipping, spin coating, transfer printing, roll coating, brush coating, inkjet coating, spraying, and slit coating. It is preferable to adjust the viscosity and surface tension of the varnish depending on the application method.

In addition, the atmosphere in which the charge-transporting varnish is baked after application is not particularly limited, and a thin film with a uniform film surface and high charge transport properties can be obtained not only in an air atmosphere, but also in an inert gas such as nitrogen or in a vacuum. However, depending on the type of dopant substance used, a thin film with charge transport properties may be reproducibly obtained by baking the varnish in an air atmosphere.

The baking temperature is appropriately set within a range of about 100 to 260° C., taking into consideration the use of the resulting thin film, the degree of charge transport property to be imparted to the resulting thin film, the type and boiling point of the solvent, etc. For example, when the resulting thin film is used as a hole injection layer of an organic EL device, a baking temperature of about 140 to 250° C. is preferable, and about 145 to 240° C. is more preferable. However, when the arylamine compound represented by the above-mentioned formula (1) is used as the charge transport material, a thin film having good charge transport property can be obtained even by baking at a low temperature of 200° C. or less.
During firing, the temperature may be changed in two or more stages in order to achieve a more uniform film formation or to promote the reaction on the substrate. Heating may be performed using a suitable device such as a hot plate or an oven.

The thickness of the charge transport thin film is not particularly limited, but when used as a functional layer provided between the anode and the light-emitting layer of an organic EL element, such as a hole injection layer, hole transport layer, or hole injection transport layer, a thickness of 5 to 300 nm is preferable. Methods for changing the film thickness include changing the solids concentration in the varnish and changing the amount of solution on the substrate during application.

The charge transport thin film of the present invention described above typically exhibits a refractive index (n) of 1.50 or more and an extinction coefficient (k) of 0.10 or less, averaged over the wavelength region of 400 to 800 nm, but in some embodiments exhibits a refractive index (n) of 1.60 or more, and in some other embodiments exhibits a refractive index (n) of 1.70 or more, and in some embodiments exhibits an extinction coefficient (k) of 0.07 or less, and in some other embodiments exhibits an extinction coefficient (k) of 0.02 or less.

When the charge transporting thin film is applied to an organic EL element, the organic EL element may be configured to include the charge transporting thin film between a pair of electrodes.
Representative configurations of the organic EL element include, but are not limited to, the following (a) to (f). In the following configurations, an electron blocking layer or the like can be provided between the light-emitting layer and the anode, and a hole blocking layer or the like can be provided between the light-emitting layer and the cathode, if necessary. In addition, the hole injection layer, the hole transport layer, or the hole injection transport layer may also function as an electron blocking layer, etc., and the electron injection layer, the electron transport layer, or the electron injection transport layer may also function as a hole blocking layer, etc. Furthermore, an arbitrary functional layer can be provided between each layer, if necessary.
(a) anode/hole injection layer/hole transport layer/light emitting layer/electron transport layer/electron injection layer/cathode (b) anode/hole injection layer/hole transport layer/light emitting layer/electron injection transport layer/cathode (c) anode/hole injection transport layer/light emitting layer/electron transport layer/electron injection layer/cathode (d) anode/hole injection transport layer/light emitting layer/electron injection transport layer/cathode (e) anode/hole injection layer/hole transport layer/light emitting layer/cathode (f) anode/hole injection transport layer/light emitting layer/cathode

The "hole injection layer", "hole transport layer" and "hole injection transport layer" are layers formed between the light emitting layer and the anode, and have the function of transporting holes from the anode to the light emitting layer. When only one layer of a hole transport material is provided between the light emitting layer and the anode, it is the "hole injection transport layer". When two or more layers of a hole transport material are provided between the light emitting layer and the anode, the layer closest to the anode is the "hole injection layer" and the other layers are the "hole transport layers". In particular, for the hole injection (transport) layer, a thin film is used that is excellent not only in the ability to accept holes from the anode but also in the ability to inject holes into the hole transport (light emitting) layer.
The terms "electron injection layer", "electron transport layer" and "electron injection transport layer" refer to a layer formed between a light-emitting layer and a cathode, and having the function of transporting electrons from the cathode to the light-emitting layer. When only one layer of an electron transporting material is provided between the light-emitting layer and the cathode, it is the "electron injection transport layer". When two or more layers of an electron transporting material are provided between the light-emitting layer and the cathode, the layer closest to the cathode is the "electron injection layer" and the other layers are "electron transport layers".
The "light-emitting layer" is an organic layer having a light-emitting function, and contains a host material and a dopant material when a doping system is adopted. In this case, the host material mainly has a function of promoting the recombination of electrons and holes and confining the excitons in the light-emitting layer, and the dopant material has a function of efficiently emitting the excitons obtained by the recombination. In the case of a phosphorescent element, the host material mainly has a function of confining the excitons generated by the dopant in the light-emitting layer.

The charge transport thin film of the present invention can be used as a functional layer provided between an anode and an emitting layer in an organic EL element, but is suitable as a hole injection layer, a hole transport layer, or a hole injection transport layer, is more suitable as a hole injection layer or a hole transport layer, and is even more suitable as a hole injection layer.

When an EL device is produced using the charge transporting varnish of the present invention, the materials to be used and the production method thereof are as follows, but are not limited thereto.
An example of a method for producing an OLED element having a hole injection layer made of a thin film obtained from the charge transport varnish of the present invention is as follows. It is preferable to previously perform a surface treatment on the electrodes, such as cleaning with alcohol, pure water, or the like, or a UV ozone treatment or oxygen plasma treatment, within a range that does not adversely affect the electrodes.
A hole injection layer made of the charge transport thin film of the present invention is formed on an anode substrate by the above method. This is introduced into a vacuum deposition apparatus, and a hole transport layer, a light emitting layer, an electron transport layer, an electron transport layer/hole blocking layer, and a cathode metal are sequentially deposited. Alternatively, instead of forming the hole transport layer and the light emitting layer by deposition in this method, these layers are formed by a wet process using a hole transport layer forming composition containing a hole transport polymer and a light emitting layer forming composition containing a light emitting polymer. If necessary, an electron blocking layer may be provided between the light emitting layer and the hole transport layer.

Examples of anode materials include transparent electrodes such as indium tin oxide (ITO) and indium zinc oxide (IZO), and metal anodes made of metals such as aluminum or alloys thereof, and it is preferable to use those that have been subjected to a planarization treatment. Polythiophene derivatives and polyaniline derivatives having high charge transport properties can also be used.
Other metals constituting the metal anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.

Materials that form the hole transport layer include triarylamines such as (triphenylamine) dimer derivatives, [(triphenylamine) dimer] spiro dimer, N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (α-NPD), 4,4',4"-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA), and 4,4',4"-tris[1-naphthyl(phenyl)amino]triphenylamine (1-TNATA), and oligothiophenes such as 5,5"-bis-{4-[bis(4-methylphenyl)amino]phenyl}-2,2':5',2"-terthiophene (BMA-3T).

Examples of materials for forming the light-emitting layer include, but are not limited to, low-molecular-weight light-emitting materials such as metal complexes such as aluminum complexes of 8-hydroxyquinoline, metal complexes of 10-hydroxybenzo[h]quinoline, bisstyrylbenzene derivatives, bisstyrylarylene derivatives, metal complexes of (2-hydroxyphenyl)benzothiazole, and silole derivatives; and systems in which a light-emitting material and an electron transfer material are mixed into a polymer compound such as poly(p-phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly(3-alkylthiophene), or polyvinylcarbazole.
In addition, when forming a light-emitting layer by vapor deposition, it may be co-deposited with a light-emitting dopant. Examples of the light-emitting dopant include, but are _not limited to, metal complexes such as tris(2-phenylpyridine)iridium(III) (Ir(ppy)), naphthacene derivatives such as rubrene, quinacridone derivatives, and condensed polycyclic aromatic rings such as perylene.

Materials for forming the electron transport layer/hole blocking layer include, but are not limited to, oxydiazole derivatives, triazole derivatives, phenanthroline derivatives, phenylquinoxaline derivatives, benzimidazole derivatives, pyrimidine derivatives, etc.

Materials for forming the electron injection layer include, but are not limited to, metal oxides such as lithium oxide ( _Li2O ), magnesium oxide ( _MgO ), and alumina ( _Al2O3 ), and metal fluorides such as lithium fluoride (LiF) and sodium fluoride (NaF).
Cathode materials include, but are not limited to, aluminum, magnesium-silver alloy, aluminum-lithium alloy, and the like.
Examples of materials for forming the electron blocking layer include, but are not limited to, tris(phenylpyrazole)iridium.

Hole transport polymers include poly[(9,9-dihexylfluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,4-diaminophenylene)], poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,1'-biphenylene-4,4-diamine)], poly[(9,9-bis{1'-penten-5'-yl}fluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,4-diaminophenylene)], and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine]-endcapped with Examples of the polysiloxane include poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(p-butylphenyl))diphenylamine)].

Examples of luminescent polymers include polyfluorene derivatives such as poly(9,9-dialkylfluorene) (PDAF), polyphenylenevinylene derivatives such as poly(2-methoxy-5-(2'-ethylhexoxy)-1,4-phenylenevinylene) (MEH-PPV), polythiophene derivatives such as poly(3-alkylthiophene) (PAT), and polyvinylcarbazole (PVCz).

As described above, the charge transport varnish of the present invention is suitable for use in forming functional layers such as a hole injection layer, a hole transport layer, and a hole injection transport layer that are provided between the anode and the light-emitting layer of an organic EL element, but can also be used to form charge transport thin films in electronic elements such as organic photoelectric conversion elements, organic thin-film solar cells, organic perovskite photoelectric conversion elements, organic integrated circuits, organic field effect transistors, organic thin-film transistors, organic light-emitting transistors, organic optical inspectors, organic photoreceptors, organic field quenching elements, light-emitting electrochemical cells, quantum dot light-emitting diodes, quantum lasers, organic laser diodes, and organic plasmon light-emitting elements.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The apparatus used is as follows.
(1) MALDI-TOF-MS: Bruker Autoflex III Smartbeam
(2) ¹ H-NMR: JNM-ECP300 FT NMR SYSTEM manufactured by JEOL Ltd.
(3) Substrate cleaning: Substrate cleaning equipment (low pressure plasma method) manufactured by Choshu Sangyo Co., Ltd.
(4) Coating of varnish: Spin coater MS-A100 manufactured by Mikasa Co., Ltd.
(5) Film thickness measurement: Microscopic shape measuring instrument Surfcorder ET-4000 manufactured by Kosaka Laboratory Co., Ltd.
(6) Fabrication of element: Multi-function deposition system C-E2L1G1-N manufactured by Choshu Sangyo Co., Ltd.
(7) Measurement of current density and luminance of the element: Multi-channel IVL measuring device manufactured by EHC Corporation (8) Measurement of lifetime of EL element (luminance half-life measurement): Organic EL luminance lifetime evaluation system PEL-105S manufactured by EHC Corporation
(9) Measurement of refractive index (n) and extinction coefficient (k): Multi-angle spectroscopic ellipsometer VASE manufactured by J.A. Woollam Japan

[1] Preparation of arylamine compound [Example 1-1] Synthesis of arylamine compound A

In a four-neck flask, 0.3 g of 3,6-diaminocarbazole, 2.570 g of 2-bromophenylcarbazole, 0.086 g of Pd ₂ (dba) ₂ , 0.087 g of [(tBu) ₃ PH]BF ₄ , 1.05 g of tBuONa, and 10 g of toluene were placed and stirred at 80°C for 3 hours. The mixture was then returned to room temperature and filtered through Celite. Toluene and saturated saline were added to the filtrate, and the aqueous layer was removed. An appropriate amount of MgSO ₄ was added to the obtained organic layer and the mixture was allowed to stand at room temperature for 10 minutes. MgSO ₄ was filtered through silica gel, and the filtrate was concentrated. The obtained concentrated liquid was dropped into a mixed solvent of ethyl acetate and methanol, and the mixture was stirred at room temperature for 30 minutes, after which the precipitated solid was filtered off. The obtained solid was dried to obtain 0.82 g of arylamine compound A (yield 38%).

¹ H-NMR (500 MHz, THF-d ₈ ) δ [ppm]: 7.95-7.92 (m, 10H), 7.72-7.55 (m, 20H), 7.54-7.41 (m, 5H), 7.35-7.20 (m, 25H), 7.16-7.09 (m, 6H).

[Example 1-2] Synthesis of arylamine compound B

In a four-neck flask, 0.502 g of 3,6-diaminocarbazole, 4.441 g of 3-bromophenylcarbazole, 0.037 g of Pd ₂ (dba) ₂ , 0.037 g of [(tBu) ₃ PH]BF ₄ , 1.346 g of tBuONa, and 15 g of toluene were placed and stirred at 80° C. for 5.5 hours. After the reaction was completed, the mixture was filtered through Celite and the target product was concentrated by silica gel chromatography. The activator was added to the concentrate and stirred at room temperature for 1 hour, after which the activated carbon was removed by Celite filtration. The obtained filtrate was dropped into a mixed solvent of ethyl acetate and methanol and stirred at room temperature for 1 hour. The precipitated solid was filtered off and the obtained solid was dried to obtain 3.50 g of arylamine compound B (yield 98%).

¹ H-NMR (500 MHz, THF-d ₈ ) δ [ppm]: 8.12-7.92 (m, 10H), 7.85-7.67 (m, 20H), 7.66-7.53 (m, 5H), 7.37-7.24 (m, 25H), 7.19-7.10 (m, 6H).

[2] Preparation of charge-transporting varnish [Example 2-1]
The arylamine compound A (0.027 g) obtained in Example 1-1 and the arylsulfonic acid ester A (0.024 g) represented by the following formula, which was synthesized according to the method described in WO 2017/217455, were added to chloroform (10 g), and the solution obtained by stirring at room temperature to dissolve was filtered through a syringe filter having a pore size of 0.2 μm to obtain a charge-transporting varnish A1.

[Example 2-2]
A charge-transporting varnish B1 was obtained in the same manner as in Example 2-1, except that the arylamine compound A was changed to the arylamine compound B obtained in Example 1-2.

[Example 2-3]
A charge-transporting varnish A2 was obtained in the same manner as in Example 2-1, except that the amount of arylamine compound A used was changed to 0.040 g.

[Example 2-4]
A charge-transporting varnish B2 was obtained in the same manner as in Example 2-2, except that the amount of arylamine compound B was changed to 0.040 g.

[3] Thin film production and film property evaluation [Examples 3-1 and 3-2]
The varnishes obtained in Examples 2-1 and 2-2 were each applied to a quartz substrate using a spin coater, dried at 120°C for 1 minute in air baking, and then baked at 200°C for 15 minutes in air atmosphere to form a uniform thin film of 50 nm on the quartz substrate.
Using the obtained quartz substrate with the film, the average refractive index n in the visible region and the average extinction coefficient k in the visible region at wavelengths of 400 to 800 nm were measured. The results are shown in Table 1.

As shown in Table 1, the thin film obtained from the charge transport varnish of the present invention has a high refractive index and a low extinction coefficient.

[4] Fabrication and Characterization of Hole-Only Device (HOD) 1 [Preparation of Solution for Forming Hole Injection Layer]
0.137 g of the aniline derivative represented by formula (T) synthesized according to the method described in WO 2013/084664 and 0.271 g of the arylsulfonic acid represented by formula (N) synthesized according to the method described in WO 2006/025342 were dissolved in 6.7 g of 1,3-dimethyl-2-imidazolidinone under a nitrogen atmosphere. 10 g of cyclohexanol and 3.3 g of propylene glycol were added to the obtained solution in this order and stirred to prepare a solution for forming a hole injection layer.

[Example 4-1]
As the ITO substrate, a 25 mm x 25 mm x 0.7 t glass substrate with indium tin oxide (ITO) patterned on the surface with a film thickness of 150 nm was used, and impurities on the surface were removed using an _O2 plasma cleaning device (150 W, 30 seconds) before use. Next, the hole injection layer forming solution prepared as above was applied to the ITO substrate by spin coating, heated to 80 ° C on a hot plate in the air and dried for 1 minute, and then heated and baked at 230 ° C for 15 minutes to form a hole injection layer (film thickness: 30 nm).
Next, the charge transporting varnish A2 obtained in Example 2-3 was applied onto the hole injection layer using a spin coater, and then baked in the air at 130° C. for 10 minutes to form a 40 nm hole transporting thin film.
An 80 nm-thick aluminum thin film was formed thereon at 0.2 nm/sec using a deposition apparatus (vacuum degree 1.0×10 ⁻⁵ Pa) to obtain a hole-only device (HOD).

[Example 4-2]
An HOD was prepared in the same manner as in Example 4-1, except that the charge-transporting varnish B2 obtained in Example 2-4 was used instead of the charge-transporting varnish A2.

The current density of the HOD fabricated above was measured at a driving voltage of 4 V. The results are shown in Table 2.

As shown in Table 2, it can be seen that the thin film prepared from the charge transport varnish of the present invention exhibits excellent charge transport properties as a hole transport layer.

[5] Preparation of single-layer element (SLD) [Example 5-1]
The charge transporting varnish A1 obtained in Example 2-1 was applied by spin coating onto an ITO substrate similar to that of Example 4-1, and the substrate was dried at 120°C for 1 minute under atmospheric baking, and then further baked at 200°C for 15 minutes under atmospheric baking to form a hole injection layer (film thickness: 50 nm).
An 80 nm-thick aluminum thin film was formed thereon at 0.2 nm/sec using a deposition apparatus (vacuum degree 1.0×10 ⁻⁵ Pa) to obtain a single layer element (SLD).

[Example 5-2]
An SLD was produced in the same manner as in Example 5-1, except that the charge transporting varnish A2 obtained in Example 2-2 was used instead of the charge transporting varnish A1.

The current density of the SLD fabricated above was measured at a driving voltage of 4 V. The results are shown in Table 3.

As shown in Table 3, it can be seen that the thin films prepared from the charge transport varnish of the present invention exhibit good charge transport properties.

[6] Preparation of HOD2 [Example 6-1]
The charge transporting varnish A1 obtained in Example 2-1 was applied onto an ITO substrate similar to that of Example 4-1 using a spin coater, and the coating was dried at 120° C. for 1 minute in the atmosphere, and then baked at 200° C. for 15 minutes to form a hole injection layer (film thickness: 50 nm).
On top of that, thin films of α-NPD and aluminum were successively laminated using a deposition apparatus (vacuum degree 2.0×10 ⁻⁵ Pa) to obtain HOD. The deposition was performed at a deposition rate of 0.2 nm/sec. The thicknesses of the thin films of α-NPD and aluminum were 30 nm and 80 nm, respectively.

[Example 6-2]
An HOD was prepared in the same manner as in Example 6-1, except that the charge transporting varnish A2 obtained in Example 2-2 was used instead of the charge transporting varnish A1.

The current density of the HOD fabricated above was measured at a driving voltage of 4 V. The results are shown in Table 4.

As shown in Table 4, it can be seen that the thin film prepared from the charge transport varnish of the present invention, as a hole injection layer, exhibits good hole injection properties into the hole transport layer.

[7] Preparation of organic EL element and evaluation of its characteristics [Example 7-1]
The charge transporting varnish A1 obtained in Example 2-1 was applied onto an ITO substrate similar to that of Example 4-1 using a spin coater, and the coating was dried at 120° C. for 1 minute in the atmosphere, and then baked at 200° C. for 15 minutes to form a thin film of 50 nm.
Next, a 30 nm film of α-NPD was formed on the ITO substrate on which the thin film was formed at 0.2 nm/sec using a vapor deposition apparatus (vacuum degree 1.0×10 ⁻⁵ Pa). Next, a 10 nm film of an electron block material HTEB-01 manufactured by Kanto Chemical Co., Ltd. was formed. Next, an emission layer host material NS60 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. and an emission layer dopant material Ir(ppy) ₃ were co-deposited. The vapor deposition rate of the co-deposition was controlled so that the concentration of Ir(ppy) ₃ was 6%, and a 40 nm film was laminated. Next, thin films of Alq ₃ , lithium fluoride, and aluminum were sequentially laminated to obtain an organic EL device. At this time, the vapor deposition rate was 0.2 nm/sec for Alq ₃ and aluminum, and 0.02 nm/sec for lithium fluoride, respectively, and the film thicknesses were 20 nm, 0.5 nm, and 80 nm, respectively.
In order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the organic EL element was sealed with a sealing substrate before evaluating its characteristics. Sealing was performed according to the following procedure. In a nitrogen atmosphere with an oxygen concentration of 2 ppm or less and a dew point of -76°C or less, the organic EL element was placed between the sealing substrates, and the sealing substrates were bonded together with an adhesive (MORESCO Moisture Cut WB90US(P) manufactured by MORESCO Corporation). At this time, a moisture scavenger (HD-071010W-40 manufactured by DYNIC Co., Ltd.) was placed in the sealing substrate together with the organic EL element. The bonded sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation amount: 6,000 mJ/cm ² ), and then annealed at 80°C for 1 hour to harden the adhesive.

[Example 7-2]
An organic EL element was produced in the same manner as in Example 7-1, except that the charge transporting varnish A2 obtained in Example 2-2 was used instead of the charge transporting varnish A1.

The organic EL device thus obtained was measured for driving voltage, current density, current efficiency, luminous efficiency, external luminescence quantum yield (EQE), and LT85 (the time required for the initial luminance of 5,000 cd/ ^m2 to decrease by 15%) when emitting light at 5,000 cd/ ^m2 . The results are shown in Table 5.

As shown in Table 5, all of the organic EL elements of the present invention exhibit high current efficiency and high EQE, as well as good life characteristics.

Claims (13)

An arylamine compound represented by the following formula (1):

(In the formula, each R ¹ independently represents an aryl group having 6 to 20 carbon atoms, and each R ² independently represents a hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.) The arylamine compound according to claim 1, represented by the following formula (1-1):

(In the formula, ^R1 and ^R2 have the same meanings as defined above.) The arylamine compound according to claim 2, represented by the following formula (1-1A) or (1-1B):

(In the formula, ^R1 and ^R2 have the same meanings as defined above.) The arylamine compound according to any one of claims 1 to 3, wherein R ¹ is a phenyl group, a 1-naphthyl group or a 2-naphthyl group. The arylamine compound according to claim 4, wherein all of the R ¹ 's are phenyl groups. The arylamine compound according to any one of claims 1 to 5, wherein all of the R ² 's are hydrogen atoms. A charge transporting varnish comprising the arylamine compound according to any one of claims 1 to 6 and an organic solvent. The charge transport varnish according to claim 7, which contains a dopant substance. The charge transport varnish according to claim 8, wherein the dopant substance is an arylsulfonic acid ester compound. A charge transporting thin film produced using the charge transporting varnish described in any one of claims 7 to 9. An electronic device comprising the charge transport thin film according to claim 10. An organic electroluminescence device comprising the charge transport thin film according to claim 10. The organic electroluminescence element according to claim 12, wherein the charge transport thin film is a hole injection layer or a hole transport layer.