JP7823652B2 - Charge-transporting varnish - Google Patents

Description

The present invention relates to a charge transport varnish.

In organic electroluminescence (hereinafter referred to as organic EL) devices, organic functional films made of organic compounds are used as the light-emitting layer and charge injection layer. In particular, the hole injection layer is responsible for transferring charges between the anode and the hole transport layer or light-emitting layer, and plays an important role in achieving low-voltage operation and high brightness of the organic EL device.
Methods for forming hole injection layers are roughly divided into dry processes, typified by vapor deposition, and wet processes, typified by spin coating. Comparing these processes, wet processes are more efficient at producing thin films with high flatness over large areas. Therefore, as organic EL displays are currently being made larger, there is a demand for hole injection layers that can be formed by wet processes, and technology related to hole injection materials that can be formed by wet processes has been reported (Patent Document 1).

Furthermore, because coloration of a charge-transporting thin film used in an organic EL element reduces the color purity and color reproducibility of the organic EL element, it is desirable for the charge-transporting thin film for an organic EL element to have high transmittance in the visible region and high transparency.
In this regard, the present applicant has already reported that highly transparent charge-transporting thin films can be obtained by adding nanoparticles of metal oxides such as silica and zirconia to a composition for forming a charge-transporting thin film (see Patent Documents 2 and 3).

However, the charge transport thin films in Patent Documents 2 and 3 contain metal oxide nanoparticles, which are insulating materials. Therefore, if the content of metal oxide nanoparticles is increased or the film is made thicker to improve the transparency of the film, the electrical properties of the charge transport thin film will deteriorate, and improvements in this area are needed.

International Publication No. 2008/032616 International Publication No. 2019/124413 International Publication No. 2020/262418

The present invention was made in consideration of the above circumstances, and aims to provide a charge transport varnish that provides a charge transport thin film with excellent transparency and electrical properties.

As a result of extensive research to solve the above-mentioned problems, the inventors discovered that a charge-transporting thin film with excellent transparency and electrical properties can be obtained by using a charge-transporting varnish containing metal oxide nanoparticles that have been surface-treated with a silane coupling agent having conductive functional groups, and thus completed the present invention.

That is, the present invention provides:
1. A charge-transporting varnish comprising a charge-transporting substance, a dopant substance, metal oxide nanoparticles surface-treated with a silane coupling agent having a conductive functional group, and a solvent;
2. The charge-transporting varnish of 1, wherein the silane coupling agent is a compound represented by the following formula (S1):
(In the formula, R represents an alkyl group having 1 to 10 carbon atoms, ^A1 represents a single bond or an alkylene group having 1 to 10 carbon atoms, ^A2 represents a single bond or a divalent linking group other than an alkylene group, and ^A3 represents a monovalent organic group having a conductive functional group.)
3. The charge transporting varnish of 2, wherein R represents an alkyl group having 1 to 5 carbon atoms, A ¹ represents an alkylene group having 2 to 5 carbon atoms, A ² represents —O—, —S—, —NH—, an amide bond, or a urea bond, and A ³ represents an aryl group having a phenylcarbazole structure.
4. The charge-transporting varnish of 3, wherein the silane coupling agent is a compound represented by the following formula (S1-1):
(In the formula, R represents an alkyl group having 1 to 5 carbon atoms, A ¹ represents an alkylene group having 2 to 5 carbon atoms, and A ⁴ represents an arylene group.)
5. The charge-transporting varnish according to any one of 1 to 4, wherein the metal oxide nanoparticles are at least one selected from silica and zirconia.
6. The charge-transporting varnish according to any one of 1 to 5, wherein the charge-transporting substance is an arylamine derivative.
7. The charge-transporting varnish according to any one of 1 to 6, wherein the dopant substance is an arylsulfonic acid compound.
8. A charge-transporting thin film obtained from the charge-transporting varnish according to any one of 1 to 7.
9. An electronic device comprising the charge transport thin film of 8.
10. An organic EL device comprising the charge transport thin film of 8.
11. The organic EL device of 10, wherein the charge transporting thin film is a hole injection layer or a hole transport layer.

The charge-transporting varnish of the present invention contains metal oxide nanoparticles that have been surface-treated with a silane coupling agent having a conductive functional group, and therefore not only provides a charge-transporting thin film with excellent transparency and electrical properties, but also provides a charge-transporting thin film that maintains the transparency that is the effect of adding particles and suppresses deterioration in electrical properties, even when the amount of metal oxide nanoparticles added is increased.
The charge transporting varnish of the present invention having such properties can be suitably used for producing thin films for electronic devices such as organic EL devices, particularly thin films for organic EL displays.

FIG. 1 is a diagram showing the average transmittance of quartz substrates with 50 nm thin films obtained in Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2 in the range of 400 to 800 nm. FIG. 10 is a graph showing the average transmittance of the quartz substrates with 100 nm thin films obtained in Examples 2-3 to 2-4 and Comparative Examples 2-3 to 2-4 in the range of 400 to 800 nm. FIG. 10 is a diagram showing the average transmittance of the quartz substrates with a 50 nm thin film obtained in Examples 2-5 to 2-8 and Comparative Examples 2-5 to 2-6 in the range of 400 to 800 nm.

The present invention will be described in more detail below.
The charge-transporting varnish according to the present invention is characterized by comprising a charge-transporting substance, a dopant substance, metal oxide nanoparticles that have been surface-treated with a silane coupling agent having a conductive functional group (hereinafter, also referred to as surface-treated metal oxide nanoparticles), and a solvent.
In the present invention, the term "charge transportability" is synonymous with "electrical conductivity" and "hole transportability." The charge transporting varnish may itself have charge transportability, or the solid film obtained from the varnish may have charge transportability.

[1] Surface-treated metal oxide nanoparticles Metal oxide nanoparticles that are surface-treated with a silane coupling agent having a conductive functional group, which are a characteristic component of the charge-transporting varnish of the present invention, are made capable of forming a conductive path with a charge-transporting substance by treating the surface of metal oxide nanoparticles, which are normally insulating, with a silane coupling agent having a conductive functional group.
The term "nanoparticles" refers to fine particles whose primary particles have an average particle size on the order of nanometers (typically 500 nm or less). The term "metal oxide nanoparticles" refers to metal oxides formed into nanoparticles.

In the present invention, the primary particle diameter of the metal oxide nanoparticles is not particularly limited as long as it is nano-sized, but is typically 5 nm or more, and from the viewpoint of ensuring good particle dispersibility and ease of production, it is typically 200 nm or less, preferably 100 nm or less, and more preferably 30 nm or less.

The metals constituting the metal oxide nanoparticles include metals in the usual sense as well as semimetals.
The metal in the ordinary sense is not particularly limited, but may include one or more selected from the group consisting of tin (Sn), titanium (Ti), aluminum (Al), zirconium (Zr), zinc (Zn), niobium (Nb), tantalum (Ta), and W (tungsten).
On the other hand, a metalloid refers to an element whose chemical and/or physical properties are intermediate between those of a metal and a nonmetal. Although a universal definition of a metalloid has not been established, in the present invention, a total of six elements, namely, boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te), are defined as metalloids. These metalloids may be used alone or in combination with two or more of them, or may be used in combination with metals in the usual sense.

In particular, the metal oxide nanoparticles preferably contain an oxide of one or more metals selected from boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), tin (Sn), titanium (Ti), aluminum (Al), zirconium (Zr), zinc (Zn), niobium (Nb), tantalum (Ta), and tungsten (W). When two or more metals are used in combination, the metal oxide may be a mixture of oxides of individual metals or a composite oxide containing multiple metals.

Specific examples of metal oxides include _B2O3 , _B2O , _SiO2 , SiO, GeO2, _GeO , _As2O4 , _As2O3 , _As2O5 , Sb2O3, _Sb2O5 , _TeO2 , _SnO2 , _ZrO2 , _Al2O3 , and _ZnO , _{and B2O3, B2O , SiO2 , SiO} , _GeO2 , _GeO , _{As2O4 , As2O3} , _As2O5 , _SnO2 , _SnO , _Sb2O3 , _{TeO2 , TiO2 , and} mixtures thereof are preferred _{, and SiO2 , ZrO 2} is more preferred.

Silane coupling agents having conductive functional groups that can be used as surface treatment agents include, for example, silane coupling agents having an alkoxysilyl group and a conductive functional group. However, in the present invention, silane coupling agents having trialkoxysilyl groups are preferred, and compounds having trialkoxysilyl groups represented by the following formula (S1) are preferably used.

In formula (S1), R represents an alkyl group having 1 to 10 carbon atoms, ^A1 represents a single bond or an alkylene group having 1 to 10 carbon atoms, ^A2 represents a single bond or a divalent linking group other than an alkylene group, and ^A3 represents a monovalent organic group having a conductive functional group.

The alkyl group having 1 to 10 carbon atoms represented by R may be linear, branched, or cyclic, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups. Among these, alkyl groups having 1 to 5 carbon atoms are preferred, alkyl groups having 1 to 3 carbon atoms are more preferred, and methyl and ethyl groups are even more preferred.
The alkylene group having 1 to 10 carbon atoms for ^A1 may be linear, branched, or cyclic. Specific examples thereof include methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, and decylene groups. Among these, alkylene groups having 2 to 5 carbon atoms are preferred, alkyl groups having 2 to 4 carbon atoms are more preferred, and ethylene and trimethylene groups are even more preferred.

Examples of the divalent linking group for ^A2 include -O-, -S-, -O-( _CH2 ) _k- O-, -S-(CH2)k _- S-, -O-( _CH2 ) _k -S-, -S-( _CH2 ) _{k -} O- (in these formulas, k represents an integer of 1 to 5), -NH-, -CO-, -NHCO-, -CONH-, -SO2NH-, -NHSO2-, -NHCONH- _, -COO-, -OCO-, and a _2,5 -pyrrolidinedione ring represented by the following formula (A2-1), and among these, -O-, -S-, -NH-, an amide bond (-NHCO-, -CONH-), or a urea bond (-NHCONH-) is preferred.

(In the formula, an asterisk * represents a bond. The same applies hereinafter.)

The monovalent organic group having a conductive functional group for ^A3 may be a monovalent group containing a chemical structure conventionally known as a structure that exhibits conductivity, and examples thereof include a monovalent group having an oligoaniline structure, a monovalent group having a triarylamine structure, a monovalent group having an N,N'-diarylbenzidine structure, a monovalent group having an N,N,N',N'-tetraarylbenzidine structure, a monovalent group having a carbazole structure, a monovalent group having an oligothiophene structure, a monovalent group having a thienothiophene structure, a monovalent group having a thienobenzothiophene structure, and a monovalent group having an oligopyrrole structure. Aryl groups having one or more of these conductive functional groups are preferred, with aryl groups having a triarylamine structure and aryl groups having a carbazole structure being more preferred, and aryl groups having a phenylcarbazole structure being even more preferred.

Specific examples of the monovalent organic group having the conductive functional group include, but are not limited to, those represented by the following formulae:
Among these, groups represented by formulae (A3-9) and (A3-10) are preferred.

(In the formula, the asterisk * and k have the same meanings as above, and ^A4 represents an arylene group.)

Particularly preferred are those in which the bonds are in the following positions:

(In the formula, the asterisk *, k, and ^A4 have the same meanings as above.)

In the above formulas, A ⁴ represents an arylene group, preferably an arylene group having 6 to 40 carbon atoms.
Specific examples of the arylene group include, but are not limited to, those represented by the following formulae:

(In the formula, the asterisk * has the same meaning as above.)

As arylene groups, those with the bonds at the following positions are particularly preferred.

(In the formula, the asterisk * has the same meaning as above.)

In particular, the silane coupling agent used in the present invention is preferably a compound represented by the following formula (S1-1), and more preferably a compound represented by the following formula (S1-1-1).

(In the formula, R represents an alkyl group having 1 to 5 carbon atoms, A ¹ represents an alkylene group having 2 to 5 carbon atoms, and A ⁴ represents an arylene group.)

(In the formula, R represents an alkyl group having 1 to 5 carbon atoms, A ¹ represents an alkylene group having 2 to 5 carbon atoms, and A ⁴ represents an arylene group.)

Specific examples of silane coupling agents include, but are not limited to, those represented by the following formula:

The above-mentioned silane coupling agent can be obtained by reacting a trialkoxysilane compound having a reactive group such as a halogen atom, NCO, _NH2 , SH, or 2,5-dioxotetrahydro-3-yl group at the end with an aryl compound having a functional group on the aryl group that reacts with these reactive groups ( _NH2 group, NCO group, carboxylic acid halide group, sulfonic acid halide group, etc.) using a known method for forming a divalent linking group such as amidation, urea conversion, or esterification.
Alternatively, it can also be obtained by subjecting a trialkoxysilane compound having an SH group at its terminal to a compound having a carbon-carbon double bond and a conductive functional group in a known ene-thiol reaction.
Furthermore, it can also be obtained by subjecting a trialkoxysilane compound having an Si—H group to a known hydrosilylation reaction with a compound having a carbon-carbon double bond and a conductive functional group.
Alternatively, it can be obtained by reacting a tetraalkoxysilane such as tetraethoxysilane with a compound having a halogen atom such as a chlorine atom or a bromine atom on an aryl group under known conditions.

Examples of the alkoxysilane compound used in the production of the silane coupling agent of the present invention include 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, glycidoxymethyltriethoxysilane, α-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxysilane, γ-glycidoxypropyl Examples of trialkoxysilanes include butyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, α-glycidoxybutyltriethoxysilane, β-glycidoxybutyltriethoxysilane, γ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, chloromethyltrimethoxysilane, chloromethyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, trimethoxysilane, and triethoxysilane.
These compounds may be commercially available products.

The primary particle diameter of the surface-treated metal oxide nanoparticles is not particularly limited, but is usually 5 nm or more, and is usually 200 nm or less, preferably 100 nm or less, and more preferably 30 nm or less, from the viewpoint of ensuring good particle dispersibility, ease of production, etc. This particle diameter is the particle diameter (median diameter _D50 ) at which the cumulative frequency distribution in volume-based particle size distribution measurement by dynamic light scattering method is 50%.

In the surface-treated metal oxide nanoparticles used in the present invention, the amount of silane coupling agent modification on the surface of the metal oxide nanoparticles is not particularly limited, but from the viewpoint of the dispersibility of the metal oxide nanoparticles and the transparency of the resulting thin film, it is preferably 0.1 particles/nm or more and less than 2.0 particles/ ^nm² , more preferably 0.2 to 1.9 particles/ ^nm² , and even more preferably 0.3 to 1.7 particles/ ^nm² .
The modification amount X (number of particles/ ^nm2 ) is calculated using the particle size (nm) of the metal oxide nanoparticles, the specific surface area SA ( ^nm2 /g) of each particle calculated from the specific gravity (g/ ^cm3 ), the total amount M (g) of metal oxide particles, the molecular weight Mw of the silane coupling agent, the amount Y (g) of the silane coupling agent, and Avogadro's constant L, as Y = X*SA*M*Mw/L.

The amount of metal oxide nanoparticles contained in the charge-transporting varnish of the present invention is not particularly limited, but from the viewpoint of improving the transparency of the resulting thin film and increasing the uniformity of the film, the lower limit of the solid content is typically 20% by mass, preferably 30% by mass, and more preferably 40% by mass, and the upper limit is typically 95% by mass, preferably 90% by mass.

The surface-treated metal oxide nanoparticles used in the present invention may also be used in the form of a sol dispersed in a dispersion medium.
Examples of the dispersion medium include water, methanol, methyl ethyl ketone, methyl isobutyl ketone, N,N-dimethylacetamide, ethylene glycol, isopropanol, methanol, ethylene glycol monopropyl ether, cyclohexanone, ethyl acetate, toluene, and propylene glycol monomethyl ether acetate.

The solid content concentration of the sol is not particularly limited, but is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and even more preferably 15 to 30% by mass.
The amount of sol used is appropriately determined taking into consideration the concentration so that the amount of surface-treated metal oxide nanoparticles finally contained in the varnish will be the blend amount of the metal oxide nanoparticles described above.

[2] Charge transporting substance The charge transporting substance is not particularly limited and can be appropriately selected from, for example, charge transporting compounds, charge transporting oligomers, charge transporting polymers, and the like used in the field of organic electroluminescence.
Specific examples thereof include various charge transporting compounds such as arylamine derivatives, such as oligoaniline derivatives, N,N'-diarylbenzidine derivatives, and N,N,N',N'-tetraarylbenzidine derivatives; thiophene derivatives, such as oligothiophene derivatives, thienothiophene derivatives, and thienobenzothiophene derivatives; and pyrrole derivatives, such as oligopyrrole; and charge transporting polymers, such as charge transporting oligomers, polythiophene derivatives, polyaniline derivatives, and polypyrrole derivatives. Of these, polythiophene derivatives and arylamine derivatives are preferred.

Furthermore, charge-transporting compounds (low-molecular-weight compounds) or charge-transporting oligomers, such as tertiary arylamine compounds represented by formula (A1) or (A2) described below, are preferably monodisperse (i.e., have a molecular weight distribution of 1) from the viewpoint of producing thin films with high flatness. In this case, the molecular weight of the charge-transporting substance is typically about 200 to 9,000 from the viewpoint of preparing a uniform ink that gives thin films with high flatness. However, from the viewpoint of obtaining thin films with even better charge transport properties, it is preferably 300 or more, and more preferably 400 or more. From the viewpoint of preparing a uniform ink that gives thin films with high flatness and good reproducibility, it is preferably 8,000 or less, more preferably 7,000 or less, even more preferably 6,000 or less, and even more preferably 5,000 or less.

Examples of charge transport materials include those described in JP 2002-151272 A, WO 2004/105446 A, WO 2005/043962 A, WO 2008/032617 A, WO 2008/032616 A, WO 2013/042623 A, WO 2014/141998 A, WO 2014/185208 A, Examples of such compounds include those disclosed in International Publication Nos. WO 2015/050253, WO 2015/137391, WO 2015/137395, WO 2015/146912, WO 2015/146965, WO 2016/190326, WO 2016/136544, and WO 2016/204079.

One preferred embodiment of the charge-transporting material is a tertiary arylamine compound that has at least one nitrogen atom, all of which have a tertiary arylamine structure. In other words, this tertiary arylamine compound has at least one nitrogen atom, and has a structure in which three aromatic groups are bonded to all of the nitrogen atoms. It is preferable that the tertiary arylamine compound have two or more nitrogen atoms.

Suitable examples of tertiary arylamine compounds include compounds represented by the following formula (A1) or (A2):

In formula (A2), R ¹ and R ² each independently represent a hydrogen atom, a halogen atom, a nitro group, or a cyano group, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a heteroaryl group having 2 to 20 carbon atoms, each of which may be substituted with a halogen atom.

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 specific examples thereof include linear or branched alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-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.

Alkenyl groups having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include vinyl, n-1-propenyl, n-2-propenyl, 1-methylvinyl, n-1-butenyl, n-2-butenyl, n-3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylvinyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, n-1-pentenyl, n-1-decenyl, and n-1-eicosenyl groups.

Alkynyl groups having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include ethynyl, n-1-propynyl, n-2-propynyl, n-1-butynyl, n-2-butynyl, n-3-butynyl, 1-methyl-2-propynyl, n-1-pentynyl, n-2-pentynyl, n-3-pentynyl, n-4-pentynyl, 1-methyl-n-butynyl, 2-methyl-n-butynyl, 3-methyl-n-butynyl, 1,1-dimethyl-n-propynyl, n-1-hexynyl, n-1-decynyl, n-1-pentadecinyl, and n-1-eicosynyl groups.

Examples of the aryl group 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.
Examples of heteroaryl groups having 2 to 20 carbon atoms include 2-thienyl, 3-thienyl, 2-furanyl, 3-furanyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 3-isothiazolyl, 4-isothiazolyl, 5-isothiazolyl, 2-imidazolyl, 4-imidazolyl, 2-pyridyl, 3-pyridyl, and 4-pyridyl groups.

Of these, R ¹ and R ² are preferably a hydrogen atom, a fluorine atom, a cyano group, an alkyl group of 1 to 20 carbon atoms which may be substituted with a halogen atom, an aryl group of 6 to 20 carbon atoms which may be substituted with a halogen atom, or a heteroaryl group of 2 to 20 carbon atoms which may be substituted with a halogen atom, more preferably a hydrogen atom, a fluorine atom, a cyano group, an alkyl group of 1 to 10 carbon atoms which may be substituted with a halogen atom, or a phenyl group which may be substituted with a halogen atom, still more preferably a hydrogen atom or a fluorine atom, and most preferably a hydrogen atom.

In formulae (A1) and (A2), Ph ¹ is a group represented by formula (P1).

In formula (P1), the dashed lines represent bonds. ^R3 to ^R6 each independently represent a hydrogen atom, a halogen atom, a nitro group, or a cyano group, or an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a heteroaryl group having 2 to 20 carbon atoms, each of which may be substituted with a halogen atom. Specific examples of these groups include those described in the description of ^R1 and ^R2 .

In particular, ^R3 to ^R6 are preferably a hydrogen atom, a fluorine atom, a cyano group, an alkyl group of 1 to 20 carbon atoms which may be substituted with a halogen atom, an aryl group of 6 to 20 carbon atoms which may be substituted with a halogen atom, or a heteroaryl group of 2 to 20 carbon atoms which may be substituted with a halogen atom, more preferably a hydrogen atom, a fluorine atom, a cyano group, an alkyl group of 1 to 10 carbon atoms which may be substituted with a halogen atom, or a phenyl group which may be substituted with a halogen atom, still more preferably a hydrogen atom or a fluorine atom, and most preferably a hydrogen atom.

Suitable groups for Ph ¹ include, but are not limited to, 1,4-phenylene groups.

In formula (A1), Ar ¹ is each independently a group represented by any one of the following formulae (Ar1-1) to (Ar1-11), and is particularly preferably a group represented by any one of the following formulae (Ar1-1') to (Ar1-11').

In formulae (Ar1-1) to (Ar1-11) and formulae (Ar1-1') to (Ar1-11'), dashed lines represent bonds. ^{R 7} to R ²⁷ , R ³⁰ to R ⁵¹ and R ⁵³ to R ¹⁵⁴ each independently represent a hydrogen atom, a halogen atom, a nitro group, or a cyano group, or a diphenylamino group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a heteroaryl group having 2 to 20 carbon atoms, each optionally substituted with a halogen atom. ^{R 28} and R ²⁹ each independently represent an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms, each optionally substituted with Z ¹ . R ⁵² is an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms, which may be substituted with Z ¹ .

^Z1 is a halogen atom, a nitro group or a cyano group, or an alkyl group having 1 to ²⁰ carbon atoms, an alkenyl group having 2 to 20 carbon atoms or an alkynyl group having 2 to 20 carbon atoms, which may be substituted with Z2. ^Z2 is a halogen atom, a nitro group or a cyano group, or an aryl group having 6 to 20 carbon atoms or a heteroaryl group having 2 to 20 carbon atoms, which may be substituted with ^Z3 . ^Z3 is a halogen atom, a nitro group or a cyano group.

In particular, R ⁷ to R ²⁷ , R ³⁰ to R ⁵¹ and R ⁵³ to R ¹⁵⁴ are preferably a hydrogen atom, a fluorine atom, a cyano group, a diphenylamino group which may be substituted with a halogen atom, an alkyl group of 1 to 20 carbon atoms which may be substituted with a halogen atom, an aryl group of 6 to 20 carbon atoms which may be substituted with a halogen atom, or a heteroaryl group of 2 to 20 carbon atoms which may be substituted with a halogen atom, more preferably a hydrogen atom, a fluorine atom, a cyano group, an alkyl group of 1 to 10 carbon atoms which may be substituted with a halogen atom, or a phenyl group which may be substituted with a halogen atom, still more preferably a hydrogen atom or a fluorine atom, and most preferably a hydrogen atom.

R ²⁸ and R ²⁹ are preferably an aryl group having 6 to 14 carbon atoms which may be substituted with a halogen atom, or a heteroaryl group having 2 to 14 carbon atoms which may be substituted with a halogen atom, more preferably a phenyl group which may be substituted with a halogen atom, or a naphthyl group which may be substituted with a halogen atom, still more preferably a phenyl group which may be substituted with a halogen atom, and even more preferably a phenyl group.

^R52 is preferably a hydrogen atom or an aryl group having 6 to 20 carbon atoms which may be substituted with ^Z1 , more preferably a hydrogen atom, a phenyl group which may be substituted with ^Z1 , or a naphthyl group which may be substituted with ^Z1 , still more preferably a phenyl group which may be substituted with ^Z1 , and even more preferably a phenyl group.

In formulas (Ar1-10), (Ar1-11), (Ar1-10'), and (Ar1-11'), Ar ⁴ 's each independently represent an aryl group having 6 to 20 carbon atoms which may be substituted with a diarylamino group, each aryl group being an aryl group having 6 to 20 carbon atoms. Specific examples of the aryl group having 6 to 20 carbon atoms include those described above for R ^1' and R ^2' . Specific examples of the diarylamino group include a diphenylamino group, a 1-naphthylphenylamino group, a di(1-naphthyl)amino group, a 1-naphthyl-2-naphthylamino group, and a di(2-naphthyl)amino group.

^Ar4 is preferably phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9-phenanthryl, p-(diphenylamino)phenyl, p-(1-naphthylphenylamino)phenyl, p-(di(1-naphthyl)amino)phenyl group, p-(1-naphthyl-2-naphthylamino)phenyl, p-[di(2-naphthyl)amino]phenyl group, or the like, more preferably p-(diphenylamino)phenyl group.

In formula (A1), Ar ² 's are each independently a group represented by any one of formulas (Ar2-1) to (Ar2-18), and are particularly preferably a group represented by any one of formulas (Ar2-1'-1) to (Ar2-18'-2). In the following formula, Ar ⁴ has the same meaning as above, DPA is a diphenylamino group, and the dashed lines represent bonds.

In formulae (Ar2-16), (Ar2-16'-1) and (Ar2-16'-2), R ¹⁵⁵ is a hydrogen atom, an aryl group having 6 to 14 carbon atoms which may be substituted with Z ¹ , or a heteroaryl group having 2 to 14 carbon atoms which may be substituted with Z ^1. Examples of the aryl group and heteroaryl group include those similar to those described in the description of R ^1' and R ^2' . Of these, R ¹⁵⁵ is preferably a hydrogen atom, a phenyl group which may be substituted with Z ¹ , a 1-naphthyl group which may be substituted with Z ¹ , a 2-naphthyl group which may be substituted with Z ¹ , a 2-pyridyl group which may be substituted with Z ¹ , a 3-pyridyl group which may be substituted with a phenyl group which may be substituted with Z ¹ , or a 4-pyridyl group which may be substituted with Z ¹ , more preferably a phenyl group which may be substituted with Z ¹ , and even more preferably a phenyl group or a (2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl) group.

In formulae (Ar2-17), (Ar2-17'-1), and (Ar2-17'-2), R ¹⁵⁶ and R ¹⁵⁷ are an aryl group having 6 to 14 carbon atoms which may be substituted with a phenyl group which may be substituted with Z ¹ , or a heteroaryl group having 2 to 14 carbon atoms which may be substituted with a phenyl group which may be substituted with Z ^1. Examples of these aryl groups and heteroaryl groups include those similar to those described in the description of R ^1' and R ^2' . Of these, R ¹⁵⁶ and R ¹⁵⁷ are preferably an aryl group having 6 to 14 carbon atoms which may be substituted with a phenyl ^group which may be substituted with Z ¹ , and more preferably a phenyl group which may be substituted with a phenyl group which may be substituted with Z ¹ , a 1-naphthyl group which may be substituted with a phenyl group which may be substituted with Z 1, or a 2-naphthyl group which may be substituted with Z ¹ .

In formula (A2), Ar ³ is a group represented by any one of formulas (Ar3-1) to (Ar3-8), and is particularly preferably a group represented by any one of formulas (Ar3-1') to (Ar3-8'). In the following formula, DPA has the same meaning as above, and the dashed line represents a bond.

In formula (A1), p is an integer between 1 and 10, but from the viewpoint of increasing the solubility of the compound in organic solvents, it is preferably between 1 and 5, more preferably between 1 and 3, even more preferably 1 or 2, and optimally 1. In formula (A2), q is 1 or 2.

The aniline derivatives represented by formula (A1) and formula (A2) can be prepared, for example, according to the method described in WO 2015/050253.

The tertiary arylamine compound is not limited to the compounds described above, as long as it has at least one nitrogen atom and all of the nitrogen atoms have a tertiary arylamine structure. Other tertiary arylamine compounds that can be used in the present invention include, for example, the arylamine compounds described in WO 2005/094133, the polymerizable compound having a triarylamine partial structure and a polymerizable group described in Japanese Patent No. 5287455, the triarylamine compounds described in Japanese Patent No. 5602191, and the compounds described in paragraph [0054] of Japanese Patent No. 6177771.

Preferred examples of the above-mentioned tertiary arylamine compounds include, but are not limited to, the following:

[3] Dopant substance The dopant substance is not particularly limited as long as it dissolves in at least one solvent used in the charge transport 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.
The amount of the dopant substance cannot be generally specified because it is determined appropriately taking into consideration the type of dopant substance, the desired degree of charge transportability, etc., but is usually within the range of 0.0001 to 100.0 parts by mass per 1 part of the charge transport substance.

The inorganic dopant substance used in the present invention is preferably a heteropolyacid.
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 condensation of 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, and phosphotungstomolybdic acid, 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 most preferably phosphotungstic acid.
In addition, the heteropolyacid may be used in the present invention regardless of whether it has a large or small number of elements in the structure represented by the general formula 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 quantitative analysis shows that compounds having a high or low number of P (phosphorus), O (oxygen), W (tungsten), or Mo (molybdenum) in these formulas 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 refer to the mass of pure phosphotungstic acid (phosphotungstic acid content) in a synthesized or commercially available product, but rather refers to the total mass, including water of hydration and other impurities, in a commercially available form or in a form that can be isolated by a known synthesis method.

The amount of heteropolyacid used can be approximately 0.001 to 50.0 parts by mass of charge-transporting substance such as polythiophene derivatives or arylamine derivatives per 1 part, but is preferably approximately 0.01 to 20.0 parts, and more preferably approximately 0.1 to 10.0 parts.

On the other hand, as organic dopant substances, tetracyanoquinodimethane derivatives and benzoquinone derivatives can be used.
Specific examples of the tetracyanoquinodimethane derivative include 7,7,8,8-tetracyanoquinodimethane (TCNQ) and halotetracyanoquinodimethane represented by formula (H3).
Specific examples of the benzoquinone derivative include 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetrachloro-1,4-benzoquinone (chloranil), trifluoro-1,4-benzoquinone, tetrafluoro-1,4-benzoquinone, tetrabromo-1,4-benzoquinone, tetracyano-1,4-benzoquinone, etc. Of these, 2,3-dichloro-5,6-dicyano-p-benzoquinone, trifluorobenzoquinone, tetrafluorobenzoquinone, and tetracyanobenzoquinone are preferred, DDQ, chloranil, tetrafluoro-1,4-benzoquinone, and tetracyano-1,4-benzoquinone are more preferred, and DDQ is even more preferred.

In the formula, R ⁵⁰⁰ to R ⁵⁰³ each independently represent a hydrogen atom or a halogen atom, and at least one is a halogen atom, preferably at least two are halogen atoms, more preferably at least three are halogen atoms, and most preferably all 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, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane, tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), tetrachloro-7,7,8,8-tetracyanoquinodimethane, 2-fluoro-7,7,8,8-tetracyanoquinodimethane, 2-chloro-7,7,8,8-tetracyanoquinodimethane, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane, and 2,5-dichloro-7,7,8,8-tetracyanoquinodimethane, with F4TCNQ being preferred.

The amount of tetracyanoquinodimethane derivatives and benzoquinone derivatives 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 organic functional material such as a polythiophene derivative or an arylamine derivative.

Furthermore, an arylsulfonic acid compound can also be used as the organic dopant material.
Specific examples of the arylsulfonic acid compound 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-octyl-1- ... Examples of the arylsulfonic acid include 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, the 1,4-benzodioxanedisulfonic acid compounds described in WO 2005/000832, the arylsulfonic acid compounds described in WO 2006/025342, and the arylsulfonic acid compounds described in WO 2009/096352.

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

D ¹ represents O or S, with O being preferred.
^D2 represents a naphthalene ring or an anthracene ring, with a naphthalene ring being preferred.
^D3 represents a divalent to tetravalent perfluorobiphenyl group, s represents the number of bonds between ^D1 and ^D3 and is an integer satisfying 2≦s≦4, but it is preferred that ^D3 is a perfluorobiphenyldiyl group, preferably a perfluorobiphenyl-4,4′-diyl group, and s is 2.
t represents the number of sulfonic acid groups bonded to ^D2 and is an integer satisfying 1≦t≦4, with 2 being optimal.

^D4 to ^D8 each independently represent a hydrogen atom, a halogen atom, a cyano group, a nitro 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 ^D4 to ^D8 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 (perfluoroallyl), 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, but the halogen atom is preferably a fluorine atom.

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

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

Specific examples of suitable aryl sulfonic acid compounds are listed 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, in terms of mole ratio per 1 part of the organic functional material such as a polythiophene derivative or an arylamine derivative.
The arylsulfonic acid compound may be a commercially available product, but can also be synthesized by known methods described in WO 2006/025342, WO 2009/096352, and the like.

The dopant substance may also be a substance whose function as a dopant substance is first manifested or improved when a part of the molecule is removed by an external stimulus, such as heating during baking, during the process of obtaining a charge-transporting thin film, which is a solid film, from the varnish, for example, an arylsulfonic acid ester compound protected by a group that easily removes the sulfonic acid group.

The aryl sulfonate ester compound is not particularly limited as long as it has a sulfonate ester group bonded to an aromatic ring. In a preferred embodiment of the present invention, the molecular weight of the aryl sulfonate ester compound is preferably 100 or more, more preferably 200 or more, and preferably 5,000 or less, more preferably 4,000 or less, even more preferably 3,000 or less, and even more preferably 2,000 or less. In a preferred embodiment of the present invention, the number of sulfonate ester groups in the aryl sulfonate ester compound is preferably 2 or more, more preferably 3 or more, and preferably 6 or less, more preferably 5 or less. In a preferred embodiment of the present invention, the aryl sulfonate ester compound preferably contains an aromatic ring substituted with fluorine.

Examples of the aryl sulfonate ester compound include the aryl sulfonate ester compounds disclosed in WO 2017/217455, the aryl sulfonate ester compounds disclosed in WO 2017/217457, and the aryl sulfonate ester compounds described in WO 2019/124412.
The arylsulfonic acid ester compound is preferably one represented by the following formula (B1) or (B1').

In formulas (B1) and (B1'), A ⁰¹ is an m-valent hydrocarbon group having 6 to 20 carbon atoms and containing one or more aromatic rings, which may have a substituent, or an m-valent group derived from a compound represented by formula (B1a) or (B1b) below (i.e., a group obtained by removing m hydrogen atoms on the aromatic rings of a compound represented by formula (B1a) or (B1b) below).

(In the formula, W ¹ and W ² each independently represent —O—, —S—, —S(O)—, —S(O ₂ )—, or —N—, —Si—, —P—, or —P(O)— which may have a substituent.)

An m-valent hydrocarbon group having 6 to 20 carbon atoms and containing one or more aromatic rings is a group obtained by removing m hydrogen atoms from a hydrocarbon having 6 to 20 carbon atoms and containing one or more aromatic rings. Examples of hydrocarbons containing one or more aromatic rings include benzene, toluene, xylene, biphenyl, naphthalene, anthracene, and pyrene. Of these, groups derived from benzene, biphenyl, etc. are preferred as m-valent hydrocarbon groups.

The above hydrocarbon groups may further have some or all of their hydrogen atoms substituted with a substituent. Examples of such substituents include halogen atoms (fluorine, chlorine, bromine, and iodine), nitro, cyano, hydroxy, amino, silanol, thiol, carboxy, sulfonate esters, phosphoric acid, phosphate esters, esters, thioesters, amides, monovalent hydrocarbons, organooxy, organoamino, organosilyl, organothio, acyl, and sulfo groups.

Here, the monovalent hydrocarbon group may be linear, branched, or cyclic. Specific examples include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; alkenyl groups having 2 to 10 carbon atoms, such as vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-methyl-2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, and hexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, xylyl, tolyl, 1-naphthyl, and 2-naphthyl; and aralkyl groups having 7 to 20 carbon atoms, such as benzyl and phenylethyl.

Specific examples of the organoxy group include alkoxy, alkenyloxy, and aryloxy groups. The alkyl, alkenyl, and aryl groups contained therein are the same as those described above.

Specific examples of the organoamino group include alkylamino groups having 1 to 12 carbon atoms, such as methylamino, ethylamino, propylamino, butylamino, pentylamino, hexylamino, cyclohexylamino, heptylamino, octylamino, nonylamino, decylamino, and dodecylamino; dialkylamino groups in which the alkyl group has 1 to 12 carbon atoms, such as dimethylamino, diethylamino, dipropylamino, dibutylamino, dipentylamino, dihexylamino, dicyclohexylamino, diheptylamino, dioctylamino, dinonylamino, and didecylamino; and morpholino groups.

Specific examples of the organosilyl group include trialkylsilyl groups, each of which is an alkyl group having 1 to 10 carbon atoms, such as trimethylsilyl, triethylsilyl, tripropylsilyl, tributylsilyl, tripentylsilyl, trihexylsilyl, pentyldimethylsilyl, hexyldimethylsilyl, octyldimethylsilyl, and decyldimethylsilyl groups.
Specific examples of the organothio group include alkylthio groups having 1 to 12 carbon atoms, such as methylthio, ethylthio, propylthio, butylthio, pentylthio, hexylthio, heptylthio, octylthio, nonylthio, decylthio, and dodecylthio groups.
Examples of the acyl group include acyl groups having 1 to 10 carbon atoms, such as formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, and benzoyl groups.

The carbon number of these monovalent hydrocarbon groups, organooxy groups, organoamino groups, organosilyl groups, organothio groups, and acyl groups is preferably 1 to 8.

Of these substituents, fluorine atoms, sulfonic acid groups, alkyl groups, organooxy groups, and organosilyl groups are more preferred.

In formula (B1), A ⁰² is —O—, —S— or —NH—, and among these, —O— is preferred because of ease of synthesis.

In formula (B1), A ⁰³ is an (n+1)-valent aromatic group having 6 to 20 carbon atoms. The (n+1)-valent aromatic group is a group obtained by removing (n+1) hydrogen atoms on the aromatic ring of an aromatic compound having 6 to 20 carbon atoms. In the present invention, the aromatic compound means an aromatic hydrocarbon or an aromatic heterocyclic compound.
Examples of the aromatic compound include benzene, toluene, xylene, biphenyl, naphthalene, anthracene, and pyrene. Of these, the aromatic group represented by ^A3 is preferably a group derived from naphthalene or anthracene.

In formulas (B1) and (B1'), ^X1 is an alkylene group having 2 to 5 carbon atoms, and this alkylene group may have —O—, —S— or a carbonyl group interposed between its carbon atoms (carbon-carbon bonds), and some or all of its hydrogen atoms may be further substituted with alkyl groups having 1 to 20 carbon atoms.
^X1 is preferably an ethylene, trimethylene, methyleneoxymethylene, or methylenethiomethylene group, and some or all of the hydrogen atoms in these groups may be further substituted with an alkyl group having 1 to 20 carbon atoms. Examples of this alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, and bicyclohexyl groups.

In formulas (B1) and (B1'), ^X2 is a single bond, —O—, —S—, or NR—. R is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. This monovalent hydrocarbon group is preferably an alkyl group such as methyl, ethyl, or n-propyl.
^X2 is preferably a single bond, —O— or —S—, more preferably a single bond or —O—.

In formulas (B1) and (B1'), ^X3 represents a monovalent hydrocarbon group having 1 to 20 carbon atoms which may be substituted. This monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 20 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, and bicyclohexyl groups; vinyl, 1-propenyl, 2-propenyl, isopropenyl, 1-methyl-2-propenyl, and 1-butene. Examples of suitable substituents include alkenyl groups having 2 to 20 carbon atoms, such as phenyl, 2-butenyl, 3-butenyl, and hexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, xylyl, tolyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9-phenanthryl, 2-biphenylyl, 3-biphenylyl, and 4-biphenylyl; and aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenylethyl, and phenylcyclohexyl. Some or all of the hydrogen atoms in the monovalent hydrocarbon group may be further substituted with a substituent. Examples of such substituents include those similar to those described in the description of A ^{01. X 3} is preferably an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms.

In formulas (B1) and (B1'), m is an integer satisfying 1≦m≦4, preferably 2. n is an integer satisfying 1≦n≦4, preferably 2.

The arylsulfonate ester compounds represented by formulas (B1) and (B1') exhibit high solubility in a wide range of solvents, including low-polarity solvents, making it possible to tailor the physical properties of the solution using a wide variety of solvents, resulting in excellent coating properties. Therefore, it is preferable to apply the compound in the form of a sulfonate ester and generate sulfonic acid when the coating film is dried or baked. The temperature at which sulfonic acid is generated from the sulfonate ester is stable at room temperature and preferably below the baking temperature, so a temperature between 40 and 260°C is preferred. Furthermore, considering high stability in the varnish and ease of desorption during baking, a temperature between 80 and 230°C is preferred, with 120 and 180°C being even more preferred.

The aryl sulfonate ester compound represented by formula (B1) is preferably one represented by any of the following formulas (B1-1) to (B1-3).

In formula (B1-1), A ¹¹ is an m-valent group derived from perfluorobiphenyl (i.e., a group obtained by removing m fluorine atoms 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 (i.e., a group obtained by removing (n+1) hydrogen atoms from naphthalene or anthracene), with a group derived from naphthalene being preferred.

In formula (B1-1), R ^s1 to R ^s4 each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ^s5 represents 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, sec-butyl, tert-butyl, and n-hexyl groups. Of these, alkyl groups having 1 to 3 carbon atoms are preferred.

The monovalent hydrocarbon group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include alkyl groups such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; and aryl groups such as phenyl, naphthyl, and phenanthryl.

Of R ^s1 to R ^s4 , it is preferable that R ^s1 or R ^s3 is a linear alkyl group having 1 to 3 carbon atoms, and the remainder are hydrogen atoms. Furthermore, it is preferable that R ^s1 is a linear alkyl group having 1 to 3 carbon atoms, and R ^s2 to R ^s4 are hydrogen atoms. As the linear alkyl group having 1 to 3 carbon atoms, a methyl group is preferable. Furthermore, R ^s5 is preferably a linear alkyl group having 2 to 4 carbon atoms or a phenyl group.

In formula (B1-1), m is an integer that satisfies 1≦m≦4, preferably 2. n is an integer that satisfies 1≦n≦4, preferably 2.

In formula (B1-2), A ¹⁴ is an m-valent hydrocarbon group having 6 to 20 carbon atoms and containing one or more aromatic rings, which may be substituted. The m-valent hydrocarbon group is a group obtained by removing m hydrogen atoms from a hydrocarbon having 6 to 20 carbon atoms and containing one or more aromatic rings. Examples of the hydrocarbon include benzene, toluene, xylene, ethylbenzene, biphenyl, naphthalene, anthracene, and phenanthrene.

In addition, some or all of the hydrogen atoms in the hydrocarbon group may be further substituted with a substituent, and such substituents include halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom), nitro, cyano, hydroxy, amino, silanol, thiol, carboxy, sulfonate ester, phosphoric acid, phosphate ester, ester, thioester, amide, monovalent hydrocarbon, organooxy, organoamino, organosilyl, organothio, acyl, sulfo group, etc. Among these, groups derived from benzene, biphenyl, etc. are preferred as ^A14 .

In formula (B1-2), A ¹⁵ is —O— or —S—, with —O— being preferred.

In formula (B1-2), A ¹⁶ is an (n+1)-valent aromatic hydrocarbon group having 6 to 20 carbon atoms. The (n+1)-valent aromatic hydrocarbon group 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 this aromatic hydrocarbon compound include benzene, toluene, xylene, biphenyl, naphthalene, anthracene, and pyrene. Of these, A ¹⁶ is preferably a group derived from naphthalene or anthracene, and more preferably a group derived from naphthalene.

In formula (B1-2), R ^s6 and R ^s7 each independently represent a hydrogen atom or a linear or branched monovalent aliphatic hydrocarbon group. R ^s8 represents a linear or branched monovalent aliphatic hydrocarbon group. 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, and more preferably 10 or less.

Specific examples of the above-mentioned linear or branched monovalent aliphatic hydrocarbon groups include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-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.

R ^s6 is preferably a hydrogen atom, and R ^s7 and R ^s8 are preferably alkyl groups having 1 to 6 carbon atoms. In this case, R ^s7 and R ^s8 may be the same or different.

In formula (B1-2), m is an integer satisfying 1≦m≦4, preferably 2. n is an integer satisfying 1≦n≦4, preferably 2.

In formula (B1-3), 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 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-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 an alkyl group having 1 to 10 carbon atoms have been substituted with halogen atoms. The halogenated alkyl group may be linear, branched, or cyclic, 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.

The halogenated alkenyl group having 2 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 an alkenyl group having 2 to 10 carbon atoms have been substituted with halogen atoms. Specific examples include perfluorovinyl, perfluoro-1-propenyl, perfluoro-2-propenyl, perfluoro-1-butenyl, perfluoro-2-butenyl, and perfluoro-3-butenyl groups.

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

In formula (B1-3), A ¹⁷ is —O—, —S— or —NH—, with —O— being preferred.

In formula (B1-3), A ¹⁸ is an (n+1)-valent aromatic hydrocarbon group having 6 to 20 carbon atoms. The (n+1)-valent aromatic hydrocarbon group 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 the aromatic hydrocarbon compound include benzene, toluene, xylene, biphenyl, naphthalene, anthracene, and pyrene. Of these, A ¹⁸ is preferably a group derived from naphthalene or anthracene, and more preferably a group derived from naphthalene.

In formula (B1-3), 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. The monovalent aliphatic hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, cyclopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl; 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. 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.

In formula (B1-3), 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 represented by R ^s18 include those similar to those described in the description of R ^s14 to R ^s17 . 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 represented by R ^s19 include the monovalent aliphatic hydrocarbon groups described above other than methyl, as well as aryl groups such as phenyl, naphthyl, and phenanthryl. Of 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.

In formula (B1-3), n is an integer satisfying the condition 1≦n≦4, with 2 being preferred.

As the aryl sulfonate ester compound represented by formula (B1-3), those represented by the following formula (B1-3-1) or (B1-3-2) are particularly preferred.

In formulas (B1-3-1) and (B1-3-2), A ¹⁷ , A ¹⁸ , R ^s9 to R ^s17 , R ^s19 and n are as defined above. R ^s20 is a linear or branched monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, and specific examples thereof include those similar to those described in the description of R ^s18 .

In the arylsulfonate ester compound represented by formula (B1-3-1), among R ^s14 to R ^s17 , it is preferable that R ^s14 or R ^s16 is a linear alkyl group having 1 to 3 carbon atoms, and the remainder are hydrogen atoms. Furthermore, it is preferable that R ^s14 is a linear alkyl group having 1 to 3 carbon atoms, and R ^s15 to R ^s17 are hydrogen atoms. As this linear alkyl group having 1 to 3 carbon atoms, a methyl group is preferred. Furthermore, R ^s19 is preferably a linear alkyl group having 2 to 4 carbon atoms or a phenyl group.

In the arylsulfonate compound represented by formula (B1-3-2), the total number of carbon atoms in R ^s14 , R ^s16 , and R ^s20 is preferably 6 or more. The upper limit of the total number of carbon atoms in ^{R s14} , R ^s16 , and R ^s20 is preferably 20 or less, and more preferably 10 or less. In this case, ^{R s14 is} preferably a hydrogen atom, and R s16 and R ^s20 are preferably an alkyl group having 1 to 6 carbon atoms. Furthermore, R ^s16 and R ^s20 may be the same or different.

The aryl sulfonate ester compounds represented by formula (B1) may be used alone or in combination of two or more.

Specific examples of suitable aryl sulfonate ester compounds include, but are not limited to, the following:

The amount of aryl sulfonate ester compound used is preferably approximately 0.01 to 20.0, more preferably approximately 0.05 to 15, in terms of molar ratio, per 1 part of organic functional material such as a polythiophene derivative or an arylamine derivative.

The molecular weight of organic dopants such as arylsulfonic acid compounds and arylsulfonic acid ester compounds is not particularly limited, but taking into consideration solubility in organic solvents when used together with a charge transport material, it is preferably 4,000 or less, more preferably 3,000 or less, and even more preferably 2,000 or less.

In the present invention, in order to produce a charge-transporting thin film with 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 the dopant substance, and in consideration of solubility in solvents, etc., it is more preferable to use an aryl sulfonic acid ester compound.

[4] Solvent The solvent used in preparing the charge-transporting varnish of the present invention may be a highly polar solvent capable of dissolving the charge-transporting material used. If necessary, a low-polarity solvent may be used because it has better process compatibility than a high-polarity solvent. In the present invention, a low-polarity solvent is defined as one having a dielectric constant of less than 7 at a frequency of 100 kHz, and a high-polarity solvent is defined as one having a 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 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.

Furthermore, 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 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 include sulfoxide solvents such as dimethyl sulfoxide.

[5] Silane Compound 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 purposes of improving injection into the hole transport layer, improving the life characteristics of the device, etc. The content of the organosilane compound is usually about 1 to 30% by mass based on the total mass of the charge transport substance and the dopant substance.

[6] Charge-Transporting Varnish and Charge-Transporting Thin Film 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 refers to the components other than the solvent contained in the charge-transporting varnish.
The solids concentration of the charge-transporting varnish is determined appropriately 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 %.

There are no particular limitations on the method for preparing the charge-transporting varnish. Examples include dissolving the charge-transporting substance and dopant substance in a high-polarity solvent, and then adding a low-polarity solvent and surface-treated metal oxide nanoparticles, or mixing a high-polarity solvent and a low-polarity solvent, dissolving the charge-transporting substance and dopant substance in the mixture, and then adding surface-treated metal oxide nanoparticles.

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

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; a uniform film surface and a thin film with 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 determined 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, the baking temperature is preferably about 140 to 250°C, and more preferably about 145 to 240°C. However, when the above-mentioned arylamine compound 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, and heating may be carried out using an appropriate device such as a hot plate or an oven.

There are no particular limitations on the film thickness of the charge-transporting thin film, but when used as a functional layer between the anode and light-emitting layer of an organic EL device, such as a hole injection layer, hole transport layer, or hole injection transport layer, a thickness of 5 to 300 nm is preferred. Methods for changing the film thickness include changing the solids concentration in the varnish or changing the amount of solution on the substrate during application.

The charge transport thin film of the present invention described above exhibits an average transmittance of 90% or more in the wavelength range of 400 to 800 nm at a film thickness of 50 nm, and in some embodiments exhibits an average transmittance of 92% or more, and in other embodiments exhibits an average transmittance of 95% or more.

[7] Organic EL Device When the charge transporting thin film is applied to an organic EL device, the organic EL device may be configured to include the charge transporting thin film between a pair of electrodes.
Representative configurations of organic EL elements 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, as necessary. Furthermore, the hole injection layer, the hole transport layer, or the hole injection transport layer may also function as an electron blocking layer or the like, and the electron injection layer, the electron transport layer, or the electron injection transport layer may also function as a hole blocking layer or the like. Furthermore, an arbitrary functional layer can be provided between each layer as 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 terms "hole injection layer,""hole transport layer," and "hole injection transport layer" refer to layers formed between the light-emitting layer and the anode, which have the function of transporting holes from the anode to the light-emitting layer. When only one layer of a hole-transporting 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-transporting material are provided between the light-emitting layer and the anode, the layer closest to the anode is the "hole injection layer," and the remaining layers are "hole transport layers." In particular, the hole injection (transport) layer is a thin film 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 layers formed between a light-emitting layer and a cathode, which have 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 that has a light-emitting function, and when a doping system is used, it contains a host material and a dopant material. In this case, the host material mainly functions to promote the recombination of electrons and holes and confine excitons within the light-emitting layer, while the dopant material functions to efficiently emit light from the excitons obtained by the recombination. In the case of a phosphorescent element, the host material mainly functions to confine excitons generated by the dopant within the light-emitting layer.

The charge transport thin film of the present invention can be used as a functional layer disposed between the anode and the light-emitting layer in an organic EL element, but is suitable as a hole injection layer, hole transport layer, or hole injection transport layer, more suitable as a hole injection layer or hole transport layer, and 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 device having a hole injection layer made of a thin film obtained from the charge-transporting varnish of the present invention is as follows: It is preferable to previously perform a surface treatment on the electrodes, such as washing with alcohol, pure water, or the like, or UV ozone treatment, oxygen-plasma treatment, or the like, 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-described method. This is then 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 preferably 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 that may be used to form the metal anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.

Materials for forming 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 with a polymer compound such as poly(p-phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly(3-alkylthiophene), or polyvinylcarbazole.
Furthermore, when forming the 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 fused 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, and aluminum-lithium alloy.
Examples of materials for forming the electron blocking layer include, but are not limited to, tris(phenylpyrazole)iridium.

Examples of hole-transporting 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]-end-capped with Examples include polysilcisquinoxane and 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 hole injection layers, hole transport layers, and hole injection transport layers that are disposed between the anode and light-emitting layer of organic EL devices. It can also be used to form charge transport thin films in electronic devices such as organic photoelectric conversion devices, organic thin-film solar cells, organic perovskite photoelectric conversion devices, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic optical inspectors, organic photoreceptors, organic field quenching devices, light-emitting electrochemical cells, quantum dot light-emitting diodes, quantum lasers, organic laser diodes, and organic plasmon light-emitting devices.

The present invention will be described in more detail below with reference to Production Examples, Preparation Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples. The apparatuses used are as follows.
(1) Substrate cleaning: Substrate cleaning equipment (low-pressure plasma method) manufactured by Choshu Sangyo Co., Ltd.
(2) Varnish application: Spin coater MS-A100 manufactured by Mikasa Co., Ltd.
(3) Film thickness measurement: Micro-shape measuring instrument Surfcorder ET-4000 manufactured by Kosaka Laboratory Co., Ltd.
(4) Fabrication of hole-only element: Multifunctional deposition system C-E2L1G1-N manufactured by Choshu Sangyo Co., Ltd.
(5) Measurement of current density of hole-only element: Multi-channel IVL measurement device manufactured by EHC Corporation (6) Measurement of transmittance: Ultraviolet-visible-near-infrared spectrophotometer UV-3600 manufactured by Shimadzu Science Corporation

[1] Production of a silane coupling agent having a conductive functional group [Production Example 1] Production of silane coupling agent (Si1)

Brominated compound 1 (7.71 g, 15.00 mmol, manufactured by Yurui (Shanghai) Chemical Co., Ltd.), Pd(dba) ₍ 863.0 mg, 5 mol%, manufactured by Tokyo Chemical Industry Co., Ltd.), ( _tBu3P ) _3HBF (435.0 _mg , 5 mol%, manufactured by Kanto Chemical Co., Inc.), toluene (120 mL), and _{a 1} M toluene solution of LiN( _SiMe3 ) (33 mL, 33 mmol, manufactured by Aldrich) were placed in a 300 mL flask and stirred at room temperature for 20 hours. The mixture was then cooled to 0°C, and 1 M aqueous HCl (66 mL, 66 mmol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred for 1.5 hours. 1 N aqueous NaOH was then added until the pH of the reaction solution was greater than 7. The mixture was then separated, the aqueous layer was removed, and the organic layer was washed with saturated brine. Toluene was removed from the resulting organic layer under reduced pressure, and 30 mL of toluene was added to dissolve the resulting solid, followed by the addition of 200 mL of hexane. The resulting solid was filtered and dried to obtain 4.86 g (72% yield) of amine 2.

Amine 2 (2.80 g, 6.23 mmol), THF (130 mL), and silane compound 3 (6.66 g, 26.91 mmol) were added to a 300 mL flask and stirred at 60°C for 19 hours. The mixture was cooled to room temperature, and the THF was removed under reduced pressure. The resulting solid was purified by silica gel chromatography (solvent: toluene:ethyl acetate = 4/1 → 2/1 (v/v)), yielding 2.81 g (yield 65%) of the desired silane coupling agent (Si1).

[Production Example 2] Production of silane coupling material (Si2)

5.52 g (99% yield) of the desired amine 5 was obtained in the same manner as in Preparation Example 1, except that bromo compound 4 (11.95 g, 30.00 mmol) was used instead of bromo compound 1.

7.84 g (yield 50%) of the desired silane coupling agent (Si2) was obtained in the same manner as in Example 1, except that amine 5 (9.00 g, 26.91 mmol) was used instead of amine 2.

[2] Preparation of metal oxide nanoparticles (sol) (comparison particles)
[Preparation Example 1]
A 500 ml recovery flask was charged with 250 g of MEK-dispersed silica sol (Nissan Chemical Industries, Ltd., MEK-ST, particle size 10-15 nm, SiO ₃₀ % by mass) and 170 g of triethylene glycol butyl methyl ether, and the flask was set in a rotary evaporator. The mixture was concentrated under reduced pressure until the mass reached 250 g, yielding a triethylene glycol butyl methyl ether-dispersed silica sol containing 30% SiO ₂ by mass.

[Preparation Example 2]
12 g of a PGMEA dispersion of zirconia particles (PixClear manufactured by Pixelligent Technologies, average particle size 7 to 10 nm, zirconia concentration: 50% by mass) and 24 g of triethylene glycol butyl methyl ether were placed in a 300 ml recovery flask and placed in a rotary evaporator. The mixture was concentrated under reduced pressure to a mass of 30 g, yielding a triethylene glycol butyl methyl ether-dispersed zirconia sol containing 20% by mass _of ZrO.

[3] Preparation of Surface-Treated Metal Oxide Nanoparticles (Sol) The "calculated modification amount" in each preparation example was determined by the following method.
The radius of the particle was taken as r, the surface area per particle was calculated from 4πr ² , and the volume per particle was calculated from 4πr ³ /3.
The weight per particle was calculated using the calculated particle volume and the specific gravity of SiO ₂ or ZrO ₂ .
The specific surface area per particle was calculated from the calculated weight per particle and the surface area per particle.
The modification amount X (number of particles/ ^nm2 ) was calculated using the specific surface area SA ( ^nm2 /g), the total amount of metal oxide particles M (g), the molecular weight Mw of the silane coupling agent, the amount Y (g) of the silane coupling agent, and the Avogadro constant L according to the formula Y = X * SA * M * Mw/L.
The specific gravity of _SiO2 was 2.2 g/ ^cm3 , and the specific gravity of _ZrO2 was 6.0 g/ ^cm3 . The radius r of the particles used in Preparation Examples 3 and 4 and Comparative Preparation Example 1 was 12 nm, and the radius r of the particles used in Preparation Examples 5 and 6 was 7 nm.

[Preparation Example 3]
5.0 g of methanol-dispersed silica sol (MT-ST, manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm, 30% by mass _{of SiO2} , specific gravity 2.2 g/ ^cm3 ), 10.0 g of triethylene glycol butyl methyl ether, and 0.2 g of Si1 were placed in a 50 ml recovery flask and heated under reflux at 60°C for 4 hours to modify the silica sol surface with Si1 (calculated modification amount: 0.5 particles/ ^nm2 ). After the reaction, the methanol was removed under reduced pressure using a rotary evaporator to obtain a triethylene glycol butyl methyl ether-dispersed Si1-modified silica sol (Si1-ST) with 15.9% by mass of _SiO2 .

[Preparation Example 4]
5.0 g of methanol-dispersed silica sol (MT-ST, manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm, 30 mass% _SiO2 , specific gravity 2.2 g/ ^cm3 ), 10.0 g of triethylene glycol butyl methyl ether, and 0.32 g of Si2 were placed in a 50 ml recovery flask and heated under reflux at 60°C for 4 hours to modify the silica sol surface with Si2 (calculated modification amount: 1.0 particles/ ^nm2 ). After the reaction, the methanol was removed under reduced pressure using a rotary evaporator to obtain a triethylene glycol butyl methyl ether-dispersed Si2-modified silica sol (Si2-ST) with 16.4 mass% _SiO2 .

Comparative Preparation Example 1
5.0 g of methanol-dispersed silica sol (MT-ST, manufactured by Nissan Chemical Industries, Ltd., particle size 10-15 nm, 30% by mass _{of SiO2} , specific gravity 2.2 g/ ^cm3 ), 10.0 g of triethylene glycol butyl methyl ether, and 0.66 g of Si2 were placed in a 50 ml recovery flask and heated under reflux at 60°C for 4 hours to modify the surface of the silica sol with Si2 (calculated modification amount: 2.0 particles/ ^nm2 ). However, settling of the particles was observed several hours after the reaction, and a modified silica sol could not be obtained.

[Preparation Example 5]
A 50 ml recovery flask was charged with 2 g of a PGMEA dispersion of zirconia particles (PixClear manufactured by Pixelligent Technologies, average particle size 7-10 nm, zirconia concentration: 50 mass%, specific gravity 6.0 g/cm ³ ), 5.67 g of triethylene glycol butyl methyl ether, and 0.09 g of Si1, and the mixture was heated under reflux at 60°C for 4 hours to modify the zirconia surface with Si1 (calculated modification amount: 0.5 particles/nm ² ). After the reaction, the PGMEA was removed under reduced pressure using a rotary evaporator, yielding a triethylene glycol butyl methyl ether-dispersed Si1-modified zirconia sol (Si1-ZrO2) containing 15.8 mass% SiO ₂ .

[Preparation Example 6]
A 50 ml recovery flask was charged with 2 g of a PGMEA dispersion of zirconia particles (PixClear manufactured by Pixelligent Technologies, average particle size 7-10 nm, zirconia concentration: 50 mass%, specific gravity 6.0 g/cm ³ ), 5.67 g of triethylene glycol butyl methyl ether, and 0.15 g of Si1, and the mixture was heated under reflux at 60°C for 4 hours to modify the zirconia surface with Si2 (calculated modification amount: 1 particle/nm ² ). After the reaction, the PGMEA was removed under reduced pressure using a rotary evaporator, yielding a triethylene glycol butyl methyl ether-dispersed Si2-modified zirconia sol (Si2-ZrO2) containing 17.1 mass% SiO ₂ .

[4] Preparation of charge-transporting varnish [Example 1-1]
Under a nitrogen atmosphere, 0.034 g of the following arylamine compound (A1) synthesized according to the method described in WO 2015/050253 and 0.091 g of the following arylsulfonate ester (D1) synthesized according to the method described in WO 2017/217455 were dissolved in a mixed solvent of 1.71 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate. To this was added 0.79 g of Si1-ST obtained in Preparation Example 3, and the mixture was stirred to obtain a charge-transporting varnish.

[Example 1-2]
Under a nitrogen atmosphere, 0.034 g of the arylamine compound (A1) and 0.091 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.67 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate. 0.83 g of Si2-ST obtained in Preparation Example 4 was added thereto and stirred to obtain a charge-transporting varnish.

[Examples 1-3]
Under a nitrogen atmosphere, 0.068 g of the arylamine compound (A1) and 0.18 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 0.93 g of triethylene glycol butyl methyl ether, 1.35 g of butyl benzoate, and 0.90 g of dimethyl phthalate. To this solution, 1.57 g of Si1-ST obtained in Preparation Example 3 was added and stirred to obtain a charge-transporting varnish.

[Examples 1-4]
Under a nitrogen atmosphere, 0.068 g of the arylamine compound (A1) and 0.18 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 0.83 g of triethylene glycol butyl methyl ether, 1.35 g of butyl benzoate, and 0.90 g of dimethyl phthalate. To this solution, 1.67 g of Si2-ST obtained in Preparation Example 4 was added and stirred to obtain a charge-transporting varnish.

[Comparative Example 1-1]
Under a nitrogen atmosphere, 0.041 g of the arylamine compound (A1) and 0.109 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.81 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate, and 0.67 g of the triethylene glycol butyl methyl ether-dispersed silica sol obtained in Preparation Example 1 was added thereto and stirred to obtain a charge-transporting varnish.

[Comparative Example 1-2]
Under a nitrogen atmosphere, 0.034 g of the arylamine compound (A1) and 0.091 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.67 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate, and 0.83 g of the triethylene glycol butyl methyl ether-dispersed silica sol obtained in Preparation Example 1 was added thereto and stirred to obtain a charge-transporting varnish.

[Comparative Examples 1-3]
Under a nitrogen atmosphere, 0.082 g of the arylamine compound (A1) and 0.218 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.12 g of triethylene glycol butyl methyl ether, 1.35 g of butyl benzoate, and 0.90 g of dimethyl phthalate. 1.33 g of the triethylene glycol butyl methyl ether-dispersed silica sol obtained in Preparation Example 1 was added thereto and stirred to obtain a charge-transporting varnish.

[Comparative Examples 1-4]
Under a nitrogen atmosphere, 0.068 g of the arylamine compound (A1) and 0.182 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 0.83 g of triethylene glycol butyl methyl ether, 1.35 g of butyl benzoate, and 0.90 g of dimethyl phthalate, to which 1.67 g of the triethylene glycol butyl methyl ether-dispersed silica sol obtained in Preparation Example 1 was added and stirred to obtain a charge-transporting varnish.

[Examples 1-5]
Under a nitrogen atmosphere, 0.048 g of the arylamine compound (A1) and 0.127 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.98 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate. 0.47 g of the Si1-ZrO2 obtained in Preparation Example 5 was added thereto and stirred to obtain a charge-transporting varnish.

[Examples 1-6]
Under a nitrogen atmosphere, 0.041 g of the arylamine compound (A1) and 0.11 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.84 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate. 0.63 g of the Si1-ZrO2 obtained in Preparation Example 5 was added thereto and stirred to obtain a charge-transporting varnish.

[Examples 1-7]
Under a nitrogen atmosphere, 0.048 g of the arylamine compound (A1) and 0.13 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 2.01 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate. 0.44 g of the Si2-ZrO2 obtained in Preparation Example 6 was added thereto and stirred to obtain a charge-transporting varnish.

[Examples 1-8]
Under a nitrogen atmosphere, 0.041 g of the arylamine compound (A1) and 0.11 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.89 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate. 0.58 g of the Si2-ZrO2 obtained in Preparation Example 6 was added thereto and stirred to obtain a charge-transporting varnish.

[Comparative Examples 1-5]
Under a nitrogen atmosphere, 0.048 g of the arylamine compound (A1) and 0.13 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 2.08 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate, and 0.37 g of the triethylene glycol butyl methyl ether-dispersed zirconia sol obtained in Preparation Example 2 was added thereto and stirred to obtain a charge-transporting varnish.

[Comparative Examples 1-6]
Under a nitrogen atmosphere, 0.041 g of the arylamine compound (A1) and 0.11 g of the arylsulfonic acid ester (D1) were dissolved in a mixed solvent of 1.98 g of triethylene glycol butyl methyl ether, 1.43 g of butyl benzoate, and 0.95 g of dimethyl phthalate, and 0.49 g of the triethylene glycol butyl methyl ether-dispersed zirconia sol obtained in Preparation Example 2 was added thereto and stirred to obtain a charge-transporting varnish.

[5] Production of charge transport thin film and evaluation of transmittance [Example 2-1]
The varnish obtained in Example 1-1 was applied to a quartz substrate using a spin coater, and then dried in air at 120°C for 1 minute. Next, the dried quartz substrate was baked in air at 230°C for 15 minutes to form a uniform thin film of 50 nm on the quartz substrate.

[Example 2-2, Comparative Example 2-1, and Comparative Example 2-2]
Thin films were formed in the same manner as in Example 2-1, except that the varnishes obtained in Example 1-2, Comparative Example 1-1 and Comparative Example 1-2 were used instead of the varnish obtained in Example 1-1.

[Example 2-3]
The varnish obtained in Example 1-3 was applied to a quartz substrate using a spin coater and then dried in air at 120°C for 1 minute. The dried quartz substrate was then baked in air at 230°C for 15 minutes to form a uniform thin film of 100 nm on the quartz substrate.

[Examples 2-4, Comparative Examples 2-3 and 2-4]
Thin films were formed in the same manner as in Example 2-1, except that the varnishes obtained in Example 1-4, Comparative Example 1-3 and Comparative Example 1-4 were used instead of the varnish obtained in Example 1-3.

[Examples 2-5 to 2-8 and Comparative Examples 2-5 to 2-6]
Thin films were formed in the same manner as in Example 2-1, except that the varnishes obtained in Examples 1-5 to 1-8, Comparative Example 1-5, and Comparative Example 1-6 were used instead of the varnish obtained in Example 1-1.

The light transmittance of the thin-film-coated quartz substrates obtained in each of the above examples and comparative examples was measured using a spectrophotometer. The results are shown in Figures 1 to 3 and Tables 1 and 2.

As shown in Figures 1 and 2 and Table 1, even when organosilica sol modified with silane coupling agents Si1 and Si2 (Si1-ST, Si2-ST) was added, the average light transmittance in the visible region was found to be similar to that when triethylene glycol butyl methyl ether-dispersed silica sol was added.
That is, it was shown that the charge transporting thin film of the present invention containing silica particles modified with a silane coupling agent can maintain excellent transmittance in the visible region.

On the other hand, as shown in FIG. 3 and Table 2, even when zirconia sol modified with silane coupling agents Si1 and Si2 (Si1-ZrO2, ZrO2) was added, the average light transmittance in the visible region was found to be similar to that when triethylene glycol butyl methyl ether dispersed zirconia sol was added.
That is, it was shown that the charge transporting thin film of the present invention containing zirconia particles modified with a silane coupling agent can maintain excellent transmittance in the visible region.

[6] Fabrication and Characterization of Hole-Only Device (HOD) [Example 3-1]
The varnish obtained in Example 1-1 was applied to an ITO substrate using a spin coater and then dried in air at 120°C for 1 minute. The dried ITO substrate was then baked in air at 230°C for 15 minutes to form a uniform 50 nm thin film on the ITO substrate. The ITO substrate was a 25 mm x 25 mm x 0.7 mm glass substrate with a patterned 150 nm thick indium tin oxide (ITO) film formed on its surface. Prior to use, impurities on the surface were removed using an _O2 plasma cleaning device (150 W, 30 seconds).
Next, a 30 ^nm film of α-NPD (N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine) was formed at 0.2 nm/sec on the ITO substrate with the thin film formed thereon using a vapor deposition apparatus (vacuum degree 1.0 × 10 -5 Pa). Next, an 80 nm film of aluminum was formed at 0.2 nm/sec to prepare a hole-only device.
To prevent performance degradation due to the effects of oxygen and water in the air, the device was sealed with a sealing substrate before its performance evaluation. Sealing was performed using 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 device was placed between sealing substrates, which were then bonded together with an adhesive (Moresco Moisture Cut WB90US(P) manufactured by MORESCO Corporation). A moisture scavenger (HD-071010W-40 manufactured by DYNIC Corporation) was placed inside the sealing substrate along with the device. The bonded sealing substrates were then irradiated with UV light (wavelength: 365 nm, dose: 6,000 mJ/ ^cm2 ) and annealed at 80°C for 1 hour to cure the adhesive.

[Example 3-2, Comparative Example 3-1, and Comparative Example 3-2]
HOD was obtained in the same manner as in Example 3-1, except that the varnish obtained in Example 1-2, Comparative Example 1-1, and Comparative Example 1-2 were used instead of the varnish obtained in Example 1-1.

[Example 3-3]
HOD was obtained in the same manner as in Example 3-1, except that the varnish obtained in Example 1-3 was used instead of the varnish obtained in Example 1-1 and the film thickness was set to 100 nm.

[Examples 3-4, Comparative Examples 3-3 and 3-4]
HOD was obtained in the same manner as in Example 3-3, except that the varnish obtained in Example 1-4, Comparative Example 1-3, and Comparative Examples 1 to 4 were used instead of the varnish obtained in Example 1-1.

[Examples 3-5 to 3-8 and Comparative Examples 3-5 to 3-6]
HOD was obtained in the same manner as in Example 3-1, except that the varnish obtained in Examples 1-5 to 1-8 and Comparative Examples 1-5 to 1-6 were used instead of the varnish obtained in Example 1-1.

The current density of the obtained HOD was measured when driven at 5 V. The results are shown in Tables 3 and 4.

As shown in Table 3, it can be seen that the thin film prepared from the charge transport varnish of the present invention, which uses silica modified with a silane coupling agent having a conductive functional group, exhibits better charge transport properties than the thin film of the comparative example.
On the other hand, as shown in Table 4, it can be seen that the thin film prepared from the charge transport varnish of the present invention, which uses zirconia modified with a silane coupling agent having a specific conductive functional group, exhibits better charge transport properties than the thin film of the comparative example.

Claims (10)

A charge transporting material, a dopant material, metal oxide nanoparticles that have been surface-treated with a silane coupling agent having a conductive functional group, and a solvent,
A charge-transporting varnish characterized in that the silane coupling agent is a compound represented by the following formula (S1):
(In the formula, R represents an alkyl group having 1 to 5 carbon atoms, A ¹ represents an alkylene group having 2 to 5 carbon atoms, A ² represents —O—, —S—, —NH—, an amide bond, a urea bond, or a combination thereof, and A ³ represents an aryl group having a phenylcarbazole structure.) 2. The charge-transporting varnish according to claim 1, wherein ^A3 is at least one selected from the group consisting of formulas (A3-1), (A3-4), and (A3-9).
(In the formula, the asterisk * represents a bond, and ^A4 represents an arylene group.) 2. The charge-transporting varnish according to claim 1, wherein the silane coupling agent is a compound represented by the following formula (S1-1):
(In the formula, R represents an alkyl group having 1 to 5 carbon atoms, A ¹ represents an alkylene group having 2 to 5 carbon atoms, and A ⁴ represents an arylene group.) The charge-transporting varnish according to any one of claims 1 to 3, wherein the metal oxide nanoparticles are at least one selected from silica and zirconia. The charge-transporting varnish according to any one of claims 1 to 4, wherein the charge-transporting substance is an arylamine derivative. The charge-transporting varnish according to any one of claims 1 to 5, wherein the dopant substance is an arylsulfonic acid compound. A charge-transporting thin film obtained from the charge-transporting varnish described in any one of claims 1 to 6. An electronic device comprising the charge transport thin film of claim 7. An organic electroluminescence device comprising the charge transport thin film according to claim 7. The organic electroluminescence device according to claim 9, wherein the charge transport thin film is a hole injection layer or a hole transport layer.