JP7497724B2 - Charge Transporting Varnish - Google Patents

Description

The present invention relates to a charge transporting varnish.

In organic electroluminescence (hereinafter referred to as organic EL) elements, charge transporting thin 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 the transfer of charges between the anode and the hole transport layer or the light emitting layer, and plays an important role in achieving low voltage operation and high brightness of the organic EL element.
The methods for forming the hole injection layer are roughly divided into dry processes, such as vapor deposition, and wet processes, such as spin coating. Comparing these processes, wet processes can efficiently manufacture thin films with high flatness over a large area. 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.
In view of these circumstances, the present inventors have developed charge transport materials which are applicable to various wet processes and which, when applied to a hole injection layer of an organic EL element, give thin films capable of realizing excellent EL element characteristics, as well as compounds which have good solubility in organic solvents used therein (see, for example, Patent Documents 1 to 3).

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

Furthermore, because coloring of a charge-transporting thin film used in an organic EL element reduces the color purity and color reproducibility of the organic EL element, in recent years, it has been desired that a charge-transporting thin film for an organic EL element has a high transmittance in the visible region and high transparency (see, for example, Patent Document 6).
In view of this, the present applicant has already found a material for wet processing that gives a charge transporting thin film with excellent transparency and suppressed coloration in the visible region (see, for example, Patent Documents 6 and 7).
However, as organic EL displays are currently being made larger in area, vigorous development is being carried out toward the practical application of organic EL displays using wet processes, and there is a constant demand for wet process materials that can provide highly transparent charge-transporting thin films.

International Publication No. 2008/129947 International Publication No. 2015/050253 International Publication No. 2017/217457 JP 2007-536718 A JP 2017-501585 A International Publication No. 2013/042623 International Publication No. 2008/032616

The present invention has been made in consideration of the above circumstances, and aims to provide a charge transport varnish that reproducibly produces a charge transport thin film having a high refractive index and transparency and excellent charge transport properties.

As a result of extensive research into achieving the above-mentioned object, the inventors have discovered that a charge-transporting thin film having excellent flatness, a high refractive index and transparency, and excellent charge transport properties can be reproducibly obtained from a charge-transporting varnish containing a charge-transporting substance, titanium oxide-containing particles surface-modified with a surface treatment agent, and an organic solvent, and that when the thin film is applied to an organic EL element, excellent brightness characteristics can be achieved, thus completing the present invention.

（式中、Ｒ¹およびＲ²は、互いに独立して、水素原子、炭素数１～４０のアルキル基、炭素数１～４０のフルオロアルキル基、炭素数１～４０のアルコキシ基、炭素数１～４０のフルオロアルコキシ基、炭素数６～２０のアリールオキシ基、－Ｏ－［Ｚ－Ｏ］_p－Ｒ^e、もしくはスルホン酸基であり、またはＲ¹およびＲ²が結合して形成される－Ｏ－Ｙ－Ｏ－であり、Ｙは、エーテル結合を含んでいてもよく、スルホン酸基で置換されていてもよい炭素数１～４０のアルキレン基であり、Ｚは、ハロゲン原子で置換されていてもよい炭素数１～４０のアルキレン基であり、ｐは、１以上の整数であり、Ｒ^eは、水素原子、炭素数１～４０のアルキル基、炭素数１～４０のフルオロアルキル基、または炭素数６～２０のアリール基である。）
７． 上記Ｒ¹が、スルホン酸基であり、上記Ｒ²が、炭素数１～４０のアルコキシ基もしくは－Ｏ－［Ｚ－Ｏ］_p－Ｒ^eである、または上記Ｒ¹およびＲ²が結合して形成される－Ｏ－Ｙ－Ｏ－である１～６のいずれかの電荷輸送性ワニス。
８． さらに、ヘテロポリ酸を含む１～７のいずれかの電荷輸送性ワニス。
９． 上記ヘテロポリ酸が、リンタングステン酸である８の電荷輸送性ワニス。
１０． １～９のいずれかの電荷輸送性ワニスから得られる電荷輸送性薄膜。
１１． １０の電荷輸送性薄膜を有する有機エレクトロルミネッセンス素子。
１２． 上記電荷輸送性薄膜が、正孔注入層または正孔輸送層である１１の有機エレクトロルミネッセンス素子。
１３． １～９のいずれかの電荷輸送性ワニスを基材上に塗布し、溶媒を蒸発させることを特徴とする電荷輸送性薄膜の製造方法。
１４． １３の電荷輸送性薄膜を用いることを特徴とする有機エレクトロルミネッセンス素子の製造方法。 That is, the present invention provides the following charge-transporting varnish.
1. A charge-transporting varnish comprising a charge-transporting substance, titanium oxide-containing particles whose surfaces have been modified with a surface treatment agent, and an organic solvent.
2. The charge transporting varnish according to 1, wherein the titanium oxide-containing particles that have been surface-modified with the surface treatment agent are colloidal particles.
3. The charge transport varnish of 2, wherein the titanium oxide-containing particles surface-modified with the surface treatment agent are colloid particles (D) (surface-modified colloid particles (D)) formed by coating a titanium oxide-containing colloid particle (A) as a core (core particle (A)) with a metal oxide colloid particle (B) (coating material (B)) as a modified titanium oxide-containing colloid particle (C) (modified colloid particle (C)) with an amphiphilic surface treatment agent.
4. The charge transporting varnish of 1 or 2, wherein the surface treatment agent is an amphiphilic surface treatment agent.
5. The charge-transporting varnish of 3 or 4, wherein the amphiphilic surface treatment agent is an organosilicon compound, a titanate coupling agent, an aluminate coupling agent or a phosphorus-based surfactant.
6. The charge-transporting varnish according to any one of 1 to 5, wherein the charge-transporting substance is a polythiophene derivative containing a repeating unit represented by formula (1) or an amine adduct thereof.

(In the formula, R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, a fluoroalkoxy group having 1 to 40 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, -O-[Z-O] _p -R ^e , or a sulfonic acid group, or R ¹ and R ² are bonded to form -O-Y-O-, Y is an alkylene group having 1 to 40 carbon atoms which may contain an ether bond and which may be substituted with a sulfonic acid group, Z is an alkylene group having 1 to 40 carbon atoms which may be substituted with a halogen atom, p is an integer of 1 or more, and R ^e is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)
7. The charge transporting varnish according to any one of 1 to 6, wherein R ¹ is a sulfonic acid group, and R ² is an alkoxy group having 1 to 40 carbon atoms or -O-[ZO] _p -R ^e , or R ¹ and R ² are bonded to form -O-Y-O-.
8. The charge transporting varnish according to any one of 1 to 7, further comprising a heteropolyacid.
9. The charge transporting varnish according to claim 8, wherein the heteropolyacid is phosphotungstic acid.
10. A charge-transporting thin film obtained from the charge-transporting varnish according to any one of 1 to 9.
11. An organic electroluminescence device having the charge transporting thin film of 10.
12. The organic electroluminescence device of 11, wherein the charge transporting thin film is a hole injection layer or a hole transport layer.
13. A method for producing a charge-transporting thin film, comprising applying the charge-transporting varnish according to any one of 1 to 9 onto a substrate and evaporating the solvent.
14. A method for producing an organic electroluminescence device, comprising using the charge transporting thin film according to 13.

By using the charge transporting varnish of the present invention, a charge transporting thin film having excellent flatness, a high refractive index (high n) and transparency (low extinction coefficient k), and excellent charge transporting properties can be obtained.
By applying such a charge transporting thin film of the present invention to a hole injection layer or a hole transport layer, preferably to a hole injection layer, of an organic EL element, an organic EL element exhibiting good luminance characteristics can be realized.
Furthermore, the charge transporting varnish of the present invention can reproducibly produce thin films with excellent charge transport properties even when various wet processes capable of forming films over large areas, such as spin coating and inkjet methods, and can therefore fully respond to recent developments in the field of organic EL elements.

The present invention will be described in further detail below.
The charge-transporting varnish of the present invention contains a charge-transporting substance, titanium oxide-containing particles whose surfaces have been modified with a surface treatment agent (hereinafter, also referred to as surface-modified titanium oxide-containing particles), and an organic solvent.
In the present invention, the "solid content" of the charge-transporting varnish of the present invention means the components other than the solvent contained in the varnish. In addition, the charge transporting property is synonymous with the electrical conductivity and the hole transporting property. The charge-transporting varnish of the present invention may have the charge transporting property by itself, or the solid film obtained by using the varnish may have the charge transporting property.

The charge transporting substance used in the present invention is not particularly limited, and can be appropriately selected from 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 and charge transporting oligomers such as arylamine derivatives, such as oligoaniline derivatives, N,N'-diarylbenzidine derivatives, and N,N,N',N'-tetraarylbenzidine derivatives; thiophene derivatives, such as thienothiophene derivatives, and thienobenzothiophene derivatives; and pyrrole derivatives, such as oligopyrrole; and charge transporting polymers, such as polythiophene derivatives, polyaniline derivatives, and polypyrrole derivatives. In particular, polythiophene derivatives are preferred.
In a preferred embodiment, the charge transporting substance is a polythiophene derivative containing a repeating unit represented by formula (1) or an amine adduct thereof.

In the formula, R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, a fluoroalkoxy group having 1 to 40 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, -O-[Z-O] _p -R ^e , or a sulfonic acid group, or R ¹ and R ² are bonded to form -O-Y-O-, Y is an alkylene group having 1 to 40 carbon atoms which may contain an ether bond and which may be substituted with a sulfonic acid group, Z is an alkylene group having 1 to 40 carbon atoms which may be substituted with a halogen atom, p is an integer of 1 or more, and R ^e is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

The alkyl group having 1 to 40 carbon atoms may be linear, branched, or cyclic, and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosanyl, behenyl, triacontyl, and tetracontyl. In the present invention, alkyl groups having 1 to 18 carbon atoms are preferred, and alkyl groups having 1 to 8 carbon atoms are more preferred.

The fluoroalkyl group having 1 to 40 carbon atoms is not particularly limited as long as it is an alkyl group having 1 to 40 carbon atoms in which at least one hydrogen atom on a carbon atom is replaced with a fluorine atom, and examples thereof include a fluoromethyl group, a difluoromethyl group, a perfluoromethyl group, a 1-fluoroethyl group, a 2-fluoroethyl group, a 1,2-difluoroethyl group, a 1,1-difluoroethyl group, a 2,2-difluoroethyl group, a 1,1,2-trifluoroethyl group, a 1,2,2-trifluoroethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a 1,2,2,2-tetrafluoroethyl group, a perfluoroethyl group, a 1-fluoropropyl group, a 2-fluoropropyl group, a 3-fluoropropyl group, a 1,1-difluoropropyl group, a 1,2-difluoropropyl group, a 1,3-difluoropropyl group, a 2,2-difluoropropyl group, a 2,3-difluoropropyl group, a 3,3-difluoropropyl group, a 1,1,2-trifluoropropyl group, a 1, 1,3-trifluoropropyl group, 1,2,3-trifluoropropyl group, 1,3,3-trifluoropropyl group, 2,2,3-trifluoropropyl group, 2,3,3-trifluoropropyl group, 3,3,3-trifluoropropyl group, 1,1,2,2-tetrafluoropropyl group, 1,1,2,3-tetrafluoropropyl group, 1,2,2,3-tetrafluoropropyl group, 1,3,3,3-tetrafluoropropyl group, 2,2,3,3-tetrafluoropropyl group, 2, Examples of such groups include a 3,3,3-tetrafluoropropyl group, a 1,1,2,2,3-pentafluoropropyl group, a 1,2,2,3,3-pentafluoropropyl group, a 1,1,3,3,3-pentafluoropropyl group, a 1,2,3,3,3-pentafluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group, a perfluoroheptyl group, and a perfluorooctyl group.

The alkoxy group having 1 to 40 carbon atoms may have a linear, branched, or cyclic alkyl group, and examples thereof include methoxy, ethoxy, n-propoxy, i-propoxy, c-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, n-pentoxy, n-hexoxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, n-tridecyloxy, n-tetradecyloxy, n-pentadecyloxy, n-hexadecyloxy, n-heptadecyloxy, n-octadecyloxy, n-nonadecyloxy, and n-eicosanyloxy.

The fluoroalkoxy group having 1 to 40 carbon atoms is not particularly limited as long as it is an alkoxy group having 1 to 40 carbon atoms in which at least one hydrogen atom on a carbon atom is replaced with a fluorine atom, and examples thereof include a fluoromethoxy group, a difluoromethoxy group, a perfluoromethoxy group, a 1-fluoroethoxy group, a 2-fluoroethoxy group, a 1,2-difluoroethoxy group, a 1,1-difluoroethoxy group, a 2,2-difluoroethoxy group, a 1,1,2-trifluoroethoxy group, a 1,2, 2-trifluoroethoxy group, 2,2,2-trifluoroethoxy group, 1,1,2,2-tetrafluoroethoxy group, 1,2,2,2-tetrafluoroethoxy group, perfluoroethoxy group, 1-fluoropropoxy group, 2-fluoropropoxy group, 3-fluoropropoxy group, 1,1-difluoropropoxy group, 1,2-difluoropropoxy group, 1,3-difluoropropoxy group, 2,2-difluoropropoxy group, 2,3-difluoropropoxy group, 3,3- Difluoropropoxy group, 1,1,2-trifluoropropoxy group, 1,1,3-trifluoropropoxy group, 1,2,3-trifluoropropoxy group, 1,3,3-trifluoropropoxy group, 2,2,3-trifluoropropoxy group, 2,3,3-trifluoropropoxy group, 3,3,3-trifluoropropoxy group, 1,1,2,2-tetrafluoropropoxy group, 1,1,2,3-tetrafluoropropoxy group, 1,2,2,3-tetrafluoropropoxy group groups, 1,3,3,3-tetrafluoropropoxy groups, 2,2,3,3-tetrafluoropropoxy groups, 2,3,3,3-tetrafluoropropoxy groups, 1,1,2,2,3-pentafluoropropoxy groups, 1,2,2,3,3-pentafluoropropoxy groups, 1,1,3,3,3-pentafluoropropoxy groups, 1,2,3,3,3-pentafluoropropoxy groups, 2,2,3,3,3-pentafluoropropoxy groups, and perfluoropropoxy groups.

The alkylene group having 1 to 40 carbon atoms may be linear, branched, or cyclic, and examples include methylene, ethylene, propylene, trimethylene, tetramethylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, nonadecylene, and eicosanylene.

Examples of aryl groups having 6 to 20 carbon atoms include phenyl, tolyl, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, and 9-phenanthryl groups, with phenyl, tolyl, and naphthyl groups being preferred.

Examples of aryloxy groups having 6 to 20 carbon atoms include phenoxy groups, anthracenoxy groups, naphthoxy groups, phenanthrenoxy groups, and fluorenoxy groups.

Halogen atoms include fluorine, chlorine, bromine and iodine atoms.

In the above formula (1), R ¹ and R ² are each independently a hydrogen atom, a fluoroalkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, -O[C(R ^a R ^b )-C(R ^c R ^d )-O] _p -R ^e , -OR ^f , or a sulfonic acid group, or R ¹ and R ² are preferably bonded to form -O-Y-O-.
R ^a to R ^d each independently represent a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and specific examples of these groups are the same as those listed above.
Among these, R ^a to R ^d are preferably each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group.
R ^e is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group, and is preferably a hydrogen atom, a methyl group, a propyl group, or a butyl group.
Furthermore, p is preferably 1 to 5, and more preferably 1, 2 or 3.

^Rf is a hydrogen atom, an alkyl group having 1 to 40 carbon atoms, a fluoroalkyl group having 1 to 40 carbon atoms, or an aryl group having 6 to 20 carbon atoms, preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl _group , more preferably _--CH2CF3 .

In the present invention, R ¹ is preferably a hydrogen atom or a sulfonic acid group, more preferably a sulfonic acid group, and R ² is preferably an alkoxy group having 1 to 40 carbon atoms or -O-[Z-O] _p -R ^e , more preferably -O[C(R ^a R ^b )-C(R ^c R ^d )-O] _p -R ^e or -OR ^f , even more preferably -O[C(R ^a R ^b )-C(R ^c R ^d )-O] _p -R ^e , -O-CH ₂ CH ₂ -O-CH ₂ CH ₂ -O-CH ₃ , -O-CH ₂ CH ₂ -O-CH ₂ CH ₂ -OH or -O-CH ₂ CH ₂ -OH, or -O-Y-O- formed by R ¹ and R ² bonding to each other.

For example, the polythiophene derivative according to a preferred embodiment of the present invention includes a repeating unit in which R ¹ is a sulfonic acid group and R ² is other than a sulfonic acid group, or includes a repeating unit in which R ¹ and R ² are bonded to form -O-Y-O-.
Preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is an alkoxy group having 1 to 40 carbon atoms or -O-[Z-O] _p -R ^e , or contains a repeating unit in which R ¹ and R ² are bonded to form -O-Y-O-.
More preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a ^sulfonic acid group and ^{R 2} is --O[C( ^{R.sup.aR.sup.b} )--C( ^{R.sup.cR.sup.d )} --O] _{.sup.pR.sup.e} or ^--OR.sup.f .
Even more preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is -O[C(R ^a R ^b )-C(R ^c R ^d )-O] _p -R ^e , or contains a repeating unit in which R ¹ and R ² are bonded to form -O-Y-O-.
More preferably, the polythiophene derivative contains a repeating unit in which R ¹ is a sulfonic acid group and R ² is -O-CH ₂ CH ₂ -O-CH ₂ CH ₂ -O-CH ₃ , -O-CH ₂ CH ₂ -O-CH ₂ CH ₂ -OH or -O-CH ₂ CH ₂ -OH, or contains a repeating unit in which R ¹ and R ² are bonded to each other to form groups represented by the following formulae (Y1) and (Y2).

Preferred examples of the polythiophene derivatives include polythiophenes containing at least one repeating unit represented by the following formulas (1-1) to (1-5).

In addition, a suitable structure of the polythiophene derivative is, for example, a polythiophene derivative having a structure represented by the following formula (1a). In the following formula, each unit may be bonded randomly or as a block polymer.

In the formula, a to d represent the molar ratios of each unit and satisfy 0≦a≦1, 0≦b≦1, 0<a+b≦1, 0≦c<1, 0≦d<1, and a+b+c+d=1.

Furthermore, the polythiophene derivatives can be homopolymers or copolymers (including statistical, random, gradient, and block copolymers). For polymers containing monomer A and monomer B, block copolymers include, for example, A-B diblock copolymers, A-B-A triblock copolymers, and (AB) _m -multiblock copolymers. Polythiophenes can also contain repeat units derived from other types of monomers, such as thienothiophenes, selenophenes, pyrroles, furans, tellurophenes, anilines, arylamines, and arylenes (e.g., phenylene, phenylenevinylene, and fluorene, etc.).

In the present invention, the content of the repeating unit represented by formula (1) in the polythiophene derivative is preferably more than 50 mol % of all repeating units contained in the polythiophene derivative, more preferably 80 mol % or more, even more preferably 90 mol % or more, even more preferably 95 mol % or more, and most preferably 100 mol %.

In the present invention, depending on the purity of the starting monomers used in the polymerization, the polymer formed may contain repeat units derived from impurities. In the present invention, the term "homopolymer" means a polymer containing repeat units derived from one type of monomer, but may contain repeat units derived from impurities. In the present invention, the polythiophene derivative is preferably a polymer in which essentially all repeat units are repeat units represented by the above formula (1), and more preferably a polymer containing at least one of the repeat units represented by the above formulas (1-1) to (1-5).

In the present invention, when the above polythiophene derivative contains a repeating unit having a sulfonic acid group, from the viewpoint of further improving the solubility and dispersibility in organic solvents, it is preferable to form an amine adduct in which an amine compound is added to at least a portion of the sulfonic acid groups contained in the polythiophene derivative.

Examples of amine compounds that can be used to form the amine adduct include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, s-butylamine, t-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, and n-octadecylamine. monoalkylamine compounds such as amine, n-nonadecylamine, and n-eicosanylamine; primary amine compounds such as monoarylamine compounds such as aniline, tolylamine, 1-naphthylamine, 2-naphthylamine, 1-anthrylamine, 2-anthrylamine, 9-anthrylamine, 1-phenanthrylamine, 2-phenanthrylamine, 3-phenanthrylamine, 4-phenanthrylamine, and 9-phenanthrylamine; N-ethylmethylamine, N-methyl-n-propylamine, N-methylisopropylamine, N-methyl-n-butylamine, N- Methyl-s-butylamine, N-methyl-t-butylamine, N-methylisobutylamine, diethylamine, N-ethyl-n-propylamine, N-ethylisopropylamine, N-ethyl-n-butylamine, N-ethyl-s-butylamine, N-ethyl-t-butylamine, dipropylamine, N-n-propylisopropylamine, N-n-propyl-n-butylamine, N-n-propyl-s-butylamine, diisopropylamine, N-n-butylisopropylamine, N-t-butylisopropylamine, di(n-butyl)amine, di(s-butyl)amine dialkylamine compounds such as amine, diisobutylamine, aziridine (ethyleneimine), 2-methylaziridine (propyleneimine), 2,2-dimethylaziridine, azetidine (trimethyleneimine), 2-methylazetidine, pyrrolidine, 2-methylpyrrolidine, 3-methylpyrrolidine, 2,5-dimethylpyrrolidine, piperidine, 2,6-dimethylpiperidine, 3,5-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, hexamethyleneimine, heptamethyleneimine, and octamethyleneimine; diphenylamine, N-phenyl-1-naphthylamine, diarylamine compounds such as N-phenyl-2-naphthylamine, 1,1'-dinaphthylamine, 2,2'-dinaphthylamine, 1,2'-dinaphthylamine, carbazole, 7H-benzo[c]carbazole, 11H-benzo[a]carbazole, 7H-dibenzo[c,g]carbazole, and 13H-dibenzo[a,i]carbazole; N-methylaniline, N-ethylaniline, N-n-propylaniline, N-isopropylaniline, N-n-butylaniline, N-s-butylaniline, N-isobutylaniline, N-methyl-1-naphthylamine ...isobutylaniline, N-methyl-2-naphthylamine, N-n-butylaniline, N-n-butylaniline, N-isobutylaniline, N-methyl-1-naphthylamine, N-n-butylaniline, N-n-butylaniline, N-n-butylaniline, N-n-butylaniline, N-n-butylaniline, N-n-butylaniline, N-n-butyl-1-naphthylamine, N-n-n-butyl-1-naphthylamine, N-n-n-butyl-1-naphthylamine, N-n-n-butyl-1-naphthylamine, N-n-n-butyl-1-naphthylamine, N-n-n-n-butyl-1-naph secondary amine compounds such as alkylarylamine compounds, such as N-n-naphthylamine, N-n-propyl-1-naphthylamine, indoline, isoindoline, 1,2,3,4-tetrahydroquinoline, and 1,2,3,4-tetrahydroisoquinoline; trialkylamine compounds such as (n-propyl)amine, N-methyldiisopropylamine, N-methyldi(n-butyl)amine, N-methyldiisobutylamine, triethylamine, N,N-diethyl-n-butylamine, N,N-diisopropylethylamine, N,N-di(n-butyl)ethylamine, tri(n-propyl)amine, tri(i-propyl)amine, tri(n-butyl)amine, tri(i-butyl)amine, 1-methylacetidine, 1-methylpyrrolidine, and 1-methylpiperidine; triarylamine compounds such as triphenylamine; Examples of tertiary amine compounds include alkyldiarylamine compounds such as N,N-phenylamine, N-ethyldiphenylamine, 9-methylcarbazole, and 9-ethylcarbazole; and dialkylarylamine compounds such as N,N-diethylaniline, N,N-di(n-propyl)aniline, N,N-di(i-propyl)aniline, and N,N-di(n-butyl)aniline. In consideration of the balance between the solubility of the amine adduct, the charge transport property of the resulting charge transporting thin film, and the like, tertiary amine compounds are preferred, trialkylamine compounds are more preferred, and triethylamine is even more preferred.
The amine adduct can be obtained by adding the polythiophene derivative to an amine itself or a solution of the amine and thoroughly stirring the mixture.

In the present invention, the above polythiophene derivative or its amine adduct may be treated with a reducing agent.
In polythiophene derivatives or their amine adducts, some of the repeating units constituting them may have an oxidized structure called a "quinoid structure". The term "quinoid structure" is used in contrast to the term "benzenoid structure", and the former refers to a structure in which a double bond in the aromatic ring moves outside the ring (as a result, the aromatic ring disappears), while the latter is a structure containing an aromatic ring, and two exocyclic double bonds are formed that are conjugated with other double bonds remaining in the ring. Those skilled in the art can easily understand the relationship between these two structures from the relationship between the structures of benzoquinone and hydroquinone. Quinoid structures for the repeating units of various conjugated polymers are well known to those skilled in the art. As an example, a quinoid structure corresponding to the repeating unit of a polythiophene derivative containing the repeating unit represented by the above formula (1) is shown in the following formula (1').

（式中、Ｒ¹およびＲ²は、上記式（１）において定義されたとおりである。）

(In the formula, R ¹ and R ² are as defined in formula (1) above.)

This quinoid structure is a part of the structure called "polaron structure" and "bipolaron structure" that is generated by the process in which the polythiophene derivative containing the repeating unit represented by the above formula (1) is oxidized by a dopant, that is, by a doping reaction, and imparts charge transport properties to the polythiophene derivative. These structures are publicly known. In the production of an organic EL element, the introduction of a "polaron structure" and/or a "bipolaron structure" is essential, and in fact, when the thin film formed from the charge transport varnish is baked during the production of the organic EL element, the above-mentioned doping reaction is intentionally caused to occur, thereby achieving this. The reason why the polythiophene derivative contains a quinoid structure before the doping reaction is thought to be that the polythiophene derivative underwent an unintended oxidation reaction equivalent to the doping reaction during the production process (particularly the sulfonation process therein).

There is a correlation between the amount of quinoid structure contained in the polythiophene derivative and the solubility and dispersibility of the polythiophene derivative in organic solvent, and the more the amount of quinoid structure, the lower the solubility and dispersibility.Therefore, the introduction of the quinoid structure after the thin film is formed from the charge transport varnish does not cause any problems, but if the quinoid structure is excessively introduced into the polythiophene derivative due to the above-mentioned unintended oxidation reaction, it may cause problems in the production of the charge transport varnish.It is known that the solubility and dispersibility of polythiophene derivatives in organic solvents varies, and one of the causes is thought to be that the amount of the quinoid structure introduced into the polythiophene due to the above-mentioned unintended oxidation reaction varies depending on the difference in the production conditions of each polythiophene derivative.
Therefore, when the above-mentioned polythiophene derivative is subjected to a reduction treatment using a reducing agent, even if an excessive amount of quinoid structures has been introduced into the polythiophene derivative, the quinoid structures are reduced by the reduction, and the solubility and dispersibility of the polythiophene derivative in organic solvents are improved, making it possible to stably produce a good charge-transporting varnish that gives a thin film with excellent homogeneity.

The conditions for the reduction treatment are not particularly limited as long as the quinoid structure can be reduced and appropriately converted into a non-oxidized structure, i.e., the benzenoid structure (for example, in a polythiophene derivative containing a repeating unit represented by formula (1) above, the quinoid structure represented by formula (1') above is converted into a structure represented by formula (1) above). For example, this treatment can be carried out by simply contacting the polythiophene derivative or the amine adduct with a reducing agent in the presence or absence of a suitable solvent.
There are no particular limitations on the reducing agent as long as the reduction is carried out appropriately, and suitable examples of the reducing agent include aqueous ammonia and hydrazine, which are readily available commercially.
The amount of the reducing agent cannot be generally specified since it varies depending on the amount of the reducing agent used. However, the amount is usually 0.1 part by mass or more per 100 parts by mass of the polythiophene derivative or amine adduct to be treated in order to ensure that the reduction is performed appropriately, and is 10 parts by mass or less in order to prevent excess reducing agent from remaining.

As an example of a specific method of reduction treatment, the polythiophene derivative or the amine adduct is stirred overnight at room temperature in 28% ammonia water. By carrying out reduction treatment under such relatively mild conditions, the solubility and dispersibility of the polythiophene derivative or the amine adduct in organic solvents is sufficiently improved.

When an amine adduct of a polythiophene derivative is used in the charge-transporting varnish of the present invention, the above-mentioned reduction treatment may be carried out either before or after the formation of the amine adduct.

Note that this reduction treatment changes the solubility and dispersibility of the polythiophene derivative or its amine adduct in the solvent, and as a result, the polythiophene derivative or its amine adduct that was not dissolved in the reaction system at the start of the treatment may be dissolved by the end of the treatment. In such cases, the polythiophene derivative or its amine adduct can be recovered by adding an organic solvent that is incompatible with the polythiophene derivative or its amine adduct (acetone, isopropyl alcohol, etc. in the case of sulfonated polythiophene) to the reaction system to cause precipitation of the polythiophene derivative or its amine adduct, and then filtering the precipitate.

The weight average molecular weight of the polythiophene derivative or its amine adduct containing the repeating unit represented by formula (1) is preferably about 1,000 to 1,000,000, more preferably about 5,000 to 100,000, and even more preferably about 10,000 to about 50,000. By setting the weight average molecular weight at or above the lower limit, good electrical conductivity can be reproducibly obtained, and by setting it at or below the upper limit, solubility in solvents is improved. The weight average molecular weight is a polystyrene equivalent value measured by gel permeation chromatography.

The polythiophene derivative or its amine adduct contained in the charge transporting varnish of the present invention may be a polythiophene derivative having a repeating unit represented by formula (1) or an amine adduct thereof, either alone or in combination.
The polythiophene derivative containing the repeating unit represented by formula (1) may be a commercially available product or may be polymerized by a known method using a thiophene derivative or the like as a starting material, but in either case, it is preferable to use a product purified by a method such as reprecipitation or ion exchange. By using a purified product, the characteristics of an organic EL device having a thin film obtained from the charge transporting varnish of the present invention can be further improved.

Sulfonation of conjugated polymers and sulfonated conjugated polymers (including sulfonated polythiophenes) are described in U.S. Patent No. 8,017,241 to Seshadri et al. Sulfonated polythiophenes are described in WO 2008/073149 and WO 2016/171935.

In the present invention, at least a portion of the polythiophene derivative or its amine adduct containing a repeating unit represented by formula (1) contained in the charge transport varnish is dissolved in an organic solvent.

In the present invention, as the charge transport substance, a polythiophene derivative containing a repeating unit represented by formula (1) or its amine adduct may be used in combination with a charge transport substance consisting of another charge transport compound, but it is preferable that only a polythiophene derivative containing a repeating unit represented by formula (1) or its amine adduct is used.

The content of the charge transport substance in the charge transport varnish of the present invention is usually appropriately determined in the range of 0.05 to 40% by mass, preferably 0.1 to 35% by mass, of the solid content, taking into consideration the desired film thickness and the viscosity of the varnish, etc.

The charge-transporting varnish of the present invention contains surface-modified titanium oxide-containing particles. The titanium oxide contained in the particles may have any of the crystal structures of anatase type, rutile type, mixed anatase-rutile type, and brookite type. Among these, those containing the rutile type are preferred in consideration of the refractive index and transparency of the resulting thin film.

In the present invention, the titanium oxide-containing particles contained in the above-mentioned surface-modified titanium oxide-containing particles are preferably colloidal particles, and more preferably colloidal particles (D) (hereinafter referred to as surface-modified colloidal particles (D)) in which a titanium oxide-containing colloidal particle (A) serves as a nucleus (hereinafter referred to as core particle (A)), the surface of which is coated with a metal oxide colloidal particle (B) (hereinafter referred to as coating material (B)), and the surface of which is modified with an amphiphilic surface treatment agent.

The core particles (A) can be produced by known methods, such as ion exchange, peptization, hydrolysis, and reaction. Examples of ion exchange include a method of treating an acidic salt of Ti with a hydrogen-type ion exchange resin, or a method of treating a basic salt of Ti with a hydroxide-type anion exchange resin. Examples of peptization include a method of neutralizing the acidic salt of Ti with a base, or a method of washing the gel obtained by neutralizing the basic salt with an acid and then peptizing it with an acid or base. Examples of hydrolysis include a method of hydrolyzing an alkoxide of Ti, or a method of hydrolyzing the basic salt under heating and then removing unnecessary acid. Examples of reaction methods include a method of reacting Ti powder with an acid.

The core particles (A) may contain an oxide of a metal other than Ti, as long as the effect of the present invention is not impaired. Examples of such metal oxides include oxides of at least one metal selected from the group consisting of Al, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, In, Sn, Sb, Ba, Hf, Ta, W, Pb, Bi, and Ce. Among these metal oxides, tin oxide ( _SnO2 ) is preferred.

The content (metal oxide equivalent value) of metal oxides other than Ti in the core particles (A) is preferably 25% by mass or less, more preferably 20% by mass or less, in the metal oxide, taking into consideration the refractive index and transparency of the resulting thin film. The lower limit is not particularly limited and may be 0% by mass, but taking into consideration the ease of obtaining titanium oxide with a rutile structure, it is preferably 0.1% by mass or more, more preferably 5% by mass or more.

The core particle (A) can be synthesized, for example, according to the method described in International Publication No. 2013/081136.

The coating material (B) is a metal oxide colloid particle, but differs from the core particle (A) in that it does not contain titanium oxide ( _TiO2 ) as a metal oxide. However, in this case, "not containing titanium oxide ( _TiO2 )" does not deny the presence of titanium oxide that may be contained as an impurity, for example.
The metal oxide used in the coating (B) is preferably a colloidal particle of at least one metal oxide selected from the group consisting of Si, Al, Sn, Zr, Mo, Sb and W. The coating (B) may be, for example, in the form of a metal oxide, such as SiO ₂ , Al ₂ O ₃ , SnO ₂ , ZrO ₂ , MoO ₃ , Sb ₂ O ₅ , WO ₃ and the like. These metal oxides may be used alone or in combination. Examples of the combination method include a method of mixing several kinds of the above metal oxides, a method of compounding the above metal oxides, or a method of forming a solid solution of the above metal oxides at the atomic level.

For example, there may be mentioned SnO ₂ -WO ₃ composite colloid particles in which SnO ₂ particles and WO ₃ particles are composited by chemical bonding at their interfaces, SnO ₂ -SiO ₂ composite colloid particles in which SnO ₂ particles and SiO ₂ particles are composited by chemical bonding at their interfaces, SnO ₂ -WO 3 -SiO 2 composite colloid particles in which SnO ₂ particles, WO ₃ particles, and SiO ₂ particles are composited by chemical bonding at their interfaces, SnO ₂ -MoO _{3 -SiO 2} composite colloid particles in which SnO ₂ particles, MoO ₃ particles, and SiO ₂ particles are composited by chemical bonding at their interfaces, and Sb ₂ O ₅ -SiO ₂ composite colloid particles in which Sb ₂ O ₅ particles and SiO ₂ particles are composited _by chemical bonding at their interfaces.

When colloidal particles containing multiple types of metal oxides are used as the coating material (B), the proportions (mass ratios) of the metal oxides contained are not particularly limited. For example, in the case of _{SnO2 -SiO2 composite} colloidal particles, the mass ratio of _SiO2 / _SnO2 is preferably 0.1 to 5, and in the case of _Sb2O5 - _SiO2 composite colloidal particles, the mass ratio of _Sb2O5 / _SiO2 is preferably _0.1 to 5.

The coating (B) can be produced by known methods, such as the ion exchange method and the oxidation method. An example of the ion exchange method is a method in which an acid salt of the above metal is treated with a hydrogen ion exchange resin. An example of the oxidation method is a method in which a powder of the above metal or an oxide of the above metal is reacted with hydrogen peroxide.

The modified colloidal particles (C) can be obtained by mixing the core particles (A) and the coating material (B) in an appropriate ratio and heating for a predetermined time. The mixing ratio of the core particles (A) to the coating material (B) is preferably 0.05 to 0.5 in terms of mass ratio (B)/(A) (metal oxide equivalent).
The heating temperature when mixing the core particles (A) and the coating material (B) is usually 1 to 100° C., and preferably 20 to 60° C. The heating temperature after mixing is preferably 70 to 350° C., and more preferably 70 to 150° C. The heating time after mixing is usually 10 minutes to 5 hours, and preferably 30 minutes to 4 hours.

The modified colloidal particles (C) can usually be prepared as an aqueous dispersion, and the aqueous dispersion can be prepared, for example, according to the first and second methods described in WO 2017/170275.

The aqueous dispersion of the modified colloidal particles (C) may contain other optional components as long as the effects of the present invention are not impaired. In particular, by adding oxycarboxylic acids, the performance of the modified colloidal particles (C), such as dispersibility, can be further improved. Examples of the oxycarboxylic acids include lactic acid, tartaric acid, citric acid, gluconic acid, malic acid, and glycolic acid. The content of the oxycarboxylic acids is preferably about 30% by mass or less based on the total metal oxides of the modified colloidal particles (C).

The dispersion of modified colloidal particles (C) may also contain an alkaline component. Examples of the alkaline component include alkali metal hydroxides such as Li, Na, K, Rb, and Cs; primary to tertiary alkylamines such as ammonia, ethylamine, isopropylamine, n-propylamine, n-butylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, triethylamine, tripropylamine, tributylamine, triisobutylamine, triamylamine, tri-n-hexylamine, tri-n-octylamine, dimethylpropylamine, dimethylbutylamine, and dimethylhexylamine; aralkylamines such as benzylamine and dimethylbenzylamine; alicyclic amines such as piperidine; alkanolamines such as monoethanolamine and triethanolamine; and quaternary ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide. These may be used alone or in combination of two or more. The content of the alkaline component is preferably about 30% by mass or less based on the total metal oxides in the modified colloidal particles (C). Moreover, these alkaline components can be used in combination with the oxycarboxylic acid.

When the concentration of the aqueous dispersion of the modified colloidal particles (C) is to be further increased, it can be concentrated to a maximum of about 65% by mass by a conventional method. Examples of the method include evaporation and ultrafiltration. When the pH of the aqueous dispersion is to be adjusted, the above-mentioned alkali metal hydroxide, amine, quaternary ammonium salt, oxycarboxylic acid, etc. can be added.
In the present invention, the total metal oxide concentration in the solvent dispersion of the modified colloidal particles (C) is preferably from 10 to 60% by mass, more preferably from 20 to 50% by mass.

The aqueous dispersion of the modified colloidal particles (C) is obtained by replacing the aqueous medium with a hydrophilic organic solvent to obtain an organic solvent dispersion. This replacement can be carried out by a conventional method such as distillation or ultrafiltration. Examples of the hydrophilic organic solvent include lower alcohols such as methanol, ethanol, isopropanol, and 1-propanol, ethers such as propylene glycol monomethyl ether, linear amides such as dimethylformamide and N,N'-dimethylacetamide, cyclic amides such as N-methyl-2-pyrrolidone, and glycols such as ethyl cellosolve and ethylene glycol.

The surface-modified colloid particles (D) are preferably modified colloid particles (C) whose surfaces have been surface-modified with an amphiphilic surface treatment agent, more preferably modified colloid particles (C) whose surfaces have been surface-modified with an amphiphilic surface treatment agent having one or more hydrophilic groups selected from polyoxyethylene groups, polyoxypropylene groups, and polyoxybutylene groups, and one or more hydrophobic groups selected from alkylene groups or vinylene groups having 1 to 18 carbon atoms, and even more preferably modified colloid particles (C) whose surfaces have been surface-modified with an amphiphilic organosilicon compound having one or more hydrophilic groups selected from polyoxyethylene groups, polyoxypropylene groups, and polyoxybutylene groups, and one or more hydrophobic groups selected from alkylene groups or vinylene groups having 1 to 18 carbon atoms, bonded thereto.

Another preferred embodiment of the surface-modified titanium oxide-containing particles is, for example, a colloidal particle in which the surface of the core particle (A) is surface-modified with an amphiphilic surface treatment agent.

As the surface treatment agent, an amphiphilic surface treatment agent is preferred in consideration of improving the dispersibility of the particles in the varnish. In the present invention, for example, an organosilicon compound, a titanate coupling agent, an aluminate coupling agent, and a phosphorus-based surfactant can be suitably used as the amphiphilic surface treatment agent, and an organosilicon compound is more preferred. Furthermore, among these, an amphiphilic surface treatment agent having one or more hydrophilic groups selected from a polyoxyethylene group, a polyoxypropylene group, or a polyoxybutylene group, and having one or more hydrophobic groups selected from an alkylene group or a vinylene group having 1 to 18 carbon atoms is more preferred.

It is preferable that the above-mentioned hydrophilic groups, i.e., polyoxyethylene groups, polyoxypropylene groups or polyoxybutylene groups, are contained in an amount of 3 to 40 moles per molecule of the amphiphilic organosilicon compound.

The alkylene group having 1 to 18 carbon atoms may be linear, branched, or cyclic, and examples thereof include methylene, ethylene, n-propylene, isopropylene, cyclopropylene, n-butylene, isobutylene, s-butylene, t-butylene, cyclobutylene, 1-methylcyclopropylene, 2-methylcyclopropylene, n-pentylene, 1-methyl-n-butylene, 2-methyl-n-butylene, 3-methyl-n-butylene, 1,1-dimethyl-n-propylene, 1,2-dimethyl-n-propylene, 2,2-dimethyl-n-propylene, 1-ethyl-n-propylene, cyclopentylene, 1-methyl cyclobutylene, 2-methylcyclobutylene, 3-methylcyclobutylene, 1,2-dimethylcyclopropylene, 2,3-dimethylcyclopropylene, 1-ethylcyclopropylene, 2-ethylcyclopropylene, n-hexylene, 1-methyl-n-pentylene, 2-methyl-n-pentylene, 3-methyl-n-pentylene, 4-methyl-n-pentylene, 1,1-dimethyl-n-butylene, 1,2-dimethyl-n-butylene, 1,3-dimethyl-n-butylene, 2,2-dimethyl-n-butylene, 2,3-dimethyl-n-butylene, 3,3-dimethyl-n-butylene, 1-ethyl-n -butylene group, 2-ethyl-n-butylene group, 1,1,2-trimethyl-n-propylene group, 1,2,2-trimethyl-n-propylene group, 1-ethyl-1-methyl-n-propylene group, 1-ethyl-2-methyl-n-propylene group, n-heptylene group, n-octylene group, n-nonylene group, cyclohexylene group, 1-methyl-cyclopentylene group, 2-methyl-cyclopentylene group, 3-methyl-cyclopentylene group, 1-ethyl-cyclobutylene group, 2-ethyl-cyclobutylene group, 3-ethyl-cyclobutylene group, 1,2-dimethyl-cyclobutylene group, 1,3-dimethyl-cyclobutylene group, 2,2-dimethyl-cyclobutylene group, 2, Examples of such cyclopropylene groups include 3-dimethyl-cyclobutylene, 2,4-dimethyl-cyclobutylene, 3,3-dimethyl-cyclobutylene, 1-n-propyl-cyclopropylene, 2-n-propyl-cyclopropylene, 1-isopropyl-cyclopropylene, 2-isopropyl-cyclopropylene, 1,2,2-trimethyl-cyclopropylene, 1,2,3-trimethyl-cyclopropylene, 2,2,3-trimethyl-cyclopropylene, 1-ethyl-2-methyl-cyclopropylene, 2-ethyl-1-methyl-cyclopropylene, 2-ethyl-2-methyl-cyclopropylene and 2-ethyl-3-methyl-cyclopropylene groups.

Examples of amphiphilic organosilicon compounds include methoxytriethyleneoxypropyl trimethoxysilane, methoxytriethyleneoxyoctyl trimethoxysilane, methoxytriethyleneoxypropyl triethoxysilane, methoxytriethyleneoxypropyl tripropoxysilane, methoxytriethyleneoxypropyl triacetoxysilane, methoxytripropyleneoxypropyl trimethoxysilane, methoxytripropyleneoxyoctyl trimethoxysilane, methoxytripropyleneoxypropyl triethoxysilane, methoxytripropyleneoxypropyl tripropoxysilane, methoxytripropyleneoxypropyl triacetoxysilane, methoxytributyleneoxypropyl trimethoxysilane, methoxytributyleneoxyoctyl trimethoxysilane, methoxytributyleneoxypropyl triethoxysilane, methoxytributyleneoxypropyl tripropoxysilane, methoxytripropyleneoxypropyl triacetoxysilane, methoxytributyleneoxypropyl trimethoxysilane, methoxytributyleneoxyoctyl trimethoxysilane, methoxytributyleneoxypropyl triethoxysilane, methoxytributyleneoxypropyl tripropoxy Silane, methoxytribuyleneoxypropyl triacetoxysilane, methoxytriethylenepropyl dimethoxymethylsilane, methoxytripropyleneoxydimethoxymethylsilane, methoxytribuyleneoxydimethoxymethylsilane, methoxytriethylenepropyl diethoxymethylsilane, methoxytripropyleneoxydiethoxymethylsilane, methoxytribuyleneoxydiethoxymethylsilane, methoxytriethylenepropyl dimethyl methoxysilane, methoxytripropylenepropyl dimethyl methoxysilane, methoxytribuylenepropyl dimethyl methoxysilane, methoxytriethylenepropyl dimethyl ethoxysilane, methoxytripropylenepropyl dimethyl ethoxysilane, methoxytribuylenepropyl dimethyl ethoxysilane, bis-(methoxytriethylenepropyl)dimethoxysilane, bis-(methoxytripropylenepropyl)dimethoxysilane, bis- (Methoxytributylenepropyl)dimethoxysilane, [methoxy(polyethyleneoxy)npropyl]trimethoxysilane, [methoxy(polyethyleneoxy)npropyl]triethoxysilane, [methoxy(polyethyleneoxy)npropyl]tripropoxysilane, [methoxy(polyethyleneoxy)npropyl]triacetoxysilane, [methoxy(polypropyleneoxy)npropyl]trimethoxysilane, [methoxy(polypropyleneoxy)npropyl]triethoxysilane, [methoxy(polypropyleneoxy)npropyl]tripropoxysilane, "methoxy(polypropyleneoxy)npropyl"triacetoxysilane, [methoxy(polybutyleneoxy)npropyl]trimethoxysilane, [methoxy(polybutyleneoxy)npropyl]tripropoxysilane, [methoxy(polybutyleneoxy)npropyl]triacetoxysilane, [methoxy(polyethyleneoxy)npropyl propyl]dimethoxymethylsilane, [methoxy(polyethyleneoxy)n propyl]diethoxymethylsilane, [methoxy(polyethyleneoxy)n propyl]dipropoxymethylsilane, [methoxy(polyethyleneoxy)n propyl]diacetoxymethylsilane, [methoxy(polypropyleneoxy)n propyl]dimethoxymethylsilane, [methoxy(polypropyleneoxy)n propyl]diethoxymethylsilane, [methoxy(polypropyleneoxy)n propyl]dipropoxymethylsilane, [methoxy(polypropyleneoxy)n propyl]diacetoxymethylsilane, [methoxy(polybutyleneoxy)n propyl]dimethoxymethylsilane, [methoxy(polybutyleneoxy)n propyl]diethoxymethylsilane, [methoxy(polybutyleneoxy)n propyl]dipropoxymethylsilane, [methoxy(polybutyleneoxy)n propyl]diacetoxymethylsilane.

Specific examples of amphiphilic titanate coupling agents and amphiphilic aluminate coupling agents include PLENACT manufactured by Ajinomoto Fine-Techno Co., Ltd., and specific examples of amphiphilic phosphorus-based surfactants include Disperbyk manufactured by BYK-Chemie and Phosphanol manufactured by Toho Chemical Industry Co., Ltd., but are not limited to these.

The amount of amphiphilic surface modifier bound to the surface of the modified colloidal particles (C) is preferably 0.1 to 30 mass %, more preferably 1 to 15 mass %, and even more preferably 1 to 10 mass %, relative to the total metal oxide of the modified colloidal particles (C).

In the present invention, for example, the surface-modified colloid particles (D) can be obtained by adding a predetermined amount of the above-mentioned amphiphilic surface modifier having a hydrolyzable group to an aqueous dispersion or a hydrophilic organic solvent dispersion of the modified colloid particles (C), hydrolyzing the surface modifier with a catalyst such as dilute hydrochloric acid, and bonding it to the surface of the modified colloid particles (C).

The aqueous dispersion or hydrophilic organic solvent dispersion of the surface-modified titanium oxide-containing particles of the present invention can be further replaced with a hydrophobic organic solvent. This replacement method can be performed by a conventional method such as distillation or ultrafiltration. Examples of hydrophobic solvents include ketones such as methyl ethyl ketone and methyl isobutyl ketone, cyclic ketones such as cyclopentanone and cyclohexanone, and esters such as ethyl acetate and butyl acetate.

The organic solvent dispersion of the surface-modified titanium oxide-containing particles of the present invention may contain other optional components within a range that does not impair the effects of the present invention. In particular, by adding phosphoric acid, phosphoric acid derivatives, phosphoric acid surfactants, oxycarboxylic acids, etc., the dispersibility of the surface-modified titanium oxide-containing particles can be further improved. Examples of phosphoric acid derivatives include phenylphosphonic acid and its metal salts. Examples of phosphoric acid surfactants include Disperbyk (manufactured by BYK-Chemie), Phosphanol (manufactured by Toho Chemical Industry Co., Ltd.), and Nikkol (manufactured by Nikko Chemicals Co., Ltd.). Examples of oxycarboxylic acids include lactic acid, tartaric acid, citric acid, gluconic acid, malic acid, and glycolic acid. The content of these optional components is preferably about 30% by mass or less based on the total metal oxide of the surface-modified titanium oxide-containing particles.

The total metal oxide concentration of the organic solvent dispersion of the above surface-modified titanium oxide-containing particles is preferably 10 to 60 mass%, more preferably 30 to 50 mass%, taking into consideration the dispersion stability of the surface-modified titanium oxide-containing particles.

The primary particle diameters of the core particles (A), the coating material (B), the modified colloidal particles (C) and the surface-modified colloidal particles (D) are preferably within the following ranges, taking into consideration the dispersion stability, and the refractive index and transparency of the resulting thin film.
The primary particle size of the core particles (A) is preferably from 1 to 60 nm, more preferably from 2 to 30 nm, and even more preferably from 2 to 20 nm.
The primary particle size of the coating (B) is preferably 5 nm or less, more preferably 1 to 5 nm, and even more preferably 1 to 4 nm.
The primary particle size of the modified colloidal particles (C) is preferably from 2 to 100 nm.
The primary particle size of the surface-modified colloidal particles (D) is preferably from 2 to 100 nm, more preferably from 5 to 50 nm, and even more preferably from 5 to 20 nm.
In the present invention, the primary particle size can be measured by observation using a transmission electron microscope.

It is preferable that the surface-modified titanium oxide-containing particles contained in the charge-transporting varnish of the present invention are uniformly dispersed in the varnish.

In the charge-transporting varnish of the present invention, the content of the surface-modified titanium oxide-containing particles is not particularly limited, but from the viewpoints of suppressing particle aggregation in the charge-transporting material and obtaining a thin film with good reproducibility and excellent flatness, it is preferably 30 to 65 mass % of the solid content, more preferably 40 to 60 mass %, and most preferably 50 to 60 mass %.

The charge-transporting varnish of the present invention contains an organic solvent. There are no particular limitations on the organic solvent as long as it disperses or dissolves components other than the organic solvent used in the charge-transporting varnish of the present invention. Specific examples of such solvents include aromatic or halogenated aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and chlorobenzene; aliphatic hydrocarbons such as n-heptane, n-hexane, and cyclohexane; ether solvents such as diethyl ether, tetrahydrofuran, dioxane, and 1,2-dimethoxyethane; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate, normal hexyl acetate, ethyl lactate, γ-butyrolactone, propylene carbonate, and diisopropyl malonate; halogenated hydrocarbon solvents such as methylene chloride, dichloromethane, 1,2-dichloroethane, and chloroform; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone; alcohol solvents such as methanol, ethanol, isopropanol, n-propanol, cyclohexanol, diacetone alcohol, and 2-benzooxyethanol; The solvent may be appropriately selected from glycol ether solvents such as glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol diglycidyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate; and glycol solvents such as ethylene glycol, propylene glycol, hexylene glycol, 1,3-octylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, and 1,4-butanediol.
These organic solvents may be used alone or in combination of two or more.

The charge transport varnish of the present invention may contain water as a solvent, but from the viewpoint of reproducibly obtaining an organic EL element having excellent durability, the water content is preferably 10% by mass or less of the total solvent, more preferably 5% by mass or less, and it is optimal to use only an organic solvent as the solvent. In this case, "only organic solvent" means that only an organic solvent is used as the solvent, and does not deny the presence of "water" contained in trace amounts in the organic solvent or solid content used.

The charge transport varnish of the present invention preferably contains a heteropolyacid from the viewpoint of realizing a low driving voltage when used as a hole injection layer of an organic EL element. A heteropolyacid is a polyacid formed by condensing an isopolyacid, which is an oxyacid of vanadium (V), molybdenum (Mo), tungsten (W), etc., with an oxyacid of a different element, and has 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 (A) or a Dawson type chemical structure represented by formula (B). Such oxyacids of different elements mainly include oxyacids of silicon (Si), phosphorus (P), and arsenic (As).

Specific examples of heteropolyacids include phosphomolybdic acid, silicomolybdic acid, phosphotungstic acid, silicotungstic acid, phosphotungstomolybdic acid, etc., which may be used alone or in combination of two or more. The heteropolyacids used in the present invention are commercially available, or may be synthesized by known methods.
In particular, when only one type of heteropolyacid is contained, the one type of heteropolyacid preferably contains tungsten, i.e., phosphotungstic acid, silicotungstic acid, phosphotungstomolybdic acid, etc. are preferred, and phosphotungstic acid and silicotungstic acid are more preferred.

In addition, even if a heteropolyacid has a large or small number of elements in the structure represented by the general formula in a quantitative analysis such as elemental analysis, it can be used in the present invention as long as it is available as a commercial product or appropriately synthesized according to a known synthesis method.
That is, for example, phosphotungstic acid is generally represented by the chemical formula _H3 ( _PW12O40 ) _nH2O , _but even if the number of P (phosphorus), O (oxygen) or W (tungsten) in this formula is large or small in quantitative analysis, it can be used in the present invention as long as it is obtained as a commercial product or appropriately synthesized according to a known synthesis method. In this case, the mass of the heteropolyacid specified in the present invention does not mean the mass of pure phosphotungstic acid (phosphotungstic acid content) in a synthesized product or a commercial product, but the total mass including water of hydration and other impurities in a form available as a commercial product or in a form that can be isolated by a known synthesis method.

When the charge-transporting varnish of the present invention contains a heteropolyacid, the content thereof is set to a mass ratio of about 1.0 to 11.0 per 1 unit of charge-transporting substance, preferably about 1.1 to 10.0, more preferably about 1.2 to 9.5, even more preferably about 1.3 to 9.0, and even more preferably about 1.4 to 8.5, so that a charge-transporting thin film that provides high brightness when used in an organic EL element can be reproducibly obtained.

The charge-transporting varnish of the present invention may contain a dopant substance for the purpose of improving the charge transporting ability, etc., depending on the application of the thin film obtained. There are no particular limitations on the dopant substance, so long as it dissolves in at least one solvent used in the varnish, and both inorganic and organic dopant substances can be used.

Inorganic dopant substances include strong inorganic acids such as hydrogen chloride, sulfuric acid, nitric acid, and phosphoric acid; metal halides such as aluminum (III) chloride ( _AlCl3 ), titanium (IV) tetrachloride ( _TiCl4 ), boron tribromide ( _BBr3 ), boron _trifluoride ether complex ( _BF3.OEt2 ), iron (III) chloride ( _FeCl3 ), copper (II) chloride ( _CuCl2 ), antimony (V) pentachloride ( _SbCl5 ), arsenic (V) pentafluoride ( _AsF5 ), and phosphorus pentafluoride ( _PF5 ); and halogens such as _Cl2 , _Br2 , _I2 , ICl, _ICl3 , IBr, and _IF4 .

In addition, examples of organic dopant substances include tetracyanoquinodimethanes such as 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 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, halotetracyanoquinodimethanes (haloTCNQs) such as quinodimethane and 2,5-dichloro-7,7,8,8-tetracyanoquinodimethane; benzoquinone derivatives such as tetrachloro-1,4-benzoquinone (chloranil) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ); 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, xylbenzenesulfonic 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-naphthalenesulfonic acid, hexylnaphthalenesulfonic acid, 7-hexyl-1-naphthalenesulfonic acid, 6-hexyl-2-naphthalenesulfonic acid, dinonylnaphthalenesulfonic acid, 2,7-dinonyl-4-naphthalenesulfonic acid Examples of the sulfonic acid include aryl sulfonic acid compounds such as phthalenesulfonic acid, dinonylnaphthalene disulfonic acid, 2,7-dinonyl-4,5-naphthalene disulfonic acid, 1,4-benzodioxane disulfonic acid derivatives described in WO 2005/000832, aryl sulfonic acid derivatives described in WO 2006/025342, and dinonylnaphthalenesulfonic acid derivatives described in JP-A 2005-108828; aromatic sulfone compounds such as polystyrene sulfonic acid; and non-aromatic sulfone compounds such as 10-camphorsulfonic acid.
These inorganic and organic dopant substances may be used alone or in combination of two or more.

Examples of arylsulfonic acid compounds preferred as dopant substances in the present invention include arylsulfonic acid compounds represented by formula (H1) or (H2).

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

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

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

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

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

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

When an organic compound is used as a dopant substance, the molecular weight thereof is preferably 3,000 or less, more preferably 2,500 or less, taking into consideration the solubility in organic solvents.
In particular, the molecular weight of the arylsulfonic acid compound used as the dopant material is not particularly limited, but is preferably 2,000 or less, more preferably 1,500 or less, taking into consideration the solubility in organic solvents.

Examples of arylsulfonic acid compounds that can be suitably used in the present invention include, but are not limited to, the following compounds:

When the charge-transporting varnish of the present invention contains a dopant substance, its content is appropriately set taking into consideration the type and amount of the charge-transporting substance, but is usually about 0.1 to 10 parts by mass per 1 part of the charge-transporting substance.

The charge transporting varnish of the present invention may contain an amine compound for the purpose of improving the dispersibility or solubility of the polythiophene derivative or its amine adduct.
Such an amine compound is not particularly limited as long as it is soluble in at least one solvent used in the varnish, and one type may be used alone, or two or more types may be used.

Specific examples of primary amine compounds include methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, s-butylamine, t-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, and n-hexadecylamine. Examples of monoalkylamine compounds include decylamine, n-heptadecylamine, n-octadecylamine, n-nonadecylamine, and n-eicosanylamine; and monoarylamine compounds such as aniline, tolylamine, 1-naphthylamine, 2-naphthylamine, 1-anthrylamine, 2-anthrylamine, 9-anthrylamine, 1-phenanthrylamine, 2-phenanthrylamine, 3-phenanthrylamine, 4-phenanthrylamine, and 9-phenanthrylamine.

Specific examples of secondary amine compounds include N-ethylmethylamine, N-methyl-n-propylamine, N-methylisopropylamine, N-methyl-n-butylamine, N-methyl-s-butylamine, N-methyl-t-butylamine, N-methylisobutylamine, diethylamine, N-ethyl-n-propylamine, N-ethylisopropylamine, N-ethyl-n-butylamine, N-ethyl-s-butylamine, N-ethyl-t-butylamine, dipropylamine, N-n-propylisopropylamine, and N-n-propyl N-n-butylamine, N-n-propyl-s-butylamine, diisopropylamine, N-n-butylisopropylamine, N-t-butylisopropylamine, di(n-butyl)amine, di(s-butyl)amine, diisobutylamine, aziridine (ethyleneimine), 2-methylaziridine (propyleneimine), 2,2-dimethylaziridine, azetidine (trimethyleneimine), 2-methylazetidine, pyrrolidine, 2-methylpyrrolidine, 3-methylpyrrolidine, 2,5-dimethylpyrrolidine, piperidine, 2,6-di Dialkylamine compounds such as methylpiperidine, 3,5-dimethylpiperidine, 2,2,6,6-tetramethylpiperidine, hexamethyleneimine, heptamethyleneimine, and octamethyleneimine; diphenylamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, 1,1'-dinaphthylamine, 2,2'-dinaphthylamine, 1,2'-dinaphthylamine, carbazole, 7H-benzo[c]carbazole, 11H-benzo[a]carbazole, 7H-dibenzo[c,g]carbazole, 13H-di Examples of the alkyl amine compounds include diarylamine compounds such as benzo[a,i]carbazole; and alkylarylamine compounds such as N-methylaniline, N-ethylaniline, N-n-propylaniline, N-isopropylaniline, N-n-butylaniline, N-s-butylaniline, N-isobutylaniline, N-methyl-1-naphthylamine, N-ethyl-1-naphthylamine, N-n-propyl-1-naphthylamine, indoline, isoindoline, 1,2,3,4-tetrahydroquinoline, and 1,2,3,4-tetrahydroisoquinoline.

Specific examples of tertiary amine compounds include N,N-dimethylethylamine, N,N-dimethyl-n-propylamine, N,N-dimethylisopropylamine, N,N-dimethyl-n-butylamine, N,N-dimethyl-s-butylamine, N,N-dimethyl-t-butylamine, N,N-dimethylisobutylamine, N,N-diethylmethylamine, N-methyldi(n-propyl)amine, N-methyldiisopropylamine, N-methyldi(n-butyl)amine, N-methyldiisobutylamine, triethylamine, N,N-diethyl-n-butylamine, N,N-diisopropylethylamine, and N,N-di(n-butyl)ethylamine. trialkylamine compounds such as tri(n-propyl)amine, tri(i-propyl)amine, tri(n-butyl)amine, tri(i-butyl)amine, 1-methylacetidine, 1-methylpyrrolidine, and 1-methylpiperidine; triarylamine compounds such as triphenylamine; alkyldiarylamine compounds such as N-methyldiphenylamine, N-ethyldiphenylamine, 9-methylcarbazole, and 9-ethylcarbazole; and dialkylarylamine compounds such as N,N-diethylaniline, N,N-di(n-propyl)aniline, N,N-di(i-propyl)aniline, and N,N-di(n-butyl)aniline.

In particular, when the charge-transporting varnish of the present invention contains an amine compound, the amine compound has an excellent ability to improve the dispersibility and solubility of the polythiophene derivative or its amine adduct used in the present invention, and therefore it is preferable that the amine compound contains a primary amine compound, and it is preferable that the amine compound contains a monoalkylamine, particularly a monoalkylamine having 2 to 20 carbon atoms.

When the charge-transporting varnish of the present invention contains an amine compound, the content thereof is usually 200% by mass or less relative to the polythiophene derivative or its amine adduct used in the present invention, and preferably 50% by mass or more in order to obtain the above-mentioned effects of the amine compound.

The charge-transporting varnish of the present invention may contain a known organosilane compound. By including such an organosilane compound in the charge-transporting varnish, when the charge-transporting thin film obtained from the varnish is used as a hole-injection layer of an organic EL device, the hole-injection property into the hole-transporting layer provided in contact with the charge-transporting thin film can be improved.
As the organic silane compound, alkoxysilane is preferable, and trialkoxysilane and tetraalkoxysilane are more preferable. As the alkoxysilane, tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, etc. can be mentioned. Among these, TEOS (tetraethoxysilane), tetramethoxysilane, and tetraisopropoxysilane can be preferably used in the present invention. These organic silane compounds can be used alone or in combination of two or more.

When the charge-transporting varnish of the present invention contains an organic silane compound, its content is usually about 0.1 to 50 mass% of the solids, but taking into consideration the balance between improving the flatness of the resulting thin film and suppressing a decrease in charge transport properties, the content is preferably about 0.5 to 40 mass%, more preferably about 0.8 to 30 mass%, and even more preferably about 1 to 20 mass%.

The viscosity of the charge-transporting varnish of the present invention is typically 1 to 50 mPa·s at 25° C., and the surface tension is typically 20 to 50 mN/m at 25° C. The viscosity and surface tension of the charge-transporting varnish of the present invention can be adjusted by changing the types of organic solvents used, their ratios, solids concentration, etc., taking into consideration various factors such as the coating method used and the desired film thickness.

In addition, the solids concentration of the charge-transporting varnish in the present invention is appropriately set taking into consideration the viscosity and surface tension of the varnish and the thickness of the thin film to be produced, but is usually about 0.1 to 15% by mass, and from the viewpoint of suppressing aggregation of the charge-transporting substance and surface-modified titanium oxide-containing particles in the varnish, it is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less.

The charge transport varnish of the present invention can be produced by mixing a charge transporting material, surface-modified titanium oxide-containing particles, an organic solvent, and other components as necessary. The order of mixing is not particularly limited, but examples of a method for easily and reproducibly producing the charge transporting varnish of the present invention include a method of dissolving a charge transporting material in an organic solvent, and adding other components or their solutions prepared in advance and an aqueous dispersion or organic solvent dispersion of surface-modified titanium oxide-containing particles to the solution, and a method of adding a solution of a charge transporting material and other components or their solutions to an aqueous dispersion or organic solvent dispersion of surface-modified titanium oxide-containing particles. In this case, if necessary, an additional organic solvent may be added at the end, or some components that are relatively soluble in the solvent may be added at the end without being included in the mixture, but from the viewpoint of suppressing aggregation and separation of the components and reproducibly preparing a charge transporting varnish with excellent uniformity, it is preferable to separately prepare a mixture containing an aqueous dispersion or organic solvent dispersion of surface-modified titanium oxide-containing particles in a well-dispersed state and other components, mix the two, and then stir well. It should be noted that the charge transporting material and the surface-modified titanium oxide-containing particles may aggregate or precipitate when mixed depending on the type and amount of the solvent they are mixed in. It should also be noted that when preparing a varnish using the above-mentioned surface-modified colloidal particles (D), it is necessary to determine the concentration and amount of the surface-modified colloidal particles (D) used so that the metal oxide in the final varnish is in the desired amount.
In preparing the varnish, heating may be carried out appropriately within a range in which the components are not decomposed or deteriorated.

In the present invention, the charge-transporting varnish may be filtered using a sub-micrometer filter during the course of producing the varnish or after all of the components have been mixed, in order to reproducibly obtain a thin film with higher flatness.

By applying the charge-transporting varnish described above onto a substrate and baking it, a charge-transporting thin film can be formed on the substrate.

The method for applying the varnish is not particularly limited, and examples include dipping, spin coating, transfer printing, roll coating, brushing, inkjet, spraying, and slit coating. It is preferable to adjust the viscosity and surface tension of the varnish depending on the application method.

In addition, when the charge transport varnish of the present invention is used, the baking atmosphere is not particularly limited, and a thin film having a uniform film surface and high charge transportability can be obtained not only in the air atmosphere but also in an inert gas such as nitrogen or in a vacuum. The baking temperature is appropriately set within the range of about 100 to 260°C, taking into consideration the use of the obtained thin film, the degree of charge transportability to be imparted to the obtained thin film, the type and boiling point of the solvent, etc., but when the obtained thin film is used as a hole injection layer of an organic EL device, about 140 to 250°C is preferable, and about 145 to 240°C is more preferable. In addition, during baking, two or more stages of temperature change may be applied for the purpose of expressing a more uniform film formation property or proceeding with a reaction on the substrate, and heating may be performed using an appropriate device such as a hot plate or oven.

There are no particular limitations on the thickness of the charge transport thin film, but when used as a hole injection layer, hole transport layer, or hole injection transport layer of an organic EL element, 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 typically exhibits a refractive index (n) of 1.50 or more and an extinction coefficient (k) of 0.500 or less, averaged over the wavelength region of 400 to 800 nm, but in some embodiments exhibits a refractive index (n) of 1.60 or more, in some other embodiments exhibits a refractive index (n) of 1.70 or more, and in some other embodiments exhibits a refractive index (n) of 1.75 or more, and in some embodiments exhibits an extinction coefficient (k) of 0.100 or less, in some other embodiments exhibits an extinction coefficient (k) of 0.070 or less, and in some other embodiments exhibits an extinction coefficient (k) of 0.050 or less.

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

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

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

When producing an EL element using the charge transport varnish of the present invention, the materials used and the production method include, but are not limited to, the following:

An example of a method for producing an OLED element having a hole injection layer made of a thin film obtained from the charge transport varnish of the present invention is as follows. It is preferable to previously perform a surface treatment on the electrodes, such as cleaning with alcohol, pure water, or the like, or a UV ozone treatment or oxygen plasma treatment, within a range that does not adversely affect the electrodes.
A hole injection layer is formed on an anode substrate by the above-mentioned method using the charge transport varnish. This is introduced into a vacuum deposition apparatus, and a hole transport layer, a light emitting layer, an electron transport layer/hole blocking layer, an electron injection 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), metals such as aluminum, and metal anodes made of alloys thereof, and it is preferable to use those that have been subjected to planarization treatment. Polythiophene derivatives and polyaniline derivatives having high charge transport properties can also be used.
Other metals constituting the metal anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.

Materials 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 into a polymer compound such as poly(p-phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly(3-alkylthiophene), or polyvinylcarbazole.
In addition, when forming a light-emitting layer by vapor deposition, it may be co-deposited with a light-emitting dopant. Examples of the light-emitting dopant include, but are _not limited to, metal complexes such as tris(2-phenylpyridine)iridium(III) (Ir(ppy)), naphthacene derivatives such as rubrene, quinacridone derivatives, and condensed polycyclic aromatic rings such as perylene.

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

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

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

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

The materials constituting the anode, cathode and layers formed therebetween differ depending on whether an element having a bottom emission structure or a top emission structure is manufactured, and therefore, the materials are appropriately selected taking this into consideration.
Typically, in an element with a bottom emission structure, a transparent anode is used on the substrate side and light is extracted from the substrate side, whereas in an element with a top emission structure, a reflective anode made of metal is used and light is extracted from the transparent electrode (cathode) side opposite the substrate. Therefore, for example, in terms of anode material, when manufacturing an element with a bottom emission structure, a transparent anode such as ITO is used, and when manufacturing an element with a top emission structure, a reflective anode such as Al/Nd is used.

In order to prevent deterioration of the characteristics of the organic EL element of the present invention, it may be sealed, if necessary, with a moisture scavenger or the like, in accordance with standard procedures.

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

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The methods for measuring physical properties and the devices used are as follows.

[Measurement of physical properties of surface-modified titanium oxide-containing particles]
(1) Water content: Measured by Karl Fischer titration.
(2) Primary particle size: The dispersion was dried on a copper mesh and observed under a transmission electron microscope to measure the sizes of 100 particles, and the average value was calculated as the primary particle size.
(3) Specific gravity: Measured by a float balance method (50°C).
(4) Viscosity: Measured with an Ostwald viscometer (50° C.).
(5) Particle size measured by dynamic light scattering: measured using a Zetasizer Nano manufactured by Malvern.
(6) Solid content: Measured from the residual solid matter after firing at 600° C.
(7) Amount of organosilane compound bound: The amount of organosilane compound bound to the modified metal oxide colloidal particles was determined by elemental analysis.
Apparatus: PerkinElmer, Series II CHNS/O Analyzer 2400

[Preparation and Evaluation of Charge-Transporting Varnish]
(1) Substrate cleaning: Substrate cleaning equipment (low pressure plasma method) manufactured by Choshu Sangyo Co., Ltd.
(2) Coating of varnish: Spin coater MS-A100, manufactured by Mikasa Co., Ltd.
(3) Film thickness measurement: Microscopic shape measuring instrument Surfcorder ET-4000, manufactured by Kosaka Laboratory Co., Ltd.
(4) Measurement of optical properties of film: J. A. Woollam Co., Ltd., multi-angle rotating compensator type high-speed spectroscopic ellipsometer M-2000UI
(5) Preparation of EL element: Multi-function deposition system C-E2L1G1-N manufactured by Choshu Sangyo Co., Ltd.
(6) Measurement of luminance of EL elements: IVL measurement system manufactured by Tech World Co., Ltd.

[1] Production of surface-modified titanium oxide-containing colloidal particles [Production Example 1-1] Production of core particles (A) 126.2 g of pure water was placed in a 1-liter container, and 17.8 g of metastannic acid (containing 15 g in terms of SnO ₂ , manufactured by Showa Kako Co., Ltd.), 284 g of titanium tetraisopropoxide (containing 80 g in terms of TiO ₂ , manufactured by Nippon Soda Co., Ltd. A-1), 98 g of oxalic acid dihydrate (containing 70 g in terms of oxalic acid , manufactured by Ube Industries, Ltd.), and 438 g of 35% by mass tetraethylammonium hydroxide aqueous solution (manufactured by Seychem Japan) were added under stirring. The resulting mixed solution had a molar ratio of oxalic acid/titanium atom of 0.78 and a molar ratio of tetraethylammonium hydroxide/titanium atom of 1.04. 950 g of the mixed solution was kept at 80° C. for 2 hours, and further reduced to 580 Torr and kept for 2 hours to prepare a titanium mixed solution. The prepared titanium mixed solution had a pH of 4.7, an electrical conductivity of 27.2 mS/cm, and a metal oxide concentration of 10.0% by mass. 950 g of the titanium mixed solution and 950 g of pure water were charged into a 3-liter glass-lined autoclave vessel, and hydrothermal treatment was performed at 140°C for 5 hours. After cooling to room temperature, the solution after hydrothermal treatment was taken out and was a pale milky white aqueous dispersion of titanium oxide-containing colloidal particles. The obtained dispersion had a pH of 3.9, an electrical conductivity of 19.7 mS/cm, a _TiO2 concentration of 4.2% by mass, a tetraethylammonium hydroxide concentration of 8.0% by mass, an oxalic acid concentration of 3.7% by mass, a dynamic light scattering particle diameter of 16 nm, and elliptical particles with a primary particle diameter of 5 to 15 nm were observed by transmission electron microscopy. The obtained dispersion was dried at 110°C, and the powder was subjected to X-ray diffraction analysis, and it was confirmed that the particles were rutile crystals. The obtained titanium oxide-containing colloidal particles were designated as core particles (A).

[Production Example 1-2] Production of coating material (B) 27.9 g of sodium silicate aqueous solution (JIS No. 3 sodium silicate, containing 34% by mass as _SiO2 , manufactured by Fuji Chemical Co., Ltd.) was diluted with 27.9 g of pure water, and then 8.6 g of sodium stannate trihydrate (containing 55% by mass as _SnO2 , manufactured by Showa Kako Co., Ltd.) was added and dissolved under stirring to obtain a silicate-sodium stannate aqueous solution. 64.4 g of the obtained silicate-sodium stannate aqueous solution was diluted with 411 g of pure water and passed through a column filled with a hydrogen cation exchange resin (Amberlite (registered trademark) IR-120B) to obtain 570 g of an aqueous dispersion of silicon dioxide-tin dioxide composite oxide colloidal particles (pH 2.7, containing 0.83% by mass as _SnO2 and 1.67% by mass as _SiO2 , _SiO2 / _SnO2 mass ratio 2.0).

Next, 2.9 g of diisopropylamine was added to the obtained aqueous dispersion of silicon dioxide-tin dioxide composite oxide colloidal particles. The obtained dispersion was an aqueous dispersion of alkaline silicon dioxide-tin dioxide composite oxide colloidal particles, with a pH of 8.2 and colloidal particles with a primary particle diameter of 5 nm or less. The obtained alkaline silicon dioxide-tin dioxide composite oxide colloidal particles were used as coating material (B).

[Production Example 1-3] Production of modified colloidal particles (C) 570 g of the above-mentioned coating material (B) was added to 1,900 g of the aqueous dispersion of the above-mentioned core particles (A) at 25° C. under stirring, and then the mixture was held at a temperature of 95° C. for 3 hours to obtain an aqueous dispersion of modified colloidal particles (C). The aqueous dispersion obtained was then passed through a column filled with a hydrogen cation exchange resin (Amberlite IR-120B) to obtain 2,730 g of an aqueous dispersion of acidic modified titanium oxide composite colloidal particles. The resulting dispersion had a pH of 2.7, a total metal oxide concentration of 4.0 mass%, and a mass ratio (metal oxide equivalent value) represented by (B)/(A) of 0.15. 2.2 g of diisobutylamine was added to the resulting dispersion. The pH of the resulting dispersion was 4.5. Next, this dispersion was placed in an evaporator equipped with a pear-shaped flask to concentrate it, and water was distilled off at 600 Torr while adding methanol to obtain 533 g of a methanol dispersion of modified colloidal particles (C). The resulting methanol dispersion had a specific gravity of 0.949, a viscosity of 1.2 mPa·s, a pH of 4.8 (diluted with the same mass of water as the dispersion), a total metal oxide concentration of 20.5 mass %, and a water content of 3.1 mass %.

[Production Example 1-4] Production of Surface-Modified Colloid Particles (D) 5.5 g of polyether-modified silane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: X-12-641) was added to 533 g of the methanol dispersion of the modified colloid particles (C) obtained in Production Example 1-3, and reflux heating was performed at 70° C. for 5 hours to obtain a methanol dispersion of modified colloid particles (C) having polyether groups bonded to the surface. Next, using an evaporator, methanol was distilled off while adding propylene glycol monomethyl ether at 80 Torr to replace the methanol with propylene glycol monomethyl ether, and 270 g of a propylene glycol monomethyl ether dispersion of surface-modified colloid particles (D) having polyether-modified silane bonded to the surface (hereinafter referred to as dispersion X) was obtained. The obtained dispersion X had a specific gravity of 1.353, a viscosity of 7.0 mPa·s, a total metal oxide concentration of 40.3 mass%, a primary particle diameter of 5 to 10 nm as determined by transmission electron microscopy, and a particle diameter of 9 nm as determined by dynamic light scattering. In the obtained surface-modified colloidal particles (D), the amount of the polyether-modified silane bonded to the surface of the modified colloidal particles (C) was 4.0 mass % based on the total metal oxides of the modified colloidal particles (C).

[2] Synthesis of compound [Production Example 2-1]
500 g of an aqueous dispersion (solid content concentration 0.6% by mass) of a polythiophene derivative, which is a polymer containing a repeating unit represented by formula (1a), was mixed with 0.9 g of triethylamine, and the resulting mixture was dried by rotary evaporation. The resulting dried product was further dried overnight at 50° C. in a vacuum oven to obtain 4 g of polythiophene derivative A in which an amine was added to a sulfonic acid group.

[Production Example 2-2]
2.00 g of polythiophene derivative A was dissolved in 100 mL of 28% aqueous ammonia (manufactured by Junsei Chemical Co., Ltd.), and the resulting solution was stirred overnight at room temperature. The resulting reaction mixture was subjected to reprecipitation treatment with 1,500 mL of acetone, and the precipitate was collected by filtration. The resulting precipitate was dissolved again in 20 mL of water and 7.59 g of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and stirred at 60 ° C. for 1 hour. After cooling the resulting reaction mixture, reprecipitation treatment was performed with a mixed solvent of 1,000 mL of isopropyl alcohol and 500 mL of acetone, and the precipitate was collected by filtration. The resulting precipitate was vacuum-dried at 50 ° C. under reduced pressure for 1 hour, and 1.30 g of an amine-treated polythiophene derivative amine adduct was obtained.

[Production Example 2-3]
According to the method described in WO 2006/025342, an arylsulfonic acid compound B represented by formula (b-1) was synthesized.

[3] Preparation of composition for preparing varnish [Preparation Example 1-1]
A dipropylene glycol solution containing 10% by mass of the arylsulfonic acid compound B was prepared by stirring the solution at 400 rpm and 50° C. for 1 hour using a hot stirrer.

[Preparation Example 1-2]
A propylene carbonate solution containing 10% by mass of phosphotungstic acid (PWA, manufactured by Nippon Shinkinzoku Co., Ltd.) was prepared by stirring the solution at 400 rpm for 10 minutes at room temperature using a stirrer.

[Preparation Example 1-3]
A 1,3-dimethyl-2-imidazolidinone solution containing 10% by mass of arylsulfonic acid compound B was prepared by stirring the solution at 400 rpm and 50° C. for 1 hour using a hot stirrer.

[Preparation Example 1-4]
A propylene glycol solution containing 10% by mass of the arylsulfonic acid compound B was prepared by stirring the solution at 400 rpm and 50° C. for 1 hour using a hot stirrer.

[4] Preparation of charge-transporting varnish [Example 1-1]
0.050 g of the amine-treated polythiophene derivative amine adduct was added to 0.49 g of dipropylene glycol (manufactured by Junsei Chemical Co., Ltd.) and 0.080 g of 2-ethylhexylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred for 3 hours at 80° C. using a hot stirrer. To the resulting mixture, 1.88 g of tripropylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.51 g of propylene carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.), 1.88 g of triethylene glycol monobutyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), and 2.83 g of diisopropyl malonate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the mixture was stirred for 10 minutes at 400 rpm at room temperature using a stirrer. Next, 0.50 g of a 10% by mass dipropylene glycol solution of arylsulfonic acid compound B, 1.25 g of a 10% by mass propylene carbonate solution of phosphotungstic acid, 0.50 g of the dispersion X obtained in Production Example 1-4, and 0.025 g of 3,3,3-trifluoropropyltrimethoxysilane (KBM-7103, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the obtained mixture and stirred. Finally, the obtained mixture was filtered through a PP syringe filter having a pore size of 0.2 μm to obtain a charge-transporting varnish.

[Example 1-2]
0.050 g of the amine-treated polythiophene derivative amine adduct was added to 0.49 g of dipropylene glycol (manufactured by Junsei Chemical Co., Ltd.) and 0.080 g of 2-ethylhexylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred for 3 hours at 80° C. using a hot stirrer. To the resulting mixture, 1.88 g of tripropylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.92 g of propylene carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.), 1.88 g of triethylene glycol monobutyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), and 2.83 g of diisopropyl malonate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the mixture was stirred for 10 minutes at 400 rpm at room temperature using a stirrer. Next, 0.50 g of a 10% by mass dipropylene glycol solution of arylsulfonic acid compound B, 0.75 g of a 10% by mass propylene carbonate solution of phosphotungstic acid, 0.59 g of the dispersion X obtained in Production Example 1-4, and 0.025 g of 3,3,3-trifluoropropyltrimethoxysilane (KBM-7103, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the obtained mixture and stirred. The obtained mixture was filtered through a PP syringe filter having a pore size of 0.2 μm to obtain a charge-transporting varnish.

[Examples 1-3]
0.050 g of the amine-treated polythiophene derivative amine adduct was added to 0.83 g of 1,3-dimethyl-2-imidazolidinone (Kanto Chemical Co., Ltd.), 1.28 g of dipropylene glycol (Kanto Chemical Co., Ltd.), and 0.080 g of 2-ethylhexylamine (Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred at 80° C. for 3 hours using a hot stirrer. 1.89 g of dipropylene glycol monomethyl ether (Kanto Chemical Co., Ltd.) was added to the resulting mixture, and the mixture was stirred at 400 rpm at room temperature for 10 minutes using a stirrer. Next, 0.63 g of a 10% by mass solution of arylsulfonic acid compound B in 1,3-dimethyl-2-imidazolidinone, 0.25 g of the dispersion X obtained in Production Example 1-4, and 0.013 g of 3,3,3-trifluoropropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM-7103) were added to the resulting mixture, and the mixture was stirred. The resulting mixture was filtered through a PP syringe filter having a pore size of 0.2 μm to obtain a charge transporting varnish.

[Examples 1 to 4]
0.050 g of the amine-treated polythiophene derivative amine adduct was added to 0.49 g of propylene glycol (manufactured by Junsei Chemical Co., Ltd.) and 0.080 g of 2-ethylhexylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred for 3 hours at 80° C. using a hot stirrer. 2.83 g of tripropylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.46 g of propylene carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.94 g of triethylene glycol monobutyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), and 1.88 g of diisopropyl malonate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the resulting mixture, and the mixture was stirred at 400 rpm at room temperature for 10 minutes using a stirrer. Next, 0.50 g of a 10% by mass propylene glycol solution of arylsulfonic acid compound B, 0.74 g of the dispersion X obtained in Production Example 1-4, and 0.025 g of 3,3,3-trifluoropropyltrimethoxysilane (KBM-7103, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to the obtained mixture and stirred. The obtained mixture was filtered through a PP syringe filter having a pore size of 0.2 μm to obtain a charge-transporting varnish.

[Comparative Example 1-1]
0.050 g of the amine-treated polythiophene derivative amine adduct was added to 0.66 g of propylene glycol (manufactured by Junsei Chemical Co., Ltd.) and 0.080 g of 2-ethylhexylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred at 80° C. for 3 hours using a hot stirrer. To the resulting mixture, 1.26 g of tripropylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.83 g of propylene carbonate (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.27 g of dipropylene glycol monobutyl ether (manufactured by Kanto Chemical Co., Ltd.), and 1.88 g of diisopropyl malonate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added, and the mixture was stirred at 400 rpm at room temperature for 10 minutes using a stirrer. Next, 0.33 g of a 10% by mass propylene glycol solution of arylsulfonic acid compound B and 0.75 g of a 10% by mass dipropylene glycol monobutyl ether solution of phosphotungstic acid were added to the resulting mixture, and the mixture was stirred. Next, the modified colloidal particles (C) obtained in Production Example 1-3 were dispersed in 10% by mass of tripropylene glycol, and 3.0 g of the resulting solution was added. However, the solution became cloudy, and a charge-transporting varnish that was sufficiently uniform to be used for forming a charge-transporting thin film could not be obtained.

[5] Evaluation of Film Properties The varnishes obtained in Examples 1-1 and 1-2 were each applied to a quartz substrate using a spin coater, and then baked at 120° C. for 1 minute, and then baked at 230° C. for 15 minutes to form a thin film with a thickness of 35 nm on the substrate.
The refractive index n and extinction coefficient k of the obtained quartz substrate with the thin film were measured using a multi-angle rotating compensator type high-speed spectroscopic ellipsometer. The results are shown in Table 1. Table 1 also shows the average values of n and k measured in the wavelength range of 400 to 800 nm.

The results in Table 1 confirm that the thin film obtained from the charge transport varnish of the present invention has a high refractive index and transparency.

[6] Fabrication and Characteristic Evaluation of Elements In the following examples, a 25 mm × 25 mm × 0.7 mm glass substrate with a 50 nm thick ITO pattern on its surface was used as the ITO substrate. Prior to use, impurities on the surface were removed using an _O2 plasma cleaning device (150 W, 30 seconds).

[6-1] Fabrication and Characterization of Hole-Only Device (HOD) [Example 2-1]
The varnish obtained in Example 1-1 was applied to an ITO substrate using a spin coater, and then baked at 120° C. for 1 minute. Then, the substrate was baked at 230° C. for 15 minutes to form a 35 nm thin film on the substrate. On the ITO substrate on which the thin film was formed, a 30 nm film of α-NPD was formed at 0.2 nm/sec using a vapor deposition apparatus (vacuum degree 1.0×10 ⁻⁵ Pa). An aluminum thin film was formed thereon using a vapor deposition apparatus (vacuum degree 4.0×10 ⁻⁵ Pa) to obtain an HOD. The vapor deposition was performed under the condition of a vapor deposition rate of 0.2 nm/sec. The thickness of the aluminum thin film was set to 80 nm. In order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the HOD was sealed with a sealing substrate, and then its characteristics were evaluated. Sealing was performed according to the following procedure. In a nitrogen atmosphere with an oxygen concentration of 2 ppm or less and a dew point of -76°C or less, the HOD was placed between the sealing substrates, and the sealing substrates were bonded together with an adhesive (Moresco Moisture Cut WB90US(P) manufactured by MORESCO Corp.). At this time, a moisture scavenger (HD-071010W-40 manufactured by DYNIC Corp.) was placed inside the sealing substrate together with the organic EL element. The bonded sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation amount: 6,000 mJ/ ^cm2 ), and then annealed at 80°C for 1 hour to harden the adhesive.

[Examples 2-2 and 2-4]
HOD was prepared in the same manner as in Example 2-1, except that the varnishes obtained in Examples 1-2 and 1-4 were used instead of the varnish obtained in Example 1-1.

[Example 2-3]
An HOD was produced in the same manner as in Example 2-1, except that the varnish obtained in Example 1-3 was used instead of the varnish obtained in Example 1-1, and the baking time was changed to 200° C. for 1 minute.

The current density of the obtained HOD was measured when it was driven at 5 V. The results are shown in Table 2.

As shown in Table 2, the charge transporting thin film obtained from the charge transporting varnish of the present invention showed good hole injection properties in a film consisting of α-NPD, which corresponds to the hole transporting layer.

[6-2] Preparation of organic EL element and evaluation of its characteristics [Example 3-1]
The varnish obtained in Example 1-1 was applied to an ITO substrate using a spin coater, and then baked at 120°C for 1 minute. Then, the substrate was baked at 230°C for 15 minutes to form a 35 nm thin film on the substrate. Then, a 30 nm film of α-NPD was formed at 0.2 nm/sec on the ITO substrate on which the thin film was formed, using a vapor deposition apparatus (vacuum degree 1.0×10 ⁻⁵ Pa). Next, a 10 nm film of an electron block material HTEB-01 manufactured by Kanto Chemical Co., Ltd. was formed. Next, an emission layer host material NS60 manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. and an emission layer dopant material Ir(PPy) ₃ were co-deposited. The vapor deposition rate was controlled so that the concentration of Ir(PPy) ₃ was 6%, and 40 nm was laminated. Next, thin films of Alq ₃ , lithium fluoride, and aluminum were sequentially laminated to obtain an organic EL device. At this time, the deposition rates were 0.2 nm/sec for _Alq3 and aluminum, and 0.02 nm/sec for lithium fluoride, and the film thicknesses were 20 nm, 0.5 nm, and 80 nm, respectively. The elements were sealed in the same manner as in Example 2-1, and then the characteristics were evaluated.

[Example 3-2]
An organic EL element was produced in the same manner as in Example 3-1, except that the varnish obtained in Example 1-2 was used instead of the varnish obtained in Example 1-1.

[Examples 3-3 and 3-4]
Organic EL elements were prepared in the same manner as in Example 3-1, except that the varnishes obtained in Examples 1-3 and 1-4 were used instead of the varnish obtained in Example 1-1, and baking was performed at 200°C for 1 minute instead of at 120°C for 1 minute.

The driving voltage, current density and current efficiency of the obtained organic EL element were measured when the element was driven at a luminance of 10,000 cd/ ^m2 . The results are shown in Table 3.

As shown in Table 3, the organic EL element having the charge transporting thin film obtained from the charge transporting varnish of the present invention operated well.

Claims (16)

The method includes the steps of: a charge transporting substance; a titanium oxide-containing particle whose surface is modified with a surface treatment agent; an organic solvent; and a dopant substance;
The charge transporting varnish , wherein the charge transporting substance is a polythiophene derivative containing a repeating unit represented by formula (1) or an amine adduct thereof .

(Wherein, R1 ^is a sulfonic acid group,
R2 is -O ^[ C(R ^a R ^b )-C(R ^c R ^d )-O] _p -R ^e or -OR ^f ;
R ^a to R ^d are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group;
R ^e is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group;
p is 1 to 5;
Rf is a hydrogen atom, an alkyl group ^having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group;
Or R ¹ and R ² are bonded to form groups represented by the following formulae (Y1) and (Y2).

[However, the dopant substance does not include an onium borate salt (which is an electrically neutral salt) consisting of at least one anion selected from the group consisting of an anion represented by the following formula (a1) and a monovalent or divalent anion represented by the following formula (a2), and a counter cation.

(In the formula, each Ar is independently an aryl group which may have a substituent or a heteroaryl group which may have a substituent; R is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, or a fluoroaralkyl group having 7 to 10 carbon atoms; and L is an alkylene group, -NH-, an oxygen atom, a sulfur atom, or -CN ⁺ -.) The charge transport varnish according to claim 1, wherein the titanium oxide-containing particles contained in the titanium oxide-containing particles surface-modified with the surface treatment agent are colloidal particles. The charge transport varnish according to claim 2, wherein the titanium oxide-containing particles surface-modified with the surface treatment agent are colloid particles (D) (surface-modified colloid particles (D)) in which the surface of modified titanium oxide-containing colloid particles (C) (modified colloid particles (C)) is coated with metal oxide colloid particles (B) (coating material (B)) using titanium oxide-containing colloid particles (A) as a core (core particle (A)). The charge transport varnish according to claim 1 or 2, wherein the surface treatment agent is an amphiphilic surface treatment agent. The charge transport varnish according to claim 3 or 4, wherein the amphiphilic surface treatment agent is an organosilicon compound, a titanate coupling agent, an aluminate coupling agent, or a phosphorus-based surfactant. The charge transporting varnish according to any one of claims 1 to 5 , further comprising a heteropolyacid. 7. The charge transporting varnish according to claim 6 , wherein said heteropolyacid is phosphotungstic acid. The charge transporting varnish according to any one of claims 1 to 7 , wherein the dopant substance comprises an arylsulfonic acid compound. 9. The charge transporting varnish according to claim 8 , wherein the aryl sulfone compound is an aryl sulfonic acid compound represented by the following formula (H1) or (H2):

(In formula (1), A ¹ represents O or S, A ² represents a naphthalene ring or an anthracene ring, A ³ represents a divalent to tetravalent perfluorobiphenyl group, s represents an integer satisfying 2≦s≦4, and q represents an integer satisfying 1≦q≦4.
In formula (2), A ⁴ to A ⁸ each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, or a halogenated alkenyl group having 2 to 20 carbon atoms, at least three of A ⁴ to A ⁸ are halogen atoms, and r represents an integer satisfying 1≦r≦4. The charge transporting varnish according to any one of claims 1 to 9 , further comprising an organosilane compound. The charge transport varnish according to claim 10, wherein the organosilane compound is 3,3,3-trifluoropropyltrimethoxysilane. A charge transporting thin film obtained from the charge transporting varnish according to any one of claims 1 to 11 . An organic electroluminescence device having the charge transport thin film according to claim 12. 14. The organic electroluminescence device according to claim 13 , wherein the charge transporting thin film is a hole injection layer or a hole transport layer. A method for producing a charge-transporting thin film, comprising applying the charge-transporting varnish according to any one of claims 1 to 11 onto a substrate and evaporating the solvent. A method for producing an organic electroluminescence device, comprising using the charge transporting thin film according to claim 15 .