Charge-transporting ink composition

Abstract

Provided is a charge-transporting ink composition which enables the achievement of a charge-transporting thin film having excellent charge-transporting properties, and which has excellent dispersibility of metal oxide nanoparticles in an organic solvent. The charge-transporting ink composition contains, for example: at least one kind of metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these oxides; a salt that is composed of a cation represented by formula (A2-3) and an anion represented by formula (B1-1), and has a topological polar surface area (TPSA) of 1 or more and a difference (∆MolLogP) between the MolLogP of the cation and the MolLogP of the anion represented by MolLogP(cation) – MolLogP(anion) of more than -3.0; and an organic solvent.

Description

Charge transport ink composition

[0001] This invention relates to a charge-transporting ink composition.

[0002] Organic electroluminescent (hereinafter referred to as organic EL) elements are attracting attention due to their various advantages, such as high contrast, energy saving, and flexibility, and are being put into practical use in fields such as displays and lighting. Organic EL elements use multiple functional thin films, and one of them, the electron transport layer, is responsible for the transfer of charge between the cathode and the light-emitting layer, playing an important role in achieving low-voltage operation and high brightness of organic EL elements.

[0003] Methods for manufacturing organic EL devices are broadly classified into dry processes, such as vapor deposition, and wet processes, such as spin coating and inkjet printing. When comparing the two processes from the perspective of increasing the device area, wet processes can efficiently produce large-area films with high flatness compared to dry processes. Therefore, in the current market where large-area manufacturing of organic EL devices is required, it is important to provide electron transport layers and other components with excellent functionality that can be formed by wet processes.

[0004] Furthermore, with the recent advancements in display technology, quantum dot electroluminescent (hereinafter referred to as quantum dot EL) elements, which use quantum dot materials as the light-emitting layer, have emerged and are showing promise for a wide range of applications. These quantum dot EL elements can be manufactured at low cost using wet processes, and their characteristics, such as controllable emission wavelength, high color purity, high luminous efficiency, and suitability for flexible applications, have attracted considerable attention in fields such as display technology and lighting.

[0005] Such EL elements require the efficient injection of electrons into the light-emitting layer by stacking an electron transport layer containing metal oxide nanoparticles between the light-emitting layer and the cathode. To date, studies have been conducted on the types of metal oxide nanoparticles and primary particle size to improve this efficiency (Patent Documents 1-3).

[0006] Furthermore, metal oxide nanoparticles such as ZnO and SnO2, commonly used in organic EL devices and quantum dot EL devices, have a small particle size (primary particle size: several nm to several tens of nm), resulting in a large specific surface area. Due to the resulting large surface energy, metal oxide nanoparticles are very unstable and prone to aggregation. When metal oxide nanoparticles aggregate, it affects film formation and the conductivity of the resulting thin film (Patent Document 4). When ink containing aggregated metal oxide nanoparticles is applied to form a functional layer such as an electron transport layer, stable film formation cannot be achieved, resulting in an uneven and poorly flat film.

[0007] While methods such as surface treatment of metal oxide nanoparticles (Patent Document 5) and the addition of binders (Patent Document 6) have been employed to suppress the aggregation of metal oxide nanoparticles, further improvements are desired to enhance the performance of the resulting EL elements.

[0008] International Publication No. 2006 / 098540, Japanese Patent Publication No. 2010-055900, International Publication No. 2009 / 084273, International Publication No. 2019 / 128992, International Publication No. 2020 / 121398, International Publication No. 2021 / 044634

[0009] The present invention has been made in view of the above background, and aims to provide a charge-transporting ink composition that has excellent dispersibility of metal oxide nanoparticles in organic solvents and provides a charge-transporting thin film with excellent charge transport properties.

[0010] As a result of diligent research, the present inventors have found a charge-transporting ink composition comprising metal oxide nanoparticles and an organic solvent, which consists of specific cations and anions, has a topological polar surface area (TPSA) of 1 or more, and is MolLogP (カチオン) -MolLogP (アニオン) We discovered that by using a salt that satisfies the condition that the difference between the MolLogP of the cation and the MolLogP of the anion (hereinafter sometimes referred to as "ΔMolLogP") is greater than -3.0, the above metal oxide nanoparticles are less likely to aggregate and exhibit excellent dispersibility in organic solvents. Furthermore, we found that the charge-transporting thin film obtained from this charge-transporting ink composition has high charge-transporting properties, thus completing the present invention.

[0011] That is, the present invention provides the following charge transport ink composition. 1. One or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these; a salt comprising any cation represented by the following formulas (A1) to (A8) and any anion represented by the following formulas (B1) to (B14), having a topological polar surface area (TPSA) of 1 or more, and a difference (ΔMolLogP) between the MolLogP of the cation and the MolLogP of the anion represented by (カチオン) - MolLogP (アニオン) being greater than -3.0; and an organic solvent. [In formula (A1), R a1 to R a4 each independently represents a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, -L1-OR z1 (L1 represents an alkylene group having 1 to 4 carbon atoms, and R z1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), a cycloalkyl group having 3 to 8 carbon atoms, a benzyl group, or a phenethyl group. In formula (A2), R a5 to R a6 each independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms. In formula (A3), R a7 to R a8 each independently represents a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, -L2-OR z2 (L2 represents an alkylene group having 1 to 4 carbon atoms, and R z2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), -L3-SO3H (L3 represents an alkylene group having 1 to 4 carbon atoms.), a benzyl group, or -L4-SiOR z3 (L4 represents an alkylene group having 1 to 4 carbon atoms, and R z3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), and R a9R represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. In formula (A4), R a10 ~R a11 Each of these independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms. In formula (A5), R a12 ~R a13 Each of these independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms. In formula (A6), R a14 ~R a17 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, and -L5-OR z4 (L5 represents an alkylene group with 1 to 4 carbon atoms, R z4 R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), ), represents a cycloalkyl group having 3 to 8 carbon atoms or a benzyl group. In formula (A7), R a18 This consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, and -L6-OR z5 (L6 represents an alkylene group with 1 to 4 carbon atoms, R z5 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), -L7-SO3H (L7 represents an alkylene group having 1 to 4 carbon atoms), a benzyl group or -L8-SiOR z6 (L8 represents an alkylene group with 1 to 4 carbon atoms, R z6 R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. a19 ~R a21 Each of these independently consists of a hydrogen atom, a C1-C8 alkyl group, a phenyl group, or -L9-OR z7 (L9 represents an alkylene group with 1 to 4 carbon atoms, R z7 R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. In formula (A8), R a22 ~R a24 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, and -L. 10 -OR z8 (L 10 R represents an alkylene group with 1 to 4 carbon atoms. z8 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), ), represents a cycloalkyl group or benzyl group having 3 to 8 carbon atoms. (In formula (B1), R b1 ~R b2 Each of these independently represents either a fluorine atom or a trifluoromethyl group. In formula (B2), R b3 R represents a hydroxyl group, a carbon-1 to carbon-4 alkoxy group, a carbon-1 to carbon-4 alkyl group, a trifluoromethyl group, or a p-toluenesulfonyl group. In formula (B3), R b4 ~R b5) Each independently represents an alkyl group having 1 to 4 carbon atoms, and each independently represents an oxygen atom or a sulfur atom. 2. A charge-transporting ink composition 1 in which the metal oxide nanoparticles are one or more particles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, and Ga, and composites of at least two of these. 3. A charge-transporting ink composition 2 in which the metal oxide nanoparticles are one or more particles selected from the group consisting of metal oxides selected from the group consisting of Zn and Mg, and composites of at least two of these. 4. A charge-transporting ink composition 1 in which the metal oxide nanoparticles are particles in which the surface of the metal oxide nanoparticles is coated with a metal oxide, with one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of metal oxides selected from the group consisting of at least two of these. 5. 4. A charge-transporting ink composition in which the metal oxide nanoparticles are particles in which one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Zr, Sn, and Ga, and composites of at least two of these, form a nucleus, and the surface of the nucleus is coated with a metal oxide. 6. A charge-transporting ink composition in which the metal oxide nanoparticles are particles in which one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn and Mg, and composites of at least two of these, form a nucleus, and the surface of the nucleus is coated with a metal oxide. 7. A charge-transporting ink composition in which any of 1 to 6 is a salt comprising a cation represented by any of the above formulas (A1) to (A4), (A6), and (A7) and an anion represented by any of the above formulas (B1) to (B3) and (B6) to (B10). 8. A charge-transporting thin film obtained from any of the charge-transporting ink compositions in which 1 to 7. 9. An electronic device comprising the charge-transporting thin film of 8. 10. The above charge-transporting thin film is an electron-transporting layer of the electronic element 9. 11. The above electronic element is an organic EL element 10. 12. The above electronic element is a quantum dot EL element 10.13. A method for producing a charge-transporting thin film, characterized by applying one of the charge-transporting ink compositions from 1 to 7 onto a substrate and evaporating an organic solvent.

[0012] By using the charge-transporting ink composition of the present invention, a charge-transporting thin film with excellent charge transport properties can be obtained. This charge-transporting thin film can be suitably used as a thin film for electronic devices, including organic EL elements and quantum dot EL elements.

[0013] The present invention will be described in more detail below. The charge-transporting ink composition of the present invention is a salt comprising: one or more metal oxide nanoparticles selected from the group consisting of metal oxide (カチオン) -MolLogP (アニオン) The salt comprises a salt in which the difference between the MolLogP of the cation and the MolLogP of the anion (ΔMolLogP) is greater than -3.0, and an organic solvent.

[0014] In this invention, "solid content" in relation to the charge-transporting ink composition of the present invention refers to components other than the solvent contained in the composition. Furthermore, in this invention, charge transport is synonymous with conductivity and also synonymous with electron transport. The charge-transporting ink composition of the present invention may be charge-transporting in itself, or the solid film obtained using the composition may be charge-transporting.

[0015] [Metal Oxide Nanoparticles] The charge-transporting ink composition of the present invention contains one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these. In the present invention, "nanoparticles" means fine particles whose average particle diameter for primary particles is on the order of nanometers (typically 500 nm or less). The particle diameter can be measured by methods such as transmission electron microscopy or dynamic light scattering (DLS). Unless otherwise specified, the particle diameter described herein is the particle diameter calculated by any known measurement method.

[0016] In the above metal oxide nanoparticles, metal oxides with a valency of 2 to 6 are preferred, with Zn, Mg, Ti, Zr, Sn, and Ga being more preferred, and Zn and Mg being even more preferred.

[0017] Specific examples of oxides of the above metals include ZnO, MgO, TiO2, ZrO2, SnO2, Ga2O3, Fe2O3, Ta2O5, Nb2O5, Y2O3, MoO3, WO3, PbO, In2O3, Bi2O3, SrO, ZnMgO, SrTiO3, BaTiO3, SnO2-WO3 complex, SnO2-ZrO2 complex, SnO2-TiO2 complex, SnO2-TiO2-ZrO2 complex, and others. In the present invention, among these, from the viewpoint of charge transport properties, ZnO, MgO, TiO2, ZrO2, SnO2, Ga2O3, ZnMgO, SnO2-ZrO2 complex, SnO2-TiO2 complex, and SnO2-TiO2-ZrO2 complex are preferred, ZnO, MgO, ZnMgO, SnO2, and SnO2-TiO2-ZrO2 complex are more preferred, and ZnO and ZnMgO are even more preferred.

[0018] The primary particle size of the above metal oxide nanoparticles is not particularly limited as long as it is nano-sized, but considering the acquisition of thin films with good reproducibility and excellent flatness, it is preferably 1 to 60 nm, more preferably 2 to 40 nm, and even more preferably 2 to 20 nm.

[0019] The metal oxide nanoparticles described above may also be surface-treated metal oxide nanoparticles in which the surface is coated with one or more materials selected from the group consisting of metal oxides and surface treatment agents. This coating of the metal oxide nanoparticle surface makes the particles less likely to aggregate and improves their dispersibility in organic solvents. In the following description, both untreated metal oxide nanoparticles and the surface-treated metal oxide nanoparticles described above may simply be referred to as metal oxide nanoparticles.

[0020] The following are examples of preferred embodiments of the above-mentioned surface-treated metal oxide nanoparticles: (1) An embodiment in which one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these, form a core, and the surface of the core is coated with a metal oxide. (2) An embodiment in which one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these, form a core, and the surface of the core is coated with one or more surface treatment agents. (3) A configuration in which one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these, are used as a core, the surface of the core is coated with a metal oxide, and the surface of the metal oxide is further coated with one or more surface treatment agents.

[0021] In the present invention, the metal oxide nanoparticles are more preferably particles in which one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, and Ga, and composites of at least two of these, form a core, and the surface of the core is coated with a metal oxide.

[0022] Furthermore, as the metal oxide nanoparticles, particles in which one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn and Mg, and composites of at least two of these, form a core, and the surface of the core is coated with a metal oxide are even more preferable.

[0023] As the metal oxide coating the surface of the nucleus, from the viewpoint of achieving both dispersibility in organic solvents and charge transport properties, at least one selected from the group consisting of MgO, In2O3, Sb2O5, SiO2, SnO2, TiO2, WO3, ZnO, ZrO2, and composites of at least two of these is preferred; at least one selected from the group consisting of MgO, Sb2O5, SiO2, SnO2, TiO2, ZnO, and composites of at least two of these is more preferred; at least one selected from the group consisting of MgO, SiO2, SnO2, ZnO, and composites of at least two of these is even more preferred; and MgO, ZnO, and SnO2-SiO2 composites are even more preferred.

[0024] Furthermore, if the metal oxide is an SnO2-SiO2 composite, the mass ratio of SiO2 / SnO2 is preferably 0.1 to 5.0. It is also preferable that an amine compound is bonded to the surface of the metal oxide, and more preferably that the molar ratio of the amine compound / (SnO2 + SiO2) is in the range of 0.001 to 1.0.

[0025] The above amine compounds can be primary, secondary, or tertiary amines. Examples of primary amines include methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, amylamine, allylamine, hexylamine, hepitylamine, octylamine, nonylamine, decylamine, dodecylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, and cyclohexylamine. Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, diisobutylamine, N-ethyl-1,2-dimethylpropylamine, diamylamine, and diallylamine. Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, triamylamine, and triallylamine. These amine compounds may be used individually or in combination of two or more.

[0026] A known method can be used to attach the above amine compound to the SnO2-SiO2 complex. For example, the method described in Japanese Patent No. 5704345 is a known method.

[0027] The primary particle size of the metal oxide is not particularly limited as long as it is large enough to sufficiently cover the surface of the nucleus, but from the viewpoint of reliably covering the nucleus, 1 to 10 nm is preferred.

[0028] The mass ratio of the above metal oxide nanoparticles to the above metal oxide (metal oxide / metal oxide nanoparticles) is preferably 0.01 to 1.00, and more preferably 0.03 to 0.30, from the viewpoint of achieving both dispersibility in organic solvents and charge transport properties.

[0029] The above surface treatment agents are preferably compounds represented by the following formulas (S1) to (S9). These surface treatment agents may be used individually or in combination of two or more.

[0030]

[0031] In formula (S1), R 1Each of these is an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a thioureido group, or a cyano group, and is bonded to a silicon atom by a Si-C bond, R 2 Each of these independently represents an alkoxy group, an acyloxy group, or a halogen atom, and a represents an integer from 1 to 3.

[0032] In formula (S2), R 3 Each of these is independently an alkyl group having 1 to 3 carbon atoms, or an aryl group having 6 to 30 carbon atoms, R 4 Each of the following independently represents an alkoxy group, an acyloxy group, or a halogen atom; Y represents an alkylene group, an NH group, or an oxygen atom; b is an integer from 1 to 3; and c is 0 or 1.

[0033] In formula (S3), R 5 Each of these is independently an alkyl group having 1 to 3 carbon atoms, or an aryl group having 6 to 30 carbon atoms, R 6 Each of these independently represents an alkoxy group, an acyloxy group, or a halogen atom, and d represents an integer from 1 to 3.

[0034] In equation (S4), R 7 Each independently represents an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a thioureido group, or a cyano group, and e represents 1 or 2.

[0035] In formula (S5), R 8 This represents an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a thioureido group, or a cyano group.

[0036] In formula (S6), R 9This represents an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a thioureido group, or a cyano group.

[0037] In formula (S7), R 10 R represents an organic group having an alkyl group, halogenated alkyl group, alkenyl group, aryl group, or polyether group, epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, thioureido group, or cyano group. 11 This represents an organic group having a hydrogen atom, an alkyl group, an alkyl halide, an alkenyl group, an aryl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a thioureido group, or a cyano group.

[0038] In formula (S8), R 12 R represents an organic group having an alkyl group, halogenated alkyl group, alkenyl group, aryl group, or polyether group, epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, thioureido group, or cyano group. 13 represents an organic group having a hydrogen atom, alkyl group, alkyl halide, alkenyl group, aryl group, or polyether group, epoxy group, (meth)acryloyl group, mercapto group, amino group, ureido group, thioureido group, or cyano group, and Z represents an oxygen atom or sulfur atom.

[0039] In formula (S9), R 14 Each of these independently represents an organic group having an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, a thioureido group, or a cyano group, and f represents 1 or 2.

[0040] As the alkyl group, alkyl groups having 1 to 18 carbon atoms are preferred, alkyl groups having 1 to 10 carbon atoms are more preferred, and alkyl groups having 1 to 8 carbon atoms are even more preferred. Specific examples of the above alkyl groups include methyl group, ethyl group, n-propyl group, i-propyl group, cyclopropyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, cyclobutyl group, 1-methyl-cyclopropyl group, 2-methyl-cyclopropyl group, n-pentyl group, 1-methyl-n-butyl group, 2-methyl-n-butyl group, 3-methyl-n-butyl group, 1,1-dimethyl-n-propyl group, 1,2-dimethyl-n-propyl group, 2,2-dimethyl-n-propyl group, 1-ethyl-n-propyl group, cyclopropyl group Lopentyl group, 1-methyl-cyclobutyl group, 2-methyl-cyclobutyl group, 3-methyl-cyclobutyl group, 1,2-dimethyl-cyclopropyl group, 2,3-dimethyl-cyclopropyl group, 1-ethyl-cyclopropyl group, 2-ethyl-cyclopropyl group, n-hexyl group, 1-methyl-n-pentyl group, 2-methyl-n-pentyl group, 3-methyl-n-pentyl group, 4-methyl-n-pentyl group, 1,1-dimethyl-n-butyl group, 1,2-dimethyl-n-butyl group, 1,3-dimethyl-n-butyl group, 2,2-dimethyl-cyclobutyl group Methyl-n-butyl group, 2,3-dimethyl-n-butyl group, 3,3-dimethyl-n-butyl group, 1-ethyl-n-butyl group, 2-ethyl-n-butyl group, 1,1,2-trimethyl-n-propyl group, 1,2,2-trimethyl-n-propyl group, 1-ethyl-1-methyl-n-propyl group, 1-ethyl-2-methyl-n-propyl group, cyclohexyl group, 1-methyl-cyclopentyl group, 2-methyl-cyclopentyl group, 3-methyl-cyclopentyl group, 1-ethyl-cyclobutyl group, 2-ethyl-cyclobutyl group, 3-ethyl-cyclobutyl group, 1,2-dimethyl-cyclobutyl group, 1,3-dimethyl-cyclobutyl group, 2,2-dimethyl-cyclobutyl group, 2,3-dimethyl-cyclobutyl group, 2,4-dimethyl-cyclobutyl group, 3,3-dimethyl-cyclobutyl group, 1-n-propyl-cyclopropyl group, 2-n-propyl-cyclopropyl group, 1-i-propyl-cyclopropyl group, 2-i-propyl-cyclopropyl group, 1,2,2-trimethyl-cyclopropyl group, 1,2,3-trimethyl-cyclopropyl group, 2,Examples include 2,3-trimethylcyclopropyl group, 1-ethyl-2-methylcyclopropyl group, 2-ethyl-1-methylcyclopropyl group, 2-ethyl-2-methylcyclopropyl group and 2-ethyl-3-methylcyclopropyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, etc.

[0041] Examples of halogenated alkyl groups include groups in which at least one carbon atom of the alkyl group is substituted with a halogen group, with halogenated alkyl groups having 1 to 18 carbon atoms being preferred, halogenated alkyl groups having 1 to 10 carbon atoms being more preferred, and halogenated alkyl groups having 1 to 8 carbon atoms being even more preferred. Specific examples of the halogenated alkyl groups include fluoromethyl, difluoromethyl, trifluoromethyl, bromodifluoromethyl, 2-chloroethyl, 2-bromoethyl, 1,1-difluoroethyl, 2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, 2-chloro-1,1,2-trifluoroethyl, pentafluoroethyl, 3-bromopropyl, 2,2,3,3-tetrafluoropropyl, 1,1,2,3,3,3-hexafluoropropyl, 1,1,1,3,3,3-hexafluoropropan-2-yl, 3-bromo-2-methylpropyl, 4-bromobutyl, perfluoropentyl, and 2-(perfluorohexyl)ethyl group.

[0042] As the alkenyl group, an alkenyl group having 2 to 10 carbon atoms is preferred, and an alkenyl group having 2 to 8 carbon atoms is more preferred. Specific examples of the above alkenyl groups include ethenyl group, 1-propenyl group, 2-propenyl group, 1-methyl-1-ethenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, 1-methyl-1-propenyl group, 1-methyl-2-propenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 4-pentenyl group, 1-n-propylethenyl group, 1-methyl-1-butenyl group, 1-methyl-2-butenyl group, 1-methyl-3-butenyl group, 2-ethyl-2-propenyl group, 2-methyl-1-butenyl group, 2-methyl-2-butenyl group, 2-methyl-3-butenyl group, 3 Examples include methyl-1-butenyl group, 3-methyl-2-butenyl group, 3-methyl-3-butenyl group, 1,1-dimethyl-2-propenyl group, 1-i-propylethenyl group, 1,2-dimethyl-1-propenyl group, 1,2-dimethyl-2-propenyl group, 1-cyclopentenyl group, 2-cyclopentenyl group, 3-cyclopentenyl group, 1-hexenyl group, 2-hexenyl group, 3-hexenyl group, 4-hexenyl group, 5-hexenyl group, 1-methyl-1-pentenyl group, 1-methyl-2-pentenyl group, 1-methyl-3-pentenyl group, 1-methyl-4-pentenyl group, 1-n-butylethenyl group, 2-methyl-1-pentenyl group, and 2-methyl-2-pentenyl group.

[0043] The aryl group is preferably one having 6 to 30 carbon atoms, and more preferably one having 6 to 10 carbon atoms. Specific examples of the above aryl group include phenyl, naphthyl, anthracenyl, and pyrenyl groups.

[0044] As the alkoxy group, an alkoxy group having 1 to 10 carbon atoms is preferred, and an alkoxy group having 1 to 8 carbon atoms is more preferred. Specific examples of the above alkoxy group include methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, s-butoxy group, t-butoxy group, n-pentyloxy group, 1-methyl-n-butoxy group, 2-methyl-n-butoxy group, 3-methyl-n-butoxy group, 1,1-dimethyl-n-propoxy group, 1,2-dimethyl-n-propoxy group, 2,2-dimethyl-n-propoxy group, 1-ethyl-n-propoxy group, n-hexyloxy group, and the like.

[0045] As the acyloxy group, an acyloxy group having 2 to 10 carbon atoms is preferred, and an acyloxy group having 2 to 8 carbon atoms is more preferred. Specific examples of the above-mentioned acyloxy groups include, but are not limited to, methylcarbonyloxy group, ethylcarbonyloxy group, n-propylcarbonyloxy group, i-propylcarbonyloxy group, n-butylcarbonyloxy group, i-butylcarbonyloxy group, s-butylcarbonyloxy group, t-butylcarbonyloxy group, n-pentylcarbonyloxy group, 1-methyl-n-butylcarbonyloxy group, 2-methyl-n-butylcarbonyloxy group, 3-methyl-n-butylcarbonyloxy group, 1,1-dimethyl-n-propylcarbonyloxy group, 1,2-dimethyl-n-propylcarbonyloxy group, 2,2-dimethyl-n-propylcarbonyloxy group, 1-ethyl-n-propylcarbonyloxy group, n-hexylcarbonyloxy group, 1-methyl-n-pentylcarbonyloxy group, and 2-methyl-n-pentylcarbonyloxy group.

[0046] Examples of alkylene groups include alkylene groups derived from the alkyl groups mentioned above, with alkylene groups having 1 to 18 carbon atoms being preferred, and alkylene groups having 1 to 8 carbon atoms being more preferred. Specific examples of the alkylene groups include methylene group, methylmethylene group, dimethylmethylene group, ethylene group, 1,2-dimethylethylene group, tetramethylethylene group, trimethylene group, propylene group, tetramethylene group, pentamethylene group, hexamethylene group, 1,2-cyclohexylene group, 1,3-cyclohexylene group, and 1,4-cyclohexylene group.

[0047] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0048] Examples of organic groups having a polyether group include polyetherpropyl groups having an alkoxy group. For example, (CH3O)3SiC3H6(OC2H4) n OCH3 is an example. n can be used in the range of 1 to 100, or 1 to 10.

[0049] Examples of organic groups having an epoxy group include the 2-(3,4-epoxycyclohexyl)ethyl group and the 3-glycidoxypropyl group.

[0050] The above-mentioned (meth)acryloyl group refers to both the acryloyl group and the methacryloyl group. Examples of organic groups having a (meth)acryloyl group include the 3-methacryloxypropyl group and the 3-acryloxypropyl group.

[0051] Examples of organic groups containing a mercapto group include the 3-mercaptopropyl group.

[0052] Examples of organic groups having an amino group include 2-aminoethyl group, 3-aminopropyl group, N-2-(aminoethyl)-3-aminopropyl group, N-(1,3-dimethylbutylidene)aminopropyl group, N-phenyl-3-aminopropyl group, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl group.

[0053] Examples of organic groups having a ureido group include the 3-ureidopropyl group.

[0054] Examples of organic groups having a thioureido group include 3-thioureidopropyl.

[0055] Examples of organic groups containing a cyano group include the 3-cyanopropyl group.

[0056] In the compound represented by formula (S1), R 1 Preferably, each of these is an organic group having an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a thioureido group, and is bonded to a silicon atom by a Si-C bond. 2 As for each of these, an alkoxy group is preferred independently.

[0057] Furthermore, the compound represented by (S1) above is R 1 However, each is independently an alkyl group or an alkyl group substituted with a mercapto group, R 1 At least one of them is an alkyl group substituted with a mercapto group, R 2 However, a more preferable embodiment is one in which the group is an alkoxy group and a is an integer from 1 to 3.

[0058] Specific examples of compounds represented by formula (S1) include, but are not limited to, the compounds represented by the following formulas (S1-1) to (S1-10).

[0059]

[0060] In formula (S2), R 3 As such, a C1-C3 alkyl group or a C6-C10 aryl group is preferred, independently of each other. 4 For each component, an alkoxy group or a halogen atom is preferred. For Y, an alkylene group, an NH group, or an oxygen atom is preferred.

[0061] Furthermore, the compound represented by formula (2) above is preferably a compound that can form a trimethylsilyl group or a triethylsilyl group on the surface of the silica particles.

[0062] Specific examples of compounds represented by formula (S2) include, but are not limited to, the compounds represented by the following formulas (S2-1) to (S2-4). These silane compounds can be commercially available; for example, silane compounds manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0063]

[0064] In formula (S3), R 5 As such, a C1-C3 alkyl group or a C6-C10 aryl group is preferred, independently of each other. 6 As such, an alkoxy group or a halogen atom is preferred, independently of each other.

[0065] Furthermore, the compound represented by formula (S3) above is preferably a compound that can form a trimethylsilyl group or a triethylsilyl group on the surface of the silica particles. Examples of such compounds include those represented by the following formulas (S3'-1) to (S3'-2).

[0066]

[0067] In the above formula, R 51 The group is an alkoxy group, and specific examples include the methoxy group, ethoxy group, and others as exemplified above. The silane compound can be a commercially available product; for example, a silane compound manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0068] Specific examples of compounds represented by formula (S3) include, but are not limited to, the compounds represented by the following formulas (S3-1) to (S3-4).

[0069]

[0070] In equation (S4), R 7 Preferably, each of these is an organic group having an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group.

[0071] Specific examples of compounds represented by formula (S4) include, but are not limited to, the compound represented by formula (S4-1) below.

[0072]

[0073] In formula (S5), R 8 Preferably, the group is an alkyl group, an alkenyl group, or an organic group having a polyether group, epoxy group, (meth)acryloyl group, mercapto group, ureido group, or thioureido group.

[0074] In formula (S6), R 9 Preferably, the group is an alkyl group, an alkenyl group, or an organic group having a polyether group, epoxy group, (meth)acryloyl group, mercapto group, ureido group, or thioureido group.

[0075] Specific examples of compounds represented by formula (S6) include, but are not limited to, the compound represented by formula (S6-1) below.

[0076]

[0077] In formula (S7), R 10 Preferably, the organic group has an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group. 11 Preferably, the organic group has a hydrogen atom, an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group.

[0078] In formula (S8), R 12 Preferably, the organic group has an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group. 13 Preferably, the organic group has a hydrogen atom, an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group.

[0079] Specific examples of compounds represented by formula (S8) include, but are not limited to, the compound represented by formula (S8-1) below.

[0080]

[0081] In formula (S9), R 14 Preferably, each of these is an organic group having an alkyl group, an alkenyl group, or a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group.

[0082] The above-mentioned surface-treated metal oxide nanoparticles can be manufactured by coating the surface of colloidal metal oxide nanoparticles (nuclei) having a primary particle size within the above range with one or more selected from the group consisting of the above-mentioned metal oxides and surface treatment agents. Specific embodiments of the above-mentioned surface-treated metal oxide nanoparticles include metal oxide-coated nanoparticles obtained by coating the surface of colloidal metal oxide nanoparticles (nuclei) having a primary particle size within the above range with a metal oxide; surface-treated agent-coated nanoparticles obtained by coating the surface of colloidal metal oxide nanoparticles (nuclei) having a primary particle size within the above range with a surface treatment agent; and surface-treated metal oxide nanoparticles obtained by coating the surface of colloidal metal oxide nanoparticles (nuclei) having a primary particle size within the above range with a metal oxide (metal oxide-coated nanoparticles), and further coating the surface of the metal oxide with a surface treatment agent. Regarding the method for manufacturing colloidal metal oxide nanoparticles and the method for coating the surface of the above-mentioned metal oxide nanoparticles with a metal oxide, known methods should be referenced. Known methods include, for example, the methods described in Japanese Patent No. 4561955, Japanese Patent No. 4730487, and Japanese Patent No. 5704345. Furthermore, known methods can be used as a reference for the method of coating the surface of the metal oxide with a surface treatment agent. For example, a known method is the method described in Japanese Patent No. 5704345.

[0083] Furthermore, from the viewpoint of improving the charge transport properties of the resulting thin film, it is preferable that the metal oxide coated nanoparticles, whose nucleus surface is coated with a metal oxide, are hydrothermally treated metal oxide coated nanoparticles during the manufacturing process. In the present invention, the following methods 1 and 2 can be used as methods for hydrothermal treatment. Method 1: A method of applying hydrothermal treatment to metal oxide nanoparticles before surface coating to obtain hydrothermally treated metal oxide nanoparticles, and then coating the surface of the hydrothermally treated metal oxide nanoparticles with a metal oxide. Method 2: A method of applying hydrothermal treatment to metal oxide coated nanoparticles obtained by coating the surface of metal oxide nanoparticles (without hydrothermal treatment) with a metal oxide, and then further treating the metal oxide coated nanoparticles to obtain hydrothermally treated metal oxide coated nanoparticles.

[0084] When performing hydrothermal treatment, the temperature is preferably 60 to 180°C. The treatment time is preferably 0.1 to 50 hours.

[0085] Surface treatment of metal oxide coated nanoparticles with a surface treatment agent can be performed by adding the surface treatment agent to a dispersion of metal oxide coated nanoparticles and heating it at a predetermined temperature. If the dispersion medium for the metal oxide coated nanoparticles is not suitable for use with the surface treatment agent, it may be replaced with a suitable solvent.

[0086] The surface treatment temperature described above can be from 20°C to the boiling point of the dispersion medium, but 20 to 100°C is preferred. The treatment time is preferably 0.1 to 48 hours.

[0087] From the viewpoint of reliably coating the surface of the metal oxide coated nanoparticles, the amount of surface treatment agent used is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass, relative to the mass of the metal oxide coated nanoparticles.

[0088] When using compounds represented by formulas (S1) to (S3) (silane compounds) as the surface treatment agent described above, water is required for the hydrolysis of these silane compounds. However, the water remaining in the solvent when the aqueous medium is replaced with an organic solvent can be used. For example, water present at 0.01 to 10% by mass can be used. Furthermore, hydrolysis can be carried out with or without a catalyst.

[0089] The surface-treated metal oxide nanoparticles contained in the charge-transporting ink composition of the present invention may be one type alone or two or more types.

[0090] It is preferable that the surface-treated metal oxide nanoparticles contained in the charge-transporting ink composition of the present invention are uniformly dispersed in the composition.

[0091] The above-mentioned surface-treated metal oxide nanoparticles may contain one or more organic capping groups. These organic capping groups may be reactive or non-reactive. An example of a reactive organic capping group is an organic capping group that can be crosslinked by ultraviolet light or a radical initiator.

[0092] The primary particle size of the surface-treated metal oxide nanoparticles described above is not particularly limited as long as it is nano-sized, but considering the need to obtain a thin film with good reproducibility and excellent flatness, 2 to 40 nm is preferred, and 2 to 20 nm is more preferred.

[0093] In the charge-transporting ink composition of the present invention, the content of metal oxide nanoparticles is not particularly limited, but from the viewpoint of suppressing particle aggregation in the charge-transporting ink composition and obtaining a thin film with excellent charge transport properties and good reproducibility, it is preferably 10 to 99.99% by mass, more preferably 40 to 99.90% by mass, even more preferably 60 to 99.70% by mass, and most preferably 80 to 99.50% by mass of the solid content.

[0094] In particular, in the present invention, by using a metal oxide nanoparticle sol in which metal oxide nanoparticles are dispersed, a composition in which metal oxide nanoparticles are uniformly dispersed can be prepared with high reproducibility. Such a metal oxide nanoparticle sol can be prepared by known methods using a solvent that may be contained in the charge-transporting ink composition of the present invention and metal oxide nanoparticles. The metal oxide nanoparticles used in the above metal oxide nanoparticle sol may be surface-treated metal oxide nanoparticles coated with one or more selected from the group consisting of metal oxides and surface treatment agents.

[0095] Specific examples of metal oxide nanoparticles used in the above-mentioned metal oxide nanoparticle sol, and of the metal oxide and surface treatment agent used for the surface treatment of the metal oxide nanoparticles, are the same as those described above. Furthermore, preferred embodiments of the metal oxide nanoparticles are also the same as those described above.

[0096] The metal oxide nanoparticle sol is not particularly limited as long as the metal oxide nanoparticles are stably dispersed in a solvent, and is usually in the form of a dispersion. Examples of metal oxide nanoparticle sols include metal oxide nanoparticles dispersed in various solvents, such as alcohols, glycols, ketones, esters, ethers, amides, hydrocarbons, or mixtures thereof. Examples of alcohols include methanol, ethanol, n-propanol, i-propanol, n-butanol, 1-octanol, 1-nonanol, 1-decanol, tetrahydrofurfuryl alcohol, terpineol, etc. Examples of glycols include ethylene glycol, propylene glycol, 2-methyl-2,4-pentanediol, 1,3-octylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, etc. Examples of ketones include acetone, acetylacetone, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, 4-hydroxy-4-methyl-2-pentanone, 2-heptanone, cyclohexanone, methylcyclopentanone, and isophorone. Examples of esters include dimethyl carbonate, diethyl carbonate, propylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dimethyl adipate, diethyl adipate, dipropyl adipate, diisopropyl malonate, dimethyl sebacate, diethyl sebacate, and propylene glycol monomethyl ether acetate.Examples of ethers include dimethyl ether, ethyl methyl ether, diethyl ether, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol butyl ether. Examples of amides include N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, N-ethylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone. Examples of hydrocarbons include n-hexane, n-heptane, n-octane, n-nonane, n-decane, i-octane, i-nonane, i-decane, and toluene.

[0097] In particular, in the present invention, metal oxide nanoparticles whose dispersion medium is methanol, ethanol, n-propanol, i-propanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripylene glycol, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, propylene carbonate, propylene glycol monomethyl ether acetate, ethyl acetate, butyl acetate, methyl methacrylate, diisopropyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, tripylene glycol monomethyl ether, tripylene glycol butyl ether, N,N-dimethylformamide, n-hexane, or toluene are preferred.

[0098] The solid content concentration of the metal oxide nanoparticle sol of the present invention is appropriately set in consideration of the saturation solubility in a solvent, storage stability, etc., but is usually about 1 to 60% by mass, preferably about 3 to 55% by mass, and more preferably about 3 to 50% by mass.

[0099] [Salt] The charge transport ink composition of the present invention is a salt composed of any cation represented by the following formulas (A1) to (A8) and any anion represented by the following formulas (B1) to (B14), having a topological polar surface area (TPSA) of 1 or more, and a difference (ΔMolLogP) between the MolLogP of the cation represented by (カチオン) - MolLogP (アニオン) and the MolLogP of the anion is greater than -3.0.

[0100]

[0101] In formula (A1), R a1 to R a4 are each independently a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, -L1-OR z1 (L1 represents an alkylene group having 1 to 4 carbon atoms, and R z1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), a cycloalkyl group having 3 to 8 carbon atoms, a benzyl group or a phenethyl group.

[0102] In formula (A2), R a5 to R a6 are each independently an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms.

[0103] In formula (A3), R a7 to R a8 are each independently a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, -L2-OR z2 (L2 represents an alkylene group having 1 to 4 carbon atoms, and R z2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), -L3-SO3H (L3 represents an alkylene group having 1 to 4 carbon atoms.), a benzyl group or -L4-SiOR z3 (L4 represents an alkylene group having 1 to 4 carbon atoms, and Rz3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), represents R a9 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

[0104] In formula (A4), R a10 to R a11 each independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms.

[0105] In formula (A5), R a12 to R a13 each independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms.

[0106] In formula (A6), R a14 to R a17 each independently represents a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, -L5-OR z4 (L5 represents an alkylene group having 1 to 4 carbon atoms, and R z4 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), a cycloalkyl group having 3 to 8 carbon atoms or a benzyl group.

[0107] In formula (A7), R a18 represents a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, -L6-OR z5 (L6 represents an alkylene group having 1 to 4 carbon atoms, and R z5 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), -L7-SO3H (L7 represents an alkylene group having 1 to 4 carbon atoms.), a benzyl group or -L8-SiOR z6 (L8 represents an alkylene group having 1 to 4 carbon atoms, and R z6 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), and R a19 to R a21 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group or -L9-OR z7 (L9 represents an alkylene group having 1 to 4 carbon atoms, and R z7 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.).

[0108] In formula (A8), R a22~R a24 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, and -L. 10 -OR z8 (L 10 R represents an alkylene group with 1 to 4 carbon atoms. z8 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), ), represents a cycloalkyl group having 3 to 8 carbon atoms or a benzyl group.

[0109]

[0110] In formula (B1), R b1 ~R b2 Each of these independently represents either a fluorine atom or a trifluoromethyl group.

[0111] In formula (B2), R b3 This represents a hydroxyl group, a carbon-1 to carbon-4 alkoxy group, a carbon-1 to carbon-4 alkyl group, a trifluoromethyl group, or a p-toluenesulfonyl group.

[0112] In formula (B3), R b4 ~R b5 Each of these independently represents an alkyl group having 1 to 4 carbon atoms, and each of these independently represents either an oxygen atom or a sulfur atom.

[0113] The alkyl group having 1 to 16 carbon atoms may be linear or branched. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and hexadecyl groups.

[0114] Examples of alkyl groups having 1 to 4 carbon atoms include those with 1 to 4 carbon atoms from among the groups exemplified above as alkyl groups having 1 to 16 carbon atoms.

[0115] Examples of alkyl groups having 1 to 8 carbon atoms include those groups having 1 to 8 carbon atoms from among the alkyl groups having 1 to 16 carbon atoms exemplified above.

[0116] Examples of alkylene groups having 1 to 4 carbon atoms include methylene group, methylmethylene group, dimethylmethylene group, ethylene group, 1,2-dimethylethylene group, trimethylene group, propylene group, tetramethylene group, and 2-methylpropylene group.

[0117] Examples of cycloalkyl groups having 3 to 8 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups.

[0118] Examples of alkoxy groups having 1 to 4 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, and tert-butoxy groups.

[0119] In the cation represented by formula (A1), R a1 ~R a4 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, and -L1-OR z1 (L1 represents an alkylene group with 1 to 4 carbon atoms, R z1 represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms. A cycloalkyl group having 5 to 6 carbon atoms, a benzyl group, or a phenethyl group is preferred, and a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group is more preferred.

[0120] Specific examples of cations represented by formula (A1) include, but are not limited to, the cations represented by the following formulas (A1-1) to (A1-21).

[0121]

[0122] In the cation represented by formula (A2), R a5 ~R a6 As for each, an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is preferred, and an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 3 carbon atoms is more preferred.

[0123] Specific examples of cations represented by formula (A2) include, but are not limited to, the cations represented by formulas (A2-1) to (A2-6) below.

[0124]

[0125] In the cation represented by formula (A3), R a7 ~R a8 These are, independently, a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, and -L2-OR z2 (L2 represents an alkylene group with 1 to 4 carbon atoms, R z2 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), -L3-SO3H (L3 represents an alkylene group having 1 to 4 carbon atoms), benzyl group, -L4-SiOR z3 (L4 represents an alkylene group with 1 to 4 carbon atoms, R z3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ) is preferred, and an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 3 carbon atoms is more preferred.

[0126] R a9 Preferably, the members are a hydrogen atom and an alkyl group having 1 to 4 carbon atoms, and more preferably a hydrogen atom and a methyl group.

[0127] Specific examples of cations represented by formula (A3) include, but are not limited to, the cations represented by formulas (A3-1) to (A3-22) below.

[0128]

[0129] In the cation represented by formula (A4), R a10 ~R a11 As for each, an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is preferred, and an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 3 carbon atoms is more preferred.

[0130] Specific examples of cations represented by formula (A4) include, but are not limited to, the cations represented by the following formulas (A4-1) to (A4-2).

[0131]

[0132] In the compound represented by formula (A5), R a12~R a13 As for each, an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is preferred, and an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 3 carbon atoms is more preferred.

[0133] A specific example of a cation represented by formula (A5) is the cation represented by formula (A5-1) below, but it is not limited to this.

[0134]

[0135] In the cation represented by formula (A6), R a14 ~R a17 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, and -L5-OR z4 (L5 represents an alkylene group with 1 to 4 carbon atoms, R z4 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A cycloalkyl group or benzyl group having 5 to 6 carbon atoms is preferred, and a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group is more preferred.

[0136] Specific examples of cations represented by formula (A6) include, but are not limited to, the cations represented by the following formulas (A6-1) to (A6-10).

[0137]

[0138] In the cation represented by formula (A7), R a18 Examples include hydrogen atoms, C1-C8 alkyl groups, C2-C8 alkenyl groups, -L6-OR z5 (L6 represents an alkylene group with 1 to 4 carbon atoms, R z5 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ) or represents a benzyl group, R z6 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ) is preferred, and a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 3 carbon atoms is more preferred.

[0139] R a19 ~R a21Each of these independently consists of a hydrogen atom, a C1-C8 alkyl group, a phenyl group, or -L9-OR z7 (L9 represents an alkylene group with 1 to 4 carbon atoms, R z7 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ) is preferred, and a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or -L9-OR z7 (L9 represents an alkylene group with 1 to 4 carbon atoms, R z7 (where represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.) is more preferable.

[0140] Specific examples of cations represented by formula (A7) include, but are not limited to, the cations represented by the following formulas (A7-1) to (A7-9).

[0141]

[0142] In the cation represented by formula (A8), R a22 ~R a24 These are, independently, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, and -L. 10 -OR z8 (L 10 R represents an alkylene group with 1 to 4 carbon atoms. z8 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. A cycloalkyl group or benzyl group having 5 to 6 carbon atoms is preferred, and a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is more preferred.

[0143] Specific examples of cations represented by formula (A8) include, but are not limited to, the cations represented by the following formulas (A8-1) to (A8-3).

[0144]

[0145] Specific examples of anions represented by formula (B1) include, but are not limited to, the anions represented by the following formulas (B1-1) to (B1-2).

[0146]

[0147] Specific examples of anions represented by formula (B2) include, but are not limited to, the anions represented by formulas (B2-1) to (B2-6) below.

[0148]

[0149] Specific examples of anions represented by formula (B3) include, but are not limited to, the anions represented by the following formulas (B3-1) to (B3-3).

[0150]

[0151] In the present invention, the salt is preferably a salt comprising any cation represented by formulas (A1) to (A4), (A6), and (A7) and any anion represented by formulas (B1) to (B3) and (B6) to (B10).

[0152] Topological polar surface area (TPSA) is a value obtained by rapidly approximating the polar surface area (PSA) of a molecule. The TPSA can be easily calculated, for example, using an algorithm incorporated into general-purpose chemical structure drawing software such as ChemDraw or an algorithm incorporated into RDKit. In this invention, unless otherwise specified, the TPSA refers to the value calculated by the algorithm incorporated into RDKit. The algorithm incorporated into RDKit uses the calculation method described in J Med. Chem. 43:3714-3717, (2000).

[0153] In this invention, the TPSA is required to be 1 or more. Preferably, the TPSA is 1 or more and 150 or less, and more preferably 1 or more and 120 or less.

[0154] MolLogP is an index that expresses the hydrophilic and hydrophobic properties of a chemical structure, and is sometimes called the hydrophilic / hydrophobic parameter. LogP values ​​can be calculated using software such as ChemBioDraw Ultra or HSPiP (Ver. 4.1.07), or using the algorithm incorporated into RDKit. They can also be determined experimentally using methods such as those described in OECD Guidelines for the Testing of Chemicals, Sections 1, Test No. 117. In this invention, unless otherwise specified, the above MolLogP refers to the value calculated using the algorithm incorporated into RDKit. The algorithm incorporated into RDKit uses the calculation method described in Wildman and Crippen JCICS 39:868-873 (1999).

[0155] In this invention, MolLogP (カチオン) -MolLogP (アニオン) The difference between the MolLogP of the cation and the MolLogP of the anion (ΔMolLogP) must be greater than -3.0. Preferably, ΔMolLogP is greater than -3.0 and 18.0 or less, and more preferably greater than -3.0 and 16.0 or less.

[0156] In this invention, by using salts that satisfy the above-mentioned TPSA and ΔMolLogP, the dispersibility of the metal oxide nanoparticles can be improved, and the charge transport properties of the resulting charge transport thin film can be improved.

[0157] The content of the above salt is not particularly limited, but is preferably 0.01 to 90% by mass of the solid content, more preferably 0.1 to 60% by mass, even more preferably 0.3 to 40% by mass, and most preferably 0.5 to 20% by mass. However, regardless of whether the salt is in solid or liquid form, it is treated as solid content in the charge transport ink composition.

[0158] [Organic solvent] The charge-transporting ink composition of the present invention contains an organic solvent. Such organic solvents are not particularly limited as long as they disperse or dissolve solid components. Specific examples include, for example, alcoholic solvents such as methanol, ethanol, n-propanol, i-propanol, n-butanol, 1-octanol, 1-nonanol, 1-decanol, tetrahydrofurfuryl alcohol, terpineol, cyclohexanol, diacetone alcohol, benzyl alcohol, 2-phenoxyethanol, and 2-benzyloxyethanol; ethylene glycol, propylene glycol, 2-methyl-2,4-pentanediol, 1,3-octylene glycol, diethylene glycol, and dipropylene glycol. Glycol solvents such as triethylene glycol, tripylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, and 3-methyl-1,5-pentanediol; ketone solvents such as acetone, acetylacetone, methyl ethyl ketone, diethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, 4-hydroxy-4-methyl-2-pentanone, 2-heptanone, cyclohexanone, methylcyclopentanone, and isophorone;Dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-hexyl acetate, benzyl acetate, 2-hydroxyethyl acetate, methyl lactate, ethyl lactate, methyl propionate, ethyl propionate, propyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dimethyl adipate, diethyl adipate, dipropyl adipate, diisopropyl malonate, dimethyl sebacate, diethyl sebacate, methyl benzoate, ethyl benzoate, butyl benzoate, dimethyl phthalate, di oxalate Ester solvents such as ethyl oxalate, dibutyl oxalate, diethyl fumarate, ethylene glycol monomethyl ether acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, triacetin, γ-butyrolactone, etc.; ether solvents such as dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, anisole, 4-methoxytoluene, etc.Glycol ether-based solvents such as ethylene glycol monoethyl ether, ethylene glycol monopropyl 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, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol butyl ether. Substrates; amide solvents such as N-methylformamide, N-methylacetamide, N-methylformanilide, N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylisobutylamide, N-methyl-2-pyrrolidone, N-ethylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone; aromatic or halogenated aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, cyclohexylbenzene, chlorobenzene, tetralin, and decylbenzene; aliphatic hydrocarbon solvents such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, i-octane, i-nonane, and i-decane; halogenated hydrocarbon solvents such as methylene chloride, dichloromethane, 1,2-dichloroethane, and chloroform; cyano solvents such as acetonitrile and 3-methoxypropionitrile;A suitable solvent can be selected from among sulfoxide-based solvents such as dimethyl sulfoxide. In this invention, alcohol-based solvents, glycol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents are preferred, with methanol, ethanol, 1-octanol, 1-nonanol, 1-decanol, terpineol, ethylene glycol, 2-methyl-2,4-pentanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, isophorone, propylene carbonate, dibutyl maleate, diethyl sebacate, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol butyl ether being more preferred. These organic solvents can be used individually or in combination of two or more.

[0159] Furthermore, when forming a thin film using a charge-transporting ink composition, a composition that ensures uniform film thickness is required. In particular, when forming a film using an inkjet method, compositions containing only low-boiling-point solvents may make it difficult to obtain a flat layer depending on the usage conditions. In such cases, using a high-boiling-point solvent can suppress the evaporation of the solvent and reduce the rate of ink convection and viscosity increase, thus allowing for the acquisition of a flat layer. Considering this, it is preferable to include at least one organic solvent with a boiling point of 200°C or higher among the organic solvents mentioned above, and more preferably at least one organic solvent with a boiling point of 230°C or higher. The upper limit of the boiling point is not particularly limited, but is usually 330°C or lower. When an organic solvent with a boiling point of 200°C or higher is included, its content is not particularly limited, but is preferably 20% by mass or more of the total organic solvent.

[0160] The charge-transporting ink composition of the present invention is optimal when using only organic solvents as the solvent. In this case, "only organic solvents" means that only organic solvents are used, and does not negate the presence of trace amounts of "water" contained in the organic solvent or solid components used.

[0161] The charge-transporting ink composition of the present invention comprises the above-mentioned metal oxide nanoparticles and an organic solvent, but may also contain a binder resin as described below if necessary to further improve the flatness and charge transport properties of the resulting thin film.

[0162] The binder resin is not particularly limited as long as it is dispersed or dissolved in at least one solvent used in the charge transport ink composition, and polymer materials can be used as binders. By blending metal oxide nanoparticles with the binder resin, excellent film-forming properties and stable film formation can be easily achieved. Note that at least one type of binder resin is sufficient, and the number of types is not particularly limited.

[0163] Specific examples of such materials include polystyrene, polyimide, polycarbonate, acrylic resin, and inert resins, but are not particularly limited.

[0164] Furthermore, the binder resin may have charge-transporting properties, or charge-transporting materials may be mixed into the binder resin. In these cases, the conductivity of the electron transport layer can be improved compared to when the binder resin is insulating. Although metal oxide nanoparticles themselves have sufficient charge-transporting properties, when minute nanoparticles are uniformly dispersed in the binder at a low concentration, the charge carried by the nanoparticles may not be effectively transported. Therefore, by using a material with charge-transporting properties as a component of the electron transport layer other than metal oxide nanoparticles, the high charge-transporting properties of metal oxide nanoparticles can be further effectively utilized.

[0165] When the charge-transporting ink composition of the present invention contains a binder resin, its content is usually about 1 to 90% by mass of the solid content. However, considering the balance between improving the flatness of the resulting thin film and suppressing the decrease in charge transport performance, it is preferably about 3 to 80% by mass, more preferably about 5 to 70% by mass, and even more preferably about 10 to 60% by mass.

[0166] The charge-transporting ink composition of the present invention may contain an organic silane compound or a phosphate ester compound. By including such an organic silane compound or phosphate ester compound in the charge-transporting ink composition, when the charge-transporting thin film obtained from the ink composition is used as an electron transport layer in an organic EL element or a quantum dot EL element, the flatness of the resulting thin film can be improved, and the electron transport to the light-emitting layer provided in contact with it can be improved.

[0167] As the organosilane compound, alkoxysilanes are preferred, and trialkoxysilanes and tetraalkoxysilanes are more preferred. Examples of the above alkoxysilanes include tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, and the like. In the present invention, among these, tetraethoxysilane (TEOS), tetramethoxysilane, and tetraisopropoxysilane can be suitably used. These organosilane compounds can be used individually or in combination of two or more. Furthermore, these organosilane compounds can be used in combination with the phosphate ester compounds described later.

[0168] As phosphate ester compounds, compounds represented by the following formulas (1) to (3) are preferred, and polyoxyethylene alkyl ether phosphate esters represented by the following formula (1) are more preferred. As the above polyoxyethylene alkyl ether phosphate ester, for example, the terminal alkyl group (Y) in the following formula (1) 1Examples of phosphate esters include those exhibiting an alkyl group having 6 to 15 carbon atoms. Examples of commercially available phosphate ester compounds include those manufactured by Toho Chemical Industry Co., Ltd., trade names Phosphanol RA-600, RS-410, RS-610, RS-710, etc. These phosphate ester compounds can be used individually or in combination of two or more. Furthermore, these phosphate ester compounds can be used in combination with organosilane compounds.

[0169]

[0170] In formulas (1) to (3), X 1 , X 2 and X 3 Each of the following independently represents an alkylene group having 2 to 20 carbon atoms, f, h, and j each independently represent an integer from 1 to 100, e, g, and i each independently represent an integer from 1 to 3, and Y 1 , Y 2 and Y 3 Each of these independently represents a hydrogen atom, a C1-C20 alkyl group, a C2-C20 alkenyl group, a C6-C30 aryl group, or a (meth)acrylic group.

[0171] Alkylene groups having 2 to 20 carbon atoms can be linear, branched, or cyclic. Specific examples include methylmethylene, dimethylmethylene, ethylene, 1,2-dimethylethylene, tetramethylethylene, trimethylene, propylene, tetramethylene, pentamethylene, hexamethylene, 1,2-cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene.

[0172] The alkyl group having 1 to 20 carbon atoms can be linear, branched, or cyclic. Specific examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n Examples include linear or branched alkyl groups having 1 to 20 carbon atoms, such as n-octadecyl, n-nonadecyl, and n-eicosanyl groups; and cyclic alkyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, bicyclobutyl, bicyclopentyl, bicyclohexyl, bicycloheptyl, bicyclooctyl, bicyclononyl, and bicyclodecyl groups.

[0173] Examples of alkenyl groups having 2 to 20 carbon atoms include ethenyl group, n-1-propenyl group, n-2-propenyl group, 1-methylethenyl group, n-1-butenyl group, n-2-butenyl group, n-3-butenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, 1-methyl-1-propenyl group, 1-methyl-2-propenyl group, n-1-pentenyl group, n-1-decenyl group, and n-1-eicocenyl group.

[0174] Examples of aryl groups having 6 to 30 carbon atoms include phenyl group, tolyl group, 1-naphthyl group, 2-naphthyl group, 1-anthryl group, 2-anthryl group, 9-anthryl group, 1-phenanthryl group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl group, 9-phenanthryl group, biphenyl-2-yl group, biphenyl-3-yl group, and biphenyl-4-yl group.

[0175] When the charge-transporting ink composition of the present invention contains an organic silane compound or a phosphate ester compound, the content thereof is usually about 0.1 to 50% by mass of the solid content. However, considering the balance between improving the flatness of the resulting thin film and suppressing the decrease in charge transport performance, it is preferably about 0.5 to 40% by mass, more preferably about 0.8 to 30% by mass, and even more preferably about 1 to 20% by mass.

[0176] The viscosity of the charge-transporting ink composition 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 ink composition of the present invention can be adjusted by changing the type and ratio of organic solvents used, the solid content concentration, etc., taking into consideration various factors such as the dispersibility of metal oxide nanoparticles, the application method used, and the desired film thickness.

[0177] Furthermore, the solid content concentration of the charge-transporting ink composition of the present invention is set appropriately considering the viscosity and surface tension of the charge-transporting ink composition, the thickness of the thin film to be produced, etc., but is usually around 0.1 to 30% by mass, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of suppressing aggregation of charge-transporting substances and metal oxide nanoparticles in the ink composition.

[0178] When preparing the charge-transporting ink composition of the present invention, metal oxide nanoparticles, organic solvents, and optionally binder resins, organosilane compounds, phosphate ester compounds, etc., can be mixed in any order, as long as the solid components are uniformly dissolved or dispersed in the solvent. When other components are included, for example, a method can be used in which the other components or their solutions are added in advance to a metal oxide nanoparticle sol dispersed in the solvent. The above method can be used as long as the solid components are uniformly dissolved or dispersed in the solvent. When using binder resins, organosilane compounds, or phosphate ester compounds, they can be dissolved at any time in the above method. Note that metal oxide nanoparticles may aggregate or precipitate when mixed, depending on the type and amount of other components mixed with them. When preparing the charge-transporting ink composition, heating may be used as appropriate, as long as the components do not decompose or deteriorate.

[0179] In the present invention, the charge-transporting ink composition may be filtered using a sub-micrometer-order filter or the like during the manufacturing process of the charge-transporting ink composition or after all components have been mixed, in order to obtain a thin film with higher flatness and reproducibility.

[0180] A charge-transporting thin film can be formed on a substrate by applying the charge-transporting ink composition described above onto a substrate and evaporating the organic solvent from the resulting coating film by appropriate means such as firing or vacuum drying.

[0181] The method of applying the ink composition is not particularly limited and includes methods such as dipping, spin coating, transfer printing, roll coating, brush coating, inkjet, spraying, and slit coating. It is preferable to adjust the viscosity and surface tension of the ink composition according to the application method.

[0182] Furthermore, when using the charge-transporting ink composition of the present invention, the firing atmosphere is not particularly limited, and a thin film with a uniform film surface and high charge transport properties can be obtained not only in an atmospheric atmosphere but also in an inert gas such as nitrogen or in a vacuum. The firing temperature is appropriately set within a range of about 80 to 260°C, taking into consideration the application of the thin film obtained, the degree of charge transport properties to be imparted to the thin film obtained, the type of solvent and its boiling point, etc. However, when the thin film obtained is used as an electron transport layer for organic EL elements or quantum dot EL elements, a temperature of about 100 to 250°C is preferred. In addition, two or more temperature changes may be made during firing in order to achieve higher uniformity of film formation or to promote the reaction on the substrate, and heating can be carried out using appropriate equipment such as a hot plate, oven, or vacuum oven.

[0183] The thickness of the charge-transporting thin film is not particularly limited, but when used as a functional layer between the cathode and the light-emitting layer, such as an electron injection layer or electron transport layer in an organic EL element or quantum dot EL element, a thickness of 5 to 300 nm is preferred, and 20 to 200 nm is more preferred. Methods for changing the thickness include changing the solid content concentration in the charge-transporting ink composition or changing the amount of solution on the substrate during coating.

[0184] The organic EL element and quantum dot EL element of the present invention have a pair of electrodes, and a charge transport layer made of the charge transport thin film of the present invention is provided between these electrodes. Typical configurations of the organic EL element and quantum dot EL element are (a) to (f) below, but are not limited to these. The charge transport ink composition of the present invention can be suitably used in elements having configurations (a) to (d) among these. In the following configurations, an electron blocking layer or the like may be provided between the light-emitting layer and the anode, and a hole blocking layer or the like may be provided between the light-emitting layer and the cathode, if necessary. Furthermore, the hole injection layer, hole transport layer, or hole injection transport layer may also function as an electron blocking layer, etc., and the electron injection layer or electron transport layer may also function as a hole blocking layer, etc. Furthermore, any functional layer may be provided between each layer as necessary. (a) Anode / Hole injection layer / Hole transport layer / Emitting layer / Electron transport layer / Electron injection layer / Cathode (b) Anode / Hole injection layer / Hole transport layer / Emitting layer / Electron transport layer / Cathode (c) Anode / Hole injection layer / Emitting layer / Electron transport layer / Electron injection layer / Cathode (d) Anode / Hole injection layer / Emitting layer / Electron transport layer / Cathode (e) Anode / Hole injection layer / Hole transport layer / Emitting layer / Cathode (f) Anode / Hole injection layer / Emitting layer / Cathode

[0185] A "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 hole-transporting material is provided between the light-emitting layer and the anode, that is the "hole injection transport layer." When two or more layers of hole-transporting material are provided between the light-emitting layer and the anode, the layer closest to the anode is the "hole injection layer," and the other layers are the "hole transport layers." In particular, the hole injection (transport) layer is made of a thin film that is excellent not only in its ability to accept holes from the anode but also in its ability to inject holes into the hole transport (light-emitting) layer.

[0186] The "electron injection layer" and the "electron transport layer" are layers formed between the light-emitting layer and the cathode, and have the function of transporting electrons from the cathode to the light-emitting layer. If only one layer of electron-transporting material is provided between the light-emitting layer and the cathode, that is the "electron transport layer." If two or more layers of 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 the "electron transport layers." The "light-emitting layer" is a layer that has a light-emitting function, and may be an organic light-emitting layer or a quantum dot light-emitting layer. Correspondingly, if the light-emitting layer is an organic light-emitting layer EL element, it is an organic EL element, and if the light-emitting layer is a quantum dot light-emitting layer EL element, it is a quantum dot EL element.

[0187] A charge-transporting thin film made from the charge-transporting ink composition of the present invention can be used as a functional layer formed between the cathode and the light-emitting layer in organic EL devices and quantum dot EL devices, and is particularly suitable as an electron injection layer and an electron transport layer, and more suitable as an electron transport layer.

[0188] The following are examples of materials and manufacturing methods used when fabricating an EL element using the charge-transporting ink composition of the present invention, but are not limited to these.

[0189] An example of a method for fabricating an organic EL element or quantum dot EL element having an electron transport layer made of a thin film obtained from the charge-transporting ink composition of the present invention is as follows. It is preferable to pre-treat the electrodes by washing with alcohol, pure water, etc., or by surface treatment such as UV ozone treatment or oxygen-plasma treatment, to the extent that it does not adversely affect the electrodes. A hole injection layer and a hole transport layer are sequentially laminated on the anode substrate by a wet process using a hole injection layer forming composition containing a hole-transporting polymer or a hole transport layer forming composition. Subsequently, a light-emitting layer is laminated by a wet process using a light-emitting layer forming composition containing a light-emitting polymer or quantum dot material. Furthermore, an electron transport layer is formed by a wet process using the charge-transporting ink composition of the present invention, and a cathode metal is deposited thereon. Alternatively, instead of forming the hole injection layer, hole transport layer, and light-emitting layer by a wet process in this method, these layers can be formed by vapor deposition. If necessary, an electron blocking layer may be provided between the light-emitting layer and the hole transport layer. The above describes an example of stacking the anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, and cathode in that order (sequential structure). However, it is not limited to this, and the layers may also be stacked in that order (reverse structure): cathode, electron transport layer, light-emitting layer, hole transport layer, hole injection layer, and anode.

[0190] Examples of anode materials include transparent electrodes such as indium tin oxide (ITO) and indium zinc oxide (IZO), metallic anodes such as aluminum, or metallic anodes composed of alloys thereof, and those that have undergone planarization treatment are preferred. Polythiophene derivatives and polyaniline derivatives with high charge transport properties can also be used. Other metals that constitute the metallic anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.

[0191] Examples of hole-transporting polymers include poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), 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)], and poly[(9,9-bis{1'-pentene- Examples include, but are not limited to, poly[(5'-yl)fluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,4-diaminophenylene)], poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine]-end-capped with polysilcisquinoxane, poly[(9,9-diodioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(p-butylphenyl))diphenylamine)], etc.

[0192] Examples of luminescent polymers include, but are not limited to, polyfluorene derivatives such as poly(9,9-dialkylfluorene) (PDAF), polyphenylene vinylene derivatives such as poly(p-phenylene vinylene) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), polythiophene derivatives such as poly(3-alkylthiophene) (PAT), and polyvinylcarbazole (PVCz).

[0193] As a quantum dot material, it may include at least one semiconductor material selected from the group consisting of II-VI semiconductors, III-V semiconductors, I-III-VI semiconductors, IV semiconductors, and I-II-IV-VI semiconductors. Specific examples of the above semiconductor materials include, for example, CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSte, ZnSeS, ZnSeTe, ZnSte, HgSeS, HgSeTe, HgSte, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, CdHgZnT e, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe; GaN, GaP, GaAs, G aSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, Ga InNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb; SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnS Examples include, but are not limited to, eS, SnSeTe, SnSte, PbSeS, PbSeTe, PbSte, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSte; Si, Ge, SiC, SiGe, AgInSe2, CuGaSe2, CuInS2, CuGaS2, CuInSe2, AgInS2, AgGaSe2, AgGaS2, C, Si, and Ge.

[0194] Materials for forming the hole injection layer include copper phthalocyanine, titanium dioxide phthalocyanine, platinum phthalocyanine, pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrine, N,N,N',N'-tetrakis(4-methoxyphenyl)benzidine, 2,7-bis[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene, 2,2'-bis[N,N-bis(4-methoxyphenyl)amino]-9,9-spirobifluorene, N,N'-diphenyl-N,N'-di[4-(N,N-ditolylamino)phenyl]benzidine, N,N'-diphenyl-N,N'-di[4-(N,N-diphenylamino)phenyl]benzidine, N 4 , N 4 '-(biphenyl-4,4'-diyl)bis(N 4 , N 4 ', N 4 '-triphenylbiphenyl-4,4'-diamine)N 1 , N 1 '-(biphenyl-4,4'-diyl)bis(N 1 -phenyl-N 4 , N 4'-di-m-tolylbenzene-1,4-diamine), International Publication No. 2004 / 043117, International Publication No. 2004 / 105446, International Publication No. 2005 / 000832, International Publication No. 2005 / 043962, International Publication No. 2005 / 042621, International Publication No. 2005 / 107335, International Publication No. 2006 / 006459, International Publication No. 2006 / 025342, International Publication No. 2006 / 137473, International Publication No. 2007 / 049631, International Publication No. 2007 / 099808, International Publication No. 2008 / 010474, International Publication No. 2008 / 03 Examples of charge transport materials, etc., described in International Publication No. 2617, International Publication No. 2008 / 032616, International Publication No. 2008 / 129947, International Publication No. 2009 / 096352, International Publication No. 2010 / 041701, International Publication No. 2010 / 058777, International Publication No. 2010 / 058776, International Publication No. 2013 / 042623, International Publication No. 2013 / 129249, International Publication No. 2014 / 115865, International Publication No. 2014 / 132917, International Publication No. 2014 / 141998, and International Publication No. 2014 / 132834 include, but are not limited to, these.

[0195] Examples of materials that form the hole transport layer include, but are not limited to, (triphenylamine) dimer derivatives, [(triphenylamine) dimer] spirodimer, N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-benzidine (α-NPD), triarylamines such as 4,4',4"-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA), 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).

[0196] Examples of materials for forming the luminescent layer include, but are not limited to, low molecular weight luminescent materials such as metal complexes of 8-hydroxyquinoline such as aluminum complexes, metal complexes of 10-hydroxybenzo[h]quinoline, bisstyrylbenzene derivatives, bisstyrylarylene derivatives, metal complexes of (2-hydroxyphenyl)benzothiazole, and silole derivatives; and systems in which luminescent materials and electron transfer materials are mixed with polymer compounds such as poly(p-phenylenevinylene), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], poly(3-alkylthiophene), and polyvinylcarbazole. Furthermore, when forming the luminescent layer by vapor deposition, it may be co-deposited with a luminescent dopant. Examples of luminescent dopants include, but are not limited to, metal complexes such as tris(2-phenylpyridine)iridium(III) (Ir(ppy)3), naphthacene derivatives such as rubrene, quinacridone derivatives, and condensed polycyclic aromatic rings such as perylene.

[0197] Examples of cathode materials include, but are not limited to, aluminum, magnesium-silver alloys, and aluminum-lithium alloys. Examples of materials for forming the electron blocking layer include, but are not limited to, tris(phenylpyrazole)iridium.

[0198] The materials that make up the anode, cathode, and the layer formed between them differ depending on whether the device has a bottom emission structure or a top emission structure, so the materials should be selected appropriately taking this into consideration. Typically, in a bottom emission device, a transparent anode is used on the substrate side, and light is extracted from the substrate side, whereas in a top emission device, a reflective anode made of metal is used, and light is extracted from the transparent electrode (cathode) side, which is opposite to the substrate. For example, when manufacturing anode materials, a transparent anode such as ITO is used when manufacturing a bottom emission device, and a reflective anode such as Ag alloy or Al alloy is used when manufacturing a top emission device.

[0199] To prevent deterioration of characteristics, the organic EL element of the present invention may be sealed together with a water-absorbing agent or the like, as necessary, according to standard procedures.

[0200] As described above, the charge-transporting ink composition of the present invention is suitably used for forming a functional layer between the cathode and the light-emitting layer of organic EL elements and quantum dot EL elements. However, it can also be used for forming charge-transporting thin films in other electronic elements such as organic photoelectric devices, organic thin-film solar cells, organic perovskite photoelectric devices, organic integrated circuits, organic field-effect transistors, organic thin-film transistors, organic light-emitting transistors, organic optical inspectors, organic photoreceptors, organic electric field quenching elements, light-emitting electrochemical batteries, quantum lasers, organic laser diodes, and organic plasma light-emitting elements. In particular, it can be suitably used in organic EL elements and quantum dot EL elements.

[0201] The present invention will be described in more detail below with reference to manufacturing examples, embodiments, and comparative examples, but this will not limit the present invention. The apparatus used in the embodiments is as follows.

[0202] (1) Evaluation device for average particle size by dynamic light scattering: Zetasizer NanoS, manufactured by Malvern Instruments Ltd. (2) Spin coating device: Spin Coater MS-A100, manufactured by Mikasa Corporation

[0203] Furthermore, the compounds 1 to 13 used in the examples are as follows. Compound 1: Compound represented by formula (C1) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 2: Compound represented by formula (C2) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 3: Compound represented by formula (C3) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 4: Compound represented by formula (C4) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 5: Compound represented by formula (C5) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 6: Compound represented by formula (C6) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 7: Compound represented by formula (C7) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 8: Compound represented by formula (C8) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 9: Compound represented by formula (C9) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 10: Compound represented by formula (C10) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 11: Compound represented by formula (C11) (manufactured by Tokyo Chemical Industry Co., Ltd.) Compound 12: Compound represented by formula (C12) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Compound 13: Compound represented by formula (C13) (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0204]

[0205] [1] Synthesis of oxide nanoparticles for charge transport ink compositions [Production Example 1] Magnesium zinc oxide nanoparticles were synthesized by the method described in Chem. Commun., 2019, 55, 13299-13302, to obtain a magnesium zinc oxide nanoparticle ethanol solution (120 g, 3.63% by mass).

[0206] [2] Preparation of charge-transporting ink composition [Example 1-1] To 1.64 g of the zinc magnesium nanoparticle ethanol solution prepared in Production Example 1 (0.06 g as ZnMgO), 2.36 g of ethanol and 0.0006 g of compound 1 as an additive (salt) (1% by mass relative to ZnMgO) were added and stirred at room temperature for 1 hour. The mixture was then filtered through a PTFE syringe filter with a pore size of 0.2 μm to prepare a charge-transporting ink composition.

[0207] [Examples 1-2 to 1-13] Charge transport ink compositions were prepared in the same manner as in Example 1-1, except that compounds 2 to 13 were used instead of compound 1.

[0208] [Comparative Example 1-1] A charge-transporting ink composition was prepared in the same manner as in Example 1-1, except that compound 1 was not added.

[0209] [3] Fabrication and Evaluation of Electron-Only Devices (EODs) [Example 2-1] The charge-transporting ink composition prepared in Example 1-1 was applied to an ITO substrate using a spin coater, and then pre-fired at 100°C for 30 seconds in an air atmosphere. Next, it was fully fired at 140°C for 15 minutes to form a 40 nm thin film on the ITO substrate. As the ITO substrate, a 25 mm × 25 mm × 0.7 t glass substrate with a patterned 50 nm thick ITO film formed on its surface was used, and impurities on the surface were removed using an O2 plasma cleaning device (150 W, 30 seconds) before use. On top of this, a deposition device (vacuum degree 1.0 × 10 -5 An 80 nm thick aluminum thin film was formed using Pa at a rate of 0.2 nm / second. Subsequently, to prevent degradation of properties due to the effects of oxygen and water in the air, it was sealed with a sealing substrate. The sealing was performed using the following procedure: In a nitrogen atmosphere with an oxygen concentration of 2 ppm or less and a dew point of -76°C or less, the ITO substrate was placed between the sealing substrates, and the sealing substrates were bonded together with an adhesive (Moresco Moisture Cut WB90US(P), manufactured by Moresco Corporation). At this time, a water-retaining agent (HD-071010W-40, manufactured by Dainippon Hazard Co., Ltd.) was placed inside the sealing substrate along with the ITO substrate. The bonded sealing substrate was then irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm²). 2 After that, the adhesive was cured by annealing at 80°C for 1 hour. This was designated as an electron-only device (EOD).

[0210] [Examples 2-2 to 2-13, Comparative Example 2-1] Electron-only devices (EODs) were fabricated in the same manner as in Example 2-1, except that the charge-transporting ink compositions prepared in Examples 1-2 to 1-13 and Comparative Example 1-1 were used instead of the charge-transporting ink composition prepared in Example 1-1.

[0211] The current density was measured for the EODs prepared in Examples 2-1 to 2-13 and Comparative Example 2-1 when a voltage of 1V was applied for 0.01 seconds. The results are shown in Table 1.

[0212]

[0213] As shown in Table 1, the charge-transporting thin film formed from the charge-transporting ink composition of the present invention was found to have sufficient charge transport properties, as evidenced by the current density values ​​when a voltage was applied. Furthermore, compared to the comparative example, the charge-transporting thin film in the example using the above-mentioned salt as an additive showed a higher current density value, indicating improved charge transport properties. This is thought to be because the use of the additive improved the energy level compatibility between the charge-transporting thin film and Al or ITO, resulting in improved electron injection.

[0214] [4] Evaluation of average particle size by dynamic light scattering [Example 3-1] The average particle size of metal oxide nanoparticles contained in the charge-transporting ink composition prepared in Example 1-1 was measured by dynamic light scattering using solvent parameters. In addition, the charge-transporting ink composition was diluted with a dispersion solvent as needed when measuring the average particle size.

[0215] [Examples 3-2 to 3-13, Comparative Example 3-1] The average particle size was measured by dynamic light scattering in the same manner as in Example 3-1, except that the charge-transporting ink composition prepared in Examples 2-2 to 2-13 and Comparative Example 1-1 was used instead of the charge-transporting ink composition prepared in Example 1-1.

[0216] The average particle size measured by dynamic light scattering in Examples 3-1 to 3-13 and Comparative Example 3-1 is shown in Table 2.

[0217]

[0218] As shown in Table 2, the average particle size of the metal oxide nanoparticles in the charge-transporting ink composition of the present invention was found to be smaller than that of the comparative example. This is thought to be because the additive contained in the charge-transporting ink composition of the present invention caused an electrical double layer to form on the metal oxide nanoparticles, which increased the charge repulsion between particles and, as a result, suppressed aggregation between particles.

[0219] [5] Evaluation of QDEL element fabrication [Example 4-1] First, an ITO substrate (Foresight Co., Ltd., product name ITO (50nm) Zebra Substrate ver2.0, a 25mm x 25mm x 0.7mm glass substrate with a 50nm thick ITO film patterned on its surface) was prepared by removing impurities from the substrate surface using an O2 plasma cleaning apparatus at 150W for 30 seconds. A PEDOT:PSS aqueous dispersion (Heraeus, product name Clevios™) was applied to it as a hole injection layer (HIL) using a spin coater, and then pre-fired at 80°C for 1 minute in an air atmosphere. Next, it was fully fired at 150°C for 30 minutes to form a 30nm HIL thin film on the ITO substrate. Next, a PVK (polyvinylcarbazole, model number 368350, average molecular weight 25,000-50,000, manufactured by Aldrich) dissolved in chlorobenzene (manufactured by Junsei Chemical Co., Ltd.) at a concentration of 0.5 mass% was applied to the HIL thin film as a hole transport layer (HTL) using a spin coater. The film was then fired at 200°C for 30 minutes under a nitrogen atmosphere to form a 20 nm HTL thin film on the HIL thin film. Next, a quantum dot dispersion (QNA, product name PureBlue.dots in Toluene_v2, toluene dispersion, concentration 3 mass%) was applied to the HTL thin film as an emissive layer (EmL) using a spin coater. The film was then fired at 100°C for 10 minutes under a nitrogen atmosphere to form a 40 nm EmL thin film on the HTL thin film. Next, the charge-transporting ink composition of Example 1-1 was applied to the EmL thin film as an electron transport layer (ETL) using a spin coater, and then calcined at 100°C for 30 seconds under a nitrogen atmosphere. Then, it was fully calcined at 140°C for 15 minutes to form a 40 nm ETL thin film on the EmL thin film. On the surface of the obtained ETL thin film, a vacuum of 1.0 × 10⁻⁶ was applied using a vapor deposition apparatus. -5A thin aluminum film with a thickness of 80 nm was formed at Pa and a pressure of 0.2 nm / second. Subsequently, to prevent degradation of properties due to the effects of oxygen, water, etc. in the air, the ITO substrate with the formed aluminum film and a water-trapping agent (manufactured by Dynic Corporation, product name HD-071010W-40) were placed between a sealing substrate (manufactured by Premium Glass Co., Ltd., cell size 19 mm x 21 mm x 0.7 mm, recess depth 0.4 mm or more) in a nitrogen atmosphere with an oxygen concentration of 2 ppm or less and a dew point of -76°C or less. The sealing substrate was then bonded together with an adhesive (manufactured by MORESCO Corporation, product name Moresco Moisture Cut WB90US(P)). The bonded sealing substrate was irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm²). 2 After that, the adhesive was cured by annealing at 80°C for 1 hour to obtain a QDEL element that emits blue light.

[0220] [Examples 4-2 to 4-13] QDEL elements exhibiting blue light emission were fabricated in the same manner as in Example 4-1, except that the charge transport ink compositions prepared in Examples 1-2 to 1-13 were used instead of the charge transport ink composition prepared in Example 1-1.

[0221] For the QDEL elements fabricated in Examples 4-1 to 4-13, the current density and luminescence intensity were measured when voltages from 0 to 12V were applied for 0.01 seconds at 0.25V intervals under 25°C and atmospheric pressure. From the obtained measurement data, the voltage, current efficiency, and external quantum efficiency at which 50 cd of luminescence was observed were determined. The external quantum efficiency is given by the following formula (3): External quantum efficiency = 8.06 × 10⁻⁶ 5 ×P × λ / I ...Equation (3) (where P is the luminescence intensity [W / m 2 ], where λ is the wavelength [m] and I is the current [A]. Calculated by ). The results of TPSA and ΔMolLogP are shown in Table 3, and the voltage, current efficiency and external quantum efficiency when 50 cd of emission was observed are shown in Table 4.

[0222]

[0223]

[0224] As shown in Tables 3 and 4, the evaluation results of the QDEL element showed that blue light emission was observed from the QD used as EmL, indicating that the charge-transporting ink composition of the present invention can be used as an electron transport layer.

Claims

1. Metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi and Sr, and one or more metal oxide nanoparticles selected from the group consisting of composites of at least two of these, a salt comprising any cation represented by the following formulas (A1) to (A8) and any anion represented by the following formulas (B1) to (B14), having a topological polar surface area (TPSA) of 1 or more, and MolLogP z2 -MolLogP (アニオン) A salt in which the difference (ΔMolLogP) between the MolLogP of the cation and the MolLogP of the anion represented by is greater than -3.0, and an organic solvent. <000,0044> [In formula (A1), R a1 ~R a4 are each independently a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, -L1-OR z1 (L1 represents an alkylene group having 1 to 4 carbon atoms, and R z1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), a cycloalkyl group having 3 to 8 carbon atoms, a benzyl group or a phenethyl group. In formula (A2), R a5 ~R a6 each independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms. In formula (A3), R a7 ~R a8 are each independently a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, -L2-OR z2 (L2 represents an alkylene group having 1 to 4 carbon atoms, and R z2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), -L3-SO3H (L3 represents an alkylene group having 1 to 4 carbon atoms.), a benzyl group or -L4-SiOR z3 (L4 represents an alkylene group having 1 to 4 carbon atoms, and R z3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.), and R a9 represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. In formula (A4), R a10 ~R a11 Each of these independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms. In formula (A5), R a12 ~R a13 Each of these independently represents an alkyl group having 1 to 16 carbon atoms or an alkenyl group having 2 to 16 carbon atoms. In formula (A6), R a14 ~R a17 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, and -L5-OR z4 (L5 represents an alkylene group with 1 to 4 carbon atoms, R z4 R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), ), represents a cycloalkyl group having 3 to 8 carbon atoms or a benzyl group. In formula (A7), R a18 This consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, an alkenyl group having 2 to 16 carbon atoms, and -L6-OR z5 (L6 represents an alkylene group with 1 to 4 carbon atoms, R z5 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), -L7-SO3H (L7 represents an alkylene group having 1 to 4 carbon atoms), a benzyl group or -L8-SiOR z6 (L8 represents an alkylene group with 1 to 4 carbon atoms, R z6 R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. a19 ~R a21 Each of these independently consists of a hydrogen atom, a C1-C8 alkyl group, a phenyl group, or -L9-OR z7 (L9 represents an alkylene group with 1 to 4 carbon atoms, R z7 R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. In formula (A8), R a22 ~R a24 Each of these independently consists of a hydrogen atom, an alkyl group having 1 to 16 carbon atoms, a phenyl group, and -L. 10 -OR z8 (L 10 R represents an alkylene group with 1 to 4 carbon atoms. z8 ) represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. ), ), represents a cycloalkyl group or benzyl group having 3 to 8 carbon atoms. (In formula (B1), R b1 ~R b2 Each of these independently represents either a fluorine atom or a trifluoromethyl group. In formula (B2), R b3 R represents a hydroxyl group, a carbon-1 to carbon-4 alkoxy group, a carbon-1 to carbon-4 alkyl group, a trifluoromethyl group, or a p-toluenesulfonyl group. In formula (B3), R b4 ~R b5 Each of these independently represents an alkyl group having 1 to 4 carbon atoms, and each of these independently represents either an oxygen atom or a sulfur atom.

2. The charge transport ink composition according to claim 1, wherein the metal oxide nanoparticles are one or more particles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Zr, Sn, and Ga, and composites of at least two of these.

3. The charge transport ink composition according to claim 2, wherein the metal oxide nanoparticles are one or more particles selected from the group consisting of metal oxides selected from the group consisting of Zn and Mg, and composites of at least two of these.

4. The charge transport ink composition according to claim 1, wherein the metal oxide nanoparticles are particles in which one or more metal oxide nanoparticles selected from the group consisting of metal oxides selected from the group consisting of Zn, Mg, Ti, Zr, Sn, Ga, Fe, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these, form a core, and the surface of the core is coated with a metal oxide.

5. The charge transport ink composition according to claim 4, wherein the metal oxide nanoparticles are particles in which one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Zr, Sn, and Ga, and composites of at least two of these, form a core, and the surface of the core is coated with a metal oxide.

6. The charge transport ink composition according to claim 5, wherein the metal oxide nanoparticles are particles in which one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn and Mg, and composites of at least two of these, form a core, and the surface of the core is coated with a metal oxide.

7. The charge-transporting ink composition according to claim 1, wherein the salt is a salt comprising any cation represented by formulas (A1) to (A4), (A6), and (A7) and any anion represented by formulas (B1) to (B3) and (B6) to (B10).

8. A charge-transporting thin film obtained from the charge-transporting ink composition according to any one of claims 1 to 7.

9. An electronic device comprising a charge-transporting thin film according to claim 8.

10. The electronic device according to claim 9, wherein the charge-transporting thin film is an electron transport layer.

11. The electronic element according to claim 10, wherein the above-mentioned electronic element is an organic EL element.

12. The electronic element according to claim 10, wherein the above-mentioned electronic element is a quantum dot EL element.

13. A method for producing a charge-transporting thin film, characterized by applying the charge-transporting ink composition according to any one of claims 1 to 7 onto a substrate and evaporating an organic solvent.

Images