Charge-transporting ink composition

Abstract

Provided is a charge-transporting ink composition for an upper layer of a quantum dot layer, the composition being configured such that: when used to form an upper layer of a quantum dot (QD) layer (light emission layer), the changes in the flatness of the film formed by inkjet deposition can be suppressed, such changes occurring due to the post-deposition time delay; practical charge-transporting properties can be maintained; and photoluminescence (PL) quenching of the quantum dot (QD) layer in the element obtained is not triggered. The composition contains a charge-transporting material and a solvent, where the solvent is a specific solvent having a Balaban index of 3.3 or lower and a molar refractive index of 65 or lower, and also having a boiling point of 180°C or higher.

Description

Charge transport ink composition

[0001] The present invention relates to a charge transport ink composition.

[0002] Organic electroluminescence (hereinafter referred to as "organic EL") devices have attracted attention due to various advantages such as high contrast, energy saving, and flexibility, and are being put to practical use in fields such as displays and lighting. Organic EL devices use multiple functional thin films, one of which, the electron transport layer, is responsible for the exchange of charges between the cathode and the light-emitting layer, and plays an important role in achieving low-voltage operation and high brightness of the organic EL device. The hole injection layer is responsible for the exchange of charges between the anode and the hole transport layer or the light-emitting layer, and plays an important role in achieving low-voltage operation and high brightness of the organic EL device. The hole transport layer is also responsible for the exchange of charges between the hole injection layer and the light-emitting layer, and plays an important role in achieving low-voltage operation and high brightness of the organic EL device.

[0003] Methods for manufacturing organic EL devices are broadly divided into dry processes, such as vapor deposition, and wet processes, such as spin coating and inkjet printing. Comparing these processes from the perspective of increasing the area of ​​devices, wet processes can more efficiently produce films with high flatness over large areas than dry processes. Therefore, given the current demand for large-area manufacturing of organic EL devices, it is important to provide electron transport layers, hole injection materials, hole transport materials, and the like that can be formed by wet processes and have excellent functionality.

[0004] Furthermore, with the recent development of display technology, quantum dot EL elements (QDEL elements), which use quantum dot materials as their light-emitting layers, have emerged and are expected to have a wide range of applications. These quantum dot EL elements (QDEL elements) can be manufactured at low cost using wet processes, and are attracting much attention in fields such as display technology and lighting due to their characteristics such as controllability of emission wavelength, high color purity, high luminous efficiency, and flexibility.

[0005] In such EL devices, it is necessary to laminate an electron transport layer containing metal oxide nanoparticles between the light-emitting layer and the cathode to efficiently inject electrons into the light-emitting layer, and to date, various studies have been conducted on the type and primary particle size of metal oxide nanoparticles in order to improve this efficiency (Patent Documents 1 to 3).

[0006] However, when a functional layer is formed by a wet process, the photoluminescence (PL) intensity of the resulting element may decrease, which is called PL quenching, and further improvement is desired. In addition, when producing an EL element, there is a film-forming process in which ink is applied and then dried to form a film, but the flatness of the film may change depending on the delay time from ink application to drying, and further improvement is desired.

[0007] International Publication No. 2006 / 098540 Japanese Patent Application Laid-Open No. 2010-055900 International Publication No. 2009 / 084273

[0008] Chem. Phys. Lett. 89:399-404 (1982)Wildman and Crippen JCICS 39:868-73 (1999)

[0009] The present invention has been made in view of the above background, and aims to provide a charge-transporting ink composition that, when used to form an upper layer of a quantum dot (QD) layer (light-emitting layer), has practical charge-transporting properties, does not cause PL quenching of the quantum dot (QD) layer of the resulting device, and can suppress changes in film flatness due to delay times after inkjet film formation.

[0010] As a result of extensive research, the present inventors have found that a charge transporting ink composition containing a charge transporting substance and a solvent (specific solvent) that satisfies specific conditions has practical charge transport properties, that a charge transporting thin film formed as an upper layer of a QD layer by the charge transporting ink composition has practical conductivity, that PL quenching of the QD layer is not caused in a device that includes the charge transporting thin film, and that changes in the flatness of the film due to delay times after inkjet film formation can be suppressed, and have completed the present invention.

[0011] That is, the present invention provides the following charge transport ink compositions: 1. A charge transport ink composition for use as an upper layer of a quantum dot layer, comprising a charge transport material and a solvent, wherein the solvent comprises a specific solvent having a Balaban index of 3.3 or less, a molar refractive index of 65 or less, and a boiling point of 180°C or higher. 2. The charge transport ink composition of 1, wherein the specific solvent contains two or more oxygen atoms in the molecule. 3. The charge transport ink composition of 1 or 2, wherein the charge transport material is one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and complexes of at least two of these metals. 4. The charge transport ink composition of 3, wherein the metal oxide nanoparticles are surface-treated metal oxide nanoparticles whose surfaces are coated with one or more metal oxides selected from the group consisting of metal oxides and surface treatment agents. 5. 5. The charge transporting ink composition of 4, wherein the surface treatment agent is at least one selected from the group consisting of compounds represented by the following formulas (S1) to (S9): (In formula (S1), R 1s are each independently an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 are bonded to a silicon atom by a Si—C bond; R 2s each independently represents an alkoxy group, an acyloxy group, or a halogen atom, and a1 represents an integer of 1 to 3. In formulas (S2) and (S3), R 3s and R 5s are each independently an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms, and R 4s and R 6s each independently represents an alkoxy group, an acyloxy group, or a halogen atom; Y s represents an alkylene group, an NH group, or an oxygen atom, b1 represents an integer of 1 to 3, c1 represents 0 or 1, and d1 represents an integer of 1 to 3. In formula (S4), R7s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 e1 represents 1 or 2. 8s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 9s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 10s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 11s represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 12s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 13s represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; Z s represents an oxygen atom or a sulfur atom. 14seach independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 f1 represents 1 or 2. 6. Any of the charge transport ink compositions of 3 to 5, in which the metal oxide nanoparticles are ZnO, a ZnO-MgO composite, SnO2, or a SnO2-TiO2-ZrO2 composite. 7. Any of the charge transport ink compositions of 4 to 6, in which the metal oxide is at least one selected from the group consisting of In2O3, Sb2O5, SiO2, SnO2, TiO2, WO3, ZnO, ZrO2, and composites of at least two of these. 8. The charge transport ink composition of 7, in which the metal oxide is SnO2, Sb2O5, or a SnO2-SiO2 composite. 9. The charge transport ink composition of 1 or 2, wherein the charge transport material is copper(I) halide or copper(I) pseudohalide. 10. The charge transport ink composition of 9, wherein the copper(I) halide or copper(I) pseudohalide is copper(I) halide or copper(I) thiocyanate. 11. The charge transport ink composition of 9, wherein the copper(I) halide is copper(I) iodide. 12. A charge transport thin film obtained from the charge transport ink composition of any one of 1 to 11. 13. An electronic device comprising the charge transport thin film of 12. 14. The electronic device of 13, wherein the charge transport thin film is an electron transport layer or a hole transport layer. 15. The electronic device of 13 or 14, wherein the electronic device is a quantum dot EL device. 16. A method for producing a charge transport thin film, comprising applying the charge transport ink composition of any one of 1 to 11 onto a substrate and evaporating the solvent. 17. A method for producing a charge transport thin film of 16, wherein the substrate is a quantum dot layer.

[0012] The charge-transporting ink composition of the present invention can be used to obtain a charge-transporting thin film having excellent flatness and practical conductivity. This charge-transporting thin film can be suitably used as a thin film for an electronic device, as an upper layer of a quantum dot layer in a quantum dot EL device, and can suppress PL quenching in a device fabricated using the charge-transporting thin film.

[0013] The present invention will be described in more detail below. The charge-transporting ink composition of the present invention is used to form a layer above the QD layer, and is characterized by containing a charge-transporting material and a specific solvent that satisfies specific conditions. Here, the "layer above the QD layer" formed by the charge-transporting ink composition of the present invention includes not only the layer formed directly above the QD layer, but also layers formed above one or two other functional layers formed on the QD layer.

[0014] In the present invention, the "solid content" of the charge transport ink composition of the present invention refers to components other than the solvent contained in the composition. Furthermore, the term "charge transportability" in the present invention is synonymous with "electrical conductivity" and "electron transportability." The charge transport ink composition of the present invention may itself have charge transportability, or a solid film obtained by using the composition may have charge transportability.

[0015] [1] Specific Solvent In the present invention, the specific solvent means a solvent having a Balaban index of 3.3 or less, a molar refractive index of 65 or less, and a boiling point of 180° C. or more.

[0016] The Balaban index can be calculated from the molecular structure using a known program, and this value can be used to determine whether the molecules of a specific solvent have a linear or branched molecular structure. In the present invention, the Balaban index was calculated using the calculation method shown in Chem. Phys. Lett. 89:399-404 (1982) (Non-Patent Document 1).

[0017] In the present invention, from the viewpoint of suppressing PL quenching of the element, the Balaban index must be 3.3 or less, preferably 3.2 or less, more preferably 3.0 or less. The lower limit is not particularly limited, but is preferably 1.8 or more, more preferably 2.0 or more.

[0018] The molar refractive index is a value that can be calculated from the molecular structure using a known program, and this value allows the refractive index per molar mass of a molecule of a specific solvent to be determined. In the present invention, the molar refractive index was calculated using the calculation method shown in Wildman and Crippen JCICS 39:868-73 (1999) (Non-Patent Document 2).

[0019] In the present invention, from the viewpoint of suppressing PL quenching of the element, the molar refractive index needs to be 65 or less, preferably 63 or less, and more preferably 60 or less. The lower limit is not particularly limited, but is preferably 15 or more, and more preferably 20 or more.

[0020] From the viewpoint of suppressing changes in flatness due to delay time after inkjet film formation of the charge transport ink composition, the specific solvent must have a boiling point of 180° C. or higher, preferably 190° C. or higher, and more preferably 200° C. or higher. The lower limit is not particularly limited, but is preferably 350° C. or lower, and more preferably 330° C. or lower. In the present invention, by using a solvent having a boiling point within this range, evaporation of the solvent can be suppressed when forming a film using the inkjet method, and the rate of ink convection and viscosity increase can be suppressed, which is thought to result in a flat layer.

[0021] From the viewpoint of suppressing PL quenching of the device, the specific solvent preferably contains one or more oxygen atoms, more preferably two or more oxygen atoms, in the molecule, and although there is no particular upper limit, the number is preferably 5 or less, more preferably 4 or less.

[0022] Specific examples of the specific solvent include dimethyl phthalate, methanol, ethanol, isopropyl alcohol, ethylene glycol, propylene carbonate, diethylene glycol monobutyl ether acetate, triethylene glycol butyl methyl ether, tripropylene glycol, 1,2-hexanediol, diethyl phthalate, 2-phenoxyethyl isobutyrate, diethylene glycol, dipropylene glycol butyl ether, triethylene glycol, diethylene glycol monobenzyl ether, 2-[2-(2-ethylhexyloxy)ethoxy]ethanol, 1-decanol, etc. The specific solvents may be used alone or in combination of two or more.

[0023] [2] Charge Transporting Substance The charge transporting substance used in the present invention is not particularly limited and can be appropriately selected from charge transporting substances used in the fields of organic electroluminescence (EL) or quantum dot electroluminescence (EL). Examples of the charge transporting substance include metal oxide nanoparticles; various charge transporting compounds and charge transporting oligomers such as oligopyrrole; charge transporting polymers such as polyaniline derivatives and polypyrrole derivatives; copper(I) halide or pseudocopper(I) halide. In the present invention, metal oxide nanoparticles and copper(I) halide or pseudocopper(I) halide are particularly preferred.

[0024] [2-1] Metal Oxide Nanoparticles In the present invention, the metal oxide nanoparticles are composed of one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these metals. The metal oxide is preferably an oxide of a metal having a valence of 2 to 6. Nanoparticles refer to fine particles whose average particle size for primary particles is on the order of nanometers (typically 500 nm or less). The particle size can be measured by methods such as transmission electron microscopy or dynamic light scattering (DLS).

[0025] Specific examples of the metal oxides include ZnO, MgO, TiO2, Fe2O3, ZrO2, SnO2, Ta2O5, Nb2O5, YO3, MoO3, WO3, PbO, In2O3, Bi2O3, SrO, SrTiO3, BaTiO3, ZnO-MgO composite, SnO2-WO3 composite, SnO2-ZrO2 composite, and SnO2-TiO2-ZrO2 composite. Among these, ZnO, ZnO-MgO composite, SnO2, and SnO2-TiO2-ZrO2 composite are preferred in the present invention from the viewpoint of charge transport properties. These metal oxide nanoparticles may be used alone or in combination of two or more.

[0026] The primary particle diameter of the metal oxide nanoparticles is not particularly limited as long as it is nano-sized. However, in consideration of obtaining a thin film with good reproducibility and excellent flatness, the primary particle diameter is preferably 1 to 60 nm, more preferably 2 to 50 nm, and even more preferably 3 to 50 nm.

[0027] The metal oxide nanoparticles may be surface-treated metal oxide nanoparticles whose surfaces are coated with one or more selected from the group consisting of metal oxides and surface treatment agents. Coating the surfaces of the metal oxide nanoparticles with these agents makes the particles less likely to aggregate, improving their dispersibility in organic solvents. In the following description, metal oxide nanoparticles that have not been surface-treated and the surface-treated metal oxide nanoparticles may also be referred to simply as metal oxide nanoparticles.

[0028] Suitable embodiments of the surface-treated metal oxide nanoparticles include the following: (1) A nanoparticle having a core made of one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these, and the surface of the core is coated with a metal oxide; (2) A nanoparticle having a core made of one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these, and the surface of the core is coated with one or more surface treatment agents. (3) A core made of one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these metal oxides, wherein 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.

[0029] As the metal oxide coating the surface of the core, from the viewpoint of achieving both dispersibility in organic solvents and charge transport properties, at least one selected from the group consisting of In2O3, Sb2O5, SiO2, SnO2, TiO2, WO3, ZnO, ZrO2 and complexes of at least two of these is preferred, and Sb2O5, SnO2 and SnO2-SiO2 complexes are more preferred.

[0030] When the metal oxide is a SnO2-SiO2 composite, the SiO2 / SnO2 mass ratio is preferably 0.1 to 5.0. An amine compound is preferably bonded to the surface of the metal oxide, and more preferably the amine compound is bonded in a molar ratio of amine compound / (SnO2+SiO2) in the range of 0.001 to 1.0.

[0031] The amine compound may be any of primary amines, secondary amines, and 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 alone or in combination of two or more.

[0032] The amine compound can be bonded to the SnO2-SiO2 composite by a known method, such as that described in Japanese Patent No. 5704345.

[0033] 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 core, but from the viewpoint of reliably covering the core, it is preferably 1 to 10 nm.

[0034] The mass ratio of the metal oxide nanoparticles to the metal oxide (metal oxide / metal oxide nanoparticles) is preferably 0.01 to 1.00, more preferably 0.03 to 0.30, from the viewpoint of achieving both dispersibility in organic solvents and charge transport properties.

[0035] The surface treatment agent is preferably a compound represented by the following formulas (S1) to (S9): These surface treatment agents may be used alone or in combination of two or more.

[0036]

[0037] In formula (S1), R 1sare each independently an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 are bonded to a silicon atom by a Si—C bond; R 2s each independently represents an alkoxy group, an acyloxy group, or a halogen atom; a1 represents an integer of 1 to 3.

[0038] In formula (S2), R 3s are each independently an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms, and R 4s each independently represents an alkoxy group, an acyloxy group, or a halogen atom; Y s represents an alkylene group, an NH group, or an oxygen atom; b1 is an integer of 1 to 3; and c1 is 0 or 1.

[0039] In formula (S3), R 5s are each independently an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms, and R 6s each independently represents an alkoxy group, an acyloxy group, or a halogen atom; and d1 represents an integer of 1 to 3.

[0040] In formula (S4), R 7s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 e1 represents 1 or 2.

[0041] In formula (S5), R 8s 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.

[0042] In formula (S6), R 9srepresents 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.

[0043] In formula (S7), R 10s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 11s represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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.

[0044] In formula (S8), R 12s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 13s represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; Z s represents an oxygen atom or a sulfur atom.

[0045] In formula (S9), R 14s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 f1 represents 1 or 2.

[0046] The alkyl group is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, and even more preferably an alkyl group having 1 to 8 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a cyclopropyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, a cyclobutyl group, a 1-methyl-cyclopropyl group, a 2-methyl-cyclopropyl group, an n-pentyl group, a 1-methyl-n-butyl group, a 2-methyl-n-butyl group, a 3-methyl-n-butyl group, a 1,1-dimethyl-n-propyl group, a 1,2-dimethyl-n-propyl group, a 2,2-dimethyl-n-propyl group, a 1-ethyl-n-propyl group, a cyclobutyl group, a cyclopropyl ... n-hexyl group, 1-methyl-n-pentyl group, 2-methyl-n-pentyl group, 3-methyl-n-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-n-butyl 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 a 2,3-trimethyl-cyclopropyl group, a 1-ethyl-2-methyl-cyclopropyl group, a 2-ethyl-1-methyl-cyclopropyl group, a 2-ethyl-2-methyl-cyclopropyl group, a 2-ethyl-3-methyl-cyclopropyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group.

[0047] Examples of halogenated alkyl groups include the above-mentioned alkyl groups in which at least one carbon atom is substituted with a halogen group, preferably a halogenated alkyl group having 1 to 18 carbon atoms, more preferably a halogenated alkyl group having 1 to 10 carbon atoms, and even more preferably a halogenated alkyl group having 1 to 8 carbon atoms. Specific examples of the halogenated alkyl group include fluoromethyl, difluoromethyl, trifluoromethyl, bromodifluoromethyl, 2-chloroethyl, 2-bromoethyl, 1,1-difluoroethyl, 2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, 2-chloro-1,1,2-trifluoroethyl, pentafluoroethyl, 3-bromopropyl, 2,2,3,3-tetrafluoropropyl, 1,1,2,3,3,3-hexafluoropropyl, 1,1,1,3,3,3-hexafluoropropan-2-yl, 3-bromo-2-methylpropyl, 4-bromobutyl, perfluoropentyl, and 2-(perfluorohexyl)ethyl groups.

[0048] The alkenyl group is preferably an alkenyl group having 2 to 10 carbon atoms, and more preferably an alkenyl group having 2 to 8 carbon atoms. Specific examples of the alkenyl group include ethenyl, 1-propenyl, 2-propenyl, 1-methyl-1-ethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylethenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-n-propylethenyl, 1-methyl-1-butenyl, 1-methyl-2-butenyl, 1-methyl-3-butenyl, 2-ethyl-2-propenyl, 2-methyl-1-butenyl, 2-methyl-2-butenyl, 2-methyl-3-butenyl, 3-methyl-4-butenyl, 4-methyl-5-butenyl, 5-methyl-6-butenyl, 5-methyl-7-butenyl, 5-methyl-8-butenyl, 5-methyl-9-butenyl, 5-methyl-10-butenyl, 10-methyl-11-butenyl, 10-methyl-12-butenyl, 10-methyl-13-butenyl, 10-methyl-14-butenyl, 10-methyl-15-butenyl, 10-methyl-16-butenyl, 10-methyl-17-butenyl, 10-methyl-18-butenyl, 10-methyl-19-butenyl, 10-methyl-20-butenyl, 10-methyl-21-butenyl, 10-methyl-22-butenyl, 10-methyl-23-butenyl, 10-methyl-24-butenyl, 10-methyl-25-butenyl, 10-methyl-26-buten 1-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, 2-methyl-2-pentenyl group, and the like.

[0049] The aryl group is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 10 carbon atoms. Specific examples of the aryl group include a phenyl group, a naphthyl group, an anthracenyl group, and a pyrenyl group.

[0050] The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms, and more preferably an alkoxy group having 1 to 8 carbon atoms. Specific examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, an n-butoxy group, an i-butoxy group, an s-butoxy group, a t-butoxy group, an n-pentyloxy group, a 1-methyl-n-butoxy group, a 2-methyl-n-butoxy group, a 3-methyl-n-butoxy group, a 1,1-dimethyl-n-propoxy group, a 1,2-dimethyl-n-propoxy group, a 2,2-dimethyl-n-propoxy group, a 1-ethyl-n-propoxy group, and an n-hexyloxy group.

[0051] The acyloxy group is preferably an acyloxy group having 2 to 10 carbon atoms, and more preferably an acyloxy group having 2 to 8 carbon atoms. Specific examples of the acyloxy group include, but are not limited to, a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an i-propylcarbonyloxy group, an n-butylcarbonyloxy group, an i-butylcarbonyloxy group, an s-butylcarbonyloxy group, a t-butylcarbonyloxy group, an n-pentylcarbonyloxy group, a 1-methyl-n-butylcarbonyloxy group, a 2-methyl-n-butylcarbonyloxy group, a 3-methyl-n-butylcarbonyloxy group, a 1,1-dimethyl-n-propylcarbonyloxy group, a 1,2-dimethyl-n-propylcarbonyloxy group, a 2,2-dimethyl-n-propylcarbonyloxy group, a 1-ethyl-n-propylcarbonyloxy group, an n-hexylcarbonyloxy group, a 1-methyl-n-pentylcarbonyloxy group, and a 2-methyl-n-pentylcarbonyloxy group.

[0052] Examples of the alkylene group include alkylene groups derived from the above-mentioned alkyl groups, preferably alkylene groups having 1 to 18 carbon atoms, and more preferably alkylene groups having 1 to 8 carbon atoms. Specific examples of the alkylene group include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a 1,2-dimethylethylene group, a tetramethylethylene group, a trimethylene group, a propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, and a 1,4-cyclohexylene group.

[0053] Halogen atoms include fluorine atoms, chlorine atoms, bromine atoms and iodine atoms.

[0054] Examples of organic groups having a polyether group include polyetherpropyl groups having an alkoxy group, such as (CH3O)3SiC3H6(OC2H4). n1 OCH3. n1 can be in the range of 1 to 100, or 1 to 10.

[0055] Examples of the organic group having an epoxy group include a 2-(3,4-epoxycyclohexyl)ethyl group and a 3-glycidoxypropyl group.

[0056] The (meth)acryloyl group refers to both an acryloyl group and a methacryloyl group. Examples of organic groups having a (meth)acryloyl group include a 3-methacryloxypropyl group and a 3-acryloxypropyl group.

[0057] Examples of the organic group having a mercapto group include a 3-mercaptopropyl group.

[0058] Examples of organic groups having an amino group include a 2-aminoethyl group, a 3-aminopropyl group, an N-2-(aminoethyl)-3-aminopropyl group, an N-(1,3-dimethyl-butylidene)aminopropyl group, an N-phenyl-3-aminopropyl group, and an N-(vinylbenzyl)-2-aminoethyl-3-aminopropyl group.

[0059] Examples of the organic group having a ureido group include a 3-ureidopropyl group.

[0060] Examples of the organic group having a thioureido group include 3-thioureidopropyl.

[0061] An example of the organic group having a cyano group is a 3-cyanopropyl group.

[0062] In the compound represented by formula (S1), R 1s Preferably, R are each independently an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, an amino group, a ureido group, or a thioureido group, and are bonded to a silicon atom by a Si—C bond. 2s are each independently preferably an alkoxy group.

[0063] Furthermore, the compound represented by (S1) above includes R 1s are each independently an alkyl group or an alkyl group substituted with a mercapto group, and R 1s at least one of R is an alkyl group substituted with a mercapto group; 2s is an alkoxy group, and a1 is an integer of 1 to 3.

[0064] Specific examples of the compound represented by formula (S1) include, but are not limited to, compounds represented by the following formulas (S1-1) to (S1-10).

[0065]

[0066] In formula (S2), R 3s are each independently preferably an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 10 carbon atoms. 4s are each independently preferably an alkoxy group or a halogen atom. s is preferably an alkylene group, an NH group, or an oxygen atom.

[0067] Furthermore, the compound represented by the above formula (2) is preferably a compound capable of forming a trimethylsilyl group or a triethylsilyl group on the surface of silica particles.

[0068] Specific examples of the compound represented by formula (S2) include, but are not limited to, compounds represented by the following formulas (S2-1) to (S2-4). These silane compounds may be commercially available products, and for example, silane compounds manufactured by Shin-Etsu Chemical Co., Ltd. may be used.

[0069]

[0070] In formula (S3), R 5s are each independently preferably an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 10 carbon atoms. 6s are each independently preferably an alkoxy group or a halogen atom.

[0071] Furthermore, the compound represented by formula (S3) above is preferably a compound capable of forming trimethylsilyl groups or triethylsilyl groups on the surface of silica particles. Examples of such compounds include those represented by the following formulas (S3'-1) to (S3'-2).

[0072]

[0073] In the above formula, R 51s is an alkoxy group, and specific examples thereof include those exemplified above, such as a methoxy group and an ethoxy group. As the silane compound, a commercially available product can be used, and for example, a silane compound manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0074] Specific examples of the compound represented by formula (S3) include, but are not limited to, compounds represented by the following formulas (S3-1) to (S3-4).

[0075]

[0076] In formula (S4), R 7s are preferably each independently an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group.

[0077] Specific examples of the compound represented by formula (S4) include, but are not limited to, the compound represented by formula (S4-1) below.

[0078]

[0079] In formula (S5), R 8s As the alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group is preferred.

[0080] In formula (S6), R 9s As the alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group is preferred.

[0081] Specific examples of the compound represented by formula (S6) include, but are not limited to, the compound represented by formula (S6-1) below.

[0082]

[0083] In formula (S7), R 10s R is preferably an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group. 11s As the alkyl group, a hydrogen atom, an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group is preferred.

[0084] In formula (S8), R 12s R is preferably an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group. 13s As the alkyl group, a hydrogen atom, an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group is preferred.

[0085] Specific examples of the compound represented by formula (S8) include, but are not limited to, the compound represented by formula (S8-1) below.

[0086]

[0087] In formula (S9), R 14s are preferably each independently an alkyl group, an alkenyl group, or an organic group having a polyether group, an epoxy group, a (meth)acryloyl group, a mercapto group, a ureido group, or a thioureido group.

[0088] The surface-treated metal oxide nanoparticles can be produced by coating the surfaces of colloidal metal oxide nanoparticles (cores) having a primary particle size within the above range with one or more selected from the group consisting of the metal oxides and surface treatment agents described above. Specific examples of the surface-treated metal oxide nanoparticles include metal oxide-coated nanoparticles in which the surfaces of colloidal metal oxide nanoparticles (cores) having a primary particle size within the above range are coated with a metal oxide; surface treatment agent-coated nanoparticles obtained by coating the surfaces of colloidal metal oxide nanoparticles (cores) having a primary particle size within the above range with a surface treatment agent; and surface-treated metal oxide nanoparticles obtained by coating the surfaces of colloidal metal oxide nanoparticles (cores) having a primary particle size within the above range with a metal oxide (metal oxide-coated nanoparticles) and then further coating the surfaces of the metal oxide with a surface treatment agent. For methods of producing colloidal metal oxide nanoparticles and methods of coating the surfaces of the metal oxide nanoparticles with a metal oxide, known methods can be used. Examples of known methods include those described in Japanese Patent Nos. 4,561,955, 4,730,487, and 5,704,345. Furthermore, the method for coating the surface of the metal oxide with a surface treatment agent can also be based on known methods, such as the method described in Japanese Patent No. 5704345.

[0089] Furthermore, from the viewpoint of improving the charge transport properties of the resulting thin film, metal oxide-coated nanoparticles whose core surfaces are coated with a metal oxide are preferably hydrothermally treated metal oxide-coated nanoparticles that have been subjected to a hydrothermal treatment in the production process. In the present invention, examples of the hydrothermal treatment method include Methods 1 and 2 below. Method 1: A method in which metal oxide nanoparticles before surface coating are subjected to a hydrothermal treatment to obtain hydrothermally treated metal oxide nanoparticles, and the surfaces of the hydrothermally treated metal oxide nanoparticles are coated with a metal oxide. Method 2: A method in which metal oxide-coated nanoparticles obtained by coating the surfaces of metal oxide nanoparticles (not subjected to hydrothermal treatment) with a metal oxide are further subjected to a hydrothermal treatment to obtain hydrothermally treated metal oxide-coated nanoparticles.

[0090] When the hydrothermal treatment is carried out, the temperature is preferably 60 to 180° C. The treatment time is preferably 0.1 to 50 hours.

[0091] The surface treatment of the metal oxide-coated nanoparticles with a surface treatment agent can be carried out by adding the surface treatment agent to a dispersion of the metal oxide-coated nanoparticles and heating the mixture at a predetermined temperature. If the dispersion medium of the metal oxide-coated nanoparticles is not suitable for use with the surface treatment agent, it can be replaced with an appropriate solvent.

[0092] The surface treatment can be carried out at a temperature ranging from 20° C. to the boiling point of the dispersion medium, preferably 20 to 100° C. The treatment time is preferably about 0.1 to 48 hours.

[0093] The amount of the surface treatment agent used is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, based on the mass of the metal oxide-coated nanoparticles, from the viewpoint of reliably coating the surfaces of the metal oxide-coated nanoparticles.

[0094] When the compounds (silane compounds) represented by formulae (S1) to (S3) are used as the surface treatment agents, water is required for the hydrolysis of these silane compounds. However, when an aqueous medium is substituted with an organic solvent, the water remaining in the solvent can be used. For example, water present in an amount of 0.01 to 10% by mass can be used. Furthermore, the hydrolysis can be carried out with or without a catalyst.

[0095] The surface-treated metal oxide nanoparticles contained in the charge transport ink composition of the present invention may be of one type alone or two or more types.

[0096] The surface-treated metal oxide nanoparticles contained in the charge transport ink composition of the present invention are preferably uniformly dispersed in the composition.

[0097] The surface-treated metal oxide nanoparticles may contain one or more organic capping groups. The organic capping groups may be reactive or non-reactive. Examples of reactive organic capping groups include organic capping groups that can be crosslinked by ultraviolet light or a radical initiator.

[0098] The primary particle diameter of the surface-treated metal oxide nanoparticles is not particularly limited as long as it is nano-sized, but in consideration of obtaining a thin film with good reproducibility and excellent flatness, it is preferably 2 to 60 nm, more preferably 3 to 40 nm.

[0099] When the charge transport ink composition of the present invention contains metal oxide nanoparticles, the content thereof is not particularly limited, but from the viewpoint of suppressing particle aggregation in the charge transport ink composition and obtaining a thin film with excellent flatness and good reproducibility, the content is preferably 0.01 to 30 mass %, more preferably 0.05 to 20 mass %, even more preferably 0.07 to 15 mass %, and most preferably 0.1 to 10 mass %, of the solid content.

[0100] 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 good reproducibility. Such a metal oxide nanoparticle sol can be prepared by a known method using a solvent and metal oxide nanoparticles that can be contained in the charge transport ink composition of the present invention.

[0101] In particular, when preparing the charge transport ink composition of the present invention, it is preferable to use a metal oxide nanoparticle sol in which metal oxide nanoparticles are dispersed in a dispersion medium. The metal oxide nanoparticle sol is not particularly limited, as long as the metal oxide nanoparticles are stably dispersed in a solvent. In the present invention, a metal oxide nanoparticle sol with improved dispersibility in the charge transport ink composition may preferably be a surface-treated metal oxide nanoparticle sol containing surface-treated metal oxide nanoparticles having a core composed of one or more metal oxide nanoparticles selected from the group consisting of ZnO, a ZnO-MgO composite, SnO, and a SnO-TiO-ZrO composite, the surface of the core being coated with SnO, SbO, or a SnO-SiO composite (metal oxide), and the surface of the SnO, SbO, or SnO-SiO composite being further coated with at least one surface treatment agent selected from the group consisting of compounds represented by the following formulas (S1) to (S9), and a solvent.

[0102] (In formula (S1), R 1s are each independently an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 are bonded to a silicon atom by a Si—C bond; R 2s each independently represents an alkoxy group, an acyloxy group, or a halogen atom, and a1 represents an integer of 1 to 3. In formula (S2), R 3s are each independently an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms, and R 4s each independently represents an alkoxy group, an acyloxy group, or a halogen atom; Y s represents an alkylene group, an NH group, or an oxygen atom, b1 is an integer of 1 to 3, and c1 is 0 or 1. In formula (S3), R 5s are each independently an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms, and R 6seach independently represents an alkoxy group, an acyloxy group, or a halogen atom, and d1 represents an integer of 1 to 3. In formula (S4), R 7s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 e1 represents 1 or 2. 8s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 9s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 10s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 11 represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 12s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 13 represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; Z srepresents an oxygen atom or a sulfur atom. 14s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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.

[0103] In formulas (S1) to (S9), R 1s ~R 14s , Y s and Z s The above is the same as that exemplified in the description of the metal oxide nanoparticles.

[0104] Metal oxide nanoparticle sols are usually in the form of a dispersion. Examples of metal oxide nanoparticle sols include those in which metal oxide nanoparticles are 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, and terpineol. 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, 1,2-hexanediol, and 3-methyl-1,5-pentanediol. 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 the ester 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 butyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl 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.

[0105] In particular, in the present invention, surface-treated metal oxide nanoparticles in which the dispersion medium is methanol, ethanol, n-propanol, i-propanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene 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, tripropylene glycol monomethyl ether, tripropylene glycol butyl ether, N,N-dimethylformamide, n-hexane, or toluene are preferred.

[0106] The solids concentration of the metal oxide nanoparticle sol of the present invention is appropriately set taking into consideration the saturated solubility in the solvent, storage stability, etc., but is usually about 0.01 to 30 mass %, preferably about 0.05 to 20 mass %, and more preferably about 0.1 to 10 mass %.

[0107] The concentration of metal oxide nanoparticles in the charge transport ink composition is set appropriately taking into consideration the viscosity and surface tension of the charge transport ink composition, the thickness of the thin film to be produced, etc., but is usually about 0.1 to 30 mass %. If the concentration of metal oxide nanoparticles is high, the metal oxide nanoparticles may aggregate depending on the type of solvent contained in the mixture, so this point must be taken into consideration when preparing the composition.

[0108] [2-2] Copper(I) halide or pseudocopper(I) halide Copper(I) halide is a compound consisting of copper(I) ion and its counter anion, a halide ion. The halide ion can be a fluoride ion (F - ), chloride ions (Cl - ), bromide ion (Br - ), iodide ion (I - Specific examples of copper(I) halides include copper(I) fluoride (CuF), copper(I) chloride (CuCl), copper(I) bromide (CuBr), and copper(I) iodide (CuI). These copper(I) halides may be used alone or in combination of two or more.

[0109] Pseudocopper(I) halides are compounds consisting of copper(I) ions and their counter anions, pseudohalide ions. The pseudohalide ions are a general term for anions that exhibit properties similar to halogen atoms, and specific examples include thiocyanate ions (SCN - ), cyano ion (CN - ), cyanate ion (NCO - ), isocyanate ion (OCN - ) Selenocyanic acid (SeCN - ), azide ion (N -) and the like. Specific examples of pseudo copper(I) halides include copper(I) thiocyanate (CuSCN), copper(I) cyanide (CuCN), copper(I) isocyanate (CuOCN), copper(I) selenocyanate (CuSeCN), copper(I) azide (CuN3), and the like. These pseudo copper(I) halides may be used alone or in combination of two or more.

[0110] In the present invention, among the above copper(I) halides and pseudocopper(I) halides, copper(I) halide or copper(I) thiocyanate is preferred, and copper(I) iodide is more preferred, from the viewpoint of the charge transport property and solvent resistance of the resulting thin film.

[0111] When the charge transport ink composition of the present invention contains the copper(I) halide or pseudocopper(I) halide as the charge transport substance, the content thereof is preferably 10 to 70 mass %, more preferably 30 to 70 mass %, and even more preferably 40 to 60 mass %, of the solid content, from the viewpoints of the charge transport property and solvent resistance of the resulting thin film.

[0112] Copper(I) halide and pseudocopper(I) halide may be used in combination, and in this case, it is preferable to use copper(I) iodide and copper(I) thiocyanate in combination. In this case, the content of pseudocopper(I) halide is preferably 0.1 to 2.0 mol, more preferably 0.2 to 1.0 mol, and even more preferably 0.3 to 0.7 mol per mol of copper(I) halide.

[0113] When the charge-transporting ink composition of the present invention contains the copper(I) halide or pseudocopper(I) halide as the charge-transporting substance, it may further contain an amine. When the composition contains an amine, it preferably contains one selected from the group consisting of amines represented by the following formulas (1) to (3):

[0114]

[0115] In formula (1), R 1 ~R 4are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In formula (2), L is an alkylene group having 3 to 8 carbon atoms, and the alkylene group may have an oxygen atom between the carbon atoms. However, there are at least three carbon atoms between HN- and -OH. In formula (3), R 5 ~R 6 each independently represents an alkyl group having 1 to 6 carbon atoms which may be substituted with a hydroxy group, and the alkyl group may have an oxygen atom between the carbon atoms. 5 and R 6 At least one of the alkyl groups is substituted with a hydroxy group or has an oxygen atom between the carbon atoms.

[0116] Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, an n-pentyl group, and an n-hexyl group.

[0117] Examples of the alkylene group having 3 to 8 carbon atoms (which satisfies the amine structure represented by the formula (2)) include a trimethylene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group.

[0118] In the above formula (1), R 1 ~R 4 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably contains at least one hydrogen atom and at least one alkyl group.

[0119] Specific examples of the amine represented by formula (1) include, but are not limited to, those represented by the following formulae (1-1) to (1-5). Among these, those represented by the following formulae (1-1) and (1-2) are preferred.

[0120]

[0121] In the above formula (2), L is preferably an alkylene group having 4 to 6 carbon atoms, more preferably a tetramethylene group, a pentamethylene group, or a hexamethylene group.

[0122] Specific examples of the amine represented by the formula (2) include, but are not limited to, those represented by the following formulas (2-1) and (2-2). Among these, the amine represented by the following formula (2-1) is preferred.

[0123]

[0124] In the above formula (3), R 5 ~R 6 The alkyl group in R is preferably an alkyl group having 3 to 5 carbon atoms. 5 and R 6 Preferably, both alkyl groups in the above are substituted with a hydroxy group or an oxygen atom is present between the carbon atoms, and more preferably, an oxygen atom is present between the carbon atoms.

[0125] Specific examples of the amine represented by the above formula (3) include, but are not limited to, those represented by the following formula (3-1):

[0126]

[0127] The content of the amine is usually, taking into consideration the solubility of the copper(I) halide or pseudocopper(I) halide, and is preferably 1 to 40 moles, more preferably 1 to 10 moles, even more preferably 2 to 8 moles, and still more preferably 3 to 7 moles per mole of the copper(I) halide or pseudocopper(I) halide. Note that the amine is not included in the solid content.

[0128] In the present invention, the charge transporting substance may be the metal oxide nanoparticles described above, or copper(I) halide and pseudocopper(I) halide, and a charge transporting substance composed of a charge transporting compound other than these may be used in combination, but it is preferable that only the metal oxide nanoparticles described above, or copper(I) halide and pseudocopper(I) halide are included.

[0129] [3] Other Organic Solvents The charge transporting ink composition of the present invention may contain organic solvents other than the specific solvents described above. Such organic solvents are not particularly limited as long as they disperse or dissolve solid components. Specific examples thereof include alcohol solvents such as n-propanol, n-butanol, 1-octanol, 1-nonanol, tetrahydrofurfuryl alcohol, terpineol, cyclohexanol, diacetone alcohol, benzyl alcohol, 2-phenoxyethanol, and 2-benzyloxyethanol; glycol solvents such as propylene glycol, 2-methyl-2,4-pentanediol, 1,3-octylene glycol, dipropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, and 3-methyl-1,5-pentanediol; and 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, 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, adipic acid Dipropyl, diisopropyl malonate, dimethyl sebacate, diethyl sebacate, methyl benzoate, ethyl benzoate, butyl benzoate, diethyl 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, dipropylene glycol methyl ether acetate, 1,3-butylene glycol diacetate, 1,6-hexyl Ester-based solvents such as Sandiol diacetate, triacetin, and γ-butyrolactone; ether-based solvents such as dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, anisole, and 4-methoxytoluene; 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;The solvent may be appropriately selected from among amide solvents such as N-methylformamide, N-methylacetamide, N-methylformanilide, N,N-dimethylacetamide, N,N-dimethylformamide, N,N-dimethylisobutyramide, 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; and sulfoxide solvents such as dimethyl sulfoxide. In the present invention, among these, alcohol-based solvents, glycol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents are preferred, and 1-octanol, 1-nonanol, terpineol, 2-methyl-2,4-pentanediol, dipropylene glycol, 3-methyl-1,5-pentanediol, isophorone, 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 are more preferred. These organic solvents can be used either alone or in combination of two or more.

[0130] When the solvent of the charge transport ink composition of the present invention contains the above-mentioned other organic solvents, the content of the other organic solvents in the solvent is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 0% by mass or less.

[0131] The charge transport ink composition of the present invention optimally uses only an organic solvent (specific solvent and other organic solvents, preferably specific solvent) as the solvent. Note that "only organic solvent" in this case means that only the organic solvent is used as the solvent, and does not exclude the presence of trace amounts of "water" contained in the organic solvent or solid content used.

[0132] [4] Binder Resin The charge-transporting ink composition of the present invention may contain a binder resin, as described below, if necessary, in order to further improve the flatness and charge-transporting properties of the resulting thin film.

[0133] The binder resin is not particularly limited as long as it disperses or dissolves in at least one solvent used in the charge transport ink composition, and a polymeric material can be used as the binder. Blending metal oxide nanoparticles into the binder resin provides excellent film-forming properties and makes it possible to easily form a stable film. Note that at least one type of binder resin is sufficient, and the number of types is not particularly limited.

[0134] Specific examples of the material that can be used include, but are not limited to, polystyrene, polyimide, polycarbonate, acrylic resin, and inactive resin.

[0135] Furthermore, the binder resin may have charge transport properties, or a charge transport material 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. Metal oxide nanoparticles themselves have sufficient charge transport properties, but when minute nanoparticles are uniformly dispersed in the binder at a low concentration, the charges carried by the nanoparticles may not be transported effectively. Therefore, by using a material with charge transport properties as a material constituting the electron transport layer other than the metal oxide nanoparticles, the high charge transport properties of the metal oxide nanoparticles can be more effectively utilized.

[0136] When the charge-transporting ink composition of the present invention contains a binder resin, the content thereof is usually about 5 to 95% by mass of the solid content. However, taking into consideration the balance between improving the flatness of the thin film obtained and suppressing a decrease in charge transport properties, the content is preferably about 10 to 90% by mass, more preferably about 20 to 80% by mass, and even more preferably about 30 to 70% by mass.

[0137] [5] Organic Silane Compound or Phosphate Ester Compound The charge transport ink composition of the present invention may contain an organic silane compound or a phosphate ester compound. When a charge transport thin film obtained from the ink composition is used as an electron transport layer of a quantum dot EL device, the inclusion of such an organic silane compound or a phosphate ester compound in the charge transport ink composition can improve the flatness of the obtained thin film and the electron transport properties to the light-emitting layer provided in contact with the thin film.

[0138] As the organic silane compound, alkoxysilanes are preferred, with trialkoxysilanes and tetraalkoxysilanes being more preferred. Examples of the alkoxysilane include tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, dimethyldiethoxysilane, and dimethyldimethoxysilane. Among these, tetraethoxysilane (TEOS), tetramethoxysilane, and tetraisopropoxysilane are preferred for use in the present invention. These organic silane compounds can be used alone or in combination of two or more. Furthermore, these organic silane compounds can be used in combination with the phosphate ester-based compounds described below.

[0139] The phosphate ester compound is preferably a compound represented by the following formulas (B1) to (B3), and more preferably a polyoxyethylene alkyl ether phosphate ester represented by the following formula (B1). Examples of the polyoxyethylene alkyl ether phosphate ester include those represented by the following formula (B1) where the terminal alkyl group Y 1bwhere R represents an alkyl group having 6 to 15 carbon atoms. Commercially available phosphate ester compounds include, for example, products manufactured by Toho Chemical Industry Co., Ltd. under the trade names Phosphanol RA-600, RS-410, RS-610, and RS-710. These phosphate ester compounds can be used alone or in combination of two or more. These phosphate ester compounds can also be used in combination with an organosilane compound.

[0140]

[0141] In formulas (B1) to (B3), X 1b , X 2b and X 3b each independently represents an alkylene group having 2 to 20 carbon atoms; f2, h2, and j2 each independently represent an integer of 1 to 100; e2, g2, and i2 each independently represent an integer of 1 to 3; Y 1b , Y 2b and Y 3b are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a (meth)acrylic group.

[0142] The alkylene group having 2 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include a methylmethylene group, a dimethylmethylene group, an ethylene group, a 1,2-dimethylethylene group, a tetramethylethylene group, a trimethylene group, a propylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, and a 1,4-cyclohexylene group.

[0143] The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic, and specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a s-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadec ...octyl group, an n-pentyl group, an n-hexadecyl group, an n-heptadecyl group, an n-pentyl group, an n-hexadecyl group, an n-heptadecyl group, an n-pentyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadecyl group, an n-hexadec straight-chain or branched-chain 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.

[0144] Examples of alkenyl groups having 2 to 20 carbon atoms include ethenyl, n-1-propenyl, n-2-propenyl, 1-methylethenyl, n-1-butenyl, n-2-butenyl, n-3-butenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, 1-ethylethenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, n-1-pentenyl, n-1-decenyl, and n-1-eicosenyl groups.

[0145] Examples of the aryl group having 6 to 30 carbon atoms include a phenyl group, a tolyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a 1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a 4-phenanthryl group, a 9-phenanthryl group, a biphenyl-2-yl group, a biphenyl-3-yl group, and a biphenyl-4-yl group.

[0146] When the charge transport ink composition of the present invention contains an organic silane compound or a phosphate ester-based compound, the content thereof is usually about 0.1 to 50 mass % of the solid content. However, taking into consideration the balance between improving the flatness of the thin film obtained and suppressing a decrease in charge transport properties, the content is preferably about 0.5 to 40 mass %, more preferably about 0.8 to 30 mass %, and even more preferably about 1 to 20 mass %.

[0147] [6] Charge-transporting ink composition and charge-transporting thin film 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 types of organic solvents used, their ratios, solids concentration, etc., taking into consideration various factors such as the dispersibility of the surface-treated metal oxide nanoparticles, the coating method used, and the desired film thickness.

[0148] The solids concentration of the charge transport ink composition of the present invention is set appropriately taking into consideration the viscosity and surface tension of the charge transport ink composition, the thickness of the thin film to be produced, and the like. However, it is usually about 0.1 to 30% by mass, and from the viewpoint of suppressing aggregation of the charge transport substance and metal oxide nanoparticles in the ink composition, it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0149] When preparing the charge transport ink composition of the present invention, the charge transport material and the specific solvent, and optionally other components such as organic solvents other than the specific solvent, binder resins, and organosilane compounds or phosphate ester compounds, can be mixed in any order as long as the solids are uniformly dissolved or dispersed in the solvent. When the other components are included, for example, a method can be used in which previously prepared other components or their solutions are added to a metal oxide nanoparticle sol dispersed in a specific solvent. The above method can be used as long as the solids are uniformly dissolved or dispersed in the solvent. When using a binder resin, organosilane compound, or phosphate ester compound, these can be dissolved at any time during the above method. Note that metal oxide nanoparticles may aggregate or precipitate when mixed, depending on the type and amount of the components mixed with them. When preparing the charge transport ink composition, heating may be performed as appropriate within a range that does not cause decomposition or deterioration of the components.

[0150] In the present invention, the charge transporting ink composition may be filtered using a sub-micrometer filter or the like during the production of the charge transporting ink composition or after all of the components have been mixed, in order to obtain a thin film with higher flatness with good reproducibility.

[0151] The charge-transporting ink composition described above can be applied to a QD layer or one or two functional layers formed thereon, followed by baking to form a layer (charge-transporting thin film) above the QD layer. Note that the layer structure before application of the charge-transporting ink composition of the present application is sometimes referred to as the substrate.

[0152] The method for applying the ink composition is not particularly limited, and examples thereof include a dipping method, a spin coating method, a transfer printing method, a roll coating method, a brush coating method, an inkjet method, a spray method, and a slit coating method. It is preferable to adjust the viscosity and surface tension of the ink composition depending on the application method.

[0153] Furthermore, when using the charge transport ink composition of the present invention, the baking atmosphere is not particularly limited; a thin film with a uniform film surface and high charge transport properties can be obtained not only in air but also in an inert gas atmosphere such as nitrogen or in a vacuum. The baking temperature is appropriately set within a range of approximately 80 to 260°C, taking into consideration the application of the resulting thin film, the level of charge transport properties to be imparted to the resulting thin film, the type and boiling point of the solvent, etc. However, when the resulting thin film is used as an electron transport layer in a quantum dot EL device, a temperature of approximately 100 to 250°C is preferred. During baking, two or more temperature changes may be applied to achieve more uniform film formation or to promote reactions on the substrate. Heating may be performed using appropriate equipment, such as a hot plate, oven, or vacuum oven.

[0154] The thickness of the charge-transporting thin film is not particularly limited, but is preferably 5 to 300 nm, and more preferably 20 to 200 nm. Methods for changing the thickness include changing the solids concentration in the charge-transporting ink composition and changing the amount of solution on the substrate during application.

[0155] [7] Quantum Dot EL Device The quantum dot EL device of the present invention has a pair of electrodes and a charge transport layer between these electrodes, which is made of the charge transport thin film of the present invention. Typical configurations of quantum dot EL devices include, but are not limited to, the following (a) to (f). The charge transport ink composition of the present invention can be suitably used in devices having the configurations (a) to (d) among these. In the following configurations, an electron blocking layer or the like can be provided between the light-emitting layer and the anode, and a hole blocking layer or the like can be provided between the light-emitting layer and the cathode, as necessary. Furthermore, the hole injection layer, hole transport layer, or hole injection transport layer may also function as an electron blocking layer, and the electron injection layer or electron transport layer may also function as a hole blocking layer. Furthermore, an optional functional layer can be provided between each layer as necessary. (a) anode / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / electron injection layer / cathode (b) anode / hole injection layer / hole transport layer / light-emitting layer / electron transport layer / cathode (c) anode / hole injection transport layer / light-emitting layer / electron transport layer / electron injection layer / cathode (d) anode / hole injection transport layer / light-emitting layer / electron transport layer / cathode (e) anode / hole injection layer / hole transport layer / light-emitting layer / cathode (f) anode / hole injection transport layer / light-emitting layer / cathode

[0156] The terms "hole injection layer," "hole transport layer," and "hole injection transport layer" refer to layers formed between the light-emitting layer and the anode, which have the function of transporting holes from the anode to the light-emitting layer. When only one layer of a hole-transporting material is provided between the light-emitting layer and the anode, it is the "hole injection transport layer." When two or more layers of a hole-transporting material are provided between the light-emitting layer and the anode, the layer closest to the anode is the "hole injection layer," and the remaining layers are "hole transport layers." In particular, the hole injection (transport) layer is a thin film that is excellent not only in the ability to accept holes from the anode but also in the ability to inject holes into the hole transport (light-emitting) layer.

[0157] An "electron injection layer" and an "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. When only one layer of an electron-transporting material is provided between the light-emitting layer and the cathode, it is the "electron transport layer." When two or more layers of an electron-transporting material are provided between the light-emitting layer and the cathode, the layer closest to the cathode is the "electron injection layer," and the other layers are "electron transport layers." An "light-emitting layer" is a layer that has a light-emitting function and is a quantum dot light-emitting layer.

[0158] The charge transport thin film produced from the charge transport ink composition of the present invention can be used as a functional layer formed between a cathode and a light-emitting layer in a quantum dot EL device, but is also suitable as an electron injection layer or an electron transport layer, and is more suitable as an electron transport layer. In particular, when the charge transport ink composition contains one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi, and Sr, and composites of at least two of these metals, the resulting charge transport thin film is more suitable as an electron transport layer.

[0159] The charge transport thin film prepared from the charge transport ink composition of the present invention can be used as a functional layer formed between an anode and an emitting layer in a quantum dot EL device, but is suitable as a hole injection layer, a hole transport layer, or a hole injection transport layer, and is more suitable as a hole transport layer. In particular, when the charge transport ink composition contains copper(I) halide or pseudocopper(I) halide, the resulting charge transport thin film is more suitable as a hole transport layer.

[0160] When an EL device is produced using the charge transporting ink composition of the present invention, the materials and production methods used include, but are not limited to, those listed below.

[0161] An example of a method for producing a quantum dot EL device having an electron transport layer composed of a thin film obtained from the charge transport ink composition of the present invention is as follows. It is preferable to previously perform surface treatment on the electrodes, such as cleaning with alcohol, pure water, or the like, or UV ozone treatment, oxygen plasma treatment, or the like, to the extent that the electrode is not adversely affected. A hole injection layer and a hole transport layer are sequentially laminated on an anode substrate by a wet process using a hole injection layer-forming composition or a hole transport layer-forming composition containing a hole transport polymer. A hole injection layer or a hole transport layer may also be formed by a wet process using the charge transport composition of the present invention. Subsequently, an emissive layer is laminated by a wet process using an emissive layer-forming composition containing a quantum dot material. Furthermore, an electron transport layer is formed by a wet process using the charge transport ink composition of the present invention, and a cathode metal is vapor-deposited thereon. Alternatively, in this method, instead of forming the hole injection layer, hole transport layer, and emissive layer by a wet process, these layers can also be formed by vapor deposition. If necessary, an electron blocking layer may be provided between the emissive layer and the hole transport layer. In the above, an example (forward structure) in which an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode are stacked in this order has been described, but the present invention is not limited thereto, and a reverse structure in which a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and an anode are stacked in this order may also be used.

[0162] Examples of anode materials include transparent electrodes such as indium tin oxide (ITO) and indium zinc oxide (IZO), metal anodes such as aluminum, and metal 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 can be used to compose the metal anode include, but are not limited to, gold, silver, copper, indium, and alloys thereof.

[0163] 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)], poly[(9,9-bis{1'-penten-5'-yl}fluorenyl-2,7-diyl)-co-(N,N'-bis{p-butylphenyl}-1,4-diaminophenylene)], and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine]-endcapped with Examples include, but are not limited to, polysilcisquinoxane, poly[(9,9-didioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(p-butylphenyl))diphenylamine)], and the like.

[0164] The quantum dot material 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 semiconductor material include 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, and 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 of suitable gallium arsenide include, but are not limited to, Cu ...

[0165] When the charge transport composition of the present invention is used to form an electron injection layer or an electron transport layer, the material for forming the hole injection layer may be, in addition to the charge transport composition of the present invention, copper phthalocyanine, titanium oxide phthalocyanine, platinum phthalocyanine, pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile, 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), WO 2004 / 043117, WO 2004 / 105446, WO 2005 / 000832, WO 2005 / 043962, WO 2005 / 042621, WO 2005 / 107335, WO 2006 / 006459, WO 2006 / 025342, WO 2006 / 137473, WO 2007 / 049631, WO 2007 / 099808, WO 2008 / 010474, WO 20 Charge transport materials described in International Publication Nos. 08 / 032617, WO 2008 / 032616, WO 2008 / 129947, WO 2009 / 096352, WO 2010 / 041701, WO 2010 / 058777, WO 2010 / 058776, WO 2013 / 042623, WO 2013 / 129249, WO 2014 / 115865, WO 2014 / 132917, WO 2014 / 141998 and WO 2014 / 132834 may also be used.

[0166] When an electron injection layer or an electron transport layer is formed using the charge transport composition of the present invention, materials for forming a hole transport layer may include, in addition to the charge transport composition of the present invention, triarylamines such as (triphenylamine) dimer derivatives, [(triphenylamine) dimer] spiro dimer, N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (α-NPD), 4,4',4"-tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA), and 4,4',4"-tris[1-naphthyl(phenyl)amino]triphenylamine (1-TNATA), and oligothiophenes such as 5,5"-bis-{4-[bis(4-methylphenyl)amino]phenyl}-2,2':5',2"-terthiophene (BMA-3T).

[0167] When a hole injection layer or a hole transport layer is formed using the charge transport composition of the present invention, in addition to the charge transport composition of the present invention, an oxydiazole derivative, a triazole derivative, a phenanthroline derivative, a phenylquinoxaline derivative, a benzimidazole derivative, a pyrimidine derivative, or the like may be used as a material for forming the electron transport layer.

[0168] When a hole injection layer or a hole transport layer is formed using the charge transport composition of the present invention, a material for forming the electron injection layer may be, in addition to the charge transport composition of the present invention, a metal oxide such as lithium oxide (LiO), magnesium oxide (MgO), or alumina (AlO), or a metal fluoride such as lithium fluoride (LiF) or sodium fluoride (NaF).

[0169] Cathode materials include, but are not limited to, aluminum, magnesium-silver alloy, aluminum-lithium alloy, etc. Materials for forming the electron blocking layer include, but are not limited to, tris(phenylpyrazole)iridium, etc.

[0170] The materials constituting the anode, cathode, and layers formed therebetween differ depending on whether an element having a bottom emission structure or a top emission structure is manufactured, and therefore, materials are selected appropriately taking this into consideration. Normally, in an element having a bottom emission structure, a transparent anode is used on the substrate side, and light is extracted from the substrate side, whereas in an element having a top emission structure, a reflective anode made of metal is used, and light is extracted from the transparent electrode (cathode) side opposite the substrate. Therefore, for example, in terms of anode materials, when an element having a bottom emission structure is manufactured, a transparent anode such as ITO is used, and when an element having a top emission structure is manufactured, a reflective anode such as an Ag alloy or an Al alloy is used.

[0171] The quantum dot EL device of the present invention may be sealed with a moisture scavenger or the like according to a standard method, if necessary, to prevent deterioration of the characteristics.

[0172] As described above, the charge transport ink composition of the present invention is suitable for use in forming a functional layer (an upper layer of the QD layer) formed between the cathode and the light-emitting layer (QD layer) of a quantum dot EL element, and is particularly suitable for use in forming a hole transport layer or an electron transport layer of a quantum dot EL element.

[0173] The present invention will be explained in more detail below with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited thereto.

[0174] [1] Apparatus The apparatus used in the examples is as follows. (1) Evaluation of primary particle size by transmission electron microscope Apparatus: JEM-1010 transmission electron microscope, manufactured by JEOL Ltd. (2) Evaluation of average particle size by dynamic light scattering Apparatus: Zetasizer NanoS, manufactured by Malvern Instruments Ltd. (3) Spin coating Apparatus: MS-A100 spin coater, manufactured by Mikasa Co., Ltd. (4) Evaluation of fluorescence intensity Apparatus: F-7000 spectrofluorometer, manufactured by Hitachi High-Tech Corporation (5) Inkjet system Inkjet head: PulseInjector, manufactured by Cluster Technology Co., Ltd. Driver: WaveBuilder, manufactured by Cluster Technology Co., Ltd. Automatic stage: Inkjet Designer, manufactured by Cluster Technology Co., Ltd. (6) Evaluation of flatness of charge transport thin film Apparatus: Surfcorder ET-4000 microprofile measuring instrument, manufactured by Kosaka Laboratory Co., Ltd. (7) Gel Permeation Chromatography (GPC) Apparatus: Shimadzu Corporation Column: Shodex (registered trademark) GPC K-803L, GPC K-804L, Showa Denko K.K. Column temperature: 40°C Eluent: tetrahydrofuran The number average molecular weight (hereinafter referred to as Mn) and the weight average molecular weight (hereinafter referred to as Mw) are expressed as polystyrene equivalent values.

[0175] [Reagents] The abbreviations used below have the following meanings. MMA: Methyl methacrylate HEMA: 2-hydroxyethyl methacrylate CHMI: N-cyclohexylmaleimide HPMA: 4-hydroxyphenyl methacrylate MAA: Methacrylic acid AIBN: α,α'-azobisisobutyronitrile PGME: Propylene glycol monomethyl ether HPMA-QD: A compound synthesized by the condensation reaction of 1 mol of 4-hydroxyphenyl methacrylate and 1.1 mol of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride PFHMA: 2-(perfluorohexyl)ethyl methacrylate CHN: Cyclohexanone QD1: A compound synthesized by the condensation reaction of 1 mol of α,α,α'-tris(4-hydroxyphenyl)-1-ethyl-4-isopropylbenzene and 1.5 mol of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride GT-401: butanetetracarboxylic acid tetra(3,4-epoxycyclohexylmethyl) modified ε-caprolactone (trade name: Epolead GT-401 (manufactured by Daicel Corporation)) PGMEA: propylene glycol monomethyl ether acetate TMAH: tetramethylammonium hydroxide

[0176] [2] Preparation of Solvent-Immersed PL Intensity Measurement Substrate [Reference Example 1] In a glove box environment, a quantum dot dispersion (QNA Corporation, trade name PureBlue.dots in Toluene_v2, toluene dispersion, concentration 3% by mass) was applied to a glass substrate using a spin coater. The substrate was then baked at 100°C for 10 minutes in a nitrogen atmosphere to form a quantum dot thin film layer with a film thickness of 40 nm on the substrate. The substrate was then baked at 140°C for 15 minutes in a nitrogen atmosphere and dried to form a quantum dot thin film layer immersed in the ink for the quantum dot layer upper layer film. Thereafter, in order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the ITO substrate and a desiccant (manufactured by Dynic Co., Ltd., product name HD-071010W-40) were placed between sealing substrates (manufactured by Premium Glass Co., Ltd., cell size 19 mm × 21 mm × 0.7 mm, excavation 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, and the sealing substrates were bonded together using an adhesive (manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)), and the sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm). 2 This was used as the substrate for measuring the PL intensity.

[0177] Reference Example 2-1 In a glove box environment, a quantum dot dispersion (QNA Corporation, trade name PureBlue.dots in Toluene_v2, toluene dispersion, concentration 3% by mass) was applied to a glass substrate using a spin coater. The substrate was then baked at 100°C for 10 minutes under a nitrogen atmosphere to form a quantum dot thin film layer with a film thickness of 40 nm on the substrate. The glass substrate on which the resulting quantum dot thin film layer was formed was immersed in dimethyl phthalate (Godo Co., Ltd.) for 15 minutes. The solvent was then removed using a spin coater, and the substrate was baked and dried at 140°C for 15 minutes under a nitrogen atmosphere to form a quantum dot thin film layer immersed in the solvent. Thereafter, in order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the ITO substrate and a desiccant (manufactured by Dynic Co., Ltd., product name HD-071010W-40) were placed between sealing substrates (manufactured by Premium Glass Co., Ltd., cell size 19 mm × 21 mm × 0.7 mm, excavation 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, and the sealing substrates were bonded together using an adhesive (manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)), and the sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm). 2 This was used as a substrate for solvent immersion PL intensity measurement.

[0178] [Reference Examples 2-2 to 2-18] Instead of dimethyl phthalate, methanol (Kanto Chemical Co., Ltd.), ethanol (Kanto Chemical Co., Ltd.), isopropyl alcohol (Kanto Chemical Co., Ltd.), ethylene glycol (Kanto Chemical Co., Ltd.), propylene carbonate (Tokyo Chemical Industry Co., Ltd.), diethylene glycol monobutyl ether acetate (Tokyo Chemical Industry Co., Ltd.), triethylene glycol butyl methyl ether (Toho Chemical Industry Co., Ltd.), tripropylene glycol (Tokyo Chemical Industry Co., Ltd.), 1,2-hexanediol (Tokyo Chemical Industry Co., Ltd.), diethyl phthalate (Tokyo Chemical Industry ... isopropyl alcohol (Tokyo Chemical Industry Co., Ltd.), propylene carbonate (Tokyo Chemical Industry Co., Ltd.), propylene carbonate (Tokyo Chemical Industry Co., Ltd.), isopropyl alcohol (Tokyo Chemical Industry Co., Ltd.), propylene carbonate (Tokyo Chemical Industry Co., Ltd.), propylene carbonate (Tokyo Chemical Industry Co., Ltd.), isopropyl alcohol (Tokyo Chemical Industry Co., Ltd.), propylene carbonate (Tokyo Chemical Industry Substrates for solvent immersion PL intensity measurement were prepared in the same manner as in Reference Example 2-1, except that 2-phenoxyethyl butyrate (Tokyo Chemical Industry Co., Ltd.), diethylene glycol (Kanto Chemical Co., Inc.), dipropylene glycol butyl ether (Fujifilm Wako Pure Chemical Industries, Ltd.), triethylene glycol (Tokyo Chemical Industry Co., Ltd.), diethylene glycol monobenzyl ether (Tokyo Chemical Industry Co., Ltd.), 2-[2-(2-ethylhexyloxy)ethoxy]ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.), and 1-decanol (Tokyo Chemical Industry Co., Ltd.) were used.

[0179] Comparative Reference Examples 1-1 to 1-8 Substrates for solvent immersion PL intensity measurement were prepared in the same manner as in Reference Example 2-1, except that diisopropyl fumarate (Tokyo Chemical Industry Co., Ltd.), 2-ethyl-1,3-hexanediol (Tokyo Chemical Industry Co., Ltd.), tripropylene glycol monobutyl ether (Aldrich), dibutyl malonate (Tokyo Chemical Industry Co., Ltd.), tripropylene glycol monomethyl ether (Tokyo Chemical Industry Co., Ltd.), dibutyl oxalate (Tokyo Chemical Industry Co., Ltd.), dibutyl fumarate (Tokyo Chemical Industry Co., Ltd.), or 7-ethyl-2-methyl-4-undecanol (Tokyo Chemical Industry Co., Ltd.) was used instead of dimethyl phthalate.

[0180] The Balaban index, molar refractive index and boiling point of the solvents used above are summarized in Table 1.

[0181] [3] Measurement of Fluorescence Intensity of Solvent-Immersed PL Intensity Measurement Substrates The prepared PL intensity measurement substrates were evaluated using the following method. The fluorescence intensity of each PL intensity measurement substrate obtained above was evaluated using a spectrofluorometer. The measurement conditions for the spectrofluorometer were an excitation wavelength of 360 nm, a measurement wavelength range of 380 to 700 nm, and a photomultiplier voltage of 400 V. The peak-top fluorescence intensity and wavelength at that time for each solvent-immersed PL intensity measurement substrate, relative to the PL intensity of the PL intensity measurement substrate of Reference Example 1 as 100, are shown in Table 1.

[0182]

[0183] As shown in Table 1, it was shown that the fluorescence intensity decreases when the quantum dot layer is immersed in a solvent whose Balaban index or molar refractive index is outside the specified value. From the above, it was found that the decrease in fluorescence intensity can be suppressed by using the solvent according to the present invention.

[0184] [4] Production of Metal Oxide Nanoparticle Sol [Production Example 1] Preparation of Ethanol Dispersion Sol (A) of Zinc Magnesium Oxide Nanoparticles An ethanol sol of zinc magnesium oxide nanoparticles was synthesized by the method described in Chem. Commun., 2019, 55, 13299-13302. The obtained sol was an ethanol dispersion sol (A) of zinc magnesium oxide nanoparticles, and had a total metal oxide (ZnO and MgO) concentration of 10.0 mass% and an average particle diameter of 10 nm as measured by dynamic light scattering (DLS).

[0185] [Production Example 2] Preparation of stannic oxide composite oxide colloidal particles (B) serving as cores 37.5 kg of oxalic acid ((COOH)2·2H2O) was dissolved in 363 kg of pure water, and the resulting solution was heated to 70°C with stirring, followed by the addition of 170 kg of 35% by weight hydrogen peroxide and 75 kg of metallic tin. The hydrogen peroxide and metallic tin were added alternately in predetermined amounts according to the following procedure: First, 10 kg of 35% by weight hydrogen peroxide was added, followed by the addition of 5 kg of metallic tin. This procedure was repeated after waiting for the reaction to finish (5 to 10 minutes). After the entire amount was added, an additional 10 kg of 35% by weight hydrogen peroxide was added. The addition took 3 hours, and after the addition was completed, the mixture was heated at 95°C for an additional 1 hour to terminate the reaction. To 629 kg of the resulting sol, 231 kg of 35% by mass hydrogen peroxide solution and 52 kg of pure water were added, and the mixture was diluted to 10% by mass in terms of SnO2 and an H2O2 / (COOH)2 molar ratio of 8.0 relative to the oxalic acid at the time of charging, and aged for 5 hours at 95°C. This procedure decomposed the contained oxalic acid into carbon dioxide and water by reaction with hydrogen peroxide. The resulting stannic oxide slurry was cooled to approximately 40°C, and 2.7 kg of isopropylamine was added. After peptization, the slurry was passed through a catalyst column packed with approximately 15 L of a platinum-based catalyst (N-220 (manufactured by Süd-Chemie Catalysts Co., Ltd.)) and circulated to decompose excess hydrogen peroxide. The slurry was circulated at a flow rate of approximately 30 L / min for 5 hours, passed through a column packed with anion exchange resin, and then concentrated by ultrafiltration. The obtained sol was an aqueous dispersion sol of alkaline stannic oxide composite oxide colloidal particles (B), with an SnO2 concentration of 10.0 mass % and a primary particle diameter of 10 to 15 nm as determined by observation with a transmission electron microscope.

[0186] [Production Example 3] Preparation of aqueous dispersion sol (C) of titanium oxide-zirconium oxide-tin oxide colloidal particles as cores 104.4 kg (28.6 kg in terms of TiO) of titanium tetrachloride (27.2% by mass in terms of TiO, 32.0% by mass of Cl, manufactured by Sumitomo Sitix Co., Ltd.) and 182.0 kg of water were placed in a reaction vessel equipped with a stirring blade to prepare 286.4 kg of aqueous titanium chloride solution (10.0% by mass in terms of TiO). 10.56 kg (4.4 kg in terms of ZrO) of zirconium carbonate (41.7% by mass in terms of ZrO) was then added to prepare a titanium chloride-zirconium carbonate composite aqueous solution. This aqueous solution was heated to 60°C while stirring in a reaction vessel equipped with a stirring blade. Then, while cooling, 132.1 kg of 35% by mass aqueous hydrogen peroxide (industrial grade) and 80.5 kg of metallic tin powder (manufactured by Yamaishi Metals Co., Ltd., product name AT-Sn, No. 200) were added in portions according to the procedure described below. First, 7.34 kg of aqueous hydrogen peroxide was gradually added, followed by 4.47 kg of metallic tin. After waiting for the reaction resulting from the addition to be complete (15 to 20 minutes), 7.34 kg of aqueous hydrogen peroxide was gradually added, followed by 4.47 kg of metallic tin. This process of adding aqueous hydrogen peroxide followed by metallic tin was repeated 18 times at intervals of 15 to 20 minutes, resulting in 18 separate additions (7.34 kg of aqueous hydrogen peroxide and 4.47 kg of metallic tin). After the separate additions were completed, 9.00 kg of aqueous hydrogen peroxide was added. The mixture was then stirred and heated at 90°C for 3 hours. This step yielded 518.6 kg of an aqueous solution of titanium-zirconium-tin composite salt. 1,091 kg of water was added to 259.3 kg of the obtained aqueous solution of titanium-zirconium-tin composite salt for dilution. Thereafter, 2.00 kg of aqueous hydrogen peroxide was added. This aqueous solution was subjected to hydrolysis at 96 to 98°C for 10 hours to obtain a slurry of aggregates of titanium oxide-zirconium oxide-tin oxide composite colloid. The obtained slurry of aggregates of titanium oxide-zirconium oxide-tin oxide composite colloid was subjected to repeated cycles of concentration, water injection, and concentration using approximately 12,000 L of water in an ultrafiltration apparatus, and excess electrolyte was removed by washing, followed by peptization to obtain 1,298 kg of an acidic aqueous sol of titanium oxide-zirconium oxide-tin oxide composite sol.The obtained sol was a water-dispersed sol (C) of titanium oxide-zirconium oxide-tin oxide composite colloid, and had a total metal oxide concentration (TiO2, ZrO2, and SnO2) of 4.9 mass % and a primary particle diameter of 3 to 10 nm as determined by observation with a transmission electron microscope.

[0187] [Production Example 4] Preparation of antimony pentoxide colloidal particles (D1) to be used as a coating material. 12.5 kg of antimony trioxide (containing 99.5% by weight as SbO), 66.0 kg of pure water, and 12.5 kg of potassium hydroxide (containing 95% by weight as KOH) were added to a 100 L vessel, and 8.4 kg of 35% by weight hydrogen peroxide was gradually added with stirring. 17.6 kg of the resulting potassium antimonate aqueous solution was diluted to 2.2% by weight and passed through a column packed with hydrogen cation exchange resin. 0.25 kg of diisopropylamine was added to the ion-exchanged antimonic acid solution with stirring. The resulting sol was an aqueous dispersion of antimony pentoxide colloidal particles (D1). The SbO concentration was 1.5% by weight, and the primary particle size was 1-10 nm as observed by transmission electron microscopy.

[0188] [Production Example 5] Preparation of silicon dioxide-stannic oxide composite oxide colloidal particles (E1) to serve as a coating material. 77.2 g of JIS No. 3 sodium silicate (containing 29.8% by mass, calculated as SiO) was dissolved in 668.8 g of pure water, followed by the dissolution of 20.9 g of sodium stannate NaSnO3·H2O (containing 55.1% by mass, calculated as SnO2). The resulting aqueous solution was passed through a column packed with a hydrogen cation exchange resin. Next, 7.2 g of diisopropylamine was added to the resulting aqueous sol. The resulting sol was an aqueous dispersion of silicon dioxide-stannic oxide composite oxide colloidal particles (E1), with a total metal oxide concentration (SnO2 and SiO2) of 2.8% by mass and a primary particle diameter of 1 to 4 nm as determined by observation with a transmission electron microscope.

[0189] [Production Example 6] Preparation of an Ethanol Dispersion Sol (D4) of Stannic Oxide Composite Oxide Colloid Particles Coated with Antimony Pentoxide The aqueous dispersion sol of alkaline stannic oxide composite oxide colloid particles (B) prepared in Production Example 2 was continuously subjected to hydrothermal treatment at a treatment temperature of 310 °C, a treatment pressure of 20 MPa, and an average flow rate of 0.6 L / min. Next, with stirring, 400 g of the aqueous dispersion sol of antimony pentoxide colloid particles (D1) prepared in Reference Example 3 (6.0 g of SbO, 5.0% by mass relative to the core particles) was added to 1,200 g of the obtained aqueous dispersion sol of alkaline stannic oxide composite oxide colloid particles (120 g of SnO), and the mixture was then aged at 95 °C for 2 hours to obtain an aqueous dispersion sol of stannic oxide composite oxide colloid particles (D2) coated with antimony pentoxide colloid particles. The obtained aqueous dispersion sol was then passed through a column packed with a hydrogen cation exchange resin. To the resulting aqueous dispersion sol, 3.8 g of tri-n-pentylamine was added and concentrated using an ultrafiltration membrane. The resulting sol was an aqueous dispersion sol of stannic oxide composite oxide colloidal particles (D3) coated with antimony pentoxide colloidal particles, with a total metal oxide (SnO2 and Sb2O5) concentration of 30.2% by mass and an average particle size of 16 nm as measured by dynamic light scattering (DLS). 100 g of the aqueous dispersion sol of stannic oxide composite oxide colloidal particles (D3) coated with antimony pentoxide was substituted with ethanol using a rotary evaporator to obtain an ethanol dispersion sol of stannic oxide composite oxide colloidal particles (D4) coated with antimony pentoxide. The resulting sol had a total metal oxide (SnO2 and SiO2) concentration of 10.0% by mass and an average particle size of 21 nm as measured by dynamic light scattering (DLS).

[0190] Production Example 7 Preparation of Ethanol Dispersion Sol (E4) of Titanium Oxide-Zirconium Oxide-Tin Oxide Colloidal Particles Coated with Silicon Dioxide-Stannic Oxide Composite Oxide 167.8 g of water was added to 272.2 g of the aqueous dispersion sol (C) of the acidic titanium oxide-zirconium oxide-tin oxide composite aqueous sol prepared in Production Example 3, and the mixture was diluted to a total metal oxide (TiO, ZrO, and SnO) concentration of 3 mass%. 0.39 g of isopropylamine was added to this diluted aqueous sol, and the mixture was passed through a column packed with 450 mL of anion exchange resin (Amberlite IRA-410, manufactured by Organo Corporation) to obtain 559.8 g of alkaline titanium oxide-zirconium oxide-tin oxide composite aqueous sol. To this alkaline titanium oxide-zirconium oxide-tin oxide composite aqueous sol was added 61.7 g of an aqueous dispersion sol of silicon dioxide-stannic oxide composite oxide colloidal particles (E1) prepared in Production Example 5 (1.7 g of total metal oxide concentration (SnO2 and SiO2), 15% by mass relative to the core particles), and the mixture was then aged at 95°C for 5 hours to obtain an aqueous dispersion sol (E2) of stannic oxide composite oxide colloidal particles coated with silicon dioxide-stannic oxide composite oxide. The obtained aqueous dispersion sol was then passed through a column packed with a hydrogen cation exchange resin. 0.2 g of tri-n-pentylamine was added to the obtained aqueous dispersion sol, and the mixture was concentrated by ultrafiltration membrane method. The resulting sol was an aqueous dispersion sol (E3) of titanium oxide-zirconium oxide-tin oxide colloidal particles coated with silicon dioxide-stannic oxide composite oxide, with a total metal oxide (TiO2, ZrO2, SnO2, and SiO2) concentration of 1.78% by mass and an average particle size of 28 nm as measured by dynamic light scattering (DLS). 307 g of the aqueous dispersion sol (E3) of titanium oxide-zirconium oxide-tin oxide colloidal particles coated with silicon dioxide-stannic oxide composite oxide was evaporated with ethanol to obtain an ethanol dispersion sol (E4) of titanium oxide-zirconium oxide-tin oxide colloidal particles coated with silicon dioxide-stannic oxide composite oxide. The resulting sol had a total metal oxide (TiO2, ZrO2, SnO2, and SiO2) concentration of 10.0% by mass and an average particle size of 28 nm as measured by dynamic light scattering (DLS).

[0191] [Production Example 8] Production of silica sol 39.2 g of ST-OS (Nissan Chemical Industries, Ltd.), which is a water-dispersed silica sol, and 31.4 g of diethylene glycol (Kanto Chemical Industry Co., Ltd.) were placed in a recovery flask, and the water contained in the ST-OS was solvent-substituted with diethylene glycol using an evaporator. Thereafter, the mixture was filtered through a PTFE filter with a pore size of 1.0 μm to obtain a diethylene glycol-dispersed silica sol (solid content concentration: 20.3% by mass).

[0192] [Production Example 9] Production of silica sol A silica sol dispersed in ethylene glycol (solid content concentration: 20.5% by mass) was obtained in the same manner as in Production Example 8, except that 31.0 g of ethylene glycol (manufactured by Kanto Chemical Co., Inc.) was used instead of 31.4 g of diethylene glycol (manufactured by Kanto Chemical Co., Inc.).

[0193] [4] Measurement of Fluorescence Intensity of Charge-Transporting Material-Laminated PL Intensity Measurement Substrate [Example 1-1] In a glove box environment, a quantum dot dispersion (QNA Corporation, trade name PureBlue.dots in Toluene_v2, toluene dispersion, concentration 3% by mass) was applied to a glass substrate using a spin coater. Then, baked at 100 ° C. for 10 minutes under a nitrogen atmosphere to form a quantum dot thin film layer with a film thickness of 40 nm on the substrate. To the glass substrate on which the obtained quantum dot thin film layer was formed, 1.40 g of dipropylene glycol butyl ether was added to 0.60 g of the ethanol dispersion sol (A) of zinc oxide magnesium nanoparticles prepared in Production Example 1, stirred, and filtered through a PP syringe filter with a pore size of 0.2 μm. A charge-transporting ink composition (3.0% by mass as metal oxide) was applied to the quantum dot thin film layer using a spin coater. Then, baked at 140 ° C. for 15 minutes under a nitrogen atmosphere and dried to form a quantum dot thin film layer laminated with a charge-transporting material. Thereafter, in order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the ITO substrate and a desiccant (manufactured by Dynic Co., Ltd., product name HD-071010W-40) were placed between sealing substrates (manufactured by Premium Glass Co., Ltd., cell size 19 mm × 21 mm × 0.7 mm, excavation 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, and the sealing substrates were bonded together using an adhesive (manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)), and the sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm). 2 This was used as a substrate for measuring the PL intensity of the charge transport material laminate.

[0194] Examples 1-2 to 1-4 Charge-transporting material-laminated PL intensity measurement substrates were prepared in the same manner as in Example 1-1, except that 1,2-hexanediol, diethylene glycol, and propylene carbonate were used instead of dipropylene glycol butyl ether.

[0195] Examples 1-5 to 1-8 Substrates for measuring PL intensity of charge-transporting materials were prepared in the same manner as in Examples 1-1 to 1-4, except that an ethanol dispersion sol of stannic oxide composite oxide colloidal particles (D4) coated with antimony pentoxide was used instead of the ethanol dispersion sol of zinc magnesium oxide nanoparticles (A).

[0196] Examples 1-9 to 1-12 Substrates for measuring the intensity of charge-transporting material-laminated PL were prepared in the same manner as in Examples 1-1 to 1-4, except that an ethanol dispersion sol (E4) of titanium oxide-zirconium oxide-tin oxide colloidal particles coated with silicon dioxide-stannic oxide composite oxide was used instead of the ethanol dispersion sol (A) of zinc magnesium oxide nanoparticles.

[0197] Comparative Examples 1-1 to 1-3 Substrates for measuring the PL intensity of charge transporting materials were prepared in the same manner as in Examples 2-1, 2-5, and 2-9, except that tripropylene glycol monomethyl ether was used instead of dipropylene glycol butyl ether.

[0198] The fluorescence intensity of the charge-transporting material-laminated PL intensity measurement substrate prepared above was measured. The measurement conditions were the same as those for measuring the fluorescence intensity of the solvent-immersed PL intensity measurement substrate. The results are shown in Table 2.

[0199] * 1: Ethanol dispersion sol of zinc magnesium oxide nanoparticles (A) * 2: Ethanol dispersion sol of stannic oxide composite oxide colloidal particles coated with antimony pentoxide (D4) * 3: Ethanol dispersion sol of titanium oxide-zirconium oxide-tin oxide colloidal particles coated with silicon dioxide-stannic oxide composite oxide (E4)

[0200] As shown in Table 2, when a charge transport ink composition using a solvent whose Balaban index or molar refractive index is outside the specified value is applied as a layer on top of a quantum dot layer, the fluorescence intensity is reduced. From the above, it was found that the use of the solvent according to the present invention in the charge transport ink composition can suppress the reduction in fluorescence intensity.

[0201] [5] Preparation of Positive Photosensitive Resin Composition (1) Synthesis of Acrylic Polymer [Reference Synthesis Example 1] 10.0 g of MMA, 12.5 g of HEMA, 20.0 g of CHMI, 2.50 g of HPMA, 5.00 g of MAA, and 3.20 g of AIBN were dissolved in 79.8 g of PGME and reacted at 60 to 100°C for 20 hours to obtain an acrylic polymer solution (solid concentration 40% by mass) (P1). The resulting acrylic polymer P1 had an Mn of 3,700 and an Mw of 6,100.

[0202] [Reference Synthesis Example 2] 2.50 g of HPMA-QD, 7.84 g of PFHMA, 0.70 g of MAA, 1.46 g of CHMI, and 0.33 g of AIBN were dissolved in 51.3 g of CHN and reacted with stirring at 110°C for 20 hours to obtain an acrylic polymer solution (solids concentration: 20% by mass) (P2). The resulting acrylic polymer P2 had an Mn of 4,300 and an Mw of 6,300.

[0203] (2) Production of Positive Photosensitive Resin Composition [Production Example 10] 5.04 g of P1 obtained in Reference Synthesis Example 1, 0.05 g of P2 obtained in Reference Synthesis Example 2, 0.40 g of QD1, 0.09 g of GT-401, and 6.42 g of PGMEA were mixed and stirred at room temperature for 3 hours to obtain a homogeneous solution, thereby obtaining a positive photosensitive resin composition.

[0204] [6] Evaluation of Change in Flatness Depending on Delay Time After Inkjet Film Formation [Example 2-1] The positive photosensitive resin composition obtained in Production Example 10 was applied using a spin coater onto plasma-cleaned ITO that had been ozone-cleaned for 10 minutes using UV-312 manufactured by Technovision Co., Ltd., and the substrate was then pre-baked on a hot plate (heated at a temperature of 100°C for 120 seconds) to form a thin film with a thickness of 1.2 μm. This thin film was irradiated with ultraviolet light (light intensity at 365 nm: 5.5 mW / cm) using an ultraviolet irradiation device PLA-600FA manufactured by Canon Inc., through a mask with a pattern of many rectangles with long sides of 200 μm and short sides of 100 μm. 2) for a certain period of time. The thin film was then immersed in a 1.0% by mass aqueous solution of TMAH for 120 seconds for development, and then washed with running ultrapure water for 20 seconds. The thin film with the rectangular pattern formed thereon was then post-baked (heated at 230°C for 30 minutes) to harden it, producing a partition-attached substrate. Furthermore, 0.40 g of the ethanol dispersion sol (A) of zinc magnesium oxide nanoparticles prepared in Production Example 1 was evaporated using a rotary evaporator with a mixed solvent of 1.60 g of dipropylene glycol butyl ether and 0.4 g of 1,2-hexanediol to obtain a sol in which zinc magnesium oxide nanoparticles were dispersed in a mixed solvent of 1.60 g of dipropylene glycol butyl ether and 0.4 g of 1,2-hexanediol. This dispersion sol was filtered through a PP syringe filter with a pore size of 0.2 μm to obtain a charge-transporting ink composition (2.0% by mass as metal oxide). The charge-transporting ink composition was ejected onto the prepared partition wall (bank)-equipped substrate using an inkjet system, and the partition wall (bank)-equipped substrate that had been left to stand for 15 minutes, as well as the partition wall (bank)-equipped substrate immediately after ejection, were dried under reduced pressure (vacuum) of 10 Pa or less for 15 minutes. The substrate was then moved into a glove box and baked at 140°C under nitrogen for 15 minutes. This yielded a partition wall (bank)-equipped substrate on which a charge-transporting thin film had been formed after drying with a 15-minute delay, and a partition wall (bank)-equipped substrate on which a charge-transporting thin film had been formed after drying without a delay.

[0205] Comparative Example 2-1 A substrate with partition walls (banks) on which a charge-transporting thin film was formed and dried after a 15-minute delay, and a substrate with partition walls (banks) on which a charge-transporting thin film was formed and dried without a delay, were obtained in the same manner as in Example 2-1, except that a charge-transporting ink composition (2.0 mass % as metal oxide) was used, which was prepared by adding 1.60 g of ethanol to 0.40 g of the ethanol dispersion sol (A) of zinc magnesium oxide nanoparticles prepared in Production Example 1, stirring the mixture, and filtering the mixture through a PP syringe filter having a pore size of 0.2 μm, instead of a sol prepared by dispersing zinc magnesium oxide nanoparticles in a mixed solvent of 1.60 g of dipropylene glycol butyl ether and 0.4 g of 1,2-hexanediol.

[0206] The flatness of the charge transport thin film was evaluated by the following method. The inkjet films obtained in Example 2-1 and Comparative Example 2-1 were evaluated for their surface shapes using a micro-profile measuring instrument. The proportion of the area where the obtained surface shape was within a ratio of -10 to 10% of the film thickness at the center was defined as the flat area. The results are shown in Table 3.

[0207]

[0208] As shown in Table 3, in the charge transport ink composition using a high-boiling point solvent as in the examples, the change in the proportion of flat regions with delay time was small, and the flat regions of the inkjet film were able to be maintained regardless of the delay time. On the other hand, in the charge transport ink composition using a low-boiling point solvent as in the comparative example, the change in the proportion of flat regions with delay time was significantly worsened, and the flat regions of the inkjet film decreased with delay time. This shows that using a high-boiling point solvent in the charge transport ink composition can suppress changes in the flatness of the film due to delay time after inkjet film formation.

[0209] [7] Fabrication of Hole-Only Device (HOD) [Example 3-1] First, an ITO substrate (Foresight Corporation, product name ITO (50 nm) Zebra Substrate_ver. 2.0, 25 mm x 25 mm x 0.7 mm glass substrate with a 50 nm thick ITO film patterned on its surface) was prepared by removing impurities from the substrate surface using an O2 plasma cleaning device at 150 W for 30 seconds. A PEDOT:PSS aqueous dispersion (Heraeus, product name Clevios™) was applied to the substrate as a hole injection layer (HIL) using a spin coater, and the substrate was pre-baked at 80°C for 1 minute in an air atmosphere. This was followed by final baking at 150°C for 30 minutes, forming a 30 nm HIL thin film on the ITO substrate. Next, 0.093 g of 1-amino-2-butanol (Tokyo Chemical Industry Co., Ltd.) and 3.71 g of diethylene glycol were added to 0.034 g of copper iodide (Fujifilm Wako Pure Chemical Industries, Ltd.), and the mixture was stirred for 30 minutes. Thereafter, 0.16 g of the silica sol obtained in Production Example 8 was added, and the mixture was further stirred at room temperature for 30 minutes. The charge transport ink composition (4.0 mass % as solids content) filtered through a PP syringe filter with a pore size of 0.2 μm was applied to the above HIL thin film using a spin coater, and then baked at 200°C for 30 minutes in a nitrogen atmosphere to form a 30 nm HTL thin film on the HIL thin film. A vapor deposition apparatus was used to apply a 30 nm HTL thin film to the surface of the obtained HTL thin film at a vacuum of 1.0 x 10 -5 An 80 nm thick aluminum thin film was formed at a pressure of 0.2 Pa and 0.2 nm / sec. Thereafter, in order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the ITO substrate on which the aluminum thin film was formed and a desiccant (manufactured by Dynic Co., Ltd., product name HD-071010W-40) were placed between sealing substrates (manufactured by Premium Glass Co., Ltd., cell size 19 mm x 21 mm x 0.7 mm, excavation 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, and the sealing substrates were bonded together using an adhesive (manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)). The bonded sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm). 2 After that, the adhesive was cured by annealing at 80° C. for 1 hour. This was used as a hole-only device (HOD).

[0210] Example 3-2 A hole-only device (HOD) was fabricated in the same manner as in Example 3-1, except that ethylene glycol and the silica sol of Production Example 9 were used instead of diethylene glycol and the silica sol of Production Example 8.

[0211] [8] Evaluation of hole-only devices (HOD) The fabricated hole-only devices were evaluated as follows. A voltage of 5 V was applied to each of the hole-only devices obtained above at 25°C and atmospheric pressure for 0.01 seconds, and the current density was measured. The current densities obtained at this time are shown in Table 4.

[0212]

[0213] As shown in Table 4, the hole-only device obtained in this example was found to exhibit a sufficient current density. This indicates that the charge-transporting thin film obtained from the charge-transporting ink composition containing copper iodide and the specific solvent can be satisfactorily used as a hole-transporting layer.

[0214] [8] Fabrication of QDEL Device [Example 4-1] First, an ITO substrate (Foresight Corporation, product name ITO (50 nm) Zebra Substrate_ver. 2.0, 25 mm x 25 mm x 0.7 mm glass substrate with a 50 nm thick ITO film patterned on its surface) was prepared by removing impurities from the substrate surface using an O2 plasma cleaning device at 150 W for 30 seconds. A PEDOT:PSS aqueous dispersion (Heraeus, product name Clevios™) was applied to the substrate as a hole injection layer (HIL) using a spin coater, followed by pre-baking at 80°C for 1 minute in an air atmosphere. This was followed by final baking at 150°C for 30 minutes to form a 30 nm HIL thin film on the ITO substrate. Next, PVK (polyvinylcarbazole, product number 368350, average molecular weight 25,000-50,000, manufactured by Aldrich) dissolved at 0.5% by mass in chlorobenzene (manufactured by Junsei Chemical Co., Ltd.) was applied to the above-mentioned HIL thin film using a spin coater, followed by post-baking for 30 minutes at 200°C in a nitrogen atmosphere to form a 20-nm HTL thin film on the HIL thin film. Next, a quantum dot dispersion (manufactured by QNA, product name PureBlue.dots in Toluene_v2, toluene dispersion, concentration 3% by mass) was applied to the above-mentioned HTL thin film using a spin coater, followed by post-baking for 10 minutes at 100°C in a nitrogen atmosphere to form a 40-nm EmL thin film on the HTL thin film. Next, the charge transporting ink composition used in Example 1-1 as an electron transport layer (ETL) was applied onto the EmL thin film using a spin coater, and then pre-baked at 100°C for 30 seconds in a nitrogen atmosphere. Then, the pre-baked layer was baked at 140°C for 15 minutes to form a 40 nm ETL thin film on the EmL thin film. A vacuum evaporation apparatus was used to apply a 40 nm ETL thin film onto the surface of the obtained ETL thin film. -5An 80 nm thick aluminum thin film was formed at a pressure of 0.2 Pa and 0.2 nm / sec. Thereafter, in order to prevent deterioration of characteristics due to the influence of oxygen, water, etc. in the air, the ITO substrate on which the aluminum thin film was formed and a desiccant (manufactured by Dynic Co., Ltd., product name HD-071010W-40) were placed between sealing substrates (manufactured by Premium Glass Co., Ltd., cell size 19 mm x 21 mm x 0.7 mm, excavation 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, and the sealing substrates were bonded together using an adhesive (manufactured by MORESCO Co., Ltd., product name MORESCO Moisture Cut WB90US(P)). The bonded sealing substrates were irradiated with UV light (wavelength: 365 nm, irradiation dose: 6,000 mJ / cm). 2 After the bonding, the adhesive was cured by annealing at 80° C. for 1 hour to obtain a QDEL device that emits blue light.

[0215] Examples 4-2 to 4-4 QDEL devices were fabricated in the same manner as in Example 4-1, except that the charge transporting ink composition used in Examples 1-2 to 1-4 was used instead of the charge transporting ink composition used in Example 1-1.

[0216] [9] Evaluation of QDEL Device The fabricated QDEL device was evaluated by the following method. The current density and luminescence intensity were measured when a voltage of 0 to 12 V at 0.25 V intervals was applied to the QDEL device obtained above for 0.01 seconds at 25°C and atmospheric pressure. From the obtained measurement data, the voltage, current efficiency, and external quantum efficiency at which 10 cd of luminescence was observed were calculated. The results are shown in Table 5. The external quantum efficiency was calculated using the following formula (3): External quantum efficiency = 8.06 × 10 5 × P × λ / I ... Equation (3) (P is the luminous intensity [W / m 2 ], λ is the wavelength [m], and I is the current [A].

[0217] * 1: Ethanol dispersion sol of zinc magnesium oxide nanoparticles (A)

[0218] As shown in Table 5, the QDEL device obtained in this example was found to emit blue light, demonstrating that the charge-transporting thin film obtained from the charge-transporting ink composition containing metal oxide nanoparticles and a specific solvent can be satisfactorily used as an electron-transporting layer.

Claims

1. A charge transport ink composition for use as an upper layer of a quantum dot layer, comprising a charge transport material and a solvent, wherein the solvent comprises a specific solvent having a Balaban index of 3.3 or less, a molar refractive index of 65 or less, and a boiling point of 180°C or higher.

2. The charge transporting ink composition according to claim 1, wherein the specific solvent contains two or more oxygen atoms in the molecule.

3. The charge transport ink composition according to claim 1, wherein the charge transport material is one or more metal oxide nanoparticles selected from the group consisting of oxides of metals selected from the group consisting of Zn, Mg, Ti, Fe, Zr, Sn, Ta, Nb, Y, Mo, W, Pb, In, Bi and Sr, and complexes of at least two of these metals.

4. The charge transporting ink composition according to claim 3, which is a surface-treated metal oxide nanoparticle having the metal oxide nanoparticle as a core, the surface of which is coated with one or more species selected from the group consisting of metal oxides and surface treatment agents.

5. The charge transporting ink composition according to claim 4, wherein the surface treatment agent is at least one selected from the group consisting of compounds represented by the following formulas (S1) to (S9): (In formula (S1), R 1s are each independently an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 are bonded to a silicon atom by a Si—C bond; R 2s each independently represents an alkoxy group, an acyloxy group, or a halogen atom, and a1 represents an integer of 1 to 3. In formulas (S2) and (S3), R 3s and R 5s are each independently an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 30 carbon atoms, and R 4s and R 6s each independently represents an alkoxy group, an acyloxy group, or a halogen atom; Y s represents an alkylene group, an NH group, or an oxygen atom, b1 represents an integer of 1 to 3, c1 represents 0 or 1, and d1 represents an integer of 1 to 3. In formula (S4), R 7s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 e1 represents 1 or 2. 8s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 9s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 10s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 11s represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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. 12s represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; R 13s represents a hydrogen atom, an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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; Z s represents an oxygen atom or a sulfur atom. 14s each independently represents an alkyl group, a halogenated alkyl group, an alkenyl group, an aryl group, or an organic group having 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 f1 represents 1 or 2.

6. The charge transporting ink composition according to claim 3, wherein said metal oxide nanoparticles are ZnO, a ZnO-MgO composite, SnO2 or a SnO2-TiO2-ZrO2 composite.

7. The charge transporting ink composition according to claim 4, wherein said metal oxide is at least one selected from the group consisting of In2O3, Sb2O5, SiO2, SnO2, TiO2, WO3, ZnO, ZrO2 and complexes of at least two of these.

8. The charge transporting ink composition according to claim 7, wherein said metal oxide is SnO2, Sb2O5 or a SnO2-SiO2 composite.

9. The charge transporting ink composition according to claim 1, wherein said charge transporting substance is a copper(I) halide or a pseudocopper(I) halide.

10. The charge transporting ink composition according to claim 9, wherein said copper(I) halide or pseudocopper(I) halide is copper(I) halide or copper(I) thiocyanate.

11. The charge transporting ink composition according to claim 9, wherein said copper(I) halide is copper(I) iodide.

12. A charge transporting thin film obtained from the charge transporting ink composition according to any one of claims 1 to 11.

13. An electronic device comprising the charge transport thin film according to claim 12.

14. The electronic device according to claim 13, wherein the charge transporting thin film is an electron transporting layer or a hole transporting layer.

15. The electronic device according to claim 14, wherein said electronic device is a quantum dot EL device.

16. A method for producing a charge transporting thin film, comprising applying the charge transporting ink composition according to any one of claims 1 to 11 onto a substrate and evaporating the solvent.

17. The method for producing a charge transporting thin film according to claim 16, wherein the substrate is a quantum dot layer.

Images