metal oxide dispersion

Abstract

To provide a metal oxide dispersion having excellent stability over time and suppressing generation of a solvent shock.SOLUTION: A metal oxide dispersion according to the present invention comprises: a first carboxylic acid which is at least one kind of aromatic carboxylic acid selected from the group consisting of an aromatic carboxylic acid having an aromatic ring substituted with an alkyl group, an aromatic carboxylic acid having an aromatic ring substituted with an alkoxy group, an aromatic carboxylic acid having an aromatic ring substituted with an alkoxycarbonyl group, and an aromatic carboxylic acid having an aromatic ring substituted with an acyloxy group; metal oxide nanoparticles surface-treated with a capping agent; and a solvent. The capping agent comprises a second carboxylic acid having an ester bond and a polymerizable double bond. The second carboxylic acid is different from the first carboxylic acid.SELECTED DRAWING: None

Description

Technical Field

[0006] , , ,

[0005] , ,

[0001] The present invention relates to a metal oxide dispersion.

Background Art

[0002] A metal oxide film used for a hard mask or the like can be formed by forming a film from a metal oxide dispersion by a liquid-phase coating method such as a spin coating method or an inkjet method. As the metal oxide dispersion, for example, a coating composition containing an organic solvent, metal oxide nanoparticles dispersed in this organic solvent, and a high-carbon polymer having a specific structure dissolved in this solvent is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an apparatus for applying a metal oxide dispersion, a solvent such as butyl acetate or γ-butyrolactone is used in a process such as pipe cleaning or pre-wetting. At that time, it is required that the metal oxide dispersion is suppressed from becoming turbid or generating precipitation over time due to the addition of the above solvent, that is, the occurrence of solvent shock. On the other hand, the metal oxide dispersion is also required to have excellent stability over time.

[0005] The present invention has been made in view of such a conventional situation, and an object thereof is to provide a metal oxide dispersion having excellent stability over time and suppressing the occurrence of solvent shock.

Means for Solving the Problems

[0006] The inventors diligently conducted research to solve the above problems. As a result, they discovered that the above problems can be solved by a metal oxide dispersion containing a first carboxylic acid which is a predetermined aromatic carboxylic acid, metal oxide nanoparticles surface-treated with a capping agent, and a solvent, wherein the capping agent contains a second carboxylic acid having an ester bond and a polymerizable double bond, and the second carboxylic acid is a different metal oxide dispersion from the first carboxylic acid, thus completing the present invention. Specifically, the present invention provides the following.

[0007] One aspect of the present invention is, A first carboxylic acid is at least one aromatic carboxylic acid selected from the group consisting of aromatic carboxylic acids having an aromatic ring substituted with an alkyl group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxy group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxycarbonyl group, and aromatic carboxylic acids having an aromatic ring substituted with an acyloxy group, Metal oxide nanoparticles surface-treated with a capping agent, Solvents and, A metal oxide dispersion containing, The capping agent comprises a second carboxylic acid having an ester bond and a polymerizable double bond, The second carboxylic acid is different from the first carboxylic acid. It is a dispersion of metal oxides. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a metal oxide dispersion that has excellent temporal stability and suppresses the occurrence of solvent shock. [Modes for carrying out the invention]

[0009] <Metal oxide dispersion> The metal oxide dispersion according to the present invention contains a first carboxylic acid, which is at least one aromatic carboxylic acid selected from the group consisting of aromatic carboxylic acids having an aromatic ring substituted with an alkyl group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxy group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxycarbonyl group, and aromatic carboxylic acids having an aromatic ring substituted with an acyloxy group; metal oxide nanoparticles surface-treated with a capping agent; and a solvent, wherein the capping agent contains a second carboxylic acid having an ester bond and a polymerizable double bond, and the second carboxylic acid is different from the first carboxylic acid. The metal oxide dispersion according to the present invention has excellent long-term stability and suppresses the occurrence of solvent shock.

[0010] In the solid content of the metal oxide dispersion, the ratio of the inorganic content to the total of the inorganic and organic content is 25% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more. When this ratio is within the above range, the ratio of inorganic content can be set high, and as a result, it is easy to improve the ratio of inorganic content in the metal oxide dispersion. The upper limit of this ratio is not particularly limited and may be 90% by mass, 80% by mass, or 75% by mass.

[0011] [First carboxylic acid] The first carboxylic acid is at least one aromatic carboxylic acid selected from the group consisting of aromatic carboxylic acids having an aromatic ring substituted with an alkyl group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxy group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxycarbonyl group, and aromatic carboxylic acids having an aromatic ring substituted with an acyloxy group. The first carboxylic acid may be used alone or in combination of two or more types.

[0012] The aromatic rings possessed by the first type of aromatic carboxylic acid are not particularly limited, and examples include benzene rings, naphthalene rings, anthracene rings, and biphenyl rings. From the viewpoint of improving stability over time and suppressing the occurrence of solvent shock, benzene rings are preferred.

[0013] The alkyl group described above may be linear or branched, and examples include alkyl groups having 1 to 18 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, n-pentyl group, isopentyl group, sec-pentyl group, tert-pentyl group, n-hexyl group, isohexyl group, sec-hexyl group, and tert-hexyl group. Alkyl groups having 2 to 8 carbon atoms are preferred, and alkyl groups having 3 to 6 carbon atoms are more preferred.

[0014] The alkyl group included in the above alkoxy group is the same as described above.

[0015] The alkyl group contained in the above alkoxycarbonyl group is the same as described above.

[0016] Examples of the above-mentioned acyloxy groups include acyloxy groups having 1 to 18 carbon atoms, such as formyloxy, acetyloxy, propionyloxy, n-butyryloxy, isobutyryloxy, and benzoyloxy groups. Acyloxy groups having 2 to 8 carbon atoms are preferred, and acyloxy groups having 3 to 6 carbon atoms are more preferred.

[0017] Specific examples of the first carboxylic acid include 4-methylbenzoic acid, 4-ethylbenzoic acid, 4-n-propylbenzoic acid, 4-n-butylbenzoic acid, 4-n-pentylbenzoic acid, 4-n-hexylbenzoic acid, 4-methoxybenzoic acid, 4-ethoxyethylbenzoic acid, 4-n-propoxybenzoic acid, 2-n-propoxybenzoic acid, 4-n-butoxybenzoic acid, 4-(n-hexyloxy)benzoic acid, 4-n-pentyl-4'-biphenylcarboxylic acid, and phthalic acid. Examples include mono-n-hexyl acids, and from the viewpoint of improving stability over time and suppressing the occurrence of solvent shock, 4-n-propylbenzoic acid, 4-n-butylbenzoic acid, 4-n-pentylbenzoic acid, 4-n-hexylbenzoic acid, 4-n-propoxybenzoic acid, 2-n-propoxybenzoic acid, 4-n-butoxybenzoic acid, 4-(n-hexyloxy)benzoic acid, 4-n-pentyl-4'-biphenylcarboxylic acid, and mono-n-hexyl phthalates are preferred.

[0018] The amount of the first carboxylic acid used is not particularly limited, but is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and even more preferably 5 to 10% by mass, relative to the total amount of components other than the solvent in the metal oxide dispersion. When the amount of the first carboxylic acid used is within the above range, the metal oxide dispersion tends to have improved stability over time and the occurrence of solvent shock tends to be suppressed.

[0019] The first carboxylic acid is present in the metal oxide dispersion and / or in the capping agent, separately from the metal oxide nanoparticles. That is, the first carboxylic acid may cover the metal oxide nanoparticles in the same way as the capping agent, or it may be present in the metal oxide dispersion in a free state.

[0020] The ratio of the mass of the first carboxylic acid present in the metal oxide dispersion separately from the metal oxide nanoparticles to the mass of the solid content of the metal oxide dispersion is preferably 10% by mass or less, more preferably 1 to 9% by mass, and even more preferably 3 to 8% by mass. When the above ratio is within the above range, the metal oxide dispersion is likely to have improved stability over time and is likely to suppress the occurrence of solvent shock.

[0021] [Metal oxide nanoparticles surface-treated with a capping agent] The metal oxide dispersion contains metal oxide nanoparticles surface-treated with a capping agent. In the present specification, the metal oxide nanoparticles are composed of a metal oxide and do not contain a capping agent. The capping agent contains a second carboxylic acid having an ester bond and a polymerizable double bond, and the second carboxylic acid is different from the first carboxylic acid. The metal oxide nanoparticles surface-treated with a capping agent may be used alone or in combination of two or more. When the metal oxide dispersion contains metal oxide nanoparticles surface-treated with a capping agent, the metal oxide dispersion is likely to have improved stability over time and is likely to suppress the occurrence of solvent shock.

[0022] The average particle diameter of the metal oxide nanoparticles is preferably 5 nm or less, more preferably 4 nm or less, and even more preferably 3 nm or less. The lower limit of the average particle diameter of the metal oxide nanoparticles is not particularly limited, and may be, for example, 0.5 nm or more, 1 nm or more, or 2 nm or more. When the average particle diameter of the metal oxide nanoparticles is within the above range, the metal oxide dispersion is more likely to have improved stability over time and is more likely to suppress the occurrence of solvent shock. In the present specification, the average particle diameter of the metal oxide nanoparticles refers to the value obtained by performing XRD measurement with an X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation), analyzing the obtained results with PDXL of the attached software, and using the Halder-Wagner method.

[0023] The average particle size of metal oxide nanoparticles surface-treated with a capping agent is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 6 nm or less. The lower limit is not particularly limited and may be, for example, 0.5 nm or more, 1 nm or more, or 2 nm or more. In this specification, the average particle size of metal oxide nanoparticles surface-treated with a capping agent refers to the value measured by a dynamic light scattering (DLS) instrument such as a Malvern Zetasizer Nano S.

[0024] The metals included in the metal oxide nanoparticles are not particularly limited, and examples include zinc, yttrium, hafnium, zirconium, lanthanum, cerium, neodymium, gadolinium, holmium, lutetium, tantalum, titanium, silicon, aluminum, antimony, tin, indium, tungsten, copper, vanadium, chromium, niobium, molybdenum, ruthenium, rhodium, rhenium, iridium, germanium, gallium, thallium, and magnesium. From the viewpoint of film-forming properties and stability, hafnium, zirconium, titanium, and tin are preferred, with zirconium being more preferred. The above metals may be used individually or in combination of two or more.

[0025] Metal oxide nanoparticles may consist of metal atoms and oxygen atoms, or they may consist of metal atoms, oxygen atoms, and atoms other than metal atoms and oxygen atoms. Examples of atoms other than metal atoms and oxygen atoms include nitrogen atoms. Therefore, metal oxide nanoparticles may consist of metal oxides or metal oxynitrides, etc.

[0026] In the metal oxide dispersion according to the present invention, it is presumed that part or all of the surface of the metal oxide nanoparticles is covered with a capping agent. The capping agent contains a second carboxylic acid having an ester bond and a polymerizable double bond, and the second carboxylic acid is different from the first carboxylic acid. In the metal oxide dispersion according to the present invention, when the metal oxide nanoparticles are surface-treated with the capping agent, the dispersibility of the metal oxide nanoparticles in the solvent is more stable, the stability of the metal oxide dispersion over time is more easily improved, and the occurrence of solvent shock is more easily suppressed.

[0027] The second carboxylic acid is not particularly limited as long as it has an ester bond and a polymerizable double bond. For example, it is a carboxylic acid in which one hydroxyl group in the polyol and one carboxyl group in the polycarboxylic acid form an ester bond, and another hydroxyl group in the polyol and a carboxyl group in (meth)acrylic acid form an ester bond. More specifically, it is a carboxylic acid in which one hydroxyl group in a diol such as ethylene glycol and one carboxyl group in a dicarboxylic acid such as succinic acid or phthalic acid form an ester bond, and another hydroxyl group in the diol and a carboxyl group in (meth)acrylic acid form an ester bond. The second carboxylic acid may be used alone or in combination of two or more.

[0028] The second carboxylic acid may have an aromatic ring. When the second carboxylic acid has an aromatic ring, the occurrence of solvent shock in the metal oxide dispersion is more easily suppressed. The aromatic ring is not particularly limited and examples include a benzene ring, naphthalene ring, anthracene ring, biphenyl ring, etc., but a benzene ring is preferred from the viewpoint of reactivity with the capping agent and metal oxide nanoparticles.

[0029] Specific examples of the second carboxylic acid include 2-acryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl phthalic acid, 2-acryloyloxyethyl succinic acid, and 2-methacryloyloxyethyl succinic acid. From the viewpoint of reactivity with the capping agent and metal oxide nanoparticles, 2-acryloyloxyethyl phthalic acid and 2-acryloyloxyethyl succinic acid are preferred.

[0030] The capping agent may include other capping agents. Examples of other capping agents include at least one selected from the group consisting of alkoxysilanes, phenols, alcohols, carboxylic acids other than the second carboxylic acid, and carboxylic acid halides. Other specific examples of capping agents include n-propyltrimethoxysilane, n-propyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-dodecyltrimethoxysilane, n-dodecyltriethoxysilane, n-hexadecyltrimethoxysilane, n-hexadecyltriethoxysilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenethylphenyltrimethoxysilane, phenethylethyltriethoxysilane, 3-{2-methoxy[poly(ethyleneoxy)]}propyltrimethoxysilane, 3-{2-methoxy[poly(ethyleneoxy)]}propyltriethoxysilane, 3-{2-methoxy[tri(ethyleneoxy)]}propyltrimethoxysilane, 3-{2-methoxy[tri(ethyleneoxy)]}propyltriethoxysilane, vinyltri Alkoxysilanes such as methoxylane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, 1-hexenyltrimethoxysilane, 1-hexenyltriethoxysilane, 1-octenyltrimethoxysilane, 1-octenyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloylpropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; phenols such as phenols;Examples include unsaturated alcohols such as ethanol, n-propanol, isopropanol, n-butanol, n-heptanol, n-hexanol, n-octanol, n-dodecyl alcohol, n-octadecanol, benzyl alcohol, and triethylene glycol monomethyl ether; unsaturated alcohols such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, allyl alcohol, oleyl alcohol, ethylene glycol monoallyl ether, propylene glycol monoallyl ether, and 3-allyloxypropanol; acids such as octanoic acid, acetic acid, propionic acid, 2-[2-(methoxyethoxy)ethoxy]acetic acid, oleic acid, lauric acid, and benzoic acid; and acid halides of these acids, such as acid chlorides of these acids. Preferably, the other capping agents are alkoxysilanes, unsaturated alcohols, or compounds listed as acids. The above other capping agents may be used individually or in combination of two or more.

[0031] The amount of capping agent used when surface-treating metal oxide nanoparticles with a capping agent is not particularly limited. Preferably, a sufficient amount of capping agent is used to react with almost all of the hydroxyl groups on the surface of the metal oxide nanoparticles.

[0032] The content of metal oxide nanoparticles in the metal oxide dispersion is not particularly limited as long as it does not hinder the objective of the present invention, but is preferably 5% to 99% by mass, more preferably 30% to 98% by mass, and even more preferably 60% to 97% by mass, relative to the total amount of components other than the solvent in the metal oxide dispersion. When the content is within the above range, the metal oxide dispersion tends to have improved stability over time and the occurrence of solvent shock tends to be suppressed. The above content of metal oxide nanoparticles includes the content of capping agents present on the surface of the metal oxide nanoparticles.

[0033] [solvent] The metal oxide dispersion according to the present invention contains a solvent for the purpose of adjusting its applicability and viscosity. Typically, an organic solvent is used as the solvent. The type of organic solvent is not particularly limited as long as it can uniformly dissolve or disperse the components contained in the metal oxide dispersion.

[0034] Suitable examples of organic solvents that can be used as solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol n-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, and tri (Poly)alkylene glycol monoalkyl ethers such as propylene glycol monomethyl ether and tripropylene glycol monoethyl ether; (Poly)alkylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; other ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, and tetrahydrofuran; ketones such as methyl ethyl ketone, cyclohexanone, 2-heptanone, and 3-heptanone; alkyl lactate esters such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate;Other esters such as ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methyl carbonate, methyl-3-methoxybutyl acetate, methyl-3-methoxybutylpropionate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl formate, isopentyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, n-butyl butyrate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, ethyl 2-oxobutanoate, and other esters; aromatic hydrocarbons such as toluene and xylene; amides such as N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. These organic solvents can be used individually or in combination of two or more.

[0035] The amount of solvent used in the metal oxide dispersion according to the present invention is not particularly limited. From the viewpoint of the applicability of the metal oxide dispersion, the amount of solvent used is, for example, 30 to 99.9% by mass of the entire metal oxide dispersion, preferably 50 to 98% by mass.

[0036] [Surfactants] The metal oxide dispersion according to the present invention may further contain a surfactant (surface modifier) ​​to improve its applicability, defoaming properties, leveling properties, etc. The surfactant may be used alone or in combination of two or more types. Examples of surfactants include silicone-based surfactants, fluorine-based surfactants, and polymer wetting dispersants.

[0037] Examples of silicone-based surfactants include BYK-077, BYK-085, BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-320, BYK-322, BYK-323, BYK-325, BYK-330, BYK-331, BYK-333, BYK-335, BYK-341, BYK-344, BYK-345, BYK-346, BYK-348, BYK-354, BYK-355, BYK-356, BYK-358, BYK-361, BYK-370, BYK-371, BYK-375, BYK-380, and BYK-390 (manufactured by BYK Chemie).

[0038] Fluorine-based surfactants include, specifically, F-114, F-177, F-410, F-411, F-450, F-493, F-494, F-443, F-444, F-445, F-446, F-470, F-471, F-472SF, F-474, F-475, F-477, F-478, F-479, F-480SF, F-482, F-483, F-484, F-486, F-487, F-172D, and MCF-350. Examples include SF, TF-1025SF, TF-1117SF, TF-1026SF, TF-1128, TF-1127, TF-1129, TF-1126, TF-1130, TF-1116SF, TF-1131, TF-1132, TF-1027SF, TF-1441, TF-1442 (manufactured by DIC); and the Polyfox series PF-636, PF-6320, PF-656, PF-6520 (manufactured by Omnova).

[0039] Examples of polymer wetting and dispersing agents include BYK-140, BYK-145, BYK-161, BYK-162, BYK-163, BYK-164, BYK-167, BYK-168, BYK-170, BYK-171, BYK-174, BYK-180, BYK-182, BYK-184, BYK-185, BYK-2050, BYK-2055, BYK-2015, and BYK-9077 (manufactured by BYK Chemie).

[0040] The amount of surfactant used is not particularly limited, but from the standpoint of the applicability, defoaming properties, and leveling properties of the metal oxide dispersion, it is, for example, 0.01 to 2% by mass, preferably 0.05 to 1% by mass, relative to the total amount of components other than the solvent in the metal oxide dispersion.

[0041] [Other ingredients] The metal oxide dispersion according to the present invention may optionally contain additives such as dispersants, thermal polymerization inhibitors, defoamers, silane coupling agents, colorants (pigments, dyes), crosslinking agents, and acid generators. Any of these additives can be conventionally known. Examples of surfactants include anionic, cationic, and nonionic compounds; examples of thermal polymerization inhibitors include hydroquinone and hydroquinone monoethyl ether; and examples of defoamers include silicone and fluorine compounds.

[0042] The method for producing the metal oxide dispersion according to the present invention is not particularly limited, and examples include a method of uniformly mixing the first carboxylic acid, metal oxide nanoparticles surface-treated with a capping agent, a solvent, optionally a surfactant, and optionally other components.

[0043] <Method for manufacturing metal oxide films> Examples of methods for producing a metal oxide film include a production method that includes a coating film formation step of forming a coating film made from the metal oxide dispersion according to the present invention.

[0044] The coating film can be formed, for example, by applying a metal oxide dispersion onto a substrate such as a semiconductor substrate. Coating methods include contact transfer type coating devices such as roll coaters, reverse coaters, and bar coaters, as well as non-contact type coating devices such as spinners (rotary coating devices, spin coaters), dip coaters, spray coaters, slit coaters, and curtain flow coaters.

[0045] The substrate is preferably a metal film, a metal carbide film, a metal oxide film, a metal nitride film, or a metal oxidoxide-nitride film. Examples of metals constituting the substrate include silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, molybdenum, or alloys thereof, but silicon, germanium, and gallium are preferred. The substrate surface may also have an uneven shape, and the uneven shape may be a patterned organic material.

[0046] Next, if necessary, remove volatile components such as solvents and dry the coating film. The drying method is not particularly limited, but for example, drying on a hot plate at a temperature of 80°C to 140°C, preferably 90°C to 130°C, for a time within the range of 60 seconds to 150 seconds is possible. Before heating on the hot plate, vacuum drying (VCD) may be performed at room temperature under reduced pressure. [Examples]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0048] [Preparation of metal oxide dispersions] The preparation of each of the following dispersion stocks was carried out with reference to the description in paragraph

[0223] of Japanese Patent Publication No. 2018-193481.

[0049] Preparation of Z-1 dispersion stock solution Based on paragraph

[0223] of Japanese Patent Publication No. 2018-193481, a slurry of ZrO2 obtained by cooling to room temperature was centrifuged to obtain wet cake A. 0.25 times the weight of wet cake A was added to wet cake A and stirred. After reprecipitation, wet cake B was obtained by centrifugation. Wet cake B was dried under reduced pressure overnight to obtain a powder. Propylene glycol monomethyl ether acetate (hereinafter referred to as "PGMEA") was added to the obtained dried powder to a solid content concentration of 48% by mass to redisperse it, and then filtered to obtain Z-1 dispersion stock solution.

[0050] • Measurement of the size of metal oxide nanoparticles contained in the Z-1 dispersion stock solution The Z-1 dispersion stock solution was used as a sample, and XRD measurements were performed using an X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation). The obtained results were analyzed using the accompanying software PDXL, and the size (crystallite size) of the metal oxide nanoparticles was determined to be 2.5 nm using the Halder-Wagner method.

[0051] Preparation of Z-2 dispersion stock solution Except for changing 2-acryloyloxyethyl phthalic acid to 2-acryloyloxyethyl succinic acid (see formula below), the procedure was the same as described in "Preparation of Z-1 dispersion stock solution" above to obtain Z-2 dispersion stock solution.

[0052] [ka]

[0053] Measurement of the size of metal oxide nanoparticles contained in the Z-2 dispersion stock solution. Except for using the Z-2 dispersion stock solution instead of the Z-1 dispersion stock solution, the procedure was performed in the same manner as described above for "Measurement of the size of metal oxide nanoparticles contained in the Z-1 dispersion stock solution," and the size (crystallite size) of the metal oxide nanoparticles was found to be 2.5 nm.

[0054] Preparation of Z-3 dispersion stock solution Except for replacing 0.25 times the weight of wet cake A with 2-acryloyloxyethyl succinic acid with 0.125 times the weight of wet cake A with 2-acryloyloxyethyl phthalic acid and 0.125 times the weight of wet cake A with 4-(n-hexyloxy)benzoic acid, the procedure was carried out in the same manner as described in "Preparation of Z-1 dispersion stock solution" above to obtain Z-3 dispersion stock solution.

[0055] • Measurement of the size of metal oxide nanoparticles contained in the Z-3 dispersion stock solution Except for using the Z-3 dispersion stock solution instead of the Z-1 dispersion stock solution, the procedure was performed in the same manner as described above for "Measurement of the size of metal oxide nanoparticles contained in the Z-1 dispersion stock solution," and the size (crystallite size) of the metal oxide nanoparticles was found to be 2.5 nm.

[0056] Preparation of carboxylic acid solution 0.40 parts by mass of the carboxylic acid shown in Table 1 and 99.60 parts by mass of PGMEA were mixed to obtain carboxylic acid solutions A to K.

[0057] [Table 1]

[0058] In the proportions shown in Table 2 or 3 (unit: parts by mass), the carboxylic acid solution and the solvent PGMEA were sequentially added to the Z-1 dispersion stock solution, the Z-2 dispersion stock solution, or the Z-3 dispersion stock solution, stirred, and filtered through a Φ0.2 μm membrane filter to obtain a metal oxide dispersion.

[0059] [Percentage of inorganic components] In Table 2 or 3, "Percentage of Inorganic Content" indicates the ratio of the inorganic content to the total amount of inorganic and organic content in the metal oxide dispersion. Specifically, the ratio (mass%) of the inorganic content of the Z-1, Z-2, or Z-3 dispersion to the total amount of solid content of the Z-1, Z-2, or Z-3 dispersion relative to the mass of carboxylic acid in the carboxylic acid solution was calculated.

[0060] [Percentage of free aromatic carboxylic acids] In Table 2 or 3, "Percentage of Free Aromatic Carboxylic Acid" indicates the proportion of aromatic carboxylic acid present in the metal oxide dispersion separately from the metal oxide nanoparticles, relative to the mass of solids in the metal oxide dispersion. Specifically, the ratio (mass%) of the mass of carboxylic acid in the carboxylic acid solution to the total mass of carboxylic acid in the carboxylic acid solution and the mass of solids in the Z-1, Z-2, or Z-3 dispersion was calculated.

[0061] [Stability over time] The metal oxide dispersions, left standing in containers at room temperature for 6 months, were carefully visually inspected and evaluated according to the following criteria. The results are shown in Table 2 or 3. +(Good): No overall turbidity of the dispersion or sedimentation at the bottom of the container was observed. -(Poor): Cloudiness of the entire dispersion, precipitation at the bottom of the container, or both were observed.

[0062] [Solvent shock] To the metal oxide dispersion, 9 times the mass of butyl acetate or 9 times the mass of γ-butyrolactone was added and allowed to stand at room temperature for one week. The dispersion was then carefully inspected visually and evaluated according to the following criteria. The results are shown in Table 2 or 3. +(Good): No overall turbidity of the dispersion or sedimentation at the bottom of the container was observed. -(Poor): Cloudiness of the entire dispersion, precipitation at the bottom of the container, or both were observed.

[0063] [Table 2]

[0064] [Table 3]

[0065] As can be seen from Tables 2 and 3, the metal oxide dispersions in the examples exhibited excellent temporal stability and suppressed the occurrence of solvent shock, while the metal oxide dispersions in the comparative examples were found to be inferior in temporal stability, the effect of suppressing solvent shock, or both.

Claims

1. A first carboxylic acid is at least one aromatic carboxylic acid selected from the group consisting of aromatic carboxylic acids having an aromatic ring substituted with an alkyl group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxy group, aromatic carboxylic acids having an aromatic ring substituted with an alkoxycarbonyl group, and aromatic carboxylic acids having an aromatic ring substituted with an acyloxy group, Metal oxide nanoparticles surface-treated with a capping agent, Solvents and, A metal oxide dispersion containing, The capping agent comprises a second carboxylic acid having an ester bond and a polymerizable double bond, The second carboxylic acid is different from the first carboxylic acid. Metal oxide dispersion.

2. The metal oxide dispersion according to claim 1, wherein the first carboxylic acid is present in the metal oxide dispersion separately from the metal oxide nanoparticles and / or in the capping agent.

3. The metal oxide dispersion according to claim 1 or 2, wherein the second carboxylic acid has an aromatic ring.

4. The metal oxide dispersion according to claim 1 or 2, wherein the ratio of the mass of the first carboxylic acid present in the metal oxide dispersion separately from the metal oxide nanoparticles to the mass of the solid content of the metal oxide dispersion is 10% by mass or less.

5. The metal oxide dispersion according to claim 1 or 2, wherein the ratio of the inorganic component to the total of the inorganic and organic components in the solid content of the metal oxide dispersion is 25% by mass or more.

6. The metal oxide dispersion according to claim 1 or 2, wherein the metal contained in the metal oxide nanoparticles is at least one selected from the group consisting of zinc, yttrium, hafnium, zirconium, lanthanum, cerium, neodymium, gadolinium, holmium, lutetium, tantalum, titanium, silicon, aluminum, antimony, tin, indium, tungsten, copper, vanadium, chromium, niobium, molybdenum, ruthenium, rhodium, rhenium, iridium, germanium, gallium, thallium, and magnesium.

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