JP2023097934A - Coated titanium dioxide fine particles and method of producing the same, and organic solvent dispersion including the same, coating composition, and coating film - Google Patents

Abstract

To provide coated titanium dioxide fine particles capable of improving the dispersibility of titanium dioxide fine particles in an organic solvent, thereby sufficiently exhibiting the functions and performance of the titanium dioxide fine particles, and a method of producing the same, also to provide an organic solvent dispersion and coating film with excellent transparency and refractivity.SOLUTION: The surface of titanium dioxide fine particles containing a tin component is coated with a reaction product of an alkoxysilane compound having an amino group such as aminopropyltrimethoxysilane and/or a hydrolysis product thereof and a compound having one α,β-unsaturated carbonyl group in the molecule such as alkoxypolyalkylene glycol (meth)acrylate.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to coated titanium dioxide fine particles, a method for producing the same, an organic solvent dispersion containing the same, a coating composition, and a coating film.

Titanium dioxide fine particles are materials having excellent properties such as visible light transmission, ultraviolet shielding, and high refractive index. In order to use its properties, usually, titanium dioxide fine particles are dispersed in an organic solvent to prepare an organic solvent dispersion or a coating composition, which is applied or sprayed onto a substrate to obtain a coating containing titanium dioxide fine particles. form a film.

For example, the surface of a synthetic resin lens or film is provided with a hard coat or ultraviolet shielding coating having high visible light transmittance (transparency) and a high refractive index. is used. In addition, the display surface of flat panel displays such as liquid crystal displays, plasma displays, and electroluminescence displays is provided with an antireflection film for the purpose of preventing reflection of the light source or face. Titanium dioxide fine particles are also used for the layer.

Titanium dioxide fine particles tend to aggregate when dispersed in an organic solvent, and if the aggregated titanium dioxide fine particles are contained when the coating film is formed, the visible light transmittance and the like decrease. Therefore, organic solvent dispersions and coating compositions in which titanium dioxide fine particles are highly dispersed have been investigated.

For example, Patent Document 1 describes coating the surface of titanium dioxide fine particles with a product obtained by reacting aminosilane with an acrylate compound. It is described that by doing so, the dispersibility of the titanium dioxide fine particles in the organic solvent is good, and an organic solvent dispersion and a coating composition having excellent transparency can be obtained.

WO2021/182378

According to the coated titanium dioxide fine particles described in Patent Document 1, a coating film having a high refractive index and improved visible light transmittance (transparency) can be formed. However, today, as the use of high refractive index coating films is expanding, higher transparency is required.

The present inventors have made intensive studies to improve the transparency of a coating film containing fine titanium dioxide particles, and found that it is effective to use titanium dioxide fine particles containing a tin component as coated titanium dioxide fine particles. When the surface of titanium dioxide fine particles is coated with a reactant obtained by reacting an alkoxysilane compound having an amino group with a compound having one α,β-unsaturated carbonyl group in the molecule, a highly transparent organic The inventors have found that a solvent dispersion can be obtained, and that a coating film can also be obtained with high transparency, and have completed the present invention.

That is, the present invention
(1) A reaction product of an alkoxysilane compound having an amino group and/or a hydrolysis product thereof and a compound having one α,β-unsaturated carbonyl group in the molecule is prepared as titanium dioxide fine particles containing a tin component. Coated titanium dioxide fine particles coated on the surface of
(2) The coated titanium dioxide fine particles according to (1), wherein the titanium dioxide fine particles further contain an aluminum component;
(3) The content of the tin component is 0.5% by mass or more and 10% by mass or less in terms of oxide [SnO ₂ /TiO ₂ ] with respect to the titanium dioxide of the titanium dioxide fine particles, or The coated titanium dioxide fine particles according to (2),
(4) The total content of the tin component and the aluminum component is 1% by mass in terms of oxide [(SnO ₂ +Al ₂ O ₃ )/TiO ₂ ] with respect to the titanium dioxide of the titanium dioxide fine particles. The coated titanium dioxide fine particles according to any one of (1) to (3), which are 15% by mass or less,
(5) An organic solvent dispersion of coated titanium dioxide fine particles, comprising the coated titanium dioxide fine particles according to any one of (1) to (4) and an organic solvent;
(6) A coating composition comprising an organic solvent dispersion of the coated titanium dioxide fine particles according to any one of (1) to (4) or the coated titanium dioxide fine particles according to (5), and a binder resin.
(7) a coating film containing the coated titanium dioxide fine particles according to any one of (1) to (4) and a binder resin;
(8) Titanium dioxide fine particles containing a tin component, an alkoxysilane compound having an amino group and/or a hydrolysis product thereof, and a compound having one α,β-unsaturated carbonyl group in the molecule are mixed in a solvent. to mix the reaction product of the alkoxysilane compound having an amino group and/or its hydrolysis product and the compound having one α,β-unsaturated carbonyl group in the molecule with the titanium dioxide A method for producing coated titanium dioxide microparticles, which coats the surface of microparticles,
(9) The fine titanium dioxide particles containing the tin component are obtained by hydrolyzing a mixture of (oxy)titanium chloride and tin chloride, or by hydrolyzing tin chloride in the presence of (oxy) ) The method for producing coated titanium dioxide fine particles according to (8), wherein titanium chloride is hydrolyzed, and then the hydrolyzed product is calcined at a temperature of 250° C. or higher and 1000° C. or lower.
(10) Titanium dioxide fine particles containing a tin component and an aluminum component are obtained by firing the hydrolyzed product described in (9) above at a temperature of 250° C. or higher and 1000° C. or lower in the presence of an aluminum compound. 8), and the method for producing coated titanium dioxide fine particles.

According to the present invention, titanium dioxide fine particles can be dispersed in an organic solvent to a higher degree, and a highly transparent dispersion can be obtained. By using this organic solvent dispersion, a coating film having high visible light transmittance (transparency) and a high refractive index can be formed.

4 is an electron micrograph of titanium dioxide fine particles of Production Example 2. FIG. 4 is an X-ray diffraction spectrum of titanium dioxide fine particles of Production Example 3. FIG.

The present invention provides a reaction product of an alkoxysilane compound having an amino group and/or a hydrolysis product thereof and a compound having one α,β-unsaturated carbonyl group in the molecule, and titanium dioxide containing a tin component. It is coated titanium dioxide microparticles coated on the surface of microparticles.

The average primary particle size of the titanium dioxide fine particles is preferably 3 nm or more and 200 nm or less, more preferably 5 nm or more and 100 nm or less, and even more preferably 10 nm or more and 100 nm or less. Titanium dioxide fine particles having such an average primary particle size are titanium dioxide particles having a larger average primary particle size (for example, titanium dioxide particles having an average primary particle size of about 0.2 to 0.5 μm used for pigment applications). Visible light transmittance is higher than that of Therefore, by using titanium dioxide fine particles having the above average primary particle size, an organic solvent dispersion having a higher transmittance can be produced. The average primary particle size of titanium dioxide fine particles is calculated by measuring the particle size of 200 randomly selected particles under an electron microscope and calculating the average value of the particle sizes (this is also referred to as "electron micrograph method" in the present application. ).

The specific surface area of the titanium dioxide fine particles is preferably 15 m ² /g or more, more preferably 50 m ² /g or more, and even more preferably 100 m ² /g or more. On the other hand, the specific surface area of the titanium dioxide fine particles is preferably 300 m ² /g or less, more preferably 200 m ² /g or less. The specific surface area of the titanium dioxide fine particles can be determined by the nitrogen adsorption method (BET method) using an automatic fluidized specific surface area measuring device (FlowSorb II 2300, manufactured by Shimadzu Corporation). By using titanium dioxide fine particles having such a specific surface area, an organic solvent dispersion having higher visible light transmittance (transparency) can be produced.

The shape of the titanium dioxide fine particles is not particularly limited, and any shape such as spherical, rod-like, needle-like, spindle-like, and plate-like can be used. Regarding the above average primary particle size in the case of shapes other than spherical, in the case of rod-like, needle-like, and spindle-like particles, it is defined by the average length of the short axis side, and in the case of plate-like particles, the average of the diagonal length of the surface. stipulated in

The crystal structure of the titanium dioxide fine particles is also not particularly limited, and an anatase type, rutile type, brookite type, or the like can be used. However, the rutile type has lower photocatalytic activity and a higher refractive index than the anatase type. It is preferable to use titanium microparticles. If a tin component is included during the production of titanium dioxide fine particles, preferable rutile-type titanium dioxide is likely to be produced. Titanium dioxide fine particles may be composed of compounds represented by metatitanic acid ( _TiO2.nH2O ) and orthotitanic acid (Ti(OH) ₄ ) in addition _to titanium dioxide ( _TiO2 ).

The titanium dioxide fine particles of the present invention contain a tin component, which is preferably contained inside the titanium dioxide fine particles, and more preferably dissolved in the titanium dioxide crystals. "Solid solution" is a phase in which an atom at a lattice point of one crystal phase is replaced with another atom or another atom enters the lattice gap, that is, another substance is dissolved in a crystal phase It is a state having a mixed phase which is considered to be a homogeneous phase as a crystalline phase. A substance in which a solute atom is substituted for a solvent atom at a lattice point is called a substitution type, and a substance in which a solute atom enters the interstitial space is called an erosion type. "Solid solution" as used herein refers to any of these states. When the solid solution state is substitution type, the titanium sites in the crystal lattice of the titanium dioxide fine particles are substituted with tin atoms. When the solid solution state is the interstitial type, the tin atoms enter the lattice gaps of the crystals of the titanium dioxide fine particles.

When the tin component is solid-solved in the titanium dioxide fine particles, the tin component is detected by elemental analysis (fluorescence X-ray analysis, X-ray photoelectron spectroscopy, etc.), but when the crystal phase is measured by X-ray diffraction, it is not oxidized. Only peaks of the crystal phase of titanium are detected, and peaks of compounds derived from tin atoms are not detected. In other words, when the crystal phase is measured by X-ray diffraction or the like and no peak of the tin atom-derived compound is detected, it can be determined that the tin component is dissolved in the titanium dioxide particles.

When titanium dioxide fine particles containing a tin component are used, the organic solvent dispersion, the coating composition, and the coating film formed using these are more effective than when titanium dioxide fine particles not containing a tin component are used. Visible light transmittance (transparency) can be improved. The reason for this is not clear, but by adding a tin component to the titanium dioxide fine particles, the amount of coarse particles and particles with a large aspect ratio is reduced, and the effect of improving the particle size distribution contributes to the improvement of the dispersibility of the fine particles. and is presumed to improve transparency.

The content of the tin component in the titanium dioxide fine particles is preferably 0.5% by mass or more and 10% by mass or less in terms of oxide (SnO ₂ /TiO ₂ ) with respect to the titanium dioxide of the titanium dioxide fine particles, and 1 mass%. % or more and 5 mass % or less. If the content of the tin component is 0.5% by mass or more, the above effect (improved visible light transmittance) can be sufficiently ensured. On the other hand, even if the tin component exceeds 10% by mass, the above-mentioned range is preferable because further improvement of the above effects cannot be expected.

The method for incorporating the tin component into the titanium dioxide particles is not particularly limited, but gas phase methods (CVD methods, PVD methods, etc.), liquid phase methods (hydrothermal methods, sol-gel methods, coprecipitation methods, etc.), solid phase methods, etc. (high-temperature firing method) can be used, and the above liquid phase method and solid phase method can be used to form a solid solution.

As a method for incorporating a tin component into titanium dioxide particles, a mixture of tin chloride and (oxy)titanium chloride may be hydrolyzed, or (oxy)chloride may be added in the presence of core particles obtained by hydrolyzing tin chloride. Titanium chloride may be hydrolyzed. Titanium tetrachloride, titanium trichloride, titanium oxychloride and the like can be used as (oxy)titanium chloride. Among them, titanium tetrachloride is preferred. (Oxy)titanium chloride means titanium chloride and/or titanium oxychloride.

To hydrolyze a mixture of tin chloride and (oxy)titanium chloride, the mixture is preferably hydrolyzed at a temperature of 40°C or higher and 110°C or lower, more preferably 60°C or higher and 110°C or lower, and 80°C. It is more preferable to carry out at a temperature of 110° C. or more. In this way, the tin component and the titanium component hydrolyze and co-precipitate at the same time. The hydrolysis time can be appropriately set.

When (oxy)titanium chloride is hydrolyzed in the presence of core particles, the core particles may be commercially available or may be synthesized by oneself. For example, by preparing a hydrochloric acid aqueous solution of tin chloride (for example, SnCl ₄ ) and heating it at a temperature of 40° C. or higher and 80° C. or lower, it is possible to obtain fine particles of a tin compound that serve as core particles. Next, hydrolysis of titanium (oxy)chloride in the presence of the core particles is preferably carried out at a temperature of 40°C or higher and 110°C or lower, more preferably 60°C or higher and 110°C or lower, and 80°C. It is more preferable to carry out at a temperature of 110° C. or more. By doing so, the (oxy)titanium chloride can be sufficiently hydrolyzed with the fine particles of the tin compound as nuclei. The hydrolysis time can be appropriately set.

After filtering, washing, and drying the above hydrolyzed product as necessary, it is fired at a temperature of 250° C. or more and 1000° C. or less, whereby fine particles can be reduced and titanium dioxide fine particles with good crystallinity can be obtained. Therefore, it is preferable. The baking time can be appropriately set. When the fine particles are reduced and the crystallinity is improved by firing, the effect of improving the refractive index of the coating film containing the titanium dioxide fine particles can be expected. This is for the following reasons.

When dispersing titanium dioxide fine particles in an organic solvent or paint, it is common to use a dispersant. Generally, more dispersant is required to disperse smaller particles. On the other hand, if the amount of the dispersant added is too large, the amount of the dispersant finally contained in the coating film also increases, which lowers the refractive index of the coating film. In this respect, as described above, if the product after hydrolysis of titanium (oxy)chloride is calcined, some fine particles that have not grown sufficiently due to hydrolysis can be reduced to a certain size. Since the titanium dioxide fine particles can be dispersed in an organic solvent dispersion or paint with a smaller amount of dispersant, it is possible to improve the refractive index of the coating film.

In addition to the tin component, the titanium dioxide fine particles of the present invention may contain an aluminum component, preferably contained inside the titanium dioxide fine particles, and preferably dissolved in the titanium dioxide crystals. more preferred. The solid-solution state of the aluminum component in the titanium dioxide fine particles and the method for confirming the solid-solution state are the same as in the case of the tin component described above. By containing an aluminum component, the photocatalytic activity of the titanium dioxide particles can be further suppressed. As a result, the coating film formed using this organic solvent dispersion can have higher light resistance.

The content of the aluminum component in the titanium dioxide fine particles is preferably 0.5% by mass or more and 10% by mass or less, and 1% by mass or more and 8% by mass or less in terms of Al ₂ O ₃ with respect to the titanium dioxide of the titanium dioxide fine particles. is more preferable.

The content of the tin component and the aluminum component in the titanium dioxide fine particles is 1% by mass or more and 15% by mass or less in terms of oxide ((SnO ₂ +Al ₂ O ₃ )/TiO ₂ ) with respect to the titanium dioxide of the titanium dioxide fine particles. It is preferably 1% by mass or more and 10% by mass or less. When the contents of the tin component and the aluminum component are 1% by mass or more, the above effects (reduction of coarse particles due to the tin component, light resistance due to the aluminum component, etc.) can be sufficiently ensured. On the other hand, when the content of these components exceeds 15% by mass, the content ratio of the titanium oxide component becomes relatively small, and as a result, there is concern that the refractive index of the coating film may decrease. The above ranges are preferred.

The method for adding the aluminum component to the titanium dioxide particles is not particularly limited, and any known method can be used. For example, hydrolysis of a mixture of titanium (oxy)chloride and tin chloride, or a product obtained by hydrolysis of titanium (oxy)chloride in the presence of core particles obtained by hydrolysis of tin chloride (hydrolysis (subsequent product) may also employ methods of treating aluminum compounds.

More specifically, aluminum hydroxide is deposited on the surface of the hydrolyzed product by adding an aluminum compound to an aqueous solution containing the hydrolyzed product and neutralizing it with an acid or alkali. be able to. Furthermore, by firing this at a temperature of 250° C. or higher and 1000° C. or lower, it is possible to obtain titanium dioxide fine particles containing (solid solution) the tin component and the aluminum component. The baking time can be appropriately set.

In addition to the tin component and the aluminum component, the titanium dioxide fine particles of the present invention may contain a third component in solid solution for the purpose of improving light resistance and controlling the particle shape during firing. Specific examples of the third component include Zn, Co and Nb.

The content of these third components is 1 mass in terms of oxide ((SnO ₂ +Al ₂ O ₃ +third component oxide)/TiO ₂ ) with respect to the amount of titanium dioxide contained in the titanium dioxide fine particles. % or more and 15 mass % or less, and more preferably 1 mass % or more and 10 mass % or less. With such a content, the above effects (improvement of visible light transmittance due to the tin component, light resistance due to the aluminum component and the third component, etc.) are sufficiently ensured, and the decrease in the refractive index of the coating film is prevented. can be suppressed.

The reactant coated on the surface of the titanium dioxide fine particles containing the tin component has an alkoxysilane compound having an amino group and/or its hydrolysis product and one α,β-unsaturated carbonyl group in the molecule. Obtained by reaction with compounds. Such a reaction is called a Michael addition reaction, and a mono α, β-unsaturated carbonyl compound having one C=C bond in the molecule (i.e., one α, β-unsaturated carbonyl group in the molecule). compound) is added with a compound having an amino group. For this reason, the reaction product is sometimes called a Michael adduct. The reactant is understood to be a compound in which an alkoxysilane compound and/or its hydrolysis product is added via an amino group to a compound having one α,β-unsaturated carbonyl group in the molecule.

The above-mentioned Michael addition reaction is a reaction in which, of the amino groups (NH ₂ ) possessed by the alkoxysilane compound and/or its hydrolysis product, the hydrogen of the amino group does not remain, that is, the two hydrogen atoms of the amino group are α,β- It may be a reaction in which 2 mol of a compound having an unsaturated carbonyl group does not leave hydrogen in the amino group, but a reaction in which hydrogen (NH) in the amino group remains, that is, one hydrogen in the amino group is α, β-unsaturated. A reaction in which 1 mol of a compound having a carbonyl group is added to leave 1 hydrogen of the amino group is preferred. Therefore, if the amino group of the alkoxysilane compound having an amino group and/or its hydrolysis product is a mol, and the compound having one α,β-unsaturated carbonyl group in the molecule is b mol, then 0.8 Reaction at a molar ratio such that ≦a/b≦10 is preferred, 1≦a/b≦10 is more preferred, 1≦a/b≦8 is even more preferred, and 1≦a/b≦6 is most preferred. .

Specific examples of the alkoxysilane compound having an amino group include a silanol compound of —C—Si(OH) ₃ , an alkoxysilane compound of —C—Si(OR) _{3 ,} and —C—Si(OR) _x R _{′ 3-} . An alkylalkoxysilane compound for _x (x is an integer of 1 to 3 (that is, 1 to 3)) and the like, and more preferably those containing a hydrolyzable group such as an alkoxy group represented by the following general formula (1) .
General formula (1):

In the general formula (1), x represents an integer of 1 to 3 (that is, 1 to 3), y represents an integer of 0 to 2 (that is, 0 to 2), and z represents 0 to 1 ( That is, it represents an integer of 0 or 1). However, x+y+z=3. R ¹ , R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (that is, 1 to 4).

Specific examples of the alkoxysilane compound having an amino group include amino group-containing alkoxysilanes and amino group-containing di(alkoxysilanes), and the former includes 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. Silane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltri Ethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-(trimethoxysilylpropyl)aminopropyltrimethoxysilane Silane, 3-(triethoxysilylpropyl)aminopropyltriethoxysilane, 2-(trimethoxysilylpropyl)aminoethyl-3-aminopropyltrimethoxysilane, 2-(triethoxysilylpropyl)aminoethyl-3-aminopropyl Examples include triethoxysilane. Examples of the latter include bis(trimethoxysilylpropyl)amine and the like, and their hydrolysis products can be prepared and used.

The compound having one α,β-unsaturated carbonyl group in the molecule is not particularly limited as long as it is a mono α,β-unsaturated carbonyl compound having one C=C bond in the molecule, and the following general Those having a skeleton represented by formula (2) are preferred. Further, the compound having one α,β-unsaturated carbonyl group in the molecule is more preferably a compound further having an ether bond in the molecule, and the compound having an ether bond has a polymerization number n = 2 to 10. (i.e., 2 to 10) ethylene glycol chain, a propylene glycol chain having a polymerization number n = 2 to 10 (i.e., 2 to 10) or a 5- to 6-membered cyclic group (i.e., a 5- or 6-membered cyclic group) more preferred are compounds having a 5- to 6-membered cyclic group, and more preferred are (meth)acrylates or alkoxypolyalkylene glycol (meth)acrylates having a 5- to 6-membered cyclic group. The expression "(meth)acrylate" means acrylate and/or methacrylate (sometimes referred to as methacrylate).
General formula (2):

In general formula (2) above, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms (ie, 1 to 4).

Specific examples of compounds having one α,β-unsaturated carbonyl group in the molecule include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n - alkyl (meth)acrylates such as butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate; Cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol ( (meth)acrylates having a 5- to 6-membered cyclic group such as meth)acrylate; methoxydiethylene glycol (meth)acrylate, methoxytriethyleneglycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxydipropylene glycol (meth) Alkoxypolyalkylene glycol (meth)acrylates such as acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy Hydroxyl group-containing (meth)acrylates such as butyl (meth)acrylate, glycerol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate; (meth)acrylamide, N,N-dimethyl (meth)acrylamide , N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, diacetone (meth)acrylamide, N-substituted (meth)acrylamides such as acryloylmorpholine; N,N-dimethylaminoethyl (meth)acrylate , N,N-diethylaminoethyl (meth)acrylates and other amino group-containing (meth)acrylates; Further, in addition to the above compounds, polyester (meth)acrylate, polyurethane (meth)acrylate, epoxy (meth)acrylate, (meth)acrylated maleic acid-modified polybutadiene, and the like can be used. Among these, (meth)acrylates or alkoxypolyalkylene glycol (meth)acrylates having a 5- to 6-membered cyclic group are preferred, such as tetrahydrofurfuryl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and methoxypolyethylene glycol. (Meth)acrylates or methoxydipropylene glycol (meth)acrylates are more preferred, and among the more preferred acrylates, tetrahydrofurfuryl acrylate (hereinafter sometimes referred to as "THF-A"), methoxytriethylene glycol acrylate (hereinafter sometimes referred to as "methoxy-triethylene glycol acrylate" or "MTG-A"), methoxypolyethylene glycol acrylate (hereinafter sometimes referred to as "130A") or methoxydipropylene glycol acrylate ( Hereinafter, it may be described as "methoxydipropylene glycol acrylate" or "DPM-A") is most preferred.

Examples of the Michael adduct include compounds having a chemical structural formula of the following general formula (3).
General formula (3):

wherein R ¹ , R ² , R ³ , R ⁴ , x, y and z are as defined above, p is 1 or 2 and q is 0 or 1. However, p+q=2. R ⁵ is an ethylene oxide polymerized portion ((CH ₂ CH ₂ O) _n CH ₃ ) or a propylene oxide polymerized portion (CHCH ₃ CH ₂ O) _n CH ₃ ), where n is 2 or more and 10 or less.

Specific examples of the general formula (3) include, but are not limited to, the following compounds.

Here, the Michael adduct may contain the following compounds in which the silanol groups of different Michael adducts are condensed or polycondensed.

The reactant (Michael adduct) adsorbs, precipitates, or reacts on the surface of the titanium dioxide fine particles, and the reactant or a part of the reactant is deformed (for example, an alkoxy group is decomposed and separated into alcohol and hydroxyl group, and is present on the surface of the titanium dioxide fine particles containing the tin component in a state (-Si-OH) adsorbed on the fine particles by the hydroxyl group, or in a state in which the reaction product undergoes dehydration condensation. exist). The reactant (Michael adduct) is preferably a low-molecular-weight alkoxysilane compound having 3 to 100 carbon atoms (ie, 3 to 100 or less) and/or a hydrolysis product thereof, and preferably has 3 to 50 carbon atoms (ie, 3 or more 50 or less), more preferably 3 to 40 carbon atoms (that is, 3 or more and 40 or less).

The coating of the reactant (Michael adduct) may be present on at least a part of the surface of the fine titanium dioxide particles containing the tin component. It is preferable to coat as densely as possible in order to disperse it in the liquid. The coating amount is preferably 0.1 to 50 parts by mass (that is, 0.1 to 50 parts by mass), and 0.5 to 40 parts by mass (that is, 0.5 parts by mass) with respect to 100 parts by mass of titanium dioxide fine particles. 5 parts by mass or more and 40 parts by mass or less), more preferably 1 to 30 parts by mass (that is, 1 part by mass or more and 30 parts by mass or less).

Next, a dispersion in which the coated titanium dioxide fine particles are dispersed in an organic solvent will be described. In the present application, a dispersion obtained by dispersing the coated titanium dioxide fine particles in an organic solvent is referred to as an organic solvent dispersion, and the organic solvent can be appropriately selected. Specifically, toluene, xylene, solvent naphtha, normal hexane. , isohexane, cyclohexane, methylcyclohexane, normal heptane, tridecane, tetradecane, pentadecane, and other hydrocarbon solvents; methanol, EtOH (ethanol), butanol, IPA (isopropyl alcohol), normal propyl alcohol, 2-butanol, TBA (tertiary butanol), butanediol, ethylhexanol, benzyl alcohol and other alcohol solvents; acetone, MEK (methyl ethyl ketone), methyl isobutyl ketone, DIBK (diisobutyl ketone), cyclohexanone, DAA (diacetone alcohol) and other ketone solvents; ethyl acetate , butyl acetate, methoxybutyl acetate, cellosolve acetate, amyl acetate, n-propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate, γ-butyl lactone and other ester solvents; methyl cellosolve, cellosolve, butyl cellosolve, dioxane, MTBE (methyl tertiary butyl ether), ether solvents such as butyl carbitol; ethylene glycol, diethylene glycol, triethylene glycol, glycol solvents such as propylene glycol; diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, PGME (1-methoxy- 2-propanol, ie, propylene glycol monomethyl ether), glycol ether solvents such as 3-methoxy-3-methyl-1-butanol; ethylene glycol monomethyl ether acetate, PGMEA (propylene glycol monomethyl ether acetate), diethylene glycol monobutyl ether acetate, diethylene glycol Glycol ester solvents such as monoethyl ether acetate; DMF (N,N-dimethylformamide), DEF (N,N-diethylformamide), DMAc (N,N-dimethylacetamide), NMP (N-methylpyrrolidone) At least one selected from amide solvents; and the like can be used. Among these solvents, it is preferable to use an alcohol solvent or a glycol ether solvent. ether) is more preferably used. The content of the coated titanium dioxide fine particles is preferably 0.1 to 95 parts by mass (that is, 0.1 to 95 parts by mass) relative to 100 parts by mass of the organic solvent, and 10 to 90 parts by mass ( That is, 10 parts by mass or more and 90 parts by mass or less) is more preferable, and 15 to 90 parts by mass (that is, 15 parts by mass or more and 90 parts by mass or less) is more preferable.

Next, a coating composition containing the above coated titanium dioxide fine particles, an organic solvent and a binder resin, or a coating composition containing the above organic solvent dispersion and a binder resin will be described. As the organic solvent, those mentioned above can be used. Any resin can be used as the binder resin, and for example, a dissolution type in a low-polarity non-aqueous solvent, an emulsion type, a colloidal dispersion type, or the like can be used without limitation. Various modified polyester resins such as polyester resins, urethane-modified polyester resins, epoxy-modified polyester resins, acrylic-modified polyester resins, polyether urethane resins, polycarbonate urethane resins, vinyl chloride-vinyl acetate copolymers, and epoxy resins. , modified celluloses such as phenol resin, acrylic resin, polyamideimide, polyimide, ethyl cellulose, hydroxyethyl cellulose, nitrocellulose, cellulose-acetate-butyrate (CAB), cellulose-acetate-propionate (CAP); polyethylene glycol; polyethylene oxide, etc. mentioned. The amount of the resin compounded is preferably about 0.5 to 100 parts by weight, more preferably about 1 to 50 parts by weight, and about 2 to 25 parts by weight based on 100 parts by weight of the coated titanium dioxide fine particles. More preferred.

Specific examples of the binder resin include, for example, Aronix (registered trademark) series B-309, B-310, M-430, M-406, M-460, M-1100 (manufactured by Toagosei Co., Ltd.); light acrylate (registered Trademark) series MTG-A, DPM-A, THF-A, IB-XA, HOA-HH (N), 1,6HX-A, 1,9ND-A, PE-3A, PE-4A (Kyoeisha Chemical Co., Ltd. ); Epolite (trade name) series 40E, 4000, 3002 (N) (manufactured by Kyoeisha Chemical Co., Ltd.); NK Ester (registered trademark) series A-TMM-3, A-9550, A-DPH (Shin Nakamura Chemical KAYARAD (registered trademark) series DPHA, DPEA-12, DPCA-60 (manufactured by Nippon Kayaku Co., Ltd.).

The organic solvent dispersion or coating composition described above can be applied or sprayed onto a substrate to form a layer of titanium dioxide particulates and optionally cured. A coating film having high visible light transmittance (transparency) can be formed, and can be used as a hard coat, a high refractive index layer, and an ultraviolet shielding layer. The base material is not particularly limited, and glass, plastic, ceramic, metal, etc. can be used. The film thickness and the like can be appropriately set.

The coated titanium dioxide microparticles are prepared in the presence of the tin component-containing titanium dioxide microparticles, preferably in the presence of an organic solvent containing the tin component-containing titanium dioxide microparticles, in the presence of a pre-prepared Michael adduct (alkoxysilane having an amino group). compound and/or its hydrolysis product with a compound having one α,β-unsaturated carbonyl group in the molecule), and the reaction product (Michael adduct) containing a tin component can be coated on the surface of the fine titanium dioxide particles. This mixing can be done by simply mixing and stirring at room temperature, but coating proceeds faster with the application of heat. It is preferable to carry out the treatment at a temperature in the range of room temperature to 150° C. for 10 minutes to 20 hours. Mixing while dispersing is preferable because the coating progresses further. A well-known dispersing machine can be used when carrying out while dispersing. Specific examples include sand mills, homogenizers, ball mills, paint shakers, and ultrasonic dispersers. Coating also proceeds by hydrolyzing the alkoxy groups of the reactants, but this hydrolysis reaction requires a certain amount of water, and the amount of water is 0.5 to 1.0 to the hydrolyzable groups of the alkoxysilane. Add 5 equivalents (ie, 0.5 to 1.5 equivalents). Moreover, in order to accelerate the hydrolysis reaction, an acid or an alkali may be added as a catalyst. In this manner, coated titanium dioxide fine particles can be produced, and a dispersion in which the coated titanium dioxide fine particles are dispersed in an organic solvent can also be produced.

As another method, titanium dioxide fine particles containing tin, an alkoxysilane compound having an amino group and/or its hydrolysis product, and a compound having one α,β-unsaturated carbonyl group in the molecule. in a solvent to obtain coated titanium dioxide fine particles. An organic solvent or an aqueous solvent can be used as the solvent. Mixing in this method can be performed by simply mixing and stirring at room temperature as described above, but the reaction proceeds more quickly when heat is applied. It is preferable to carry out the treatment at a temperature in the range of room temperature to 150° C. for 10 minutes to 20 hours. Mixing while dispersing is preferable because the coating progresses further. A well-known dispersing machine can be used when carrying out while dispersing. Specific examples include sand mills, homogenizers, ball mills, paint shakers, and ultrasonic dispersers. Coating also proceeds by hydrolyzing the alkoxy groups of the reactants, but this hydrolysis reaction requires a certain amount of water, and the amount of water is 0.5 to 1.0 to the hydrolyzable groups of the alkoxysilane. Add 5 equivalents (ie, 0.5 to 1.5 equivalents). Moreover, in order to accelerate the hydrolysis reaction, an acid or an alkali may be added as a catalyst. In this manner, coated titanium dioxide fine particles can be produced, and a dispersion in which the coated titanium dioxide fine particles are dispersed in an organic solvent can also be produced.

Alternatively, the coating composition can be produced by mixing the coated titanium dioxide fine particles with the organic solvent and the binder resin, or by mixing the organic solvent dispersion with the binder resin. Alternatively, a solvent-free coating composition can be produced by mixing coated titanium dioxide fine particles with a binder resin, or by removing the organic solvent after producing the coating composition containing the organic solvent. . In the mixing step, for example, it is preferable to use the above-described dissolver or high-speed stirrer. Since the organic solvent dispersion of the present invention has high visible light transmittance, a highly transparent coating film can be formed by using a coating agent composition using this organic solvent dispersion.

The binder resin used in the coating composition is not particularly limited as long as the stability, high refractive index, and visible light transmittance (transparency) of the coating film obtained from the coating composition are ensured. Examples of binder resins that can be used include alkyd resins, acrylic resins, melamine resins, urethane resins, epoxy resins, silicone resins, and the like. Also usable are polyester resins, polyamic acid resins, polyimide resins, styrene maleic acid resins, styrene maleic anhydride resins, and the like. Furthermore, various acrylic acid-based monomers and acrylate-based monomers are also applicable. Resins and monomers particularly preferred as the binder resin include urethane resins, acrylic resins, acrylic acid monomers, polyamic acid resins, polyimide resins, styrene maleic acid resins, and styrene maleic anhydride resins. Binder resin may be used individually by 1 type, and may be used in combination of 2 or more types.

Furthermore, the coating composition may contain various additives in addition to the binder resin. Specifically, dispersants, pigments, fillers, aggregates, thickeners, flow control agents, leveling agents, curing agents, cross-linking agents, curing catalysts and the like can be blended.

A coating film can be formed on a substrate by applying the organic solvent dispersion or the coating composition of the present invention to a substrate, and drying and/or baking as necessary. The base material is not particularly limited, and various materials such as glass, polymer, ceramic, and metal can be used. The coating method is not particularly limited, and known methods can be used. Examples thereof include a method of coating with a spin coater, dip coater, die coater, slit coater, bar coater, gravure coater, LB (Langmuir-Blodgett) film method, self-assembly method, spray coating and the like.

There are no particular restrictions on the drying method and the baking method, and known methods can be used. For example, heat drying under normal pressure or reduced pressure, natural drying, and the like can be mentioned. The heating method for heat drying and baking is not particularly limited, and examples thereof include a method of heating using an apparatus such as a hot plate or an oven. The drying temperature is preferably about 80 to 150°C, and the firing temperature is preferably about 150 to 400°C.

The thickness of the coating film can be appropriately set depending on the application. ) is more preferred. The visible light transmittance of the coating film can be measured as haze with a haze meter, and although it is also affected by the film thickness, the haze is preferably 5% or less, more preferably 2.5% or less, and 1.5%. More preferred are: Moreover, the refractive index of the coating film is preferably 1.60 or more, more preferably 1.80 or more, in order to use the film as a high refractive index layer. The refractive index can be measured and calculated by ellipsometry.

The coating film formed on the substrate may be laminated in multiple layers. In the case of lamination of multiple layers, each layer may be the same coating film, or a combination of different coating films. By alternately laminating the high refractive index layer and the low refractive index layer on the substrate, an antireflection film can be formed on the substrate. The antireflection film may have any structure as long as it includes the high refractive index layer. For example, an antireflection film having a high refractive index layer and a low refractive index layer in this order on a substrate, Alternatively, it may be an antireflection film having a low refractive index layer, a high refractive index layer, and a low refractive index layer in this order on a substrate. In such a layer structure, a desired antireflection film can be designed by adjusting the film thickness and refractive index of each layer.

Examples and comparative examples are shown below, but the present invention is not limited to these examples.

[Production Example 1]
An aqueous solution of titanium tetrachloride corresponding to 192.7 g in terms of TiO ₂ was prepared. On the other hand, 1.93 g of tin tetrachloride converted to SnO ₂ and 14.4 g of hydrochloric acid (35%) were dissolved in pure water to make 1 L. This tin tetrachloride aqueous solution was heated to 60° C. while stirring to hydrolyze the tin tetrachloride to obtain fine core particles. The aforementioned titanium tetrachloride aqueous solution was added to the solution containing the core particles, and then heated to 100° C. and maintained for 1 hour to hydrolyze the titanium tetrachloride to obtain a product. The solution containing this product was cooled to 70° C. while neutralizing the pH of the solution to 7.0 with sodium hydroxide. Next, 15.4 g of an aqueous solution of sodium aluminate was added in terms of Al ₂ O ₃ , and further neutralized with sulfuric acid to a pH of 5.5, thereby precipitating aluminum hydroxide on the surface of the product particles. This slurry was filtered and washed to recover the solid content and dried at 150° C. to obtain fine titanium dioxide particles containing a tin component and coated with aluminum hydroxide.

The titanium dioxide fine particles were calcined in an electric furnace at 600° C. for 1 hour to obtain titanium dioxide fine particles in which the tin component and the aluminum component of Production Example 1 were solid-dissolved.

[Production Example 2]
In Production Example 1, the amount of tin tetrachloride contained in the tin tetrachloride aqueous solution was changed to 5.8 g in terms of _SnO2 , and the amount of sodium aluminate added was changed to ₁₂ g in terms of _Al2O3 . Titanium dioxide fine particles in which the tin component and the aluminum component are solid-dissolved in Production Example 2 were obtained in the same manner as above, except for the above. An electron micrograph of this titanium dioxide fine particle is shown in FIG.

[Production Example 3]
Titanium dioxide fine particles in which the tin component and the aluminum component are solid-dissolved in Production Example 3 were obtained in the same manner as in Production Example 1, except that the firing temperature in the electric furnace was changed to 400°C.

<Evaluation 1: crystal type>
Using the titanium dioxide fine particles of Production Examples 1 to 3 as a sample, an X-ray diffractometer (Ultima IV, manufactured by Rigaku) was used to analyze X-ray tube: Cukα, tube voltage: 40 kV, tube current: 40 mA, divergence slit: 1/ The X-ray diffraction spectrum was measured under the conditions of 2°, scattering slit: 8 mm, receiving slit: open, sampling width: 0.020°, scanning speed: 10.00°/min. For reference, the X-ray diffraction spectrum of Production Example 3 is shown in FIG. As shown in FIG. 2, in the titanium dioxide fine particles of Production Example 3, peaks corresponding to rutile-type titanium dioxide were detected, while peaks corresponding to tin oxide and aluminum oxide were not detected. . This was the same for the samples of Production Examples 1 and 2 (not shown).

<Evaluation 2: Elemental analysis>
Powders of titanium dioxide fine particles of Production Examples 1 to 3 are compacted into pellet-shaped measurement samples, and all element order (semi-quantitative) analysis is performed with a fluorescent X-ray analyzer (ZSX Primus IV, manufactured by Rigaku). ₂ , SnO ₂ and Al ₂ O ₃ were determined. Table 1 shows the measurement results.

<Evaluation 3: BET specific surface area>
The BET specific surface area (m ² /g) of the powder of titanium dioxide fine particles of Production Examples 1 to 3 was determined by the nitrogen adsorption method (BET method) using an automatic fluidized specific surface area measuring device (FlowSorb II 2300, manufactured by Shimadzu Corporation). asked for At this time, desorption was performed at room temperature under nitrogen gas flow, and adsorption was performed at 77K. Table 1 shows the measurement results.

[Example 1]
1.026 g of 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-903, hereinafter referred to as “KBM-903”) and methoxydipropylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd.: Light Acrylate (registered trademark) DPM-A (hereinafter referred to as “DPM-A”) 0.926 g, methyl ethyl ketone (hereinafter referred to as “MEK”) and ethanol (hereinafter referred to as “EtOH”) in a mass ratio of 1:1 20. 9.76 g of the titanium dioxide fine particles of Production Example 1 and 100 g of 0.05 mm zirconia beads were added to the resulting solution and dispersed using a bead mill. After removing the beads, centrifugation was performed and the supernatant was recovered to obtain an organic solvent dispersion of Example 1.

[Example 2]
An organic solvent dispersion of Example 2 was obtained in the same manner as in Example 1, except that the titanium dioxide fine particles were changed to those of Production Example 2.

[Example 3]
The organic solvent of Example 3 was repeated in the same manner as in Example 1, except that the titanium dioxide fine particles were changed to those of Production Example 2 and the organic solvent was changed to propylene glycol monomethyl ether (hereinafter referred to as "PGME"). A dispersion was obtained.

[Example 4]
1.109 g of KBM-903, 0.995 g of methoxy-polyethylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd.: Light Acrylate (registered trademark) 130A, hereinafter referred to as “130A”), and MEK and EtOH at a mass ratio of 1: 8.416 g of the titanium dioxide fine particles of Production Example 3 and 100 g of 0.05 mm zirconia beads were added to the resulting solution, and dispersed using a bead mill. After removing the beads, centrifugation was performed and the supernatant was collected to obtain an organic solvent dispersion of Example 4.

[Comparative Example 1]
1.370 g of KBM-903, 1.230 g of 130A, and 19.00 g of a mixed solvent of MEK and EtOH in a weight ratio of 1:1 were mixed, and the tin component was added to the resulting solution. 10.40 g of commercially available titanium dioxide fine particles (manufactured by Ishihara Sangyo Co., Ltd.: TTO-51(N)) and 100 g of 0.05 mm zirconia beads were added and dispersed by a bead mill. After removing the beads, centrifugation was performed and the supernatant was recovered to obtain an organic solvent dispersion of Comparative Example 1.

[Comparative Example 2]
An organic solvent dispersion of Comparative Example 2 was obtained in the same manner as in Example 2, except that the addition of DPM-A was omitted.

<Evaluation 4: Transmittance of dispersion>
Using a spectrophotometer (manufactured by JASCO Corporation: V-770, quartz cell thickness 1 mm), the concentration of titanium dioxide fine particles in the dispersion was adjusted to 12 g/L, and the transmittance of the dispersion was measured. The concentration of fine titanium dioxide particles in the dispersion was obtained from the residue after heating at 800°C. The measurement wavelength is 420 nm and visible light is used, and the visible light is represented by the average transmittance. Table 2 shows the results.

[Preparation of paint]
Dipentaerythritol hexaacrylate (Japan Kayaku Co., Ltd.: KAYARAD (registered trademark) DPHA) was mixed, and Omnirad (registered trademark)-907 was added in an amount of 5% by mass based on the DPHA to prepare a curable coating composition.

[Preparation of coating film]
The above curable coating composition was appropriately diluted with PGME, applied to a glass substrate, pre-dried at 110° C. for 3 minutes, and cured by irradiation with a high-pressure mercury lamp to prepare a coating film. Three types of coating films with different film thicknesses were prepared for each curable coating composition of each example and comparative example.

<Evaluation 5: Haze and refractive index of coating film>
Using a haze meter (COH-7700, manufactured by Nippon Denshoku Industries Co., Ltd.), the haze of the coating film was measured. In addition, the thickness of the coating film and the refractive index at a measurement wavelength of 589 nm were measured using an ellipsometer (SmartSE, manufactured by Horiba, Ltd.). The film thickness and haze were plotted, and the haze at a film thickness of 3 μm was calculated by linear approximation. Table 2 shows the results.

＊評価不能とは塗料が直ちに固化（ゲル化）してコーティング不可能であったことを示す。

* Unevaluable indicates that the paint solidified (gelled) immediately and could not be coated.

In each of the titanium dioxide fine particles contained in the organic solvent dispersions of Examples 1 to 4, a tin component is dissolved in a solid solution, and an alkoxysilane compound having an amino group and/or an alkoxysilane compound having an amino group on the particle surface of the titanium dioxide fine particles. It was confirmed that the reaction product of the hydrolysis product (KBM-903) and the compound (DPM-A or 130A) having one α,β-unsaturated carbonyl group in the molecule was coated. The organic solvent dispersions of Examples 1 to 4 have higher average visible light transmittance and higher transmittance at a wavelength of 420 nm than the organic solvent dispersions of Comparative Examples. It can be seen that the tin component solid-dissolved in and the reactant coating the particle surface contribute to the improvement of the transparency of the organic solvent dispersion.

In addition, the coating films prepared using the organic solvent dispersions of Examples 1 to 4 had a low haze while maintaining a sufficiently high refractive index, compared with the coating films of Comparative Examples. The transparency of the coating film was also significantly improved. It can be seen that the tin component solid-dissolved in the titanium dioxide fine particles and the reactant coating the particle surface also contribute to the improvement of the transparency of the coating film.

In addition, in the titanium dioxide fine particles of Examples 1 to 4, a tin component and an aluminum component as a third component are dissolved in a solid solution. It can be seen that the performance (and thus the refractive index of the coating film containing this) is not impaired. It is believed that this is because the total contents of the tin component and the aluminum component are controlled to a relatively small amount with respect to the titanium dioxide component.

The present invention provides an alkoxysilane compound having amino groups on the surface of fine titanium dioxide particles containing a tin component and/or a hydrolysis product thereof, and a compound having one α,β-unsaturated carbonyl group in the molecule. A coated titanium dioxide fine particle obtained by coating the surface of a titanium dioxide fine particle containing a tin component with a reactant, wherein the dispersibility of the titanium dioxide fine particle in an organic solvent can be sufficiently improved, whereby the titanium dioxide fine particle possesses It is possible to make full use of the functions and performance. Further, the obtained organic solvent dispersion of the coated titanium dioxide fine particles and the coating film are excellent in transparency and refraction.

Claims (10)

A reaction product of an alkoxysilane compound having an amino group and/or a hydrolysis product thereof and a compound having one α,β-unsaturated carbonyl group in the molecule is applied to the surface of fine titanium dioxide particles containing a tin component. Coated, coated titanium dioxide microparticles. 2. The coated titanium dioxide microparticles according to claim 1, wherein said titanium dioxide microparticles further contain an aluminum component. Claim 1 or Claim 2, wherein the content of the tin component is 0.5% by mass or more and 10% by mass or less in terms of oxide [ _SnO2 / _TiO2 ] with respect to the titanium dioxide of the titanium dioxide fine particles. 3. The coated titanium dioxide microparticles according to . The total content of the tin component and the aluminum component is 1% by mass or more and 15% by mass in terms of oxide [(SnO ₂ +Al ₂ O ₃ )/TiO ₂ ] with respect to the titanium dioxide of the titanium dioxide fine particles. % or less, the coated titanium dioxide fine particles according to any one of claims 1 to 3. An organic solvent dispersion of coated titanium dioxide fine particles, comprising the coated titanium dioxide fine particles according to any one of claims 1 to 4 and an organic solvent. A coating composition comprising an organic solvent dispersion of the coated titanium dioxide fine particles according to any one of claims 1 to 4 or the coated titanium dioxide fine particles according to claim 5, and a binder resin. A coating film comprising the coated titanium dioxide fine particles according to any one of claims 1 to 4 and a binder resin. Titanium dioxide fine particles containing a tin component, an alkoxysilane compound having an amino group and/or a hydrolysis product thereof, and a compound having one α,β-unsaturated carbonyl group in the molecule are mixed in a solvent. Then, the reaction product of the alkoxysilane compound having an amino group and/or its hydrolysis product and the compound having one α,β-unsaturated carbonyl group in the molecule is applied to the surface of the titanium dioxide fine particles. A method for producing coated titanium dioxide fine particles. The fine particles of titanium dioxide containing the tin component are obtained by hydrolyzing a mixture of titanium (oxy)chloride and tin chloride, or by hydrolyzing tin chloride to obtain (oxy)titanium chloride in the presence of core particles. and then calcining the hydrolyzed product at a temperature of 250°C or higher and 1000°C or lower. Titanium dioxide fine particles containing a tin component and an aluminum component are obtained by calcining the product after hydrolysis according to claim 9 at a temperature of 250° C. or more and 1000° C. or less in the presence of an aluminum compound. A method for producing the coated titanium dioxide microparticles described.

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