Titanium oxide particles, a dispersion thereof, a photocatalytic thin film, a member having the photocatalytic thin film on its surface, and a method for producing a dispersion of titanium oxide particles

Abstract

The present invention provides: titanium oxide particles that have higher photocatalytic activity, especially higher photocatalytic activity under visible light than ever before; a dispersion liquid of the titanium oxide particles; a photocatalyst thin film which is formed using this dispersion liquid; a member which has a photocatalyst thin film on the surface; and a method for producing a dispersion liquid of titanium oxide particles.　Titanium oxide particles wherein: (1) a tin component and a transition metal component that enhances photocatalytic activity under visible light are solid-solved therein; and (2) an iron component, a titanium component and a silicon component are adhering to the surfaces. A dispersion liquid of titanium oxide particles obtained by dispersing the titanium oxide particles in an aqueous dispersion medium.

Description

Technical Field

[0001] The present invention relates to titanium oxide particles, a dispersion thereof, a photocatalytic thin film formed using the dispersion, a member having the photocatalytic thin film on its surface, and a method for producing a titanium oxide particle dispersion. More specifically, the present invention relates to visible light-responsive photocatalytic titanium oxide particles and the like that can easily produce a highly transparent photocatalytic thin film that exhibits photocatalytic activity even only with visible light (wavelength 400 to 800 nm).

Background Art

[0002] Photocatalysts are widely used for applications such as cleaning, deodorizing, and antibacterial treatment of member surfaces. The photocatalytic reaction refers to a reaction caused by excited electrons and holes generated when a photocatalyst absorbs light. The decomposition of organic substances by a photocatalyst is considered to mainly occur through the following mechanisms (1) and (2). (1) The generated excited electrons and holes undergo a redox reaction with oxygen and water adsorbed on the photocatalyst surface, and the active species generated by the redox reaction decompose the organic substances. (2) The generated holes directly oxidize and decompose the organic substances adsorbed on the photocatalyst surface.

[0003] Recently, the application of the above-described photocatalytic action has been studied not only for outdoor use where ultraviolet light can be used but also for indoor spaces illuminated by a light source that mostly occupies light in the visible region (wavelength 400 to 800 nm) such as a fluorescent lamp. For example, as a visible light-responsive photocatalyst, a tungsten oxide photocatalyst (Japanese Patent Application Laid-Open No. 2009-148700: Patent Document 1) has been developed. However, since tungsten is a rare element, it is desired to improve the visible light activity of a photocatalyst using titanium, which is a general-purpose element.

[0004] As a method for improving the visible light activity of a titanium oxide photocatalyst, there are methods such as supporting iron or copper on the surface of titanium oxide fine particles or titanium oxide fine particles doped with a metal (for example, JP-A-2012-210632: Patent Document 2, JP-A-2010-104913: Patent Document 3, JP-A-2011-240247: Patent Document 4, JP-A-7-303835: Patent Document 5), a method of preparing titanium oxide fine particles in which tin and a transition metal that enhances visible light activity are solid-soluted (doped) and titanium oxide fine particles in which copper is solid-soluted, and then mixing and using them (International Publication No. 2014 / 045861: Patent Document 6), a method of preparing titanium oxide fine particles in which tin and a transition metal that enhances visible light responsiveness are solid-soluted and titanium oxide fine particles in which an iron group element is solid-soluted, and then mixing and using them (International Publication No. 2016 / 152487: Patent Document 7), etc. are known.

[0005] When a photocatalyst film formed using a visible light-responsive photocatalytic titanium oxide fine particle dispersion obtained by preparing titanium oxide fine particles in which tin and a transition metal that enhances visible light activity are solid-soluted and titanium oxide fine particles in which an iron group element is solid-soluted according to Patent Document 7 and then mixing them is used, high decomposition activity can be obtained only under the condition of light in the visible region. Also, when a photocatalyst film formed using a titanium oxide fine particle dispersion in which an iron component is adsorbed (=supported) on the surface of titanium oxide fine particles in which tin and a transition metal that enhances visible light activity are solid-soluted is used, it has been shown that acetaldehyde gas can be decomposed only under the condition of light in the visible light region. However, since the quality of the photocatalyst film obtained by aggregation and precipitation of titanium oxide fine particles due to the iron component is impaired, the amount of the iron component is limited, and the obtained photocatalytic activity is low.

[0006] As described above, although studies on improving photocatalytic activity have been actively conducted, in the actual environment, it is important that harmful substances are decomposed and removed as quickly as possible. Therefore, further improvement of photocatalytic activity is required.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

[0008] Accordingly, an object of the present invention is to provide titanium oxide particles capable of obtaining higher photocatalytic activity, particularly visible light activity, than conventional ones, a dispersion thereof, a photocatalytic thin film formed using the dispersion, a member having the photocatalytic thin film on its surface, and a method for producing a dispersion of titanium oxide particles. [Means for Solving the Problems

[0009] In order to achieve the above object, the present inventors have examined in detail the metal elements to be dissolved in titanium oxide particles and their combinations, the metal elements to be added to titanium oxide particles and their combinations, and their quantitative ratios. As a result, it has been found that the photocatalytic activity, particularly the visible light activity, of titanium oxide particles having an iron component, a titanium component, and a silicon component adhering to the surface of titanium oxide particles in which a specific metal is dissolved is remarkably improved, and the present invention has been completed.

[0010] Accordingly, the present invention provides the following titanium oxide particles, a dispersion thereof, a photocatalytic thin film formed using the dispersion, a member having the photocatalytic thin film on its surface, and a method for producing a dispersion of titanium oxide particles. [1 1) A tin component and a transition metal component for enhancing visible light activity are dissolved, 2) Titanium oxide particles with iron, titanium, and silicon components adhering to the surface. [2] The titanium oxide particles according to [1], wherein the transition metal component that enhances visible light activity and is dissolved in the titanium oxide particles is at least one selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium. [3] The titanium oxide particles according to [2], wherein the transition metal component that enhances visible light activity and is dissolved in the titanium oxide particles is at least one selected from molybdenum, tungsten, and vanadium components. [4] The titanium oxide particles according to any one of [1] to [3], wherein the content of the tin component dissolved in the titanium oxide particles is 1 to 1,000 in terms of the molar ratio (TiO2 / Sn) with titanium oxide. [5] The titanium oxide particles according to any one of [1] to [4], wherein the molar ratio of the iron component to titanium oxide (TiO2 / Fe) is 10 to 10,000, the molar ratio of the titanium component to titanium oxide (TiO2 / Ti) is 10 to 10,000, and the molar ratio of the silicon component to titanium oxide (TiO2 / Si) is 1 to 10,000. [6] The titanium oxide particles according to [3], wherein the amount of each of the molybdenum, tungsten, and vanadium components dissolved in the titanium oxide particles is 1 to 10,000 in terms of the molar ratio (TiO2 / Mo, TiO2 / W, or TiO2 / V) with titanium oxide. [7] A titanium oxide particle dispersion liquid in which the titanium oxide particles according to any one of [1] to [6] are dispersed in an aqueous dispersion medium. [8] The titanium oxide particle dispersion liquid according to [7], further containing a binder. [9] The titanium oxide particle dispersion liquid according to [8], wherein the binder is a silicon compound-based binder.

[10] A photocatalytic thin film containing the titanium oxide particles according to any one of [1] to [6].

[11] Furthermore, the photocatalytic thin film according to

[10] containing a binder.

[12] A member having the photocatalytic thin film according to

[10] or

[11] on its surface.

[13] The method for producing a titanium oxide particle dispersion according to any one of [7] to [9], having the following steps (1) to (4). (1) A step of producing a peroxotitanic acid solution containing a tin component and a transition metal component from a raw material titanium compound, a tin compound, a transition metal compound, a basic substance, hydrogen peroxide, and an aqueous dispersion medium (2) A step of heating the peroxotitanic acid solution containing a tin component and a transition metal component produced in the step (1) at 80 to 250 ° C under pressure control to obtain a titanium oxide particle dispersion containing a tin component and a transition metal component (3) A step of producing a solution or dispersion of an iron component, a titanium component, and a silicon component from an iron compound, a titanium compound, a silicon compound, and an aqueous dispersion medium (4) A step of mixing the titanium oxide particle dispersion produced in the step (2) with the solution or dispersion of the iron compound, titanium compound, and silicon compound produced in the step (3) to obtain a dispersion [Advantages of the Invention]

[0011] The titanium oxide particles of the present invention have a higher photocatalytic activity than conventional ones, particularly a high photocatalytic activity even only with visible light (wavelength 400 to 800 nm). Further, a highly transparent photocatalytic thin film can be easily produced from the dispersion of the titanium oxide particles. Therefore, the titanium oxide particles of the present invention are useful for members used in an indoor space illuminated by a light source mainly composed of visible light such as a fluorescent lamp or a white LED. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, the present invention will be described in detail. [Titanium Oxide Particle Dispersion] The titanium oxide particle dispersion of the present invention contains, in an aqueous dispersion medium, 1) titanium oxide particles in which a tin component and a transition metal that enhances visible light activity are solid-dissolved, and 2) an iron component, a titanium component, and a silicon component. The iron component, titanium component, and silicon component contained in the titanium oxide particle dispersion adhere to the surface of the titanium oxide particles, but the iron component, titanium component, and silicon component may be free in the titanium oxide particle dispersion.

[0013] As the aqueous dispersion medium, it is preferable to use water, but a mixed solvent of water and a hydrophilic organic solvent mixed with water at an arbitrary ratio may also be used. As the water, for example, purified water such as filtered water, deionized water, distilled water, and pure water is preferable. Further, as the hydrophilic organic solvent, for example, alcohols such as methanol, ethanol, and isopropanol, glycols such as ethylene glycol, and glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol - n - propyl ether are preferable. When using a mixed solvent, the ratio of the hydrophilic organic solvent in the mixed solvent is preferably more than 0% by mass and 50% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less.

[0014] The titanium oxide particles are those in which titanium oxide used as a photocatalyst is solid-dissolved with a tin component and a transition metal component that enhances visible light activity. The fact that the titanium oxide particle dispersion of the present invention "contains an iron component, a titanium component, and a silicon component" means that the dispersion contains the iron component, titanium component, and silicon component.

[0015] As the crystal phase of the titanium oxide particles, usually, three types, rutile type, anatase type, and brookite type, are known. However, the titanium oxide particles of the present invention are preferably mainly of the rutile type or anatase type, and particularly preferably mainly of the rutile type. Here, the term "mainly" means containing 50% by mass or more of the titanium oxide particles of the crystal phase in the whole titanium oxide particles, preferably 70% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0016] Here, in this specification, a solid solution refers to a phase in which atoms at lattice points of a certain crystal phase are replaced by other atoms or other atoms enter the interstitial sites, that is, a mixed phase in which other substances are considered to be dissolved in a certain crystal phase, and the crystal phase refers to a homogeneous phase. A substitutional solid solution is one in which solvent atoms at lattice points are replaced by solute atoms, and an interstitial solid solution is one in which solute atoms enter the interstitial sites. In this specification, either of these is meant.

[0017] The titanium oxide particles of the present invention are characterized by forming a solid solution with tin atoms and transition metal atoms that enhance visible light responsiveness. The solid solution may be substitutional or interstitial. The substitutional solid solution of titanium oxide is formed by replacing titanium sites of titanium oxide crystals with various metal atoms, and the interstitial solid solution of titanium oxide is formed by various metal atoms entering the interstitial sites of titanium oxide crystals. When various metal atoms are solid-dissolved in titanium oxide, when measuring the crystal phase by X-ray diffraction or the like, only the peaks of the crystal phase of titanium oxide are observed, and the peaks of compounds derived from the various added metal atoms are not observed.

[0018] The method of solid-dissolving a different metal in a metal oxide crystal is not particularly limited, and examples include vapor phase methods (CVD method, PVD method, etc.), liquid phase methods (hydrothermal method, sol-gel method, etc.), and solid phase methods (high temperature firing method, etc.).

[0019] The tin component dissolved in the titanium oxide particles is for enhancing the visible light responsiveness of the photocatalytic thin film. However, it may be derived from any tin compound. For example, it may be elemental tin (Sn), oxides (SnO, SnO2), hydroxides, chlorides (SnCl2, SnCl4), nitrates (Sn(NO3)2), sulfates (SnSO4), halides other than chlorides (Br, I), oxoacid salts (Na2SnO3, K2SnO3), complex compounds, etc. One or a combination of two or more of these may be used. Among them, it is preferable to use oxides (SnO, SnO2), chlorides (SnCl2, SnCl4), sulfates (SnSO4), and oxoacid salts (Na2SnO3, K2SnO3).

[0020] The amount of the tin component dissolved in the titanium oxide particles is 1 to 1,000, preferably 5 to 500, more preferably 5 to 100 in terms of the molar ratio (TiO2 / Sn) with titanium oxide. This is because when the molar ratio is less than 1, the content ratio of titanium oxide may decrease and the photocatalytic effect may not be fully exerted. When it exceeds 1,000, the visible light responsiveness may be insufficient.

[0021] The transition metal dissolved in the titanium oxide particles is for enhancing the visible light responsiveness of the photocatalytic thin film. It is one or more elements selected from Groups 3 to 11 of the periodic table and can be selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, cerium, etc. Among them, molybdenum, tungsten, and vanadium are preferable.

[0022] The transition metal component dissolved in the titanium oxide particles may be derived from any of the transition metal compounds, and examples include metals, oxides, hydroxides, chlorides, nitrates, sulfates, halides other than chlorides (Br, I), oxoacid salts, various complex compounds, etc. One or a combination of two or more of these are used.

[0023] The amount of the transition metal component dissolved in the titanium oxide particles can be appropriately selected according to the type of the transition metal component, but is preferably 1 to 10,000 in terms of the molar ratio (TiO2 / transition metal) with titanium oxide.

[0024] When molybdenum is selected as the transition metal component dissolved in the titanium oxide particles, the molybdenum component may be derived from a molybdenum compound. For example, simple metal of molybdenum (Mo), oxides (MoO2, MoO3), hydroxides, chlorides (MoCl3, MoCl5), nitrates, sulfates, halides other than chlorides (Br, I), molybdic acid (oxo acid) and its salts (H2MoO4, Na2MoO4, K2MoO4), complex compounds, etc. may be mentioned, and one or a combination of two or more of these may be used. Among them, it is preferable to use oxides (MoO2, MoO3), chlorides (MoCl3, MoCl5), oxo acids and their salts (H2MoO4, Na2MoO4, K2MoO4).

[0025] The amount of the molybdenum component dissolved in the titanium oxide particles is preferably 1 to 10,000 in terms of the molar ratio (TiO2 / Mo) with titanium oxide, more preferably 5 to 5,000, and still more preferably 20 to 1,000. This is because when the molar ratio is less than 1, the content ratio of titanium oxide may decrease and the photocatalytic effect may not be fully exerted, and when it exceeds 10,000, the visible light responsiveness may be insufficient.

[0026] When tungsten is selected as the transition metal component dissolved in the titanium oxide particles, the tungsten component may be derived from a tungsten compound. For example, simple metal of tungsten (W), oxides (WO3), hydroxides, chlorides (WCl4, WCl6), nitrates, sulfates, halides other than chlorides (Br, I), tungstic acid and oxo acid salts (H2WO4, Na2WO4, K2WO4), complex compounds, etc. may be mentioned, and one or a combination of two or more of these may be used. Among them, it is preferable to use oxides (WO3), chlorides (WCl4, WCl6), oxo acid salts (Na2WO4, K2WO4).

[0027] The amount of tungsten component dissolved in titanium oxide particles is preferably 1 to 10,000, more preferably 5 to 5,000, and still more preferably 20 to 2,000 in terms of the molar ratio (TiO2 / W) with titanium oxide. This is because when the molar ratio is less than 1, the content ratio of titanium oxide may decrease and the photocatalytic effect may not be fully exerted, and when it exceeds 10,000, the visible light responsiveness may be insufficient.

[0028] When vanadium is selected as the transition metal component dissolved in titanium oxide particles, the vanadium component may be derived from a vanadium compound. For example, metallic vanadium (V), oxides (VO, V2O3, VO2, V2O5), hydroxides, chlorides (VCl5), oxychlorides (VOCl3), nitrates, sulfates, oxysulfates (VOSO4), halides (Br, I) other than chlorides, oxoacid salts (Na3VO4, K3VO4, KVO3), complex compounds, etc. may be mentioned, and one or more of these may be used in combination. Among them, it is preferable to use oxides (V2O3, V2O5), chlorides (VCl5), oxychlorides (VOCl3), oxysulfates (VOSO4), and oxoacid salts (Na3VO4, K3VO4, KVO3).

[0029] The amount of vanadium component dissolved in titanium oxide particles is preferably 1 to 10,000, more preferably 10 to 10,000, and still more preferably 100 to 10,000 in terms of the molar ratio (TiO2 / V) with titanium oxide. This is because when the molar ratio is less than 1, the content ratio of titanium oxide may decrease and the photocatalytic effect may not be fully exerted, and when it exceeds 10,000, the visible light responsiveness may be insufficient.

[0030] As the transition metal component dissolved in titanium oxide particles, a plurality of them can be selected from molybdenum, tungsten, and vanadium, and the amount of each component at that time can be selected from the above ranges. However, the molar ratio [TiO2 / (Mo + W + V)] of the total amount of each component and titanium oxide is 1 or more and less than 10,000.

[0031] The titanium oxide particles may be used alone or in combination of two or more. When two or more kinds having different visible light responsivities are combined, an effect of enhancing the visible light activity may be obtained.

[0032] The iron component, titanium component and silicon component contained in the titanium oxide particle dispersion and adhering to the surface of the titanium oxide particles enhance the visible light responsivity of the photocatalytic thin film.

[0033] The iron component contained in the titanium oxide particle dispersion is for enhancing the photocatalytic activity of the photocatalytic thin film, and any iron compound-derived one may be used. For example, elemental iron (Fe), oxides (Fe2O3, Fe3O4), hydroxides (Fe(OH)2, Fe(OH)3), oxyhydroxides (FeO(OH)), chlorides (FeCl2, FeCl3), nitrates (Fe(NO)3), sulfates (FeSO4, Fe2(SO4)3), halides (Br, I) other than chlorides, complex compounds, etc. may be mentioned, and one or a combination of two or more of these may be used.

[0034] The content of the iron component contained in the titanium oxide particle dispersion is preferably 10 to 10,000 in terms of the molar ratio (TiO2 / Fe) with titanium oxide, more preferably 20 to 5,000, and still more preferably 50 to 2,000. This is because when the molar ratio is less than 10, the quality of the photocatalytic thin film obtained by aggregation and precipitation of titanium oxide may deteriorate and the photocatalytic effect may not be fully exhibited, and when it exceeds 10,000, the visible light responsivity may be insufficient.

[0035] The titanium component contained in the titanium oxide particle dispersion is for enhancing the photocatalytic activity of the photocatalytic thin film, and any titanium compound-derived one may be used. For example, elemental titanium (Ti), hydroxide (Ti(OH)4), oxyhydroxide (TiO(OH)2), chlorides (TiCl4, TiCl3, TiCl2), nitrates (Ti(NO)4), sulfates (Ti(SO4)2, TiOSO4), halides (Br, I) other than chlorides, complex compounds, etc. may be mentioned, and one or a combination of two or more of these may be used.

[0036] The content of the titanium component contained in the titanium oxide particle dispersion is preferably 10 to 10,000, more preferably 20 to 5,000, and still more preferably 50 to 2,000 in terms of the molar ratio (TiO2 / Ti) with titanium oxide. This is because when the molar ratio is less than 10, the quality of the photocatalytic thin film obtained by the aggregation and precipitation of titanium oxide may deteriorate and the photocatalytic effect may not be fully exerted. When it exceeds 10,000, the effect of enhancing the activity may be insufficient.

[0037] The silicon component contained in the titanium oxide particle dispersion suppresses the aggregation and precipitation of titanium oxide, iron component and titanium component at the time of adding the iron component and titanium component, thereby preventing the deterioration of the quality of the photocatalytic thin film and suppressing the decrease of the photocatalytic effect. However, it may be derived from a silicon compound. Examples of the silicon compound include metallic silicon (Si), oxides (SiO, SiO2), alkoxides (Si(OCH3)4, Si(OC2H5)4, Si(OCH(CH3)2)4), silicates (sodium salts, potassium salts), and activated silicic acid obtained by removing at least a part of ions such as sodium and potassium from these silicates. One or more of these may be used in combination. Among them, it is preferable to use silicate (sodium silicate), activated silicic acid, and particularly activated silicic acid.

[0038] The content of the silicon component contained in the titanium oxide particle dispersion is preferably 1 to 10,000, more preferably 2 to 5,000, and still more preferably 5 to 2,000 in terms of the molar ratio (TiO2 / Si) with titanium oxide. This is because when the molar ratio is less than 1, the content ratio of titanium oxide may decrease and the photocatalytic effect may not be fully exerted. When it exceeds 10,000, the effect of suppressing the aggregation and precipitation of titanium oxide may be insufficient.

[0039] The titanium oxide particles in the titanium oxide particle dispersion containing an iron component, a titanium component and a silicon component have a volume-based 50% cumulative distribution diameter (hereinafter, D 50(which may be denoted as) are preferably 3 to 50 nm each, more preferably 3 to 30 nm, and even more preferably 3 to 20 nm. D 50 This is because when it is less than 3 nm, the photocatalytic activity may be insufficient, and when it exceeds 50 nm, the dispersion may become opaque.

[0040] Also, the volume-based 90% cumulative distribution diameter (hereinafter sometimes denoted as D 90 (which may be denoted as) are preferably 5 to 100 nm each, more preferably 5 to 80 nm. D 90 This is because when it is less than 5 nm, the photocatalytic activity may be insufficient, and when it exceeds 100 nm, the dispersion may become opaque. The titanium oxide particles of the present invention are particles in which D 50 and D 90 are within the above-described ranges, which is preferable because they have high photocatalytic activity and form a highly transparent dispersion. Note that as an apparatus for measuring D 50 and D 90 of the titanium oxide particles in the titanium oxide particle dispersion, for example, ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.), NanoTrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.), LA-910 (manufactured by Horiba, Ltd.), etc. can be used.

[0041] The concentration of the titanium oxide particles in the titanium oxide particle dispersion is preferably 0.01 to 20% by mass, particularly preferably 0.5 to 10% by mass, from the viewpoint of ease of producing a photocatalytic thin film with a required thickness.

[0042] Furthermore, a binder may be added to the titanium oxide particle dispersion for the purpose of facilitating the application of the dispersion to the surfaces of various members described later and facilitating the adhesion of the particles. Examples of the binder include metal compound-based binders containing silicon, aluminum, titanium, zirconium, etc., and organic resin-based binders containing fluorine-based resins, acrylic resins, urethane-based resins, etc.

[0043] The mass ratio of the binder to titanium oxide [titanium oxide / binder] is preferably added and used in the range of 99 to 0.01, more preferably 9 to 0.1, and still more preferably 2.5 to 0.4. This is because when the above mass ratio exceeds 99, the adhesion of titanium oxide particles to the surfaces of various members becomes insufficient, and when it is less than 0.01, the visible light activity may become insufficient.

[0044] Among them, in order to obtain an excellent photocatalytic thin film with high photocatalytic activity and transparency, it is particularly preferable to add and use a silicon compound-based binder in the mass ratio (titanium oxide / silicon compound-based binder) range of 99 to 0.01, more preferably 9 to 0.1, and still more preferably 2.5 to 0.4. Here, the silicon compound-based binder is a colloidal dispersion, solution, or emulsion of a silicon compound containing a solid or liquid silicon compound in an aqueous dispersion medium. Specifically, it includes colloidal silica (preferred particle size 1 to 150 nm); silicate solutions such as silicate; silane, siloxane hydrolyzate emulsion; silicone resin emulsion; emulsions of copolymers of silicone resins such as silicone-acrylic resin copolymers and silicone-urethane resin copolymers with other resins, etc.

[0045] <Method for producing titanium oxide particle dispersion> The method for producing the titanium oxide particle dispersion of the present invention is prepared by separately producing a titanium oxide particle dispersion and a solution or dispersion of an iron component, a titanium component, and a silicon component, and then mixing the titanium oxide particle dispersion with the solution or dispersion of the iron component, the titanium component, and the silicon component.

[0046] As a method for producing a titanium oxide particle dispersion in which a tin component and a transition metal component for enhancing visible light responsiveness are solid-dissolved and which contains an iron component, a titanium component, and a silicon component, specifically, a production method having the following steps (1) to (4) can be mentioned. (1) A step of producing a peroxotitanic acid solution containing a tin component and a transition metal component from a raw material titanium compound, a tin compound, a transition metal compound, a basic substance, hydrogen peroxide, and an aqueous dispersion medium (2) The step of heating the peroxotitanic acid solution containing a tin component and a transition metal component produced in the step (1) under pressure control at 80 to 250 °C to obtain a titanium oxide particle dispersion liquid containing a tin component and a transition metal component (3) The step of producing a solution or dispersion liquid of an iron component, a titanium component, and a silicon component from an iron compound, a titanium compound, a silicon compound, and an aqueous dispersion medium (4) The step of mixing the titanium oxide particle dispersion liquid produced in the step (2) with the solution or dispersion liquid of the iron compound, titanium compound, and silicon compound produced in the step (3) to obtain a dispersion liquid

[0047] Steps (1) to (2) are steps for obtaining a titanium oxide particle dispersion liquid in which a tin component and a transition metal component that enhance visible light responsiveness are dissolved. Step (3) is a step for obtaining a solution or dispersion liquid of an iron component, a titanium component, and a silicon component. And step (4) is finally a step for obtaining a dispersion liquid containing titanium oxide particles in which a tin component and a transition metal component that enhance visible light responsiveness are dissolved and an iron component, a titanium component, and a silicon component are adhered to the surface. As already described, as the transition metal compound used in step (1), it is preferable to use at least one of a molybdenum compound, a tungsten compound, and a vanadium compound. Therefore, each step will be described in detail on this premise below.

[0048] · Step (1): In step (1), a peroxotitanic acid solution containing a tin component and a transition metal component is produced by reacting a raw material titanium compound, a tin compound, a transition metal compound, a basic substance, and hydrogen peroxide in an aqueous dispersion medium.

[0049] As the reaction method, any of the following methods i) to iii) may be used. i) To the raw material titanium compound and the basic substance in the aqueous dispersion medium, a tin compound and a transition metal compound are added and dissolved, then it is made into titanium hydroxide containing a tin component and a transition metal component, impurities ions other than the contained metal ions are removed, and hydrogen peroxide is added to make peroxotitanic acid containing a tin component and a transition metal component ii) A method in which a basic substance is added to a raw material titanium compound in an aqueous dispersion medium to form titanium hydroxide, impurities ions other than the contained metal ions are removed, a tin compound and a transition metal compound are added, and then hydrogen peroxide is added to obtain peroxotitanic acid containing a tin component and a transition metal component iii) A method in which a basic substance is added to a raw material titanium compound in an aqueous dispersion medium to form titanium hydroxide, impurities ions other than the contained metal ions are removed, hydrogen peroxide is added to form peroxotitanic acid, and then a tin compound and a transition metal compound are added to obtain peroxotitanic acid containing a tin component and a transition metal component In the previous stage of the method of i), the "raw material titanium compound and basic substance in the aqueous dispersion medium" is divided into two aqueous dispersion media such as "aqueous dispersion medium in which the raw material titanium compound is dispersed" and "aqueous dispersion medium in which the basic substance is dispersed", and according to the solubility of each compound of the tin compound and the transition metal compound in the two liquids, each compound may be dissolved in one or both of the two liquids, and then the two are mixed.

[0050] After obtaining peroxotitanic acid containing a tin component and a transition metal component in this way, by subjecting it to the hydrothermal reaction in step (2) described later, titanium oxide particles in which the various metals are solid-dissolved in titanium oxide can be obtained.

[0051] Here, examples of the raw material titanium compound include inorganic acid salts such as titanium chlorides, nitrates, and sulfates, organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid, and titanium hydroxide precipitated by adding an alkali to an aqueous solution thereof and hydrolyzing. One or more of these may be used in combination. Among them, it is preferable to use titanium chlorides (TiCl3, TiCl4).

[0052] As the tin compound, transition metal compound, and aqueous dispersion medium, the aforementioned ones are each used so as to have the aforementioned formulation. The concentration of the aqueous solution of the raw material titanium compound formed from the raw material titanium compound and the aqueous dispersion medium is preferably 60% by mass or less, particularly preferably 30% by mass or less. The lower limit of the concentration is appropriately selected, but is usually preferably 1% by mass or more.

[0053] The basic substance is for smoothly converting the raw material titanium compound into titanium hydroxide. Examples include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide and potassium hydroxide, ammonia, amine compounds such as alkanolamine and alkylamine. Among them, it is particularly preferable to use ammonia, and it is added and used in an amount such that the pH of the aqueous solution of the raw material titanium compound is 7 or more, particularly pH 7 to 10. The basic substance may be used as an aqueous solution with an appropriate concentration together with the above aqueous dispersion medium.

[0054] Hydrogen peroxide is for converting the above raw material titanium compound or titanium hydroxide into peroxotitanium, that is, a titanium oxide compound containing a Ti-O-O-Ti bond, and is usually used in the form of an aqueous hydrogen peroxide solution. The addition amount of hydrogen peroxide is preferably 1.5 to 20 times the total amount of substance of Ti, transition metal, and Sn in moles. In the reaction of adding hydrogen peroxide to convert the raw material titanium compound or titanium hydroxide into peroxotitanic acid, the reaction temperature is preferably 5 to 80°C, and the reaction time is preferably 30 minutes to 24 hours.

[0055] The peroxotitanic acid solution containing the tin component and the transition metal component thus obtained may contain an alkaline substance or an acidic substance for pH adjustment or the like. Examples of the alkaline substance herein include ammonia, sodium hydroxide, calcium hydroxide, alkylamine, etc., and examples of the acidic substance include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, phosphoric acid, hydrogen peroxide, and organic acids such as formic acid, citric acid, oxalic acid, lactic acid, glycolic acid. In this case, the pH of the obtained peroxotitanic acid solution containing the tin component and the transition metal component is preferably 1 to 9, particularly preferably 4 to 7, from the viewpoint of handling safety.

[0056] · Step (2): In step (2), the peroxotitanic acid solution containing the tin component and the transition metal component obtained in the above step (1) is subjected to a hydrothermal reaction at a temperature of 80 to 250 °C, preferably 100 to 250 °C, for 0.01 to 24 hours under pressure control. The reaction temperature is appropriately 80 to 250 °C from the viewpoints of reaction efficiency and reaction controllability. As a result, the peroxotitanic acid containing the tin component and the transition metal component is converted into titanium oxide particles in which the tin component and the transition metal component are solid-dissolved. Here, "under pressure control" means that when the reaction temperature exceeds the boiling point of the dispersion medium, appropriate pressure is applied to maintain the reaction temperature so that the reaction temperature can be maintained, and it includes the case of controlling at atmospheric pressure when the temperature is below the boiling point of the dispersion medium. The pressure used here is usually about 0.12 to 4.5 MPa, preferably about 0.15 to 4.5 MPa, more preferably about 0.20 to 4.5 MPa. The reaction time is preferably 1 minute to 24 hours. By this step (2), a dispersion of titanium oxide particles in which the tin component and the transition metal component are solid-dissolved is obtained. The pH of the titanium oxide particle dispersion in which the tin component and the transition metal component obtained in this step (2) are dissolved is preferably 8 to 14, more preferably 10 to 14. The titanium oxide particle dispersion in which the tin component and the transition metal component obtained in this step (2) are dissolved may contain an alkaline substance or an acidic substance for pH adjustment or the like so as to have the aforementioned pH. The alkaline substance, acidic substance, and the method for pH adjustment are the same as those of the peroxotitanic acid solution obtained in the aforementioned step (1).

[0057] The particle diameters (D 50 and D 90 ) of the titanium oxide particles obtained here are preferably within the range as described above, but it is possible to control the particle diameter by adjusting the reaction conditions. For example, the particle diameter can be reduced by shortening the reaction time or the temperature rising time.

[0058] · Step (3): In step (3), separately from the above steps (1) to (2), a solution or dispersion of an iron component, a titanium component, and a silicon component is produced by dissolving or dispersing a raw material iron compound, a raw material titanium compound, and a raw material silicon compound in an aqueous dispersion medium.

[0059] Examples of the raw material iron compound include the above-described iron compounds, such as metallic iron (Fe), oxides (Fe2O3, Fe3O4), hydroxides (Fe(OH)2, Fe(OH)3), oxyhydroxides (FeO(OH)), chlorides (FeCl2, FeCl3), nitrates (Fe(NO)3), sulfates (FeSO4, Fe2(SO4)3), halides (Br, I) other than chlorides, complex compounds, etc. One or a combination of two or more of these may be used. Among them, it is preferable to use oxides (Fe2O3, Fe3O4), oxyhydroxides (FeO(OH)), chlorides (FeCl2, FeCl3), nitrates (Fe(NO)3), and sulfates (FeSO4, Fe2(SO4)3).

[0060] As the raw material titanium compound, the titanium compounds described above can be used, for example, metallic titanium (Ti), hydroxide (Ti(OH)4), oxyhydroxide (TiO(OH)2), chloride (TiCl4, TiCl3, TiCl2), nitrate (Ti(NO)4), sulfate (Ti(SO4)2, TiOSO4), halide (Br, I) compounds other than chloride, complex compounds, peroxotitanium compounds (titanium oxide compounds containing Ti - O - O - Ti bonds), etc. One or more of these may be used in combination. Among them, it is preferable to use hydroxide (Ti(OH)4), oxyhydroxide (TiO(OH)2), chloride (TiCl4, TiCl3, TiCl2), nitrate (Ti(NO)4), sulfate (Ti(SO4)2, TiOSO4), peroxotitanium compounds (titanium oxide compounds containing Ti - O - O - Ti bonds).

[0061] As the raw material silicon compound, the silicon compounds described above can be used, for example, metallic silicon (Si), oxides (SiO, SiO2), alkoxides (Si(OCH3)4, Si(OC2H5)4, Si(OCH(CH3)2)4), silicates (sodium salts, potassium salts), and active silicic acids obtained by removing ions such as sodium and potassium from these silicates. One or more of these may be used in combination. Among them, it is preferable to use silicates (sodium silicate) or active silicic acids. Active silicic acid can be obtained, for example, by adding a cation exchange resin to an aqueous sodium silicate solution in which sodium silicate is dissolved in pure water to remove at least a part of the sodium ions. It is preferable to add the cation exchange resin so that the pH of the obtained active silicic acid solution is 2 - 10, preferably 2 - 7.

[0062] The solution or dispersion containing the iron component, titanium component, and silicon component thus obtained may also contain an alkaline substance or an acidic substance for pH adjustment, etc. The alkaline substance, acidic substance, and pH adjustment mentioned here can be handled in the same manner as described above. Iron component , titanium component The pH of the solution or dispersion containing the silicon component is preferably 1 - 7, more preferably 1 - 5.

[0063] The concentration of the raw material iron compound in the solution or dispersion of the iron component, titanium component and silicon component produced in step (3) is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass. The concentration of the raw material titanium compound is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass. The concentration of the raw material silicon compound is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass.

[0064] · Step (4): In step (4), the titanium oxide particle dispersion obtained in step (2) is mixed with the solution or dispersion of the iron component, titanium component and silicon component obtained in step (3). The mixing method is not particularly limited, and it may be a method of stirring with a stirrer or a method of dispersing with an ultrasonic disperser. The temperature during mixing is 20 to 100 °C, preferably 20 to 80 °C, more preferably 20 to 40 °C, and the time is preferably 1 minute to 3 hours. Regarding the mixing ratio, it may be mixed so that the molar ratio of TiO2 to Fe, Ti and Si in the titanium oxide particle dispersion is the molar ratio as described above.

[0065] The titanium oxide particle dispersion obtained in the above steps (1) to (4) may contain an alkaline substance or an acidic substance for pH adjustment or the like, and the above-mentioned substances can be used as the pH adjuster. Further, ion exchange treatment or filtration washing treatment may be performed to adjust the ion component concentration, or solvent replacement treatment may be performed to change the solvent component. The pH of the titanium oxide particle dispersion is preferably 7 to 14, more preferably 8 to 12.

[0066] The mass of the titanium oxide particles contained in the titanium oxide particle dispersion can be calculated from the mass and concentration of the titanium oxide particle dispersion. The measurement method of the concentration of the titanium oxide particle dispersion is as follows: A part of the titanium oxide particle dispersion is sampled, heated at 105 °C for 1 hour to volatilize the solvent, and then calculated according to the following formula from the mass of the non-volatile component (titanium oxide particles) and the mass of the sampled titanium oxide particle dispersion. Concentration of titanium oxide particle dispersion (%) = [Mass of non-volatile matter (g) / Mass of titanium oxide particle dispersion (g)] × 100

[0067] As described above, the total concentration of the iron component, titanium component, silicon component and titanium oxide particles in the titanium oxide particle dispersion thus prepared is preferably 0.01 to 20% by mass, particularly preferably 0.5 to 10% by mass, in terms of the ease of producing a photocatalytic thin film with a required thickness. Regarding the concentration adjustment, when the concentration is higher than the desired concentration, the concentration can be lowered by adding an aqueous solvent for dilution, and when it is lower than the desired concentration, the concentration can be increased by volatilizing or filtering off the aqueous solvent. The concentration can be calculated as described above.

[0068] When adding the above-mentioned binder for enhancing the film-forming property, it is preferable to add the above-mentioned binder solution (aqueous binder solution) to the titanium oxide particle dispersion whose concentration has been adjusted as described above so as to reach the desired concentration after mixing. The silicon component contained in the titanium oxide particle dispersion suppresses the aggregation and precipitation of the titanium oxide particles, iron component and titanium component, and suppresses the decrease in photocatalytic activity, and is added simultaneously when mixing the titanium oxide particles with the iron component and titanium component. On the other hand, the binder enhances the film-forming property of the titanium oxide particle dispersion and is added after preparing the titanium oxide particle dispersion and before coating, and the two are different.

[0069] <Titanium Oxide Particles> The titanium oxide particles of the present invention are characterized in that a tin component and a transition metal for enhancing visible light activity are solid-dissolved, and an iron component, a titanium component and a silicon component are attached to the surface. The iron component, titanium component and silicon component only need to be attached to at least a part of the surface of the titanium oxide particles, and may be attached to the entire surface.

[0070] The method for attaching the iron component, titanium component, and silicon component to the surface of the titanium oxide particles is not particularly limited. Examples include a method of mixing in a solid state (mixing titanium oxide particle powder with powder composed of an iron component, a titanium component, and a silicon component), a method of mixing in a liquid state (mixing a titanium oxide particle dispersion with a solution or dispersion composed of an iron component, a titanium component, and a silicon component), and a method of mixing a solid and a liquid (mixing a solution or dispersion composed of an iron component, a titanium component, and a silicon component with titanium oxide particle powder, or mixing powder composed of an iron component, a titanium component, and a silicon component with a titanium oxide particle dispersion). Since the silicon component plays a role in suppressing the aggregation of the iron component and the titanium component, it is preferable to mix the iron component, the titanium component, and the silicon component in advance and then mix them with the titanium oxide particles. Also, the iron component and the titanium component may be mixed separately. Specifically, after mixing the iron component and the silicon component with the titanium oxide particles, the titanium component and the silicon component may be mixed, or conversely, after mixing the titanium component and the silicon component with the titanium oxide particles, the iron component and the silicon component may be mixed. Examples of the mixing method include those described above. Among them, the method of mixing in a liquid state is preferable, and the method by steps (1) to (4) as in the above-described method for producing the titanium oxide particle dispersion is more preferable.

[0071] On the surface of the titanium oxide particles, it is sufficient that at least a part of the mixed iron component, titanium component, and silicon component adheres, and all of the mixed iron component, titanium component, and silicon component may adhere. Furthermore, it is preferable that the iron component, the titanium component, and the silicon component directly adhere to the surface of the titanium oxide particles, respectively.

[0072] <Photocatalytic thin film containing titanium oxide particles · Member having the photocatalytic thin film on the surface> The titanium oxide particle dispersion of the present invention can be used to form a photocatalytic film on the surface of various members. Here, the various members are not particularly limited, but examples of the material of the members include organic materials and inorganic materials. These can have various shapes according to their respective purposes and uses.

[0073] Examples of organic materials include synthetic resin materials such as vinyl chloride resin (PVC), polyethylene (PE), polypropylene (PP), polycarbonate (PC), acrylic resin, polyacetal, fluororesin, silicone resin, ethylene-vinyl acetate copolymer (EVA), acrylonitrile-butadiene rubber (NBR), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl butyral (PVB), ethylene-vinyl alcohol copolymer (EVOH), polyimide resin, polyphenylene sulfide (PPS), polyetherimide (PEI), polyetheretherimide (PEEI), polyetheretherketone (PEEK), melamine resin, phenol resin, acrylonitrile-butadiene-styrene (ABS) resin, natural materials such as natural rubber, or semi-synthetic materials of the above synthetic resin materials and natural materials. These may be commercialized into required shapes and configurations such as films, sheets, fiber materials, fiber products, other molded products, laminates, etc.

[0074] Examples of inorganic materials include non-metallic inorganic materials and metallic inorganic materials. Examples of non-metallic inorganic materials include glass, ceramics, stone materials, etc. These may be commercialized into various forms such as tiles, glass, mirrors, walls, decorative materials, etc. Examples of metallic inorganic materials include cast iron, steel materials, iron, iron alloys, aluminum, aluminum alloys, nickel, nickel alloys, zinc die-castings, etc. These may be plated with the above metallic inorganic materials, coated with the above organic materials, or plated on the surface of the above organic materials or non-metallic inorganic materials.

[0075] The titanium oxide particle dispersion of the present invention is particularly useful for forming a photocatalytic thin film by applying it to various members made of inorganic substances such as glass and metal, and organic substances such as resin, and is particularly useful for forming a transparent photocatalytic thin film on various members.

[0076] As a method for forming a photocatalytic thin film on the surface of various members, a titanium oxide particle dispersion liquid is applied to the surface of the above members by a known coating method such as spray coating or dip coating, and then dried by a known drying method such as far-infrared drying, IH drying, or hot air drying. The thickness of the photocatalytic thin film can also be selected variously, but usually, a range of 10 nm to 10 μm is preferable. Thereby, the coating film of the titanium oxide particles described above is formed. In this case, when the binder is contained in the above dispersion liquid in the above-described amount, a coating film containing titanium oxide particles and the binder is formed.

[0077] The photocatalytic thin film formed in this way is transparent, and not only gives a good photocatalytic action in the ultraviolet region light (wavelength 10 - 400 nm) as in the prior art, but also a more excellent photocatalytic action can be obtained even in the visible region light (wavelength 400 - 800 nm) where a sufficient photocatalytic action could not be obtained with the conventional photocatalysts. Various members on which the photocatalytic thin film is formed can exhibit effects such as cleaning, deodorizing, and antibacterial of the member surface because the organic substances adsorbed on the surface are decomposed more rapidly by the photocatalytic action of titanium oxide.

Example

[0078] Examples and comparative examples are shown below to specifically explain the present invention, but the present invention is not limited to the following examples. Various measurements in the present invention were performed as follows.

[0079] (1) 50% and 90% cumulative distribution diameters (D 50 and D 90 ) The D 50 and D 90 of the titanium oxide particles in the dispersion liquid were calculated as volume-based 50% and 90% cumulative distribution diameters measured by the dynamic light scattering method using laser light with a particle size distribution measuring device (ELSZ - 2000ZS (manufactured by Otsuka Electronics Co., Ltd.)).

[0080] (2) Acetaldehyde gas decomposition performance test of the photocatalytic thin film The activity of the photocatalytic thin film prepared by applying and drying the dispersion was evaluated by the decomposition reaction of acetaldehyde gas. The evaluation was carried out by a batch-type gas decomposition performance evaluation method. Each titanium oxide particle dispersion prepared in the examples or comparative examples was spread on one side of a PET film of A4 size (210 mm × 297 mm) with a wire bar coater of #7 so that the dry mass of titanium oxide particles became about 20 mg to prepare an evaluation sample, and it was dried in an oven set at 80 °C for 1 hour to obtain a sample for evaluating the acetaldehyde gas decomposition performance. Using this evaluation sample, the photocatalytic activity of the titanium oxide particles was evaluated by the decomposition reaction of acetaldehyde gas. The evaluation was carried out by a batch-type gas decomposition performance evaluation method. Specifically, after installing the evaluation sample in a stainless steel cell with a quartz glass window having a volume of 5 L, the cell was filled with acetaldehyde gas at an initial concentration adjusted to a humidity of 50%, and irradiated with light using a light source installed at the upper part of the cell. When the acetaldehyde gas is decomposed by the photocatalytic action of titanium oxide, the concentration of acetaldehyde gas in the cell decreases. Therefore, the strength of the photocatalytic activity can be confirmed by measuring the concentration change. The acetaldehyde gas concentration was measured using a photoacoustic multi-gas monitor (product name “INNOVA1412”, manufactured by LumaSense), and the photocatalytic activity was evaluated by measuring the time from the start of light irradiation until the acetaldehyde gas concentration became 1 ppm or less. The shorter the time, the higher the photocatalytic activity, and the longer the time, the lower the photocatalytic activity.

[0081] In the evaluation of photocatalytic activity under visible light irradiation, an LED (product model number “TH-211×200SW”, CCS Inc., spectral distribution: 400~800 nm) was used as the light source, and visible light was irradiated under the condition of an illuminance of 10,000 Lx. At this time, the initial concentration of acetaldehyde in the cell was set to 5 ppm. In addition, in the evaluation of photocatalytic activity under ultraviolet irradiation, a UV fluorescent lamp (product model number “FL10 BLB”, Toshiba Lighting & Technology Corporation) was used as the light source, and the irradiance was 0.2 mW / cm 2Under the conditions of , ultraviolet rays (352 nm) were irradiated. At this time, the initial concentration of acetaldehyde in the cell was set to 20 ppm.

[0082] (3) Identification of the crystal phase of titanium oxide particles The crystal phase of the titanium oxide particles was identified by measuring the powder X-ray diffraction (trade name "Desktop X-ray Diffractometer D2 PHASER", Bruker AXS K.K.) of the titanium oxide particle powder recovered by drying the obtained dispersion of titanium oxide particles at 105 °C for 3 hours.

[0083] (4) Preparation of titanium oxide particle dispersion [Preparation Example 1-1] [Preparation of a Dispersion of Titanium Oxide Particles in which Tin and Molybdenum are Solid-Solved] Tin(IV) chloride was added and dissolved in a 36 mass% aqueous solution of titanium(IV) chloride so that the TiO2 / Sn (molar ratio) in the titanium oxide particle dispersion obtained in Preparation Example 1-1 was 20, and this was diluted 10-fold with pure water. Then, 10 mass% aqueous ammonia was gradually added for neutralization and hydrolysis to obtain a precipitate of titanium hydroxide containing tin. The pH at this time was 8. The obtained precipitate was subjected to deionization treatment by repeating the addition of pure water and decantation. Sodium molybdate(VI) was added to the titanium hydroxide precipitate containing tin after this deionization treatment so that the TiO2 / Mo (molar ratio) in the titanium oxide particle dispersion obtained in Preparation Example 1-1 was 400. 35 mass% aqueous hydrogen peroxide solution was added so that the H2O2 / (Ti + Sn + Mo) (molar ratio) was 10, and then it was stirred at 60 °C for 2 hours for sufficient reaction to obtain an orange transparent peroxotitanic acid solution (1a) containing tin and molybdenum. A 500 mL autoclave was charged with 400 mL of a peroxotitanic acid solution (1a) containing tin and molybdenum. This was hydrothermally treated at 150 °C for 90 minutes, and then pure water was added for concentration adjustment to obtain a dispersion (titanium oxide concentration 1.2 mass%) of titanium oxide particles (1A) in which tin and molybdenum were solid-dissolved. When powder X-ray diffraction measurement of the titanium oxide particles (1A) was performed, the observed peaks were only those of rutile-type titanium oxide, indicating that tin and molybdenum were solid-dissolved in titanium oxide.

[0084] [Preparation Example 1-2] [Preparation of Titanium Oxide Particle Dispersion in which Tin and Tungsten are Solid-Dissolved] Tin(IV) chloride was added and dissolved in a 36 mass% aqueous solution of titanium(IV) chloride so that the TiO2 / Sn (molar ratio) was 10 in the titanium oxide particle dispersion obtained in Preparation Example 1-2. After diluting this 10-fold with pure water, 10 mass% aqueous ammonia was gradually added for neutralization and hydrolysis to obtain a precipitate of titanium hydroxide containing tin. The pH at this time was 8. The obtained precipitate was subjected to deionization treatment by repeating the addition of pure water and decantation. Sodium tungstate(VI) was added to the titanium hydroxide precipitate containing tin after this deionization treatment so that the TiO2 / W (molar ratio) was 100 in the titanium oxide particle dispersion obtained in Preparation Example 1-2. 35 mass% hydrogen peroxide solution was added so that the H2O2 / (Ti + Sn + W) (molar ratio) was 10, and then the mixture was stirred at 60 °C for 2 hours for sufficient reaction to obtain an orange transparent peroxotitanic acid solution (1b) containing tin and tungsten. A 500 mL autoclave was charged with 400 mL of a peroxotitanic acid solution (1b) containing tin and tungsten, and this was hydrothermally treated at 160 °C for 60 minutes. Then, pure water was added to adjust the concentration, and a dispersion (titanium oxide concentration: 1.2 mass%) of titanium oxide particles (1B) in which tin and tungsten were solid-dissolved was obtained. When powder X-ray diffraction measurement was performed on the titanium oxide particles (1B), the observed peaks were only those of rutile-type titanium oxide, indicating that tin and tungsten were solid-dissolved in titanium oxide.

[0085] [Preparation Example 1-3] <Preparation of Titanium Oxide Particle Dispersion in which Tin and Vanadium are Solid-Dissolved> Tin(IV) chloride was added and dissolved in a 36 mass% aqueous solution of titanium(IV) chloride so that the TiO2 / Sn (molar ratio) was 33 in the titanium oxide particle dispersion obtained in Preparation Example 1-3, and after diluting this 10-fold with pure water, 10 mass% aqueous ammonia was gradually added for neutralization and hydrolysis to obtain a precipitate of titanium hydroxide containing tin. The pH at this time was 8. The obtained precipitate was subjected to deionization treatment by repeating the addition of pure water and decantation. Sodium vanadate(V) was added to the titanium hydroxide precipitate containing tin after this deionization treatment so that the TiO2 / V (molar ratio) was 2,000 in the titanium oxide particle dispersion obtained in Preparation Example 1-3. 35 mass% hydrogen peroxide solution was added so that the H2O2 / (Ti+Sn+V) (molar ratio) was 10, and then it was stirred at 50 °C for 3 hours for sufficient reaction to obtain an orange transparent peroxotitanic acid solution (1c) containing tin and vanadium. A 500 mL autoclave was charged with 400 mL of a peroxotitanic acid solution (1c) containing tin and vanadium. This was subjected to hydrothermal treatment at 140 °C for 120 minutes, and then pure water was added for concentration adjustment to obtain a dispersion (titanium oxide concentration 1.2 mass%) of titanium oxide particles (1C) in which tin and vanadium were solid-dissolved. When powder X-ray diffraction measurement of the titanium oxide particles (1C) was performed, the observed peaks were those of anatase-type titanium oxide and rutile-type titanium oxide, indicating that tin and vanadium were solid-dissolved in titanium oxide.

[0086] [Preparation Example 1-4] [Preparation of Dispersion of Titanium Oxide Particles with Solid-Dissolved Tin and Molybdenum] Tin(IV) chloride was added and dissolved in a 36 mass% aqueous solution of titanium(IV) chloride so that the TiO2 / Sn (molar ratio) was 20 in the titanium oxide particle dispersion obtained in Preparation Example 1-4. After diluting this 10-fold with pure water, 10 mass% aqueous ammonia was gradually added for neutralization and hydrolysis to obtain a precipitate of titanium hydroxide containing tin. The pH at this time was 8. The obtained precipitate was subjected to deionization treatment by repeating the addition of pure water and decantation. Sodium molybdate(VI) was added to the titanium hydroxide precipitate containing tin after this deionization treatment so that the TiO2 / Mo (molar ratio) was 100 in the titanium oxide particle dispersion obtained in Preparation Example 1-4. 35 mass% hydrogen peroxide solution was added so that the H2O2 / (Ti + Sn + Mo) (molar ratio) was 12, and then it was stirred at 60 °C for 2 hours for sufficient reaction to obtain an orange transparent peroxotitanic acid solution (1d) containing tin and molybdenum. A 500 mL autoclave was charged with 400 mL of a peroxotitanic acid solution (1d) containing tin and molybdenum. This was hydrothermally treated at 120 °C for 180 minutes, and then pure water was added for concentration adjustment to obtain a dispersion of titanium oxide particles (1D) in which tin and molybdenum were solid-dissolved (titanium oxide concentration: 1.2 mass%). When powder X-ray diffraction measurement was performed on the titanium oxide particles (1D), the observed peaks were only those of rutile-type titanium oxide, indicating that tin and molybdenum were solid-dissolved in titanium oxide.

[0087] [Preparation Example 1-5] <Preparation of Titanium Oxide Particle Dispersion in which Tin, Tungsten, and Vanadium are Solid-Dissolved> To an aqueous solution of titanium(IV) chloride at 36 mass%, tin(IV) chloride was added and dissolved so that the TiO2 / Sn (molar ratio) was 50 in the titanium oxide particle dispersion obtained in Preparation Example 1-5. After diluting this 10-fold with pure water, 10 mass% aqueous ammonia was gradually added for neutralization and hydrolysis to obtain a precipitate of titanium hydroxide containing tin. The pH at this time was 8. The obtained precipitate was subjected to deionization treatment by repeating the addition of pure water and decantation. To the titanium hydroxide precipitate containing tin after this deionization treatment, sodium tungstate(VI) was added so that the TiO2 / W (molar ratio) was 33 in the titanium oxide particle dispersion obtained in Preparation Example 1-5, and sodium vanadate(V) was added so that the TiO2 / V (molar ratio) was 5,000. 35 mass% hydrogen peroxide solution was added so that the H2O2 / (Ti + Sn + W + V) (molar ratio) was 10, and then it was stirred at 60 °C for 2 hours for sufficient reaction to obtain an orange transparent peroxotitanic acid solution (1e) containing tin 、 tungsten and vanadium ​400 mL of a peroxotitanic acid solution (1e) containing tin, tungsten, and vanadium was charged into an autoclave with a volume of 500 mL, and this was hydrothermally treated at 140 °C for 120 minutes. Then, pure water was added for concentration adjustment to obtain a dispersion (titanium oxide concentration: 1.2% by mass) of titanium oxide particles (1E) in which tin, tungsten, and vanadium were solid-dissolved. When powder X-ray diffraction measurement was performed on the titanium oxide particles (1E), the observed peaks were those of anatase-type titanium oxide and rutile-type titanium oxide, and it was found that tin, tungsten, and vanadium were solid-dissolved in titanium oxide.

[0088] [Preparation Example 1-6] <Preparation of Titanium Oxide Particle Dispersion with Tin Solid-Dissolved> A dispersion (titanium oxide concentration: 1.2% by mass) of titanium oxide particles (1F) in which tin was solid-dissolved was obtained in the same manner as in Preparation Example 1-1, except that sodium molybdate (VI) was not added. When powder X-ray diffraction measurement was performed on the titanium oxide particles (1F), the observed peaks were only those of rutile-type titanium oxide, and it was found that tin was solid-dissolved in titanium oxide.

[0089] [Preparation Example 1-7] <Preparation of Titanium Oxide Particle Dispersion with Molybdenum Solid-Dissolved> A dispersion (titanium oxide concentration: 1.2% by mass) of titanium oxide particles (1G) in which molybdenum was solid-dissolved was obtained in the same manner as in Preparation Example 1-1, except that tin(IV) chloride was not added. When powder X-ray diffraction measurement was performed on the titanium oxide particles (1G), the observed peaks were only those of anatase-type titanium oxide, and it was found that molybdenum was solid-dissolved in titanium oxide.

[0090] [Preparation Example 1-8] <Preparation of Titanium Oxide Particle Dispersion with Tungsten Solid-Dissolved> A dispersion (titanium oxide concentration: 1.2% by mass) of titanium oxide particles (1H) in which tungsten was dissolved was obtained in the same manner as in Preparation Example 1-2, except that tin(IV) chloride was not added. Powder X-ray diffraction measurement of the titanium oxide particles (1H) revealed that the observed peaks were only those of anatase-type titanium oxide, indicating that tungsten was dissolved in the titanium oxide.

[0091] [Preparation Example 1-9] <Preparation of Dispersion of Titanium Oxide Particles in which Vanadium was Dissolved> A dispersion (titanium oxide concentration: 1.2% by mass) of titanium oxide particles (1I) in which vanadium was dissolved was obtained in the same manner as in Preparation Example 1-3, except that tin(IV) chloride was not added. Powder X-ray diffraction measurement of the titanium oxide particles (1I) revealed that the observed peaks were only those of anatase-type titanium oxide, indicating that vanadium was dissolved in the titanium oxide.

[0092] Table 1 summarizes the molar ratios of the titanium oxide particles prepared in each preparation example, the hydrothermal treatment conditions, the dispersed particle diameters (D 50 、D 90 ), and the pH of the titanium oxide particle dispersion after the hydrothermal treatment. The dispersed particle diameter was measured by the dynamic light scattering method using a laser beam (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

[0093]

Table 1

[0094] (5) Preparation of Solution or Dispersion of Iron Component, Titanium Component, and Silicon Component [Preparation Example 2-1] <Preparation of Aqueous Solution of Iron Sulfate, Titanium Chloride, and Activated Silicic Acid> To 100 g of pure water, 0.34 g of JIS No. 3 sodium silicate (29.1% by mass in terms of SiO₂) was dissolved to obtain an aqueous sodium silicate solution. A strongly acidic cation exchange resin (Amberjet 1024H, manufactured by Organo Corporation) was added thereto and stirred, and then the ion exchange resin was filtered off to obtain an aqueous solution of active silicic acid. To this aqueous solution of active silicic acid, 0.13 g of ferric sulfate (III) and 0.12 g of titanium (IV) chloride were added to obtain an aqueous solution (2A) of ferric sulfate, titanium chloride, and active silicic acid having a pH of 1.8.

[0095] [Preparation Example 2-2] <Preparation of Aqueous Solution of Ferric Sulfate, Titanium Chloride, and Active Silicic Acid> To 100 g of pure water, 3.43 g of JIS No. 3 sodium silicate (29.1% in terms of SiO₂) was dissolved to obtain an aqueous sodium silicate solution. A strongly acidic cation exchange resin (Amberjet 1024H, manufactured by Organo Corporation) was added thereto and stirred, and then the ion exchange resin was filtered off to obtain an aqueous solution of active silicic acid. To this aqueous solution of active silicic acid, 0.38 g of ferric sulfate (III) and 0.02 g of titanium (IV) chloride were added to obtain an aqueous solution (2B) of ferric sulfate, titanium chloride, and active silicic acid having a pH of 2.2.

[0096] [Preparation Example 2-3] <Preparation of Aqueous Solution of Ferric Sulfate, Titanium Chloride, and Active Silicic Acid> To 100 g of pure water, 0.17 g of JIS No. 3 sodium silicate (29.1% in terms of SiO₂) was dissolved to obtain an aqueous sodium silicate solution. A strongly acidic cation exchange resin (Amberjet 1024H, manufactured by Organo Corporation) was added thereto and stirred, and then the ion exchange resin was filtered off to obtain an aqueous solution of active silicic acid. To this aqueous solution of active silicic acid, 0.06 g of ferric sulfate (III) and 0.06 g of titanium (IV) chloride were added to obtain an aqueous solution (2C) of ferric sulfate, titanium chloride, and active silicic acid having a pH of 2.2.

[0097] [Preparation Example 2-4] <Preparation of Aqueous Solution of Ferric Sulfate and Active Silicic Acid> An aqueous solution (2D) of ferric sulfate and active silicic acid having a pH of 2.6 was obtained in the same manner as in Preparation Example 2-3 except that titanium (IV) chloride was not added.

[0098] [Preparation Example 2-5] [Preparation of Aqueous Solution of Titanium Chloride and Activated Silicic Acid] An aqueous solution (2E) of titanium chloride and activated silicic acid with a pH of 2.2 was obtained in the same manner as in Preparation Example 2-3, except that iron(III) sulfate was not added.

[0099] [Preparation Example 2-6] [Preparation of Aqueous Solution of Iron Sulfate] An aqueous solution (2F) of iron sulfate with a pH of 2.5 was obtained in the same manner as in Preparation Example 2-2, except that sodium silicate No. 3 according to JIS and titanium(IV) chloride were not added.

[0100] [Preparation Example 2-7] [Preparation of Aqueous Solution of Titanium Chloride] An aqueous solution (2G) of titanium chloride with a pH of 1.8 was obtained in the same manner as in Preparation Example 2-1, except that sodium silicate No. 3 according to JIS and iron(III) sulfate were not added.

[0101] [Preparation Example 2-8] [Preparation of Aqueous Solution of Activated Silicic Acid] An aqueous solution (2H) of activated silicic acid with a pH of 4.8 was obtained in the same manner as in Preparation Example 2-1, except that iron sulfate and titanium chloride were not added.

[0102] (6) Preparation of Titanium Oxide Particle Dispersion [Example 1] An aqueous solution (2A) of iron sulfate, titanium chloride and activated silicic acid was mixed with a dispersion of titanium oxide particles (1A) at 25°C for 10 minutes with a stirrer so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. Then, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (E-1).

[0103] [Example 2] An aqueous solution (2B) of iron sulfate, titanium chloride and activated silicic acid was mixed with a dispersion of titanium oxide particles (1B) at 25°C for 10 minutes with a stirrer so that TiO2 / Fe was 133, TiO2 / Ti was 1,000, and TiO2 / Si was 8. Then, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (E-2).

[0104] [Example 3] An aqueous solution (2C) of iron sulfate, titanium chloride, and activated silica was added to a dispersion of titanium oxide particles (1C) and mixed with a stirrer at 25°C for 10 minutes so that TiO2 / Fe was 800, TiO2 / Ti was 400, and TiO2 / Si was 150. Then, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (E-3).

[0105] [Example 4] An aqueous solution (2A) of iron sulfate, titanium chloride, and activated silica was added to a dispersion of titanium oxide particles (1D) and mixed with a stirrer at 25°C for 10 minutes so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. Then, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (E-4).

[0106] [Example 5] An aqueous solution (2A) of iron sulfate, titanium chloride, and activated silica was added to a dispersion of titanium oxide particles (1E) and mixed with a stirrer at 25°C for 10 minutes so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. Then, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (E-5).

[0107] [Example 6] A silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added to the titanium oxide particle dispersion (E-4) so that TiO2 / SiO2 (mass ratio) was 1.5, and the mixture was stirred with a stirrer at 25°C for 10 minutes to obtain a titanium oxide particle dispersion (E-6) containing the binder.

[0108] [Comparative Example 1] An aqueous solution (2A) of iron sulfate, titanium chloride, and activated silica was added to a dispersion of titanium oxide particles (1F) and mixed with a stirrer at 25°C for 10 minutes so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. Then, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-1).

[0109] [Comparative Example 2] An aqueous solution (2A) of iron sulfate, titanium chloride, and activated silica was mixed with a dispersion of titanium oxide particles (1G) at 25°C for 10 minutes with a stirrer so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-2).

[0110] [Comparative Example 3] An aqueous solution (2A) of iron sulfate, titanium chloride, and activated silica was mixed with a dispersion of titanium oxide particles (1H) at 25°C for 10 minutes with a stirrer so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-3).

[0111] [Comparative Example 4] An aqueous solution (2A) of iron sulfate, titanium chloride, and activated silica was mixed with a dispersion of titanium oxide particles (1I) at 25°C for 10 minutes with a stirrer so that TiO2 / Fe was 400, TiO2 / Ti was 200, and TiO2 / Si was 75. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-4).

[0112] [Comparative Example 5] An aqueous solution (2D) of iron sulfate and activated silica was mixed with a dispersion of titanium oxide particles (1D) at 25°C for 10 minutes with a stirrer so that TiO2 / Fe was 800 and TiO2 / Si was 150. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-5).

[0113] [Comparative Example 6] An aqueous solution (2E) of titanium chloride and activated silica was mixed with a dispersion of titanium oxide particles (1D) at 25°C for 10 minutes with a stirrer so that TiO2 / Ti was 400 and TiO2 / Si was 150. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-6).

[0114] [Comparative Example 7] An aqueous solution of iron sulfate (2F) was mixed with a dispersion of titanium oxide particles (1D) at 25 °C for 10 minutes with a stirrer so that TiO2 / Fe was 133. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-7). Due to the addition of iron sulfate, the titanium oxide particles aggregated and some precipitated, and the appearance of the dispersion became turbid. Also, when the titanium oxide particle dispersion (C-7) was filtered through a PP filter with a pore size of 1 μm, a brown iron component was separated on the filter, indicating that the iron component was also aggregated. [Comparative Example 8] An aqueous solution of titanium chloride (2G) was mixed with a dispersion of titanium oxide particles (1D) at 25 °C for 10 minutes with a stirrer so that TiO2 / Ti was 200. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-8). Due to the addition of titanium chloride, the titanium oxide particles aggregated and some precipitated, and the appearance of the dispersion became turbid. Also, when the titanium oxide particle dispersion (C-8) was filtered through a PP filter with a pore size of 1 μm, a hydrated white component was separated on the filter, indicating that in addition to titanium oxide, the titanium component was also aggregated.

[0115] [Comparative Example 9] An aqueous solution of activated silica (2H) was mixed with a dispersion of titanium oxide particles (1D) at 25 °C for 10 minutes with a stirrer so that TiO2 / Si was 75. After that, the solid content concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-9).

[0116] [Comparative Example 10] The solid content concentration of a dispersion of titanium oxide particles (1D) was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (C-10).

[0117] [Comparative Example 11] To the titanium oxide particle dispersion (C-5), a silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added so that the TiO2 / SiO2 (mass ratio) became 1.5, and the mixture was stirred with a stirrer at 25°C for 10 minutes to obtain a titanium oxide particle dispersion (C-11) containing the binder.

[0118] [Comparative Example 12] To the titanium oxide particle dispersion (C-6), a silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added so that the TiO2 / SiO2 (mass ratio) became 1.5, and the mixture was stirred with a stirrer at 25°C for 10 minutes to obtain a titanium oxide particle dispersion (C-12) containing the binder.

[0119] (7) Preparation of sample member having photocatalytic thin film Each of the titanium oxide particle dispersions prepared in the above Examples or Comparative Examples was coated with a #7 wire bar coater onto an A4-sized PET film so as to form a photocatalytic thin film (thickness of about 80 nm) containing 20 mg of titanium oxide particles, and dried in an oven set at 80°C for 1 hour to obtain a sample member for evaluating the acetaldehyde gas decomposition performance.

[0120] [Photocatalytic performance test under visible light irradiation] An acetaldehyde decomposition test was conducted on the sample members having the photocatalytic thin films of the Examples and Comparative Examples under visible light irradiation by an LED. Evaluation was based on the time required to reduce the initial concentration of acetaldehyde from 5 ppm to 1 ppm. In addition, when the concentration did not reduce to 1 ppm within 24 hours, in Tables 2 and 3, in the column of "time required to decompose to 1 ppm", "-" was indicated, and in the column of "concentration after 24 hours", the concentration after 24 hours was indicated.

[0121] Table 2 shows the types of titanium oxide particles and added metal components in Examples 1 to 5 and Comparative Examples 1 to 10, the molar ratio of the metal in the added metal component to titanium oxide (TiO2), the dispersed particle diameter (D 50 、D90 ) The results of the acetaldehyde gas decomposition test under pH and visible light irradiation are summarized. The dispersed particle size was measured by the dynamic light scattering method using a laser beam (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

[0122]

Table 2

[0123] As can be seen from the results of Examples 1 to 5 and Comparative Examples 1 to 4, by using titanium oxide particles in which both the tin component and the transition metal component that enhances visible light activity are solid-dissolved, the photocatalytic activity under visible light irradiation is higher than when using titanium oxide in which either one or both of the tin component and the transition metal component that enhances visible light activity are not solid-dissolved.

[0124] As can be seen from the results of Example 4 and Comparative Examples 5, 6, 9, and 10, photocatalytic titanium oxide with iron, titanium, and silicon components (2A) attached to the surface of titanium oxide particles (1D) has higher photocatalytic activity under visible light irradiation than photocatalytic titanium oxide with iron and silicon components (2D), titanium and silicon components (2E), silicon component (2H) attached, and photocatalytic titanium oxide with nothing attached.

[0125] As can be seen from the results of Example 4 and Comparative Examples 7 and 8, when adding iron and titanium components to titanium oxide particles (1D), it was found that adding silicon components together can suppress the aggregation and precipitation of titanium oxide particles, iron components, and titanium components.

[0126] From the above, it was confirmed that the photocatalytic performance of titanium oxide particles with iron, titanium, and silicon components attached to the surface of the present invention and in which the tin component and the transition metal component that enhances visible light activity are solid-dissolved is excellent.

[0127] [Photocatalytic Performance Test under UV Irradiation] For the sample members having the photocatalytic thin films of Example 6 and Comparative Examples 11 and 12, an acetaldehyde decomposition test was conducted under irradiation with a UV fluorescent lamp. Evaluation was made based on the time required to reduce the initial concentration of acetaldehyde from 20 ppm to 1 ppm.

[0128] Table 3 shows the types of titanium oxide particles and added metals, the molar ratio of the metal in the added metal component to titanium oxide (TiO2), the dispersed particle size (D 50 , D 90 ), pH, and the results of the acetaldehyde gas decomposition test. The dispersed particle size was measured by the dynamic light scattering method using a laser beam (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

[0129]

Table 3

[0130] Similarly, from the results of Example 6 and Comparative Examples 11 and 12, it was found that for the photocatalytic thin film containing a binder and even under UV irradiation, the photocatalytic titanium oxide obtained by adding a solution (2A) containing an iron component, a titanium component, and a silicon component to titanium oxide particles (1D) has higher activity than the photocatalytic titanium oxide obtained by adding a solution (2D) containing an iron component and a silicon component or a solution (2E) containing a titanium component and a silicon component.

[0131] The titanium oxide particle dispersion of the present invention is useful for producing a photocatalytic thin film by applying it to various members made of inorganic substances such as glass and metal, and organic substances such as resin, and is particularly useful for producing a transparent photocatalytic thin film on various members.

Claims

1. 1) It contains a tin component and at least one transition metal component selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium that enhances visible light activity in solid solution, 2) Titanium oxide particles that do not contain iron and silicon components in solid solution and have iron, titanium, and silicon components adhering to their surfaces, where the molar ratio of the iron component to titanium oxide (TiO 2 / Fe) is 50 to 2,000, the molar ratio of the titanium component to titanium oxide (TiO 2 / Ti) is 50 to 2,000, and the molar ratio of the silicon component to titanium oxide (TiO 2 / Si) is 5 to 2,000, Titanium oxide particles having a volume-based 50% cumulative distribution diameter D50 of 3 to 50 nm and a volume-based 90% cumulative distribution diameter D90 of 5 to 100 nm as measured by the dynamic light scattering method using laser light in the dispersion of the titanium oxide particles.

2. The titanium oxide particles according to claim 1, wherein the transition metal component that enhances visible light activity and is dissolved in the titanium oxide particles is at least one selected from molybdenum, tungsten, and vanadium components.

3. The content of the tin component dissolved in the titanium oxide particles is 1 to 1,000 in terms of the molar ratio to titanium oxide (TiO 2 / Sn). The titanium oxide particles according to claim 1 or 2.

4. The amount of each of the molybdenum, tungsten, and vanadium components dissolved in the titanium oxide particles is 1 to 10,000 in terms of the molar ratio to titanium oxide (TiO 2 / Mo, TiO 2 / W or TiO 2 / V). The titanium oxide particles according to claim 2.

5. A titanium oxide particle dispersion in which the titanium oxide particles according to any one of claims 1 to 4 are dispersed in an aqueous dispersion medium and the pH is 7 to 14.

6. Furthermore, the titanium oxide particle dispersion according to claim 5, which contains a binder.

7. The titanium oxide particle dispersion according to claim 6, wherein the binder is a silicon compound-based binder.

8. A photocatalytic thin film containing the titanium oxide particles according to any one of claims 1 to 4.

9. Furthermore, the photocatalytic thin film according to claim 8, which contains a binder.

10. A member having the photocatalytic thin film according to claim 8 or 9 on its surface.

11. A method for producing the titanium oxide particle dispersion according to any one of claims 5 to 7, which comprises the following steps (1) to (4). (1) A step of producing a peroxotitanic acid solution containing a tin component and at least one transition metal component selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium from a raw material titanium compound, a tin compound, at least one transition metal compound selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium, a basic substance, hydrogen peroxide, and an aqueous dispersion medium (2) A step of heating the peroxotitanic acid solution containing a tin component and at least one transition metal component selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium, produced in the step (1) above, at 80 to 250 ° C under pressure control to obtain a titanium oxide particle dispersion containing a tin component and at least one transition metal component selected from vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium (3) A step of producing a solution or dispersion of an iron component, a titanium component, and a silicon component from an iron compound, a titanium compound, a silicon compound, and an aqueous dispersion medium (4) A step of mixing the titanium oxide particle dispersion produced in the step (2) above with the solution or dispersion of the iron compound, titanium compound, and silicon compound produced in the step (3) to obtain a dispersion

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