Titanium oxide particle composition, photocatalytic film, member having photocatalytic film on its surface

Abstract

Providing a titanium oxide particle composition or the like that can obtain a photocatalytic activity higher than ever before. 【Solution means】 i) Titanium oxide particles, ii) Titanium oxide particles in which copper and / or iron is dissolved, A titanium oxide particle composition containing two types of titanium oxide particles, i) The titanium oxide particles have a volume-based 50% cumulative distribution diameter D 50 measured by the dynamic light scattering method using laser light in an aqueous dispersion medium of 30 to 500 nm, and a 90% cumulative distribution diameter D 90 of 50 to 800 nm, ii) The titanium oxide particles in which copper and / or iron is dissolved have a volume-based 50% cumulative distribution diameter D 50 measured by the dynamic light scattering method using laser light in an aqueous dispersion medium of 5 to 30 nm, and a 90% cumulative distribution diameter D 90 of 10 to 50 nm, A titanium oxide particle composition in which the mass ratio (i-TiO2 / ii-TiO2) of the two types of titanium oxide particles is 99 to 1.0.

Description

[Technical Field]

[0001] The present invention relates to a titanium dioxide particle composition, a photocatalytic film containing the composition, and a component having the photocatalytic film on its surface, and more particularly to a titanium dioxide particle dispersion that can easily produce a photocatalytic film with high photocatalytic activity. [Background technology]

[0002] Photocatalysts are widely used for applications such as cleaning, deodorizing, and antibacterial treatment of substrate surfaces. A photocatalytic reaction is a reaction caused by excited electrons and holes generated when a photocatalyst absorbs light. The decomposition of organic matter by photocatalysts is thought to occur mainly through the following mechanisms [1] and [2].

[0003] [1] The generated excited electrons and holes undergo an oxidation-reduction reaction with oxygen and water adsorbed on the photocatalyst surface, and the active species generated by this oxidation-reduction reaction decompose organic matter. [2] The generated holes directly oxidize and decompose organic matter adsorbed on the photocatalyst surface.

[0004] In recent years, the development of photocatalytic air purification devices utilizing the photocatalytic action described above has been progressing in various places, and they are particularly promising as a technology for decomposing and removing low concentrations of volatile organic compounds (VOCs), which are considered to be the cause of sick building syndrome and chemical sensitivity.

[0005] To improve the performance of such photocatalytic air purification devices, efforts are being made to improve the shape and material of the photocatalytic filter and the photocatalytic unit into which it is incorporated, as well as to further enhance the volatile organic compound decomposition performance of the photocatalyst.

[0006] For example, a method of using a photocatalyst and a cocatalyst together (Japanese Patent Application Laid-Open No. 2023-068678: Patent Document 1, International Publication No. 2022 / 190901: Patent Document 2), a method of using a photocatalyst and an adsorbent together (Japanese Patent Application Laid-Open No. 2017-023163: Patent Document 3, Japanese Patent Application Laid-Open No. 2016-221447: Patent Document 4, Japanese Patent Application Laid-Open No. 2000-37614: Patent Document 5), etc. are known.

[0007] As described above, although studies have been actively conducted to improve the performance of photocatalytic air purifying devices, in the actual environment, it is important that volatile organic compounds are decomposed and removed as quickly as possible. Therefore, further improvement in the volatile organic compound decomposition performance of photocatalysts is desired.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to provide a titanium oxide particle composition capable of obtaining higher photocatalytic activity (volatile organic compound decomposition performance) than before, a photocatalytic film containing the composition, and a member having the photocatalytic film on its surface.

Means for Solving the Problems

[0010] In order to achieve the above object, the inventors of the present invention have carefully studied the type of titanium oxide particles, the dispersed particle diameter (cumulative distribution diameter), the combination with various materials, and the quantitative ratio thereof. As a result, it has been found that the photocatalytic activity is dramatically improved by using a mixture of titanium oxide particles obtained by mixing titanium oxide in which copper and / or iron is dissolved in titanium oxide particles having a dispersed particle diameter within a specific range, and the present invention has been completed.

[0011] Therefore, the present invention provides a titanium oxide particle composition shown below, a photocatalytic film containing the composition, and a member having the photocatalytic film on the surface. 〔1〕 i) titanium oxide particles; and ii) titanium oxide particles in which copper and / or iron is dissolved, The titanium oxide particle composition contains two types of titanium oxide particles, i) The titanium oxide particles have a volume-based 50% cumulative distribution diameter D 50 measured by a dynamic light scattering method using laser light in an aqueous dispersion medium of 30 to 500 nm, and a 90% cumulative distribution diameter D 90 of 50 to 800 nm, ii) The titanium oxide particles in which copper and / or iron is dissolved have a volume-based 50% cumulative distribution diameter D 50 measured by a dynamic light scattering method using laser light in an aqueous dispersion medium of 5 to 30 nm, and a 90% cumulative distribution diameter D 90 of 10 to 50 nm, The mass ratio (i-TiO2 / ii-TiO2) of i) titanium oxide particles to ii) titanium oxide particles in which copper and / or iron is dissolved is 99 to 1.0. 〔2〕 The volume-based 50% cumulative distribution diameter D 50 measured by a dynamic light scattering method using laser light in an aqueous dispersion medium of a mixture of two types of titanium oxide particles of i) titanium oxide particles and ii) titanium oxide particles in which copper and / or iron is dissolved is 50 to 500 nm, and the 90% cumulative distribution diameter D 90 is 80 to 800 nm. The titanium oxide particle composition according to 〔1〕. 〔3〕 ii) The titanium oxide particle composition according to [1] or [2], wherein the content of copper or iron dissolved in the titanium oxide particles is 1 to 100 in molar ratio (Ti / Cu or Fe) with titanium in the titanium oxide. [4] Furthermore, a titanium dioxide particle composition according to any one of [1] to [3], which contains a binder. [5] The titanium oxide particle composition according to [4], wherein the binder is a silicon compound-based binder. [6] A photocatalytic film containing the titanium dioxide particle composition described in any of [1] to [5]. [7] Furthermore, the titanium dioxide particle composition according to any one of [1] to [5] is a dispersion liquid containing an aqueous dispersion medium, wherein titanium dioxide particles are dispersed in the aqueous dispersion medium. [8] A component having the photocatalytic film described in [6] on its surface. [Effects of the Invention]

[0012] The titanium dioxide particle composition of the present invention has higher photocatalytic activity than conventional compositions. Therefore, the titanium dioxide particle composition of the present invention is useful for components such as photocatalytic filters where rapid decomposition and removal of harmful volatile organic compounds are required. [Modes for carrying out the invention]

[0013] The present invention will be described in detail below. <Titanium dioxide particle composition> The titanium oxide particle composition of the present invention contains titanium oxide particles i) and titanium oxide particles ii), which have different compositions and dispersion particle diameters (cumulative distribution diameters). The titanium oxide particles i) are titanium oxide particles in which neither copper nor iron is solid-dissolved, and are not particularly limited as long as neither copper nor iron is solid-dissolved, and titanium oxide particles used as photocatalysts can be used, and the titanium oxide particles ii) are titanium oxide particles in which copper and / or iron are solid-dissolved.

[0014] In this specification, a solid solution refers to a phase in which an atom at a lattice point of one crystalline phase is replaced by another atom, or another atom enters the interstitial space, that is, a mixed phase in which another substance is considered to be dissolved in a crystalline phase, and which is a homogeneous crystalline phase. A solid solution in which solvent atoms at lattice points are replaced by solute atoms is called a substitutional solid solution, and a solid solution in which solute atoms enter the interstitial space is called an interstitial solid solution, but in this specification, both of these will be used.

[0015] In the titanium oxide particles of the present invention, the titanium oxide particles of ii) are characterized in that they form a solid solution with copper atoms and / or iron atoms. The solid solution may be substitutional or interstitial. A substitutional solid solution of titanium oxide is formed when the titanium sites of the titanium oxide crystal are replaced by various metal atoms, while an interstitial solid solution of titanium oxide is formed when various metal atoms enter the interstitial spaces of the titanium oxide crystal. When various metal atoms are dissolved in titanium oxide, when the crystal phase is measured by X-ray diffraction or the like, only the peak of the titanium oxide crystal phase is observed, and the peaks of compounds derived from the added metal atoms are not observed.

[0016] There are no particular limitations on the method for solid-solving dissimilar metals into metal oxide crystals, but examples include gas-phase methods (CVD, PVD, etc.), liquid-phase methods (hydrothermal methods, sol-gel methods, etc.), and solid-phase methods (high-temperature firing methods, etc.).

[0017] While three crystalline phases are generally known for titanium dioxide particles—anatase, rutile, and brookite—the titanium dioxide particles described in i) and ii) above are preferably mainly of the anatase or rutile type, and particularly preferably of the anatase type. Here, "mainly" means that the titanium dioxide particles of the crystalline phase make up 50% by mass or more of the total titanium dioxide particles, preferably 70% by mass or more, more preferably 90% by mass or more, and may even be 100% by mass.

[0018] In this specification, the volume-based 50% cumulative distribution diameter measured by the dynamic light scattering method using laser light is denoted as "D 50 ", and the volume-based 90% cumulative distribution diameter measured by the dynamic light scattering method using laser light may be denoted as "D 90 ". As an apparatus for measuring D 50 and D 90 of titanium oxide particles, for example, ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.), Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.), LA-910 (manufactured by Horiba, Ltd.) and the like can be used.

[0019] In this specification, as the aqueous dispersion medium, it is preferable to use water, but a mixed solvent of a hydrophilic organic solvent mixed with water at an arbitrary ratio and water may also be used. As the water, for example, purified water such as filtered water, deionized water, distilled water, pure water and the like is preferable. As the hydrophilic organic solvent, for example, alcohols such as methanol, ethanol, isopropanol and the like, glycols such as ethylene glycol and the like, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol-n-propyl ether and the like 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, still more preferably 10% by mass or less.

[0020] <i) titanium oxide particles> The titanium oxide particles of i) are not particularly limited as long as neither copper nor iron is solid-dissolved, and titanium oxide particles used as a photocatalyst can be used. The titanium oxide particles of i) may be used singly or in combination of two or more. When two or more kinds having different light absorption characteristics are combined as the titanium oxide particles of i), an effect of enhancing the photocatalytic activity may be obtained.

[0021] The titanium oxide particles of i) have D 50However, the wavelength is 30-500 nm, preferably 50-400 nm, and more preferably 50-300 nm. 50 However, if the wavelength is less than 30 nm, the photocatalytic activity may be insufficient, and if it exceeds 500 nm, the titanium dioxide particles tend to settle.

[0022] i) Titanium dioxide particles in an aqueous dispersion medium 90 However, the wavelength is 50-800 nm, preferably 80-500 nm, and more preferably 80-400 nm. 90 However, if the wavelength is less than 50 nm, the photocatalytic activity may be insufficient, and if it exceeds 800 nm, the titanium dioxide particles tend to settle.

[0023] i) The primary particle diameter of the titanium dioxide particles is preferably 3 to 100 nm, more preferably 3 to 50 nm, and even more preferably 3 to 30 nm. This is because if the primary particle diameter of the titanium dioxide particles in i) is less than 3 nm or greater than 100 nm, the photocatalytic activity may be insufficient. In the present invention, unless otherwise specified, the primary particle diameter refers to the arithmetic mean of the projected area circle equivalent diameter (Heywood diameter) of approximately 1000 non-overlapping particles randomly selected from multiple particle images taken using a transmission electron microscope (e.g., Hitachi High-Technologies Corporation H-9500).

[0024] i) The titanium dioxide particles are preferably used in the form of a dispersion in which the titanium dioxide particles are dispersed in an aqueous dispersion medium. The titanium dioxide particle dispersion in i) contains a predetermined range of D 50 and D 90 The material is not particularly limited as long as it contains dispersed titanium dioxide particles having the properties of the same material, but it may also contain a dispersant to obtain dispersion stability. Examples of dispersants include surfactant-type dispersants (e.g., anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants), polymer-type dispersants (e.g., polycarboxylates, polyacrylates, etc.), and inorganic-type dispersants (e.g., polyphosphates, etc.).

[0025] <Titanium oxide particles of ii> ii) The titanium oxide particles in which copper and / or iron is dissolved have a composition different from that of the titanium oxide particles of i), and are characterized in that copper and / or iron is dissolved therein.

[0026] The copper and / or iron dissolved in the titanium oxide particles of ii is for enhancing the photocatalytic activity of the titanium oxide particles of i), but by dissolving in titanium oxide particles different from those of i), the thermal and chemical stability can be enhanced, and the performance can be stably exhibited for a long period of time.

[0027] The copper dissolved in the titanium oxide particles of ii may be derived from a copper compound. For example, elemental copper (Cu), oxides (Cu2O, CuO), hydroxides (CuOH, Cu(OH)2), chlorides (CuCl, CuCl2), nitrates (Cu(NO)2), sulfates (CuSO4), halides other than chlorides (Br, I), 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 (Cu2O, CuO), hydroxides (CuOH, Cu(OH)2), chlorides (CuCl, CuCl2), nitrates (Cu(NO)2), and sulfates (CuSO4).

[0028] The content of copper in the titanium oxide particles of ii is preferably 1 to 100, more preferably 2 to 50, and still more preferably 5 to 20 in terms of the molar ratio (Ti / Cu) with titanium in the titanium oxide. This is because when the molar ratio is less than 1, it may be difficult to dissolve in titanium oxide, and when it exceeds 100, the photocatalytic activity may be insufficient.

[0029] ii) The iron dissolved in the titanium oxide particles can be derived from an iron compound, and examples include elemental iron (Fe), oxides (Fe2O3, Fe3O4), hydroxides, oxyhydroxides (FeO(OH)), chlorides (FeCl2, FeCl3), nitrates (Fe(NO)3), sulfates (FeSO4, Fe2(SO4)3), halogenated compounds (Br, I) other than chlorides, complex compounds, etc., and one or more of these may be used in combination. Among these, oxides (Fe2O3, Fe3O4), oxyhydroxides (FeO(OH)), chlorides (FeCl2, FeCl3), nitrates (Fe(NO)3), and sulfates (FeSO4, Fe2(SO4)3) are preferred.

[0030] ii) The iron content in the titanium dioxide particles is preferably 1 to 100, more preferably 2 to 50, and even more preferably 5 to 20 in terms of the molar ratio (Ti / Fe) of iron to titanium in the titanium dioxide. This is because if the molar ratio is less than 1, solid solution in titanium dioxide may be difficult, and if it exceeds 100, the photocatalytic activity may be insufficient.

[0031] ii) When the titanium oxide particles in ii) are in which copper and iron are solid-dissolved, the total content of copper and iron in the titanium oxide particles in ii) is preferably 1 to 100, more preferably 2 to 50, and even more preferably 5 to 20 in terms of the molar ratio (Ti / Cu+Fe) to titanium in the titanium oxide. This is because if the molar ratio is less than 1, solid dissolution into titanium oxide may be difficult, and if it exceeds 100, the photocatalytic activity may be insufficient.

[0032] ii) The titanium dioxide particles in the aqueous dispersion medium 50 However, it is 5 to 30 nm, preferably 5 to 20 nm. 50 However, if the wavelength is less than 5 nm or more than 30 nm, the photocatalytic activity may be insufficient.

[0033] Furthermore, the titanium dioxide particles in ii) are in the aqueous dispersion medium D 90 However, it is 10-50 nm, preferably 10-40 nm. 90However, if the wavelength is less than 10 nm or more than 50 nm, the photocatalytic activity may be insufficient.

[0034] ii) The primary particle size of the titanium dioxide particles is preferably 3 to 30 nm, more preferably 3 to 20 nm, and even more preferably 3 to 10 nm. This is because if the primary particle size of the titanium dioxide particles in ii) is less than 3 nm or greater than 30 nm, the photocatalytic activity may be insufficient. The primary particle size is the value measured by the method described above.

[0035] ii) The titanium dioxide particles are preferably used in the form of a dispersion in which the titanium dioxide particles of ii) are dispersed in an aqueous dispersion medium.

[0036] The mixing ratio of the titanium oxide particles i) and ii) contained in the titanium oxide particle composition of the present invention is preferably 99 to 1.0 in terms of their respective mass ratio [(titanium oxide particles i-TiO2) / (titanium oxide particles ii-TiO2)], more preferably 99 to 3.0, and even more preferably 99 to 5.0. This is because if the above mass ratio exceeds 99 or is less than 1.0, the photocatalytic activity may be insufficient.

[0037] The titanium oxide particle composition of the present invention is a mixture of two types of titanium oxide particles, i) titanium oxide particles and ii) titanium oxide particles in which copper and / or iron are solid-solved, in an aqueous dispersion medium. 50 However, those with a wavelength of 50 to 500 nm are preferred, and those with a wavelength of 80 to 400 nm are more preferred. 50 However, if the wavelength is less than 50 nm, the photocatalytic activity may be insufficient, and if it exceeds 500 nm, the titanium dioxide particles tend to settle. Furthermore, the titanium oxide particle composition of the present invention is a mixture of two types of titanium oxide particles, i) titanium oxide particles and ii) titanium oxide particles in which copper and / or iron are solid-solved, in an aqueous dispersion medium. 90 However, a wavelength of 80-800 nm is preferred, and a wavelength of 100-500 nm is more preferred. 90However, if the wavelength is less than 80 nm, the photocatalytic activity may be insufficient, and if it exceeds 800 nm, the titanium dioxide particles tend to settle. The titanium oxide particle composition of the present invention is D 50 and D 90 It is preferable that the particles fall within the range described above, as this allows for the creation of a photocatalytic film with high photocatalytic activity.

[0038] The titanium oxide particle composition of the present invention further contains an aqueous dispersion medium, and is preferably in the form of a dispersion liquid in which the titanium oxide particles of i) and the titanium oxide particles of ii) are dispersed in the aqueous dispersion medium. The concentration of titanium dioxide particles in the titanium dioxide particle dispersion (i) and the total concentration of titanium dioxide particles in (ii), hereinafter the same, is preferably 0.01 to 40% by mass, and particularly preferably 0.5 to 20% by mass, in terms of ease of fabricating a photocatalytic film of the required thickness.

[0039] The mass of titanium dioxide particles contained in a titanium dioxide particle dispersion can be calculated from the mass and concentration of the titanium dioxide particle dispersion. The concentration of the titanium dioxide particle dispersion can be measured by sampling a portion of the dispersion, heating it at 105°C for 1 hour to evaporate the solvent, and then calculating the concentration from the mass of the non-volatile components (titanium dioxide particles) and the sampled titanium dioxide particle dispersion according to the following formula. Concentration (%) of titanium dioxide particle dispersion = [Mass of non-volatile content (g) / Mass of titanium dioxide particle dispersion (g)] × 100

[0040] Furthermore, a binder may be added to the titanium oxide particle composition or titanium oxide particle dispersion for the purpose of facilitating the application of the dispersion to the surface of various components described later, and for facilitating the adhesion of the particles. Examples of binders include metal compound binders containing silicon, aluminum, titanium, zirconium, etc., and organic resin binders containing fluororesins, acrylic resins, urethane resins, etc.

[0041] The mass ratio of the binder to titanium oxide [titanium oxide / binder] is preferably in the range of 99 to 0.01, more preferably 9 to 0.1, and even more preferably 2.5 to 0.4. This is preferable because if the above mass ratio is within the range of 99 to 0.01, the adhesion of titanium oxide particles to the surfaces of various members is good, it functions as a binder, and the photocatalytic activity is not impaired.

[0042] Among them, in order to obtain an excellent photocatalytic film with high photocatalytic activity, it is particularly preferable to add and use a silicon compound-based binder in a mass ratio (titanium oxide / silicon compound-based binder) preferably in the range of 99 to 0.01, more preferably 9 to 0.1, and even 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, 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. can be mentioned.

[0043] <Method for producing the titanium oxide particle dispersion of i> As the method for producing the titanium oxide particle dispersion of i), a method of dispersing the titanium oxide particles of i) in an aqueous dispersion medium can be mentioned. The titanium oxide particles of i) may be commercially available products having the above-described dispersed particle diameter and primary particle diameter, or those produced by a conventional method may be used. As the aqueous dispersion medium used for the titanium oxide particle dispersion of i), the above-described ones can be used. The dispersion method is not particularly limited, and it may be dispersed by a stirrer, ultrasonic disperser, bead mill, etc. A dispersant may be added to improve the dispersibility of the titanium oxide particles. As the dispersant, any of the surfactant-type dispersant, polymer-type dispersant, and inorganic-type dispersant as described above can be used.

[0044] <Method for producing the titanium oxide particle dispersion of ii> A specific method for producing a titanium oxide particle dispersion in which copper and / or iron is solid-dissolved can be described as a method having the following steps (1) to (2). (1) A process for producing a copper and / or iron component-containing peroxotitanic acid solution from raw material titanium compounds, copper and / or iron compounds, a basic substance, hydrogen peroxide, and an aqueous dispersion medium. (2) A step to obtain a titanium dioxide particle dispersion by heating the copper and / or iron component-containing peroxotitanic acid solution produced in step (1) above at 80 to 250°C under pressure control.

[0045] ·Process (1): In step (1), a copper and / or iron component-containing peroxotitanic acid solution is produced by reacting a raw material titanium compound, a copper and / or iron compound, a basic substance, and hydrogen peroxide in an aqueous dispersion medium.

[0046] Any of the following methods [1] to [3] may be used as the reaction method. [1] A method in which copper and / or iron compounds are added to a raw material titanium compound and a basic substance in an aqueous dispersion medium and dissolved to obtain copper and / or iron-containing titanium hydroxide, impurity ions other than metal ions are removed, and hydrogen peroxide is added to obtain copper and / or iron-containing peroxotitanic acid. [2] A method of obtaining copper and / or iron-containing peroxotitanic acid by adding a basic substance to a raw material titanium compound in an aqueous dispersion medium to obtain titanium hydroxide, removing impurity ions other than metal ions, adding a copper and / or iron compound, and then adding hydrogen peroxide. [3] A method in which a basic substance is added to a raw material titanium compound in an aqueous dispersion medium to obtain titanium hydroxide, impurity ions other than metal ions are removed, hydrogen peroxide is added to obtain peroxotitanic acid, and then a copper and / or iron compound is added to obtain copper and / or iron-containing peroxotitanic acid. In addition, in the preceding step of method [1], the "raw material titanium compound and basic substance in an aqueous dispersion medium" may be divided into two aqueous dispersion mediums, such as "an aqueous dispersion medium in which the raw material titanium compound is dissolved" and "an aqueous dispersion medium in which the basic substance is dissolved," and each compound may be dissolved in one or both of the two liquids according to the solubility of each copper and / or iron compound in the two liquids, and then the two liquids may be mixed.

[0047] After obtaining peroxotitanic acid containing copper and / or iron components in this manner, titanium oxide particles can be obtained by subjecting them to the hydrothermal reaction in step (2) described below, in which the various metals are solid-solved in titanium oxide.

[0048] Examples of titanium compounds used as raw materials include inorganic salts such as titanium chloride, nitrate, and sulfate; organic salts such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid; and titanium hydroxide precipitated by hydrolysis of aqueous solutions thereof with the addition of alkali. One or more of these may be used in combination. Among these, titanium chloride (TiCl3, TiCl4) is preferred.

[0049] The copper compound, iron compound, and aqueous dispersion medium are used as described above, in the aforementioned formulations. The concentration of the aqueous solution of the raw titanium compound formed from the raw titanium compound and the aqueous dispersion medium is preferably 60% by mass or less, and particularly preferably 30% by mass or less. The lower limit of the concentration is selected as appropriate, but is usually preferably 1% by mass or more.

[0050] The basic substance is used to smoothly convert the raw titanium compound into titanium hydroxide. Examples include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide and potassium hydroxide, and amine compounds such as ammonia, alkanolamines, and alkylamines. Among these, ammonia is particularly preferred, and it is used by adding it in an amount such that the pH of the aqueous solution of the raw titanium compound becomes 7 or higher, especially 7 to 10. The basic substance may also be used as an aqueous solution of an appropriate concentration together with the aqueous dispersion medium.

[0051] Hydrogen peroxide is used to convert the above-mentioned raw material titanium compound or titanium hydroxide into peroxotitanium, that is, a titanium oxide compound containing a Ti-OO-Ti bond, and is usually used in the form of hydrogen peroxide solution. The amount of hydrogen peroxide added is preferably 1.5 to 20 times the amount of substance of Ti, or the total amount of substance of Ti, Cu, or Fe. In the reaction in which hydrogen peroxide is added 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.

[0052] The peroxotitanic acid solution obtained in this way, which contains copper and / or iron components, may contain an alkaline or acidic substance for pH adjustment or the like. Examples of alkaline substances include ammonia, sodium hydroxide, calcium hydroxide, alkylamines, etc., and examples of acidic substances include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, phosphoric acid, and hydrogen peroxide, and organic acids such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid. In this case, the pH of the obtained peroxotitanic acid solution is preferably 1 to 9, particularly 4 to 7, from the standpoint of safety during handling.

[0053] ·Process (2): In step (2), the copper and / or iron-containing peroxotitanic acid solution obtained in step (1) is subjected to a hydrothermal reaction for 0.01 to 24 hours at a temperature of 80 to 250°C, preferably 100 to 250°C, under pressure control. A reaction temperature of 80 to 250°C is appropriate from the viewpoint of reaction efficiency and controllability of the reaction, and as a result, the copper and / or iron-containing peroxotitanic acid is converted into titanium oxide particles in which copper and / or iron are solid-solved. Here, "under pressure control" means that if the reaction temperature exceeds the boiling point of the dispersion medium, the reaction temperature is maintained by applying appropriate pressure, and this includes cases where the temperature is controlled at atmospheric pressure when it 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, and more preferably about 0.20 to 4.5 MPa. The reaction time is preferably 1 minute to 24 hours. This step (2) yields a dispersion of titanium oxide particles in which copper and / or iron are dissolved. The pH of the titanium oxide particle dispersion in which copper and / or iron is solid-dissolved obtained in step (2) is preferably 7 to 14, and more preferably 9 to 14. The titanium oxide particle dispersion in which copper and / or iron is solid-dissolved obtained in step (2) may contain an alkaline substance or an acidic substance for pH adjustment, etc., so that it has the aforementioned pH. The alkaline substance, acidic substance and pH adjustment method are the same as those for the copper and / or iron-containing peroxotitanic acid solution obtained in step (1) above.

[0054] The cumulative distribution diameter (D) of titanium oxide particles obtained here (ii) 50 and D 90 The particle size is preferably within the range already described, and it is possible to control the particle size by adjusting the reaction conditions. For example, the particle size can be reduced by shortening the reaction time or heating time.

[0055] <Method for producing titanium dioxide particle dispersion> Mix the titanium dioxide particle dispersions i) and ii) that were prepared separately. The mixing method is not particularly limited and may be done by stirring with a stirrer or by dispersing with an ultrasonic disperser. The mixing temperature is preferably 20 to 100°C and the time is preferably 1 minute to 3 hours. The mixing ratio should be such that the mass ratio of titanium dioxide particles in each titanium dioxide particle dispersion is as described above.

[0056] <Photocatalytic film containing titanium dioxide particle composition / Component having a photocatalytic film on its surface> The titanium oxide particle composition of the present invention can be used to form a photocatalytic film on the surface of various components. While the components are not particularly limited, examples of materials for the components include inorganic materials and organic materials, with inorganic materials being particularly preferred. This is because the photocatalytic film obtained from the titanium oxide particles of the present invention has high photocatalytic activity, and using organic materials may cause the substrate itself to decompose due to the photocatalytic activity. Furthermore, these components can have various shapes depending on their respective purposes and applications.

[0057] Inorganic materials include, for example, non-metallic inorganic materials and metallic inorganic materials. Examples of non-metallic inorganic materials include glass, ceramics, and stone. These may be manufactured into various forms such as filters, tiles, glass, mirrors, walls, and decorative materials. Examples of metallic inorganic materials include cast iron, steel, iron, iron alloys, aluminum, aluminum alloys, nickel, nickel alloys, and zinc die-cast. These may be plated with the above-mentioned metallic inorganic materials, coated with the above-mentioned organic materials, or plated on the surface of the following organic materials or non-metallic inorganic materials.

[0058] Examples of organic materials include synthetic resin materials such as polyvinyl chloride (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, phenolic resin, and 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 manufactured into films, sheets, fiber materials, fiber products, other molded products, laminates, or other products with the required shape and structure.

[0059] The titanium oxide particle composition of the present invention, when used as a titanium oxide particle dispersion, is particularly useful for producing photocatalytic films with excellent decomposition properties for volatile organic compounds when applied to various substrates whose surfaces are made of inorganic materials such as ceramics and glass.

[0060] As a method for forming a photocatalytic film on the surface of various components, a titanium dioxide particle dispersion can be applied to the surface of the component by known coating methods such as dip coating, flow coating, or spray coating, and then dried by known drying methods such as far-infrared drying, IH drying, or hot air drying. Various thicknesses of the photocatalytic film can be selected, but generally, a range of 10 nm to 50 μm is preferred. This forms a coating of titanium dioxide particles as described above. In this case, if the dispersion contains the binder in the amount described above, a coating containing titanium dioxide particles and the binder is formed.

[0061] The photocatalytic film formed in this manner exhibits excellent photocatalytic activity, particularly in the ultraviolet region (wavelengths of 10 to 400 nm). Various components on which this photocatalytic film is formed can more rapidly decompose organic matter adsorbed on their surfaces due to the photocatalytic action of titanium dioxide, thereby exhibiting effects such as deodorization, antibacterial properties, and surface cleaning. [Examples]

[0062] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Various measurements in the present invention were performed as follows.

[0063] (1) The 50% and 90% cumulative distribution diameters (D) of titanium dioxide particles in the dispersion. 50 and D 90 ) D of titanium dioxide particles in dispersion 50 and D 90 These values ​​were calculated as the 50% and 90% cumulative distribution diameters based on volume, measured by dynamic light scattering using laser light, with a particle size distribution analyzer (ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.)).

[0064] (2) Test of acetaldehyde gas decomposition performance of photocatalytic film The activity of photocatalytic films prepared by coating and drying a dispersion was evaluated by the decomposition reaction of acetaldehyde gas. The evaluation was performed using a batch-type gas decomposition performance evaluation method. Each titanium dioxide particle dispersion prepared in the examples or comparative examples was spread on one side of a 100 mm square glass plate using a wire bar coater so that the dry mass of titanium dioxide particles was approximately 1 mg to prepare an evaluation sample. This sample was then dried in an oven set to 400°C for 1 hour to obtain a sample for evaluating acetaldehyde gas decomposition performance. Using this evaluation sample, the photocatalytic activity (volatile organic compound decomposition performance) of titanium dioxide particles was evaluated by the decomposition reaction of acetaldehyde gas. The evaluation was performed using a batch-type gas decomposition performance evaluation method. Specifically, an evaluation sample was placed in a 5L stainless steel cell with a quartz glass window. The cell was then filled with acetaldehyde gas at an initial concentration, humidified to 50%, and irradiated with light from a light source placed at the top of the cell. When acetaldehyde gas is decomposed by the photocatalytic action of titanium dioxide, the acetaldehyde gas concentration in the cell decreases. Therefore, the strength of the photocatalytic activity can be confirmed by measuring this concentration change. The acetaldehyde gas concentration was measured using a photoacoustic multi-gas monitor (product name "INNOVA1412," manufactured by LumaSense) to evaluate the photocatalytic activity by measuring the time from the start of light irradiation until the acetaldehyde gas concentration fell below 1 ppm. A shorter time indicates higher photocatalytic activity, while a longer time indicates lower photocatalytic activity.

[0065] In the evaluation of photocatalytic activity under ultraviolet irradiation, a UV fluorescent lamp (product model "FL10 BLB", Toshiba Lighting & Technology Corporation) was used as the light source, with an irradiance of 0.1 mW / cm². 2 The cells were irradiated with ultraviolet light (wavelength range 300-400 nm, peak wavelength 352 nm) under the specified conditions. At this time, the initial acetaldehyde concentration in the cells was set to 5 ppm.

[0066] (3) Identification of the crystalline phase of titanium oxide particles The crystalline phase of the titanium dioxide particles was identified by measuring the powder X-ray diffraction (product name "Tabletop X-ray Diffractometer D2 PHASER", Bruker AXS Co., Ltd.) of the titanium dioxide particle powder recovered after drying the obtained dispersion of titanium dioxide particles at 105°C for 3 hours.

[0067] (4)i) Preparation of titanium dioxide particle dispersion Table 1 shows the crystalline phase and dispersed particle size (D 50 , D 90 Using titanium dioxide particles having the primary particle size and other properties, titanium dioxide particle dispersions 1A, 1B, 1C, and 1D were prepared by dispersing them in pure water.

[0068] <Preparation of Titanium Dioxide Particle Dispersion 1E> A 36% by mass aqueous solution of titanium(IV) chloride was diluted 10-fold with pure water, and then neutralized and hydrolyzed by gradually adding 10% by mass aqueous ammonia to obtain a precipitate of titanium hydroxide. The pH at this time was 8. The obtained precipitate was deionized by repeatedly adding pure water and decanting. To the titanium hydroxide precipitate after this deionization treatment, 35% by mass aqueous hydrogen peroxide was added so that the H2O2 / Ti (molar ratio) was 8, and then the mixture was stirred at 80°C for 1 hour to allow it to react sufficiently, obtaining an orange, transparent peroxotitanic acid solution (1e). A dispersion of titanium dioxide particles (1E) (titanium dioxide concentration 1% by mass, pH 11) was obtained by placing 400 mL of peroxotitanic acid solution (1e) into a 500 mL autoclave, hydrothermally treating it at 135°C for 60 minutes, and then adjusting the concentration by adding pure water. Powder X-ray diffraction measurements of the titanium dioxide particles (1E) revealed that the only peak observed was that of anatase-type titanium dioxide.

[0069] Titanium dioxide particle concentration, crystalline phase, and dispersed particle size (D) of titanium dioxide particle dispersions 1A to E. 50 , D 90 The primary particle size and pH are summarized in Table 1. [Table 1]

[0070] (5)ii) Preparation of titanium dioxide particle dispersion [Preparation Example 1] <Preparation of a dispersion of titanium oxide particles in which copper is solid-dissolved> Copper(II) chloride was added and dissolved in a 36% by mass aqueous solution of titanium(IV) chloride so that the Ti / Cu (molar ratio) was 10. This solution was then diluted 10-fold with pure water, and neutralization and hydrolysis were carried out by gradually adding 10% by mass aqueous ammonia to obtain a precipitate of titanium hydroxide containing copper. The pH at this time was 8. The obtained precipitate was deionized by repeatedly adding pure water and decanting. 35% by mass aqueous hydrogen peroxide was added so that the H2O2 / (Ti+Cu) (molar ratio) was 10, and the mixture was then stirred at 80°C for 1 hour to allow the reaction to proceed thoroughly, obtaining a green, transparent copper-containing peroxotitanic acid solution (2a).

[0071] A 400 mL copper-containing peroxotitanic acid solution (2a) was placed in a 500 mL autoclave and subjected to hydrothermal treatment at 135°C for 80 minutes. Afterward, pure water was added to adjust the concentration, yielding a dispersion of titanium oxide particles (2A) with solid-solution copper (titanium oxide concentration 1% by mass). Powder X-ray diffraction measurements of the titanium oxide particles (2A) revealed that only anatase-type titanium oxide peaks were observed, indicating that copper was solid-solution in the titanium oxide.

[0072] [Preparation Example 2] <Preparation of a dispersion of titanium oxide particles in which copper is solid-dissolved> A dispersion of titanium oxide particles (2B) with solid-solution copper (titanium oxide concentration 1% by mass) was obtained in the same manner as in Preparation Example 1, except that the amount of copper(II) chloride added to the titanium(IV) chloride aqueous solution was adjusted to a Ti / Cu (molar ratio) of 30. Powder X-ray diffraction measurements of the titanium oxide particles (2B) showed that only the peaks of anatase-type titanium oxide were observed, indicating that copper was solid-solution in the titanium oxide.

[0073] [Preparation Example 3] <Preparation of a titanium oxide particle dispersion in which iron is solid-dissolved> To a 36% by mass aqueous solution of titanium(IV) chloride, iron(III) chloride was added and dissolved so that the Ti / Fe (molar ratio) was 10. After diluting this solution 10-fold with pure water, 10% by mass aqueous ammonia was gradually added to neutralize and hydrolyze it, yielding a precipitate of iron-containing titanium hydroxide. The pH at this time was 8. The obtained precipitate was deionized by repeatedly adding pure water and decanting. 35% by mass aqueous hydrogen peroxide was added so that the H2O2 / (Ti+Fe) (molar ratio) was 10, and then the mixture was stirred at 80°C for 1 hour to allow it to react thoroughly, yielding an orange, transparent iron-containing peroxotitanic acid solution (2c).

[0074] A 400 mL solution of iron-containing peroxotitanic acid (2c) was placed in a 500 mL autoclave and subjected to hydrothermal treatment at 135°C for 80 minutes. Afterward, pure water was added to adjust the concentration, yielding a dispersion of titanium oxide particles (2C) with solid-dissolved iron (titanium oxide concentration 1% by mass). Powder X-ray diffraction measurements of the titanium oxide particles (2C) revealed that only anatase-type titanium oxide peaks were observed, indicating that iron was solid-dissolved in the titanium oxide.

[0075] [Preparation Example 4] <Preparation of a dispersion of titanium oxide particles in which copper is solid-dissolved> Except for the hydrothermal treatment in an autoclave for 160 minutes, a dispersion of titanium oxide particles (2D) with solid-solution copper (titanium oxide concentration 1% by mass) was obtained in the same manner as in Preparation Example 1. Powder X-ray diffraction measurements of the titanium oxide particles (2D) showed that only the peak of anatase-type titanium oxide was observed, indicating that copper was solid-solution in the titanium oxide.

[0076] Table 2 shows the raw material ratio, hydrothermal treatment conditions, and dispersed particle size (D) of the titanium oxide particles prepared in each preparation example. 50 , D 90 The primary particle size and pH are shown together. The dispersed particle size was measured using dynamic light scattering with laser light (ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.)).

[0077] [Table 2]

[0078] (6) Preparation of titanium dioxide particle dispersion [Example 1] <Titanium dioxide particle dispersion consisting of titanium dioxide particles and titanium dioxide particles in which copper is solid-dissolved> Titanium dioxide particle dispersion (3A) was obtained by mixing titanium dioxide particle dispersion 1A and titanium dioxide particle dispersion 2A with a stirrer so that the mass ratio (1A / 2A) was 9.0.

[0079] [Example 2] <Titanium dioxide particle dispersion consisting of titanium dioxide particles and titanium dioxide particles in which copper is solid-dissolved> Titanium dioxide particle dispersion (3B) was obtained by mixing titanium dioxide particle dispersion 1B and titanium dioxide particle dispersion 2B with a stirrer so that the mass ratio (1B / 2B) was 2.5.

[0080] [Example 3] <Titanium dioxide particle dispersion consisting of titanium dioxide particles and titanium dioxide particles in which iron is solid-dissolved> Titanium dioxide particle dispersion 1C and titanium dioxide particle dispersion 2C were mixed in a stirrer to obtain titanium dioxide particle dispersion (3C) in a mass ratio (1C / 2C) of 19.

[0081] [Example 4] <Titanium dioxide particle dispersion consisting of titanium dioxide particles and titanium dioxide particles in which copper is solid-dissolved> Titanium dioxide particle dispersion (3D) was obtained by mixing titanium dioxide particle dispersion 1A and titanium dioxide particle dispersion 2D with a stirrer so that the mass ratio (1A / 2D) was 9.0.

[0082] [Comparative Example 1] <Titanium dioxide particle dispersion consisting of titanium dioxide particles and titanium dioxide particles in which copper is solid-dissolved> Titanium oxide particle dispersion (3E) was obtained by mixing titanium oxide particle dispersion 1D and titanium oxide particle dispersion 2A with a stirrer so that the mass ratio (1D / 2A) was 9.0.

[0083] [Comparative Example 2] <Titanium dioxide particle dispersion consisting of titanium dioxide particles and titanium dioxide particles> Titanium oxide particle dispersion (3F) was obtained by mixing titanium oxide particle dispersion 1A and titanium oxide particle dispersion 1E with a stirrer so that the mass ratio (1A / 1E) was 9.0.

[0084] [Comparative Example 3] <Titanium oxide particle dispersion consisting of titanium oxide particles> Titanium dioxide particle dispersion (3G) was obtained from titanium dioxide particle dispersion 1A.

[0085] [Comparative Example 4] <Titanium oxide particle dispersion consisting of titanium oxide particles> Titanium dioxide particle dispersion (3H) was obtained from titanium dioxide particle dispersion 2A.

[0086] [Comparative Example 5] <Titanium oxide particle dispersion consisting of titanium oxide particles> Titanium dioxide particle dispersion (3I) was obtained from titanium dioxide particle dispersion 2D.

[0087] [Comparative Example 6] <Titanium oxide particle dispersion consisting of titanium oxide particles> Titanium dioxide particle dispersion (3J) was obtained from titanium dioxide particle dispersion 1B.

[0088] [Comparative Example 7] <Titanium oxide particle dispersion consisting of titanium oxide particles> Titanium dioxide particle dispersion (3K) was obtained from titanium dioxide particle dispersion 1C.

[0089] [Example 5] A silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added to a titanium dioxide particle dispersion (3A) in a mass ratio of titanium dioxide particles / binder of 4. The mixture was then stirred at 25°C for 10 minutes to obtain a titanium dioxide particle dispersion (3L) containing the binder.

[0090] [Comparative Example 6] A silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added to a titanium dioxide particle dispersion (3G) in a mass ratio of titanium dioxide particles / binder of 4. The mixture was then stirred at 25°C for 10 minutes to obtain a titanium dioxide particle dispersion (3M) containing the binder.

[0091] Table 3 shows the weight ratio, concentration, and particle size (D) of titanium dioxide particle dispersions i and ii prepared in each example or comparative example. 50 , D 90 ), and pH are shown together.

[0092] [Table 3]

[0093] (7) Preparation of a sample member having a photocatalytic film Each titanium dioxide particle dispersion prepared in the above examples or comparative examples was coated onto a 100 mm square glass plate using a #7 wire bar coater to form a photocatalytic film containing 1 mg of photocatalytic titanium dioxide particles. The film was then dried in an oven set to 400°C for 1 hour to obtain a sample material for evaluating acetaldehyde gas decomposition performance.

[0094] [Photocatalytic performance test under UV irradiation] Acetaldehyde decomposition tests were performed on sample members having photocatalytic films in the examples and comparative examples under UV fluorescent lamp irradiation. Evaluation was based on the time required to reduce the initial acetaldehyde concentration from 5 ppm to 1 ppm. The tests were conducted for up to 24 hours.

[0095] Each test result was evaluated according to the following criteria. • Excellent (indicated as ◎) ... Reduced to 1 ppm within 2 hours • Good (indicated as ○) • Reduced to 1 ppm within 4 hours • Slightly poor (indicated as △) • Reduced to 1 ppm within 6 hours • Poor (marked with ×) • Requires more than 6 hours to reduce by 1 ppm

[0096] Table 4 summarizes the acetaldehyde gas decomposition test results for the examples and comparative examples. [Table 4]

[0097] From the results of the Examples and Comparative Example 1, it was found that having the particle size of the titanium dioxide particles of the present invention fall within a specific range is important for obtaining high photocatalytic activity.

[0098] From the results of the Examples and Comparative Example 2, it can be seen that having copper or iron solid-dissolved in the titanium oxide particles of ii) is important for obtaining high photocatalytic activity. From the results of the Examples and Comparative Example 3, it can be seen that adding titanium dioxide particles as described in ii) is important for obtaining high photocatalytic activity. From the results of the Examples and Comparative Example 4, it can be seen that the addition of titanium dioxide (i) is essential to obtain high photocatalytic activity. The results from Comparative Examples 4 and 5 show that titanium oxide particles with copper solid solution exhibit lower photocatalytic activity compared to titanium oxide without copper solid solution, indicating that mixing them with titanium oxide particles from i) is essential to obtain high photocatalytic activity. Examples 5 and Comparative Example 6 show that even when a binder is added, the photocatalytic film containing the titanium dioxide particle composition of the present invention exhibits high photocatalytic activity. The titanium oxide particle composition of the present invention is useful for producing photocatalytic films with high photocatalytic activity by applying it to various substrates made of inorganic materials such as glass and metals, and organic materials such as resins. In particular, it is useful as a photocatalyst for filters in photocatalytic air purifiers where the performance of decomposing volatile organic compounds is important.

Claims

1. i) Titanium dioxide particles and ii) Titanium oxide particles in which copper and / or iron are in solid solution, A titanium dioxide particle composition containing two types of titanium dioxide particles, i) The titanium dioxide particles have a volume-based 50% cumulative distribution diameter D, which is measured by dynamic light scattering using laser light in an aqueous dispersion medium. 50 The wavelength is 30-500 nm, and the 90% cumulative distribution diameter is D 90 The wavelength is 50-800 nm. ii) Titanium oxide particles in which copper and / or iron are solid-dissolved have a volume-based 50% cumulative distribution diameter D measured by dynamic light scattering using laser light in an aqueous dispersion medium. 50 The 90% cumulative distribution diameter is 5-30 nm. 90 The range is 10-50 nm. i) the mass ratio of titanium oxide particles to ii) titanium oxide particles in which copper and / or iron are solid-solved (i - TiO 2 / ii-TiO 2 A titanium dioxide particle composition in which the ratio is 99 to 1.

0.

2. i) Titanium oxide particles and ii) Titanium oxide particles in which copper and / or iron are solid-solved, as measured by dynamic light scattering using laser light in an aqueous dispersion medium, the 50% cumulative distribution diameter D based on volume. 50 The wavelength is 50-500 nm, and the 90% cumulative distribution diameter is D 90 The titanium dioxide particle composition according to claim 1, wherein the wavelength is 80 to 800 nm.

3. ii) The titanium oxide particle composition according to claim 1, wherein the content of copper or iron dissolved in the titanium oxide particles is 1 to 100 in molar ratio (Ti / Cu or Fe) with respect to titanium in the titanium oxide.

4. Furthermore, the titanium dioxide particle composition according to claim 1, further comprising a binder.

5. The titanium oxide particle composition according to claim 4, wherein the binder is a silicon compound-based binder.

6. A photocatalytic film comprising the titanium oxide particle composition according to any one of claims 1 to 5.

7. Furthermore, the titanium dioxide particle composition according to any one of claims 1 to 5, wherein the composition contains an aqueous dispersion medium and is a dispersion in which titanium dioxide particles are dispersed in the aqueous dispersion medium.

8. A member having the photocatalytic film described in claim 6 on its surface.

Images