Titanium oxide particle / metal particle composition and method for producing the same

Abstract

Provided are: a titanium oxide particle-metal particle composition having a higher photocatalytic activity, in particular, visible light activity, as compared with a conventional counterpart; and a manufacturing method therefor.　The present invention provides a titanium oxide particle-metal particle composition containing two types of particles, namely, i) titanium oxide particles, in which tin components and transition metal components for increasing the visible light activity are dissolved, iron components and silicon components are not dissolved, and surfaces thereof are modified by the iron components and the silicon components, and ii) metal particles containing an antibacterial metal.

Description

[Technical Field]

[0001] The present invention relates to a titanium oxide particle / metal particle composition and a method for producing the same, and more specifically to a titanium oxide particle / metal particle composition (dispersion, photocatalytic film formed using the dispersion, member having a photocatalytic film on its surface) that can be used to easily produce a highly transparent photocatalytic film that exhibits antibacterial properties regardless of whether or not light is irradiated, and a method for producing the same. [Background technology]

[0002] In recent years, consumers have been increasingly seeking a hygienic living environment, and there has been growing interest in household products that have been treated to maintain cleanliness, such as with antibacterial, antifungal, antiviral, deodorizing, and stain-resistant properties. Photocatalytic materials are attracting attention because they are widely effective in cleaning substrate surfaces, providing antibacterial, antifungal, antiviral, deodorizing, and antifouling properties through photocatalytic reactions that occur when exposed to light such as sunlight or artificial lighting.

[0003] A photocatalytic reaction is a reaction caused by excited electrons and holes generated when a photocatalyst, such as titanium oxide, absorbs light. The excited electrons and holes generated on the titanium oxide surface by the photocatalytic reaction undergo an oxidation-reduction reaction with oxygen and water adsorbed on the titanium oxide surface, generating active species. These active species decompose organic microorganisms, viruses, odors, and dirt, which is thought to achieve the cleaning effect on the substrate surface described above. The strengths of photocatalysts are that they are basically effective against any organic material, so they are effective against a wide variety of microorganisms, viruses, odors, and dirt, and they hardly deteriorate over time.

[0004] Recently, studies have been conducted to apply the above-mentioned photocatalytic action not only to outdoor use where ultraviolet light (wavelength 10 to 400 nm) can be used, but also to indoor spaces illuminated by light sources such as fluorescent lamps, where the majority of light is in the visible range (wavelength 400 to 800 nm). For example, a tungsten oxide photocatalyst (JP 2009-148700 A: Patent Document 1) has been developed as a visible light responsive photocatalyst.

[0005] Known methods for improving the visible light activity of titanium oxide photocatalysts include a method of supporting iron or copper on the surface of titanium oxide fine particles or metal-doped titanium oxide fine particles (e.g., JP 2012-210632 A: Patent Document 2, JP 2010-104913 A: Patent Document 3, JP 2011-240247 A: Patent Document 4, and JP 7-303835 A: Patent Document 5), a method of separately preparing titanium oxide fine particles doped with tin and a transition metal that enhances visible light activity, and titanium oxide fine particles doped with copper, and then mixing these particles together for use (WO 2014 / 045861 A: Patent Document 6), and a method of separately preparing titanium oxide fine particles doped with tin and a transition metal that enhances visible light responsiveness, and titanium oxide fine particles doped with an iron-group element, and then mixing these particles for use (WO 2016 / 152487 A: Patent Document 7).

[0006] In Patent Document 7, titanium oxide microparticles having tin and a transition metal that enhances visible light activity dissolved therein, and titanium oxide microparticles having an iron-group element dissolved therein are separately prepared and then mixed to obtain a visible-light-responsive photocatalytic titanium oxide microparticle dispersion liquid. High decomposition activity can be obtained under conditions of only visible light by using a photocatalytic film formed using this. Furthermore, it has also been shown that acetaldehyde gas can be decomposed under conditions of only visible light by using a photocatalytic film formed using a titanium oxide microparticle dispersion liquid in which iron components are adsorbed (supported) on the surface of titanium oxide microparticles having tin and a transition metal that enhances visible light activity dissolved therein. However, the iron components cause the titanium oxide microparticles to aggregate and precipitate, impairing the quality of the resulting photocatalytic film. Therefore, the amount of iron components that can be added is limited, and the resulting photocatalytic activity is low.

[0007] As mentioned above, although there has been much research being done to improve photocatalytic activity, it is important in the real world that harmful substances be decomposed and removed as quickly as possible, and so further improvements in photocatalytic activity are required.

[0008] Furthermore, since photocatalytic reactions are triggered by irradiation with ultraviolet light (wavelength 10 to 400 nm) or visible light (wavelength 400 to 800 nm), the effect cannot be obtained in principle in dark places without natural light or artificial lighting. On the other hand, bacteria and fungi (mold) can grow even without light, so for products that require sustained performance for a desired period of time, such as antibacterial products, materials that exhibit antibacterial properties even in dark places where there is no light are required.

[0009] To address the above-mentioned issues, photocatalytic materials that complement the functions of photocatalysts by combining them with antibacterial agents other than photocatalysts are being investigated. Because photocatalysts decompose organic matter, it is appropriate to use inorganic antibacterial materials. For example, it has been disclosed that the addition of silver or copper as an antibacterial and antifungal component provides antibacterial and antifungal properties in dark places (JP Patent Publication No. 2000-051708: Patent Document 8, JP Patent Publication No. 2008-260684: Patent Document 9).

[0010] Generally, photocatalysts are used by dispersing photocatalyst particles in a solvent, mixing in film-forming components to form a paint, and applying the paint to a substrate, but as mentioned above, adding metal components such as silver, copper, zinc, etc. to improve antibacterial performance often causes practical problems. That is, as a method for supporting metals such as silver, copper, zinc, etc. or their compounds, if the metal raw material is reacted with the photocatalyst particle powder to support the metal, it is not preferable because it requires a great deal of effort to subsequently disperse the metal in a solvent, and if the metal raw material is added to a dispersion liquid in which the photocatalyst particles are previously dispersed, the dispersion stability of the photocatalyst particles is impaired, causing aggregation, and it is often difficult to obtain the transparency required for practical use when forming this photocatalyst thin film on various substrates.

[0011] Furthermore, in the case of photocatalysts in which components that improve photocatalytic activity are attached to the surface, simply adding these metal components weakens the effect of attaching the components that improve photocatalytic activity, and there is a problem that the expected photocatalytic function cannot be obtained.Until now, there have been no photocatalytic thin films that combine practically sufficient antibacterial properties with the transparency required for application to a variety of substrates. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-148700 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-210632 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-104913 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-240247 [Patent Document 5] Japanese Patent Application Publication No. 7-303835 [Patent Document 6] International Publication No. 2014 / 045861 [Patent Document 7] International Publication No. 2016 / 152487 [Patent Document 8] Japanese Patent Application Laid-Open No. 2000-051708 [Patent Document 9] Japanese Patent Application Laid-Open No. 2008-260684 Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, an object of the present invention is to provide a titanium oxide particle / metal particle composition that has higher photocatalytic activity, particularly visible light activity, than conventional compositions, and further exhibits high antibacterial properties regardless of whether or not light is irradiated, and a method for producing the same. [Means for solving the problem]

[0014] In order to achieve the above-mentioned object, the present inventors conducted detailed studies on the metal elements to be dissolved in titanium oxide particles and combinations thereof, the metal elements to be used to modify titanium oxide particles and combinations thereof, and combinations of titanium oxide particles with various materials and their quantitative ratios. As a result, they found that a titanium oxide particle-metal particle composition containing two types of particles - titanium oxide particles with a specific metal dissolved therein and whose surfaces are modified with iron and silicon components, and metal particles containing a separately prepared antibacterial metal - has dramatically improved photocatalytic activity, particularly activity under visible light, compared to conventional compositions, and furthermore, it exhibits high antibacterial properties regardless of the presence or absence of light irradiation, and can easily produce a highly transparent photocatalytic thin film, which led to the present invention.

[0015] Therefore, the present invention provides the titanium oxide particle / metal particle composition and the method for producing the same shown below.

[0016] [1] i) titanium oxide particles having a surface modified with a tin component and a transition metal component that enhances visible light activity, but not with an iron component or a silicon component; ii) metal particles containing antibacterial metals; A titanium oxide particle / metal particle composition containing two types of particles. [2] ii) The titanium oxide particle / metal particle composition according to [1], wherein a protective agent is adsorbed onto the surface of metal particles containing the antibacterial metal. [3] ii) The titanium oxide particle / metal particle composition according to [1] or [2], wherein the antibacterial metal contained in the antibacterial metal-containing metal particles is at least one metal selected from silver, copper, and zinc. [4] The titanium oxide particle / metal particle composition according to [3], wherein the antibacterial metal contained in the antibacterial metal-containing metal particles of ii) contains at least silver. [5] i) The titanium oxide particle / metal particle composition according to any one of [1] to [4], wherein the content of the tin component dissolved in the titanium oxide particles is 1 to 1,000 in terms of a molar ratio (TiO2 / Sn) to the titanium oxide. [6] i) The titanium oxide particle / metal particle composition according to any one of [1] to [5], wherein the mass ratio of the iron component (in terms of oxide) modifying the surface of the titanium oxide particles to the titanium oxide (TiO2 / Fe2O3) is 10 to 100,000, and the mass ratio of the silicon component (in terms of oxide) to the titanium oxide (TiO2 / SiO2) is 1 to 10,000. [7] The titanium oxide particle / metal particle composition according to any one of [1] to [6], wherein the transition metal component that is dissolved in the titanium oxide particles and that enhances visible light activity is at least one selected from molybdenum, tungsten, and vanadium. [8] i) The titanium oxide particle / metal particle composition according to [7], 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 a molar ratio to the titanium oxide (TiO2 / Mo, TiO2 / W or TiO2 / V). [9] The titanium oxide particle / metal particle composition according to any one of [1] to [8], wherein the mass ratio (TiO2 / M) of the titanium oxide particles (i) to the antibacterial metal component (M) contained in the metal particles (ii) is 0.0001 to 10.

[10] The titanium oxide particle / metal particle composition according to any one of [1] to [9], further comprising a binder.

[11] The titanium oxide particle / metal particle composition according to

[10] , wherein the binder is a silicon compound-based binder.

[12] The composition according to any one of [1] to

[11] , wherein the titanium oxide particle / metal particle composition is a dispersion of titanium oxide particles / metal particles.

[13] The composition according to any one of [1] to

[11] , wherein the titanium oxide particle / metal particle composition is a thin film of titanium oxide particles / metal particles.

[14] A member having the composition according to

[13] on its surface.

[15] A method for producing the composition according to

[12] , comprising the following steps (1) to (8): (1) A step of producing a peroxotitanic acid solution containing a tin component and a transition metal component from raw material titanium compounds, tin compounds, transition metal compounds, basic substances, hydrogen peroxide, and an aqueous dispersion medium. (2) A step of heating the peroxotitanic acid solution containing the tin component and the transition metal component produced in the above step (1) at 80 to 250°C under pressure control to obtain a titanium oxide particle dispersion liquid in which the tin component and the transition metal component are solid-dissolved. (3) A step of producing a solution or dispersion of an iron component and a silicon component from an iron compound, a silicon compound, and an aqueous dispersion medium. (4) A step of mixing the titanium oxide particle dispersion liquid produced in the above step (2) with the solution or dispersion liquid of iron and silicon components produced in the step (3) to obtain a titanium oxide particle dispersion liquid whose surfaces are modified with iron and silicon components. (5) A step of producing a solution containing the raw antibacterial metal compound and a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (6) A step of producing a metal particle dispersion by mixing the solution containing the raw antibacterial metal compound produced in the step (5) with a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (7) A step of washing the metal particle dispersion liquid produced in the above step (6) with an aqueous dispersion medium by membrane filtration. (8) A step of mixing the titanium oxide particle dispersion liquid and the metal particle dispersion liquid obtained in the steps (4) and (7). [Effects of the Invention]

[0017] The titanium oxide particle / metal particle composition of the present invention has higher photocatalytic activity than conventional compositions, particularly when exposed to visible light (wavelengths of 400 to 800 nm) alone. Furthermore, it exhibits high antibacterial properties regardless of whether or not light is irradiated, and can easily form highly transparent photocatalytic thin films. Therefore, the titanium oxide particle / metal particle composition of the present invention is useful for components used in indoor spaces illuminated by artificial lighting, such as fluorescent lamps and white LEDs, where rapid cleaning of the substrate surface is required. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below. <Titanium oxide particle / metal particle composition> The titanium oxide particle / metal particle composition of the present invention comprises: i) titanium oxide particles having a surface modified with a tin component and a transition metal that enhances visible light activity, but not with an iron component or a silicon component; ii) metal particles containing antibacterial metals; It contains two types of particles: In one embodiment of the titanium oxide particle / metal particle composition of the present invention, the composition is a dispersion of titanium oxide particles / metal particles. In another embodiment of the titanium oxide particle / metal particle composition of the present invention, the composition is a thin film (photocatalytic thin film) of titanium oxide particles / metal particles.

[0019] First, an embodiment in which the titanium oxide particle / metal particle composition of the present invention is a dispersion of titanium oxide particles / metal particles, that is, a titanium oxide particle / metal particle dispersion, will be described. The titanium oxide particle / metal particle dispersion of the present invention is In an aqueous dispersion medium, i) titanium oxide particles having a surface modified with a tin component and a transition metal that enhances visible light activity, but not with an iron component or a silicon component; ii) metal particles containing antibacterial metals; As will be described later, this is obtained by mixing two types of particle dispersions, a titanium oxide particle dispersion and a metal particle dispersion, which are separately prepared.

[0020] In the titanium oxide particle / metal particle dispersion of the present invention, the content ratio of i) titanium oxide particles to ii) the antibacterial metal component (M) contained in the metal particles is, in mass ratio, TiO2 / M, from 1 to 100,000, preferably from 10 to 10,000, and more preferably from 100 to 1,000. If the mass ratio is less than 1, the photocatalytic performance is not fully exhibited, which is not preferred, and if it exceeds 100,000, the antibacterial performance is not fully exhibited, which is not preferred.

[0021] Here, the dispersed particle diameter of the mixture of titanium oxide particles and metal particles in the titanium oxide particle-metal particle dispersion is the 50% cumulative distribution diameter (D 50 ) is preferably 3 to 50 nm, more preferably 3 to 40 nm, and even more preferably 3 to 30 nm. 50 However, if it is less than 3 nm, the photocatalytic activity may be insufficient, and if it exceeds 50 nm, the dispersion and the photocatalytic thin film obtained from the dispersion may become opaque. In addition, the 90% cumulative distribution diameter (D 90 ) are each preferably 5 to 100 nm, more preferably 5 to 80 nm. 90 However, if it is less than 5 nm, the photocatalytic activity may be insufficient, and if it exceeds 100 nm, the dispersion and the photocatalytic thin film obtained from the dispersion may become opaque. The dispersed particle size of a mixture of titanium oxide particles and metal particles can be measured using an apparatus such as ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.), Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.), or LA-910 (manufactured by Horiba, Ltd.).

[0022] ·Aqueous dispersion medium Although water is preferably used as the aqueous dispersion medium, a mixed solvent of water and a hydrophilic organic solvent mixed with water at any ratio may also be used. Examples of water that are preferred include purified water such as filtered water, deionized water, distilled water, and pure water. Examples of hydrophilic organic solvents that are preferred include 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. When a mixed solvent is used, the proportion 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 even more preferably 10% by mass or less.

[0023] i) Titanium oxide particles having a surface modified with a tin component and a transition metal component that enhances visible light activity, but not with an iron component or a silicon component. The titanium oxide particle component i) contained in the titanium oxide particle / metal particle dispersion of the present invention contains titanium oxide particles in which a tin component and a transition metal that enhances visible light activity are solid-solved, as well as iron and silicon components. The iron and silicon components are modified on the surface of the titanium oxide particles, but some of the iron and silicon components may be free in the dispersion. Here, modification refers to the process of attaching various components to a solid surface through reaction and adsorption, with the aim of changing the properties of the solid surface or imparting new functions. The titanium oxide particle component i) is preferably blended in the titanium oxide particle / metal particle dispersion of the present invention as a titanium oxide particle dispersion.

[0024] The titanium oxide particles are titanium oxide used as a photocatalyst, in which a tin component and a transition metal component that enhances visible light activity are dissolved as a solid solution, and the surface is modified with an iron component and a silicon component.

[0025] Although three types of crystalline phases are generally known for titanium oxide particles: rutile, anatase, and brookite, the titanium oxide particles of the present invention are preferably mainly of the anatase or rutile type. Here, "mainly" means that titanium oxide particles of this crystalline phase account for 50% by mass or more of the entire titanium oxide particles, preferably 70% by mass or more, more preferably 90% by mass or more, and may even be 100% by mass.

[0026] In this specification, the term "solid solution" refers to a phase in which atoms at the lattice points of a certain crystal phase are replaced with other atoms, or other atoms enter the lattice gaps, i.e., a mixed phase in which another substance is considered to have dissolved into a certain crystal phase, and refers to a homogeneous crystalline phase. A solid solution in which solvent atoms at the lattice points are replaced with solute atoms is called a substitutional solid solution, and a solid solution in which solute atoms enter the lattice gaps is called an interstitial solid solution, and in this specification, both of these are referred to.

[0027] The titanium oxide particles contained in the dispersion liquid form a solid solution with tin atoms and transition metal atoms. The solid solution may be substitutional or interstitial. A substitutional solid solution of titanium oxide is formed when the titanium sites of titanium oxide crystals are substituted with various metal atoms, while an interstitial solid solution of titanium oxide is formed when various metal atoms enter the lattice gaps of titanium oxide crystals. When various metal atoms are dissolved in titanium oxide, when the crystalline phase is measured by X-ray diffraction or the like, only the peak of the crystalline phase of titanium oxide is observed, and no peaks of compounds derived from the various metal atoms added are observed.

[0028] The method for dissolving a different metal in a metal oxide crystal is not particularly limited, but examples include gas phase methods (CVD, PVD, etc.), liquid phase methods (hydrothermal, sol-gel, etc.), and solid phase methods (high-temperature calcination, etc.).

[0029] The tin component dissolved in the titanium oxide particles may be any tin compound, such as tin metal (Sn), oxides (SnO, SnO), hydroxides, chlorides (SnCl, SnCl), nitrates (Sn(NO), sulfates (SnSO), halogenides (Br, I) other than chlorides, oxoacid salts (NaSnO, KSnO), and complex compounds. These compounds may be used alone or in combination. Among these, oxides (SnO, SnO), chlorides (SnCl, SnCl), sulfates (SnSO), and oxoacid salts (NaSnO, KSnO) are preferred.

[0030] The amount of tin component dissolved in the titanium oxide particles is preferably 1 to 1,000 in terms of the molar ratio to titanium oxide (TiO2 / Sn), more preferably 5 to 500, and even more preferably 5 to 100. This is because if the molar ratio is less than 1, the titanium oxide content decreases and the photocatalytic effect is not fully exerted, and if it exceeds 1,000, the visible light responsiveness may be insufficient.

[0031] The transition metals that dissolve in titanium oxide particles and enhance visible light activity include, for example, vanadium, chromium, manganese, niobium, molybdenum, rhodium, tungsten, and cerium from Groups 3 to 11 of the periodic table, with molybdenum, tungsten, and vanadium being preferred. Therefore, iron, a transition metal, is not included in the transition metals that enhance visible light activity. On the other hand, silicon modifies the surface of titanium oxide particles but does not dissolve in the titanium oxide particles. In other words, the titanium oxide particles (i) contained in the titanium oxide particle / metal particle composition of the present invention do not contain iron or silicon components in solid solution.

[0032] The transition metal component dissolved in the titanium oxide particles may be any component derived from the transition metal compound, and examples thereof include metals, oxides, hydroxides, chlorides, nitrates, sulfates, halides (Br, I) other than chlorides, oxoacid salts, and various complex compounds, and one or more of these may be used.

[0033] The amount of the transition metal component dissolved in the titanium oxide particles can be appropriately selected depending on the type of transition metal component, but the molar ratio to titanium oxide (TiO2 / transition metal) is preferably 1 to 10,000.

[0034] The transition metal to be dissolved may be selected from those listed above. In particular, when molybdenum is selected as the transition metal component to be dissolved in titanium oxide particles, the molybdenum component may be derived from a molybdenum compound, such as molybdenum metal (Mo), oxides (MoO, MoO), hydroxides, chlorides (MoCl, MoCl), nitrates, sulfates, halides (Br, I) other than chlorides, molybdic acid (oxoacid) and its salts (HMoO, NaMoO, KMoO), and complex compounds, or a combination of two or more of these. Among these, oxides (MoO, MoO), chlorides (MoCl, MoCl), and oxoacid and its salts (HMoO, NaMoO, KMoO) are preferred.

[0035] The amount of molybdenum component dissolved in the titanium oxide particles is preferably in a molar ratio to titanium oxide (TiO2 / Mo) of 1 to 10,000, more preferably 5 to 5,000, and even more preferably 20 to 1,000. This is because if the molar ratio is less than 1, the titanium oxide content decreases and the photocatalytic effect may not be fully exerted, while if it exceeds 10,000, the visible light responsiveness may be insufficient.

[0036] When tungsten is selected as the transition metal component to be dissolved in titanium oxide particles, the tungsten component may be derived from a tungsten compound, such as tungsten metal (W), oxide (WO), hydroxide, chloride (WCl, WCl), nitrate, sulfate, halide (Br, I) compound other than chloride, tungsten acid and oxoacid salts (HWO, NaWO, KWO), complex compounds, etc., and one or more of these may be used in combination. Among these, the oxide (WO), chloride (WCl, WCl), and oxoacid salts (NaWO, KWO) are preferably used.

[0037] The amount of tungsten component dissolved in the titanium oxide particles is preferably in a molar ratio to titanium oxide (TiO2 / W) of 1 to 10,000, more preferably 5 to 5,000, and even more preferably 20 to 2,000. This is because if the molar ratio is less than 1, the titanium oxide content will decrease and the photocatalytic effect may not be fully exerted, while if it exceeds 10,000, the visible light responsiveness may be insufficient.

[0038] When vanadium is selected as the transition metal component to be dissolved in titanium oxide particles, the vanadium component may be derived from a vanadium compound, such as vanadium metal (V), oxides (VO, VO, VO, VO), hydroxide, chloride (VCl), oxychloride (VOCl), nitrate, sulfate, oxysulfate (VOSO), halide (Br, I) compounds other than chloride, oxoacid salts (NaVO, KVO, KVO), complex compounds, etc., and one or more of these may be used in combination. Among these, oxides (VO, VO), chlorides (VCl), oxychlorides (VOCl), oxysulfates (VOSO), and oxoacid salts (NaVO, KVO, KVO) are preferred.

[0039] The amount of vanadium component dissolved in the titanium oxide particles is preferably in a molar ratio to titanium oxide (TiO2 / V) of 1 to 10,000, more preferably 10 to 10,000, and even more preferably 100 to 10,000. This is because if the molar ratio is less than 1, the titanium oxide content decreases and the photocatalytic effect may not be fully exerted, and if it exceeds 10,000, the visible light responsiveness may be insufficient.

[0040] The transition metal components dissolved in the titanium oxide particles may be selected from molybdenum, tungsten, and vanadium, and the amount of each component may be selected within the above ranges, provided that the molar ratio of the total amount of each component to titanium oxide [TiO2 / (Mo+W+V)] is 1 or more and less than 10,000.

[0041] The titanium oxide particles may be used alone or in combination of two or more. When two or more types with different visible light responsiveness are combined, the effect of increasing visible light activity may be obtained.

[0042] The iron and silicon components modifying the surface of the titanium oxide particles enhance the visible light response of the photocatalytic thin film.

[0043] The iron component is used to enhance the visible light responsiveness of the photocatalytic thin film, and may be any compound derived from an iron compound, such as 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., and one or more of these may be used in combination.

[0044] The content of the iron component (as oxide) is preferably a mass ratio to titanium oxide (TiO2 / Fe2O3) of 10 to 100,000, more preferably 20 to 10,000, and even more preferably 50 to 1,000. This is because if the mass ratio is less than 10, the titanium oxide particles may aggregate and precipitate, reducing the quality of the resulting photocatalytic thin film and preventing the photocatalytic effect from being fully exerted, while if it exceeds 100,000, the visible light responsiveness may be insufficient.

[0045] The silicon component prevents deterioration of the quality of the photocatalytic thin film and suppresses a decrease in the photocatalytic effect by suppressing aggregation and precipitation of the titanium oxide and iron component when the iron component is added. The silicon component may be derived from a silicon compound. Examples of silicon compounds include metal silicon (Si), oxides (SiO, SiO), alkoxides (Si(OCH), Si(OCH, Si(OCH)), silicates (sodium salts, potassium salts), and activated silicic acid obtained by removing at least a portion of the sodium, potassium, and other ions from these silicates. One or more of these may be used in combination. Among these, silicates (sodium silicate) and activated silicic acid, especially activated silicic acid, are preferred.

[0046] The content of the silicon component (as oxide) is preferably a mass ratio to titanium oxide (TiO2 / SiO2) of 1 to 10,000, more preferably 2 to 5,000, and even more preferably 5 to 1,000. This is because if the mass ratio is less than 1, the titanium oxide content decreases and the photocatalytic effect may not be fully exerted, and if it exceeds 10,000, the effect of suppressing the aggregation and precipitation of titanium oxide may be insufficient.

[0047] In addition to the iron and silicon components, the titanium oxide particles may be surface-modified with a titanium component to further enhance the photocatalytic activity of the photocatalytic thin film. The titanium component, which further enhances the photocatalytic activity of the photocatalytic thin film, may be any titanium compound, such as titanium metal (Ti), hydroxide (Ti(OH)4), oxyhydroxide (TiO(OH)2), chloride (TiCl4, TiCl3, TiCl2), nitrate (Ti(NO)4), sulfate (Ti(SO4)2, TiOSO4), halogen compounds (Br, I) other than chloride, and complex compounds. These compounds may be used alone or in combination of two or more.

[0048] The content of the titanium component (in terms of oxide) is preferably a mass ratio to titanium oxide (TiO2 (titanium oxide particles) / TiO2 (modifying component)) of 10 to 100,000, more preferably 20 to 10,000, and even more preferably 50 to 1,000. This is because if the mass ratio is less than 10, the titanium oxide may aggregate and precipitate, resulting in a decrease in the quality of the obtained photocatalytic thin film and insufficient photocatalytic effect, while if it exceeds 100,000, the effect of enhancing activity may be insufficient.

[0049] Although water is preferably used as the aqueous dispersion medium for the titanium oxide particle dispersion, a mixed solvent of water and a hydrophilic organic solvent, which can be mixed with water in any ratio, may also be used. Examples of water that are preferred include purified water such as filtered water, deionized water, distilled water, and pure water. Examples of hydrophilic organic solvents that are preferred include 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. When a mixed solvent is used, the proportion 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 even more preferably 10% by mass or less.

[0050] The titanium oxide particles in the titanium oxide particle dispersion liquid, in which tin and a transition metal component that enhances visible light activity are dissolved in a solid solution and the surface is modified with iron and silicon components, have a volume-based 50% cumulative distribution diameter (hereinafter referred to as D 50 The thickness of the film is preferably 3 to 50 nm, more preferably 3 to 40 nm, and even more preferably 3 to 30 nm. 50 However, if it is less than 3 nm, the photocatalytic activity may be insufficient, and if it exceeds 50 nm, the dispersion and the photocatalytic thin film obtained from the dispersion may become opaque.

[0051] In addition, the 90% cumulative distribution diameter (hereinafter referred to as D 90and ) are each preferably 5 to 100 nm, more preferably 5 to 80 nm. 90 However, if it is less than 5 nm, the photocatalytic activity may be insufficient, and if it exceeds 100 nm, the dispersion and the photocatalytic thin film obtained from the dispersion may become opaque.

[0052] Titanium oxide particles are D 50 and D 90 It is preferable that the particle has a molecular weight within the above range, since it has high photocatalytic activity and provides a highly transparent dispersion and a photocatalytic thin film obtained from the dispersion. In addition, the D of the titanium oxide particles in the titanium oxide particle dispersion liquid 50 and D 90 As an apparatus for measuring this, for example, ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.), Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.), LA-910 (manufactured by Horiba Ltd.), etc. can be used.

[0053] The concentration of titanium oxide particles in the dispersion of titanium oxide particles 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 of the required thickness.

[0054] ii) Metal particles containing antibacterial metals The metal particle component ii) contained in the dispersion of titanium oxide particles and metal particles of the present invention is a metal component containing at least one metal component that enhances antibacterial properties. Metal components that enhance antibacterial properties refer to metal components that are harmful to microorganisms such as bacteria and mold but relatively harmless to the human body, and examples thereof include silver, copper, zinc, platinum, palladium, nickel, aluminum, titanium, cobalt, zirconium, molybdenum, and tungsten, which have been confirmed to reduce the viable counts of Staphylococcus aureus and Escherichia coli when coated with metal component particles on a film and subjected to the JIS Z 2801 standard test for antibacterial processed products. Particularly preferred metal components that enhance antibacterial properties include at least one metal selected from silver, copper, and zinc.

[0055] The metal particle component ii) is preferably blended in the titanium oxide particle / metal particle dispersion of the present invention as a metal particle dispersion. These metal components that enhance antibacterial properties can be used as they are or as a solution thereof added to titanium oxide particles, but adding the metal components themselves or a solution thereof to titanium oxide particles that have been surface-modified to enhance their activity reduces the effect of enhancing the photocatalytic activity. To prevent this, it is preferable to add separately prepared metal particles to the titanium oxide particles, and it is more preferable to adsorb a protective agent to the surface of the metal particles.

[0056] The metal particles are metal particles containing at least one of these metals, and may be alloy particles containing two or more metals.

[0057] Examples of alloy particles include alloy particles containing a combination of metal components such as silver-copper, silver-palladium, silver-platinum, silver-tin, gold-copper, silver-nickel, silver-antimony, silver-copper-tin, gold-copper-tin, silver-nickel-tin, silver-antimony-tin, platinum-manganese, silver-titanium, copper-tin, cobalt-copper, zinc-magnesium, silver-zinc, copper-zinc, and silver-copper-zinc.

[0058] The metal components other than the metal components that enhance the antibacterial properties of the metal particles are not particularly limited, and can be selected from at least one of, for example, gold, antimony, tin, sodium, magnesium, silicon, potassium, calcium, scandium, vanadium, chromium, manganese, iron, gallium, germanium, arsenic, selenium, yttrium, niobium, technetium, ruthenium, rhodium, indium, tellurium, cesium, barium, hafnium, tantalum, rhenium, osmium, iridium, mercury, thallium, lead, bismuth, polonium, radium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, actinium, and thorium.

[0059] The content of the antibacterial metal component in the metal particles can be 1 to 100 mass %, preferably 10 to 100 mass %, and more preferably 50 to 100 mass %, of the antibacterial metal relative to the total mass of the metal particles, because if the antibacterial metal component is less than 1 mass %, the antibacterial performance may not be fully exhibited.

[0060] The protective agent for metal particles is not particularly limited as long as it adsorbs to the surface of the metal particles to stabilize them and prevents the reduction-precipitated metal particles from agglomerating and enlarging, and prevents the antibacterial metal from reducing the effect of enhancing the photocatalytic activity of the iron and silicon components modified on the titanium oxide particles. Organic compounds capable of acting as surfactants or dispersants can be used. Furthermore, those exhibiting reducing properties can also serve as reducing agents, as described below. Examples of protective agents for metal particles include surfactants such as anionic surfactants, cationic surfactants, and nonionic surfactants; water-soluble polymers such as polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyethyleneimine, polyethylene oxide, polysulfonic acid, polyacrylic acid, and methylcellulose; aliphatic amine compounds such as ethanolamine, diethanolamine, triethanolamine, and propanolamine; butylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, 3-butoxypropylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadecylamine, and the like. The surfactant can be selected from at least one of the following: primary amine compounds such as amine, oleylamine, and octadecylamine; diamine compounds such as N,N-dimethylethylenediamine and NN-diethylethylenediamine; sulfonic acid compounds such as mercaptosulfonic acid and toluenesulfonic acid; carboxylic acid compounds such as mercaptoacetic acid, citric acid, stearic acid, and oleic acid; bromides such as hexatrimethylammonium bromide, tetrabutylammonium bromide, dodecyltrimethylammonium bromide, and tetradecyltrimethylammonium bromide; aliphatic thiol compounds such as dodecanethiol; and polyphenols such as flavonoids and phenolic acids.

[0061] The content of the protective agent is preferably 0.01 to 100, more preferably 0.05 to 20, in terms of the mass ratio to the metal particles (metal particles / protective agent adsorbed on the surface of the metal particles). This is because if the mass ratio is less than 0.01, the content of metal particles will be reduced and the antibacterial effect may not be fully exerted, and if it exceeds 100, the protective effect of the metal particles will be insufficient, which may result in aggregation and enlargement of the metal particles or a decrease in photocatalytic activity. The content of the protective agent can be measured by the method described below.

[0062] The aqueous dispersion medium for the metal particle dispersion liquid is typically an aqueous solvent, and preferably water, a water-miscible water-soluble organic solvent, or a mixture of water and a water-soluble organic solvent. Examples of water include deionized water, distilled water, and pure water. Examples of water-soluble organic solvents include alcohols such as methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, ethylene glycol, diethylene glycol, and polyethylene glycol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and propylene glycol-n-propyl ether; ketones such as acetone and methyl ethyl ketone; water-soluble nitrogen-containing compounds such as 2-pyrrolidone and N-methylpyrrolidone; and ethyl acetate. These may be used alone or in combination.

[0063] The average particle size of metal particles in a metal particle dispersion is the 50% cumulative distribution diameter (D 50) is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 70 nm or less. There are no particular restrictions on the lower limit of the average particle size, and theoretically, particles up to the smallest particle size that can have antibacterial properties can be used, but in practice, it is preferably 1 nm or more. Furthermore, if the average particle size exceeds 200 nm, the dispersion and the photocatalytic thin film obtained from the dispersion may become opaque, which is not preferable.

[0064] In addition, the 90% cumulative distribution diameter (D 90 ) is preferably 1,000 nm, more preferably 500 nm or less, and even more preferably 200 nm or less. 90 The lower limit of D is not particularly limited, but is preferably 1 nm or more in practical use. 90 If the diameter exceeds 1,000 nm, the dispersion and the photocatalytic thin film obtained from the dispersion may become opaque, which is undesirable.

[0065] As a device for measuring the average particle size, for example, ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.), Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.), LA-910 (manufactured by Horiba, Ltd.), etc. can be used.

[0066] The concentration of metal particles in the metal particle dispersion is not particularly limited, but since a lower concentration generally leads to better dispersion stability, it is preferably 0.0001 to 10% by mass, more preferably 0.001 to 5% by mass, and even more preferably 0.01 to 1% by mass. If the concentration is less than 0.0001% by mass, productivity will be significantly reduced, which is not preferred.

[0067] ·binder Furthermore, a binder may be added to the titanium oxide particle / metal particle dispersion liquid to facilitate application of the dispersion liquid to the surfaces of various components described below and to facilitate adhesion of the particles. Examples of binders include metal compound binders containing silicon, aluminum, titanium, zirconium, etc., and organic resin binders containing fluorine-based resins, acrylic resins, urethane resins, etc.

[0068] The mass ratio of the binder to the titanium oxide particles and metal particles [(titanium oxide particles + metal particles) / 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 because if the mass ratio exceeds 99, the adhesion of the titanium oxide particles to the surfaces of various components becomes insufficient, and if it is less than 0.01, the photocatalytic activity may become insufficient.

[0069] Among these, to obtain an excellent photocatalytic thin film with high photocatalytic activity and transparency, it is preferable to add and use a silicon compound binder in a mass ratio (titanium oxide + metal particles / silicon compound binder) of 99 to 0.01, more preferably 9 to 0.1, and even more preferably 2.5 to 0.4. Here, the silicon compound binder refers to a colloidal dispersion, solution, or emulsion of a silicon compound containing a solid or liquid silicon compound in an aqueous dispersion medium, and specific examples include colloidal silica (preferably particle size 1 to 150 nm); silicate solutions such as silicates; silane and siloxane hydrolyzate emulsions; silicone resin emulsions; and emulsions of copolymers of silicone resins with other resins, such as silicone-acrylic resin copolymers and silicone-urethane resin copolymers.

[0070] <Method of manufacturing titanium oxide particle / metal particle dispersion> The titanium oxide particle / metal particle dispersion of the present invention is obtained by dispersing two types of particles in an aqueous dispersion medium: i) titanium oxide particles that are surface-modified and contain a tin component and a transition metal component that enhances visible light activity, but do not contain iron or silicon components, and ii) metal particles that contain an antibacterial metal. The production method thereof can be, for example, a method comprising the following steps (1) to (8).

[0071] (1) A step of producing a peroxotitanic acid solution containing a tin component and a transition metal component from raw material titanium compounds, tin compounds, transition metal compounds, basic substances, hydrogen peroxide, and an aqueous dispersion medium. (2) A step of heating the tin component and transition metal component peroxotitanate solution produced in the above step (1) at 80 to 250°C under pressure control to obtain a titanium oxide particle dispersion liquid in which the tin component and the transition metal component are solid-dissolved. (3) A step of producing a solution or dispersion of an iron component and a silicon component from an iron compound, a silicon compound, and an aqueous dispersion medium. (4) A step of mixing the titanium oxide particle dispersion liquid produced in the above step (2) with the solution or dispersion liquid of iron and silicon components produced in the step (3) to obtain a dispersion liquid whose surfaces are modified with iron and silicon components. (5) A step of producing a solution containing the raw antibacterial metal compound and a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (6) A step of producing a metal particle dispersion by mixing the solution containing the raw antibacterial metal compound produced in the step (5) with a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (7) A step of washing the metal particle dispersion liquid produced in the above step (6) with an aqueous dispersion medium by membrane filtration. (8) A step of mixing the titanium oxide particle dispersion liquid and the metal particle dispersion liquid obtained in the steps (4) and (7).

[0072] Steps (1) to (4) are for producing a dispersion of titanium oxide particles in which a tin component and a transition metal component are dissolved as a solid solution and whose surfaces are modified with an iron component and a silicon component. Steps (5) to (7) are used to produce a metal particle dispersion. While physical and chemical methods exist, the liquid-phase reduction method is one of the chemical methods that offers advantages in terms of productivity, including ease of adjusting synthesis conditions, wide controllability over the composition, particle size, and particle size distribution, and is characterized by its ease of productivity. The liquid-phase reduction method involves mixing a reducing agent into a solution containing the raw metal ions, causing them to precipitate as metal particles. The inclusion of a metal particle protective agent in the reaction system makes it easier to improve the dispersibility of the metal particles in the solvent, control particle size, and prevent a decrease in photocatalytic activity when mixed with titanium oxide particles. In step (8), the titanium oxide particle dispersion liquid obtained in step (4), in which the tin component and the transition metal component are solid-dissolved and whose surfaces are modified with the iron component and the silicon component, is mixed with the metal particle dispersion liquid containing the antibacterial metal obtained in step (7), to finally produce a titanium oxide particle / metal particle dispersion liquid. Each step will be described in detail below.

[0073] <Method for producing a dispersion of titanium oxide particles having a tin component and a transition metal component dissolved therein and having their surfaces modified with an iron component and a silicon component> A method for producing a titanium oxide particle dispersion liquid in which a tin component and a transition metal component are dissolved and which is surface-modified with an iron component and a silicon component includes producing a titanium oxide particle dispersion liquid in which a tin component and a transition metal component are dissolved and a solution or dispersion of an iron component and a silicon component, respectively, and mixing the titanium oxide particle dispersion liquid in which a tin component and a transition metal component are dissolved with the solution or dispersion of an iron component and a silicon component.

[0074] A specific example of a method for producing a titanium oxide particle dispersion liquid in which a tin component and a transition metal component are dissolved and whose surfaces are modified with an iron component and a silicon component includes 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 raw material titanium compounds, tin compounds, transition metal compounds, basic substances, hydrogen peroxide, and an aqueous dispersion medium. (2) A step of heating the peroxotitanic acid solution containing the tin component and the transition metal component produced in the above step (1) at 80 to 250°C under pressure control to obtain a titanium oxide particle dispersion liquid. (3) A step of producing a solution or dispersion of an iron component and a silicon component from an iron compound, a silicon compound, and an aqueous dispersion medium. (4) A step of mixing the titanium oxide particle dispersion liquid containing the tin component and the transition metal component in a solid solution produced in the step (2) with the solution or dispersion liquid of the iron component and the silicon component produced in the step (3) to obtain a titanium oxide particle dispersion liquid whose surfaces are modified with the iron component and the silicon component.

[0075] When the surface of the titanium oxide particles is further modified with a titanium component in order to further enhance the photocatalytic activity of the photocatalytic thin film, a titanium oxide particle dispersion liquid whose surface is modified with an iron component, a silicon component, and a titanium component can be obtained in the same manner as above, except that a titanium compound is further added in step (3).

[0076] Steps (1) and (2) are steps for obtaining a dispersion of titanium oxide particles in which a tin component and a transition metal component are dissolved, step (3) is a step for obtaining a solution or dispersion of an iron component and a silicon component, and step (4) is a step for obtaining a dispersion containing titanium oxide particles in which a tin component and a transition metal component are dissolved and whose surfaces are modified with an iron component and a silicon component.

[0077] ·Process (1): In step (1), a peroxotitanic acid solution containing a tin component and a transition metal component is produced by reacting raw materials, such as a titanium compound, a tin compound, a transition metal compound, a basic substance, and hydrogen peroxide, in an aqueous dispersion medium.

[0078] The reaction method may be any of the following methods i) to iii). i) A method in which a tin compound and a transition metal compound are added to and dissolved in a raw material titanium compound and a basic substance in an aqueous dispersion medium, and then titanium hydroxide containing tin and transition metal components is obtained, impurity ions other than the contained metal ions are removed, and hydrogen peroxide is added to obtain peroxotitanic acid containing tin and transition metal components. 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, and after removing impurity ions other than the contained metal ions, a tin compound and a transition metal compound are added, and then hydrogen peroxide is added to form a 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, impurity 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 form peroxotitanic acid containing a tin component and a transition metal component.

[0079] In the first step of method i), the "raw material titanium compound and basic substance in an aqueous dispersion medium" may be separated into two aqueous dispersion media, such as "an aqueous dispersion medium in which the raw material titanium compound is dispersed" and "an aqueous dispersion medium in which the basic substance is dispersed," and the tin compound and the transition metal compound may be dissolved in one or both of the two liquids according to the solubility of each compound in the two liquids, and then the two may be mixed.

[0080] After obtaining peroxotitanic acid containing a tin component and a transition metal component in this manner, it is possible to obtain titanium oxide particles in which the various metals are dissolved in titanium oxide as a solid solution by subjecting the peroxotitanic acid to the hydrothermal reaction in step (2) described below.

[0081] Examples of the raw titanium compound include inorganic acid salts such as titanium chloride, nitrate, and sulfate, 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 of these to hydrolyze the solution. One or more of these may be used in combination. Among these, titanium chlorides (TiCl3, TiCl4) are preferably used.

[0082] The tin compound, transition metal compound, and aqueous dispersion medium are used in the above-mentioned proportions. The concentration of the aqueous solution of the starting titanium compound formed from the starting titanium compound and the aqueous dispersion medium is preferably 60% by mass or less, and more preferably 30% by mass or less. The lower limit of the concentration can be selected as appropriate, but is usually preferably 1% by mass or more.

[0083] The basic substance is used to smoothly convert the starting titanium compound into titanium hydroxide, and examples thereof include alkali metal or alkaline earth metal hydroxides such as sodium hydroxide and potassium hydroxide, ammonia, and amine compounds such as alkanolamines and alkylamines, with ammonia being particularly preferred and added in an amount such that the pH of the aqueous starting titanium compound solution becomes 7 or higher, particularly 7 to 10. The basic substance may be used together with the aqueous dispersion medium in an appropriate concentration to form an aqueous solution.

[0084] Hydrogen peroxide is used to convert the starting titanium compound or titanium hydroxide into peroxotitanium, i.e., a titanium oxide compound containing Ti-OO-Ti bonds, and is usually used in the form of aqueous hydrogen peroxide. The amount of hydrogen peroxide added is preferably 1.5 to 20 times the molar amount of Ti or the total molar amount of Ti, transition metal, and Sn. In addition, in the reaction of converting the starting titanium compound or titanium hydroxide into peroxotitanic acid by adding hydrogen peroxide, the reaction temperature is preferably 5 to 80°C, and the reaction time is preferably 30 minutes to 24 hours.

[0085] The thus obtained peroxotitanic acid solution containing a tin component and a transition metal component may contain an alkaline or acidic substance for pH adjustment, etc. Examples of alkaline substances include ammonia, sodium hydroxide, calcium hydroxide, and alkylamines, while 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 viewpoint of safety in handling.

[0086] ·Process (2): In step (2), the peroxotitanic acid solution containing the tin component and the transition metal component obtained in step (1) is subjected to a hydrothermal reaction under pressure control at a temperature of 80 to 250°C, preferably 100 to 250°C, for 0.01 to 24 hours. From the viewpoints of reaction efficiency and reaction control, a reaction temperature of 80 to 250°C is appropriate. 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. Note that "under pressure control" here refers to applying appropriate pressure to maintain the reaction temperature when the reaction temperature exceeds the boiling point of the dispersion medium. This also includes controlling the reaction temperature at atmospheric pressure when the temperature is below the boiling point of the dispersion medium. The pressure used here is typically 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. By this step (2), a titanium oxide particle dispersion liquid in which the tin component and the transition metal component are dissolved is obtained. The pH of the titanium oxide particle dispersion liquid containing the tin component and the transition metal component dissolved therein obtained in step (2) is preferably 7 to 14, and more preferably 9 to 14. The titanium oxide particle dispersion liquid containing the tin component and the transition metal component dissolved therein obtained in step (2) may contain an alkaline substance or an acidic substance for adjusting the pH to the aforementioned pH, and the alkaline substance, acidic substance, and pH adjustment method are the same as those for the tin component and transition metal component-containing peroxotitanic acid solution obtained in step (1) described above.

[0087] The particle diameter of the titanium oxide particles obtained here (D 50 and D 90 ) is preferably in the range as already described, and the particle diameter can be controlled by adjusting the reaction conditions. For example, the particle diameter can be reduced by shortening the reaction time or the temperature rise time.

[0088] ·Process (3): In step (3), separate from steps (1) and (2), a solution or dispersion of the iron component and the silicon component is produced by dissolving or dispersing a raw material iron compound and a raw material silicon compound in an aqueous dispersion medium.

[0089] Examples of the raw iron compound include the above-mentioned iron compounds, such as 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, and complex compounds. These compounds may be used alone or in combination of two or more. Among these, the oxides (Fe2O3, Fe3O4), oxyhydroxides (FeO(OH)), chlorides (FeCl2, FeCl3), nitrates (Fe(NO)3), and sulfates (FeSO4, Fe2(SO4)3) are preferably used.

[0090] Examples of the starting silicon compound include the silicon compounds described above, such as metal silicon (Si), oxides (SiO, SiO), alkoxides (Si(OCH), Si(OCH), Si(OCH(CH)), silicates (sodium salts, potassium salts), and activated silicic acid obtained by removing ions such as sodium and potassium from these silicates. These may be used alone or in combination of two or more. Among these, silicates (sodium silicate) and activated silicic acid are preferably used. Activated silicic acid can be obtained, for example, by adding a cation exchange resin to an aqueous sodium silicate solution prepared by dissolving sodium silicate in pure water to remove at least a portion of the sodium ions. The cation exchange resin is preferably added so that the pH of the resulting activated silicic acid solution is 2 to 10, preferably 2 to 7.

[0091] The iron component and silicon component-containing solution or dispersion thus obtained may also contain alkaline or acidic substances for pH adjustment, etc., and the alkaline and acidic substances and pH adjustment referred to here can be handled in the same manner as described above. The pH of the solution or dispersion containing the iron component and the silicon component is preferably 1-7, and more preferably 1-5.

[0092] The concentration of the raw material iron compound in the solution or dispersion of the iron component and silicon component produced in step (3) is preferably 0.001 to 10 mass%, more preferably 0.01 to 5 mass%, and the concentration of the raw material silicon compound is preferably 0.001 to 10 mass%, more preferably 0.01 to 5 mass%.

[0093] The solution or dispersion of the iron component and silicon component may further contain a titanium component dissolved or dispersed therein.

[0094] When a titanium component is to be contained, examples of the raw titanium compound include the titanium compounds described above, such as titanium metal (Ti), hydroxide (Ti(OH)), oxyhydroxide (TiO(OH)), chloride (TiCl, TiCl, TiCl), nitrate (Ti(NO)), sulfate (Ti(SO), TiOSO), halogen compounds (Br, I) other than chloride, complex compounds, and peroxotitanium compounds (titanium oxide compounds containing Ti-OO-Ti bonds). One or more of these compounds may be used in combination. Among these, hydroxide (Ti(OH)), oxyhydroxide (TiO(OH)), chloride (TiCl, TiCl, TiCl), nitrate (Ti(NO), sulfate (Ti(SO), TiOSO), and peroxotitanium compounds (titanium oxide compounds containing Ti-OO-Ti bonds) are preferred.

[0095] ·Process (4): In step (4), the titanium oxide particle dispersion obtained in step (2) is mixed with the solution or dispersion of the iron and silicon components obtained in step (3). The mixing method is not particularly limited, and 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, and more preferably 20 to 40°C, and the time is preferably 1 minute to 3 hours. The mixing ratio may be such that the mass ratio of TiO2 to Fe and Si oxides (Fe2O3 and SiO2) in the titanium oxide particle dispersion is as described above.

[0096] The titanium oxide particle dispersion obtained in the above steps (1) to (4) may contain an alkaline or acidic substance for pH adjustment, etc., and the pH adjusters described above can be used. In addition, ion exchange treatment or filtration and washing treatment may be performed to adjust the ion component concentration, or solvent substitution treatment may be performed to change the solvent component. The pH of the titanium oxide particle dispersion is preferably 7 to 14, and more preferably 8 to 12.

[0097] The mass of titanium oxide particles contained in a titanium oxide particle dispersion can be calculated from the mass and concentration of the titanium oxide particle dispersion. The concentration of the titanium oxide particle dispersion can be measured by sampling a portion of the titanium oxide particle dispersion and heating it at 105°C for 1 hour to volatilize the solvent, and then calculating the concentration from the mass of the non-volatile content (titanium oxide particles) and the mass of the sampled titanium oxide particle dispersion according to the following formula: Titanium oxide particle dispersion concentration (%) = [mass of nonvolatile matter (g) / mass of titanium oxide particle dispersion (g)] × 100

[0098] <Method for producing a metal particle dispersion containing an antibacterial metal> The method for producing a metal particle dispersion containing an antibacterial metal is to mix a solution containing an antibacterial metal compound with a solution containing a reducing agent and a protecting agent to obtain a metal particle dispersion, and then to remove and purify components other than the metal particles using a membrane filtration method.

[0099] A specific example of a method for producing a metal particle dispersion liquid containing an antibacterial metal is a production method including the following steps (5) to (7).

[0100] (5) A step of producing a solution containing the raw antibacterial metal compound and a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (6) A step of producing a metal particle dispersion by mixing the solution containing the raw antibacterial metal compound produced in the step (5) with a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (7) A step of washing the metal particle dispersion liquid produced in the above step (6) with an aqueous dispersion medium by membrane filtration.

[0101] In addition, when the metal particles are alloy particles consisting of multiple metals, a dispersion of alloy particles consisting of multiple metals can be obtained in the same manner as above, except that in step (5) above, a metal compound is further added to the solution containing the raw antibacterial metal compound.

[0102] ·Process (5): In step (5), a solution in which the raw antibacterial metal compound is dissolved in an aqueous dispersion medium and a solution in which a reducing agent for reducing the raw antibacterial metal compound is dissolved in an aqueous dispersion medium are produced.

[0103] The method for producing these solutions may be a method in which the raw antibacterial metal compound and a reducing agent for reducing the raw antibacterial metal compound are separately added to an aqueous dispersion medium and stirred to dissolve them. The stirring method is not particularly limited as long as it can dissolve the raw antibacterial metal compound uniformly in the aqueous dispersion medium, and a commonly available stirrer can be used.

[0104] Various antibacterial metal compounds can be used as the raw antibacterial metal compound, including inorganic acid salts such as chlorides, nitrates, and sulfates of antibacterial metals, organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid, and complex salts such as ammine complexes, cyano complexes, halogeno complexes, and hydroxy complexes, and these may be used alone or in combination of two or more. Among these, inorganic acid salts such as chlorides, nitrates, and sulfates are preferably used.

[0105] The reducing agent is not particularly limited, and any of various reducing agents capable of reducing the metal ions constituting the raw antibacterial metal compound can be used. For example, hydrazines such as hydrazine, hydrazine monohydrate, phenylhydrazine, and hydrazinium sulfate; amines such as dimethylaminoethanol, triethylamine, octylamine, dimethylaminoborane, and benzotriazole; organic acids such as citric acid, ascorbic acid, tartaric acid, malic acid, malonic acid, and formic acid; sodium borohydride, lithium borohydride, lithium triethylborohydride, lithium aluminum hydride, diisobutylaluminum hydride, tributyltin hydride, and tri(se) hydride. Examples of suitable aqueous dispersion media include hydrides such as lithium (c-butyl)borohydride, potassium tri(sec-butyl)borohydride, zinc borohydride, and sodium acetoxyborohydride; pyrrolidones such as polyvinylpyrrolidone, 1-vinylpyrrolidone, N-vinylpyrrolidone, and methylpyrrolidone; reducing sugars such as glucose, galactose, mannose, fructose, sucrose, maltose, raffinose, and stachyose; and sugar alcohols such as sorbitol, and these may be used alone or in combination. The aqueous dispersion medium for dissolving the reducing agent may be the same as the aqueous dispersion medium used for the metal compound.

[0106] A protective agent may be added to the solution in which the reducing agent is dissolved in the aqueous dispersion medium. The protective agent is preferably one of the above-mentioned types, and is contained in the above-mentioned mass ratio relative to the metal particles.

[0107] As the aqueous dispersion medium (aqueous solvent), it is preferable to use those described above.

[0108] A basic or acidic substance may be added to the solvent. Examples of basic substances include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates such as sodium carbonate and potassium carbonate, alkali metal bicarbonates such as sodium bicarbonate and potassium bicarbonate, alkali metal alkoxides such as potassium tert-butoxide, sodium methoxide, and sodium ethoxide, alkali metal salts of aliphatic hydrocarbons such as butyllithium, and amines such as triethylamine, diethylaminoethanol, and diethylamine. Examples of acidic substances include inorganic acids such as aqua regia, hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, oxalic acid, trifluoroacetic acid, and trichloroacetic acid.

[0109] The concentrations of these two solutions are not particularly limited. However, since a lower concentration generally tends to result in a smaller primary particle size of the individual metal particles formed, it is preferable to set an appropriate concentration range depending on the target range of primary particle size.

[0110] There are no particular limitations on the pH of these two solutions, and it is preferable to adjust the pH to a suitable value depending on the molar ratio of the metal in the target metal particles, the primary particle size, and the like.

[0111] ·Process (6): In step (6), the solution prepared in step (5) in which the raw antibacterial metal compound is dissolved in an aqueous dispersion medium is mixed with a solution prepared in which a reducing agent for reducing the raw antibacterial metal compound is dissolved in an aqueous dispersion medium to produce a metal particle dispersion liquid.

[0112] The method for mixing these two solutions is not particularly limited as long as it can uniformly mix these two solutions. Examples include a method in which the metal compound solution and the reducing agent solution are placed in a reaction vessel and stirred and mixed; a method in which the reducing agent solution is added dropwise to the metal compound solution placed in a reaction vessel while stirring and mixed; a method in which the metal compound solution is added dropwise to the reducing agent solution placed in a reaction vessel while stirring and mixed; and a method in which the metal compound solution and the reducing agent solution are continuously supplied at fixed amounts and mixed in a reaction vessel or a flow reactor.

[0113] The temperature during mixing is not particularly limited, and it is preferable to adjust the temperature to a suitable value depending on the target primary particle size, reaction time, etc.

[0114] ·Process (7): In step (7), the metal particle dispersion liquid produced in step (6) is washed with an aqueous dispersion medium by membrane filtration.

[0115] The aqueous dispersion medium preferably includes water, a water-miscible water-soluble organic solvent, or a mixture of water and a water-soluble organic solvent. Examples of water include deionized water, distilled water, and pure water. Examples of water-soluble organic solvents include alcohols such as methanol, ethanol, isopropanol, n-propanol, 2-propanol, n-butanol, 2-butanol, tert-butanol, ethylene glycol, and diethylene glycol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and propylene glycol-n-propyl ether; ketones such as acetone and methyl ethyl ketone; water-soluble nitrogen-containing compounds such as 2-pyrrolidone and N-methylpyrrolidone; and ethyl acetate. These water-soluble organic solvents may be used alone or in combination.

[0116] The membrane filtration method is used to wash and separate from the metal particle dispersion any unnecessary nonvolatile components other than the metal particles, such as components other than the metals in the raw metal compound, reducing agents, excess protective agents that are not adsorbed to the surfaces of the metal particles, etc. It is preferable that components other than the metal particles and the protective agents adsorbed to their surfaces are separated from the metal particle dispersion in this step. Washing is preferably carried out until the mass ratio of metal particles with a protective agent adsorbed on their surfaces to other nonvolatile components in the metal particle dispersion (metal particles with a protective agent adsorbed on their surfaces / other nonvolatile components) is 1 or more, more preferably 10 or more, and even more preferably 100 or more. If it is less than 1, the content of metal particles decreases, and the antibacterial effect may not be fully exerted.

[0117] Quantitative determination of metal component concentration in metal particle dispersion (ICP-OES) The metal component (metal particle) concentration C (mass %) in the metal particle dispersion can be measured by appropriately diluting the metal particle dispersion with pure water and introducing it into an inductively coupled plasma optical emission spectrometer (trade name "Agilent 5110 ICP-OES", Agilent Technologies, Inc.).

[0118] Quantitative determination of metal particles with protective agents adsorbed on the surface in metal particle dispersions The mass M2 (g) of the metal particles with the protective agent adsorbed on their surfaces can be calculated as follows: First, the metal particle dispersion liquid is sampled and its mass M1 (g) is measured. Next, the metal particle dispersion liquid with mass M1 (g) is heated at 105°C for 3 hours to volatilize the solvent, and the mass M of the non-volatile matter is measured. a (g) is measured. The mass of the evaporated solvent, S(g), is calculated as S(g) = M1(g) - M a (g). Furthermore, mass M a The non-volatile matter in (g) is dispersed in pure water and washed, and then centrifuged to precipitate the metal particles with the protective agent adsorbed to their surfaces. The supernatant, which contains the non-volatile matter M3(g) other than the metal particles with the protective agent adsorbed to their surfaces, is removed. This process is repeated five times, and the resulting sediment (metal particles with the protective agent adsorbed to their surfaces) is further heated at 105°C for 3 hours, cooled, and its mass M2(g) is measured. Mass M2 (g) of metal particles with protective agent adsorbed on their surface = Mass of sampled metal particle dispersion M1 (g) - solvent S (g) - non-volatile matter other than metal particles with protective agent adsorbed on their surfaces M3 (g)

[0119] Quantitative determination of protective agents adsorbed on the surface of metal particles The mass M4 (g) of the protective agent adsorbed on the surface of the metal particles can be calculated from the metal component concentration C (mass %) determined as described above, the mass M1 (g) of the sampled metal particle dispersion, and the mass M2 (g) of the metal particles with the protective agent adsorbed on their surfaces. Mass of the protective agent adsorbed on the metal particle surface M4 (g) = Mass of metal particles with protective agent adsorbed on their surfaces M2 (g) - [Mass of sampled metal particle dispersion M1 (g) × Metal component concentration C (mass%) ÷ 100]

[0120] Quantitative determination of non-volatile matter other than metal particles with protective agents adsorbed on the surface in metal particle dispersions The mass M3 (g) of non-volatile components other than metal particles with protective agents adsorbed on their surfaces can be calculated from the mass M1 (g) of the sampled metal particle dispersion liquid obtained as described above, the mass S (g) of the solvent, and the mass M2 (g) of the metal particles with protective agents adsorbed on their surfaces. Mass of non-volatile matter other than metal particles with protective agent adsorbed on the surface M3 (g) = Mass of sampled metal particle dispersion M1 (g) - Mass of solvent S (g) - Mass of metal particles with protective agent adsorbed on their surfaces M2 (g)

[0121] The membrane used in the membrane filtration method is not particularly limited as long as it can separate metal particles having a protective agent adsorbed on their surfaces from other non-volatile components from a metal particle dispersion. Examples of the membrane include a microfiltration membrane, an ultrafiltration membrane, and a nanofiltration membrane. Of these, the membrane filtration method can be carried out using a membrane having an appropriate pore size.

[0122] As the filtration method, any of centrifugal filtration, pressure filtration, cross-flow filtration, etc. can be used.

[0123] The shape of the filtration membrane may be any appropriate shape, such as hollow fiber, spiral, tubular, or flat membrane.

[0124] The material of the filtration membrane is not particularly limited as long as it is durable against the metal particle dispersion liquid, and can be appropriately selected from organic membranes such as polyethylene, tetrafluoroethylene, polypropylene, cellulose acetate, polyacrylonitrile, polyimide, polysulfone, and polyethersulfone, and inorganic membranes such as silica, alumina, zirconia, and titania.

[0125] Specific examples of such filtration membranes include Microza (manufactured by Asahi Kasei Chemicals Corporation), Amicon Ultra (manufactured by Merck Millipore Co., Ltd.), Ultrafilter (Advantech Toyo Co., Ltd.), MEMBRALOX (Nippon Pall Co., Ltd.), and Cefilt (NGK Insulators, Ltd.).

[0126] ·Process(8) In step (8), the titanium oxide particle dispersion liquid obtained in step (4), in which the tin component and the transition metal component are solid-dissolved and whose surfaces are modified with the iron component and the silicon component, is mixed with the metal particle dispersion liquid containing the antibacterial metal obtained in step (7), to obtain a titanium oxide particle / metal particle dispersion liquid.

[0127] The mixing method is not particularly limited as long as it is a method that can uniformly mix the two types of dispersion liquids, and for example, they can be mixed by stirring using a commonly available stirrer.

[0128] The mixing ratio of the titanium oxide particle dispersion liquid to the metal particle dispersion liquid, expressed as the mass ratio of the titanium oxide particles to the metal particles in each dispersion liquid (titanium oxide particles / metal particles), is 1 to 100,000, preferably 10 to 10,000, and more preferably 100 to 1,000. If the ratio is less than 1, the photocatalytic performance is not fully exhibited, which is not preferred, and if it exceeds 100,000, the antibacterial performance is not fully exhibited, which is not preferred.

[0129] The 50% cumulative distribution diameter (D) on a volume basis measured by dynamic light scattering using a laser beam is related to the dispersed particle diameter of a mixture of titanium oxide particles and metal particles in a titanium oxide particle / metal particle dispersion. 50 ) (sometimes referred to as "average particle size") is as described above. The device for measuring the average particle size is also as described above.

[0130] The total concentration of titanium oxide particles, metal particles, and other nonvolatile components in the titanium oxide particle-metal particle dispersion thus prepared is preferably 0.01 to 20 mass %, and particularly preferably 0.5 to 10 mass %, from the viewpoint of ease of fabricating a photocatalytic thin film of the required thickness, as described above. Regarding concentration adjustment, if the concentration is higher than the desired concentration, it can be reduced by diluting it with an aqueous solvent, and if it is lower than the desired concentration, it can be increased by volatilizing or filtering off the aqueous solvent.

[0131] The concentration of the titanium oxide particle / metal particle dispersion liquid can be measured by sampling a portion of the titanium oxide particle / metal particle dispersion liquid, heating it at 105°C for 3 hours to volatilize the solvent, and then calculating the concentration from the mass of the nonvolatile components (titanium oxide particles, metal particles, and nonvolatile impurities) and the mass of the sampled titanium oxide particle / metal particle dispersion liquid according to the following formula. Titanium oxide particle / metal particle dispersion concentration (%) = [Non-volatile matter mass (g) / Titanium oxide particle / metal particle dispersion mass (g)] x 100

[0132] When adding a binder that enhances the film-forming properties described above, it is preferable to add the binder solution (aqueous binder solution) described above to the titanium oxide particle / metal particle dispersion whose concentration has been adjusted as described above so that the desired concentration is obtained after mixing. The silicon component contained in the titanium oxide particle dispersion inhibits the aggregation and precipitation of the titanium oxide particles and iron components, preventing a decrease in photocatalytic activity, and is added at the same time as the titanium oxide particles and iron components are mixed. On the other hand, the binder enhances the film-forming properties of the titanium oxide particle / metal particle dispersion, and is added after the titanium oxide particle / metal particle dispersion is prepared and before coating; therefore, the two are different.

[0133] Next, an embodiment in which the titanium oxide particle / metal particle composition of the present invention is a thin film of titanium oxide particles / metal particles will be described. The titanium oxide particle / metal particle dispersion liquid, which is one embodiment of the present invention, can be used to form a photocatalytic thin film on the surface of various components. The components are not particularly limited, and examples of the components include organic and inorganic materials. These components can have various shapes depending on their respective purposes and applications.

[0134] Examples of organic materials include synthetic resin materials such as polyvinyl 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, phenolic resin, and acrylonitrile-butadiene-styrene (ABS) resin; natural materials such as natural rubber; and semi-synthetic materials made from the above synthetic resin materials and natural materials. These may be commercialized into desired shapes and configurations such as films, sheets, textile materials, textile products, other molded products, and laminates.

[0135] 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 commercialized into various forms such as 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 metallic inorganic material, coated with the organic material, or plated on the surface of the organic material or non-metallic inorganic material.

[0136] The titanium oxide particle / metal particle dispersion of the present invention is particularly useful for producing a photocatalytic thin film by applying it to various materials 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 materials.

[0137] The photocatalytic thin film can be formed on the surface of various components by applying a titanium oxide particle / metal particle dispersion to the surface of the component using a known application method such as spray coating or dip coating, and then drying the coating using a known drying method such as far-infrared drying, IH drying, or hot air drying. The thickness of the photocatalytic thin film can be selected from a variety of thicknesses, but a range of 10 nm to 10 μm is usually preferred. This results in the formation of a thin film of titanium oxide particles and metal particles. In this case, if the dispersion contains the binder in the amount described above, a thin film containing titanium oxide particles, metal particles, and the binder is formed.

[0138] The photocatalytic thin film formed in this way is transparent and not only exhibits good photocatalytic action in ultraviolet light (wavelength 10 to 400 nm) as in the past, but also exhibits superior photocatalytic action in visible light (wavelength 400 to 800 nm), for which previous photocatalysts were unable to achieve sufficient photocatalytic action.Various components on which this photocatalytic thin film is formed can exhibit effects such as cleaning, deodorizing, and antibacterial properties on the surface of the component due to the antibacterial action of the metal particles and the photocatalytic action of titanium oxide. [Example]

[0139] 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 carried out as follows.

[0140] (1) The 50% and 90% cumulative distribution diameters (D 50 and D 90 ) D of titanium oxide particles and metal particles in dispersion 50 and D 90 was calculated as the 50% and 90% cumulative distribution diameters on a volume basis measured by dynamic light scattering using a laser beam using a particle size distribution analyzer (ELSZ-2000ZS (Otsuka Electronics Co., Ltd.)).

[0141] (2) Acetaldehyde gas decomposition performance test of photocatalytic thin film The activity of the photocatalytic thin film prepared by coating and drying the dispersion was evaluated by the decomposition reaction of acetaldehyde gas using a batch gas decomposition performance evaluation method. Each titanium oxide particle dispersion prepared in the Examples or Comparative Examples was spread onto one side of an A4 size (210 mm × 297 mm) PET film using a #7 wire bar coater so that the dry mass of titanium oxide particles and metal particles was approximately 20 mg to prepare a sample for evaluation. The sample was then dried in an oven set at 80°C for 1 hour to obtain a sample for evaluating acetaldehyde gas decomposition performance. Using this evaluation sample, the photocatalytic activity of titanium oxide particles and metal particles was evaluated by the decomposition reaction of acetaldehyde gas using a batch gas decomposition performance evaluation method. Specifically, a sample for evaluation was placed in a 5-L stainless steel cell with a quartz glass window. The cell was then filled with acetaldehyde gas at an initial concentration adjusted to 50% humidity, and light was irradiated from a light source installed above the cell. When acetaldehyde gas decomposed by the photocatalytic action of titanium oxide, the acetaldehyde gas concentration in the cell decreased. Therefore, the strength of photocatalytic activity could be confirmed by measuring this concentration change. The acetaldehyde gas concentration was evaluated using a photoacoustic multi-gas monitor (trade name "INNOVA1412", manufactured by LumaSense) to measure the time from the start of light irradiation until the acetaldehyde gas concentration reached 1 ppm or less. A shorter time indicates higher photocatalytic activity, while a longer time indicates lower photocatalytic activity.

[0142] In the evaluation of photocatalytic activity under visible light irradiation, an LED (product number "TH-211x200SW", CCS Inc., spectral distribution: 400-800 nm) was used as the light source, and visible light was irradiated at an illuminance of 10,000 lx. At this time, the initial concentration of acetaldehyde in the cell was set to 5 ppm.

[0143] The test results were evaluated according to the following criteria. Very good (marked as ◎) Reduced within 5 hours Good (marked as ○) Reduced within 10 hours · Slightly poor (marked as △) · Reduced within 20 hours · Poor (marked as ×) · · · Cannot be reduced within 20 hours

[0144] (3) Antibacterial test of photocatalytic thin film (in the dark, under visible light irradiation) The antibacterial performance of the photocatalytic thin film was tested under visible light irradiation using a sample in which the photocatalytic thin film was applied to a thickness of 100 nm on a 50 mm square glass substrate, in accordance with the test method for hybrid photocatalytic antibacterial processed flat plate products in the Japanese Industrial Standard JIS R 1752:2020 "Fine ceramics - Antibacterial test method and antibacterial effect of visible light responsive photocatalytic antibacterial processed materials." A Type B sharp cut filter was used, and the illuminance was set to 3,000 lx.

[0145] The test results were evaluated according to the following criteria. Very good (marked as ◎) - All antibacterial activity values are 4.0 or higher Good (marked with ○) - All antibacterial activity values are 2.0 or higher · Defective (marked as ×) · Antibacterial activity value less than 2.0

[0146] (4) Identification of the crystalline phase of titanium oxide particles The crystalline phase of the titanium oxide particles was identified by measuring the titanium oxide particle powder recovered from the resulting dispersion of titanium oxide particles by powder X-ray diffraction (trade name: "Tabletop X-ray Diffractometer D2 PHASER", Bruker AXS Co., Ltd.).

[0147] (5) Preparation of titanium oxide particle dispersion [Preparation Example 1-1] <Preparation of titanium oxide particle dispersion> <Preparation of titanium oxide particle dispersion containing tin and molybdenum as a solid solution> Tin(IV) chloride was added and dissolved in a 36% by mass aqueous solution of titanium(IV) chloride so that the TiO2 / Sn (molar ratio) in the resulting titanium oxide particle dispersion was 20. This solution was then diluted 10 times with pure water, and 10% by mass aqueous ammonia was gradually added to neutralize and hydrolyze the solution, yielding a tin-containing titanium hydroxide precipitate. The pH was then 8. The resulting precipitate was deionized by repeatedly adding pure water and decanting. Sodium molybdate(VI) was added to the deionized tin-containing titanium hydroxide precipitate so that the TiO2 / Mo (molar ratio) in the resulting titanium oxide particle dispersion was 400. 35% by mass aqueous hydrogen peroxide was then added so that the HO2 / (Ti + Sn + Mo) (molar ratio) was 10. The mixture was then stirred at 60°C for 2 hours to allow the reaction to proceed sufficiently, yielding a transparent, orange-colored tin- and molybdenum-containing peroxotitanic acid solution (1a).

[0148] A 500 mL autoclave was charged with 400 mL of the tin- and molybdenum-containing peroxotitanic acid solution (1a), which was then hydrothermally treated at 150°C for 90 minutes. Pure water was then added to adjust the concentration, yielding a dispersion (1A) of titanium oxide particles with tin and molybdenum dissolved therein (titanium oxide concentration: 1.2% by mass). Powder X-ray diffraction analysis of the titanium oxide particles revealed that the only peak observed was that of rutile-type titanium oxide, indicating that tin and molybdenum were dissolved in the titanium oxide.

[0149] [Preparation Example 1-2] <Preparation of a dispersion of titanium oxide particles containing tin and tungsten as a solid solution> Tin(IV) chloride was added and dissolved in a 36% by mass aqueous solution of titanium(IV) chloride so that the TiO2 / Sn (molar ratio) in the resulting titanium oxide particle dispersion was 10. This solution was then diluted 10 times with pure water, and 10% by mass aqueous ammonia was gradually added to neutralize and hydrolyze the solution, yielding a tin-containing titanium hydroxide precipitate. The pH was then 8. The resulting precipitate was deionized by repeatedly adding pure water and decanting. Sodium tungstate(VI) was added to the deionized tin-containing titanium hydroxide precipitate so that the TiO2 / W (molar ratio) in the resulting titanium oxide particle dispersion was 100. Further, 35% by mass aqueous hydrogen peroxide was added so that the HO2 / (Ti + Sn + W) (molar ratio) was 10. The mixture was then stirred at 60°C for 2 hours to allow the reaction to proceed sufficiently, yielding a transparent orange tin- and tungsten-containing peroxotitanic acid solution (1b).

[0150] A 500 mL autoclave was charged with 400 mL of the tin- and tungsten-containing peroxotitanic acid solution (1b), which was then hydrothermally treated at 160°C for 60 minutes. Pure water was then added to adjust the concentration, yielding a dispersion (1B) of titanium oxide particles containing tin and tungsten in a solid solution (titanium oxide concentration: 1.2% by mass). Powder X-ray diffraction analysis of the titanium oxide particles revealed that the only peak observed was that of rutile-type titanium oxide, indicating that tin and tungsten were dissolved in the titanium oxide.

[0151] [Preparation Example 1-3] <Preparation of titanium oxide particle dispersion containing tin and vanadium as a solid solution> Tin(IV) chloride was added and dissolved in a 36% by weight titanium(IV) chloride aqueous solution so that the TiO2 / Sn (molar ratio) in the resulting titanium oxide particle dispersion was 33. This solution was then diluted 10 times with pure water, and 10% by weight ammonia water was gradually added to neutralize and hydrolyze the solution, yielding a tin-containing titanium hydroxide precipitate. The pH was then 8. The resulting precipitate was deionized by repeatedly adding pure water and decanting. Sodium vanadate (V) was added to the deionized tin-containing titanium hydroxide precipitate so that the TiO2 / V (molar ratio) in the resulting titanium oxide particle dispersion was 2,000. 35% by weight hydrogen peroxide was then added so that the HO2 / (Ti + Sn + V) (molar ratio) was 10. The mixture was then stirred at 50°C for 3 hours to allow the reaction to proceed sufficiently, yielding a transparent orange tin- and vanadium-containing peroxotitanate solution (1c).

[0152] A 500 mL autoclave was charged with 400 mL of the tin- and vanadium-containing peroxotitanate solution (1c), which was subjected to hydrothermal treatment at 140°C for 120 minutes. Pure water was then added to adjust the concentration, yielding a dispersion (1C) of titanium oxide particles containing dissolved tin and vanadium (titanium oxide concentration: 1.2% by mass). Powder X-ray diffraction analysis of the titanium oxide particles revealed peaks corresponding to anatase and rutile titanium oxides, indicating that tin and vanadium were dissolved in the titanium oxide.

[0153] [Preparation Example 1-4] <Preparation of titanium oxide particle dispersion containing tin and molybdenum as a solid solution> Tin(IV) chloride was added and dissolved in a 36% by weight titanium(IV) chloride aqueous solution so that the TiO2 / Sn (molar ratio) in the resulting titanium oxide particle dispersion was 20. This solution was then diluted 10 times with pure water, and 10% by weight ammonia water was gradually added to neutralize and hydrolyze the solution, yielding a tin-containing titanium hydroxide precipitate. The pH was then 8. The resulting precipitate was deionized by repeatedly adding pure water and decanting. Sodium molybdate(VI) was added to the deionized tin-containing titanium hydroxide precipitate so that the TiO2 / Mo (molar ratio) in the resulting titanium oxide particle dispersion was 100. 35% by weight hydrogen peroxide was then added so that the HO2 / (Ti + Sn + Mo) (molar ratio) was 12. The mixture was then stirred at 60°C for 2 hours to allow the reaction to proceed sufficiently, yielding a transparent orange tin- and molybdenum-containing peroxotitanic acid solution (1d).

[0154] A 500 mL autoclave was charged with 400 mL of tin- and molybdenum-containing peroxotitanic acid solution (d), which was then hydrothermally treated at 120°C for 180 minutes. Pure water was then added to adjust the concentration, yielding a dispersion (1D) of titanium oxide particles with tin and molybdenum dissolved therein (titanium oxide concentration: 1.2% by mass). Powder X-ray diffraction analysis of the titanium oxide particles revealed that the only peak observed was that of rutile-type titanium oxide, indicating that tin and molybdenum were dissolved in the titanium oxide.

[0155] [Preparation Example 1-5] <Preparation of a dispersion of titanium oxide particles containing tin as a solid solution> A dispersion (1E) of titanium oxide particles containing dissolved tin (titanium oxide concentration: 1.2% by mass) was obtained in the same manner as in Preparation Example 1-1, except that sodium molybdate (VI) was not added. When the titanium oxide particles were subjected to powder X-ray diffraction measurement, the only peak observed was that of rutile-type titanium oxide, indicating that tin was dissolved in the titanium oxide.

[0156] [Preparation Example 1-6] <Preparation of Molybdenum-Soluted Titanium Oxide Particle Dispersion> A dispersion (1F) of titanium oxide particles having molybdenum dissolved therein (titanium oxide concentration: 1.2% by mass) was obtained in the same manner as in Preparation Example 1-1, except that tin (IV) chloride was not added. When the titanium oxide particles were subjected to powder X-ray diffraction measurement, the only peak observed was that of anatase titanium oxide, indicating that molybdenum was dissolved in the titanium oxide.

[0157] [Preparation Example 1-7] <Preparation of a dispersion of titanium oxide particles containing tungsten as a solid solution> A dispersion liquid (1G) of titanium oxide particles having tungsten dissolved therein (titanium oxide concentration: 1.2% by mass) was obtained in the same manner as in Preparation Example 1-2, except that tin(IV) chloride was not added. When the titanium oxide particles were subjected to powder X-ray diffraction measurement, the only peak observed was that of anatase titanium oxide, indicating that tungsten was dissolved in the titanium oxide.

[0158] [Preparation Example 1-8] <Preparation of titanium oxide particle dispersion containing vanadium as a solid solution> A dispersion liquid (1H) of titanium oxide particles having vanadium dissolved therein (titanium oxide concentration: 1.2% by mass) was obtained in the same manner as in Preparation Example 1-3, except that tin (IV) chloride was not added. When the titanium oxide particles were subjected to powder X-ray diffraction measurement, the only peak observed was that of anatase-type titanium oxide, indicating that vanadium was dissolved in the titanium oxide.

[0159] [Preparation Example 1-9] <Preparation of titanium oxide particle dispersion> A 36% by mass aqueous solution of titanium(IV) chloride was diluted 10 times with pure water, and then 10% by mass aqueous ammonia was gradually added to neutralize and hydrolyze the solution, yielding a titanium hydroxide precipitate. The pH at this point was 8.5. The resulting precipitate was deionized by repeatedly adding pure water and decanting. After this deionization, 35% by mass aqueous hydrogen peroxide was added to the titanium hydroxide precipitate so that the HO / Ti (molar ratio) was 8.0. The mixture was then stirred at 60°C for 2 hours to allow the reaction to proceed sufficiently, yielding a transparent orange peroxotitanic acid solution (1i).

[0160] A 500 mL autoclave was charged with 400 mL of peroxotitanic acid solution (1i), which was subjected to hydrothermal treatment at 130°C for 90 minutes, and then purified water was added to adjust the concentration, yielding a dispersion (1I) of titanium oxide particles (titanium oxide concentration 1.2% by mass). When the titanium oxide particles were subjected to powder X-ray diffraction measurement, the only peak observed was that of anatase-type titanium oxide.

[0161] Table 1 shows the molar ratio of titanium oxide particles prepared in each preparation example, the hydrothermal treatment conditions, and the dispersed particle diameter (D 50 , D 90 The dispersed particle size was measured by dynamic light scattering using a laser beam (ELSZ-2000ZS (Otsuka Electronics Co., Ltd.)).

[0162] [Table 1]

[0163] (6) Preparation of surface-modified titanium oxide particle dispersion [Preparation Example 2-1] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A strong acid cation exchange resin (Amberlite HPR1024H, manufactured by Organo Corporation) was added to an aqueous sodium silicate solution obtained by dissolving 0.34 g of JIS No. 3 sodium silicate (29.1% by mass in terms of SiO2) in 100 g of pure water, and the mixture was stirred. The ion exchange resin was then filtered off to obtain an aqueous activated silicic acid solution. 0.31 g of a 41% aqueous solution of ferric sulfate (III) was added to the aqueous activated silicic acid solution to obtain an aqueous solution of iron sulfate and active silicic acid with a pH of 2.4.

[0164] The titanium oxide particle dispersion (1A) was mixed with the aqueous solution of iron sulfate and activated silicic acid prepared as described above using a stirrer at 25°C for 1 hour so that the TiO2 / Fe2O3 ratio was 200 and the TiO2 / SiO2 ratio was 100.The solid content was then adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (2A) whose surfaces were modified with iron and silicon components.

[0165] [Preparation Example 2-2] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2B) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1B) was used.

[0166] [Preparation Example 2-3] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2C) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1C) was used.

[0167] [Preparation Example 2-4] <Preparation of a dispersion of titanium oxide particles whose surfaces are modified with iron, titanium, and silicon components> A strong acid cation exchange resin (Amberlite HPR1024H, manufactured by Organo Corporation) was added to an aqueous sodium silicate solution prepared by dissolving 1.71 g of JIS No. 3 sodium silicate (29.1% SiO2 equivalent) in 100 g of pure water, and the mixture was stirred. The ion exchange resin was then filtered off to obtain an aqueous activated silicic acid solution. 0.31 g of a 41% aqueous solution of ferric sulfate (III) and 0.33 g of a 36% aqueous solution of titanium (IV) chloride were added to the aqueous activated silicic acid solution to obtain an aqueous solution of ferric sulfate, titanium chloride, and activated silicic acid with a pH of 1.6.

[0168] The titanium oxide particle dispersion (1A) was mixed with the aqueous solution of iron sulfate, titanium chloride, and activated silicic acid prepared as described above using a stirrer for 1 hour at 25°C so that the TiO2 / Fe2O3 ratio was 200, the TiO2 / TiO2 (modifying component) ratio was 200, and the TiO2 / SiO2 ratio was 20.The solid concentration was then adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (2D) whose surfaces were modified with iron components, titanium components, and silicon components.

[0169] [Preparation Example 2-5] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A strong acid cation exchange resin (Amberlite HPR1024H, manufactured by Organo Corporation) was added to an aqueous sodium silicate solution obtained by dissolving 0.17 g of JIS No. 3 sodium silicate (29.1% by mass in terms of SiO2) in 100 g of pure water, and the mixture was stirred. The ion exchange resin was then filtered off to obtain an aqueous activated silicic acid solution. 0.15 g of a 41% aqueous solution of ferric sulfate (III) was added to the aqueous activated silicic acid solution to obtain an aqueous solution of iron sulfate and active silicic acid with a pH of 2.6.

[0170] The titanium oxide particle dispersion (1D) was mixed with the aqueous solution of iron sulfate and activated silicic acid prepared as described above using a stirrer at 25°C for 1 hour so that the TiO2 / Fe2O3 ratio was 400 and the TiO2 / SiO2 ratio was 200.The solid concentration was then adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (2E) whose surfaces were modified with iron and silicon components.

[0171] [Preparation Example 2-6] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2F) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1E) was used.

[0172] [Preparation Example 2-7] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2G) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1F) was used.

[0173] [Preparation Example 2-8] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2H) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1G) was used.

[0174] [Preparation Example 2-9] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2I) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1H) was used.

[0175] [Preparation Example 2-10] <Preparation of titanium oxide particle dispersion whose surface is modified with iron and silicon components> A titanium oxide particle dispersion (2J) surface-modified with iron and silicon components was obtained in the same manner as in Preparation Example 2-1, except that the titanium oxide particle dispersion (1I) was used.

[0176] [Preparation Example 2-11] <Preparation of titanium oxide particle dispersion with silicon component on the surface> An active silicic acid aqueous solution having a pH of 4.8 was obtained in the same manner as in Preparation Example 2-1, except that ferric sulfate (III) was not added.

[0177] The titanium oxide particle dispersion (1A) was mixed with the activated silicic acid aqueous solution prepared as described above using a stirrer at 25°C for 1 hour so that the TiO2 / SiO2 ratio was 100, and then the solid concentration was adjusted to 1 mass% with pure water to obtain a titanium oxide particle dispersion (2K) whose surface was modified with silicon components.

[0178] [Preparation Example 2-12] <Preparation of titanium oxide particle dispersion with iron-modified surface> 0.31 g of a 41% aqueous solution of ferric sulfate (III) was added to 100 g of pure water and stirred to obtain an aqueous solution of ferric sulfate with a pH of 2.4.

[0179] The dispersion of titanium oxide particles (1A) was mixed with the aqueous solution of iron sulfate prepared as described above using a stirrer for 1 hour at 25°C so that the TiO2 / Fe2O3 ratio was 200, and then the solid content was adjusted to 1 mass% with pure water to obtain a dispersion of titanium oxide particles (2 L) whose surfaces were modified with iron components. During the addition of the aqueous solution of iron sulfate, the dispersion became cloudy and some precipitation was observed.

[0180] [Table 2]

[0181] (7) Preparation of metal particle dispersion [Preparation Example 3-1] <Preparation of silver particle dispersion> Silver nitrate was dissolved in ethylene glycol as a solvent so that the concentration of Ag was 2.50 mmol / L, to obtain a solution containing the raw material metal compound. A solution containing a reducing agent was obtained by mixing 55% by mass of ethylene glycol and 8% by mass of pure water as a solvent, 2% by mass of potassium hydroxide as a basic substance, 20% by mass of hydrazine monohydrate and 5% by mass of dimethylaminoethanol as a reducing agent, and 10% by mass of polyvinylpyrrolidone as a reducing agent / protecting agent. 2 L of a solution containing raw metal compounds heated to 90°C in a reactor was mixed with 0.2 L of a solution containing a reducing agent / protecting agent at 25°C. The resulting solution was concentrated using an ultrafiltration membrane with a molecular weight cutoff of 10,000 (Microza, Asahi Kasei Corporation) and washed with pure water to obtain silver particle dispersion (3A). The obtained metal particle dispersion is summarized in Table 3.

[0182] [Preparation Example 3-2] <Preparation of Silver-Copper Particle Dispersion> Ethylene glycol was used as a solvent, and silver nitrate and copper nitrate dihydrate were dissolved therein to give a concentration of 2.50 mmol / L as Ag and 2.50 mmol / L as Cu, respectively, to obtain a solution containing raw metal compounds. A solution containing a reducing agent was obtained by mixing 55% by mass of ethylene glycol and 8% by mass of pure water as a solvent, 2% by mass of potassium hydroxide as a basic substance, 20% by mass of hydrazine monohydrate and 5% by mass of dimethylaminoethanol as a reducing agent, and 10% by mass of polyvinylpyrrolidone as a reducing agent / protecting agent. 2 L of a solution containing raw metal compounds heated to 150°C in a reactor was mixed with 0.2 L of a solution containing a reducing agent at 25°C. The resulting solution was concentrated using an ultrafiltration membrane with a molecular weight cutoff of 10,000 (Microza, Asahi Kasei Corporation) and washed with pure water to obtain a silver-copper particle dispersion (3B).

[0183] [Preparation Example 3-3] <Preparation of Silver-Zinc Particle Dispersion> A silver-zinc particle dispersion (3C) was obtained in the same manner as in Preparation Example 3-2, except that a solution containing raw metal compounds was used in which ethylene glycol was used as a solvent, and silver nitrate was dissolved to a concentration of 3.75 mmol / L as Ag and zinc nitrate hexahydrate was dissolved to a concentration of 1.25 mmol / L as Zn.

[0184] [Preparation Example 3-4] <Preparation of silver particle dispersion> A silver particle dispersion (3D) was obtained in the same manner as in Preparation Example 3-1, except that the amount of pure water used for washing with the ultrafiltration membrane was reduced.

[0185] [Preparation Example 3-5] <Preparation of silver particle dispersion> A silver particle dispersion (3E) was obtained in the same manner as in Preparation Example 3-1, except that polyvinylpyrrolidone, which was added as a reducing agent / protecting agent, was not added.

[0186] [Table 3]

[0187] (8) Preparation of titanium oxide particle / metal particle dispersion [Example 1] The surface-protected metal particle dispersion (3A) was mixed with the surface-modified titanium oxide particle dispersion (2A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, thereby obtaining the titanium oxide particle / metal particle dispersion (E-1) of the present invention. The obtained titanium oxide particle / metal particle dispersions are summarized in Table 4 below.

[0188] [Example 2] The surface-modified titanium oxide particle dispersion (2B) was mixed with the surface-protected metal particle dispersion (3B) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 400, thereby obtaining a titanium oxide particle / metal particle dispersion (E-2) of the present invention.

[0189] [Example 3] The surface-modified titanium oxide particle dispersion (2C) was mixed with the surface-protected metal particle dispersion (3C) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 200, thereby obtaining a titanium oxide particle / metal particle dispersion (E-3) of the present invention.

[0190] [Example 4] The surface-protected metal particle dispersion (3A) was mixed with the surface-modified titanium oxide particle dispersion (2D) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, thereby obtaining a titanium oxide particle / metal particle dispersion (E-4) of the present invention.

[0191] [Example 5] The surface-modified titanium oxide particle dispersion (2E) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, thereby obtaining a titanium oxide particle / metal particle dispersion (E-5) of the present invention.

[0192] [Example 6] The surface-modified titanium oxide particle dispersion (2A) was mixed with the surface-protected metal particle dispersion (3D) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, thereby obtaining a titanium oxide particle / metal particle dispersion (E-6) of the present invention.

[0193] [Example 7] The surface-modified titanium oxide particle dispersion (2A) was mixed with the metal particle dispersion (3E) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / metal particles) was 1,000, thereby obtaining a titanium oxide particle / metal particle dispersion (E-7) of the present invention.

[0194] [Example 8] A silicon compound (silica-based) binder (colloidal silica, product name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added to the titanium oxide particle / metal particle dispersion (E-1) so that the titanium oxide particle / metal particle / binder (mass ratio) was 1.5, and the mixture was mixed with a stirrer at 25°C for 10 minutes to obtain a binder-containing titanium oxide particle dispersion (E-8). The titanium oxide particle / metal particle dispersions to which binder had been added are summarized in Table 5.

[0195] [Comparative Example 1] A titanium oxide particle dispersion (C-1) for comparative evaluation was obtained from the surface-modified titanium oxide particle dispersion (2A).

[0196] Comparative Example 2 A metal particle dispersion (C-2) for comparative evaluation was obtained from the surface-protected silver particle dispersion (3A).

[0197] Comparative Example 3 The titanium oxide particle dispersion (1A) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-3) for comparative evaluation.

[0198] Comparative Example 4 The surface-modified titanium oxide particle dispersion (2F) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-4) for comparative evaluation.

[0199] Comparative Example 5 The surface-modified titanium oxide particle dispersion (2G) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-5) for comparative evaluation.

[0200] Comparative Example 6 The surface-modified titanium oxide particle dispersion (2H) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-6) for comparative evaluation.

[0201] Comparative Example 7 The surface-modified titanium oxide particle dispersion (2I) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-7) for comparative evaluation.

[0202] [Comparative Example 8] The surface-modified titanium oxide particle dispersion (2J) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-8) for comparative evaluation.

[0203] Comparative Example 9 The surface-modified titanium oxide particle dispersion (2K) was mixed with the surface-protected metal particle dispersion (3A) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-9) for comparative evaluation.

[0204] [Comparative Example 10] The surface-protected metal particle dispersion (3A) was mixed with the surface-modified titanium oxide particle dispersion (2 L) so that the mass ratio of particles contained in each dispersion (surface-modified titanium oxide particles / surface-protected metal particles) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-10) for comparative evaluation. The resulting liquid was cloudy, with some of the particles settling.

[0205] [Comparative Example 11] A 1% by mass aqueous solution of silver nitrate was mixed with the surface-modified titanium oxide particle dispersion (2A) so that the mass ratio to the surface-modified titanium oxide particles (surface-modified titanium oxide particles / silver) was 100, to obtain a titanium oxide particle / metal particle dispersion (C-11) for comparative evaluation. The resulting liquid was cloudy, with some of the particles settling.

[0206] [Comparative Example 12] A binder-containing titanium oxide particle / metal particle dispersion (C-12) was obtained in the same manner as in Example 8, except that the titanium oxide particle / metal particle dispersion (C-3) was used.

[0207] [Table 4]

[0208] [Table 5]

[0209] The antibacterial performance test and acetaldehyde gas decomposition performance test were carried out for each of the examples and comparative examples as described above. The results of the tests and whether or not there was any precipitate (no (good): indicated by ○, present (bad): indicated by ×) are summarized in Table 6.

[0210] [Table 6]

[0211] From Example 1 and Comparative Example 1, it was found that titanium oxide particles alone could not provide antibacterial properties in a dark place.

[0212] From Example 1 and Comparative Example 2, it was found that photocatalytic activity under visible light irradiation cannot be obtained with metal particles alone.

[0213] From Example 1 and Comparative Examples 3 and 9 and Example 8 and Comparative Example 12, it was found that unless the surface of titanium oxide is modified with iron (Fe) and silicon (Si), the photocatalytic activity under visible light irradiation is low.

[0214] From Example 1 and Comparative Example 10, it was found that when the surface of titanium oxide was modified with iron (Fe) alone, the components aggregated and precipitated.

[0215] From Example 1 and Comparative Example 11, it was found that when the surface of surface-modified titanium oxide was further modified with a silver component, the photocatalytic activity under visible light irradiation decreased and the components aggregated and precipitated.

[0216] From Examples 1 to 7 and Comparative Examples 4 to 8, it was found that photocatalytic activity under visible light irradiation cannot be obtained unless the tin component and the transition metal component are solid-dissolved in the titanium oxide.

Claims

1. i) titanium oxide particles having a surface modified with a tin component and a transition metal component that enhances visible light activity, but not with an iron component or a silicon component; ii) metal particles containing antibacterial metals; A titanium oxide particle / metal particle composition containing two types of particles: i) the mass ratio (TiO 2 / Fe 2 O 3 ) of the iron component (as oxide) modifying the surface of the titanium oxide particles to the titanium oxide is 20 to 10,000; i) the silicon component modifying the surface of the titanium oxide particles is derived from silicate or active silicic acid, and the mass ratio of the silicon component (as oxide) to titanium oxide (TiO 2 / SiO 2 ) is 5 to 1,000; the mass ratio (TiO 2 / M) of the titanium oxide particles in i) to the antibacterial metal component (M) contained in the metal particles in ii) is 10 to 10,000; A titanium oxide particle / metal particle composition, in which the volume-based 50% cumulative distribution diameter (D 50 ) of titanium oxide particles in a dispersion liquid, as measured by dynamic light scattering using laser light, is 3 to 50 nm.

2. 2. The titanium oxide particle / metal particle composition according to claim 1, wherein a protective agent is adsorbed onto the surface of metal particles containing the antibacterial metal of ii).

3. 2. The titanium oxide particle / metal particle composition according to claim 1, wherein the antibacterial metal contained in the antibacterial metal-containing metal particles is at least one metal selected from the group consisting of silver, copper, and zinc.

4. 4. The titanium oxide particle / metal particle composition according to claim 3, wherein the antibacterial metal contained in the antibacterial metal-containing metal particles of ii) contains at least silver.

5. i) the content of the tin component dissolved in the titanium oxide particles is in the molar ratio to titanium oxide (TiO 2 2. The titanium oxide particle / metal particle composition according to claim 1, wherein the SiO 2 content is 1 to 1,000.

6. i) The mass ratio of the iron component (as oxide) modifying the surface of the titanium oxide particles to titanium oxide (TiO 2 / Fe 2 O 3 2. The titanium oxide particle / metal particle composition according to claim 1, wherein the molecular weight of the titanium oxide particle / metal particle composition is 50 to 1,000.

7. 2. The titanium oxide particle / metal particle composition according to claim 1, wherein the transition metal component that enhances visible light activity and is solid-solved in the titanium oxide particles (i) is at least one selected from molybdenum, tungsten, and vanadium.

8. i) The amounts of the molybdenum, tungsten, and vanadium components dissolved in the titanium oxide particles are in the molar ratio to the titanium oxide (TiO 2 / Mo, TiO 2 / W or TiO 2 8. The titanium oxide particle / metal particle composition according to claim 7, wherein the molecular weight (Mw / V) is 1 to 10,000.

9. The mass ratio of the titanium oxide particles in i) to the antibacterial metal component (M) contained in the metal particles in ii) (TiO 2 2. The titanium oxide particle / metal particle composition according to claim 1, wherein the molecular weight of the titanium oxide particle / metal particle composition is 100 to 1,000.

10. The titanium oxide particle / metal particle composition according to claim 1 , further comprising a binder.

11. 11. The titanium oxide particle / metal particle composition according to claim 10, wherein the binder is a silicon compound-based binder.

12. The composition according to any one of claims 1 to 11, wherein the titanium oxide particle / metal particle composition is a dispersion of titanium oxide particles / metal particles.

13. The composition according to any one of claims 1 to 11, wherein the titanium oxide particle / metal particle composition is a thin film of titanium oxide particles / metal particles.

14. A member having the composition according to claim 13 on its surface.

15. A method for producing the composition according to claim 12, comprising the following steps (1) to (8): (1) A step of producing a peroxotitanic acid solution containing a tin component and a transition metal component from raw material titanium compounds, tin compounds, transition metal compounds, basic substances, hydrogen peroxide, and an aqueous dispersion medium. (2) A step of heating the peroxotitanic acid solution containing the tin component and the transition metal component produced in the above step (1) at 80 to 250°C under pressure control to obtain a titanium oxide particle dispersion liquid in which the tin component and the transition metal component are solid-dissolved. (3) A step of producing a solution or dispersion of an iron component and a silicon component from an iron compound, a silicate or an active silicic acid, and an aqueous dispersion medium. (4) A step of mixing the titanium oxide particle dispersion liquid produced in the above step (2) with the solution or dispersion liquid of iron and silicon components produced in the step (3) to obtain a titanium oxide particle dispersion liquid whose surfaces are modified with iron components and silicon components derived from silicate or active silicic acid. (5) A step of producing a solution containing the raw antibacterial metal compound and a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (6) A step of producing a metal particle dispersion by mixing the solution containing the raw antibacterial metal compound produced in the step (5) with a solution containing a reducing agent for reducing the metal compound and a protecting agent for coating and protecting the metal particles. (7) A step of washing the metal particle dispersion liquid produced in the above step (6) with an aqueous dispersion medium by membrane filtration. (8) A step of mixing the titanium oxide particle dispersion liquid and the metal particle dispersion liquid obtained in the steps (4) and (7).

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