Visible light-responsive titanium oxide particle dispersion liquid and method for manufacturing the same

The present invention relates to a visible light responsive titanium oxide-based fine particle dispersion and a method for producing the same. More specifically, the present invention provides a highly transparent photocatalytic thin film having excellent dispersion stability of titanium oxide fine particles and visible light responsiveness. The present invention relates to a visible light responsive titanium oxide-based dispersion that can be easily produced and a method for producing the same.

Titanium oxide is a precursor of composite oxides such as pigments, ultraviolet shielding agents, catalysts, photocatalysts, catalyst carriers, adsorbents, ion exchangers, fillers, reinforcing agents, raw materials for ceramics, and perovskite-type composite oxides. It is used as an undercoat for the body and magnetic tape.

Among them, the photocatalytic titanium oxide fine particles are based on the fact that the photocatalytic coating film formed by coating the dispersion liquid on the surface of various substrates decomposes organic substances by the photocatalytic action of titanium oxide to make the film surface hydrophilic. It is often used for cleaning the surface of materials, deodorizing, antibacterial, etc. In order to enhance the photocatalytic activity, it is necessary to widen the contact area between the photocatalytic particles and the substance to be decomposed, and for that purpose, the primary particle size of the particles is required to be 50 nm or less. Furthermore, the transparency of the film is also required so as not to lose the design of the base material.

As a method for producing a titanium oxide fine particle dispersion, 1) a method of dispersing titanium oxide fine powder in a dispersion medium by a wet disperser using a dispersion aid such as an organic polymer dispersant (Patent Documents 1 to 3). , And 2) a liquid phase method prepared by hydrothermal treatment of a titanium-containing compound solution (Patent Document 4). The problem with these manufacturing methods is that ultrafine particles with an average particle size of 50 nm or less tend to agglomerate, so it takes a lot of labor to disperse to the primary particles, and in some cases it is impossible to disperse to the primary particles. Is.

In addition, although titanium oxide exhibits good photocatalytic action under irradiation with light in the ultraviolet region having a relatively short wavelength such as sunlight, it is an indoor space illuminated by a light source such as a fluorescent lamp in which visible light occupies most of the light. In some cases, it may be difficult to exhibit sufficient photocatalytic action. In recent years, a tungsten oxide photocatalyst (Patent Document 4) has been attracting attention as a visible light responsive photocatalyst, but since tungsten is a rare element, it is desired to improve the visible light activity of the photocatalyst using titanium, which is a general-purpose element. There is.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 01-003020</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 06-279725</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 07-247119</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2009-148700</text></patcit></p>

<p> The present invention has been made in view of the above circumstances, and is a visible light responsive titanium oxide that is excellent in dispersion stability of titanium oxide fine particles and can easily produce a highly transparent photocatalyst thin film having visible light responsiveness. An object of the present invention is to provide a system dispersion liquid and a method for producing the same.</p>

<p> As a result of diligent studies to achieve the above object, the present inventors produced peroxotitanic acid containing a tin compound using a raw material titanium compound, a tin compound and hydrogen peroxide, and then subjected the peroxotitanic acid to a high pressure. After hydrothermal reaction to obtain a titanium oxide fine particle dispersion, a copper compound is added and reacted to obtain a titanium oxide fine particle dispersion containing a peroxotitanium component, a copper component, and a tin component, and this titanium oxide fine particle dispersion is obtained. Has found that a highly transparent photocatalyst thin film having excellent dispersion stability of titanium oxide fine particles and having visible light responsiveness can be easily produced from this titanium oxide dispersion, and has led to the present invention. ..</p><p> Therefore, the present invention provides the following visible light responsive titanium oxide-based dispersion and a method for producing the same. Claim 1: Titanium oxide fine particles are dispersed in the aqueous dispersion medium, and a peroxotitanium component, a copper component, and a tin component are contained, and the content of the peroxotitanium component is 0.1 to 20% by mass with respect to titanium oxide. A visible light responsive titanium oxide-based fine particle dispersion. Claim 2: The visible light-responsive titanium oxide-based fine particle dispersion according to claim 1, wherein the content of the copper component in terms of metallic copper is 0.01 to 5% by mass with respect to titanium oxide. Claim 3: The visible light-responsive titanium oxide-based fine particle dispersion according to claim 1 or 2, wherein the content of the tin component is 1 to 1000 in terms of molar ratio (Ti / Sn) with titanium oxide. Claim 4: The titanium oxide fine particles have a 50% cumulative distribution diameter (D) measured by the dynamic scattering method.₅₀) Is 50 nm or less, the visible light responsive titanium oxide-based fine particle dispersion according to any one of claims 1 to 3. Claim 5: (1) A process for producing peroxotitanic acid containing a tin compound from a raw material titanium compound, a tin compound and hydrogen peroxide. (2) A step of heating a peroxotitanic acid aqueous solution containing a tin compound at 80 to 250 ° C. under high pressure to obtain a titanium oxide fine particle dispersion containing a peroxotitanium component and a tin component, and (3) Step of adding a copper compound to the titanium oxide fine particle dispersion and reacting it. The method for producing a visible light responsive titanium oxide-based fine particle dispersion liquid according to any one of claims 1 to 4, wherein the liquid oxide-based fine particle dispersion liquid is characterized by having.</p>

<p> According to the present invention, a visible light responsive titanium oxide-based dispersion liquid and its production capable of easily producing a highly transparent photocatalytic thin film having excellent dispersion stability of titanium oxide fine particles and visible light responsiveness. A method can be provided.</p>

Hereinafter, the present invention will be described in more detail. &lt;Visible light responsive titanium oxide fine particle dispersion&gt; In the visible light-responsive titanium oxide-based fine particle dispersion of the present invention, titanium oxide fine particles are highly dispersed in an aqueous solvent, and a peroxotitanium component, a copper component, and a tin component are further contained.

Aqueous dispersion medium: An aqueous solvent is used as the aqueous dispersion medium. Examples of the aqueous solvent include water and a mixed solvent of water and a hydrophilic organic solvent mixed at an arbitrary ratio. As the water, for example, deionized water, distilled water, pure water and the like are preferable. As the hydrophilic organic solvent, alcohols such as methanol, ethanol and isopropanol are preferable. In this case, the mixing ratio of the hydrophilic organic solvent is preferably 0 to 50% by mass in the aqueous dispersion medium.

Titanium oxide fine particles: The titanium oxide fine particles dispersed in the aqueous dispersion medium have a 50% cumulative distribution diameter (D) based on the volume measured by the dynamic scattering method using laser light.₅₀) (Hereinafter referred to as "average particle size") is preferably 50 nm or less, more preferably 30 nm or less. Usually, the lower limit is not particularly limited, but it is preferably 5 nm or more.

The concentration of the titanium oxide fine particles is preferably 0.01 to 20% by mass, and particularly preferably 0.5 to 10% by mass in the dispersion liquid because it is easy to prepare a photocatalyst thin film having a required thickness.

Peroxotitanium component: Here, the "peroxotitanium component" means a titanium oxide-based compound containing a Ti-OO-Ti bond, and includes peroxotitanium acid and a peroxotitanium complex produced by the reaction of Ti (VI) with hydrogen peroxide. Wrap.

In the titanium oxide-based fine particle dispersion of the present invention, the peroxotitanium component has an action of satisfactorily dispersing titanium oxide. The concentration of the peroxotitanium component is 0.1 to 20% by mass, preferably 0.1 to 5% by mass, based on the titanium oxide fine particles. If the concentration is less than 0.1% by mass, the titanium oxide fine particles tend to aggregate. On the other hand, if it exceeds 20% by mass, the photocatalytic effect of the photocatalytic thin film obtained from the dispersion may be insufficient.

Copper component: The copper component has an effect of enhancing the decomposition activity of the obtained photocatalytic thin film. The presence state of the copper component is not limited, and may be any of, for example, metallic copper, oxides, hydroxides, nitrates, sulfates, halides, and complex compounds. It is preferable that at least a part of the copper component is supported on the surface of the titanium oxide fine particles, and the other part is preferably dissolved and / or dispersed in the dispersion liquid.

The content of the copper component in terms of metallic copper is preferably 0.01 to 5% by mass, particularly preferably 0.1 to 2% by mass, based on the titanium oxide fine particles. If the content of the copper component is too large, the photocatalytic activity may not be sufficiently exhibited.

Tin component: The tin component has an effect of enhancing the visible light responsiveness of the obtained photocatalytic thin film. The presence state of the tin component is not limited, and may be any of, for example, metallic tin, oxides, hydroxides, nitrates, sulfates, halides, and complex compounds. It is preferable that at least a part of the tin component is doped inside the titanium oxide fine particles or supported on the surface of the titanium oxide fine particles, and the other part is preferably dissolved and / or dispersed in the dispersion liquid.

The tin component is preferably contained in a molar ratio (Ti / Sn) with titanium oxide of 1 to 1000, particularly preferably 5 to 200, and more preferably 10 to 100. If the molar ratio exceeds 1000, the effect is insufficient. On the other hand, if it is less than 1, the titanium oxide content may decrease and the photocatalytic effect may not be sufficiently exhibited.

&lt;Manufacturing method of visible light responsive titanium oxide fine particle dispersion&gt; The above titanium oxide fine particle dispersion is (1) A process for producing peroxotitanic acid containing a tin compound from a raw material titanium compound, a tin compound and hydrogen peroxide. (2) A process of heating a peroxotitanic acid aqueous solution containing a tin compound at 80 to 250 ° C. under high pressure to convert it into a titanium oxide fine particle dispersion. (3) Step of adding a copper compound to the titanium oxide fine particle dispersion and reacting it. It can be manufactured by the manufacturing method having.

Process (1): In step (1), a peroxotitanic acid containing a tin compound is produced by reacting the raw material titanium compound, the tin compound, and hydrogen peroxide. As a reaction method, a basic substance is added to the raw material titanium compound to obtain titanium hydroxide, the contained impurity ions are removed, hydrogen peroxide is added to obtain peroxotitanic acid, and then a tin compound is added to obtain tin. Even in the method of using peroxotitanic acid, a basic substance is added after adding a tin compound to the raw material titanium compound to obtain tin-containing titanium hydroxide, the impurity ions contained are removed, and hydrogen peroxide is added to contain tin. A method using peroxotitanic acid may also be used.

Examples of the raw material titanium compound used as a raw material in the step (1) include inorganic acid salts such as titanium hydrochloride, nitrate and sulfate, and organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid and glycolic acid. Examples thereof include titanium hydroxide precipitated by adding an alkali to the aqueous solution of the above and hydrolyzing it, and two or more of these may be used in combination. The concentration of the aqueous solution of this raw material titanium compound is preferably 60% by mass or less, particularly preferably 30% by mass or less. Although the lower limit of the concentration is appropriately selected, it is preferably 1% by mass or more.

The tin compound-containing peroxotitanic acid aqueous solution may contain an alkaline or acidic substance for pH adjustment and the like. Examples of alkaline substances include ammonia, sodium hydroxide, calcium hydroxide and the like, and examples of acidic substances include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, phosphoric acid and hydrogen peroxide, and formic acid, citric acid and oxalic acid. Examples include organic acids such as lactic acid and glycolic acid. In this step (1), the amount of the tin compound used is as described above, but the amount of hydrogen peroxide used is preferably 1.5 to 5 times the total number of moles of Ti and Sn. The reaction temperature in the reaction of adding this hydrogen peroxide to convert the raw material titanium compound or titanium hydroxide into peroxotitanic acid is preferably 5 to 60 ° C, and the reaction time is 30 minutes to 24 hours. It is preferable to do so. Examples of the basic substance added to convert the raw material titanium compound into titanium hydroxide include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide or alkali earth metals, ammonia, alkanolamine, and alkylamines. Is added and used in an amount such that the pH of the aqueous solution of the raw material titanium compound is 7 or more. Further, the pH of the obtained aqueous solution of the tin compound-containing peroxo acid is preferably 1 to 7, particularly 4 to 7, from the viewpoint of handling safety.

Process (2): In step (2), an aqueous solution of peroxotitanic acid containing a tin compound is subjected to a hydrothermal reaction under high pressure at a temperature of 80 to 250 ° C., preferably 120 to 250 ° C. The appropriate reaction temperature is 80 to 250 ° C from the viewpoint of reaction efficiency and reaction controllability. As a result, peroxotitanic acid is converted into titanium oxide fine particles. In this case, the pressure is preferably a high pressure of about 0.01 to 4.5 MPa, particularly a high pressure of about 0.15 to 4.5 MPa, and the reaction time is preferably 1 minute to 24 hours. By this step (2), a titanium oxide fine particle dispersion containing a peroxotitanium component and a tin component is obtained.

Process (3): In the step (3), the copper compound is added to the titanium oxide fine particle dispersion obtained in the step (2) and reacted. The reaction method may be a method of adding a copper compound to the titanium oxide fine particle dispersion and stirring at room temperature, or a method of adding the copper compound to the titanium oxide fine particle dispersion and hydrothermally treating the mixture at a temperature of 80 to 250 ° C. .. In this case, the reaction time is preferably 1 minute to 3 hours.

Examples of the copper compound used as a raw material in step (3) include inorganic acid salts such as copper hydrochloride, nitrate and sulfate, and organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid and glycolic acid. Examples thereof include complexes such as copper hydroxide and copper tetraammine complex precipitated by adding an alkali to an aqueous solution and hydrolyzing the mixture, and two or more of these may be used in combination. The titanium oxide-based fine particle dispersion thus obtained is used for forming a photocatalytic film on the surface of various base materials, for example, an inorganic base material such as glass or an organic base material such as a polyester film. Can be done. In this case, as a method for forming the photocatalyst film, a known method may be adopted for coating and drying, and various thicknesses of the photocatalyst film may be selected, but the thickness is usually in the range of 50 nm to 10 μm. The formed photocatalytic film is transparent, gives a good photocatalytic action in the ultraviolet region as in the conventional case, and is also excellent in visible light responsiveness.

<p> Examples and comparative examples will be shown below to describe the present invention in detail, but the present invention is not limited to the following examples. The various measurements in the present invention were carried out as follows.</p><p>(1) Average particle size of titanium oxide fine particles in the dispersion (D₅₀) Average particle size of titanium oxide fine particles in the dispersion (D₅₀) Was measured using a particle size distribution measuring device (trade name "Nanotrack particle size analyzer UPA-EX", Nikkiso Co., Ltd.).</p><p>(2) Transparency of photocatalytic thin film Measure the HAZE value (%) of the glass plate that is the base material. Next, the dispersion liquid is applied onto the glass and dried to prepare a photocatalytic thin film, and the HAZE value of the glass plate in the prepared state is measured. The HAZE value of the photocatalytic thin film is obtained from the difference. The HAZE value was measured using a HAZE meter (trade name "Digital Haze Meter NDH-200", Nippon Denshoku Kogyo Co., Ltd.). The transparency of the photocatalytic thin film was evaluated according to the following criteria based on the difference in the required HAZE values.</p><p>Good (indicated as ) The difference is + 1% or less. Slightly defective (displayed as ) ... The difference exceeds + 1% and + 3% or less. Defective (indicated as x) The difference exceeds + 3%.</p><p>(3) Acetaldehyde gas decomposition performance test of photocatalytic thin film (under visible light irradiation) The activity of the photocatalytic thin film prepared by applying and drying the dispersion was evaluated by the decomposition reaction of acetaldehyde gas. The evaluation was performed by the distribution type gas decomposition performance evaluation method. Specifically, the volume is 12.5 cm³An evaluation sample in which a photocatalytic thin film was formed on a substrate made of 5 cm square glass was placed in a quartz glass cell, and acetaldehyde gas with a concentration of 250 ppm adjusted to a humidity of 50% was flowed into the cell at a flow rate of 5 mL · s.^-1The fluorescent lamp installed at the top of the cell radiated light so that the illuminance would be 8000 LUX. When the acetaldehyde gas is decomposed by the photocatalyst on the thin film, the concentration of the acetaldehyde gas in the gas flowing out from the cell decreases. Therefore, the amount of acetaldehyde gas decomposition can be determined by measuring the concentration. The acetaldehyde gas concentration was measured using a gas chromatograph (trade name "GC-8A", Shimadzu Corporation).</p><p>(4) Self-cleaning performance test of photocatalytic thin film (under visible light irradiation) The activity of the photocatalytic thin film prepared by applying the dispersion liquid on the slide glass and drying it was evaluated by the decomposition reaction of oleic acid.</p><p> Specifically, 0.5% by mass oleic acid is applied to the surface of the thin film with a dip coater and dried to obtain a sample for evaluating photocatalytic activity. The sample is irradiated with the light of a fluorescent lamp at an illuminance of 10,000 LUX. When the oleic acid on the thin film surface is decomposed, the thin film surface becomes hydrophilic and the water contact angle gradually decreases. Therefore, the water contact angle on the sample surface is measured every hour. The water contact angle was measured using a contact angle meter (trade name "CA-A", Kyowa Interface Science Co., Ltd.).</p><p>[Example 1] (1) Tin (IV) chloride is added to a 36 mass% titanium (IV) chloride aqueous solution so that Ti / Sn (molar ratio) is 20, and this is diluted 10-fold with pure water, and then this aqueous solution is used. A precipitate of titanium hydroxide was obtained by gradually adding 10% by mass of aqueous ammonia to neutralize and hydrolyze the mixture. The pH of the solution at this time was 9. The obtained titanium hydroxide precipitate was deionized by repeating addition of pure water and decantation. 30% by mass of hydrogen peroxide solution is added to the titanium hydroxide precipitate after this deionization treatment so that the hydrogen peroxide / titanium hydroxide (molar ratio) is 2.5 or more, and then the mixture is sufficiently stirred at room temperature for 24 hours. It was reacted. Then, pure water was added to adjust the concentration to obtain a yellow transparent tin-containing peroxotitanic acid solution (a) (solid content concentration: 1% by mass).</p><p> (2) Copper sulfate was dissolved in pure water to obtain a 1% by mass copper sulfate aqueous solution (b).</p><p> (3) 400 mL of the tin-containing peroxotitanic acid aqueous solution (a) obtained in (1) was placed in an autoclave having a volume of 500 mL, and this was hydrothermally treated at a pressure of 1.6 MPa, 200 ° C. for 120 minutes. Then, the reaction mixture in the autoclave was discharged to a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapid cooling to obtain a titanium oxide-based fine particle dispersion. ..</p><p> To the titanium oxide-based fine particle dispersion obtained in (3), add and mix the copper sulfate aqueous solution (b) obtained in (2) so that the amount of metallic copper is 0.2% by mass with respect to titanium oxide, and mix at 150 ° C. The visible light-responsive titanium oxide-based fine particle dispersion (A) of the present invention containing 1% by mass of titanium oxide and 1% by mass of the peroxotitanium component with respect to titanium oxide was obtained by hydrothermal treatment for 30 minutes. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 12 nm.</p><p>[Example 2] (4) Tin (IV) chloride is added to a 36 mass% titanium (IV) chloride aqueous solution so that Ti / Sn (molar ratio) is 5, and this is diluted 10-fold with pure water, and then this aqueous solution is used. A precipitate of titanium hydroxide was obtained by gradually adding 10% by mass of aqueous ammonia to neutralize and hydrolyze the mixture. The pH of the solution at this time was 9. The obtained titanium hydroxide precipitate was deionized by repeating addition of pure water and decantation. 30% by mass of hydrogen peroxide solution is added to the titanium hydroxide precipitate after this deionization treatment so that the hydrogen peroxide / titanium hydroxide (molar ratio) is 2.5 or more, and then the mixture is sufficiently stirred at room temperature for 24 hours. It was reacted. Then, pure water was added to adjust the concentration to obtain a yellow transparent tin-containing peroxotitanic acid solution (c) (solid content concentration: 1% by mass).</p><p> (5) Copper nitrate was dissolved in pure water to obtain a 1% by mass copper nitrate aqueous solution (d).</p><p> (6) 400 mL of the tin-containing peroxotitanic acid aqueous solution (c) obtained in (4) was charged into an autoclave having a volume of 500 mL, and this was hydrothermally treated at a pressure of 0.5 MPa, 150 ° C. for 120 minutes. Then, the reaction mixture in the autoclave was discharged to a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapid cooling to obtain a titanium oxide-based fine particle dispersion. ..</p><p> To the titanium oxide-based fine particle dispersion obtained in (6), add the copper sulfate aqueous solution (d) obtained in (5) so that the amount of metallic copper is 0.25% by mass with respect to titanium oxide, mix and oxidize. The visible light responsive titanium oxide-based fine particle dispersion (B) of the present invention containing 1% by mass of titanium and 2% by mass of the peroxotitanium component with respect to titanium oxide was obtained. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 10 nm.</p><p>[Example 3] (7) Titanium hydroxide is obtained by diluting a 36% by mass titanium (IV) chloride aqueous solution 10-fold with pure water, and then gradually adding 10% by mass of aqueous ammonia to neutralize and hydrolyze the aqueous solution. Dilution was obtained. The pH of the solution at this time was 10. The obtained titanium hydroxide precipitate was deionized by repeating addition of pure water and decantation. 30% by mass of hydrogen peroxide solution is added to the titanium hydroxide precipitate after this deionization treatment so that the hydrogen peroxide / titanium hydroxide (molar ratio) is 2.5 or more, and then the mixture is sufficiently stirred at room temperature for 24 hours. It was reacted. Then, pure water was added to adjust the concentration to obtain a yellow transparent peroxotitanic acid solution (e) (solid content concentration: 1% by mass).</p><p> (8) Tin chloride pentahydrate was dissolved in pure water to obtain a 10% by mass tin chloride aqueous solution (f).</p><p> (9) In an autoclave with a volume of 500 mL, 350 mL of the peroxotitanate aqueous solution (e) obtained in (7) and 10 mL of the tin chloride aqueous solution (f) obtained in (8) were charged, and these were placed at 150 ° C. for 120 minutes. Hydrothermally treated. Then, the reaction mixture in the autoclave was discharged to a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapid cooling to obtain a titanium oxide-based fine particle dispersion. ..</p><p> To the titanium oxide-based fine particle dispersion obtained in (9), add the copper sulfate aqueous solution (d) obtained in (5) so that the amount of metallic copper is 0.3% by mass with respect to titanium oxide, mix and oxidize. A visible light-responsive titanium oxide-based fine particle dispersion (C) of the present invention containing 1% by mass of titanium and 2% by mass of a peroxotitanium component with respect to titanium oxide was obtained. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 25 nm.</p><p>[Comparative example 1] (10) A titanium oxide-based fine particle dispersion (D) was obtained in the same manner as in Example 1 except that the copper sulfate aqueous solution was not added. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 9 nm.</p><p>[Comparative example 2] (11) 400 mL of the peroxotitanic acid aqueous solution (e) obtained in Example 3 was charged into an autoclave having a volume of 500 mL, and this was hydrothermally treated at 150 ° C. for 120 minutes. Then, the reaction mixture in the autoclave was discharged to a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapid cooling to obtain a titanium oxide-based fine particle dispersion. ..</p><p> To the titanium oxide-based fine particle dispersion obtained in (11), add the copper sulfate aqueous solution (d) obtained in (5) so that the amount of metallic copper is 0.25% by mass with respect to titanium oxide, mix and oxidize. A titanium-based fine particle dispersion (E) was obtained. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 25 nm.</p><p>[Comparative example 3] A titanium oxide fine particle dispersion (F) was obtained in the same manner as in Example 1 except that the hydrothermal treatment temperature was set to 60 ° C. The average particle size of the titanium oxide fine particles in the obtained dispersion could not be measured because the amount of particles produced was small. In this comparative example, since the amount of titanium oxide fine particles produced was extremely small, other characteristics were not measured.</p><p> Silica-based binder (colloidal silica, trade name: Snowtex 20 (manufactured by Nissan Chemical Industries, Ltd.)) is added to the dispersions prepared in Examples 1 to 3 and Comparative Examples 1 and 2.₂/ SiO₂After the addition at a ratio of 1.5, the glass plate was coated with a dip coater and dried to form a photocatalytic thin film having a film thickness of 150 nm, and an evaluation sample was obtained.</p><p> Table 1 shows the reaction conditions and average particle size of Examples and Comparative Examples, the transparency evaluation of the photocatalytic thin film, the measurement results of the water contact angle 5 hours after irradiation with a fluorescent lamp in the self-cleaning performance test, and the fluorescent lamp in the acetaldehyde gas decomposition test. The gas decomposition rate after 90 minutes of irradiation is shown together.</p><p> As can be seen from the results of Comparative Example 1, sufficient visible light activity cannot be obtained unless the copper component is added.</p><p> As can be seen from the results of Comparative Example 2, sufficient visible light activity cannot be obtained unless the tin component is added.</p><p> As can be seen from the results of Comparative Example 3, if the reaction temperature is too low, the conversion to titanium oxide becomes very slow.</p><p> As can be seen from the results of Examples 1 to 3, the decomposition of acetaldehyde and oleic acid (that is, photocatalytic activity) under fluorescent light irradiation can be improved by containing the copper component and the tin component in the dispersion liquid. I understand.</p><p><tables num="1"><img file="JP2011240246A_D0001.tif" /></tables></p>

The titanium oxide-based fine particle dispersion of the present invention can be applied to various substrates composed of inorganic substances such as glass and metal, and organic substances such as polymer films (PET film, etc.) by adding a binder. It is useful for producing a photocatalytic thin film, and particularly useful for producing a transparent photocatalytic thin film on a polymer film.