Visible light responsive type titanium oxide-based particulate dispersion 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. Specifically, the present invention relates to a visible light responsive titanium oxide fine particle dispersion containing a copper component, peroxotitanium and titanium oxide fine particles in an aqueous dispersion medium. Regarding.

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 applying the dispersion liquid to 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 increase 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 (Patent Documents 4 and 5) prepared by hydrothermal treatment of a titanium-containing compound solution. 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. It is a point.

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, the room is illuminated by a light source such as a fluorescent lamp in which visible light occupies most of the light. In space, 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 Patent Application Laid-Open No. 01-003020</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 06-279725</text></patcit><patcit num="3"><text>Japanese Patent Application Laid-Open No. 07-247119</text></patcit><patcit num="4"><text>JP 2009-148700</text></patcit></p>

<p> Therefore, an object of the present invention is to provide a visible light responsive titanium oxide-based dispersion liquid which can produce a titanium oxide-based photocatalyst thin film having excellent transparency and visible light responsiveness and has excellent dispersion stability.</p>

<p> The present invention provides means for solving the above problems. 50% cumulative distribution diameter (D) measured by an aqueous dispersion medium and the dynamic scattering method dispersed in the dispersion medium.₅₀) Is 50 nm or less, and a titanium oxide-based fine particle dispersion containing the copper component and peroxotitanium contained in the dispersion medium and having a peroxotitanium content of 0.1 to 20% by mass. provide.</p>

<p> The visible light responsive titanium oxide fine particle dispersion provided in the present invention has excellent dispersion stability of titanium oxide fine particles, and a highly transparent photocatalytic thin film having visible light responsiveness can be easily produced.</p>

&lt;Titanium oxide-based fine particle dispersion&gt; In the titanium oxide-based fine particle dispersion of the present invention, titanium oxide fine particles are highly dispersed in an aqueous medium, and peroxotitanium and a copper component are further contained.

Aqueous medium: An aqueous medium is used as the dispersion medium. Examples of the aqueous medium include water, a hydrophilic organic solvent mixed with water at an arbitrary ratio, and a mixed solvent with water. As the hydrophilic organic solvent, alcohols such as methanol, ethanol and isopropanol are preferable. The aqueous medium is preferably water, and for example, deionized water, distilled water, pure water, or the like is used.

Titanium oxide fine particles: The titanium oxide fine particles dispersed in the dispersion liquid of the present invention have a 50% cumulative distribution diameter (D) based on the volume measured by a dynamic scattering method using a laser beam.₅₀) (Hereinafter abbreviated as "average particle size") is 50 nm or less, preferably 30 nm or less. Usually 5 nm or more.

The concentration of the titanium oxide fine particles is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass in the dispersion liquid, because it is easy to prepare a photocatalyst thin film having a required thickness.

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

In the titanium oxide-based fine particle dispersion of the present invention, peroxotitanium has an action of satisfactorily dispersing titanium oxide fine particles. The concentration of the peroxotitanium 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: In the present invention, the copper component has an action of enhancing the visible light responsiveness of the obtained photocatalytic thin film. The state of existence of the copper component is not limited, and may be, for example, metallic copper, oxides, hydroxides, nitrates, sulfates, halides, complex compounds and the like. When the copper component is a water-soluble copper compound, it may exist in the form of copper ions. At least a part of the copper component is supported on the surface of the titanium oxide fine particles. Other parts are dissolved and / or dispersed in the dispersion.

The content of the copper component in terms of metallic copper is preferably 0.01 to 5% by mass, more preferably 0.1 to 1% by mass, based on the titanium oxide fine particles. If the content of the copper component is too large, the visible light responsiveness may not be sufficiently exhibited.

&lt;Manufacturing method of titanium oxide-based fine particle dispersion&gt; The above titanium oxide fine particle dispersion is (1) A process of heating a peroxotitanic acid aqueous solution at 80 to 250 ° C. under high pressure to convert peroxotitanate into titanium oxide fine particles. (2) In step (1), when the conversion rate of peroxotitanic acid to titanium oxide fine particles is 80 to 95%, a copper-containing solution is added to the reaction solution, and then the reaction is further carried out at 80 to 250 ° C. Process, (3) A step of stopping the reaction after the addition of the copper-containing solution at the stage where the conversion rate is 95 to 99.9%. It can be manufactured by the manufacturing method having.

Process (1): In the step (1), the titanium-containing raw material solution (that is, the peroxotitanic acid aqueous solution) is subjected to a hydrothermal reaction at a temperature of 80 to 250 ° C., preferably 120 to 250 ° C. under high pressure. The appropriate reaction temperature is 80 to 250 ° C from the viewpoint of reaction efficiency and reaction controllability. As a result, peroxotitanium acid is converted into titanium oxide fine particles while passing through an intermediate product such as the peroxotitanium complex represented by the above formula.

The method of the present invention is preferably carried out in step (2) using a pressure resistant reaction vessel provided with means for press-fitting the copper compound. For example, an autoclave to which a pressure-resistant glass cylinder can be attached or a plurality of tubes are provided, and a titanium-containing raw material solution can be introduced into a reaction vessel from one tube, and a copper-containing solution can be introduced into the reaction vessel from another tube. A pressure-resistant tube type reaction vessel can be mentioned. When a pressure-resistant tube type reaction vessel such as an autoclave is used, a hydrothermal reaction is carried out under saturated vapor pressure at a predetermined reaction temperature.

As the peroxotitanate aqueous solution used as a raw material in the step (1), an aqueous solution of peroxotitanate, which is a water-soluble complex ion obtained by peroxoizing titanium hydroxide, is used. The concentration of peroxotitanic acid is preferably 0.01 to 50% by mass, more preferably 0.01 to 20% by mass, and even more preferably 0.01 to 10% by mass with respect to the aqueous solution. If the concentration is too high, the generated titanium oxide particles tend to aggregate.

The 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, potassium 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.

Process (2) The copper-containing solution used in step (2) is an aqueous solution containing a copper-containing compound. For example, inorganic acid salts such as copper hydrochloride, nitrate and sulfate, organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid and glycolic acid, and complexes such as tetraammine complex can be mentioned, and two or more of these can be combined. May be used.

In step (2), the titanium-containing raw material solution was heated at 80 to 250 ° C, preferably 120 to 250 ° C, and 80 to 95%, preferably 90 to 95% of peroxotitanic acid was converted into titanium oxide fine particles. At this point, the copper-containing solution is mixed with the reaction solution and heated at the same temperature. As a result, it is considered that at least a part of the copper component adheres to and is supported on the surface of the titanium oxide fine particles. If the heating temperature is less than 80 ° C, the reaction time becomes long, which is not preferable, and if it exceeds 250 ° C, the reaction is extremely fast and control becomes difficult, which is not preferable. If the conversion rate of peroxotitanic acid to titanium oxide fine particles when the copper-containing solution is added is less than 80%, the photocatalytic action cannot be sufficiently improved by adding the copper component. This is probably because the amount of titanium oxide fine particles produced is insufficient. Further, when the conversion rate exceeds 95%, the generated titanium oxide fine particles are likely to cause aggregation.

When the above-mentioned pressure-resistant reaction vessel is used, the copper-containing solution is added to the reaction solution by pressurizing and press-fitting with an inert gas such as nitrogen gas using the above-mentioned glass cylinder or the like. The time required for press-fitting is preferably short, preferably 60 seconds or less, and more preferably 30 seconds or less in order to ensure the uniformity of the reaction. The pressure required for the press-fitting is usually 0.1 to 5 MPa.

Process (3): The reaction is continued after the addition of the copper-containing solution in step (2), but the reaction is stopped when the conversion rate of peroxotitanic acid to titanium oxide fine particles reaches 95 to 99.9%, preferably 98 to 99.9%. If the conversion rate at the time of reaction termination is less than 95%, the photocatalytic action cannot be sufficiently improved by adding the copper component, and if the conversion rate exceeds 99.9%, the peroxotitanium content in the obtained dispersion is not sufficiently obtained. Is too small and the stability of the dispersed state is reduced. The reaction time from the addition of the copper-containing solution to the termination of the reaction is 30 seconds to 5 minutes, preferably 40 seconds to 2 minutes. One of the preferred methods of stopping the reaction is to reduce the temperature of the reaction mixture. The temperature decrease is preferably rapid, preferably within 2 minutes, more preferably within 1 minute, to 60 ° C or less, preferably 40 ° C or less. Such quenching can be performed, for example, by discharging the reaction mixture in the autoclave into a container held in a water bath at 20 ° C. using a sampling tube. If the temperature is slowly lowered, the particle size of titanium oxide tends to increase, which is not preferable.

The conversion rate as the reaction progresses can be measured as follows. For example, a part of the reaction mixture is extracted from the reaction vessel, sulfuric acid is added, and then hydrogen peroxide solution is added to cause the reaction to convert the amorphous titanium component in the reaction mixture into a peroxotitanium complex, and then the spectrophotometry. Measure the absorbance at 410 nm with a meter. The conversion rate can be determined by monitoring the absorbance.

<p> Examples will be shown below to describe the present invention in detail, but the present invention is not limited thereto. In addition, various measurements in this invention were performed as follows.</p><p>(1) Conversion rate of peroxotitanic acid to titanium oxide fine particles The conversion rate of peroxotitanic acid to titanium oxide fine particles was measured at 410 nm using a raw material titanium solution (peroxotitanate aqueous solution) before the start of the reaction using an ultraviolet visible spectrophotometer (trade name UVmini1240, Shimadzu Corporation). Measure the absorbance (a1). Sulfuric acid is added to the reaction mixture sampled during the reaction to make it acidic, and then hydrogen peroxide is added to cause the reaction to develop color. For the sample treated in this way, the absorbance (a2) at 410 nm is measured in the same manner as above. The conversion rate is calculated from the relative ratio of the absorbance (a2) to the absorbance (a1).</p><p>(2) 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>(3) 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 is 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 is + 3% or less. Defective (indicated as x) ... The difference exceeds + 3%.</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>(5) Acetaldehyde gas decomposition performance test of photocatalytic thin film (under UV 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 cell made of quartz glass, and acetaldehyde gas at a concentration of 250 ppm adjusted to a humidity of 50% was flowed into the cell at a flow rate of 5 mL · s.^-1UV light intensity 1mW / cm from the UV lamp installed at the top of the cell²Irradiated with. When the acetaldehyde gas is decomposed by the photocatalyst on the thin film, the concentration of acetaldehyde in the gas flowing out of 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>-Example 1- (1) Titanium hydroxide is obtained by diluting a 60% by mass titanium (IV) chloride aqueous solution 100-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. To the titanium hydroxide precipitate after this deionization treatment, 30% by mass hydrogen peroxide solution was added so that the hydrogen peroxide / titanium hydroxide (molar ratio) was 4 or more, and then the mixture was allowed to stand at room temperature for 24 hours. It was allowed to react sufficiently. Then, pure water was added to adjust the concentration to obtain a yellow transparent peroxotitanic acid aqueous solution (A) (solid content concentration: 1% by mass).</p><p>(2) 100 mL of pure water was added to 90 mg of copper sulfate to obtain a copper sulfate aqueous solution (B).</p><p>(3) A glass cylinder containing 50 mL of the copper sulfate aqueous solution (B) obtained in (2) was attached to an autoclave having a volume of 500 mL. Next, 400 mL of the peroxotitanic acid aqueous solution (A) obtained in (1) was charged into the autoclave, and this was heated to 200 ° C. When the conversion rate of peroxotitanate to titanium oxide fine particles in the peroxotitanate aqueous solution (A) reaches 85%, the copper sulfate aqueous solution (B) in the glass cylinder is pressurized with nitrogen and press-fitted into the autoclave. did. The time required for press fitting was 10 seconds. The temperature of the obtained mixed solution reached 200 ° C in 5 seconds after the completion of press-fitting. Hydrothermal treatment was performed at this temperature for 1 minute. 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. .. The conversion rate of peroxotitanic acid into titanium oxide fine particles in the peroxotitanic acid aqueous solution (A) was 98%. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 22 nm. When the dispersion was left to stand for 24 hours, a uniform dispersion state was maintained, and no precipitation of titanium oxide fine particles was observed.</p><p>-Example 2- (1) A 15% by mass titanium sulfate solution is diluted 20-fold with pure water, and then 10% by mass of aqueous ammonia is gradually added to this aqueous solution for neutralization and hydrolysis to precipitate a titanium hydroxide. Got 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. To the titanium hydroxide precipitate after this deionization treatment, add 30% by mass hydrogen peroxide solution so that the hydrogen peroxide / titanium hydroxide (molar ratio) is 4 or more, and leave it at room temperature for a whole day and night. It was reacted. Then, pure water was added to adjust the concentration to obtain a yellow transparent peroxotitanic acid aqueous solution (C) (solid content concentration: 1.5% by mass).</p><p>(2) 100 mL of pure water was added to 90 mg of copper nitrate to obtain a copper nitrate aqueous solution (D).</p><p>(3) A glass cylinder containing 50 mL of the copper nitrate aqueous solution (D) obtained in (2) was attached to an autoclave having a volume of 500 mL. Next, 400 mL of the peroxotitanic acid aqueous solution (C) obtained in (1) was charged into the autoclave and heated to 150 ° C. When the conversion rate of peroxotitanate to titanium oxide fine particles in the peroxotitanate aqueous solution (C) reaches 90%, the copper nitrate aqueous solution (D) in the glass cylinder is pressurized with nitrogen and press-fitted into the autoclave. did. The time required for press fitting was 10 seconds. The temperature of the mixed solution reached 150 ° C 5 seconds after the press-fitting was completed. Hydrothermal treatment was performed at this temperature for 30 seconds. 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. In this way, a titanium oxide-based fine particle dispersion was obtained. The conversion rate of peroxotitanic acid into titanium oxide fine particles in the peroxotitanic acid aqueous solution (C) was 98%. The average particle size of the titanium oxide fine particles in the dispersion was measured and found to be 23 nm. When the dispersion was left to stand for 24 hours, a uniform dispersion state was maintained, and no precipitation of titanium oxide fine particles was observed.</p><p>-Comparative example 1- A glass cylinder containing 50 mL of the copper sulfate aqueous solution (B) obtained in Example 1 was attached to an autoclave having a volume of 500 mL. Next, 400 mL of the peroxotitanic acid aqueous solution (A) obtained in Example 1 was charged into the autoclave, and this was heated to 50 ° C. Since the conversion rate of peroxotitanic acid to titanium oxide fine particles in the peroxotitanic acid aqueous solution (A) was less than 10% even after the lapse of 24 hours, the reaction was terminated there.</p><p>-Comparative example 2- 400 mL of the peroxotitanic acid aqueous solution (A) obtained in Example 1 was charged into an autoclave having a volume of 500 mL, and this was heated to 200 ° C. Hydrothermal treatment was performed until the conversion rate of peroxotitanic acid into titanium oxide fine particles in the peroxotitanic acid aqueous solution (A) reached 98%. 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. .. The average particle size of the titanium oxide fine particles in the dispersion was measured and found to be 19 nm.</p><p>-Comparative example 3- A glass cylinder containing 50 mL of the copper sulfate aqueous solution (B) obtained in Example 1 was attached to an autoclave having a volume of 500 mL. Next, 400 mL of the peroxotitanic acid aqueous solution (A) obtained in Example 1 was charged into the autoclave, and this was heated to 200 ° C. When the conversion rate of peroxotitanate to titanium oxide fine particles in the peroxotitanate aqueous solution (A) reaches 50%, the copper sulfate aqueous solution (B) in the glass cylinder is pressurized with nitrogen and press-fitted into the autoclave. did. The time required for press fitting was 10 seconds. The temperature of the obtained mixed solution reached 200 ° C. 5 seconds after the completion of press-fitting. Hydrothermal treatment was performed at this temperature for 60 seconds. 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. .. The conversion rate of peroxotitanic acid into titanium oxide fine particles in the peroxotitanic acid aqueous solution (A) was 55%. The average particle size of the titanium oxide fine particles in the dispersion was measured and found to be 18 nm.</p><p>-Comparative example 4- A glass cylinder containing 50 mL of the copper sulfate aqueous solution (B) obtained in (2) of Example 1 was attached to an autoclave having a volume of 500 mL. Next, 400 mL of the peroxotitanic acid aqueous solution (A) obtained in (1) of Example was charged into the autoclave, and this was heated to 200 ° C. When the conversion rate of peroxotitanic acid into titanium oxide fine particles in the peroxotitanate aqueous solution (A) reaches 85%, the copper sulfate aqueous solution (B) in the glass cylinder is pressurized with nitrogen and press-fitted into the autoclave. did. The time required for press fitting was 10 seconds. The temperature of the obtained mixed solution reached 200 ° C in 5 seconds after the completion of press-fitting. Hydrothermal treatment was performed at this temperature for 5 minutes. Then, the reaction mixture in the autoclave was discharged into a container via a sampling tube to obtain a titanium oxide-based fine particle dispersion. The conversion rate of peroxotitanic acid into titanium oxide fine particles in the peroxotitanic acid aqueous solution (A) was 100%. The average particle size of the titanium oxide fine particles in the obtained dispersion was measured and found to be 278 nm. When the dispersion was left to stand for 24 hours, precipitation of titanium oxide fine particles was observed on the bottom surface of the container. In this comparative example, the transparency of the thin film was poor, so other characteristics were not measured.</p><p> Silica-based binder (coloidal silica, trade name: Snowtex 20 (manufactured by Nissan Chemical Industries, Ltd.)) was added to the dispersions prepared in Examples 1 and 2 and Comparative Example 2-4.₂/ SiO₂After the addition at a ratio of 1.5, it was applied on a slide glass 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 water contact angle measurement results 6 hours after irradiation with a fluorescent lamp in the self-cleaning performance test, and UV irradiation in the acetaldehyde gas decomposition test. The gas decomposition rate after 90 minutes is shown together.</p><p> As can be seen from the results of Comparative Example 1, 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 Comparative Example 3, when the copper-containing solution is added and mixed at the stage where the conversion rate is low, the amount of photocatalyst becomes sufficient. Moreover, the average particle size of the titanium oxide fine particles is increased, and the transparency is impaired.</p><p> In Comparative Example 4, as a result of proceeding with the reaction to a conversion rate of 100%, the obtained dispersion did not contain peroxotitanium, and the average particle size became too large, so that the stability of the dispersion was low and the photocatalyst was used. The transparency of the thin film also deteriorated.</p><p> As can be seen from the results of the self-cleaning performance tests of Examples 1 and 2 and Comparative Example 2, the decomposition of oleic acid (that is, photocatalytic activity) under fluorescent lamp irradiation is good by containing the copper component in the dispersion. It turns out that it becomes. In the examples of the present invention, the water contact angle was reduced to an order of magnitude showing superhydrophilicity.</p><p><tables num="1"><img file="JP2011136297A_D0001.tif" /></tables></p>

The titanium oxide fine particle dispersion of the present invention is useful for producing a photocatalytic thin film by applying it to various substrates composed of an inorganic substance such as glass or metal and an organic substance such as polyethylene terephthalate film. In particular, it is suitable for forming a photocatalytic thin film on a polymer film.