JP2011240246A - Visible light-responsive titanium oxide particle dispersion liquid and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visible light-responsive titanium oxide dispersion liquid in which the dispersion stability of the titanium oxide microparticle is excellent, and from which a photocatalyst having a visible light responsibility and a high transparency can simply be fabricated; and to provide a method for manufacturing the same.SOLUTION: The visible light-responsive titanium oxide dispersion liquid comprises the titanium oxide microparticle dispersed in an aqueous dispersion medium, a peroxotitanium component, a copper and a tin components, wherein the content of the peroxotitanium component is 0.1-20 mass% to the titanium oxide. The manufacturing method of a visible light-responsive titanium oxide dispersion liquid comprises the steps of: (1) manufacturing a peroxotitanic acid containing a tin compound from a titanium compound, the tin compound and hydrogen peroxide as raw materials; (2) heating the peroxotitanic acid aqueous solution containing the tin compound under high pressure at 80-250°C to obtain a titanium oxide microparticle dispersion liquid containing the peroxotitanium component and the tin component; and (3) adding a copper compound to the titanium oxide microparticle dispersion liquid to react those.

Description

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

  Titanium oxide is a precursor for composite oxides such as pigments, UV shielding agents, catalysts, photocatalysts, catalyst carriers, adsorbents, ion exchangers, fillers, reinforcing agents, ceramic raw materials, and perovskite composite oxides. It is used as a primer for the body and magnetic tape.

  Among them, the photocatalytic titanium oxide fine particles are based on the photocatalytic coating film formed by coating the dispersion on the surface of various substrates, which decomposes organic substances and makes the film surface hydrophilic by photocatalytic action of titanium oxide. It is widely used for cleaning the surface of materials, deodorizing, antibacterial and so on. In order to enhance the photocatalytic activity, it is necessary to increase the contact area between the photocatalyst particles and the substance to be decomposed, and for this purpose, the primary particle diameter 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 properties of the substrate.

  As a method for producing a titanium oxide fine particle dispersion, 1) a method in which a fine powder of titanium oxide is dispersed 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 Document 4) prepared by hydrothermal treatment of a titanium-containing compound solution. The problem with these production methods is that ultrafine particles having an average particle diameter of 50 nm or less are likely to agglomerate, so that a great deal of labor is required to disperse to the primary particles, and in some cases it is impossible to disperse to the primary particles. It is.

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

JP-A-01-003020 Japanese Patent Laid-Open No. 06-279725 Japanese Patent Laid-Open No. 07-247119 JP 2009-148700 A

  The present invention has been made in view of the above circumstances, and is capable of easily producing a highly transparent photocatalytic thin film having excellent dispersion stability of titanium oxide fine particles and having visible light responsiveness. It is an object to provide a system dispersion and a method for producing the same.

  As a result of intensive studies to achieve the above object, the present inventors have produced peroxotitanic acid containing a tin compound using a raw material titanium compound, a tin compound and hydrogen peroxide, and then subjecting this to high pressure. After obtaining a titanium oxide fine particle dispersion by hydrothermal reaction, a titanium compound fine particle dispersion containing a peroxotitanium component, a copper component, and a tin component is obtained by adding and reacting a copper compound. This titanium oxide dispersion Has found that it is excellent in dispersion stability of titanium oxide fine particles, and that a highly transparent photocatalytic thin film having visible light responsiveness can be easily produced from this titanium oxide dispersion, and has led to the present invention. .

Accordingly, the present invention provides the following visible light responsive titanium oxide dispersion and a method for producing the same.
Claim 1:
In the aqueous dispersion medium, fine particles of titanium oxide are dispersed, 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:
2. The visible light responsive titanium oxide fine particle dispersion according to claim 1, wherein the content of the copper component in terms of metallic copper is 0.01 to 5 mass% with respect to titanium oxide.
Claim 3:
3. The visible light responsive titanium oxide fine particle dispersion according to claim 1, wherein a content of the tin component is 1 to 1000 in terms of a molar ratio (Ti / Sn) to titanium oxide.
Claim 4:
The visible light responsive type according to any one of claims 1 to 3, wherein the titanium oxide fine particles have a 50% cumulative distribution diameter (D50) measured by a dynamic scattering method of ₅₀ nm or less. Titanium oxide fine particle dispersion.
Claim 5:
(1) a step of 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) a titanium oxide fine particle dispersion. The method for producing a visible light responsive titanium oxide fine particle dispersion according to any one of claims 1 to 4, further comprising a step of adding a copper compound to the reaction.

  INDUSTRIAL APPLICABILITY According to the present invention, a visible light responsive titanium oxide dispersion and a production thereof that can easily produce a highly transparent photocatalytic thin film having excellent dispersion stability of titanium oxide fine particles and having visible light responsiveness. A method can be provided.

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

・ Aqueous dispersion medium:
An aqueous solvent is used as the aqueous dispersion medium. Examples of the aqueous solvent include a mixed solvent of water and a hydrophilic organic solvent mixed with water at an arbitrary ratio. As 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 volume-based 50% cumulative distribution diameter (D ₅₀ ) (hereinafter referred to as “average particle diameter”) measured by a dynamic scattering method using laser light. The thickness is preferably 50 nm or less, and more preferably 30 nm or less. Usually, the lower limit is not particularly limited, but is preferably 5 nm or more.

  The concentration of the titanium oxide fine particles is preferably from 0.01 to 20% by mass, and particularly preferably from 0.5 to 10% by mass in the dispersion, in that a photocatalytic thin film having a required thickness can be easily produced.

Peroxotitanium component:
Here, the “peroxotitanium component” means a titanium oxide-based compound containing a Ti—O—O—Ti bond, and a peroxotitanium complex formed by the reaction of peroxotitanic acid and Ti (VI) with hydrogen peroxide. Include.

  In the titanium oxide-based fine particle dispersion of the present invention, the peroxotitanium component has a function of favorably dispersing titanium oxide. The density | concentration of a peroxotitanium component is 0.1-20 mass% with respect to a titanium oxide fine particle, Preferably it is 0.1-5 mass%. When 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:
A copper component has the effect | action which improves the decomposition activity of the photocatalyst thin film obtained. The presence state of the copper component is not limited, and may be any of, for example, metallic copper, oxide, hydroxide, nitrate, sulfate, halide, and complex compound. 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.

  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 with respect to the titanium oxide fine particles. When there is too much content of a copper component, photocatalytic activity may not fully be exhibited.

-Tin component:
A tin component has the effect | action which improves the visible light responsiveness of the photocatalyst thin film obtained. The presence state of the tin component is not limited, and may be any of metal tin, oxide, hydroxide, nitrate, sulfate, halide, and complex compound, for example. 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.

  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. When the molar ratio exceeds 1000, the effect is insufficient. On the other hand, if it is smaller than 1, the content ratio of titanium oxide is lowered, and the photocatalytic effect may not be sufficiently exhibited.

<Production Method of Visible Light Responsive Titanium Oxide Fine Particle Dispersion>
The titanium oxide fine particle dispersion is
(1) a step of 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 under high pressure at 80 to 250 ° C. to convert it into a titanium oxide fine particle dispersion, and (3) adding a copper compound to the titanium oxide fine particle dispersion, It can manufacture with the manufacturing method which has the process made to react.

-Process (1):
In step (1), peroxotitanic acid containing a tin compound is produced by reacting a raw material titanium compound, a tin compound, and hydrogen peroxide. As a reaction method, a basic substance is added to a raw material titanium compound to form titanium hydroxide, impurity ions contained are removed, hydrogen peroxide is added to form peroxotitanic acid, a tin compound is added, and tin is added. Even in the method of containing peroxotitanic acid, a tin compound is added to the raw material titanium compound, then a basic substance is added to form tin-containing titanium hydroxide, 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 the raw material in the step (1) include inorganic acid salts such as titanium hydrochloride, nitrate and sulfate, organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid and glycolic acid, and the like. Examples thereof include titanium hydroxide precipitated by adding an alkali to the aqueous solution and hydrolyzing it, and two or more of these may be used in combination. The concentration of the aqueous solution of the raw material titanium compound is preferably 60% by mass or less, particularly preferably 30% by mass or less. In addition, although the minimum of a density | concentration is selected suitably, it is preferable that it is 1 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 the alkaline substance include ammonia, sodium hydroxide, and calcium hydroxide, and examples of the acidic substance include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, phosphoric acid, and hydrogen peroxide, formic acid, citric acid, oxalic acid, Examples include organic acids such as lactic acid and glycolic acid.
In this step (1), the amount of 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 hydrogen peroxide to the raw material titanium compound or titanium hydroxide to peroxotitanic acid is preferably 5 to 60 ° C., and the reaction time is 30 minutes to 24 hours. It is preferable.
The basic substance added to make the raw material titanium compound titanium hydroxide includes alkali metal or alkaline earth metal hydroxide such as sodium hydroxide and potassium hydroxide, ammonia, alkanolamine, alkylamine, etc. And is added and used in such an amount that the pH of the aqueous solution of the raw material titanium compound becomes 7 or more.
Moreover, it is preferable from the point of the safety | security of handling that the pH of the obtained tin compound containing peroxo acid aqueous solution is 1-7, especially 4-7.

-Process (2):
In the step (2), a peroxotitanic acid aqueous solution 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 reaction temperature is suitably 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 about 0.01 to 4.5 MPa, particularly 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 step (3), a copper compound is added to the titanium oxide fine particle dispersion obtained in step (2) and allowed to react. 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 a copper compound to the titanium oxide fine particle dispersion and hydrothermally treating 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 the step (3) include 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 the like. Examples include complexes such as copper hydroxide and copper tetraammine complexes deposited by adding an alkali to an aqueous solution to cause hydrolysis, 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 substrates, for example, an inorganic substrate such as glass or an organic substrate such as a polyester film. Can do. In this case, as a method for forming the photocatalyst film, a known method may be adopted and dried, and the thickness of the photocatalyst film may be variously selected, but is usually in the range of 50 nm to 10 μm. The formed photocatalyst film is transparent, provides a good photocatalytic action in the ultraviolet region as in the prior art, and has excellent visible light response.

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

(1) Average particle diameter of fine titanium oxide particles in the dispersion (D ₅₀ )
The average particle diameter (D ₅₀ ) of the titanium oxide fine particles in the dispersion was measured using a particle size distribution measuring device (trade name “Nanotrack particle size analyzer UPA-EX”, Nikkiso Co., Ltd.).

(2) Transparency of the photocatalytic thin film The HAZE value (%) of the glass plate as the substrate is measured. Next, a photocatalyst thin film is produced by applying and drying the dispersion on the glass, and the HAZE value of the glass plate in the state of producing the thin film is measured. From the difference, the HAZE value of the photocatalytic thin film is obtained. The HAZE value was measured using a HAZE meter (trade name “Digital Haze Meter NDH-200”, Nippon Denshoku Industries Co., Ltd.). The transparency of the photocatalytic thin film was evaluated according to the following criteria from the difference in the HAZE value obtained.

Good (displayed as ○) ··· The difference is + 1% or less.
Slightly poor (displayed as △) ··· The difference exceeds + 1% and is less than + 3%.
Defect (displayed as x) ··· The difference exceeds + 3%.

(3) Acetaldehyde gas decomposition performance test of photocatalytic thin film (under visible light irradiation)
The activity of the photocatalyst thin film produced by applying and drying the dispersion was evaluated by the decomposition reaction of acetaldehyde gas. The evaluation was performed by a flow-type gas decomposition performance evaluation method. Specifically, a sample for evaluation in which a photocatalytic thin film is formed on a substrate made of 5 cm square glass is placed in a quartz glass cell having a volume of 12.5 cm ³ , and the concentration is adjusted to 250% in the cell at a concentration of 250 ppm. The acetaldehyde gas was circulated at a flow rate of 5 mL · s ⁻¹ , and light was irradiated with a fluorescent lamp installed at the top of the cell so that the illuminance was 8000 LUX. When the acetaldehyde gas is decomposed by the photocatalyst on the thin film, the concentration of 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).

(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 a slide glass and drying was evaluated by the decomposition reaction of oleic acid.

  Specifically, 0.5% by mass of oleic acid is applied to the surface of the thin film with a dip coater and dried to obtain a sample for photocatalytic activity evaluation. The sample is irradiated with light from a fluorescent lamp at an illuminance of 10,000 LUX. When the oleic acid on the surface of the thin film 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 other hour. The water contact angle was measured using a contact angle meter (trade name “CA-A”, Kyowa Interface Science Co., Ltd.).

[Example 1]
(1) Tin (IV) chloride is added to a 36 mass% titanium chloride (IV) aqueous solution so that the Ti / Sn (molar ratio) is 20, and this is diluted 10 times with pure water, and then the aqueous solution. 10% by mass of ammonia water was gradually added to neutralize and hydrolyze to obtain a precipitate of titanium hydroxide. The pH of the solution at this time was 9. The resulting titanium hydroxide precipitate was deionized by repeatedly adding pure water and decanting. To this titanium hydroxide precipitate after deionization treatment, 30% by mass hydrogen peroxide water was added so that the hydrogen peroxide / titanium hydroxide (molar ratio) was 2.5 or more, and then stirred at room temperature all day and night. It was made to react sufficiently. Thereafter, pure water was added to adjust the concentration, thereby obtaining a yellow transparent tin-containing peroxotitanic acid solution (a) (solid content concentration 1% by mass).

  (2) Copper sulfate was dissolved in pure water to obtain a 1% by mass copper sulfate aqueous solution (b).

  (3) A 500 mL volume autoclave was charged with 400 mL of the tin-containing peroxotitanic acid aqueous solution (a) obtained in (1), and this was hydrothermally treated at a pressure of 1.6 MPa and 200 ° C. for 120 minutes. Thereafter, the reaction mixture in the autoclave was discharged into a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapidly cooling to obtain a titanium oxide fine particle dispersion.

  To the titanium oxide fine particle dispersion obtained in (3), the aqueous copper sulfate solution (b) obtained in (2) was added and mixed so that the metal copper was 0.2% by mass with respect to titanium oxide. A visible light response type titanium oxide fine particle dispersion (A) of the present invention containing 1% by mass of titanium oxide and 1% by mass of peroxotitanium component with respect to titanium oxide was obtained by hydrothermal treatment at 30 ° C. for 30 minutes. It was 12 nm when the average particle diameter of the titanium oxide microparticles | fine-particles in the obtained dispersion liquid was measured.

[Example 2]
(4) Tin (IV) chloride is added to a 36% by mass titanium chloride (IV) aqueous solution so that Ti / Sn (molar ratio) is 5, and this is diluted 10 times with pure water, and then the aqueous solution. 10% by mass of ammonia water was gradually added to neutralize and hydrolyze to obtain a precipitate of titanium hydroxide. The pH of the solution at this time was 9. The resulting titanium hydroxide precipitate was deionized by repeatedly adding pure water and decanting. To this titanium hydroxide precipitate after deionization treatment, 30% by mass hydrogen peroxide water was added so that the hydrogen peroxide / titanium hydroxide (molar ratio) was 2.5 or more, and then stirred at room temperature all day and night. It was made to react sufficiently. Thereafter, 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).

  (5) Copper nitrate was dissolved in pure water to obtain a 1% by mass copper nitrate aqueous solution (d).

  (6) A 500 mL volume autoclave was charged with 400 mL of the tin-containing peroxotitanic acid aqueous solution (c) obtained in (4) and hydrothermally treated at a pressure of 0.5 MPa and 150 ° C. for 120 minutes. Thereafter, the reaction mixture in the autoclave was discharged into a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapidly cooling to obtain a titanium oxide fine particle dispersion.

  Add the copper sulfate aqueous solution (d) obtained in (5) to the titanium oxide fine particle dispersion obtained in (6) so that the metal copper is 0.25% by mass with respect to titanium oxide, and mix. Thus, a visible light responsive titanium oxide fine particle dispersion (B) of the present invention containing 1% by mass of titanium oxide 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.

[Example 3]
(7) After diluting a 36 mass% titanium chloride (IV) aqueous solution 10 times with pure water, 10 mass% ammonia water is gradually added to the aqueous solution to neutralize and hydrolyze the titanium hydroxide. A precipitate was obtained. The pH of the solution at this time was 10. The resulting titanium hydroxide precipitate was deionized by repeatedly adding pure water and decanting. To this titanium hydroxide precipitate after deionization treatment, 30% by mass hydrogen peroxide water was added so that the hydrogen peroxide / titanium hydroxide (molar ratio) was 2.5 or more, and then stirred at room temperature all day and night. It was made to react sufficiently. Thereafter, pure water was added to adjust the concentration to obtain a yellow transparent peroxotitanic acid solution (e) (solid content concentration 1 mass%).

  (8) Tin chloride pentahydrate was dissolved in pure water to obtain a 10% by mass tin chloride aqueous solution (f).

  (9) An autoclave having a volume of 500 mL was charged with 350 mL of the peroxotitanic acid aqueous solution (e) obtained in (7) and 10 mL of the tin chloride aqueous solution (f) obtained in (8). Heat treated. Thereafter, the reaction mixture in the autoclave was discharged into a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapidly cooling to obtain a titanium oxide fine particle dispersion.

  Add the copper sulfate aqueous solution (d) obtained in (5) to the titanium oxide fine particle dispersion obtained in (9) so that the metal copper is 0.3% by mass with respect to titanium oxide, and mix. Thus, a visible light responsive titanium oxide fine particle dispersion (C) of the present invention containing 1% by mass of titanium oxide and 2% by mass of the peroxotitanium component with respect to titanium oxide was obtained. It was 25 nm when the average particle diameter of the titanium oxide microparticles | fine-particles in the obtained dispersion liquid was measured.

[Comparative Example 1]
(10) A titanium oxide fine particle dispersion (D) was obtained in the same manner as in Example 1 except that the aqueous copper sulfate solution was not added. It was 9 nm when the average particle diameter of the titanium oxide microparticles | fine-particles in the obtained dispersion liquid was measured.

[Comparative Example 2]
(11) 400 mL of the peroxotitanic acid aqueous solution (e) obtained in Example 3 was placed in an autoclave having a volume of 500 mL and hydrothermally treated at 150 ° C. for 120 minutes. Thereafter, the reaction mixture in the autoclave was discharged into a container held in a water bath at 25 ° C. via a sampling tube, and the reaction was stopped by rapidly cooling to obtain a titanium oxide fine particle dispersion.

  Add the copper sulfate aqueous solution (d) obtained in (5) to the titanium oxide fine particle dispersion obtained in (11) so that the metal copper is 0.25% by mass with respect to titanium oxide, and mix. Thus, a titanium oxide-based fine particle dispersion (E) was obtained. It was 25 nm when the average particle diameter of the titanium oxide microparticles | fine-particles in the obtained dispersion liquid was measured.

[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 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.

A silica-based binder (colloidal silica, trade name: Snowtex 20 (manufactured by Nissan Chemical Industries, Ltd.)) was added to the dispersions prepared in Examples 1 to 3 and Comparative Examples 1 and 2 with a TiO ₂ / SiO ₂ ratio of 1. After adding in step 5, it was applied to a glass plate with a dip coater and dried to form a photocatalytic thin film having a thickness of 150 nm to obtain a sample for evaluation.

  Table 1 shows the reaction conditions and average particle diameters of the examples and comparative examples, the evaluation of the transparency of the photocatalytic thin film, the results of water contact angle measurement after 5 hours of irradiation with a fluorescent lamp in a self-cleaning performance test, and the fluorescent lamp in an acetaldehyde gas decomposition test. The gas decomposition rate 90 minutes after irradiation is shown collectively.

  As can be seen from the results of Comparative Example 1, sufficient visible light activity cannot be obtained unless a copper component is added.

  As can be seen from the results of Comparative Example 2, sufficient visible light activity cannot be obtained unless a tin component is added.

  As can be seen from the results of Comparative Example 3, if the reaction temperature is too low, the conversion to titanium oxide is very slow.

  As can be seen from the results of Examples 1 to 3, by containing a copper component and a tin component in the dispersion, it is possible to improve the decomposition of acetaldehyde and oleic acid (that is, photocatalytic activity) under irradiation with a fluorescent lamp. I understand.

  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.

Claims (5)

  In the aqueous dispersion medium, fine particles of titanium oxide are dispersed, 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.   2. The visible light responsive titanium oxide fine particle dispersion according to claim 1, wherein the content of the copper component in terms of metallic copper is 0.01 to 5 mass% with respect to titanium oxide.   3. The visible light responsive titanium oxide fine particle dispersion according to claim 1, wherein a content of the tin component is 1 to 1000 in terms of a molar ratio (Ti / Sn) to titanium oxide. The visible light responsive type according to any one of claims 1 to 3, wherein the titanium oxide fine particles have a 50% cumulative distribution diameter (D50) measured by a dynamic scattering method of ₅₀ nm or less. Titanium oxide fine particle dispersion. (1) a step of 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) a titanium oxide fine particle dispersion. The method for producing a visible light responsive titanium oxide fine particle dispersion according to any one of claims 1 to 4, further comprising a step of adding a copper compound to the reaction.