JP2013032474A - Photocatalyst coating liquid, and photocatalyst thin film obtained therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalyst coating liquid good in pot life and coatability, dryable and curable at a relatively low temperature, and capable of forming a hydrophilic thin film high in transparency and long in the duration of the catalytic activity.SOLUTION: The photocatalyst coating liquid contains (A) a photocatalyst particle, and (B) a binder component, wherein the binder component as the (B) component contains a hydrolytically condensed substance obtained by hydrolyzing a hydrolyzable silicon compound in the presence of a basic compound in a mixed solvent of water and a polar organic solvent; the photocatalyst particle as the (A) component is dispersed in the coating liquid; the proportion of the (A) component to the total of the (A) component and the (B) component is 0.05 to 99.5 mass%; and the pH of the coating liquid is in the range of 5 to 8.

Description

  The present invention relates to a photocatalyst coating liquid and a photocatalyst thin film obtained therefrom.

  The photocatalyst coating thin films formed on various substrate surfaces have the ability to clean the substrate surface because the photocatalytic metal compound such as titanium oxide contained therein exhibits the decomposing power and hydrophilicity of organic matter by light irradiation. It is used for applications such as chemical conversion, deodorization, and antibacterial. Currently, such photocatalytic coatings are mainly applied to exterior tiles, glass, exterior wall coating, filters inside air cleaners, inorganic base materials (ceramics, metals, etc.), but organics such as plastic materials. In recent years, applications to materials and designable materials have been actively studied [Japanese Patent Laid-Open No. 2006-116461 (Patent Document 1), Japanese Patent Laid-Open No. 2006-272757 (Patent Document 2)].

  Under such circumstances, most of the photocatalysts that are widely used are in the form of a powder or a sol in which photocatalyst particles having a large particle diameter of 100 nm to several μm are dispersed. Poor sex.

  In addition, in order to apply a photocatalyst particle coating solution to a substrate and cure and fix it, a means of using hydrolyzed silane or silicone resin as a “binder” component is also generally used [Patent No. 2756474 ( Patent Document 3), Patent No. 2865065 (Patent Document 4)]. However, in this case, it is necessary to remarkably reduce the photocatalyst solid content in the coating liquid in order to ensure the transparency of the resulting thin film when actually constructed. As a result, the resulting thin film is significantly inferior in oxidative decomposition characteristics and hydrophilicity as compared to powdered photocatalytic particles, and in many cases, hydrophilic characteristics can be obtained only under conditions exposed to light irradiation and rainfall over a long period of time. Stop.

In many cases, the hydrolyzed silane solution is prepared using an organic solvent instead of an aqueous solvent as a solvent in consideration of the stability of the solution, but the pot life is still not sufficient. The problems related to short life and work safety are still unresolved.
Furthermore, in many cases, baking at several hundred degrees C. is required for fixing the thin film on the base material, and in this case, it is difficult to perform on-site construction in which an appropriate heat source cannot be prepared. Alternatively, a significantly long curing time is required for fixing the thin film to the substrate.

JP 2006-116461 A JP 2006-272757 A Japanese Patent No. 2756474 Japanese Patent No. 2865065

  The present invention has been made in view of the above problems. In particular, the pot life and coatability are good, and it can be dried and cured even at a relatively low temperature, and has high transparency and sustained catalytic activity. It aims at providing the photocatalyst coating liquid which can form a hydrophilic thin film with a long period of time, and this hydrophilic thin film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the photocatalyst particles are dispersed in a solvent, particularly preferably an aqueous mixed solvent containing water or alcohol, and the hydrolyzable silicon compound. A thin film formed by applying a photocatalyst coating liquid containing a specific amount of a hydrolysis-condensation product obtained by hydrolysis in the presence of a basic compound as a binder in a liquid containing water and a polar organic solvent is transparent.・ Excellent hardness, the surface is always hydrophilic, maintains sufficient oxidative degradation ability, and does not depend on the superhydrophilicity of the photocatalyst, and the film itself exhibits water wettability, so it is hydrophilic even in the dark. As a result, the inventors have found that the self-cleaning property does not deteriorate and the present invention has been completed.

That is, the present invention provides the following inventions.
The present invention, first,
(A) a photocatalyst particle, and (B) a photocatalyst coating liquid containing a binder component,
The binder component (B) is a hydrolysis condensate obtained by hydrolyzing (b-1) a hydrolyzable silicon compound in the presence of a basic compound in a mixed solvent of water and a polar organic solvent. Including
The (A) component photocatalyst particles are dispersed in the coating solution,
The ratio of the component (A) to the sum of the components (A) and (B) is 0.05 to 99.5% by mass,
The pH of the coating solution is in the range of 5-8,
The photocatalyst coating liquid characterized by the above is provided.

Examples of the embodiment of the photocatalyst coating liquid include the following.
-The photocatalyst coating liquid whose said hydrolysable silicon compound is alkoxysilane, halogenated silane, or those combination.
The basic compound is of the formula (2a):
^{_{R 1 y -NH 3-y (}} 2a)
(In the formula, R ¹ is a monovalent organic group, and y is an integer of 1 to 3.)
Or
R ¹ ₄ -N ⁺ (2b)
(In the formula, R ¹ is a monovalent organic group.)
The photocatalyst coating liquid which is a compound represented by these, or a nitrogen-containing heterocyclic compound.

-The binder component of (B) component is further (b-2) Formula (3):
R ² —Si (OR ³ ) ₃ (3)
(In the formula, R ² represents a substituted or unsubstituted monovalent hydrocarbon group, and R ³ represents an alkyl group.)
The photocatalyst coating liquid containing the hydrolysis-condensation product of a trifunctional silane compound represented by these.

-The photocatalyst coating liquid in which the binder component of the said (B) component contains further (b-3) water-soluble titanic acid type compound. Furthermore, the said photocatalyst coating liquid whose water-soluble titanic acid type compound of this (b-3) component is peroxotitanic acid.

-The said photocatalyst coating liquid in which the binder component of said (B) component contains further (b-4) water-soluble zirconium type compound. And the water-soluble zirconium compound of the component (b-4) has the following structural formula:
(NH ₄ ) ₂ ZrO (CO ₃ ) ₂
The said photocatalyst coating liquid which is ammonium zirconium carbonate represented by these.

-The photocatalyst coating liquid, wherein the photocatalyst fine particles of the component (A) are metal oxide crystal fine particles having n-type semiconductivity. Then, the metal oxide crystal fine particles having n-type semiconductivity, vanadium, manganese, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, rhodium, palladium, silver, tin, tungsten, platinum, And a photocatalyst coating solution on which a metal selected from the group consisting of gold and a compound of the metal is supported.

  Secondly, the present invention provides a method for producing a hydrophilic photocatalyst thin film in which the photocatalyst coating solution of the above invention is applied onto a substrate, dried and cured.

  Thirdly, the present invention provides a hydrophilic photocatalytic thin film obtained by the production method.

  Fourthly, the present invention provides an article having a hydrophilic surface, which has a base material and the photocatalytic thin film formed on the base material.

  The photocatalyst coating liquid of the present invention is a coating liquid that can use an aqueous solvent as a medium and is safe and free from substrate damage. The coating solution can be cured at a low temperature of about 50 ° C. to 200 ° C., and the resulting thin film is excellent in transparency, hardness, and oxidative decomposition ability against adhered dirt, and the surface maintains hydrophilicity even after one month.

  Since the photocatalytic thin film of the present invention formed using the coating liquid is mainly composed of an inorganic material, the thin film is not deteriorated by the photocatalyst. In addition, the thin film does not depend on the superhydrophilicity by the photocatalyst, and the film itself exhibits water wettability. Therefore, the hydrophilicity continues even in a dark place, and the self-cleaning property does not easily deteriorate with time.

Therefore, the photocatalyst coating liquid of the present invention is excellent in maintaining performance, handleability and design.
Furthermore, when the coating liquid of the present invention contains a hydrolysis condensate of a specific trifunctional siloxane compound, a water-soluble titanium compound, a water-soluble zirconium compound, or a combination of two or more of these, the chemical resistance In particular, strong alkali resistance is improved. In particular, when the hydrolysis condensate (component (b-2)) of the trifunctional siloxane compound is contained, in addition to chemical resistance, adhesion to an organic substrate is also improved.

Hereinafter, the present invention will be described in detail.
-Photocatalyst coating solution-
The photocatalyst coating liquid of the present invention contains (A) photocatalyst particles and (B) a binder component. Hereinafter, both components will be described in detail.

<(A) Photocatalyst particles>
Any conventionally known photocatalyst can be used. The photocatalyst particles may be used alone or in combination of two or more. As the photocatalyst particles, for example, metal oxide crystal fine particles which are n-type semiconductors such as titanium oxide, tungsten oxide, zinc oxide and niobium oxide can be used. For example, anatase-type titanium dioxide (TiO ₂ ), rutile-type titanium dioxide (TiO ₂ ), tungsten trioxide (WO ₃ ), zinc oxide (ZnO), Ga-doped zinc oxide (GZO), niobium oxide in the crystalline state (Nb ₂ O ₅ ) or the like can be used.

  Among them, those having high visible light activity, those doped with nitrogen, sulfur, phosphorus, carbon, etc. in the crystal of these metal oxides, or copper, iron, nickel, gold, silver, platinum, palladium, rhodium, ruthenium on the surface Those carrying carbon or the like can be suitably used. More specifically, rutile-type titanium oxide carrying platinum, rutile-type titanium oxide carrying iron, rutile-type titanium oxide carrying copper, rutile-type titanium oxide carrying copper hydroxide, anatase-type titanium oxide carrying gold And tungsten trioxide carrying platinum. Furthermore, in addition to increasing the transparency of the thin film and good appearance, those having a fine primary particle diameter are preferably used. That is, the primary particle size is preferably in the range of 1 to 100 nm, more preferably in the range of 1 to 50 nm. In the present specification, the “average particle size” means a volume-based average particle size corresponding to 50% of the cumulative distribution obtained by a particle size distribution measuring apparatus using a dynamic light scattering method.

  As a commercial product of such photocatalyst particles, for example, in the state of an aqueous photocatalyst dispersion excellent in transparency and activity, Sagancoat TO-85 (trade name, peroxo modified anatase sol, average dispersed particle size of about 20 nm, manufactured by Sakai Corporation In addition, MPT-623 (trade name, visible light responsive photocatalyst, powder, rutile titanium dioxide carrying platinum; manufactured by Ishihara Sangyo Co., Ltd.) is exemplified as the photocatalyst fine particles having high visible light activity. .

<(B) Binder component>
[(B-1) Hydrolytic condensate of hydrolyzable silicon compound]
The binder component is a hydrolysis condensate obtained by hydrolyzing a hydrolyzable silicon compound in a mixed solvent of water and a polar organic solvent in the presence of a basic compound. As a hydrolysable silicon compound, the silicon alkoxide shown in following Structural formula (1), its condensate, or a mixture thereof is mentioned.
Si (OR) _x (OH) _4-x (1)
(In the formula, R is a monovalent hydrocarbon group, hydrocarbyloxysilyl group, x is an integer of 0 to 4, and when x is 2 or more, a plurality of R may be the same or different.)

  In the above formula. The group represented by R is usually a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, for example, 1 carbon atom such as a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group. -4 alkyl groups; hydrocarbyloxysilyl groups such as alkoxysilyl groups such as triethoxysilyl groups.

  Of these, tetramethoxysilane, tetraethoxysilane, and partial hydrolysates and condensates thereof can be preferably used.

  As a basic compound used for hydrolysis in the above reaction, a nitrogen-containing compound or a nitrogen-containing heterocyclic compound represented by the following general formula (2a) or general formula (2b) is preferable, and these compounds are salts. It may be in the state.

^{_{R 1 y -NH 3-y (}} 2a)
(In the formula, R ¹ is a monovalent organic group, and y is an integer of 1 to 3.)
R ¹ ₄ -N ⁺ (2b)
(In the formula, R ¹ is a monovalent organic group.)

In the above formulas (2a) and (2b), R ¹ is independently a monovalent organic group. R ¹ may be the same as or different from each other. Specific examples of R ¹ include, for example, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, and a C 1 to 3 carbon atom such as a methylol group and an ethylol group. A hydroxyalkyl group is mentioned.

In the case where the nitrogen-containing compound takes the form of quaternary ammonium, the following formula (3):
_{^{R 1 4 N + · X -}} (3)
(Where X ⁻ represents a counter anion)
It may be in a salt state represented by Specifically, examples of X include a hydroxyl anion, a halide anion (F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ ) and the like. Among the quaternary ammonium salts, tetramethylammonium hydroxide can be preferably used.

  Examples of the nitrogen-containing heterocyclic compound include pyridine, pyrazine, pyrrole, imidazole, pyrazole, isoxazole, oxazole, and thiazole. Preferred are pyridine and imidazole.

  The above reaction is performed in a mixed solvent of water and a polar organic solvent. As polar organic solvents, alcohols (for example, methanol, ethanol, isopropanol), glycols (for example, ethylene glycol, propylene glycol), glycerin, butyl cellosolve, methyl cellosolve, ethyl cellosolve, propyl cellosolve, and acetates thereof, ketones (For example, acetone, diacetone alcohol, acetylacetone, methyl ethyl ketone). The polar organic solvents can be used singly or in combination of two or more. Of these, methyl acetate, ethyl acetate, methyl lactate, ethyl lactate, triacetin, and acetone can be suitably used. As for the ratio in a mixed solvent, 5-60 mass% is preferable for water, and 20-50 mass% is more preferable.

  Specifically, the hydrolysis reaction can proceed by mixing and stirring a hydrolyzable silicon compound, a basic compound, a polar organic solvent, and water.

At this time, the concentration of the hydrolyzable silicon compound in the resulting solution is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass. The amount of the basic compound charged is preferably 0.1 to 10 mol times, more preferably 0.5 to 5 mol times the amount of the hydrolyzable silicon compound. The reaction temperature is preferably about 10 to about 70 ° C, more preferably a room temperature of about 20 to 30 ° C. If the temperature is too high, the formation of a gel product is promoted.
Produces a reaction solution containing the hydrolyzed condensate (component (b-1)) thus produced for the entire solution. By removing the solvent from the solution, dissolving the product in water or alcohol, and adjusting the pH to 5 to 8 by acid addition or ion exchange, it can be suitably used as a binder liquid containing the component (b-1).

  The binder component which is the component (B) of the present invention can contain another binder component described below as needed, in addition to the component (b-1).

[(B-2) Hydrolysis condensate of trifunctional silane compound]
The binder component is represented by the formula (3):
R ² —Si (OR ³ ) ₃ (3)
(In the formula, R ² represents a substituted or unsubstituted monovalent hydrocarbon group, and R ³ represents an alkyl group.)
It is a hydrolysis-condensation product of the trifunctional silane compound represented by these.

  The hydrolysis of the trifunctional silane compound may be performed together with the hydrolysis for obtaining the component (b-1) or may be separately hydrolyzed.

  In the coating liquid of the present invention, the ratio of the component (b-1) / (b-2) is preferably in the range of 90/10 to 10/90 in terms of mass ratio.

[(B-3) Water-soluble titanic acid compound]
The binder component is a water-soluble titanic acid compound. As the water-soluble titanic acid compound, peroxotitanic acid is preferable. Peroxotitanic acid is a kind of titanium oxide compound, and is a compound in which a part of Ti—O—Ti bond is converted to Ti—OO—Ti bond as shown in the following structural formula.

  A commercial product can be used as the coating solution containing peroxotitanic acid. Examples of such commercially available coating solutions include Sagan Coat PTA sol (peroxotitanic acid aqueous solution, peroxotitanium solid content concentration 1.70% by mass; manufactured by Sakai Corporation), Tio Sky Coat TAK-B (peroxotitanic acid). Aqueous solution, peroxotitanium solid content concentration of 1.70% by mass; manufactured by Tio-Techno Co., Ltd.).

  In the coating liquid of the present invention, the ratio of the component (b-1) / (b-3) is preferably in the range of 90/10 to 10/90 in terms of mass ratio.

[(B-4) Water-soluble zirconium compound]
The binder component is a water-soluble zirconium compound. Here, the water-soluble zirconium compound includes a zirconium oxide compound. A water-soluble zirconium compound may be used individually by 1 type, or may use 2 or more types together. Examples of the water-soluble zirconium compound include zirconium oxide, zirconium hydroxide, zirconium oxychloride (zirconium oxychloride), zirconium sulfate, zirconium nitrate, zirconium hydrochloride, zirconium acetate, zirconium formate, zirconium carbonate, basic zirconium carbonate, zirconium carbonate. Ammonium, potassium zirconium carbonate, zirconium octylate, zirconium tetranormal propoxide, zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium monobutoxyacetylacetonate bis (ethylacetoacetate), zirconium tetraacetylacetonate, zirconium These hydrolysates or partial hydrolysates such as tributoxy monostearate And the like. A commercial item can be used as a water-soluble zirconium compound.

  In the coating liquid of the present invention, the ratio of the component (b-1) / (b-4) is preferably in the range of 90/10 to 10/90 in terms of mass ratio.

<Medium of coating liquid>
The medium of the coating liquid of the present invention functions as a solvent and / or a dispersion medium for the components (A) to (C). Water is used as the medium. In addition to water, alcohols such as methanol, ethanol, n-propanol and isopropanol, and cellosolves such as methyl cellosolve, ethyl cellosolve, propyl cellosolve and butyl cellosolve can be added, and ethanol, isopropanol and butyl cellosolve are preferred. When such an organic solvent is added to water to obtain an aqueous mixed solvent, the proportion of water in the mixed solvent is preferably 80% by mass or more, and more preferably 90% by mass or more.

<Preparation of photocatalyst coating liquid>
The photocatalyst coating liquid of the present invention was prepared by previously dispersing photocatalyst particles in a solvent to prepare a photocatalyst dispersion, and the photocatalyst dispersion was dissolved in the hydrolyzable condensate (hydrolyzed silicate) of the hydrolyzable silicon compound. It can be prepared by mixing with a solution and stirring.

  In the above, as the solvent for dispersing the photocatalyst particles and the solvent for dissolving the hydrolysis condensate, water is basically used, and a mixed solvent in which the above-described alcohol or cellosolve is blended as necessary can be used. It can also be added as necessary after preparation.

  In the photocatalyst coating liquid of the present invention, the photocatalyst particles (component (A)) are dispersed, and the hydrolysis condensate (component (b-1)) is dissolved or dispersed.

  The photocatalyst concentration in the photocatalyst coating solution of the present invention is usually 0.01 to 10% by mass, preferably 0.1 to 5% by mass, in view of the balance between the antifouling activity and transparency obtained. If the photocatalyst concentration is too low, the antifouling activity of the thin film may be reduced, and if the concentration is too high, the transparency of the thin film may be reduced and the appearance may be impaired.

  Moreover, the ratio of the (A) component photocatalyst and the (B) binder component in the coating liquid is such that the ratio of the (A) component to the total of the (A) component and the (B) component is 0.05 to 99.5. % By mass, preferably 5 to 95% by mass. When the proportion of the component (A) is less than 5% by mass, it is difficult to obtain sufficient hydrophilicity and / or antifouling activity due to oxidative decomposition for the obtained thin film, and when it exceeds 95% by mass, the strength of the obtained thin film is reduced. However, peeling or cracking may occur.

-Photocatalytic thin film-
The photocatalytic thin film of the present invention is a hydrophilic photocatalytic thin film obtained by applying the above photocatalyst coating liquid on a substrate and drying it.

·Base material:
The base material to which the photocatalyst coating solution of the present invention is applied is not particularly limited as long as the target thin film can be formed. Examples of the base material include organic materials and inorganic materials, and inorganic materials include, for example, non-metallic inorganic materials and metallic inorganic materials. These can have various shapes according to their purposes and applications.

  Examples of organic materials include vinyl chloride resin, polyethylene, polypropylene, polycarbonate, acrylic resin polyacetal, fluorine resin, silicone resin, ethylene-vinyl acetate copolymer (EVA), acrylonitrile-butadiene rubber (NBR), polyethylene terephthalate (PET). , Polyethylene naphthalate (PEN), polyvinyl butyral (PVB), ethylene-vinyl alcohol copolymer (EVOH), polyimide, polyphenylene sulfide (PPS), polyether imide (PEI), polyether ether imide (PEEI), polyether Synthetic resin materials such as ether ketone (PEEK), melamine resin, acrylonitrile-butadiene-styrene (ABS) resin; natural, synthetic or semi-synthetic fiber materials and fibers Products, and the like. These may be commercialized into required shapes and configurations such as films, sheets, other molded products, and laminates.

  Examples of non-metallic inorganic materials include glass and ceramic materials. These can be commercialized in various forms such as tiles, glass, mirrors and the like.

  Examples of the metal inorganic material include cast iron, steel material, iron, iron alloy, aluminum, aluminum alloy, nickel, nickel alloy, zinc die cast, etc., and these may be plated or coated with organic paint. It may be. Moreover, the metal plating film provided on the surface of nonmetallic inorganic material or organic material may be sufficient.

  Any conventionally known method can be used to apply the photocatalyst coating liquid to the substrate. Specifically, the dip coating method, spin coating method, spray coating method, mark coating method, impregnation method, roll method, wire bar method, die coating method, gravure printing method, inkjet method, etc. It can be formed on a substrate.

  The thickness of the thin film to be formed is usually in the range of 1 to 500 nm, and preferably in the range of 50 to 300 nm. If the film thickness is too thin, the strength of the thin film may be low, and if it is too thick, the thin film may be cracked.

  In order to apply and apply the photocatalyst coating liquid to dry and cure the coating film, it is preferable to perform the treatment at a temperature range of 50 to 200 ° C. for 1 to 120 minutes, and in particular, at a temperature range of 60 to 90 ° C. It is preferable to process for 60 minutes.

  The thin film of the present invention has high hydrophilicity, and the water contact angle (at 25 ° C., hereinafter the same) on the thin film is preferably 20 degrees or less. When the water contact angle exceeds 20 degrees, the antifouling property may be lowered. The thin film maintains high hydrophilicity not only immediately after formation but also over time. Therefore, the water contact angle on the thin film is preferably 20 degrees or less as well as immediately after the formation, and further preferably 20 degrees or less even after being left in the dark after the formation for one month or more. It is.

  The total light transmittance of the thin film of the present invention is preferably 85% or more and the haze ratio is preferably 3.5% or less. When the total light transmittance of the thin film is less than 85%, the transparency may deteriorate and the appearance may be impaired. When the haze ratio exceeds 3.5%, the transparency may decrease and the appearance may be impaired.

  The present invention also provides an article in which the thin film is formed on a substrate. Such an article may be any article as long as the organic catalyst is expected to decompose organic contaminants, clean the surface, deodorize, antibacterial, hydrophilic, etc. by the photocatalytic thin film of the present invention. For example, tiles (white tiles, color tiles, glowing tiles that generate colors by interference colors), filters (air conditioners, air purifiers, water treatment), insulators, dishes and other daily necessities, sanitary wares such as bathtubs and toilets, exterior tiles Ceramic products such as window glass plates, window glass, mirrors (large to hand mirror size), panels using glass plates (touch panels, display panels, solar cell cover panels), glass products such as lighting fixtures having glass parts; concrete Stone walls such as natural stones such as system walls, mortar, plaster, bricks, marble, etc .; metal products such as steel plates, painted steel plates, galvalume steel plates; window protection films or sheets, heat insulation films or sheets, heat shield films or sheets, panels (touch panels) , Display panels, solar cell cover panels), used in lighting fixtures Transparent synthetic resin products made of krill resin, polycarbonate, polyethylene terephthalate, etc .; made of vinyl chloride resin, melamine resin, polyethylene resin, polypropylene resin, etc. used for wallpaper, cloth, fibers, tents, interior boards, blinds, and other processed products Examples include opaque synthetic resin products.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited by these examples.

[Preparation Example 1] (Preparation of titanium oxide photocatalyst dispersion)
As a photocatalytic material, commercially available MPT-623 (platinum-supported titanium dioxide crystal fine particles / rutile type, primary particle size of about 20 nm; manufactured by Ishihara Sangyo Co., Ltd.) is dispersed in pure water, and the average particle size is 50 nm. An aqueous dispersion was prepared and used as a visible light responsive photocatalyst dispersion having a photocatalyst concentration of 1% by mass.

[Preparation Example 2] (Preparation of binder component and binder liquid)
14.3 g of water, 8.16 g of tetramethylammonium hydroxide (25% by mass aqueous solution, manufactured by Toyo Gosei), 4.67 g of tetraethylorthosilicate (trade name: orthoethyl silicate, manufactured by Tama Chemical Co., Ltd.), acetone (Wako Pure) 20.0 g (manufactured by Yakuhin Kogyo Co., Ltd.) was mixed (tetramethylammonium hydroxide: tetraethylorthosilicate in a molar ratio of 4: 1) and stirred at room temperature for 5 hours. After removing the solvent from the resulting reaction solution to separate the product hydrolysis condensate (binder component), the product was dissolved again in water, and the aqueous solution was converted to an ion exchange resin (trade name: Dowex). 50W-X8, manufactured by Dow Corning) was adjusted to pH 7.0 through a column packed, and water was further added to adjust the final solid content concentration to 1.0 mass%. The resulting aqueous binder solution is hereinafter referred to as “binder liquid 1”.

[Examples 1 to 3]
After adding and dissolving the binder liquid 1 prepared in Preparation Example 2 to the photocatalyst dispersion liquid prepared in Preparation Example 1, water is added in each Example so that each component has a mass concentration shown in Table 1 and applied. A liquid was prepared.

[Comparative Example 1]
Instead of the binder liquid 1, coating was performed in the same manner as in Example 1 except that a commercially available Snowtex S (colloidal silica having a particle size of 8 to 11 nm; manufactured by Nissan Chemical Industries, Ltd.), which is a solid silica sol binder, was used. A working solution was prepared. The concentration of each component was as shown in Table 1.

[Comparative Example 2]
A coating solution was prepared in the same manner as in Example 1, except that a commercially available Sagan Coat PTA sol (aqueous solution of peroxotitanic acid; manufactured by Sakai Corporation) was used instead of the binder solution 1. did. The concentration of each component was as shown in Table 1.

[Comparative Example 3]
Coating was performed in the same manner as in Example 1 except that a commercially available SS-C1 (water-alcohol solution of hydrolyzed siloxane: manufactured by Colcoat Co., Ltd.), which is a water-alcohol binder, was used in place of the binder liquid 1. A liquid was prepared. The concentration of each component was as shown in Table 1.

[Preparation Example 3] (Preparation of binder component and binder solution)
14.3 g of water, 8.16 g of tetramethylammonium hydroxide (25% by weight aqueous solution, manufactured by Toyo Gosei), 4.67 g of tetraethylorthosilicate (manufactured by Tama Chemical), γ-methacryloxypropyltrimethoxysilane (product name KBM-503) (Made by Shin-Etsu Chemical Co., Ltd.) 5.20 g, acetone (made by Wako Pure Chemical Industries, special grade) 20.0 g (At this time, the molar ratio of tetramethylammonium hydroxide: tetraethylorthosilicate: γ-methacryloxypropyltrimethoxysilane was 4: 1: 1) was mixed and stirred at room temperature for 5 hours. A solvent is removed from the obtained reaction solution to obtain a hydrolysis condensation product (binder component) as a product, and an aqueous solution obtained by dissolving this product in water again is used as an ion exchange resin (Dowex 50W-X8, The pH was adjusted to 7.0 by passing through a column packed with Dow Corning), and water was added to adjust the final solid content concentration to 1.0 mass%. The binder liquid thus obtained is referred to as “binder liquid 2”.

[Preparation Example 4] (Preparation of binder component and binder solution)
Instead of γ-methacryloxypropyltrimethoxysilane, 5.0 g of glycidoxypropyltrimethoxysilane (product name KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) is used, and tetramethylammonium hydroxide: tetraethylorthosilicate: gly A binder component was obtained under the same conditions as in Preparation Example 3, except that the mixture was mixed so that the molar ratio of cidoxypropyltrimethoxysilane was 4: 1: 1. This binder liquid is referred to as “binder liquid 3”.

[Example 4]
In Example 4, the binder solution 2 prepared in Preparation Example 3 was added to the photocatalyst dispersion prepared in Preparation Example 1 and dissolved, and then water was added so that each component had a mass concentration shown in Table 2. A working solution was prepared.

[Example 5]
In Example 5, the binder solution 3 prepared in Preparation Example 4 was added to the photocatalyst dispersion prepared in Preparation Example 1 and dissolved, and then water was added so that each component had a mass concentration shown in Table 2. A working solution was prepared.

[Comparative Example 4]
A coating liquid was prepared in the same manner as in Example 4 except that a commercially available FJ-294 (manufactured by Grandex Co., Ltd.), which is a water glass binder, was used instead of the binder liquid 2. The concentration of each component was as shown in Table 2.

[Preparation Example 5] (Preparation of binder solution)
The binder liquid 1 prepared in Preparation Example 2 and a commercially available aqueous solution of peroxotitanic acid (product name: Sagancoat PTA-85; manufactured by Sakai Corporation) have a peroxotitanic acid concentration of 0.05 mass in the resulting mixture. It mixed so that it might become%. The resulting mixed liquid is referred to as “binder liquid 4”.

[Preparation Example 6] (Preparation of binder solution)
The binder liquid 1 prepared in Preparation Example 2 and a commercially available aqueous solution of peroxotitanic acid (product name: Sagancoat PTA-85; manufactured by Sakai Corporation) have a peroxotitanic acid concentration of 0.15 mass. It mixed so that it might become%. The resulting mixed liquid is referred to as “binder liquid 5”.

[Example 6]
After mixing the binder solution 4 prepared in Preparation Example 5 with the photocatalyst dispersion prepared in Preparation Example 1, water was added to prepare a coating solution so that each component had a mass concentration shown in Table 3.

[Example 7]
After mixing the binder solution 5 prepared in Preparation Example 6 with the photocatalyst dispersion prepared in Preparation Example 1, water was added to prepare a coating solution so that each component had a mass concentration shown in Table 3.

[Preparation Example 7] (Preparation of binder solution)
The concentration of ammonium zirconium carbonate in the resulting mixed solution of the binder liquid 1 prepared in Preparation Example 2 and a commercially available aqueous solution of ammonium zirconium carbonate (product name: AC-7; manufactured by Daiichi Rare Element Chemical) is 0.05 mass. It mixed so that it might become%. The obtained mixed liquid is referred to as “binder liquid 6”.

[Preparation Example 8] (Preparation of binder solution)
The binder liquid 1 prepared in Preparation Example 2 and a commercially available aqueous solution of ammonium zirconium carbonate (product name: AC-7; manufactured by Daiichi Rare Element Chemical Co., Ltd.) had a concentration of 0.15 mass of zirconium ammonium carbonate in the resulting mixture. It mixed so that it might become%. The obtained binder liquid is referred to as “binder liquid 7”.

[Example 8]
After mixing the binder solution 6 prepared in Preparation Example 7 with the photocatalyst dispersion prepared in Preparation Example 1, water was added to prepare a coating solution so that each component had a mass concentration shown in Table 4.

[Example 9]
After mixing the binder liquid 7 prepared in Preparation Example 8 with the photocatalyst dispersion liquid prepared in Preparation Example 1, water was added to prepare a coating solution so that each component had a mass concentration shown in Table 4.

-Sample preparation-
A PET (polyethylene terephthalate) film (thickness 50 μm) cut to A4 size was used as the base material, and the surface thereof was subjected to corona discharge treatment. A photocatalytic thin film was formed by heating and drying for minutes to a thickness of about 200 nm.

-Physical property evaluation of photocatalytic thin film-
Various physical properties of the sample photocatalytic thin film were measured and evaluated as follows.
・ Surface tension (static / dynamic)
..Water contact angle:
It measured using contact angle meter CA-A (Kyowa Interface Science Co., Ltd. product).

..Contact angle after leaving in the dark for 1 month:
The sample film was irradiated with UV of 365 nm at 1 mw / cm ² for 24 hours, and then the film was put in an airtight container, shielded from light, taken out after one month, and measured with a contact angle meter CA-A.

..Dynamic wet tension on the surface:
Mixture No. for wet tension test 22.6-No. 73.0 (manufactured by Wako Pure Chemical Industries, Ltd.) was applied to the thin film surface of the sample with a cotton swab, and the wet tension of the liquid mixture for wet tension test when the applied liquid film was held without being repelled for 10 seconds Was the wetting tension (mN / m).

-Pencil hardness The hardness of the thin film of the sample was measured using a scratch hardness (pencil method) tester (manufactured by Cortec Co., Ltd.) in accordance with JIS K5600-5-4.
・ Appearance (turbidity, presence or absence of coloring)
During the preparation of the sample, the photocatalyst dispersion was partially applied to the surface of the base film, so that a portion where the photocatalyst thin film was formed and a portion where it was not formed were formed. The thin film formation part was visually observed with the thin film non-formation part, and it was investigated whether clear turbidity and coloring were recognized by the thin film.

-Film thickness measurement of thin film It measured using the thin film measuring apparatus F-20 (made by FILMETRICS) and the scanning electron microscope S-3400NX (made by Hitachi High-Technologies Corporation).
-Average particle diameter of the photocatalyst fine particles in the coating solution It was measured using Microtrac UPA-EX (Nikkiso Co., Ltd.).

Photocatalytic activity The sample film was placed in a 5 L closed chamber with three black lights inside. The chamber was filled with 50% humidity air (the ratio of nitrogen and oxygen was 4: 1), and acetaldehyde gas was sealed in the chamber so that the concentration became 20 ppm.
After standing in this state for about 1 hour, the black light was turned on, and the decreasing behavior of acetaldehyde gas was traced under the condition that the amount of light on the sample surface was 1.0 mW / cm ² . For the measurement of the acetaldehyde gas concentration, a photoacoustic multigas monitor (manufactured by INNOVA; Model 1412) was used, and the time until the concentration reached 0.01 ppm was determined as photocatalytic activity.

-Alkali resistance A 1 mol / L aqueous solution of sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) was prepared, and a thin film of the sample was immersed in this, and after 24 hours, it was wiped off with Kimwipe to check for scratches. Those with scratches were evaluated as bad and indicated with “x”, and those without scratches were evaluated as good and indicated with “◯”.

-Adhesion to organic substrate A cross-cut cross-cut tape peeling test was performed on the thin film according to JIS K5400. The number of squares remaining without peeling in 100 squares produced by cross-cutting is shown.
-Comprehensive evaluation The thing which is 3H or more in hardness, there is no change of an external appearance, and has a photocatalytic activity within 12 hours by the photocatalytic activity test was evaluated as favorable, and was shown by "(circle)".

  The result of said measurement and evaluation is shown to Tables 1-4. Note that the thickness of each of the formed thin films was 200 nm.

  For ease of comparison, Comparative Examples 2 and 3 are shown again in Table 2, and the results of adhesion to an organic substrate and alkali resistance are also shown.

  In Table 3, Comparative Examples 1 and 3 are shown again for the same purpose. Table 4 shows Comparative Examples 2 to 4 again.

  From the results in Table 1, the thin films obtained from the coating liquids of Examples 1 to 3 had the best thin film characteristics. Comparing Example 1 and Comparative Examples 1 to 3 where the photocatalyst: binder component is in the same ratio, the thin film of Example 1 is excellent in film physical properties such as appearance and hardness, and its oxidative decomposition activity is also kept very high. . From Comparative Example 1, the film formed only from colloidal silica is not cured due to insufficient temperature, the thin film formed only from peroxotitanic acid is colored, and the film formed from SS-C1 is excellent in strength. However, the oxidative decomposition ability, which is a characteristic of the photocatalyst, was significantly reduced.

  From the results in Table 2, the thin film obtained from the coating solutions of Examples 4 and 5 had the best thin film characteristics. Although the photocatalyst: binder component ratio is the same, when comparing Examples 4 and 5 with Comparative Example 2-4, the thin film of Example 4 is excellent in film physical properties such as appearance / hardness, adhesion, and alkali resistance, Moreover, the oxidative degradation activity is also kept very high. From Comparative Example 4, the film formed only with FJ-294 was slightly cloudy in the neutral region, and was inferior in alkali resistance, organic substance adhesion, and photocatalytic properties. The thin film formed with only peroxotitanic acid is colored, and the film formed with SS-C1 has excellent film-forming properties, but it does not adhere to organic matter and the oxidative decomposition ability, which is a feature of the photocatalyst, is significantly reduced. It was.

  From the results of Table 3, the thin films obtained from the coating solutions of Examples 6 and 7 had the best thin film characteristics. Although the photocatalyst: binder component ratio is the same, when comparing the Example with Comparative Examples 1, 3, and 4, the thin films of Examples 6 and 7 have excellent film physical properties such as appearance, hardness, adhesion, and alkali resistance. Moreover, the oxidative degradation activity is also kept very high. From Comparative Example 4, the film formed only with FJ-294 was slightly cloudy in the neutral region, and was inferior in alkali resistance and photocatalytic properties. The thin film formed only with Snowtex was insufficiently cured under these conditions, and the film formed with SS-C1 was excellent in film forming property, but the oxidative decomposition ability, which is a characteristic of the photocatalyst, was remarkably lowered.

  From the results in Table 4, the thin films obtained from the coating solutions of Examples 8 and 9 had the best thin film characteristics. Although the photocatalyst: binder component ratio is the same, comparing the Examples and Comparative Examples 2 to 4, the thin films of Examples 8 and 9 are excellent in film physical properties such as appearance, hardness, and alkali resistance, and have an oxidative decomposition activity. Also kept very high. From Comparative Example 4, the film formed only with FJ-294 was slightly cloudy in the neutral region, and was inferior in alkali resistance and photocatalytic properties. The thin film formed only with PTA was colored, and the film formed with SS-C1 was excellent in film forming property, but the oxidative decomposition ability, which is a characteristic of the photocatalyst, was remarkably reduced.

  Since the photocatalytic thin film of the present invention exhibits the decomposing power and hydrophilicity of organic substances by irradiation with light, it is utilized for applications such as cleaning of the substrate surface, deodorization, antibacterial, etc., for example, exterior tile, glass, exterior wall coating It is used for filters inside air purifiers, inorganic base materials such as ceramics and metals, and organic materials such as plastic materials. The photocatalyst coating liquid of the present invention is useful for forming the photocatalyst thin film.

Claims (15)

(A) a photocatalyst particle, and (B) a photocatalyst coating liquid containing a binder component,
The binder component (B) is a hydrolysis condensate obtained by hydrolyzing (b-1) a hydrolyzable silicon compound in the presence of a basic compound in a mixed solvent of water and a polar organic solvent. Including
The (A) component photocatalyst particles are dispersed in the coating solution,
The ratio of the component (A) to the sum of the components (A) and (B) is 0.05 to 99.5% by mass,
The pH of the coating solution is in the range of 5-8,
Photocatalyst coating solution.   The photocatalyst coating liquid according to claim 1, wherein the hydrolyzable silicon compound is an alkoxysilane, a halogenated silane, or a combination thereof. The basic compound is represented by the formula (2a):
^{_{R 1 y -NH 3-y (}} 2a)
(In the formula, R ¹ is a monovalent organic group, and y is an integer of 1 to 3.)
Or
R ¹ ₄ -N ⁺ (2b)
(In the formula, R ¹ is a monovalent organic group.)
The photocatalyst coating solution according to claim 1, wherein the photocatalyst coating solution is a compound represented by the formula: The binder component of the component (B) is further added to the formula (3) (b-2):
R ² —Si (OR ³ ) ₃ (3)
(In the formula, R ² represents a substituted or unsubstituted monovalent hydrocarbon group, and R ³ represents an alkyl group.)
The photocatalyst coating liquid which concerns on any one of Claims 1-3 containing the hydrolysis-condensation product of a trifunctional silane compound represented by these.   (B) The photocatalyst coating liquid which concerns on any one of Claims 1-4 in which the binder component of a component contains (b-3) water-soluble titanic acid type compound further.   The photocatalyst coating liquid according to claim 5, wherein the water-soluble titanic acid compound as the component (b-3) is peroxotitanic acid.   (B) The photocatalyst coating liquid which concerns on any one of Claims 1-6 in which the binder component of a component contains the water-soluble zirconium type compound further (b-4). The water-soluble zirconium compound as the component (b-4) has the following structural formula:
(NH ₄ ) ₂ ZrO (CO ₃ ) ₂
The photocatalyst coating liquid which concerns on ammonium carbonate represented by these.   The photocatalyst coating liquid according to any one of claims 1 to 8, wherein the photocatalyst fine particles of component (A) are crystal fine particles of a metal oxide having n-type semiconductivity.   The above-mentioned metal oxide crystal fine particles having n-type semiconductivity include vanadium, manganese, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, rhodium, palladium, silver, tin, tungsten, platinum, and gold. The photocatalyst coating liquid which concerns on the metal selected from the group which consists of and / or the compound of this metal is carry | supported.   The photocatalyst coating liquid which concerns on any one of Claims 1-10 containing water as a medium.   The manufacturing method of the hydrophilic photocatalyst thin film which apply | coats the photocatalyst coating liquid of any one of Claims 1-11 on a base material, and is dried and hardened.   A hydrophilic photocatalytic thin film obtained by the production method according to claim 12.   The hydrophilic photocatalytic thin film according to claim 13, wherein the initial contact angle of water immediately after formation is 20 degrees or less, and the contact angle is 20 degrees or less even after standing in a clean dark place for 1 month or more.   An article provided with a hydrophilic surface, comprising a substrate and the photocatalytic thin film according to claim 13 or 14 formed on the substrate.