WO2003068871A1 - Compositions for forming photocatalytic film and substrate provided with photocatalytic film - Google Patents

Abstract

It is intended to provide compositions for forming a photocatalytic film whereby an excellent hydrophilic nature can be imparted to the surface of a substrate, in particular, compositions for forming a photocatalytic film whereby a photocatalytic film having an excellent effect of decomposing stains and a highly hydrophilic durability can be formed. It is also intended to provide a substrate provided with a photocatalytic film having an excellent hydrophilic nature. These compositions for forming a photocatalytic film comprise as the essential components a photocatalyst (titanium oxide, etc.), a specific silica precursor (a silicic acid compound containing from 0.001 to 1 part by mass of an alkali metal ion per 100 parts by mass of silicic acid, for example, sodium silicate wherein the sodium ion content has been lowered with the use of an ionic exchange resin) and a vehicle.

Description

 Description Composition for forming photocatalytic film and substrate with photocatalytic film

 The present invention relates to a photocatalyst film-forming composition capable of forming a photocatalyst film on the surface of various substrates, a photocatalyst film formed from the composition, and a substrate with a photocatalyst film having the photocatalyst film. Background art

 It is known that photoexcitation of a photocatalyst decomposes organic dirt attached to the photocatalyst surface, resulting in a hydrophilic surface. As a method for forming a photocatalytic film, a pyrolysis method, which is a kind of a dry method, has been conventionally known (for example, Japanese Patent Application Laid-Open No. H11-5122337). However, the above method has a problem in that it is inferior to the wet method in the hydrophilicity persistence.

 A method of forming a photocatalyst film using a coating composition containing a photocatalyst and silica is also known (for example, Japanese Patent No. 2756474). However, the film using the above-described method using the silicon force has problems that the hydrophilicity is inferior and the soil decomposability is low. The present invention has been made to solve the above problems, and provides a composition for forming a photocatalyst film capable of imparting excellent hydrophilicity to the surface of a substrate, and in particular, forming a photocatalyst film having excellent soil decomposability. An object is to provide a photocatalyst film formed and a substrate with the photocatalyst film. Further, the present invention provides a photocatalyst film-forming composition capable of forming a photocatalyst film having a long hydrophilicity duration and excellent abrasion resistance on the surface, a photocatalyst film formed from the composition, and a substrate with the photocatalyst film. Aim. Disclosure of the invention

 The present invention provides a composition for forming a photocatalytic film, which essentially includes photocatalytic semiconductor fine particles, the following silica precursor and a medium.

Silica precursor: a silicate compound containing 0.001-1 to 1 part by mass of an alkali metal ion with respect to 100 parts by mass of a silicate. . Further, the present invention provides a photocatalyst film formed on a surface of a substrate from a composition for forming a photocatalyst film, and a substrate with a photocatalyst film having the photocatalyst film. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a schematic cross-sectional view showing an example of a substrate with a photocatalytic film of the present invention.

 Explanation of reference numerals

 10: substrate with photocatalytic film

 20: Base material

 30: Photocatalyst film Embodiment for carrying out the invention

 The photocatalytic semiconductor fine particles according to the present invention are such that when irradiated with light having an energy larger than the energy difference between the valence band and the conduction electron band of the photocatalyst, the conduction electrons and the positive electrons are excited by the excitation of the electrons in the valence band. A material having the property of generating pores. Preferred examples of such photocatalytic semiconductor fine particles include anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, tungsten trioxide, ferric oxide, and strontium titanate.

 The average particle diameter of the photocatalytic semiconductor fine particles in the present invention is obtained by measuring the agglomerated particle size of the fine particles in the composition using light scattering using a Microtrac UPA particle size distribution meter (manufactured by HONE YWE LL), It is preferably from 5 to 90 nm, particularly preferably from 40 to 70 nm. If the average particle size is too small, various effects of the photocatalyst are hardly exhibited because the photocatalyst fine particles are buried in the formed photocatalytic film. If the average particle diameter is too large, the mechanical strength of the formed photocatalyst film may be insufficient, and transparency may not be ensured.

The silica precursor in the present invention is a silicic acid compound containing 0.001 to 1 part by mass of an alkali metal ion with respect to 100 parts by mass of a citric acid. It is preferably contained in an amount of from 0.2 to 0.2 parts by mass, and particularly preferably from 0.01 to 0.15 parts by mass. The alkali metal ion concentration was measured by ICP emission spectrometry using, for example, SPS400 manufactured by Seiko Instruments Inc. There is no particular limitation on the alkali metal ion, and one type may be used or two or more types may be used. alkali a As the metal ion, a sodium ion or a lithium ion is preferable. The silicate compound means a compound that forms a silica film by performing a post-treatment as described below.

 The silylation precursor is preferably a product obtained by removing a portion of the metal ion from the alkali metal salt of caieic acid. The product can be obtained, for example, by a method of reducing the alkali metal ion from the alkali metal salt of keic acid using a cation exchange resin. By controlling the amount of cation exchange resin used, contact time, contact method, etc., the amount of metal ions to be reduced can be adjusted.

The cation exchange resin, a strongly acidic cation exchange resin (RS0 ₃ H type), although weakly acidic cation exchange resin (RCOOH type), and the like can be used, the use of strongly acidic cation exchange resin is a reaction rate It is preferred in that respect.

 In the composition for forming a photocatalyst film of the present invention, the concentration of metal ions is preferably 1 to 80 ppm in terms of mass relative to the composition for forming a photocatalyst, and particularly preferably 1 to 40 ppm. More preferably, it is 1 to 20 ppm. If the concentration of the alkali metal ion is too low, the stability and hydrophilicity of the composition decrease, and if it is too high, the stability of the composition remarkably decreases.

 Examples of the alkali metal salt of the caiic acid include one or more selected from the group of sodium silicate, lithium silicate, potassium silicate, and the like, with sodium silicate and Z or lithium gayate being particularly preferred.

The sodium gay acid, S i O ₂ ZN a ₂ 〇 composition ratio are known different materials can be used without particular limitation. Among them, a material having a small content ratio of Na ₂ O is preferable. Examples of commercially available sodium silicate include sodium silicate 1 (molar ratio of Si ₂ / Na ₂₀ : 2.0 to 2.3) (sodium silicate 1 is a trade name of Nippon Chemical Industry Co., Ltd.) Hereinafter, the same applies to Nos. 2 to 4.), Sodium gayate No. 2 (equivalent molar ratio: 2.4 to 2.7), Sodium silicate No. 3 (equivalent molar ratio: 3.0 to 3. 3) and Sodium Gayate No. 4 (equivalent molar ratio: 3.7-3.9). In particular, sodium silicate 3 or 4 having a small content ratio of Na ₂ 〇 is particularly preferable.

As the lithium Kei acid, Ri Contact known S I_〇 ₂ i ₂ O composition ratios of different materials, it can be used without particular limitation. Among them, a material having a small Li ₂ O content ratio is preferable. Commercially available lithium silicates include lithium gayate 35 (S i 0 ₂ ZL i ₂モ ル molar ratio: 3.5) (Lithium silicate 35 is a trade name of Nippon Chemical Industry Co., Ltd., and the same applies to 45 and 75 hereinafter.), lithium silicate 45 ( Equimolar ratio: 4.5) and lithium silicate 75 (equimolar ratio: 7.5). In particular, L i ₂ 0 containing ratio smaller again Kei lithium 7 5 are particularly preferred.

The composition for forming a photocatalyst film of the present invention preferably contains a surfactant. The surfactant has two main functions, the first is to ensure the wettability of the composition to the substrate, and the second is to make the photocatalytic film formed using the composition hydrophilic. It is to make sex higher. The type of surfactant is not particularly limited, but a nonionic surfactant is preferably used from the viewpoint of liquid dispersion stability. In particular, a compound in which the hydrophilic part is a polyoxyalkylene and the hydrophobic part is a fluorinated organic group [eg, C ₈ F _{x 7} CH ₂ CH ₂ CH (CH ₃ ) O (CH ₂ CH ₂ 〇) _x (CH ₂ CH (CH ₃ ) O) _y H [x: y = 70: 30; x + y = 5.72; average molecular weight 800]] (hereinafter referred to as surfactant Q). ) etc. ] Is preferred. Alternatively, a compound in which the hydrophilic part is polyoxyalkylene and the hydrophobic part is methylpolysiloxane (for example, product name: "L-177" manufactured by Nippon Tunicer Co., Ltd.) is preferable.

 In the composition for forming a photocatalyst film of the present invention, the silica precursor is preferably contained in an amount of 25 to 900 parts by mass, more preferably 50 to 400 parts by mass, based on 100 parts by mass of the photocatalytic semiconductor fine particles. Preferably, it is included. In the case where a surfactant is contained, the surfactant is preferably contained in an amount of 0.1 to 10 parts by mass with respect to 100 parts by mass of the photocatalytic semiconductor fine particles. The durability of the hydrophilicity of the obtained photocatalyst film is reduced, and if it is too small, the obtained photocatalyst film is not provided with hydrophilicity. Also, if the proportion of the surfactant is too large, the appearance of the obtained photocatalyst film is impaired, and the durability of the hydrophilicity is reduced. I do.

The composition for forming a photocatalyst film of the present invention contains a medium. The medium is not particularly limited, is preferably a medium containing water, and may contain a solvent. The solvent is used mainly for dilution, and the composition is preferably in the form of a solution. The solvent is preferably a polar solvent such as a lower alcohol, a nitrogen-containing solvent, and a zeolite-containing solvent, and particularly preferably a lower alcohol. Two or more solvents may be used. Water is particularly preferred as the medium. The total of the photocatalytic semiconductor fine particles and the silica precursor in the photocatalytic film forming composition of the present invention. The amount may be determined according to the method of application and the desired thickness of the photocatalytic film. The total amount is preferably 0.5 to 50 parts by mass, more preferably 0. 0 to 50 parts by mass, per 100 parts by mass of the photocatalyst-forming composition, in consideration of the stability, economy and the like of the composition. The amount is preferably from 5 to 15 parts by mass, particularly preferably from 0.5 to 5 parts by mass.

 The composition for forming a photocatalyst film of the present invention may contain a functional additive. Examples of the functional additive include coloring dyes, pigments, ultraviolet absorbers, antioxidants, and fine particles of oxide particles other than the photocatalytic semiconductor particles of the present invention (phosphorus pentoxide, magnesium oxide, etc., average particle diameter. Is preferably 20 O nm or less.) Are preferable.

 Using the composition for forming a photocatalyst film of the present invention, the composition is applied to the surface of a substrate, a photocatalytic film is formed, and a substrate with a photocatalytic film is produced. In the photocatalytic film, the silica precursor has been converted to silica, but a silanol group may remain partially.

The silica precursor has a silanol group in the compound, that is, has a structure represented by S i O _s (OH) _t (where s and t are integers of 0 or more and s + t = 4.) ( However, in the structure, an oxygen atom which is not a 7K acid group is chemically bonded to another silicon atom.) It is considered that a silicic acid is formed from the silicic acid precursor by a dehydration condensation reaction.

 In the present invention, a composition for forming a photocatalyst film is applied to the surface of a substrate using a known wet method, and as shown in FIG. 1, a photocatalyst film having a photocatalyst film 30 formed on a substrate 20 is provided. A substrate 10 can be formed. Preferred examples of the wet method include spray coating, brush coating, hand coating, spin coating, dip coating, coating by various printing methods, curtain flow, die coating, and flow coating.

 After applying the composition for forming a photocatalytic film, it is preferable to perform a post-treatment for the purpose of removing the medium and increasing the hardness of the photocatalytic film. Examples of the post-treatment include drying and heating at room temperature, irradiation with electromagnetic waves such as ultraviolet rays and electron beams, and heating. The heating is preferably carried out at a temperature of 50 to 700 ° (in particular, at a temperature of 100 to 350 ° C for 5 to 60 minutes in consideration of the heat resistance of the base material. In the case of a material having low heat resistance such as resin. In the case where the low molecular weight compound in the base material is diffused out of the base material by heating, as the post-treatment, irradiation of electromagnetic waves such as ultraviolet rays and electron beams is performed. It is preferred to do so.

In the present invention, the thickness of the obtained photocatalyst film can be controlled by adjusting the concentration of the composition for forming a photocatalyst film, the type of solvent, the application conditions, the post-treatment conditions, and the like. If the photocatalytic film is too thick, the film may crack, create interference fringes, or be scratched. There is a disadvantage that the scratch is conspicuous, and if it is too thin, the desired photocatalytic performance may not be exhibited. The thickness of the photocatalyst film is preferably from 10 to 30 nm, more preferably from 10 to 150 nm, in view of economy.

 The substrate used in the present invention is not particularly limited. The shape of the substrate is not limited to a flat plate, and may have a curvature over the entire surface or a part thereof. The substrate used in the present invention is preferably a transparent substrate such as a glass or an organic resin. Examples of the glass include soda lime glass mainly used for plate glass and automotive glass, and examples of the organic resin include resins such as polyacrylonitrile, acrylic, polyethylene, polypropylene, and polyethylene terephthalate. Is mentioned. Further, in order to increase the strength of the organic resin, a silicone hard coat may be applied to the surface of the resin. When a transparent substrate such as glass or organic resin is used as the substrate, the visible light transmittance (JISR 3106 (19 98 years)) is preferably 70% or more.

 The substrate may be pretreated. Examples of the pretreatment include a plasma treatment, a corona discharge, a UV treatment, a discharge treatment such as an ozone treatment, a chemical treatment using an acid or an alkali, a physical treatment using an abrasive, and the like. By performing the pretreatment, the wettability of the composition to the substrate is improved, the composition can be applied uniformly, and the adhesion of the formed photocatalytic film to the substrate can be increased. In particular, when the substrate is an organic resin, it is preferable to perform a pretreatment. In general, pretreatment performed by ultraviolet irradiation using a low-pressure mercury lamp or the like used for modifying plastics is particularly effective.

In addition, since these pretreatments and posttreatments as described above greatly affect the performance of the obtained film, it is necessary to optimize each treatment condition. For example, by post-treatment by irradiation with ultraviolet rays, the dehydration-condensation polymerization reaction can be advanced to promote the curing of the film, and the adhesion between the substrate surface and the composition can be improved. If the post-treatment can improve the adhesion to the substrate as described above, the pre-treatment is not essential. In some cases, pretreatment more than necessary may deteriorate the base material and lead to a decrease in performance. The substrate with a photocatalyst film of the present invention is preferably used as an article for transportation equipment, an article for construction, and the like because its surface is excellent in hydrophilicity and excellent in transparency. Examples of articles for transportation equipment include bodies of trains, automobiles, ships, and aircraft, window glasses, mirrors, cover plates for various display elements, and the like. Building materials include exterior walls, sealants, window glass, Structures such as bridges and tunnels are exemplified. Other uses include a cover glass for lighting, a sound insulating wall, and the like.

 The substrate with a photocatalytic film of the present invention has an antifogging property such that water droplets adhering to the surface spread because the surface is excellent in hydrophilicity and the surface is not clouded. In addition, organic soil is decomposed on the surface. In addition, irradiation of the surface with light further improves the decomposition performance of organic soil. Furthermore, when raindrops run down the surface due to rainfall, dirt also flows down at the same time (self-cleaning effect). The substrate with a photocatalytic film of the present invention can also be expected to have effects such as securing visibility, protecting aesthetics, and reducing maintenance costs.

The photocatalyst film formed from the composition for forming a photocatalyst film of the present invention is obtained by hydrolyzing S i (OR) ₄ (R: alkyl group), which is a conventional alkoxysilane, to obtain S i O _P (OH). _Q (OR) _r (p, Q is an integer of 0 or more, r is an integer of 1 or more, p + q + r = 4.) (However, in the structure, oxygen which is not a hydroxyl group The atom is chemically bonded to another silicon atom.) It has better hydrophilicity retention and soil decomposability than a film formed from a composition using a product having the following formula:

 In the substrate with a photocatalyst film of the present invention, another film may be provided between the substrate and the photocatalyst film. Examples of the another film include, for example, an alkali barrier layer (when the substrate is an alkali metal-containing glass, a layer for preventing diffusion of the alkali metal into the photocatalyst film).

 Example

 The present invention will be specifically described with reference to Examples (Examples 1 to 7 and 10 to 12) and Comparative Examples (Examples 8 and 9). The samples were evaluated using the following method. Table 1 shows the evaluation results.

 [Hydrophilic]

 Immediately after the sample was made, the contact angle of water, which was not irradiated with light, was measured.

 [Hydrophilic persistence]

 Immediately after the sample was prepared, the sample was kept in an environment without light for one week, and the contact angle of water was measured. The contact angle is preferably 20 ° or less, more preferably 10 ° or less, from the viewpoint of maintaining hydrophilicity.

 [Stain degradation]

Oleic acid is applied to the sample immediately after preparation to form a dirty surface with a water contact angle of about 70 °, and a black light (center wavelength: 365 nm) of 0.5 mWZc is applied to the surface. After irradiation for 6 hours at an intensity of m ² , the contact angle of water was measured. The contact angle is preferably 10 ° or less, more preferably 6 ° or less from the viewpoint of antifouling properties. The sample was subjected to a Taber abrasion test (number of wear: 100, load: 4.9N.), And the haze value before and after the abrasion test was measured (measurement instrument name: Directly read haze computer manufactured by Suga Test Instruments Co., Ltd.). I asked. The amount of change is preferably 3% or less from the viewpoint of wear resistance.

 [Anti-fouling property]

 After exposing the sample immediately after the preparation to the outdoors for one month, the degree of dirt (slight dirt is not noticeable: 〇, slightly dirt is noticeable: △, considerably dirt is noticeable: X.) was visually observed.

 [Anti-fogging property]

 The sample immediately after the preparation was blown, and the presence or absence of fogging (no fogging: Δ, occurrence of fogging: X.) was visually observed.

 [Example 1]

 A soda-lime glass plate (10 OmmX 100 mm, thickness 3.5 mm) was prepared, its surface was polished with cerium oxide, washed with distilled water, and dried to obtain a pre-treated glass plate.

Kei sodium No.4 to 37. 5 g of water (trade name:. Nippon Chemical Industrial Co., Ltd. S i 0 _2:. 23 35 _{wt%, Na 2 O:. 6.} 29 wt% S i 0 ₂ / Na ₂ The molar ratio of O: 3.83.;) Was added, and a strongly acidic cation exchange resin (manufactured by Mitsubishi Chemical Corporation, trade name)

"SK1BH". ) Was added thereto, and the mixture was stirred at room temperature for 10 minutes to prepare a desalted sodium carbonate solution (0.12 parts by mass of sodium ion with respect to 100 parts by mass of keic acid).

 In addition, 9 g of an aqueous dispersion (solid content concentration: 10% by mass) of anatase-type titanium oxide fine particles (average particle diameter: 56 nm; hereinafter, referred to as photocatalyst A) was added to 32.lg of 2-propanol. And 8.9 g of desalted sodium carbonate solution, and then a surfactant “L-77” (trade name, manufactured by Nippon Tunicer) was added to the solution so that the amount became 100 ppm. Thus, a coating solution 1 (sodium ion concentration was 12 ppm) was obtained.

2 mL of the obtained coating solution 1 was dropped on the surface of the treated glass plate, and spin-coated. After coating by the method, the sample was baked at 200 ° C. for 60 minutes in an air atmosphere to obtain a sample having a photocatalytic film having a thickness of 8 Onm.

 [Example 2]

Kei lithium 75 to 36. 07 g of water (trade name:. Nippon Chemical Industrial Co., Ltd. S i 0 _2: 21. 54 _{wt%, L i 2 O:.} 1. 43 wt% S I_〇 ₂ / L i ₂ 〇 molar ratio: 7. 49. 13. add 93 g of) was further added 30 g of "SK1BH", stirred at room temperature for 10 minutes desalting Kei lithium solution (100 Kei acid The amount of lithium ion was 0.13 parts by mass with respect to parts by mass.).

 Also, to 32.lg of 2-propanol, add 9g of photocatalyst A and 8.9g of lithium desalted silicate solution, and then add L_77 so that it becomes 100 ppm based on the liquid volume. Thus, a coating solution 2 (the lithium ion concentration was 13 ppm) was obtained. A sample having a photocatalytic film with a thickness of 83 nm was obtained in the same manner as in Example 1 using the obtained Coating Liquid 2.

 [Example 3]

 To 32. lg of 2-propanol, add 10.5 g of photocatalyst A and 6.69 g of the desalted sodium silicate solution in Example 1, and further add "L-77" to 10 Op pm to obtain a coating solution 3 (sodium ion concentration: 7 ppm). A sample having a photocatalytic film having a thickness of 82 nm was obtained in the same manner as in Example 1 using the obtained coating liquid 3.

 [Example 4]

 To 32.lg of 2_propanol, 4.5 g of photocatalyst A and 15.6 g of the desalted sodium silicate solution in Example 1 were added, and “L-77” was added at 100 pp to the volume. m to give a coating solution 4 (sodium ion concentration: 23 ppm). A sample having a photocatalyst film having a thickness of 83 nm was obtained in the same manner as in Example 1 using the obtained coating solution 4.

 [Example 5]

 A sample was obtained in the same manner as in Example 1 except that surfactant Q was used instead of “L_77”.

 [Example 6]

In Example 1, instead of baking at 200 ° C for 60 minutes in air atmosphere, A sample was obtained by baking for 30 minutes at 3 o or: medium.

 [Example 7]

 In Example 1, instead of firing at 200 in the air atmosphere for 60 minutes, the sample was fired at 650 ° C for 5 minutes in the air atmosphere to obtain a sample.

 [Example 8] (Comparative example)

 5 g of tetramethoxysilane was added to 90 g of ethanol, and after stirring for 10 minutes, 5 g of an aqueous nitric acid solution (1% by mass) was gradually added to obtain a hydrolysis product B of tetramethoxysilane.

 To 32.1 g of 2-propanol, 9 g of the photocatalyst A and 8.9 g of the hydrolysis product B were added, and “L_77” was further added so as to be 100 ppm with respect to the liquid volume. As a result, a coating solution 8 (sodium ion concentration was 0 ppm) was obtained.

 Using the obtained coating solution 8, a sample having a photocatalytic film having a thickness of 80 nm was obtained in the same manner as in Example 1.

 [Example 9] (Comparative example)

 To 23.1 of 2-propanol, add 9 g of photocatalyst A and 8.9 g of Soda-4 (26.9 parts by mass of sodium ion with respect to 100 parts by mass of citric acid). As a result, a precipitate was generated and could not be formed into a coating solution.

 [Example 10]

 A polycarbonate resin plate with a silicone hard coat (10 Omm X 10 Omm, thickness 5. Omm) was prepared, and the surface of the hard coat was washed with distilled water and then dried to obtain a pre-treated polycarbonate plate.

 2 mL of the coating solution 1 obtained in Example 1 was dropped on the surface of the treated polycarbonate plate, and applied by a spin coating method. Then, using a low-pressure UV irradiation device (PL7-200 manufactured by Sen Engineering Co., Ltd.) With the distance between the lamp and the resin plate being 2 cm, irradiation with ultraviolet light was performed for 5 minutes to obtain a sample having a photocatalytic film having a thickness of 8 Onm. Here, the term “ultraviolet light” refers to high-energy ultraviolet rays (hereinafter referred to as UV-C) with a main wavelength of 253.7 nm and 184.9 nm from a low-pressure mercury lamp.

 [Example 11]

In Example 10, the polycarbonate resin plate with the silicone hard coat was washed and dried, and then irradiated with UV-C for 2 minutes using the low-pressure UV irradiator described above. A sample was obtained in the same manner as in Example 10, except that the substrate was a nate plate.

 [Example 1 2]

 In Example 10, instead of irradiating UV-C for 5 minutes, using a metal halide lamp (M03-L31, manufactured by FG Co., Ltd.) and setting the distance between the lamp and the resin plate to 10 cm, ultraviolet rays Was irradiated for 5 minutes to obtain a sample having a photocatalyst film having a thickness of 80 nm. The metal halide lamp here refers to a lamp with a wavelength of 300 to 450 nm, which emits longer wavelength ultraviolet light than a low-pressure mercury lamp.

 table 1

Industrial applicability

 ADVANTAGE OF THE INVENTION According to this invention, the composition for photocatalyst film formation which can provide the outstanding hydrophilicity to the surface of a base material is obtained. Further, the photocatalytic film-forming composition of the present invention can be used to form a photocatalytic film having excellent hydrophilicity at a low temperature, and the surface of the substrate provided with the photocatalytic film has excellent hydrophilicity. Further, the photocatalyst film formed using the composition for forming a photocatalyst film of the present invention is particularly excellent in soil decomposability and has a long hydrophilicity duration. For this reason, the surface is always kept clean.

The surface of the substrate provided with excellent hydrophilicity, formed using the composition for forming a photocatalytic film of the present invention, has excellent dripability, antifogging property, antifouling property, and abrasion resistance. In other words, by imparting hydrophilicity to the surface of the base material, water droplets adhering to the surface of the base material wet and spread, and the surface becomes cloudy. No. In addition, the decomposition of dirt (particularly the decomposition of organic dirt) is further promoted by irradiation with light such as sunlight. Furthermore, when water flows down the surface of the article due to rainfall or the like, the dirt on the organic material also flows down (self-cleaning effect).

Claims

The scope of the claims

I. A composition for forming a photocatalyst film, which essentially comprises photocatalyst semiconductor fine particles, the following silica precursor and a medium.

 Silicity precursor: A gay acid compound containing 0.001 to 1 part by mass of an alkali metal ion with respect to 100 parts by mass of cayic acid.

 2. The composition for forming a photocatalyst film according to claim 1, wherein the average particle diameter of the photocatalyst semiconductor fine particles is 5 to 90 nm.

 3. The photocatalytic film forming composition according to claim 1, wherein the concentration of the alkali metal ion in the photocatalytic film forming composition is 1 to 80 ppm in terms of mass with respect to the photocatalytic film forming composition. Composition.

 4. The composition for forming a photocatalyst film according to claim 1, 2 or 3, wherein the silica precursor is formed by removing a part of an alkali metal ion from an alkali metal salt of cayic acid.

 5. The photocatalyst film according to claim 1, 2, or 3, wherein the silica precursor is formed by removing a part of alkali metal ions from an alkali metal salt of cayic acid using a cation exchange resin. Forming composition.

 6. The composition for forming a photocatalyst film according to claim 4 or 5, wherein the alkali metal salt of a keic acid is sodium silicate and Z or lithium silicate.

 7. The composition for forming a photocatalyst film according to any one of claims 1 to 6, wherein the silica precursor is contained in an amount of 25 to 900 parts by mass based on 100 parts by mass of the photocatalytic semiconductor fine particles.

 8. The total amount of the photocatalytic semiconductor fine particles and the silylation precursor is 0.5 to 50 parts by mass based on 100 parts by mass of the composition for forming a photocatalytic film. 12. The composition for forming a photocatalyst film according to item 10.

 9. A photocatalyst film formed on the surface of a substrate from the composition for forming a photocatalyst film according to any one of claims 1 to 8.

 10. It is formed by performing a pretreatment on the surface of the substrate, applying the composition for forming a photocatalyst film according to any one of claims 1 to 8 to the surface, and then performing a post-treatment. Photocatalytic film.

II. The photocatalytic film according to claim 10, wherein the post-treatment is irradiation with electromagnetic waves.

12. The photocatalyst film according to claim 9, 10 or 11, wherein the thickness of the photocatalyst film is 10 to 300 nm.

 13. A substrate with a photocatalyst film having the photocatalyst film according to any one of claims 9 to 12 on the surface of the substrate.

 14. The substrate with a photocatalytic film according to claim 13, wherein the substrate is glass or an organic resin.

15. The substrate with a photocatalyst film according to claim 13 or 14, wherein the visible light transmittance of the substrate with a photocatalyst film is 70% or more.