JP2006070141A - Composition for forming photocatalyst membrane and substrate with the photocatalyst membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for forming a photocatalyst membrane, which is suitable for forming the photocatalyst membrane excellent in stain degradation and hydrophilicity persistence through a spraying method, the photocatalyst membrane formed from the composition and a substrate with the photocatalyst membrane. <P>SOLUTION: The composition for forming the photocatalyst membrane through spraying essentially comprises a photocatalyst semiconductor particulate, a silica precursor and a solvent, wherein the solvent comprises an alcohol with a boiling point of ≤90°C and an alcohol with a boiling point of >90°C but ≤130°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composition for forming a photocatalyst film 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.

  It is known that when the photocatalyst is photoexcited, organic stains and the like attached to the surface of the photocatalyst are decomposed, and as a result, a hydrophilic surface is realized. It is known to use a specific silica precursor for the purpose of forming a photocatalyst film having excellent soil decomposability and excellent hydrophilic durability (see, for example, Patent Document 1). However, this photocatalyst composition does not prescribe a preferred composition range for a particular coating method such as spraying.

International Publication No. 03/068771 Pamphlet

  The present invention relates to a composition for forming a photocatalyst film suitable for forming a photocatalyst film excellent in soil decomposability and hydrophilic sustainability by a spray method, a photocatalyst film formed from the composition, and a substrate with the photocatalyst film The purpose is to provide.

  The present invention is a composition for forming a photocatalyst film comprising the photocatalyst semiconductor fine particles, the following silica precursor, and a solvent, including an alcohol having a boiling point of 90 ° C. or lower and an alcohol having a boiling point of 90 ° C. or higher and 130 ° C. or lower as a solvent, The total amount of the photocatalyst semiconductor fine particles and the solid content of the silica precursor with respect to 100 parts by mass of the composition is 0.3 to 1.2 parts by mass, and the content of alcohol having a boiling point of 90 ° C. or less is 40 to 65 parts by mass. And a composition for forming a photocatalyst film for spraying (silica precursor: 100 parts by mass of silicic acid), wherein the content of the alcohol having a boiling point of 90 ° C. or more and 130 ° C. or less is 25 to 50 parts by mass. A silicic acid compound containing 0.001 to 1 part by mass of metal ions).

  With the composition for forming a photocatalyst film of the present invention, a photocatalyst film excellent in hydrophilicity, soil decomposability, hydrophilicity persistence, and abrasion resistance and a substrate with the photocatalyst film can be obtained by a spray method.

  Examples of the method for forming a film by a wet method include coating methods such as spraying, brush coating, roller coating, spin coating, dip coating, coating by various printing methods, curtain flow, die coating, and flow coating. However, among these methods, as a method of forming a coating film on a substrate such as glass or resin installed in an existing building, the uniformity of the coating film on the appearance and the workability are excellent. In some cases, the spray method is used. In particular, when a composition is applied to a large-area substrate, there is a problem that rotation is very difficult by a method such as spin coating, and the spray method is excellent also in this respect.

  The spray method has a characteristic that droplets of the coating liquid are sprayed from the tip of the spray gun toward the substrate. Therefore, when a composition containing fine particles of, for example, 1 μm or less is applied to the substrate surface by a spray method, if the drying speed of the solvent contained in the composition is too high, droplets of the composition land on the substrate surface. It was found that there was a problem that the droplets dried before and the fine particles became a lump of several hundred μm and adhered to the surface of the base material, and the uniformity in appearance was impaired. On the other hand, if the drying speed of the solvent contained in the composition is too slow, after the droplets land on the surface of the substrate, the droplets flow downward due to the gravity of the droplets, etc. It was found that there was a problem that the uniformity above was impaired.

  The present inventors have found that a composition suitable for the spray method can be obtained by using a specific solvent or fine particles.

Hereinafter, the present invention will be described in detail.
In the present invention, the photocatalytic semiconductor fine particle means 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, conduction electrons and positive electrons are excited by excitation of electrons in the valence band. A material having the property of generating pores. Preferred examples of the material for 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 size of the photocatalytic semiconductor fine particles in the present invention is obtained by measuring the aggregate particle size of the fine particles with a dynamic light scattering particle size analyzer (manufactured by Nikkiso, model: Microtrac UPA), preferably 5 to 90 nm, particularly Preferably it is 40-70 nm. When the average particle size is small, the photocatalyst fine particles are buried in the formed photocatalyst film, so that various effects of the photocatalyst are hardly exhibited. On the other hand, if the average particle size is 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 in which 0.001 to 1 part by mass of alkali metal ions is contained with respect to 100 parts by mass of silicic acid, and in particular, 0.001 to 0.2 parts by mass is contained. It is particularly preferable that 0.001 to 0.15 parts by mass is included. The alkali metal ion concentration is measured by ICP emission analysis using SPS4000 manufactured by Seiko Instruments Inc. There is no limitation in particular as an alkali metal ion, 1 type may be used and 2 or more types may be used. As the alkali metal ion, sodium ion or lithium ion is preferable. Moreover, a silicic acid compound means the compound which forms a silica film by performing post-processing as mentioned later.

  The silica precursor in the present invention is preferably a product obtained by removing a part of alkali metal ions from an alkali metal salt of silicic acid. The product is obtained, for example, by a method of reducing alkali metal ions from an alkali metal salt of silicic acid using a cation exchange resin. The amount of alkali metal ions to be reduced can be adjusted by controlling the amount of cation exchange resin used, the contact time, the contact method, and the like.

As the cation exchange resin, strong acid cation exchange resin (RSO ₃ H type), weak acid cation exchange resin (RCOOH type), etc. can be used, but the reaction rate is to use strong acid cation exchange resin. This is preferable.

  In the composition for forming a photocatalyst film of the present invention, the concentration of alkali metal ions is preferably 0.2 to 80 ppm in terms of mass relative to the composition for forming a photocatalyst, particularly 0.2 to 40 ppm, and more preferably 0. It is preferably 2 to 20 ppm. If the alkali metal ion concentration is too small, the hydrophilicity of the formed photocatalyst film is deteriorated, which is not preferable. On the other hand, if the concentration of alkali metal ions is too large, the stability of the composition is significantly reduced, which is not preferable.

  Examples of the alkali metal salt of silicic acid include one or more selected from the group of sodium silicate, lithium silicate, and potassium silicate, and sodium silicate and / or lithium silicate are particularly preferable.

As sodium silicate, materials having different composition ratios of SiO ₂ / Na ₂ O are known, and can be used without any particular limitation. Among them, a material having a small content ratio of Na ₂ O is preferable because alkali metal ions can be easily removed. As commercially available sodium silicate, sodium silicate No. 1 (SiO ₂ / Na ₂ O molar ratio: 2.0 to 2.3), sodium silicate No. 2 (same molar ratio: 2.4 to 2.7) ), Sodium silicate 3 (same molar ratio: 3.0 to 3.3), and sodium silicate 4 (same molar ratio: 3.7 to 3.9). Sodium silicate No. 3 or No. 4 having a small Na ₂ O content ratio is particularly preferred.

As lithium silicate, materials having different composition ratios of SiO ₂ / Li ₂ O are known, and can be used without particular limitation. Among them, a material having a small Li ₂ O content ratio is preferable because alkali metal ions can be easily removed. As commercially available lithium silicate, lithium silicate 35 (SiO ₂ / Li ₂ O molar ratio: 3.5) (lithium silicate 35 is a trade name manufactured by Nippon Chemical Industry Co., Ltd., 45, 75 below. And lithium silicate 45 (same molar ratio: 4.5) and lithium silicate 75 (same molar ratio: 7.5). In particular, lithium silicate 75 having a small content ratio of Li ₂ O is particularly preferable.

  In the present invention, the total amount of the photocatalyst semiconductor fine particles and the solid content of the silica precursor is 0.3 to 1.2 parts by mass with respect to 100 parts by mass of the photocatalyst film forming composition. If it is less than 0.3 parts by mass, the film thickness of the formed photocatalyst film becomes small, and hydrophilicity and dirt degradability deteriorate, which is not preferable. On the other hand, when the amount is larger than 1.2 parts by mass, the fine particles adhere to the surface of the base material when sprayed and adhere to the surface of the substrate, which is not preferable. More preferably, it is 0.5-0.9 mass part. If it is 0.5-0.9 mass part, it is especially excellent in stain | pollution | contamination decomposability, and more preferable. In addition, solid content means the component which forms a film | membrane after film-forming, for example, the solid content of a silica precursor means the silicic acid contained in a silica precursor.

  In this invention, it is preferable that 25-900 mass parts of solid content of the said silica precursor is contained with respect to 100 mass parts of said photocatalyst semiconductor fine particles. If it is less than 25 parts by mass, the mechanical strength of the formed photocatalyst film becomes weak and the film is easily damaged. On the other hand, when it is larger than 900 parts by mass, the soil decomposability deteriorates, which is not preferable. More preferably, it is 50-400 mass parts.

  The composition for forming a photocatalyst film of the present invention contains a solvent. The solvent contains an alcohol having a boiling point of 90 ° C. or lower and an alcohol having a boiling point higher than 90 ° C. and 130 ° C. or lower in a predetermined ratio in order to obtain a composition suitable for the spray method. The alcohol may be a monohydric alcohol or a polyhydric alcohol. In addition, water or the like may be included as a solvent.

  Examples of the alcohol having a boiling point of 90 ° C. or lower include methanol (boiling point: 65 ° C.), ethanol (boiling point: 78 ° C.), 2-propanol (boiling point: 83 ° C.), and tert-butanol (boiling point 83 ° C.). These alcohol solvents have a feature that the evaporation rate is high and the photocatalytic semiconductor fine particles and the silica precursor hardly aggregate, and the alcohol increases the charges of the photocatalytic semiconductor fine particles and the silica precursor and repels each other. It is preferable because it works to prevent aggregation. The content of alcohol having a boiling point of 90 ° C. or less is preferably 40 to 65 parts by mass with respect to 100 parts by mass of the composition. If it is less than 40 parts by mass, the drying speed is too slow when the composition is spray-coated, and after landing on the surface of the substrate, the droplets flow due to the influence of gravity, etc., resulting in uneven coating and uniformity in appearance. Is unfavorable because it is damaged. On the other hand, if it is larger than 65 parts by mass, when the composition is spray-coated, the drying speed is too fast, and the droplets are dried before landing on the surface of the substrate, and the fine particles become a lump of several hundred μm. It is not preferable because it adheres and the appearance uniformity is impaired. More preferably, it is 45-60 mass parts with respect to 100 mass parts of compositions.

  On the other hand, as alcohols having a boiling point of more than 90 ° C. and not more than 130 ° C., 1-propanol (boiling point: 97 ° C.), 1-butanol (boiling point: 118 ° C.), 2-butanol (boiling point: 100 ° C.), 2-methyl-1- Propanol (boiling point: 108 ° C), cyclobutanol (boiling point: 123 ° C), 2-buten-1-ol (boiling point: 122 ° C), 3-buten-1-ol (boiling point: 113 ° C), 3-butene-2 -Ol (boiling point: 97 ° C.), 3-butyn-1-ol (boiling point: 129 ° C.). Among these alcohols, the photocatalyst semiconductor fine particles and the silica precursor are liable to agglomerate. However, since the evaporation rate is slow, the use of the alcohol in combination with the alcohol having a boiling point of 90 ° C. or lower allows A composition for forming a photocatalyst film suitable for the coating method can be obtained. The content of alcohol having a boiling point of more than 90 ° C and not more than 130 ° C is preferably 25 to 50 parts by mass with respect to 100 parts by mass of the composition. If it is less than 25 parts by mass, the drying speed is too high when the composition is spray-coated, and the droplets are dried before landing on the surface of the substrate, and the fine particles adhere as a lump of several hundred μm. Since the uniformity in appearance is impaired, it is not preferable. On the other hand, when the amount is larger than 50 parts by mass, the photocatalyst semiconductor fine particles and the silica precursor are aggregated, and spray coating cannot be performed. More preferably, it is 30-45 mass parts.

The composition for forming a photocatalyst film of the present invention preferably contains a surfactant. The surfactant mainly has two functions, the first is to ensure the wettability of the composition to the substrate, and the second is the hydrophilicity of the photocatalyst film formed using the composition. It is to make sex higher. The type of the 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 polyoxyalkylene and the hydrophobic part is a fluorine-containing organic group [for example, C ₈ F ₁₇ CH ₂ CH ₂ CH (CH ₃ ) O (CH ₂ CH ₂ O) _x (CH ₂ CH (CH ₃ ) O) Compounds represented by _y H [x: y = 70: 30, x + y = 5.72, average molecular weight 800] and the like. ] Is preferable. Alternatively, a compound in which the hydrophilic part is polyoxyalkylene and the hydrophobic part is methylpolysiloxane (for example, trade name “L-77” manufactured by Nippon Unicar Co., Ltd.) is preferable.

  The composition for forming a photocatalyst film of the present invention may contain a functional additive. Preferred examples of the functional additive include coloring dyes, pigments, ultraviolet absorbers, antioxidants, and oxide fine particles (phosphorus pentoxide, magnesium oxide, etc.) other than the photocatalytic semiconductor fine particles in the present invention.

  Using the composition for forming a photocatalyst film of the present invention, the composition is applied to the surface of a substrate to form a photocatalyst film, and a substrate with a photocatalyst film is obtained. In the photocatalyst film, the silica precursor is converted to silica, but silanol groups may partially remain.

The silica precursor has a silanol group in the compound, that is, a structure represented by SiO _s (OH) _t (s, t is an integer of 0 or more, and s + t = 4). In other words, oxygen atoms that are not hydroxyl groups are chemically bonded to other silicon atoms.), And silica is formed from the silica precursor by a dehydration condensation reaction.

  The composition for forming a photocatalyst film of the present invention is a composition suitable for a spray method. The composition of the present invention can be preferably used when the substrate is installed horizontally with respect to the ground or when the substrate is installed vertically with respect to the ground. In particular, when the composition is applied to a base material that has already been installed in a building, the base material is often installed perpendicular to the ground. It tends to sag due to gravity and cause uneven coating. Since the composition of the present invention can be applied without such application unevenness, it is preferably used for a substrate already installed in a building, for example, a window glass of a building.

  In the present invention, the thickness of the resulting photocatalyst film can be controlled by adjusting the concentration, coating amount, etc. of the composition for forming the photocatalyst film. If the thickness of the photocatalyst film is too thick, the film has cracks, interference fringes, or scratches that are noticeable, and if it is too thin, the hydrophilicity and dirt degradability deteriorate. There is a fear. The thickness of the photocatalytic film is preferably 5 to 90 nm, and particularly preferably 20 to 80 nm.

  The base material used for this invention is not specifically limited. The shape of the substrate is not limited to a flat plate, and may have a curvature on the entire surface or a part thereof. The base material used in the present invention is preferably a transparent base material such as glass or organic resin in that the composition of the present invention can maintain transparency. Examples of the glass include soda lime glass mainly used for plate glass and automotive glass. Examples of the organic resin include resins such as polycarbonate, acrylic, polyethylene, polypropylene, and polyethylene terephthalate. 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 (JIS R3106 (1998)) of the substrate with a photocatalyst film is 70% from the viewpoint of visibility. The above is preferable.

  The substrate may be pretreated. Examples of the pretreatment include plasma treatment, corona discharge, UV treatment, discharge treatment such as ozone treatment, chemical treatment using acid or alkali, 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 uniformly applied, and the adhesion of the formed photocatalytic film to the substrate can be enhanced. In particular, when the substrate is an organic resin, pretreatment is preferably performed. In general, a pretreatment performed by ultraviolet irradiation by a low-pressure mercury lamp or the like generally used for plastic modification is particularly effective.

  A photocatalyst film is obtained by spraying the composition for forming a photocatalyst film of the present invention on a substrate and drying it. In this case, drying at room temperature is sufficient, but post-treatment may be performed for the purpose of increasing the hardness of the photocatalyst film. Examples of the post-treatment include heating and irradiation with electromagnetic waves such as ultraviolet rays and electron beams. In consideration of the heat resistance of the substrate, the heating is preferably performed at 50 to 700 ° C., particularly at 100 to 350 ° C. for 5 to 60 minutes. When the base material is a material with low heat resistance such as an organic resin, or when low molecular compounds in the base material diffuse out of the base material by heating, irradiation with electromagnetic waves such as ultraviolet rays and electron beams is performed as a post-treatment. Preferably it is done.

Moreover, the coating amount of the composition for forming a photocatalyst film varies somewhat depending on the film thickness to be formed, but is preferably 5 to 150 ml / m ² . If the coating amount is too small, the formed film thickness becomes small, and there is a possibility that the hydrophilicity and dirt decomposability are deteriorated. On the other hand, if the coating amount is too large, not only coating unevenness is likely to occur, but also the film thickness that is formed becomes large, cracks occur in the film, interference fringes occur, or scratches are noticeable. There are drawbacks. A more preferable range of the coating amount is 10 to 100 ml / m ² .

  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, aircrafts, window glass, mirrors, various display element cover plates, and the like. Examples of building articles include outer walls, window glass, structures such as bridges and tunnels, and the like. Other applications include lighting cover glass and sound insulation walls. In particular, it is suitably used for window glass already installed in buildings.

  The base material with a photocatalyst film of the present invention has an antifogging property that its surface is excellent in hydrophilicity, so that water droplets adhering to the surface spread out and the surface does not become cloudy. In addition, organic dirt is decomposed on the surface. Furthermore, the degradation performance of organic dirt is further improved by light irradiation on the surface. Furthermore, when raindrops flow down the surface due to rain, dirt also flows down at the same time. The base material with a photocatalyst film of the present invention can be expected to have effects such as ensuring visibility, protecting aesthetics, or reducing maintenance costs.

A photocatalyst film formed from the composition for forming a photocatalyst film of the present invention is obtained by hydrolyzing Si (OR) ₄ (R: alkyl group), which is a conventional alkoxysilane, SiO _p (OH) _q (OR) r (p, q is an integer of 0 or more, r is an integer of 1 or more, and p + q + r = 4) (in this structure, an oxygen atom that is not a hydroxyl group includes another silicon atom) It is superior in hydrophilic sustainability and soil decomposability than a film formed from a composition using a product having a chemical bond.

  The base material with a photocatalyst film of the present invention may be provided with another film between the base material and the photocatalyst film or on the photocatalyst film. Examples of the another film include an alkali barrier layer (a layer intended to prevent diffusion of alkali metal into the photocatalyst film when the base material is alkali metal-containing glass), a protective film, and the like.

  Hereinafter, the present invention will be specifically described with reference to Examples (Examples 1 to 6) and Comparative Examples (Examples 7 to 11). Samples were prepared and evaluated using the following methods. The evaluation results are shown in Table 1.

[appearance]
A case where the coating unevenness was observed on the sample surface with the naked eye or the microparticles were adhered in the form of a lump of several hundreds μm by microscopic observation was marked as x. In addition, the case where there was no such defect was marked as ◯.

[Haze]
Transparency was evaluated by measuring the haze value of the sample. The haze measurement was performed by JIS K-7105 (1981) with a haze computer (HGM-3DP type, manufactured by Suga Test Instruments Co., Ltd.). This JIS standard is mainly a test method for plastics. In this evaluation, this test method is applied to glass. A haze value of 2% or less is preferred for practical use because of its excellent transparency.

[Membrane strength (Abrasion resistance)]
The sample is subjected to a Taber abrasion test (wear frequency: 20 times, load: 4.9 N), and the haze value before and after the abrasion test is measured with a haze computer (HGM-3DP type, manufactured by Suga Test Instruments Co., Ltd.). Asked. A change amount of 2% or less is practically preferable.

[Hydrophilic]
Immediately after the preparation of the sample, the initial water droplet contact angle that was not irradiated with light was measured using a contact angle meter (Kyowa Interface Science Co., Ltd., CA-X type). The water droplet contact angle was evaluated as ◯ when the angle was 10 ° or less, and x when the angle exceeded 10 °.

[Hydrophilic durability]
Immediately after the sample was prepared, the sample was kept in an environment free from light for 1 week, and then the contact angle of the water droplet was measured. A case where the water droplet contact angle is maintained at 10 ° or less was evaluated as ◯, and a case where the water droplet contact angle exceeded 10 ° was evaluated as ×. Even after one week, the water droplet contact angle is preferably 10 ° or less from the viewpoint of maintaining hydrophilicity.

[Soil degradability]
After attaching oleic acid to the sample immediately after production to create a dirty surface with a water droplet contact angle of about 70 °, the surface was irradiated with black light (center wavelength 365 nm) at an intensity of 0.5 mW / cm ² for a predetermined time. The water droplet contact angle was measured. When the water droplet contact angle is 10 ° or less after irradiation within 6 hours, ◎, when the water droplet contact angle is 10 ° or less after irradiation within 24 hours, ○, 10 ° or less even when irradiated for 24 hours What did not become was set as x. It is preferable from the viewpoint of antifouling property that the irradiation is within 10 ° after irradiation within 24 hours.

[Anti-fouling]
The sample immediately after preparation was exposed outdoors for one month, and then the degree of contamination was observed with the naked eye. The case where the dirt was not noticeable was rated as “◯”, the case where the dirt was slightly noticed as “Δ”, and the case where the dirt was noticeable as “x”.

[Anti-fogging property]
The sample immediately after preparation was blown, and the presence or absence of cloudiness was observed with the naked eye. No cloudiness was indicated by ○, and occurrence of cloudiness was indicated by ×.

[Example 1] Example A soda-lime glass plate (100 mm x 100 mm, thickness 3 mm) was prepared, its surface was polished with cerium oxide, washed with distilled water and dried to obtain a pretreated glass plate.
To 79.4 g of water, sodium silicate 3 (manufactured by Dokai Chemical Industries, SiO ₂ : 24.3 mass%, Na ₂ O: 7.62 mass%. SiO ₂ / Na ₂ O molar ratio: 3.3 20.6 g), 63 g of a strongly acidic cation exchange resin (product name “Diaion SK1BH” manufactured by Mitsubishi Chemical) was added, and the mixture was stirred for 10 minutes at room temperature to remove sodium silicate. The liquid (0.02 mass part of sodium ions with respect to 100 mass parts of silicic acid) was adjusted.

Also, 53.3 g of 2-propanol (boiling point: 83 ° C.), 4.8 g of an aqueous dispersion (solid content concentration: 10% by mass) of anatase-type titanium oxide fine particles (average particle size: 60 nm), demineralized silica 6.4 g of acid soda liquid and 35.5 g of 1-butanol (boiling point: 118 ° C.) were added, and further a surfactant (trade name: L-77, manufactured by Nihon Unicar Co., Ltd.) was added to the liquid amount. It added so that it might become 0.5 ppm, and the coating liquid 1 was obtained. This coating liquid 1
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of the composition = 0.8 parts by mass Content of 2-propanol with respect to 100 parts by mass of the composition = 53 parts by mass of 1-butanol with respect to 100 parts by mass of the composition Content = 36 parts by mass Sodium ion concentration in the composition is 0.6 ppm
Met.

The obtained coating liquid 1 was spray-coated on the surface of the treated glass plate using a spray gun. The coating amount was 60 ml / m ² . After application, the sample was left to stand at room temperature for one day and dried to obtain Sample 1 having a photocatalyst film having a thickness of 60 nm.

[Example 2] A coating liquid 2 was obtained in the same manner as in Example 1 except that the preparation of the coating liquid in Example 1 was changed to 40.0 g of 2-propanol and 48.8 g of 1-butanol. This coating liquid 2 is
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of the composition = 0.8 parts by mass Content of 2-propanol with respect to 100 parts by mass of the composition = 40 parts by mass of 1-butanol with respect to 100 parts by mass of the composition Content = 49 parts by mass Sodium ion concentration in the composition is 0.6 ppm
Met.

  The obtained coating liquid 2 was sprayed and dried in the same manner as in Example 1 to obtain Sample 2 having a photocatalytic film having a thickness of 60 nm.

[Example 3] A coating liquid 3 was obtained in the same manner as in Example 1 except that 62.2 g of 2-propanol and 26.6 g of 1-butanol were prepared in the preparation of the coating liquid in Example 1. This coating solution 3
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of the composition = 0.8 parts by mass Content of 2-propanol with respect to 100 parts by mass of the composition = 62 parts by mass of 1-butanol with respect to 100 parts by mass of the composition Content = 27 parts by mass Sodium ion concentration in the composition is 0.6 ppm
Met.

  The obtained coating liquid 3 was sprayed and dried in the same manner as in Example 1 to obtain Sample 3 having a photocatalytic film having a thickness of 60 nm.

Example 4 In the preparation of the coating liquid in Example 1, 56.6 g of 2-propanol, 2.4 g of an aqueous dispersion of anatase-type titanium oxide fine particles, 3.2 g of sodium silicate solution dehydrated, and A coating solution 4 was obtained in the same manner as in Example 1 except that 37.8 g of 1-butanol was used. This coating solution 4 is
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of composition = 0.4 parts by mass Content of 2-propanol with respect to 100 parts by mass of composition = 57 parts by mass of 1-butanol with respect to 100 parts by mass of composition Content = 38 parts by mass Sodium ion concentration in the composition is 0.3 ppm
Met.

  The obtained coating liquid 4 was sprayed and dried in the same manner as in Example 1 to obtain Sample 4 having a photocatalytic film having a thickness of 30 nm.

[Example 5] Using the coating solution 1 of Example Example 1, except that the spray coating amount was 30 ml / m ^2, to obtain a sample 5 with a photocatalyst film having a thickness of 30nm in the same manner as in Example 1.

Example 6 A sample 6 having a photocatalytic film having a thickness of 10 nm was obtained in the same manner as in Example 1 except that the coating amount 1 of Example 1 was used and the spray coating amount was 10 ml / m ² .

[Example 7] Comparative example (when 1-butanol is too much)
In the preparation of the coating liquid in Example 1, when 2propanol was 35.5 g and 1-butanol was 53.3 g, the liquid aggregated and precipitated immediately after the addition of 1-butanol, and could not be applied by the spray method. . This coating liquid 7
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of the composition = 0.8 parts by mass Content of 2-propanol with respect to 100 parts by mass of the composition = 36 parts by mass of 1-butanol with respect to 100 parts by mass of the composition Content = 53 parts by mass Sodium ion concentration in the composition is 0.6 ppm
Met.

[Example 8] Comparative example (when 1-butanol is too little)
A coating solution 8 was obtained in the same manner as in Example 1 except that 66.6 g of 2-propanol and 22.2 g of 1-butanol were prepared in the preparation of the coating solution in Example 1. This coating liquid 8
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of the composition = 0.8 parts by mass Content of 2-propanol with respect to 100 parts by mass of the composition = 67 parts by mass of 1-butanol with respect to 100 parts by mass of the composition Content = 22 parts by mass Sodium ion concentration in the composition is 0.6 ppm
Met.

  The obtained coating liquid 8 was sprayed and dried in the same manner as in Example 1 to obtain Sample 8 having a photocatalytic film having a thickness of 60 nm.

[Example 9] Comparative example (when solid content concentration is too high)
In the preparation of the coating liquid in Example 1, 46.6 g of 2-propanol, 9.6 g of an aqueous dispersion of anatase-type titanium oxide fine particles, 12.8 g of sodium silicate solution removed with sodium, and 31. 1-butanol. A coating solution 9 was obtained in the same manner as in Example 1 except that the amount was 0 g. This coating liquid 9
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of the composition = 1.5 parts by mass Content of 2-propanol with respect to 100 parts by mass of the composition = 47 parts by mass of 1-butanol with respect to 100 parts by mass of the composition Content = 31 parts by mass Sodium ion concentration in the composition is 1.3 ppm
Met.

  The obtained coating liquid 9 was sprayed and dried in the same manner as in Example 1 to obtain Sample 9 having a photocatalytic film having a thickness of 110 nm.

[Example 10] Comparative example (when solid content concentration is too low)
In the preparation of the coating liquid in Example 1, 58.7 g of 2-propanol, 1.0 g of an aqueous dispersion of anatase-type titanium oxide fine particles, 1.3 g of sodium silicate solution removed with sodium, and 39. 1-butanol. A coating solution 10 was obtained in the same manner as in Example 1 except that the amount was 1 g. This coating solution 10 is
Total amount of titanium oxide fine particles and solid content of silica precursor with respect to 100 parts by mass of composition = 0.2 parts by mass Content of 2-propanol with respect to 100 parts by mass of composition = 59 parts by mass of 1-butanol with respect to 100 parts by mass of composition Content = 39 parts by mass Sodium ion concentration in the composition is 0.1 ppm
Met.

  A sample 10 having a photocatalyst film having a thickness of 4 nm was obtained in the same manner as in Example 1 except that the obtained coating liquid 10 was used and the amount of spray coating was changed to 30 ml / m2.

[Example 11] Comparative example (when 1-butanol is not present)
A soda lime glass plate (100 mm × 100 mm, thickness 3.5 mm) was prepared, the surface was polished with cerium oxide, washed with distilled water and dried to obtain a pretreated glass plate.

Sodium silicate No. 4 (trade name: manufactured by Nippon Chemical Industry Co., Ltd., SiO ₂ : 23.35% by mass, Na ₂ O: 6.29% by mass. Molar ratio of SiO ₂ / Na ₂ O: 37.5 g of water 3.83.) Is added, and 30 g of a strongly acidic cation exchange resin (trade name “SK1BH”, manufactured by Mitsubishi Chemical Corporation) is added and stirred at room temperature for 10 minutes to remove demineralized silica. An acid soda solution (0.12 parts by mass of sodium ions with respect to 100 parts by mass of silicic acid) was prepared.

  Further, 32.1 g of 2-propanol was added to 9 g of an aqueous dispersion (solid content concentration: 10% by mass) of anatase-type titanium oxide fine particles (average particle size: 56 nm) and 8. 9 g was added, and a surfactant “L-77” (trade name: manufactured by Nihon Unicar Co., Ltd.) was added so as to be 100 ppm with respect to the liquid volume, and coating liquid 11 (sodium ion concentration in the liquid was 12 ppm). .)

This coating liquid 11 was spray-coated on the surface of the treated glass plate using a spray gun. The coating amount was 60 ml / m ² . After application, the sample was left to stand at room temperature for one day and dried to obtain Sample 11 having a photocatalyst film having a thickness of 60 nm.

ADVANTAGE OF THE INVENTION According to this invention, the composition for photocatalyst film formation for the spray method which can provide the hydrophilic property excellent in the surface of a base material is obtained. Moreover, the photocatalyst film | membrane excellent in hydrophilic property can be formed using the composition for photocatalyst film formation of this invention, and the surface of this base material with a photocatalyst film | membrane is excellent in hydrophilicity. Furthermore, 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 hydrophilic duration. For this reason, the surface is always kept clean. Moreover, even if it is the base material already installed in the building, it can apply | coat without application | coating unevenness and is useful.

Claims (11)

A composition for forming a photocatalyst film comprising the photocatalyst semiconductor fine particles, the following silica precursor, and a solvent, wherein the composition comprises an alcohol having a boiling point of 90 ° C. or lower and an alcohol having a boiling point of 90 ° C. or higher and 130 ° C. or lower. The total amount of the photocatalyst semiconductor fine particles and the solid content of the silica precursor with respect to parts by mass is 0.3 to 1.2 parts by mass, the content of alcohol having a boiling point of 90 ° C. or less is 40 to 65 parts by mass, and the boiling point 90 The composition for forming a photocatalyst film for spraying, wherein the content of an alcohol having a temperature of more than 130 ° C and not more than 130 ° C is 25 to 50 parts by mass.
Silica precursor: a silicic acid compound containing 0.001 to 1 part by mass of alkali metal ions with respect to 100 parts by mass of silicic acid.   The composition for forming a photocatalyst film according to claim 1, wherein the content of alcohol having a boiling point of 90 ° C or lower is 45 to 60 parts by mass, and the content of alcohol having a boiling point of 90 ° C or higher and 130 ° C or lower is 30 to 45 parts by mass. .   The composition for forming a photocatalyst film according to claim 1 or 2, wherein the photocatalyst semiconductor fine particles have an average particle diameter of 5 to 90 nm.   The composition for forming a photocatalyst film according to claim 1, 2 or 3, wherein the concentration of alkali metal ions in the composition for forming a photocatalyst film is 0.2 to 80 ppm in terms of mass with respect to the composition for forming a photocatalyst film. object.   5. The composition for forming a photocatalyst film according to claim 1, wherein the silica precursor is formed by removing a part of alkali metal ions from an alkali metal salt of silicic acid.   The composition for forming a photocatalyst film according to claim 5, wherein the silica precursor is formed by removing a part of alkali metal ions from an alkali metal salt of silicic acid using a cation exchange resin.   The composition for forming a photocatalyst film according to any one of claims 1 to 6, wherein the silica precursor has a solid content of 25 to 900 parts by mass with respect to 100 parts by mass of the photocatalytic semiconductor fine particles.   The photocatalyst film formed by apply | coating the composition for photocatalyst film formation of any one of Claims 1-7 on the surface of a base material with a spray method.   The photocatalyst film according to claim 8, wherein the photocatalyst film has a thickness of 5 to 90 nm.   The base material with a photocatalyst film which has the photocatalyst film of Claim 8 or 9 on the surface of a base material. The substrate with a photocatalyst film according to claim 10, wherein the substrate is a substrate already installed in a building.