JPH0956788A - Cleaning method for bath room members - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the adhesion and growth of slime on a floor, a washing place, in a bathtub and on duckboards in a bath room to be prevented. SOLUTION: Bath room members are covered with a photocatalyst, which is photoexcited up to such a state that its durface is made superhydrophilic, so as to have a converted contact angle with water smaller than 10 deg.. Not only because insoluble soap scum, fat and other hydrophobic organic matter hardly adhere to the superhydrophilic surfacce, but also because they are easily washed away by being showered or wetted with water, a photocatalitic layer is kept clean on the surface. Bacterial, mold, yeast and the microbes immediately touch the surface of the photocatalitic layer, and thus, are effectively killed by the photooxidation of the photocatalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing so-called "neck" from adhering to or occurring on bathroom members such as a bathroom floor, a washing room, a bathtub, a side wall of a bathroom, a child's chair, and a bathroom stool.

[0002]

2. Description of the Related Art It is well known that a so-called "null" is attached to a floor of a bathroom, a bathtub, a side wall of a bathroom, or a child of a cage. Not only does slime give an unsanitary impression, but it is slippery and can cause a fall if you are not careful.

The slime is considered to be a mixture of bacteria, microorganisms such as molds and yeasts, secretions thereof, dirt from the human body such as fats and proteins, and decomposition products thereof. In order to remove sliminess, it is necessary to clean the bathroom floor, cage, etc. with detergent and scrubbing brush, so it takes time to manage the bathroom.

Japanese Patent Laid-Open No. 6-154118 (Matsushita Electric Industrial Co., Ltd.)
It has been proposed to prevent the slime from sticking by coating the bath with a coating composed of a highly water-repellent fluoropolymer and an antibacterial agent. Thus, according to the conventional wisdom, it has been considered that a water-repellent material is less likely to be contaminated with dirt, but recently, since a water-repellent material has an affinity for fats and oils, it is not It has been pointed out that adhesion of lipophilic substances is rather likely to occur.

In International Publication WO 94/11092 (Totoki), a photocatalyst coating is provided on the surface of a substrate such as a tile, and the photocatalyst is photoexcited by weak ultraviolet rays emitted from indoor lighting such as a fluorescent lamp. By doing so, it is disclosed that antibacterial and contaminants are decomposed.

However, when this technique is applied to the slime removal of a bathtub or a washing place, insoluble "soap residue" or a lipophilic organic pollution which is a reaction product of human dross and soap in the bathtub or the washing place is polluted. As the material attaches to the surface of the photocatalytic coating, the active sites of the photocatalytic coating are shielded from microorganisms such as bacteria, fungi and yeast. As a result, the antibacterial function of the photocatalyst is not fully exhibited.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cleaning method capable of preventing adhesion and occurrence of "neck" without requiring human labor and keeping bathroom members clean. It is in.

[0008]

The present inventors have discovered that the photocatalyst has a hydrophilizing action in addition to the conventionally known antibacterial action and photoredox action. Surprisingly, it was discovered that when photocatalytic titania was photoexcited, the surface became highly hydrophilic so that the contact angle with water was 10 ° or less, more specifically 5 ° or less, and especially about 0 °. Was done.

The present invention is based on such a discovery. The present invention cleans bathroom members such as a bathroom floor, a washroom, a bathtub, a bathroom side wall, a cage, and a bathroom stool to prevent slime adhesion. Provide a way. According to the present invention, the surface of the bathroom member is coated with a layer containing a semiconductor photocatalyst. When the photocatalyst is photoexcited, the photocatalyst is activated and the surface of the photocatalyst layer is made hydrophilic. Photoexcitation is carried out until the surface of the photocatalyst layer is converted to a contact angle with water of about 10 ° or less, preferably about 5 ° or less.

Such a highly hydrophilic surface is naturally exposed to water splashes or water wetting with the use of a bath, a washing room or a shower. The highly hydrophilic surface has no affinity for soap residue and lipophilic organic pollutants,
These contaminants are easily released from the surface and rinsed with water after each use of the bathroom. Therefore, the surface of the photocatalyst layer is kept clean. As a result, microorganisms such as bacteria, molds and yeasts attached to the surface of the bathroom member come into direct contact with the surface of the photocatalyst layer, and are effectively killed or grown by the photooxidation action of the photocatalyst. Be suppressed.

The above-mentioned features and effects of the present invention, as well as other features and advantages, will be apparent from the description of the following embodiments.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The surface of a bathroom member is covered with a semiconductor photocatalyst layer. The thickness of the photocatalyst layer is preferably 0.2 μm or less. With such a film thickness, the photocatalyst layer can be made sufficiently transparent, and color development due to light interference can be prevented.

The most preferable photocatalyst is titania (TiO ₂ ). Titania is harmless, chemically stable, and available at low cost. As the photocatalytic titania, either anatase or rutile can be used. The advantage of the anatase type titania is that a sol in which very fine particles are dispersed can be easily obtained on the market, and a very thin thin film can be easily formed. On the other hand, rutile-type titania has an advantage that it can be sintered at high temperature and a coating excellent in strength and wear resistance can be obtained.

When the bathroom member is coated with a titania photocatalyst layer and the titania is photoexcited with ultraviolet rays, the surface of the photocatalyst layer is converted into a contact angle with water of 10 ° or less, more specifically 5 ° or less, and particularly about 0. It becomes superhydrophilic to the extent of °. Water by photocatalysis hydroxyl (OH ^-) are chemisorbed on the surface in the form of, as a result, the surface is considered to become superhydrophilic.

Other photocatalysts that can be used include ZnO and SnO.
₂ , there are metal oxide semiconductors such as SrTiO ₃ , WO ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ . These metal oxides, like titania,
Since metal elements and oxygen exist on the surface, surface hydroxyl groups (OH
^- ) It is thought to adsorb.

The photocatalyst layer may be formed of any one of the above photocatalysts, or may be formed of a mixture thereof. In particular, when silica or tin oxide is added to the photocatalytic titania, the surface can be made highly hydrophilic.

The photocatalytic semiconductor is photoexcited by light having a wavelength having an energy equal to or higher than its band gap energy. When the photocatalyst is, for example, anatase type TiO ₂ or ZnO, it can be photoexcited with ultraviolet rays having a wavelength of 387 nm or less, and when it is rutile type TiO ₂ , it can be photoexcited with ultraviolet rays having a wavelength of 413 nm or less. As the ultraviolet light source, a fluorescent lamp, an incandescent lamp, a metal halide lamp, a mercury lamp, a fluorescent mercury lamp, and other electric lamps can be used. In order to make the surface of the photocatalyst layer superhydrophilic so that the contact angle with water becomes about 0 °,
It is preferable to irradiate ultraviolet rays with sufficient illuminance for a sufficient time. However, once the surface of the photocatalyst layer is highly hydrophilized, it is possible to sufficiently maintain superhydrophilicity even with weak ultraviolet light emitted from a fluorescent lamp or the like. Under the condition that sunlight enters the bathroom, sunlight can be used during the daytime.

When the bathroom member is formed of a heat-resistant base material such as tiles and enamel products, it is superhydrophilic enough to have a contact angle with water of 0 ° and is excellent in abrasion resistance. The preferred way to form the photocatalyst layer is to first coat the surface of the substrate with amorphous titania and then phase change the amorphous titania to crystalline titania (anatase or rutile) by firing. Any of the following methods can be used to form the amorphous titania.

(1) Hydrolysis and Dehydration Polycondensation of Organic Titanium Compounds Titanium alkoxides such as tetraethoxy titanium, tetraisopropoxy titanium, tetra n-propoxy titanium, tetrabutoxy titanium, tetramethoxy titanium, hydrochloric acid or ethyl amine. After adding such a hydrolysis inhibitor and diluting it with an alcohol such as ethanol or propanol, the mixture is spray-coated, flow-coated, while the hydrolysis is partially or completely progressed. Spin coating,
Apply dip coating, roll coating or other coating method to the surface of the substrate, and
Dry at a temperature of 0 ° C. Upon drying, the hydrolysis of titanium alkoxide is completed to produce titanium hydroxide, and dehydration polycondensation of titanium hydroxide forms an amorphous titania layer on the surface of the substrate. Instead of titanium alkoxide, other organotitanium compounds such as titanium chelate or titanium acetate may be used. (2) Formation of amorphous titania by inorganic titanium compound Spray coating, flow coating of an acidic aqueous solution of an inorganic titanium compound, for example, TiCl ₄ or Ti (SO ₄ ) ₂ ,
It is applied to the surface of a substrate by spin coating, dip coating, or roll coating. Next, the inorganic titanium compound is subjected to hydrolysis and dehydration-condensation polymerization by drying at a temperature of about 100 ° C to 200 ° C to form a layer of amorphous titania on the surface of the substrate. Alternatively, amorphous titania may be applied to the surface of the substrate by chemical vapor deposition of TiCl ₄ . (3) Formation of amorphous titania by sputtering Amorphous titania is deposited on the surface of a substrate by irradiating a target of metallic titanium with an electron beam in an oxidizing atmosphere. (4) Firing temperature The firing of amorphous titania is performed at a temperature of at least the crystallization temperature of anatase. Amorphous titania can be converted to anatase titania by firing at a temperature of 400 ° C to 500 ° C or higher. By firing at a temperature of 600 ° C to 700 ° C or higher, amorphous titania can be converted to rutile type titania.

When the bathroom member is covered with glaze such as tiles and enamel products, it is preferable to previously form an intermediate layer such as silica between the base material and the amorphous titania layer. This prevents the alkaline network modifying ions in the glaze from diffusing from the base material into the photocatalyst layer during firing of the amorphous titania, and achieves superhydrophilicity such that the contact angle with water becomes 0 °. To be done.

Another preferred method for forming a photocatalytic layer having super-hydrophilic property such that the contact angle with water is 0 ° and having excellent abrasion resistance is based on a photocatalytic coating composed of a mixture of titania and silica. It is to form on the surface of the material. The ratio of silica to the total of titania and silica can be 5 to 90 mol%, preferably 10 to 70 mol%, more preferably 10 to 50 mol%. To form a photocatalytic coating made of silica-containing titania, any one of the following methods can be adopted.

(1) A suspension containing particles of anatase-type or rutile-type titania and silica particles is applied to the surface of a base material and sintered at a temperature below the softening point of the base material. (2) Precursors of amorphous silica (for example, tetraalkoxysilanes such as tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, tetrabutoxysilane, tetramethoxysilane, etc .; silanol which is a hydrolyzate thereof); Alternatively, a mixture of a polysiloxane having an average molecular weight of 3000 or less) and crystalline titania sol is applied to the surface of the base material, and if necessary, hydrolyzed to form silanol, and then heated at a temperature of about 100 ° C. or higher to obtain silanol. Is subjected to dehydration polycondensation to form a photocatalytic coating in which titania is bound with amorphous silica.
In particular, if the dehydration condensation polymerization temperature of silanol is carried out at a temperature of about 200 ° C. or higher, the degree of polymerization of silanol can be increased and the alkali resistance performance of the photocatalytic coating can be improved. (3) Disperse silica particles in a solution of amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate, or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ). The resulting suspension is applied to the surface of the base material, and the titanium compound is subjected to hydrolysis and dehydration polycondensation at a temperature from room temperature to 200 ° C to form a thin film of amorphous titania in which silica particles are dispersed. . Then, the amorphous titania is phase-changed into crystalline titania by heating the titania to a temperature above the crystallization temperature and below the softening point of the substrate. (4) Amorphous silica precursor in a solution of amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ). Body (eg, tetraethoxysilane, tetraisopropoxysilane, tetra n
A mixture of tetraalkoxysilanes such as propoxysilane, tetrabutoxysilane, and tetramethoxysilane; silanol which is a hydrolyzate thereof; or polysiloxane having an average molecular weight of 3000 or less), and coating the mixture on the surface of the substrate. Then, these precursors are subjected to hydrolysis and dehydration polycondensation to form a thin film composed of a mixture of amorphous titania and amorphous silica. Then, the amorphous titania is phase-changed into crystalline titania by heating the titania to a temperature above the crystallization temperature and below the softening point of the substrate.

Still another preferred method of forming a photocatalytic coating having superhydrophilicity such that the contact angle with water is 0 ° and having excellent abrasion resistance is a photocatalytic property comprising a mixture of titania and tin oxide. Forming a coating on the surface of the substrate. The ratio of tin oxide to the total of titania and tin oxide is 1 to 95% by weight, preferably 1 to 50%.
It can be wt%. Any one of the following methods can be adopted to form the photocatalytic coating made of titania containing tin oxide. (1) A suspension containing particles of anatase-type or rutile-type titania and particles of tin oxide is applied to the surface of a base material and sintered at a temperature equal to or lower than the softening point of the base material. (2) Tin oxide particles in a solution of amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) The suspension obtained by dispersing is applied to the surface of the base material, and the titanium compound is subjected to hydrolysis and dehydration condensation polymerization at a temperature of from room temperature to 200 ° C., thereby forming a thin film of amorphous titania in which tin oxide particles are dispersed. Form. Then, the amorphous titania is phase-changed into crystalline titania by heating the titania to a temperature above the crystallization temperature and below the softening point of the substrate.

When the bathroom member is made of a non-heat resistant material such as plastic, it is preferable to form a photocatalyst layer exhibiting superhydrophilicity such that the contact angle with water upon photoexcitation becomes 0 °. The approach is to use a coating composition in which photocatalyst particles are dispersed in a film-forming element consisting of uncured or partially cured silicone (organopolysiloxane) or a precursor of silicone. When this coating composition is applied to the surface of a bathroom member and the coating film-forming element is cured and then the photocatalyst is photoexcited, the organic group bonded to the silicon atom of the silicone molecule is replaced with a hydroxyl group by the photocatalytic action of the photocatalyst. The surface of the photocatalyst layer is made superhydrophilic.

The coating film-forming elements of this coating composition include methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane and methyltri-t-silane.
-Butoxysilane; ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane,
Ethyltri-t-butoxysilane; n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltriisopropoxysilane, n-propyltrit-butoxysilane; n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-hexyltriisopropoxysilane, n-hexyltrit-butoxysilane; n-decyltrichlorosilane, n -Decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n-decyltriisopropoxysilane, n-decyltrit-butoxysilane; n-octadecyltrichlorosilane, n
-Octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n-
Octadecyltri-t-butoxysilane; phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltri-t-butoxysilane; tetrachlorosilane, tetrabromosilane,
Tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane; dimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxysilane; diphenyldichlorosilane, diphenyldibromosilane, diphenyldimethoxysilane, Diphenyldiethoxysilane; phenylmethyldichlorosilane, phenylmethyldibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane, tribromohydrosilane, trimethoxyhydrosilane, triethoxyhydrosilane, triisopropoxyhydrosilane, tri-t -Butoxyhydrosilane; vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyl Triethoxysilane, vinyltriisopropoxysilane, vinyltri-t-butoxysilane; trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane. , Trifluoropropyltri-t-butoxysilane;
γ-glycidoxypropylmethyldimethoxysilane, γ
-Glycidoxypropylmethyldiethoxysilane, γ-
Glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxysilane, γ-glycidoxypropyltri-t-butoxysilane; γ-methacryloxypropylmethyldimethoxysilane Γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxypropyltri t-butoxysilane; γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ
-Aminopropyltriisopropoxysilane, γ-aminopropyltri-t-butoxysilane; γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane Γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri-t-butoxysilane; β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane; And their partial hydrolysates; and mixtures thereof.

It is preferable that an antibacterial metal such as Ag, Cu, or Zn is further added to the photocatalyst layer. Ag on the photocatalyst,
To add Cu or Zn, soluble salts of these metals can be added to a suspension of photocatalytic particles and the resulting solution used to form a photocatalytic coating. Alternatively, after forming a photocatalytic coating, a soluble salt of these metals may be applied and photoreduced to be precipitated by light irradiation. The photocatalyst layer doped with Ag, Cu, or Zn exhibits antibacterial performance even when it cannot be photoexcited such as at night.

On such a highly hydrophilic surface,
It is difficult for hydrophobic contaminants such as soap residue and organic matter to adhere. Also, even if adhered, the superhydrophilized surface has a much greater affinity for water than for hydrophobic contaminants, so that when wetted with water, water will be trapped between the surface and the contaminants. Enters and releases contaminants from the surface. Therefore, when the surface of the bathroom member is exposed to water droplets or water with the use of a bath, a washing place, or a shower, contaminants are easily released from the surface and washed away with water. Thus, each time the bathroom is used, the contaminants are washed away with water, so that the surface of the photocatalyst layer is kept clean. As a result, the microorganisms such as bacteria, molds and yeasts attached to the surface of the bathroom member come into direct contact with the surface of the photocatalyst layer, and are effectively killed or grown by the photooxidation action of the photocatalyst. Be suppressed.

[0028]

Example 1 Anatase-type titania sol (Ishihara Sangyo Co., Ltd., STS-11, average particle size 0.01 μm) is a 10 cm square glazed tile.
B02E01) was applied on the surface by a spray coating method and baked at a temperature of 850 ° C. for 2 hours. Next, a 1 wt% silver nitrate aqueous solution was applied to this sample by a spray coating method, and a 4 W black light blue (BLB) fluorescent lamp (Sankyo Denki) was used to irradiate ultraviolet rays for several minutes to photodecompose silver nitrate. To deposit silver to obtain Sample A.
The contact angle of the surface of Sample A with water was 8 °.

For the sample A and for comparison, a glazed tile without a photocatalyst layer (sample B) was tested for changes in slipperiness with use and the state of adhesion of dirt. Therefore, sample A
And the sample B was installed on the floor of the public bath of the employee dormitory located in Chigasaki and observed. This public bathhouse is designed to be illuminated by fluorescent lights at normal illuminance at night.

The slipperiness was evaluated by the ratio of the maximum static friction coefficient at the time of measurement to the initial maximum static friction coefficient (maximum static friction coefficient ratio). The maximum static friction coefficient is obtained by wetting the sample surface with water, placing a weight of 0.5 kg on the sample, and applying the force in the horizontal direction to the force when the weight starts to move. ) And read it. The state of adhesion of dirt was evaluated by the ratio of the glossiness at the time of measurement to the initial glossiness (specific glossiness). The reflectance was measured using a gloss meter (Nippon Denshoku Industries Co., Ltd.) in accordance with JIS Z8741, and the specific glossiness was obtained from the change in reflectance.

The measurement results are shown in the graphs of FIGS. 1 and 2. As can be seen from these graphs, in the glazed tile without the photocatalyst layer (Sample B), the maximum static friction coefficient was reduced with use, gradually becoming slippery, and the adhesion of dirt increased. On the other hand, in the glazed tile (Sample A) provided with the photocatalyst layer, the initial maximum static friction coefficient was maintained, and the adhesion of dirt was small.

Example 2 Anatase-type titania sol (Ishihara Sangyo, STS-11) and colloidal silica sol (Nissan Kagaku, Snowtex O) were mixed at a solid content molar ratio of 88:12, and a 15 cm square glazed tile ( It was applied to the surface of Totoki Co., Ltd., AB02E01) by the spray coating method and baked at a temperature of 800 ° C. for 1 hour to obtain a sample coated with a film made of titania and silica. The thickness of the coating was 0.3 μm. The contact angle with water immediately after firing was 5 °. The contact angle with water after leaving the sample in the dark for 1 week was 5 °. 0.03 mW / cm on the surface of the sample using a BLB fluorescent lamp (Sankyo Denki, FL20BLB)
^When ultraviolet rays were irradiated for 1 day at an ultraviolet illuminance of ² , the contact angle with water became 0 °.

Example 3 Anatase type titania sol (STS-11) and colloidal silica sol (Nissan Kagaku, Snowtex 20) were mixed at a molar ratio of solid content of 80:20 to obtain a 15 cm square glazed tile (AB02E01). The sample was applied on the surface by a spray coating method and baked at a temperature of 800 ° C. for 1 hour to obtain a sample coated with a film made of titania and silica. The thickness of the coating was 0.3 μm. The contact angle with water immediately after firing was 5 °. The contact angle with water after leaving the sample for 2 weeks in the dark was 14 °. When the surface of the sample was irradiated with ultraviolet light at 0.004 mW / cm ² for 1 day using a white fluorescent lamp, the contact angle with water became 4 °. Therefore, it can be seen that even under room illumination, it is sufficiently hydrophilized.

Example 4 Tetraethoxysilane Si was added to 86 parts by weight of an ethanol solvent.
6 parts by weight of (OC ₂ H ₅ ) ₄ (Wako Pure Chemical Industries), 6 parts by weight of pure water, and 2 parts by weight of 36% hydrochloric acid as a hydrolysis inhibitor of tetraethoxysilane were added and mixed to prepare a silica coating solution. Since the solution generated heat by mixing, the mixed solution was left to cool for about 1 hour. This solution was applied to the surface of a 10 cm square soda lime glass plate by the flow coating method,
Dried at a temperature of ° C. With drying, tetraethoxysilane was hydrolyzed to silanol Si (OH) _{4 first} , and then a thin film of amorphous silica was formed on the surface of the glass plate by dehydration condensation polymerization of silanol.

Next, tetraethoxy titanium Ti (OC ₂ H ₅ )
₄ (Merck) 0.1 part by weight of 36% hydrochloric acid as a hydrolysis inhibitor was added to a mixture of 1 part by weight of ethanol and 9 parts by weight of ethanol to prepare a titania coating solution, and this solution was dried on the surface of the glass plate. It was applied by a flow coating method in air. The coating amount was 45 μg / cm ² in terms of titania. Since the rate of hydrolysis of tetraethoxytitanium was extremely fast, part of the tetraethoxytitanium was hydrolyzed at the coating stage, and titanium hydroxide Ti (OH) ₄ began to form.

Next, the glass plate is heated to about 150 minutes for 1 to 10 minutes.
By maintaining the temperature at ℃, the hydrolysis of tetraethoxytitanium was completed, and the produced titanium hydroxide was subjected to dehydration polycondensation to produce amorphous titania. Thus, a glass plate in which amorphous titania was coated on amorphous silica was obtained. The glass plate was fired at a temperature of 500 ° C. to convert amorphous titania to anatase titania.

After leaving this sample in the dark for several days, 20 W
0.5mW on the surface of the sample using the BLB fluorescent lamp (FL20BLB)
Ultraviolet rays were irradiated for about 1 hour at an ultraviolet illuminance of / cm ² to obtain a # 1 sample. For comparison, a glass plate not coated with titania was prepared and used as a # 2 sample.

The contact angle between the # 1 sample and the # 2 sample with water was measured by a contact angle measuring instrument (model CA-X150, manufactured by Kyowa Interface Science Co., Ltd.). The detection limit on the low angle side of this contact angle measuring instrument was 1 °. The contact angle was measured 30 seconds after a water droplet was dropped from the microsyringe on the sample surface. The reading of the measuring instrument with respect to water on the surface of the # 1 sample was 0 °, indicating superhydrophilicity. On the other hand, the contact angle of the # 2 sample with water was 30 to 40 °.

Applying oleic acid to the surface of # 1 sample,
When the glass plate was immersed in water filled in a water tank while keeping the glass plate surface in a horizontal position, the oleic acid curled into oil droplets, which were released from the surface of the glass plate and floated.

Example 5 In this example, a 10 cm square aluminum substrate was used as a base material. In order to smooth the surface of the substrate, it was previously coated with a silicone layer. For this reason, liquid A (silica sol) and liquid B (trimethoxymethylsilane) of the Japanese synthetic rubber coating composition "GLASCA" are mixed so that the weight ratio of liquid A and liquid B is 3: 1. This mixed solution was applied to an aluminum substrate and cured at a temperature of 150 ° C. to obtain a plurality of aluminum substrates (# 1 sample) coated with a base coat of silicone having a thickness of 3 μm.

The # 1 sample was then coated with the titania-containing paint. More specifically, anatase-type titania sol (NISSAN CHEMICAL, TA-15) is mixed with the above-mentioned "grasca" solution A (silica sol), diluted with ethanol, and then the above-mentioned "grasca" solution B is added to the titania-containing paint. A composition for use was prepared. The composition of this coating composition was 39 parts by weight of silica, 97 parts by weight of trimethoxymethylsilane, and 8 parts of titania.
It was 7 parts by weight. This coating composition was applied to the surface of a # 1 sample and cured at a temperature of 150 ° C. to form a top coat in which anatase-type titania particles were dispersed in a silicone coating, to obtain a # 2 sample.

Next, using the BLB fluorescent lamp for the # 2 sample, 0.5.
Ultraviolet rays were irradiated for 5 days at an illuminance of mW / cm ² to obtain a # 3 sample. The contact angle of the surface of this sample with water is measured by a contact angle measuring device (ER
The contact angle reading was less than 3 ° when measured by MA). The contact angle of the # 2 sample before ultraviolet irradiation was measured and was found to be 70 °. When the contact angle of the # 1 sample was measured, it was 90 °. Further, the # 1 sample was irradiated with ultraviolet rays for 5 days under the same conditions as the # 2 sample, and the contact angle was measured. As a result, the contact angle was 85 °.

From this, it can be seen that the silicone coating film is highly hydrophilized when the photocatalyst is photoexcited by incorporating the photocatalyst into the silicone. It is considered that the organic group bonded to the silicon atom of the silicone molecule is substituted with the hydroxyl group by the photocatalytic action, and the hydrophilic silicone derivative is formed on the surface.

Example 6 In this example, an acrylic resin plate was used as the base material.
In order to prevent the acrylic resin plate from being deteriorated by the photocatalyst, the surface of the acrylic resin plate was previously coated with a silicone layer. Therefore, in the same manner as in Example 5, solutions A and B of "Glaska" were mixed to prepare a coating solution. This coating liquid is applied on the surface of a 10 cm square acrylic resin plate and cured at a temperature of 100 ° C. to a film thickness of 5 μm.
A plurality of acrylic resin plates (# 1) coated with the above silicone base coat were obtained.

Next, anatase-type titania sol (Nissan Kagaku, TA-15) and the above-mentioned "grasca" solution A were mixed, diluted with ethanol, and then "grasca" solution B was added to give four different compositions. The coating liquid of was prepared. The compositions of these coating solutions were adjusted such that the ratio of the weight of titania to the sum of the weight of titania, the weight of silica, and the weight of trimethoxymethylsilane was 5%, 10%, 50%, and 80%, respectively. Apply each coating solution to the acrylic resin plate coated with silicone layer,
Curing at a temperature of 2 to form a top coat in which anatase-type titania particles are dispersed in a silicone coating film.
A # 5 sample was obtained. BLB fluorescent lamp 0.5mW for # 1 to # 5 samples
The contact angle with water on the surface of these samples was measured with a contact angle measuring instrument (made by ERMA) at different time intervals while irradiating with UV light for up to 200 hours at an illuminance of / cm ² , and the contact angle changed with time. Was observed. The results are shown in the graph of FIG.

As can be seen from the graph of FIG. 3, the # 1 sample without the titania-containing layer shows almost no change in the contact angle with water even when it is irradiated with ultraviolet rays. On the other hand, it can be seen that the # 2 to # 5 samples provided with the titania-containing top coat are hydrophilized until the contact angle with water becomes less than 10 ° in response to ultraviolet irradiation. In particular, in the samples # 3 to # 5 in which the ratio of titania is 10% by weight or more, the contact angle with water is 3 ° or less. Furthermore, the titania content is 50% by weight and 80% by weight, respectively.
It is noted that the contact angle with water of the 4 sample and the # 5 sample becomes 3 ° or less by the short-time ultraviolet irradiation. # 4 After leaving the sample in the dark for 2 weeks, contact angle measuring device (CA-X15
When the contact angle with water was measured according to 0), the contact angle with water was 3 ° or less.

[0047]

According to the method of the present invention, the surface of the photocatalyst layer of the bathroom member is highly hydrophilized by the hydrophilizing action of the photocatalyst, so that soap residue and organic matter are used every time when bathing, washing place or showering. The surface of the photocatalyst layer is washed away from the surface and is always kept clean. Therefore, the microorganisms such as bacteria, molds and yeasts attached to the surface of the bathroom member come into direct contact with the photocatalyst, and the photooxidation of the photocatalyst effectively kills or suppresses the growth. . Therefore, it is possible to prevent the occurrence of "slimming" on the surface of the bathroom member without requiring special maintenance.

[Brief description of drawings]

FIG. 1 is a graph showing the test results of Example 1.

FIG. 2 is a graph showing the test results of Example 1.

FIG. 3 is a graph showing the test results of Example 6.

Claims (5)

[Claims] 1. A surface of a bathroom member is coated with a layer containing a semiconductor photocatalyst, and the photocatalyst is photoexcited to hydrophilize the surface of the layer to about 10 ° or less in terms of a contact angle with water. The photocatalyst is activated, and the surface of the layer is exposed to water droplets or wet to wash away the contaminants adhering to the surface of the layer and the bacteria and microorganisms adhering to the surface of the layer of the photocatalyst. A method for cleaning a bathroom member, which is characterized by killing or suppressing its growth by a photooxidation effect. 2. The surface of the bathroom member is coated with a layer containing a semiconductor photocatalyst and an antibacterial metal, and the photocatalyst is photoexcited to convert the surface of the layer into a contact angle with water of about 10 ° or less. The photocatalyst is activated together with hydrophilicity, and the surface of the layer is exposed to water droplets or wet to wash away the contaminants adhering to the surface of the layer, and bacteria attached to the surface of the layer. A method for cleaning a bathroom member, which comprises killing microorganisms by an antibacterial action of an antibacterial metal or suppressing the growth thereof. 3. The method according to claim 1, wherein the surface of the layer exhibits hydrophilicity of about 5 ° or less in terms of contact angle with water by photoexcitation of a photocatalyst. 4. The method according to claim 1, wherein the layer comprises a mixture of photocatalytic titania and silica or tin oxide. 5. The layer is made of silicone having photocatalyst particles dispersed therein, and an organic group bonded to a silicon atom of a silicone molecule on the surface of the layer is at least partially substituted with a hydroxyl group due to photoexcitation of the photocatalyst. Method according to any one of claims 1 to 3, characterized in that