JP3465664B2 - Building materials for exterior walls - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a building material for outer walls that can be self-cleaned (self-cleaning) by rainfall, and a building material for outer walls that can be easily cleaned by washing with water.

[0002]

2. Description of the Related Art The outer wall of a high-rise building, for example, contains combustion products such as dust and exhaust gas contained in the air, dirt eluted from an upper sealant, and pollutants discharged from the exhaust port of the building. Stain with hydrophobic stains. These hydrophobic stains are dark black and significantly impair the aesthetics of the building. further,
If the outer wall of a high-rise building is to be cleaned, the cleaning is a work at a high place, is a heavy labor, and is dangerous at the same time.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a building material for outer wall which can be cleaned by rainfall or washing with water.

[0004]

The present invention is based on the finding that in a member having a surface layer containing a photocatalyst, when the photocatalyst is photoexcited, the surface of the member is highly hydrophilized. This phenomenon is considered to proceed by the mechanism shown below. That is, when the photocatalyst is irradiated with light having an energy larger than the energy gap between the valence band upper end and the conduction band lower end of the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. The action of either or both of them probably imparts polarity to the surface and collects polar components such as water and hydroxyl groups. And, by the cooperative action of one or both of conduction electrons and holes and the polar component, the chemical bond between the surface and the contaminant chemically adsorbed on the surface is cut off, and the chemisorbed water is adsorbed on the surface. Are adsorbed, and a physically adsorbed water layer is further formed thereon. Further, once the surface of the member has been made highly hydrophilic, the hydrophilicity of the surface continues for a certain period even if the member is kept in a dark place.

The present invention provides a self-cleaning outer wall building material comprising a surface layer containing substantially transparent photocatalytic oxide particles on the surface of the outer wall building material substrate. By providing a surface layer containing photocatalytic oxide particles,
In response to the photoexcitation of the photocatalyst, the surface of the surface layer becomes hydrophilic, and when the outer wall building material surface is exposed to rainfall, the adhered deposits and / or contaminants are washed away by raindrops.

The present invention provides an easily-cleanable outer wall building material, which comprises a surface layer containing substantially transparent photocatalytic oxide particles on the surface of the outer wall building material substrate. By providing a surface layer containing photocatalytic oxide particles, the surface of the surface layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst, and the surface of the building material for outer walls becomes easy to wash with water and rinsed with water. It can be cleaned with a simple water wipe.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a specific structure of the present invention will be described. As shown in FIG. 1 or FIG. 2, on the surface of the building material for outer wall in the present invention, a photocatalyst (crystal) is formed on the surface of the base material.
A layer containing a conductive oxide or the like is formed. By taking such a surface structure, the surface of the building material for outer walls is highly hydrophilized according to the photoexcitation of a photocatalyst. Thereby,
The rain drops wash away the deposits and / or contaminants adhering to the surface of the surface layer. Furthermore, when the surface structure is provided on the surface of the building material for outer walls, the deposits and / or contaminants adhering to the surface of the surface layer can be easily washed with water, and if the sunny day continues. However, it can be cleaned by rinsing with water or sprinkling water.

In FIG. 1, the surface layer consists only of photocatalytic oxide particles. In this case, since the photocatalyst is made of an oxide, the oxide shows hydrophilicity in a state where the pollutant in the environment is not adsorbed, so that the photoexcited action is to eliminate the pollutant to form an adsorbed water layer. Thus, it is easy to exhibit hydrophilicity and a uniform water film can be formed. In FIG. 2, M represents a metal element. Therefore, in the case of FIG. 2, the outermost surface is made of a general inorganic oxide. Also in this case, since the oxide shows hydrophilicity in the state where the pollutant in the environment is not adsorbed, the pollutant is excluded by the photoexcitation action of the photocatalytic oxide mixed in the surface layer in addition to the above inorganic oxide. By forming the adsorbed water layer, a uniform water film can be formed.

The building material substrate for outer wall to which the present invention can be applied includes
Glazed tile, unglaze tile, brick, crystallized glass, glass block, concrete, stone, wood; lightweight cellular concrete board, asbestos cement calcium silicate board, precast reinforced concrete board, asbestos slate board, pulp cement board, gypsum board board, etc. Acrylic resin, urethane resin, polyester, silicone,
Decorative inorganic building materials coated with resin paints such as fluororesin and acrylic silicone resin; acrylic resin, urethane resin, on the surface layer of metal base materials such as aluminum, stainless steel, and steel.
A coated steel plate coated with a resin paint such as polyester, silicone, fluororesin, and acrylic silicone resin; a plastic plate such as an acrylic plate or a polycarbonate plate, or a coated product thereof can be preferably used.

The photocatalyst means an electron in the valence band when irradiated with light (excitation light) having an energy (that is, a short wavelength) larger than the energy gap between the conduction band and the valence band of the crystal. Excitation (photoexcitation) refers to a substance capable of generating conduction electrons and holes, and the photocatalytic titanium oxide refers to crystalline titanium oxide such as anatase type titanium oxide and rutile type titanium oxide. Here, sunlight can be preferably used as a light source used for photoexcitation of the photocatalyst. In order to make the surface of the base material highly hydrophilic by photoexcitation of the photocatalyst, the illuminance of the excitation light is 0.001 mW / cm.
^It may be ² or more, but 0.01 mW / cm ² or more is preferable, and 0.1 mW / cm ² or more is more preferable.

The thickness of the surface layer containing the photocatalytic titanium oxide is preferably 0.4 μm or less. Then, white turbidity due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. Furthermore, it is more preferable that the thickness of the surface layer containing the photocatalytic titanium oxide be 0.2 μm or less. By doing so, it is possible to prevent coloration of the surface layer due to light interference. Also, the thinner the surface layer, the higher its transparency. Furthermore, if the film thickness is reduced, the wear resistance of the surface layer is improved. The surface of the surface layer may be further provided with a wear-resistant or corrosion-resistant protective layer which can be made hydrophilic and other functional films.

The surface layer preferably has a refractive index that is not so high as that of the substrate. The refractive index of the surface layer is preferably 2 or less. Then, reflection of light at the interface between the substrate and the surface layer and the interface between the surface layer and the air can be suppressed. To reduce the refractive index of the surface layer to 2 or less, another substance having a refractive index of 2 or less is added to the photocatalytic titanium oxide. Here, as another substance having a refractive index of 2 or less,
For example, calcium carbonate (refractive index 1.6), calcium hydroxide (refractive index 1.6), magnesium carbonate (refractive index 1.5), strontium carbonate (refractive index 1.5), dolomite (refractive index 1.7). ), Calcium fluoride (refractive index 1.4), magnesium fluoride (refractive index 1.4), silica (refractive index 1.5), alumina (refractive index 1.6), silica sand (refractive index 1.6). ), Montmorillonite (refractive index 1.
5), kaolin (refractive index 1.6), sericite (refractive index 1.6), zeolite (refractive index 1.5), tin oxide (refractive index 1.9) and the like can be added to the surface layer.

Metals such as Ag, Cu and Zn can be added to the surface layer. The metal-added surface layer can kill bacteria and mold attached to the surface even in a dark place.

The surface layer includes Pt, Pd, Ru and R.
Platinum group metals such as h, Ir, Os can be added. The surface layer to which the metal is added can enhance the redox activity of the photocatalyst and improve the deodorizing purification action and the like. Further, when a solid acid other than the photocatalyst is added, the acidity of the solid acid is improved by the addition of the platinum group metal, so that the hydrophilicity maintenance property is also improved, and the water film of the adhered water is further promoted to some extent. The hydrophilicity maintaining property when the photocatalyst is not irradiated with the excitation light for a long time is also improved. Mo may be added to the surface layer. Also in this case, since the acidity of the solid acid is improved by the addition, the hydrophilicity-maintaining property is also improved, and the formation of a water film of the attached water is further promoted, and the hydrophilicity-maintaining property when the photocatalyst is not irradiated with the excitation light for a certain period of time. Also improves.

When the substrate is a glass containing an alkali network modifying ion such as sodium (soda lime glass, parallel plate glass, etc.), an intermediate layer such as silica may be formed between the substrate and the surface layer. Good. Then, the alkali network modifying ions are prevented from diffusing from the base material to the surface layer during firing, and the photocatalytic function is better exhibited.

[0016] The hydrophilic property means a property of easily fitting when water is dripped on the surface, and generally means a state where the water wetting angle is less than 90 °. The high degree of hydrophilicity in the present invention refers to the property of being very easily blended when water is dropped on the surface, and more specifically, a state in which the water wetting angle is about 10 ° or less. In particular, as disclosed in PCT / JP96 / 00734, the antifogging property is preferably such that the water wetting angle is 10 ° or less, more preferably 5 ° or less.

The solid acid in the present invention includes sulfuric acid carrying Al.
₂ O ₃ , sulfuric acid-supporting TiO ₂ , sulfuric acid-supporting ZrO ₂ , sulfuric acid-supporting S
nO ₂ , Fe ₂ O ₃ supporting sulfuric acid, SiO ₂ supporting sulfuric acid, HfO ₂ supporting sulfuric acid, TiO ₂ / WO ₃ , WO ₃ / SnO ₂ , WO ₃ / Z
rO ₂ , WO ₃ / Fe ₂ O ₃ , SiO ₂ · Al ₂ O ₃ , TiO ₂
/ SiO ₂ , TiO ₂ / Al ₂ O ₃ , TiO ₂ / ZrO _{2 and the} like can be preferably used.

Next, a method of forming the surface layer will be described. First, the production method in the case where the surface layer is composed only of the photocatalytic oxide will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, there are roughly three methods. One method is a sol coating firing method, another method is an organic titanate method, and another method is an electron beam evaporation method. (1) Sol coating firing method Anatase type titanium oxide sol
The surface of the base material is applied by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method, or a roll coating method, and then baked. (2) Organic titanate method Titanium alkoxide (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelate, etc. are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.). , After diluting with a non-aqueous solvent such as alcohol (ethanol, propanol, butanol, etc.), while partially or completely proceeding the hydrolysis, the mixture is spray-coated, dip-coated, It is applied by a method such as a flow coating method, a spin coating method or a roll coating method, and dried. Drying completes the hydrolysis of the organic titanate to produce titanium hydroxide,
A layer of amorphous titanium oxide is formed on the surface of the substrate by dehydration polycondensation of titanium hydroxide. Then, it is baked at a temperature equal to or higher than the crystallization temperature of anatase to transform the amorphous titanium oxide into anatase-type titanium oxide. (3) Electron beam evaporation method A target of titanium oxide is irradiated with an electron beam to form a layer of amorphous titanium oxide on the surface of the base material. Then, it is baked at a temperature equal to or higher than the crystallization temperature of anatase to transform the amorphous titanium oxide into anatase-type titanium oxide.

Next, the case where the surface layer is composed of a photocatalytic oxide and silica will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, there are the following three methods, for example. One is the sol coating firing method, the other is the organic titanate method, and the other is the tetrafunctional silane method. (1) Sol coating firing method A mixed solution of anatase type titanium oxide sol and silica sol is applied to the surface of a substrate by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method, a roll coating method, etc. and baked. To do. (2) Organic titanate method Titanium alkoxides (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelates and other organic titanates are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.) and silica sol. Add alcohol (ethanol, propanol, butanol, etc.)
After diluting with a non-aqueous solvent such as, while partially proceeding the hydrolysis or after proceeding the hydrolysis completely, the mixture is spray-coated, dip-coated,
It is applied by a method such as a flow coating method, a spin coating method or a roll coating method, and dried. Drying completes the hydrolysis of the organic titanate to produce titanium hydroxide, and a dehydration condensation polymerization of titanium hydroxide forms an amorphous titanium oxide layer on the surface of the substrate. Then, it is baked at a temperature equal to or higher than the crystallization temperature of anatase to transform the amorphous titanium oxide into anatase-type titanium oxide. (3) Tetrafunctional silane method A mixture of tetraalkoxysilane (tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetramethoxysilane, etc.) and anatase type titanium oxide sol is spray-coated or dip-coated on the surface of a substrate. , A flow coating method, a spin coating method, a roll coating method and the like, and if necessary, hydrolyzed to form silanol, and then silanol is subjected to dehydration polycondensation by a method such as heating.

Next, the case where the surface layer is composed of a photocatalytic oxide and a solid acid will be described by taking as an example the case where the photocatalyst is anatase type titanium oxide and the solid acid is TiO2 / WO3. The method in this case is to mix an ammonia solution of tungstic acid with an anatase type titanium oxide sol and, if necessary, dilute the mixture with a diluent (water, ethanol, etc.) on the surface of the substrate by spray coating or dip coating. Method, flow coating method, spin coating method, roll coating method, etc., and baking. Other methods include electron beam evaporation and hydrolysis and dehydration polycondensation of organic titanates such as titanium alkoxide, titanium acetate, and titanium chelate to form an amorphous titanium oxide film, then apply tungstic acid, and then form amorphous titanium oxide. Heat treatment is performed at a temperature at which titanium oxide is crystallized and a TiO ₂ / WO ₃ composite oxide is formed.

Next, the case where the surface layer is composed of a photocatalytic oxide and silicone will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. The method in this case is to mix a coating composed of uncured or partially cured silicone or a precursor of silicone and anatase type titanium oxide sol, and hydrolyze the precursor of silicone as needed, and then mix the mixture. Is applied to the surface of the substrate by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method and a roll coating method, and the hydrolyzate of the silicone precursor is dehydrated and polycondensed by a method such as heating. Then, a surface layer composed of anatase type titanium oxide particles and silicone is formed. The formed surface layer, by photoexcitation of anatase type titanium oxide by irradiation with light including ultraviolet rays, at least a part of the organic group bonded to the silicon atom in the silicone molecule is substituted with a hydroxyl group, and further on it. A physically adsorbed water layer is formed and exhibits a high degree of hydrophilicity. Here, the precursor of silicone includes methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltributoxysilane, ethyltripropoxysilane, and phenyl. Trimethoxysilane,
Phenyltriethoxysilane, phenyltributoxysilane, phenyltripropoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, dimethyldipropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldibutoxysilane, diethyldi Propoxysilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, phenylmethyldibutoxysilane, phenylmethyldipropoxysilane, γ-glycidoxypropyltrimethoxysilane, and their hydrolysates and their mixtures are preferably used. it can.

In addition, a film coated with the above coating may be attached to the surface of the substrate with a transparent adhesive such as soapy water. Here, a plastic film such as polyethylene terephthalate, polyester, or polyethylene can be preferably used as the film substrate.

[0023]

EXAMPLES Example 1. Anatase type titanium oxide sol (Nissan Chemical, TA-15, solid content 15% by weight, nitric acid peptization type,
16 parts by weight of pH = 1 and silica sol (Japan Synthetic Rubber,
Glasca A liquid, solid content 13% by weight, pH = 4) 9 parts by weight were mixed, and then methyltrimethoxysilane (Japan Synthetic Rubber,
3 parts by weight of Glasca B solution) and 452 parts by weight of ethanol were added, the mixture was further stirred for 2 hours, and methyltrimethoxysilane was partially subjected to a hydrolysis reaction and a dehydration polycondensation reaction to prepare a coating solution. This coating solution was applied by flow coating to a decorative inorganic building material (Daiken Kogyo, Cerastar, WK1002-113, ivory white, plate thickness 4 mm; after adjusting the surface of the autoclaved cement calcium silicate plate, the silicone resin-based material was used. After being applied to the surface of the decorative inorganic building material to which the coloring paint was applied, it was heated at 150 ° C. for 30 minutes. Then, the surface coated with the coating solution was irradiated with ultraviolet rays for about 3 days at an ultraviolet illuminance of 0.5 mW / cm ² using an ultraviolet light source ((Sankyo Denki, Black Light Blue (BLB) fluorescent lamp), # 1. Samples were obtained.For comparison, a decorative inorganic building material (Taken Kogyo, Cerastar, WK1002-113, ivory white, plate thickness 4 mm) # 2 sample was also prepared. The contact angle with water was measured by using a contact angle measuring instrument (Kyowa Interface Science, CA-X150), and the contact angle with water 30 seconds after dropping was evaluated. As a result, the # 2 sample showed a high contact angle with water of 90 °, whereas the # 1 sample showed a high contact angle of 0 ° with water, indicating a high degree of hydrophilicity.

Next, the # 1 sample and the # 2 sample were installed outdoors and examined for self-cleaning property by rain.
The self-cleaning property by rainfall was tested as follows. That is, the outdoor stain acceleration test device shown in FIGS. 3 and 4 was installed on the roof of a building located in Chigasaki City. With reference to FIGS. 3 and 4, the apparatus includes an inclined sample support surface 22 supported by a frame 20 for mounting a sample 24. A roof 26 that is inclined forward is fixed to the top of the frame. The roof is made of a corrugated plastic plate, and the collected rain flows down in a streak on the surface of the sample 24 attached to the sample support surface 22. On the sample support surface 22 of this device, # 1 sample and # 2 sample
The sample was attached and exposed to weather conditions for one month from June 12, 1995. During the rainy season, it rained frequently. Observed after 1 month, no photocatalyst coating #
In the two samples, vertical stripe-like stains were remarkably observed on the surface of the samples. In contrast, no stain was observed in the # 1 sample with the photocatalytic coating. The state was examined by the change in color difference of the most contaminated part before and after mounting the acceleration test device. Here, the color difference was examined by using a color difference meter (Tokyo Denshoku Co., Ltd.) according to Japanese Industrial Standard (JIS) H0201 and using ΔE * display. As a result, in the # 2 sample without the photocatalytic coating, the color difference change was as large as 7.2, and the stain was remarkable, while
In the # 1 sample having the photocatalytic coating, the change in color difference was 0.8, which was very small.

Example 2. 0.69 g of tetraethoxysilane (Wako Pure Chemical Industries), 1.07 g of anatase type titanium oxide sol (TA-15, average particle size 10 nm), 29.88 g of ethanol, and 0.36 g of pure water are mixed to form a coating liquid. Was prepared. This coating liquid was applied on a 5 × 10 cm square crystallized glass substrate by a flow coating method. This crystallized glass plate for about 20 minutes about 1
By maintaining the temperature at 50 ° C., tetraethoxysilane was subjected to hydrolysis and dehydration polycondensation, and a coating in which anatase type titanium oxide particles were bound with amorphous silica was formed on the surface of the crystallized glass plate. The weight ratio of titanium oxide and silica in this coating was 1. After leaving this crystallized glass plate in the dark for a few days, it was exposed to an ultraviolet light source (Sankyo Denki, Black Light Blue (BLB) fluorescent lamp).
Was used to irradiate the surface of the sample with ultraviolet light having an ultraviolet illuminance of 0.5 mW / cm ² for about 1 hour to obtain a # 3 sample. For comparison, a # 4 sample in which a 10 cm square crystallized glass plate was left in the dark for several days was also prepared. First, water drops were dropped on the # 3 sample and the # 4 sample, and the state after the drop was observed and the contact angle with water was measured. Here, the contact angle with water was evaluated by using a contact angle measuring device (Kyowa Interface Science, CA-X150) and the contact angle with water 30 seconds after dropping. As a result, it was observed that when water droplets were dropped from the microsyringe on the sample surface of the # 3 sample, the water droplets spread uniformly on the sample surface in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the case of the # 4 sample, when a water droplet was dropped from the microsyringe on the surface of the sample, the water droplet adapted to the surface but did not reach a uniform water film shape. The contact angle with water after 30 seconds was 30 °.

Next, 1 part by weight of hydrophobic carbon black,
A slurry was prepared by suspending a powder mixture consisting of 1 part by weight of hydrophilic carbon black in water at a concentration of 1.05 g / liter. 150 ml of the above slurry was made to flow down on a # 1 sample inclined at 45 degrees and dried for 15 minutes, then 150 ml of distilled water was made to flow down and dried for 15 minutes, and this cycle was repeated 25 times. The change in color difference before and after the test was measured using a color difference meter (Tokyo Denshoku). The color difference was evaluated according to Japanese Industrial Standard (JIS) H0201 using ΔE * display. As a result, the color difference change of the # 1 sample before and after the test was 0.
There was almost no change from 6.

Example 3. Ammonia peptization anatase type titanium oxide sol (Ishihara Sangyo, STS-11) 1g and 2g
Tungstic acid dissolved in 25% aqueous ammonia was mixed, and 2 g of distilled water was further added so that the molar ratio of titanium oxide particles to tungstic acid in the coating liquid was 10: 1. Next, a 5 × 10 cm square glazed tile plate (TO02, AB02E11) was coated with the above coating solution and baked at a temperature of 700 ° C. for 30 minutes to form anatase type titanium oxide and TiO ₂ / WO _3. Five samples were obtained. No color development was observed due to the surface layer.
Next, after leaving this # 5 sample in the dark for several days,
The surface of the sample was irradiated with ultraviolet rays for about 1 hour using a fluorescent lamp at an ultraviolet illuminance of 0.5 mW / cm ² to obtain a # 6 sample. For comparison, 5 × 10 cm square glazed tile board (Totoki Equipment,
A # 7 sample was also prepared in which AB02E11) was left in the dark for several days. First, water drops were dropped on the # 6 sample and the # 7 sample, and the state after the drop was observed and the contact angle with water was measured. As a result, when the # 6 sample was dropped from the microsyringe onto the sample surface, it was observed that the water droplet spreads uniformly on the sample surface in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the # 7 sample, when a water droplet was dropped from the microsyringe on the surface of the sample, the water droplet adapted to the surface, but did not reach a uniform water film shape. The contact angle with water after 30 seconds was 30 °. Further, the # 6 sample was left in the dark for 2 days to obtain the # 8 sample. Then, with respect to the # 8 sample, the contact angle with water was similarly measured with a contact angle measuring device. As a result, when water droplets were dropped onto the sample surface of the # 8 sample from the microsyringe, it was observed that the water droplets spread uniformly on the sample surface in the form of a water film, similarly to the # 6 sample.
The contact angle with water was maintained at about 1 °.

Next, oleic acid was applied to the surface of the # 8 sample, and each sample was immersed in water filled in a water tank while keeping the sample surface in a horizontal posture. As a result, the oleic acid became round and separated from the surface by light rubbing.

Next, 1 part by weight of hydrophobic carbon black,
A slurry was prepared by suspending a powder mixture consisting of 1 part by weight of hydrophilic carbon black in water at a concentration of 1.05 g / liter. 150 ml of the above slurry was made to flow down on a # 8 sample inclined at 45 degrees and dried for 15 minutes, then 150 ml of distilled water was made to flow down and dried for 15 minutes, and this cycle was repeated 25 times. The change in color difference before and after the test was measured using a color difference meter (Tokyo Denshoku). The color difference was evaluated according to Japanese Industrial Standard (JIS) H0201 using ΔE * display. As a result, the change in color difference of the # 8 sample before and after the test was 0.
There was almost no change from 4.

[0030]

According to the present invention, the surface of the building material for outer walls is provided with a surface layer containing substantially transparent photocatalytic oxide particles, whereby the surface of the surface layer is hydrophilic in response to photoexcitation of the photocatalyst. Present. As a result, the surface of the surface layer is self-cleaned by the rainfall. Furthermore, the surface of the surface layer is cleaned only by rinsing with water or sprinkling water.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface structure of a building material for outer wall according to the present invention.

FIG. 2 is a view showing another surface structure of the building material for outer wall according to the present invention.

FIG. 3 is a front view of an outdoor stain acceleration test apparatus according to an embodiment of the present invention.

FIG. 4 is a side view of an outdoor dirt acceleration test apparatus according to an embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09D 5/00 C09D 5/00 L (56) References JP-A-6-278241 (JP, A) JP-A-7-171408 ( JP, A) JP 8-302856 (JP, A) JP 9-173783 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) E04F 13 / 08-13 / 18 B01J 21/06 B01J 35/02 C09D 1/00 C09D 5/00 E04B 1/62-1/99

Claims (3)

(57) [Claims] 1. A surface layer containing photocatalytic oxide particles is provided on the surface of a building material substrate for outer walls, said surface layer forming a layer of amorphous titanium oxide on the surface of said substrate, and thereafter crystallization of anatase. It can be produced by firing at the above temperature to cause phase transition of amorphous titanium oxide to anatase type titanium oxide, and is converted into a contact angle with water in response to photoexcitation of the photocatalytic oxide particles. And exhibits hydrophilicity of 10 ° or less, and when the surface of the building material for the outer wall is exposed to rainfall, deposited deposits or contaminants are washed away by raindrops or can be easily washed with water. Building material for outer walls. 2. The building material for outer wall according to claim 1, wherein the layer of amorphous titanium oxide can be produced by an organic titanate method or an electron beam evaporation method. 3. The amorphous titanium oxide layer is partially hydrolyzed after adding a hydrolysis inhibitor to an organic titanate such as titanium alkoxide, titanium acetate or titanium chelate and diluting it with a non-aqueous solvent such as alcohol. While proceeding with the hydrolysis, or after proceeding with the hydrolysis completely, these are spray-coated, dip-coated,
The building material for outer wall according to claim 1, which can be produced by applying by a flow coating method, a spin coating method, a roll coating method or the like and drying.