Multifunctional material having photocatalytic function and its production

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a multifunctional material in which a photocatalytic thin film is formed on the surface to add an antibacterial function or a deodorant function.

【0002】

[Previous technology]

It has recently been proposed to add an antibacterial function or a deodorant function by applying a photocatalyst to the surface of a base material. For example, there are Japanese Patent Publication No. 5-50294 and JP-A-6-65012 in the literature in which an antibacterial function is added by applying a photocatalyst on the surface of a base material. Japanese Patent Publication No. 5-50294 discloses a sterilization reactor characterized by having a photosterile filler formed by immobilizing photosemiconductor fine particles on the surface of a substrate. Further, Japanese Patent Application Laid-Open No. 6-65012 discloses antibacterial and antifungal ceramics characterized in that a substrate is coated with a titanium oxide film containing at least one metal ion selected from silver, copper, zinc and platinum. ing.

【0003】

There is a special fair 4-46609 in the literature in which a deodorizing function is added by applying a photocatalyst to the surface of a base material. Tokusho 4-46609 is a method of purifying the odor of the vehicle interior by decomposing or modifying the malodorous substance contained in the odor of the vehicle interior air, and is a solid photocatalyst of a semiconductor in which a metal or a metal oxide is supported on the semiconductor. Purification of vehicle interior odor, which is characterized by decomposing or modifying malodorous substances contained in the odor in the air by a photochemical reaction by irradiating the photocatalyst with light and bringing the photocatalyst into contact with the vehicle interior air to be purified. The method is disclosed.

【0004】

However, when a base material coated with a photocatalyst on the surface of the base material is used in an environment such as sewage or an outer wall, dirt easily adheres due to polymers, dust, fungi, etc. contained in the air or water, and the dirt becomes dirty. Depending on the type, the photocatalytic function may be reduced due to the adhesion of the dirt. There is a special fair 6-7905 as a countermeasure against the deterioration of the photocatalytic function due to the adhesion of dirt in the past. In Tokusho 6-7905, the photocatalyst layer or heating element is composed of a photocatalyst layer made of a semiconductor, an ultraviolet lamp and a heating element provided opposite to the photocatalyst layer, and a blower so that the entire photocatalyst layer is heated in sequence. A photocatalyst-based deodorizing device in which a photocatalyst layer and a heating element move is disclosed, and by heating to around 400 ° C, stains due to polymers, dust, etc. are removed, and the photocatalyst layer is regenerated.

【0005】

PROBLEM TO BE SOLVED: To solve a problem of the invention.

However, it is practically difficult to do this for the members used in the equipment installed in the room by the method by regenerating the photocatalyst. Therefore, a fundamental solution is desired rather than removing the photocatalyst layer after the dirt has adhered to the photocatalyst layer, rather than preventing the dirt from adhering to the photocatalyst layer or deteriorating the photocatalyst function due to the adhesion of the dirt.

【0006】

Therefore, in the present invention, in a member having a photocatalyst thin film formed on the surface and having an antibacterial function or a deodorant function, a photocatalyst thin film structure capable of preventing dirt from adhering to the member and preventing functional deterioration due to the dirt has been found. Based on the findings, it was an object of the present invention to provide a member having antibacterial or deodorant properties, which is resistant to stains and can prevent functional deterioration due to stains.

【0007】

[Means for solving problems]

In the present invention, in order to solve the above problems, a layer having a photocatalytic function is formed on the surface of the base material, and the gaps formed on the surface of the layer are filled with particles smaller than the gaps. The gist is a multifunctional material that has.

【0008】

It will be described in detail below. Here, the material of the base material may be basically anything such as ceramics, ceramics, metals, glass, thermosetting resins, thermoplastic resins, or composites thereof. The shape of the base material may be any shape, and it may be a simple shape such as a spherical object, a tile, a wall material, a plate-like material such as a flooring material, or a complicated shape such as a sanitary ware, a wash basin, or a bathtub. Absent. The surface of the base material may be a part or the entire surface of the base material.

【0009】

The layer having a photocatalytic function is a layer mainly composed of particles having a photocatalytic function. Particles having a photocatalytic function are required to have a degree of photoactivity having a deodorizing function or an antibacterial function, that is, a degree capable of generating active oxygen. For that purpose, it is necessary to compose a substance whose conduction band position is above the hydrogen evolution potential when represented by a band model, and the upper end of the valence band is below the oxygen evolution potential. Substances satisfying this condition include TiO2, SrTiO3, ZnO, SiC, GaP, CdS, CdSe, MoS3 and the like. In addition, since the position of the conduction band shifts upward when atomized, SnO2, WO3, Fe2O3, Bi2O3, etc. may also generate active oxygen if the layer can be composed of fine particles of about 1 to 10 nm. Of these, TiO2, SrTiO3, ZnO, SnO2, WO3, Fe2O3, and Bi2O3 are preferable because they can be fired in the atmosphere. Hereinafter, these metal compounds are referred to as photocatalysts. The photocatalytic particles are preferably 0.1 μm or less rather than 0.5 μm or less in order to have sufficient photoactivity.

【0010】

Here, the step of forming a layer having a photocatalytic function on the surface of the base material is basically carried out by applying the starting material of the photocatalyst or a material subjected to an appropriate treatment thereof to the surface of the base material. As a starting material, a photocatalyst sol, a metal alkoxide, a metal sulfate, a metal chloride solution, an organometallic salt and the like are used. For example, when a TiO2 sol is used, since the isoelectric point of TiO2 is almost neutral at PH6.5, it is easy to apply it uniformly to the surface of the base material using an aqueous solution dispersed with an acid or an alkali. At this time, when the base material is a metal, alkali dispersion is preferable from the viewpoint of corrosion resistance. In the case of ceramics, tiles, ceramics, etc., either acid or alkali dispersion may be used. Examples of the acid include nitric acid, sulfuric acid, hydrochloric acid, acetic acid, phosphoric acid, and organic acids. In the case of alkali, examples thereof include ammonia, hydroxides containing alkali metals or alkaline earth metals, but ammonia is particularly preferable because no metal contaminants are generated after the heat treatment. In addition, an organic-based or phosphoric acid-based dispersant, a surface active agent, a surface treatment agent, or the like may be further added to these dispersions. The average particle size of the photocatalyst sol is 0.05 μm or less, preferably 0.01 μm or less. This is because the smaller the particle size, the higher the photoactivity of the photocatalyst. As a coating method on the substrate, there are a method of applying these starting materials by spray coating, roll coating, dip coating, spin coating, CVD, electron beam deposition, sputtering, etc., and any of them may be used. However, other methods may be used. However, spray coating, roll coating, and dip coating have the advantage that they do not require special equipment and can be coated at low cost as compared with CVD, electron beam deposition, sputtering, and the like. After coating, a layer having a photocatalytic function is formed by means such as drying and firing. By keeping the film thickness of this layer less than 0.4 μm, the amount of particles that fill the gaps (number of coatings), which will be described later, can be reduced as much as possible to satisfy stain resistance (surface smoothness) and abrasion resistance. Productivity can be improved and costs can be reduced.

【0011】

The layer having a photocatalytic function may be passed through a glaze layer such as a glaze layer or a glass layer having a melting point lower than that of the base material in order to improve the adhesion to the base material. It is considered that this is because the layer having a photocatalytic function is partially embedded in the glaze layer. The step of forming the glaze layer on the surface of the base material is performed by applying a glaze component having a softening temperature lower than that of the base material to the base material. The glaze component at this time does not necessarily have to match the composition of the glaze layer at the time of completion of the member. Therefore, the coating material of the glaze component at this time may be a suspension of a glaze composition such as granular, frit-like, lumpy, or powder, or a mixed solution of salts containing a constituent metal component. The coating method includes a spray coating method, a roll coating method, a dip coating method and the like, but any of them may be used.

【0012】

The step of heat-treating at a temperature at which the outermost surface of the photocatalyst layer is exposed and a part of the lower layer is embedded in the glaze layer is lower than the softening point of the base material, and the glaze layer has the composition of the glaze layer at the time of completion of the member. It is carried out by heat treatment at a temperature that changes and softens. Specifically, it is advisable to heat-treat at a temperature 20 to 320 ° C higher than the softening temperature of the glaze layer. By doing so, the photocatalyst particles appropriately move into the glaze layer, and the outermost surface of the photocatalyst layer is exposed and a part of the lower layer is embedded in the glaze layer. The glaze layer applied before the step of forming the photocatalyst layer on the glaze layer may be dried to evaporate water or the like. The drying method at this time includes a method of leaving at room temperature, a method of heating together with the base material, and the like.

【0013】

Further, before performing the step of forming the photocatalyst layer on the glaze layer, the applied glaze layer is lowered to the softening temperature of the base material, and the glaze layer changes to the composition of the glaze layer at the time of completion of the member and is softened. It may be heat treated. According to this method, when the photocatalyst layer is formed on the glaze layer, the glaze layer becomes smoother in advance, so that even a small amount of the photocatalyst particles to be applied can exert a sufficient effect.

【0014】

The gaps formed on the surface of the thin film specifically refer to both the gaps between the particles in FIG. 1 (a), that is, the open pores, and the recesses in the neck portion shown in FIG. 1 (b). Although a thin film is superior in terms of film strength and stain resistance, the finer the thin film, the higher the temperature at which the thin film is formed and the material of the base material is limited. According to the present application in which particles are filled in the gaps, the porosity of the thin film before the addition of the gap particles may be 10% or more. Further, since a film having a porosity of 10% or more is excellent in deodorant property, it is possible to provide a multifunctional material excellent in both antifouling property and deodorant property by adjusting the filling amount.

【0015】

The particles smaller than the gaps filled in the gaps are preferably made of an inorganic crystalline material, and more preferably have photocatalytic activity. Therefore, oxide semiconductors such as TiO2, SnO2, Fe2O3, ZnO, Bi2O3, WO3, and SrTiO3 Is good. The size of particles smaller than the gap should basically be smaller than the average value of the generated pore diameters. Specifically, it is possible to improve the resistance to stains and the film strength by improving the surface smoothness and reducing the surface defects by reducing the gaps and the particles adhering to the surface of the particles having a photocatalytic function. Small particles of less than 0.01 μm, preferably 0.008 μm or less are preferable. However, if the TiO2 thin film is anatase and is heat-treated at 850 ° C or less and fixed on the substrate, it should be smaller than the TiO particle size because the average pore size and the TiO particle size are approximately the same when observed with an electron microscope. Good. Since a raw material of 0.05 μm or less is generally used as a starting material for a TiO2 thin film having photocatalytic activity, it is preferably 0.05 μm or less.

【0016】

Here, by making the porosity of the surface of the layer having a photocatalytic function filled with particles in the gaps less than 20%, it becomes more difficult to get dirty. Further, the maximum width of the open pores is preferably 0.04 μm or less. Here, the porosity refers to the porosity of the surface of the base material, and the maximum width of the open pores is adjacent to the particles having a photocatalytic function constituting the surface of the base material as shown in FIG. 1 (c). It is the maximum value of the distance between the two particles (mean + 3 x standard deviation).

【0017】

If the porosity of the layer having a photocatalytic function before filling the gaps with particles is close to 10%, the porosity is reduced to less than 10%, but the porosity buried here is 0.01. Since it is a size that allows particles smaller than μm to enter and is larger than the size of the gas (several A), it does not affect the deodorant property and is equivalent to a prefabricated TiO2 thin film with a porosity of 10% or more. Can retain the deodorant properties of.

【0018】

Further, by using the formed layer having a photocatalytic function mainly as crystalline photocatalyst particles, the butterbur is relatively easy to adhere even if it adheres, and the stains do not adhere in a strong adhesion form so that the glass adheres. You will be able to wipe it off. In addition, when used around water, it has the effect of making it difficult for algae to grow. Here, the crystalline photocatalytic particles are the maximum peaks of crystals (for example, in TiO2 particles, 2θ = 25.3 ° for anatase, rutile) when powder X-ray diffraction is performed on the photocatalytic particles peeled off from the member under the condition of 50 kV-300 mA. Then, it is a photocatalytic particle crystallized to the extent that 2θ = 27.4 °) is detected.

【0019】

As a method of filling the gaps with particles, metal alkoxide, an organometallic salt, a sulfate or the like is used, and the particles are formed by coating, drying, and heat treatment. For example, the step of using the metal alkoxide is performed by applying a solution of the metal alkoxide to an appropriate diluent and hydrochloric acid on the outermost surface of the photocatalyst layer and then drying and heat-treating it. Here, the suitable diluent is preferably, but is not limited to, alcohols such as ethanol, propanol and methanol. However, it is better not to contain water as much as possible. This is because when water is contained, the hydrolysis of the metal alkoxide is explosively promoted, which contributes to the generation of cracks. Hydrochloric acid is added to prevent cracks during drying and heat treatment. The method of applying the metal alkoxide is usually, but is not limited to, flow coating. The flow coating is preferably performed in dry air. When coated with ordinary air (atmosphere), hydrolysis is promoted by the moisture in the air, making it difficult to control the film thickness. The coating may be applied once or several times. It is determined by the filling property of the photocatalyst layer before coating. After that, when it is left in dry air for several minutes, a film filled with particles is formed in the gaps between the photocatalyst layers. Here, if the layer before applying the packed particles and the packed particles are made of the same material, the coefficient of thermal expansion may be the same, and it is desirable in that a film having excellent mechanical strength can be formed.

【0020】

As a specific example, the one using Ti alkoxide will be further described. In the step of further applying Ti alkoxide to the surface of the photocatalyst layer and performing a dry heat treatment, the amount of Ti alkoxide applied at one time was set to 10 μg / cm2 or more and 100 μg / cm2 or less in terms of TiO2. If the amount is too small, the number of coatings must be increased, which is not efficient. On the contrary, if the amount is too large, the film thickness per application becomes too thick and cracks occur during drying or heat treatment.

【0021】

In the above-mentioned dry heat treatment step, the heat treatment temperature was set to 400 ° C. or higher and 800 ° C. or lower. This is because amorphous TiO2 does not crystallize into anatase-type TiO2 below 400 ° C, and rapid grain growth occurs at 800 ° C or higher, resulting in a decrease in photoactivity. The amount of hydrochloric acid relative to Ti alkoxide in the coating liquid was adjusted to be 1% by weight or more and 10% by weight or less. This is because if it is less than 1% by weight, the crack prevention effect is not sufficient, and if it exceeds 10% by weight, hydrochloric acid is usually a 36% aqueous solution, so a large amount of water enters and hydrolysis is promoted too much to generate cracks. When the amount of hydrochloric acid is large, it is better to have a large amount of diluent. This is because the diluent suppresses hydrolysis. The ratio should be about 1: 100 to 1: 1000 for hydrochloric acid (excluding water): diluent.

【0022】

Further, a layer having a photocatalytic function is formed, and the gap formed on the surface of the layer is filled with particles smaller than the gap, and Cu, Ag, Zn, Fe, Co, Ni, Pd, At least one metal of Pt may be fixed. With such a configuration, the metal occupies the highly adsorptive site of the layer having a photocatalytic function in advance, so that the alkali metal, calcium, etc. in the dust component adhere to this portion and lose the photocatalytic activity. There is no. Therefore, the antibacterial action of the photocatalyst is not easily impaired, and stains due to the adhesion of fungi can be prevented. Further, when Ag, Cu, and Zn are used as the above metals, since these metals themselves have antibacterial properties, it is possible to more effectively prevent stains due to the adhesion of fungi. Furthermore, the photoactivity of the photocatalyst layer is improved by the electron capture effect of these metals. The size of the metal to be fixed should be large enough to occupy the highly adsorptive sites of the photocatalyst layer in advance and small enough to maintain high activity. From this point of view, it is preferably about several nm to 10 nm.

【0023】

As a method for fixing the metal described above, a photoreduction method, a heat treatment method, a sputtering method, a CVD method, etc. can be used, but the point that the metal can be firmly fixed by a relatively simple method without requiring a large-scale equipment. Therefore, the photoreduction method is desirable. The step using photoreduction is carried out by applying an aqueous solution containing at least one metal ion of Ag, Cu, Zn, Fe, Co, Ni, Pd and Pt and irradiating with light containing ultraviolet rays. An aqueous solution containing at least one metal ion of Ag, Cu, Zn, Fe, Co, Ni, Pd, and Pt includes copper acetate, silver nitrate, copper carbonate, copper sulfate, cuprous chloride, and cupric chloride. , Platinum chloride, palladium chloride, nickel chloride, zinc nitrate, cobalt chloride, ferrous chloride, ferric chloride and the like. The method of applying the aqueous metal salt solution is basically any method, but the spray coating method or the dip coating method is convenient. Comparing the two, spray coating is possible because the amount of solution used is small, it can be applied evenly, the film thickness is easy to control, and it is possible when you do not want to apply it to the back surface. The method is more preferred. The light source for irradiating light containing ultraviolet rays may be any one that can irradiate light containing ultraviolet rays, and specifically, any of an ultraviolet lamp, a BLB lamp, a xenon lamp, a mercury lamp, and a fluorescent lamp may be used. In the method of irradiating light including ultraviolet rays, it is preferable to arrange the sample so that the light shines perpendicularly to the irradiation surface. This is because the irradiation efficiency is the highest. The irradiation time is preferably about 10 seconds to 10 minutes. If the irradiation time is too short, the metal species will not sufficiently adhere to the highly adsorptive sites of the photocatalyst layer, which will cause alkali metals, calcium, etc. in the dust component to adhere and lose the photocatalytic activity. This is because the metal species adhere too much and it becomes difficult for light to reach the photocatalyst layer sufficiently, and the photocatalyst activity decreases. The distance of the sample from the light source is preferably 1 cm to 30 cm. If the distance is too short, the entire sample surface is not irradiated with light with almost uniform illuminance, and the adhesion of the above metal species tends to vary. If the distance is too long, the illuminance of the emitted light is the square of the distance.

【0024】

[Action]

In the present invention, a layer having a photocatalytic function is formed on the surface of the base material, and the gap formed on the surface of the layer is filled with particles smaller than the gap, whereby the gap formed on the surface of the thin film is formed. Since the particles are filled with particles smaller than the gaps, the size of the gaps existing on the surface is reduced and the surface smoothness is improved, so that the polymers, dust, fungi, etc. that make up the dirt component adhere. It becomes difficult to do.

【0025】

[Example]

(Example 1) An ammonia-freezing suspension of a TiO2 sol having a crystal diameter of 0.01 μm is applied to a 15 cm square tile substrate by a spray coating method, and this is fired at 750 ° C to form an anatase-type TiO2 thin film. did. The porosity of the TiO2 thin film at this stage was 45%, and the crystal diameter of the TiO2 particles was 0.02 μm. Next, SnO2 sol having different crystal diameters was applied thereto by a spray coating method and dried at 110 ° C. to obtain a sample. The obtained sample was evaluated for deodorant property, abrasion resistance, and stain resistance. The deodorant property was evaluated by measuring R30 (L). R30 (L) is the removal rate after light irradiation. Specifically, the surface on which the anatase-type TiO2 thin film of the sample is formed in an 11 L glass container is placed at a distance of 8 cm from the light source (BLB fluorescent lamp 4W). Then, methyl mercaptan gas is injected into the container so as to have an initial concentration of 3 ppm, and the change in concentration when irradiated with light for 30 minutes is measured.

【0026】

Abrasion resistance was evaluated by performing sliding wear using a plastic eraser and comparing changes in appearance. The evaluation index is shown below. : No change for 40 round trips : The TiO2 layer is peeled off due to scratches caused by sliding 10 times or more and less than 40 times. Δ: Scratches are made by sliding 5 times or more and less than 10 times, and the TiO2 layer is peeled off. ×: Scratches occur after sliding less than 5 times, and the TiO2 layer peels off. The resistance to stains was evaluated by drawing a line on the surface of the base material with thick black magic ink, drying the ink, and wiping off the ink with ethanol. The evaluation index is shown. : The trace disappears completely. : A faint mark remains. Δ: Gray-blue marks remain. ×: Black marks remain. The results are shown in the figure.

【0027】

Figure 2 shows the resistance to stains with respect to the amount of SnO2 added. Here, the amount of SnO2 added is expressed as the ratio of the weight of SnO2 to the sum of the amounts of TiO2 and SnO2. With the addition of 30% or more of SnO2, dirt is dramatically less likely to adhere. I understand that the reason for this is the following three points. First, the porosity decreased to less than 20% by adding SnO2 of 30% or more (Fig. 3). Secondly, the addition of SnO2 reduced the number of pores with large pore diameters. FIG. 4 shows the maximum width of the open pores with respect to the amount of SnO2 added, but when the amount of SnO2 added is 30% or more, it is considerably small at 0.04 μm. Thirdly, it is understood that the improvement of surface roughness due to the addition of SnO2 also has an effect. Figure 5 shows the deodorant properties and wear resistance with respect to the amount of SnO2 added. Regarding the deodorant property, even if the crystal diameter of the SnO2 sol was changed from 0.0035 μm to 0.01 μm, there was almost no change, and good results were shown. When the amount of SnO2 was 50% or less, R30 was 80% or more, which was a good result. Comparing the relationship between the amount of SnO2 added and the porosity in FIG. 2, the porosity is less than 10% when the amount of SnO2 added is 40% or more and 50% or less, but the deodorant property is good. This tendency is different from the relationship between the porosity and the deodorant property when the particles that fill the gaps of the earlier application are not added (Fig. 6). The reason is considered as follows. That is, in this case, the porosity is reduced to less than 10%, but pores of about 0.02 μm still remain as shown in Fig. 4, and the crystal diameter of the particles filling the gap is 0.0035 μm, which is the size of the gas (number A). This is because the gas passage is not closed under this condition without grain growth because it is larger than the other.

【0028】

Regarding wear resistance, the effect when the amount of SnO2 added was 30% or more differed depending on the crystal diameter of the SnO2 sol. That is, when particles of 0.008 μm or less were added, it improved to or , but no effect of addition was observed at 0.01 μm. From this experiment, the following was found. (1) When a TiO2 film is formed on the base material and particles (SnO2 sol) smaller than the gaps are added to the gaps formed on the surface of the thin film, it becomes difficult for stains to adhere. (2) When the amount of SnO2 added is 30% by weight or more based on the total weight of TiO2 and SnO2, it is difficult to get dirty and the wear resistance is improved. (3) When the amount of SnO2 added is 50% by weight or less based on the total weight of TiO2 and SnO2, the deodorant property can be maintained in good condition. (4) If the porosity is less than 20% and the maximum width of the open pores is 0.04 μm or less, dirt is less likely to adhere.

【0029】

【0030】

(Example 3) A method of applying SiO2-Al2O3-Na / K20 frit on the surface of a 15 cm square ceramic tile, and then spray-coating the surface with an ammonia defibrated suspension of TiO2 sol having a crystal diameter of 0.01 μm. And fired at 750 ° C for 2 hours to prepare three types of TiO2 thin films of 0.2 μm, 0.4 μm, and 0.8 μm. The porosity of the TiO2 thin film at this stage was 45%, and the crystal diameter of the TiO2 particles was 0.02 μm. A 10: 1: 400 (weight ratio) mixture of titanate tetraethoxydo, 36% hydrochloric acid and ethanol was further applied to the cooled sample by a flow coating method using dry air as a carrier and dried. The coating amount was 40 to 50 μg / cm2 for TiO2. Then it was fired at 500 ° C for 10 minutes. This Ti alkoxide coating step was repeated 1 to 5 times. The obtained sample was evaluated for deodorant property, antibacterial property, abrasion resistance, and stain resistance.

【0031】

The antibacterial property was tested using Escherichia coli W3110 strain. 0.15 ml (1 to 50000 CFU) of the bacterial solution was dropped on the outermost surface of the multifunctional material sterilized with 70% ethanol in advance, placed on a glass plate (100 × 100), and brought into close contact with the outermost surface of the base material to prepare a sample. After irradiating a white lamp (3500 lux) for 30 minutes, the bacterial solution of the irradiated sample was wiped with sterile gauze and collected in 10 ml of physiological saline, and the survival rate of the bacterial solution was calculated and used as an evaluation index. The evaluation index is shown below. +++: E. coli survival rate less than 10% ++: E. coli survival rate of 10% or more and less than 30% +: E. coli survival rate 30% or more and less than 70% -: E. coli survival rate of 70% or more Under all of the above conditions, the deodorant property was 80% or more at R30 (L), and the antibacterial property was +++.

【0032】

The stain resistance (Fig. 7) and wear resistance (Fig. 8) depended on the number of times Ti alkoxide was applied and the TiO2 film thickness. Increasing the number of times Ti alkoxide was applied improved the resistance to stains and wear resistance. In addition, the thinner the TiO2 film thickness, the less the number of times Ti alkoxide was applied, and the more difficult it was to get dirty and the better the wear resistance. One of the reasons for the above is considered to be a decrease in the porosity on the surface of the TiO2 layer due to the application of Ti alkoxide. FIG. 9 shows the relationship between the porosity on the surface of the TiO2 layer, the number of times Ti alkoxide is applied, and the TiO2 film thickness. The porosity on the surface of the TiO2 layer decreases as the number of Ti alkoxide coatings increases, and decreases with the same number of Ti alkoxide coatings as the TiO2 film thickness decreases, and this relationship is related to the number of Ti alkoxide coatings and the TiO2 film thickness. It corresponds well with the relationship between stain resistance and abrasion resistance. In particular, in terms of resistance to stains, the porosity was when the porosity was less than 20%, as in the case of Example 1.

【0033】

(Example 4) A method of applying SiO2-Al2O3-Na / K20 frit on the surface of a 15 cm square ceramic tile, and then spray-coating the surface with an ammonia-freezing suspension of TiO2 sol having a crystal diameter of 0.01 μm. And fired at 750 ° C for 2 hours. The film thickness of the TiO2 thin film at this stage was 0.4 μm, the porosity was 45%, and the crystal diameter of the TiO2 particles was 0.02 μm. A 10: 1: 400 (weight ratio) mixture of titanate tetraethoxydo, 36% hydrochloric acid and ethanol was further applied to the cooled sample by a flow coating method using dry air as a carrier and dried. The coating amount was 40 to 50 μg / cm2 for TiO2. Then it was fired at 500 ° C for 10 minutes. This Ti alkoxide coating step was repeated 3 times. After that, a 1 wt% silver nitrate aqueous solution was further applied onto the sample, and the sample was obtained by photoreduction (light source was a 20 watt BLB lamp, the distance from the light source to the sample was 10 cm, and the irradiation time was 30 seconds). Here, the amount of silver supported on the sample surface was 0.7 μg / cm2, and the silver particle size was about 40 nm on average. The antibacterial properties of the obtained samples and the antibacterial properties after long-term use were measured.

【0034】

The antibacterial properties after long-term use were tested as follows. First, the surface of the obtained sample was thoroughly washed with ethanol or the like and dried at 50 ° C. Next, bath water collected in a public bath was placed in a sterilized beaker, and the sample was immersed in the water and left for 1 month. Then, the sample was taken out, washed with ethanol or the like, and the outermost surface of the multifunctional material was sterilized with 70% ethanol. Next, 0.15 ml (1 to 50000 CFU) of a bacterial solution of Escherichia coli W3110 strain was placed on a glass plate (100 × 100) and brought into close contact with the outermost surface of the substrate to prepare a sample. After irradiating a white lamp (3500 lux) for 30 minutes, the bacterial solution of the irradiated sample was wiped with sterile gauze and collected in 10 ml of physiological saline, and the survival rate of the bacterial solution was calculated and used as an evaluation index. The evaluation index is the same as the antibacterial property test of Example 3.

【0035】

For comparison, the sample used in Example 3 was also tested. As a result, the initial antibacterial properties of both the sample prepared in this example and the sample prepared in Example 3 were +++, but there was a difference in antibacterial properties after one month. occured. That is, the antibacterial property of the sample prepared in Example 3 deteriorated to +, but the sample prepared in this Example showed +++, which is the same value as the initial value. It is understood that this is because silver occupies the highly adsorptive sites on the surface of the TiO2 layer to prevent dust and the like from adhering to the highly adsorptive sites during use.

【0036】

[Effect of the invention]

A layer having a photocatalytic function was formed on the surface of the base material, and particles smaller than the gaps were filled in the metaphysically formed gaps of the layer, so that the amount and size of the gaps existing on the surface were larger than those of the conventional photocatalytic thin film. Is reduced and the surface smoothness is improved, so that the film strength can be improved while maintaining the deodorant property and the antibacterial property, and the polymer, dust, fungi and the like constituting the dirt component can be prevented from adhering. ..

[Simple explanation of drawings]

[Figure 1]

(a) to (c) are diagrams for explaining the configuration of the embodiment of the present invention.

[Figure 2]

A graph showing the relationship between the amount of particles added to the gap and the difficulty of getting dirty [Fig. 3]

A graph showing the relationship between the amount of particles added to the gap and the open porosity of the surface of the layer having a photocatalytic function. [Fig. 4]

A graph showing the relationship between the amount of particles added to the gap and the maximum pore width on the surface of the layer having a photocatalytic function. [Fig. 5]

Graph showing the relationship between the amount of particles added to the gap and the deodorant property and wear resistance [Fig. 6]

A graph showing the relationship between the porosity of a layer having a photocatalytic function that does not fill the gaps with particles, and deodorization and wear resistance [Fig. 7]

Graph showing the relationship between the number of coatings of particles filled in the gap and the difficulty of getting dirty [Fig. 8]

Graph showing the relationship between the number of coatings of particles filled in the gap and wear resistance [Fig. 9]

A graph showing the relationship between the number of coatings of particles filled in the gap and the open porosity of the surface of the layer having a photocatalytic function.