Multifunctional material having photocatalyst function

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a base material obtained by firing at a high temperature, for example, a member having functions such as antibacterial property, deodorant property, and antifouling property added to the surface of ceramics, tiles, ceramics, and the like.

【0002】

[Conventional technology]

TiO2, ZnO, V2O5, WO3, SrTiO3, CdS, etc. are substances that exert the function of adsorbing or desorbing oxygen molecules on organic compounds such as malodorous components by irradiating them with ultraviolet rays and promoting their decomposition. It is known that TiO2, which has a crystalline form of anatase, is particularly effective as a photocatalyst. Therefore, for example, it is represented by supporting it on the surface of a discharge lamp container (Japanese Patent Laid-Open No. 1-169866) and deodorizing it by a photocatalytic function. Proposals have been made to support the surface of various substrates as described above. The conventional method of forming a photocatalyst thin film on the base material is mainly a method of directly supporting the photocatalyst particles on the base material by a method such as spray coating. [0003]

[Problems to be Solved by the Invention]

The direct support method does not provide sufficient adhesion between the photocatalyst thin film and the base material, and is particularly useful when the photocatalyst thin film is provided on a relatively dense base material such as glass, tile, metal, or plastics. There was a problem that it was easy to peel off.

【0004】

[Means for solving problems]

The present invention has been made in view of the above problems, and is a photocatalytic layer having antibacterial, deodorant, antifouling and other functions on the surface of a base material obtained by firing at a high temperature, for example, ceramics, tiles, ceramics and the like. The purpose is to increase the adhesion between the photocatalyst thin film and the base material and improve the peeling resistance, and the gist of this is that the photocatalyst layer is held on the surface of the base material via an amorphous layer. The photocatalyst layer is exposed so that its upper layer is in contact with the outside air, and the photocatalyst layer is a multifunctional material having a photocatalyst function in which particles are bonded to each other. It is a multifunctional material having a photocatalytic function characterized by having an intermediate layer in which the concentration of the components of the above changes.

【0005】

It will be described in detail below. The material of the base material may be basically anything such as ceramics, ceramics, glass, metals, plastics or composites thereof, but heat resistance above a temperature at which the amorphous layer can be sufficiently softened is required. The shape of the base material may be any shape, and may be a simple shape such as a plate shape or a spherical shape, or a complicated shape such as a sanitary ware, a wash basin, and a bathtub. The surface of the base material may be a part or the entire surface of the base material. The amorphous layer is a layer in an amorphous state containing a structure such as Si or B as a main component, and other modified substances such as alkali, intermediates such as alumina, and coloring components such as transition metal oxides. Etc. may be included.

【0006】

The material of the photocatalyst layer is basically composed of oxide semiconductors such as TiO2, ZnO, V2O5, WO3 and SrTiO3, and a metal such as Ag and Cu may be added thereto. The state in which the photocatalyst layer is exposed so that its upper layer is in contact with the outside air includes not only the case where it is exposed to the outermost surface but also the state where it is exposed to the open pore surface. The optimum structure of the above two types of structure differs depending on the application. In the antibacterial multifunctional material, the contact between the fungus and the photocatalyst is important, so the structure on the outermost layer is excellent. In the decomposition, the structure exposed on the open pore surface, which can have a large contact area with the gas, is excellent.

【0007】

The state in which the particles of the photocatalyst layer are bonded to each other is sufficient if the particles have a bonding force sufficient to withstand the shear stress according to the application. As the method, it is desirable to sinter the photocatalytic particles with each other, but the photocatalytic particles may be bonded by adsorption. In that case, the specific surface area must be increased, that is, the particle size must be as small as possible, and the filling property must be improved. Further, by filling the gaps between the photocatalyst particles with particles having a particle size smaller than the gaps (metals such as Sn, Ti, Ag, Cu, Zn, Fe, Pt, Co, Pd, Ni, etc. or their oxides) later. , Photocatalyst particles may be bonded to each other.

【0008】

The intermediate layer in which the concentrations of both components continuously change between the amorphous layer and the photocatalyst layer will be described with reference to FIGS. 1 and 2. FIG. 1 is a conceptual diagram of a basic profile when the cross-sectional direction of the multifunctional material according to the present application is observed by EPMA (electron probe microanalyzer). As shown in FIG. 1, the concentration of the components constituting the photocatalyst layer continues for a while from the surface (region A), and then the components constituting the photocatalyst layer decrease. In addition, the components constituting the amorphous layer are small or absent on the surface, and the concentration increases toward the inside. Then, when the film thickness reaches a certain level, the component concentration becomes almost constant (region B). Here, the A region is defined as a photocatalytic layer, the B region is defined as an amorphous layer, and the C region in the middle is defined as an intermediate layer. However, FIG. 1 is a conceptual diagram for convenience of explanation only, and in reality, as shown in FIG. 2, the portion described as having a constant concentration in FIG. 1 often accompanies fluctuations in the concentration caused by manufacturing process reasons. .. In this case, as shown in the figure, the parts that reach the minimum concentration of the regions (A'region and B'region) corresponding to a certain region are the A'region and C'region, and the B'region and C'region, respectively. Was regarded as the boundary of.

【0009】

The thickness of the photocatalyst layer is the thickness of the A region or the A'region, and the thickness of the intermediate layer is the thickness of the C region or the C'region. The thickness of this intermediate layer can be changed by controlling the speed at which the photocatalytic particles move into the softening amorphous layer and the time during which they can move. The moving speed can be controlled by the difference in specific gravity between the photocatalytic particles and the amorphous layer, the firing temperature, the atmospheric pressure, and the like. Further, the movable time can be changed by changing the holding time at the temperature at which the amorphous material softens.

【0010】

[Action]

The photocatalyst layer is held on the surface of the base material via an amorphous layer, the photocatalyst layer is exposed so that the upper layer thereof is in contact with the outside air, and the photocatalyst layer secures the film strength by binding the particles to each other. Further, by embedding the photocatalyst layer in the amorphous layer so as to have an intermediate layer in which the concentrations of both components continuously change between the amorphous layer and the photocatalyst layer, the photocatalyst thin film and the base material can be obtained. Adhesion can be increased and peeling resistance can be improved.

【0011】

[Example]

(Example 1) A SiO2-Al2O3-Na / K2O-based amorphous layer is formed on a 10 cm square alumina substrate by a spray coating method, dried and fired, and then spray-coated with a TiO2 sol aqueous solution having an average particle size of 0.01 μm. It was applied by the method, and this was fired at 850 ° C for different holding times to form amorphous TiO2 thin films having thicknesses of 0.2 μm, 0.5 μm, and 1 μm. Next, an aqueous solution of copper acetate is applied to this anatase-type TiO2 thin film by a spray coating method, and then photoreduction (light source is a 20 watt BLB lamp, distance from the light source to the sample is 10 cm, irradiation time is 30 seconds) to obtain a sample. It was. The obtained sample was evaluated for film thickness measurement by elemental analysis (Ti, Si) of cross section by EPMA, antibacterial property and wear resistance. For antibacterial evaluation, Escherichia coli Tested using W3110 strain). 0.15 ml (1 to 50000 CFU) of the bacterial solution was dropped on the outermost surface of the multifunctional member 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 criteria are 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 The wear resistance was evaluated by performing sliding wear using a plastic eraser and comparing changes in appearance. The evaluation criteria are shown below. : No change for 40 round trips : The photocatalyst layer peels off due to scratches caused by sliding 10 times or more and less than 40 times. Δ: The photocatalyst layer is peeled off due to scratches caused by sliding 5 times or more and less than 10 times. ×: The photocatalyst layer is peeled off due to scratches caused by sliding less than 5 times. The results are summarized in Table 1. All antibacterial properties were +++. The wear resistance was also or , showing good results. In particular, the ratio of the thickness of the intermediate layer to the thickness of the photocatalyst layer was in all samples of 1/3 or more.

[table 1]

<img file="JPH08103488A_D0001.tif" />【0012】

(Comparative example) An ammonia dispersion of TiO2 sol with an average particle size of 0.01 μm is applied on a 10 cm square alumina substrate by a spray coating method, and this is fired at 850 ° C to form an anatase-type TiO2 thin film with a thickness of 1 μm. Formed. Next, an aqueous solution of copper acetate is applied to this anatase-type TiO2 thin film by a spray coating method, and then photoreduction (light source is a 20 watt BLB lamp, distance from the light source to the sample is 10 cm, irradiation time is 30 seconds) to obtain a sample. It was. The antibacterial properties and wear resistance of the obtained samples were evaluated. As a result, the antibacterial property was good as +++, but the wear resistance was insufficient as Δ.

【0013】

[Effect of the invention]

A photocatalyst layer is held on the surface of the base material via an amorphous layer, the photocatalyst layer is exposed so that the upper layer thereof is in contact with the outside air, and the photocatalyst layer is multifunctional having a photocatalyst function in which particles are bonded to each other. In the material, the amorphous layer and the photocatalyst layer have an intermediate layer in which the concentrations of both components change continuously between them, thereby increasing the adhesion between the photocatalyst thin film and the substrate and peeling resistance. Was able to be improved. Further, when the thickness of the intermediate layer was set to 1/3 or more of the thickness of the photocatalyst layer, the adhesion could be further increased.

[Simple explanation of drawings]

[Figure 1]

The figure explaining the thickness of the photocatalyst layer, the intermediate layer, and the amorphous layer which concerns on this invention. [Figure 2]

Other figures for explaining the thickness of the photocatalyst layer, the intermediate layer, and the amorphous layer according to the present invention.