Substrate with photocatalytic coating

[0001] The present invention relates to a substrate with a photocatalytic coating, a method for obtaining such a coating, and various uses thereof. [0002] The present invention particularly relates to coatings comprising semiconductor materials based on metal oxides, especially titanium oxide. Here, the coating is capable of initiating a radical reaction that results in the oxidation of organic matter by the effect of radiation of the appropriate wavelength. [0003] Such a coating allows the material to be coated to be imparted with new functionality, in particular antifouling, fungicidal, and bactericidal properties, and optionally with hydrophilicity, antifogging, optical properties, etc. Have. [0004] A very wide variety of substrates can be considered, especially glazing; wall materials, cladding materials, roofing and flooring materials such as tiles, slate, slabs and paving materials; and especially vehicles. Alternatively, materials used in the field of buildings, especially materials used in the building industry, can be considered. These materials are glass, metal, glass-ceramic, cement brick, and materials reconstructed from wood, stone or these natural materials, plastic or fibrous materials, especially inorganic wool-like molds for filtration steps and the like. Can be manufactured from the fibrous material of. [0005] In addition, they can be specifically classified as transparent materials used as windowpanes, such as glass substrates, or made of flexible or rigid plastics such as substrates made of acrylates such as polyester or polymethylmethacrylate (PMMA). Examples of the substrate to be used. [0006] In addition, the substrate is considered to be a "single-material" such as a glass substrate, or a material such as a wall material with a wall-render type coating. It can be thought of as containing overlaps or layers. [0007] Crystallized anatase TiO with photocatalytic properties₂Coatings containing are already known in international patent applications WO97 / 10186 and WO97 / 10185, and these coatings are pyrolyzed and / or embedded in an inorganic or organic binder of a suitable organometallic precursor. And "pre-crystallized" TiO₂Obtained from particles. [0008] Therefore, it is an object of the present invention to improve these types of coatings so that photocatalytic performance lasts longer when exposed to the aging conditions encountered in a variety of expected applications. [0009] Thus, it is an object of the present invention to improve these types of coatings to increase their durability, in particular mechanical or chemical durability, while maintaining or improving their photocatalytic properties in particular. [0010] The gist of the present invention is, firstly, a method for obtaining a substrate having a photocatalytic coating on at least a part of the surface. Here, crystallized particles of an oxide of metal A having photocatalytic properties have photocatalytic properties in a crystalline state. It is compounded in the coating with an inorganic binder containing an oxide of at least one metal B having the above. The binder may further optionally include at least one oxide of metal M lacking photocatalytic properties and / or at least one silicon oxide SiO.₂It may contain a type of silicon compound. This method comprises (a) crystallized particles of an oxide of metal A; and (b) at least one precursor compound for the oxide of metal B of an inorganic binder, and optionally an oxide of metal M and /. Or from one or more liquid phase dispersions containing precursor compounds for silicon compounds, including attaching a coating, where the relative ratio defined by the A / (B + M + Si) ratio is 60. It is / 40 ~ 40/60. This ratio, on the other hand, corresponds to the mass of metal A to the mass of metal B and any metal M and silicon (Si), the oxide of metal A in the form of particles, and the oxide of metal B and Oxide of any metal M and SiO₂Each precursor for a silicon compound of type is included in the composition. [0011] Advantageously, the adhesion / treatment conditions of the coating are selected such that the oxide of the inorganic binder, especially the metal B forming a portion thereof, crystallizes at least partially in the final coating. [0012] Preferably, the oxides of metal A and metal B are selected from at least one of the following oxides: titanium oxide, zinc oxide, tin oxide and tungsten oxide. One particularly preferred embodiment is to select both the oxides of metal A and metal B in the form of highly photocatalytic anatase crystals, titanium oxide (titanium dioxide). [0013] Oxides of metal M that lack the inherent photocatalytic properties are, for example, aluminum oxide or zirconium oxide. [0014] The inventor has succeeded in this method in harmonizing two constraints that have not been easily harmonized, namely photocatalytic performance and durability. In particular, the present inventor has succeeded in maintaining the photocatalytic property of the coating for a long time. This is because it was found that the catalytic effect of the coating would be largely due to the particles contained therein, which were already crystallized and were already active as catalysts from the beginning. Therefore, we want to maximize the amount of particles in the coating. Surprisingly, however, it turns out that neither excessively large amounts nor excessively low amounts of particles meet the two desired goals (ie, photocatalytic properties and sufficient durability). The adjustment of the ratio found by the present invention is that the amount and type of particles of the oxide of metal A changes in the form of the binder containing the oxide of metal B, the relatively significant photocatalytic properties of the coating, and the long time. It is increasingly difficult to achieve when it affects holding in the non-linear function of such parameters. [0015] Therefore, the method of the present invention provides an A / (B + M + Si) ratio within a range that maximizes harmony between a satisfactory level of photocatalytic activity and the maintenance of this high level of photocatalytic activity for an extended period of time. Indicates that you can choose. The reason for this is not entirely clear, at least for the photocatalytic performance of the coating. It may be advantageous that the inorganic binder also contributes to the activity of the coating. In addition, it should be noted that the resulting coating helps to have excellent optical properties, especially high light transmittance and very low levels of haze. [0016] The precursors for oxides of metal B and any precursors for oxides of metal M described above are organometallic compounds that can be decomposed into oxides by the effect of appropriate treatment, especially heat treatment. Is preferable. Silicon compounds, especially SiO₂As the precursor, compounds of silicon alcoholides (silanes) can be used. [0017] Advantageously, the methods of the invention are TiO crystallized particles of metal A oxide, especially TiO crystallized primarily in the anatase form.₂), The form of aggregates of crystallites, preferably aggregates having an average size of about 5-80 nm and having microcrystals having an average size of about 5-20 nm (particularly 5-10 nm). The aggregate is used as a dispersion in a liquid phase, particularly a colloidal dispersion in an aqueous medium or a dispersion in an organic solvent. These sizes correspond to the "diameters" of the agglomerates and microcrystals of interest, and their shapes are likened to spheres (not necessarily in this case, especially if the agglomerates are mostly crystalline lenses). Or even if it is rod-shaped.) Rather than mentioning agglomerates of microcrystals, more accurate terms can actually be used: aggregates are particles and microcrystals are in the domain of crystalline. It can be referred to by the term coherence). In the first approximation, the same agglomerates are found in the final coating, which can be considered to undergo little or no structural or dimensional changes. In fact, when the method for obtaining a photocatalytic coating involves heat treatment (discussed in detail below), this treatment results in structural modification of these particles, i.e. a clear increase in crystallite size. become. For example, TiO₂When the crystallites are initially about 5-10 nm in size, they are usually about 10-20 nm in the final coating. That is, their size is approximately doubled (1.5 to 2.5 times). A detailed description of these particles can be found, for example, in WO / FR97 / 02068 or FR2,681,534 on November 18, 1997, published under the numbers WO97 / 10185, or WO98 / 23549, in the aforementioned application. [0018] Preferably, the oxide of metal B, and optionally the precursor organometallic compound for the oxide of metal M, is of formula M (OR).₄Tetraalkoxides (where M is the metal and R is a linear or branched alkyl-type carbon-containing residue, all of which are the same or different, especially having 1 to 6 carbon atoms). Is selected from. For example, titanium tetrabutoxide or titanium tetraisopropoxide can be mentioned. MR'(OR)₃They can also be selected from the types of trialkoxides (R and R'are of the same or different type as the tetraalkoxides described above), or halides, especially titanium chloride. Since these precursors are highly hydrolyzable and highly reactive, it is preferable to dissolve at least one chelate / stabilizer with them. For example, β-diketone types such as acetylacetone (2,4-pentandione), benzoylacetone (1-phenyl-1,3-butandione) and diisopropylacetylacetone, or acetic acid, diethanolamine, or ethylene glycol or tetraoctylene. Examples include compounds of the family of glycols such as glycols. The precursor concentration in solution (eg, given solid content) is then adjusted by appropriate dilution with one or more organic solvents. [0019] According to the first modification of the present invention, the coating inorganic binder of the present invention contains only an oxide of metal B, and therefore the A / (B + M + Si) ratio described above is more easily A / B. Become a ratio. [0020] According to the second modification of the present invention, the inorganic binder is an oxide of metal B, TiO.₂SiO which is a type oxide and silicon compound₂It contains type oxides, so the A / (B + M + Si) ratio is A / (B + Si). [0021] [0021] The simplest way to carry out the method according to the invention consists of attaching a coating from a dispersion containing precursors and a dispersion containing particles, in which case the dispersion is sprayed onto a substrate or simply. Prior to immersing the substrate in the monodisperse, it is premixed into the monodisperse. However, it is also conceivable to attach the coating from several separate dispersions, especially two dispersions, without premixing them. [0022] The first type of adhesion method is called "hot" adhesion. Here, during contact between the dispersion and the substrate, the substrate is hot enough to thermally decompose the precursor. This is a liquid phase pyrolysis type method. [0023] The second type of method is called "cold" adhesion. Here, during contact between the dispersion and the substrate, the substrate is at room temperature, or at least a low temperature that does not cause thermal decomposition of the precursor. These are sol-gel type methods and include dipping, cell-coated, laminar-coated, or spray coated attachment methods. [0024] Heat treatment after the contact step between the dispersion and the substrate is required in the case of "cold" decomposition to cure the coating and ensure that the precursor is completely decomposed. However, this is also advantageous for "hot" decomposition methods. This is because it can improve the bond of the coating and can also be advantageous for at least partial crystallization of the binder resulting from the decomposition of the precursor. This treatment is at least 400 ° C, for example above 450 ° C, more particularly if the substrate can withstand this type of treatment, i.e. if the substrate has a glass, ceramic or glass-ceramic matrix, at 550-500 ° C. Especially implemented in the range. [0025] Further, the present invention is a photocatalyst in which crystallized particles of an oxide of a metal A having a photocatalytic property are blended using an inorganic binder containing an oxide of the metal B having a photocatalytic property in a crystalline state and at least partially crystallized. It is a substrate having a coating on at least a part of the surface, and in particular, a substrate as obtained by the above-mentioned method. The substrate is characterized by a high porosity, particularly greater than 40%, preferably 45-65% porosity. This porosity can be calculated indirectly by measuring the index of refraction of the actual layer and comparing it to the index of refraction when the material is perfectly dense. Since the index of refraction measurement takes into account the degree of surface roughness of the layer at least in part, this indirect method provides a good indication of the porosity and surface morphology of the layer. [0026] (There are also other indirect methods, which in particular consist of measuring the mass of the adhered coating per area of the substrate in relation to the coating thickness.) [0027] In fact, this high porosity has many advantages. First, it can reduce the index of refraction of a substance, and change its optical appearance. TiO₂Coating mainly composed of TiO crystallized as anatase₂Particles and TiO₂Binder with the main raw material, optionally SiO₂In the case of (including those made by blending), the refractive index can be reduced to 2 or less; in particular, it can be reduced to about 1.4 to 1.8, preferably about 1.7 to 1.8, which is well known. It makes it possible to greatly reduce the reflective appearance of the body. [0028] Furthermore, the porosity of the coating is associated with high surface roughness, so the highly developed surface area of the coating is advantageous for photocatalytic activity. [0029] Finally, as described in WO98 / 23549 above, there are probably two different types of this roughness, which gives the coating improved lasting hydrophilicity, thereby providing significant rain resistance and anti-fog properties. (Water droplets spread on the invisible film) to promote the removal of mineral impurities due to the accompanying droplets of rainwater. Surprisingly, this high porosity does not, from a mechanical point of view, overly weaken the coating. [0030] Further, the gist of the present invention lies in a substrate having a coating having photocatalytic properties at least on a part of the surface, where at least one oxide of metal B having photocatalytic properties in a crystalline state, and any at least one. Crystallized particles of an oxide of metal A having photocatalytic properties are blended with an inorganic binder containing an oxide of metal M and / or a silicon oxide type silicon compound lacking the photocatalytic properties of the species, in particular. This substrate is obtained by the method described above. This substrate is composed of oxide particles of metal A, an oxide of metal B of an inorganic binder, and an oxide of any metal M and the mass of each metal (and optionally Si) contained in the composition of the silicon compound. Is characterized by the relative ratio A / (B + M + Si) of 60/40 to 40/60. [0031] It should be noted that in the present invention, the expected substrate may be porous (eg, when the expected substrate is tile) or have a fibrous appearance (eg, mineral insulation wool). Is. When a substrate is said to have a photocatalytic coating, the coating adheres to its surface, but it should also be understood that if the substrate is porous / fibrous, the substrate can be impregnated beyond a certain depth. Is. Therefore, when the substrate is not porous, for example when the substrate is a glass substrate, the amount of coating is represented by the thickness on the substrate, or especially when the substrate has a certain porosity, the amount of material per unit area. The amount of coating can be expressed by. [0032] The coating according to the invention advantageously has the following structures (particularly metal A and metals), even if obtained by the methods described above and / or their unique features are compatible with the coatings described above. Both oxides of B are TiO₂The crystallized particles have a size of 5 to 80 nm, the crystal interference region has a size of 5 to 20 nm (according to the above-mentioned rules), and the inorganic binder is between the particles. It is in the form of particles, at least partially around the crystallized particles up to the plow, which have an average size of 5-25 nm, preferably 10-20 nm. These approximately spherical "particles" do not crystallize completely and are probably partially crystallized on a very small scale that is difficult to measure, thereby "encapsulating" the particles. ) And combine them together. [0033] Advantageously, the substrate of the present invention comprises the photocatalytic coating of the present invention, which is essentially anatase-shaped TiO.₂Particles and partially crystallized TiO₂And SiO₂Includes an inorganic binder in combination with. Preferably, the coating has a refractive index of 2 or less, particularly 1.5 to 1.9, or 1.6 to 1.9, or 1.6 to 1.8. [0034] According to one embodiment, at least one layer is inserted between the substrate and the photocatalytic coating, and the layer has various functions (optical function, barrier function against chemical species such as alkali metals that are easily migrated from the substrate). , Antistatic function, adhesive function, etc.). [0035] Si, SiO₂, SiON, SiOC and Si₃N₄A layer mainly composed of a silicon compound such as, or an optionally doped metal compound (F: SnO)₂, Sb: SnO₂, Etc.) as the main component. [0036] Hypokeimenons with such coatings have already been mentioned in the preface of this application. They include transparent materials of glass or plastic type, especially windowpanes attached to buildings or vehicles, or screens for televisions or computer-type equipment, such as touch screens, or laminated or "monolithic" windowpanes (ie). , A single windowpane or a single plastic sheet). Further, it is advantageous to incorporate a transparent substrate with the coating of the present invention into the insulated multilayer window glass structure, the coating being made on the inner or outer surface of the window glass. The substrate may be a common insulated glazing with one or more gas intermediate layers, for example, marketed by Saint-Gobain Vitrage under the names BIVER or CLIMALITD, CONTRATHERM, CONTASONOR, CONTARISC. The substrate may also be referred to as a "vacuum" windowpane, in which the gas intermediate layer is replaced by a vacuum, which are described, for example, in European Patent No. 645,516. Especially in the latter case, it is particularly advantageous to put a coating as an outer surface on the surface of the heat insulating glass window facing the outer side, and as a result, its hydrophilicity prevents the formation of fogging. [0037] The coatings of the present invention are also advantageous for window glass walls of refrigerating equipment / refrigerators. In fact, many materials can be used as substrates for the coatings of the present invention, for example metal, ceramic, plastic or cement materials, such as tiles and slate, wall materials, cladding materials or roofing materials. It is used in construction for the purpose of. In addition, they may be materials such as slabs or tiles that are attached to the floor or wall inside or outside the dwelling. [0038] In addition, the coating can be attached to inorganic wool-type fibrous materials for heat insulation and / or soundproofing, or other woven yarn-type fibers for reinforcement. These fibrous materials can find applications in the filtration process. For example, if desired, the antifouling property, bactericidal property, antifungal property, and antifogging property of the coating of the present invention can be utilized. [0039] Further, the gist of the present invention lies in the liquid phase dispersion, which is particularly as described above, and can be used in the production of the photocatalytic coating according to the present invention. The dispersion specifically comprises a solvent selected from water, ethylene glycol, ethanol, propylene glycol and mixtures thereof. [0040] The titanium dioxide crystal phase of the dispersion of the present invention is preferably mainly anatase crystal phase. "Mainly" means that the anatase content in the coated titanium dioxide particles is greater than 50% by mass. Preferably, the coated particles have an anatase content greater than 80%. The crystallinity and properties of the crystalline phase are measured by X-ray diffraction. [0041] The dispersion of the present invention is usually obtained by mixing a dispersion of titanium dioxide particles with a solution of a precursor compound and / or a silicon compound. Depending on the nature of the compounds used, additives such as co-solvents, surfactants or stabilizers can also be added during this mixing. Mixing can be further improved by stirring the dispersion with ultrasonic waves. [0042] Further details and advantageous features of the present invention will become apparent with the help of the following unrestricted illustrations and drawings. [0043] [Example] The first series of examples relates to the adhesion of a so-called "antifouling" coating onto the transparent substrate 1 which is essentially titanium dioxide as the main component. [0044] Hypokeimenon 1 is transparent, flat silica-soda-lime glass (area 15 x 40 cm)², Thickness 4 mm). Of course, the present invention is not limited to this particular type of glass. Moreover, the glass is not flat and may be bent. [0045] A thin layer 2 containing silicon oxycarbide (SiOC) as a main component and / or an optical function for the purpose of forming a diffusion barrier against alkali metals harmful to the photocatalytic properties of the coating between the coating 3 and the substrate 1. A layer having a thickness of, for example, a layer attached by a method known by a chemical vapor deposition (CVD) method and having a thickness of about 50 nm may be optionally provided. [0046] Two different "cold" adhesion methods were used. That is, the adhesion by immersion in the cell coating method in a bath with a drainage rate of about 5 to 30 cm / min and the spray coating, that is, the adhesion method by cold liquid spray were used. These well-known methods are described in detail in the patent application described above, which can be referred to. [0047] The coating is attached from the dispersion obtained by mixing the two first solutions / dispersions 1 and 2. [0048] (Solution 1) This is TiO₂It is a solution containing an organometallic precursor for an inorganic binder containing as a main component. It is acetylacetoneate (CH) dissolved in ethanol₃-CO-CH₂-CO-CH₃) Stabilized Titanium Isopropilate {Ti (OCH (CH)₃)₂)₄}. [0049] (Dispersion 2) This is an ethylene glycol liquid phase containing photocatalytic crystallized particles with the following properties: Specific surface area of particles: 350m²/ g Particle size: about 40 nm Size of crystallites forming particles: 7 nm Crystalline phase: more than 80% anatase. [0050] The composition of the dispersion obtained by mixing Solution 1 with Dispersion 2 is the desired Ti.₍₂₎/ Ti₍₁₎The ratio is adjusted to obtain the ratio of the mass of titanium (2) from the particles of dispersion 2, that is, the mass of titanium (1) from the precursor of solution 1. (Assuming 100% of the precursor is converted to oxide, this ratio may be the ratio of the mass of titanium oxide from the particles to the mass of titanium oxide from the metal precursor, which is It is attributed to the same thing.) [0051] Examples 1 to 7 have the same adhesion conditions, that is, the same bath discharge rate (6 cm / min) and titanium concentration from the precursor of solution 1 (that is, 3% solid content in terms of oxide mass). (Regarding adhesion by immersion in the cell coating method). [0052] After attachment, the substrate is heat treated at about 450-500 ° C for at least 30 minutes. [0053] The symbols in Table 1 below are as follows: Ti₍₂₎/ Ti₍₁₎Ratio: As mentioned above (no units); Thickness of coating (3) (e): (unit: nm); Light transmittance value T_L:( Unit%) D₆₅Measured with a illuminant; "Haze" value: (Unit%) Measured as the ratio of diffuse transmission to integrated light transmission over the entire visible range. [0054] [table 1]<img file="JP4911376B2_D0001.tif" />[0055] Example 8 was made from the same dispersion used in Example 4, but at 0.7 bar (0.7 × 10).⁵At the pressure of Pa), it was adhered to the substrate by cold spray using a so-called airless spray nozzle. The resulting layer is heat treated at about 450-500 ° C for at least 30 minutes and then has a thickness of about 35-60 nm, T, as shown in Table 1._LIt had a value of 88.6% and a haze value of 0.6%. [0056] Examples 1-8 above were evaluated for photocatalytic activity before and after treatment for the purpose of simulating accelerated aging of the coating. [0057] Photocatalytic activity is measured by the following method. (1) Approximately 15 cm of coating²Run the test for; (2) Weighing the sample and the thickness of the substrate, T_LAnd haze measurements; (3) Glass / spray nozzle distance 20 cm, substrate vertical, 3-4 consecutive passes, spray adhesion of palmitic acid solution (8 g acid for 1 L chloroform); (4) In order to measure the thickness of the attached acid in nm, weigh the sample after attaching palmitic acid; (5) Haze and T after adhesion_LMeasurement; (6) UVA irradiation time (approx. 30V / m)²) As a function of measuring changes in haze; (7) Graphical determination of the time the haze decreased to 50%: This time is T_1/2Called (disappearance); (8) ν (nm / h) = [Palmitic acid thickness (nm)] / [2 × t_1/2(Extinction) (h)], the photocatalytic activity of the coating is evaluated as the extinction rate ν (nm / h). [0058] [0058] Coating aging consists of mechanically abrading the coating as follows: Sample size: 7 cm x 15 cm Load Load: 600g Abrasive cloth area: 1.5 cm² Number of cycles (n) (1 cycle = 1 reciprocating motion of felt and load carrier arm): 200 and 500. [0059] The symbols in Table 2 are as follows: Extinction speed ν1: Before wear Extinction speed ν2: After 200 cycles Extinction speed ν3: After 500 cycles. [0060] [Table 2]<img file="JP4911376B2_D0002.tif" />[0061] In addition, analysis showed that the coatings in Examples 3, 4 and 5 had a structure probably similar to that shown in FIG. 1 in a very simplified manner (glass substrate 1, SiOC layer 2 and coating 3). ). This coating is an amorphous or slightly crystalline TiO that forms the inorganic binder of the coating.₂Includes particles or crystalline aggregates 5 between the aggregates. [0062] FIG. 2 is a photograph taken with a scanning electron microscope that gives information about the surface appearance of Example 4, especially with respect to Example 4. Here, the slightly rough surface provides a large developed surface area for the coating. [0063] It should be noted that Example 4 has a refractive index of about 1.65. In the first approximation, "bulk" TiO₂Assuming that the index of refraction of is 2.4, the porosity of the coating is considered to be about (2.4-1.65) / (2.4-1), or about 54%. The coating according to Example 4 also shows strong hydrophilicity. The catalyst angle ψ of water is measured regularly after being exposed to UVA rays for 20 minutes to activate and placed in the dark: this contact angle remains less than 10 ° in the dark for at least 20 days. is there. [0064] The following conclusions are drawn from the data: Examples 3, 4, 6 and 8 and in particular Ti have all the desired properties.₍₂₎/ Ti₍₁₎Example 5 has a ratio of 50/50. Here, the desirable properties are: High T_L, Low haze, and index of refraction less than 2. These give the coating a very favorable optical appearance; -Satisfactory photocatalytic activity that still exists even after a mechanical attack. This indicates the durability of the coatings and the acceptable "lifetime" allows these coatings to be used in real-life conditions, such as exterior glazing. These are, in fact, examples that still exhibit photocatalytic activity despite after a moderate 500 wear cycle. [0065] The second series of examples relates to the same type of coating with the same "solution 1" and the same "dispersion 2" as the main components. The adhesion conditions are the same as those of Examples 1 to 7 described above, except that the bath discharge time is high and the bath discharge time is 24 cm / min. Another difference is with respect to the substrate. Although the substrate is the same glass, it is pre-coated with a 50 nm first layer of SiOC adhered by CVD, and then fluorine-doped tin oxide F: SnO is subjected to powder pyrolysis by a known method.₂The second layer of 450 nm was attached. Furthermore, in the examples of this series, the amount Q of the photocatalytic coating does not measure its thickness, but the amount of material per unit area of the substrate (μg / cm).²(Represented by) is evaluated by measuring. [0066] The photocatalytic activity of the examples is measured prior to the wear test. That is, this is the above-mentioned ν1 value. The durability of the coating is qualitatively assessed by simply wiping it with a rug. Here, "++" means that the coating has very strong durability, "+" means that it still has appropriate durability, and "-" means wiped with a rug. Later, it means that the coating has been (almost) removed. [0067] Table 3 below relates to Examples 9-13, Ti₍₂₎/ Ti₍₁₎The ratio (same meaning as in Table 1), Q value, ν1 value and lag wiping evaluation are shown: [0068] [Table 3]<img file="JP4911376B2_D0003.tif" />[0069] The same trends as for the first series can be seen in this table. That is, if exactly the same or almost the same amount of coating is attached, Ti₍₂₎/ Ti₍₁₎Optimal results were obtained in Examples 11 and 12, where the ratios were 40/60 and 50/50. Only Example 12 exhibits more than 200 photocatalytic activity and modified durability. [0070] The third series of examples is the dispersion TiO used in all previous examples.₂Regarding coating with particles, TiO₂The SiO₂The hybrid binder blended in is used. [0071] The solution containing the precursor for the binder uses the following components: Solvent: Ethanol and ethylene glycol in mass ratio of 75/25; Stabilizer: Acetylacetone; TiO₂Precursor: Titanium tetrabutoxide (TBT); SiO₂Precursor: Tetraethyl orthosilicate (TEOS). [0072] The relative ratio of TBT to TEOS is TiO in solution₂/ SiO₂Adjusted to a mass ratio of 15/85 (all TPTs are TiO₂And all TEOS are SiO₂Will be converted to). [0073] This solution is then added to the particle dispersion used in the previous example at a desired ratio r, such that Ti particles / (Ti precursor + silicon precursor) are obtained. (The solid content of the solution is 3%). [0074] Adhesion and substrate conditions are the same as in Examples 9-13. [0075] Table 4 below shows the above-mentioned ratio r value, the above-mentioned velocity ν1 value, and the coating substrate.<u style="single">Reflection</u>Rate R_L(%), And T observed after 500 cycles of wear testing as described in the context of the first series of examples._LChange (ΔT_L), And the ratio of the amount of titanium (Ti) to the amount of silicon (Si) (based on the mass of oxides) r₁{r₁= TiO₂Particle / (TiO₂Binder + SiO₂Binder)} is shown. [0076] In addition, the table shows the total TiO in the coating.₂Q which is the quantity₁(TiO resulting from particles and titanium precursors₂) To μg / cm²Amount Q calculated in units and as the total mass of the coating₂Μg / cm²It is shown in units. [0077] [Table 4]<img file="JP4911376B2_D0004.tif" />[0078] By adjusting the solid content of the solution and the drainage rate, the ratio r was fixed at 55.3 / 44.7, and the amount of coating to be attached was changed, and the coating was repeated. [0079] Table 5 below shows<u style="single">Example 15</u>For an additional example from, the amount Q (μg / cm), as described above.²), Corresponding thickness e (nm) when measured, value of ν1 (nm / h), R_LAnd ΔT_LIndicates the value of. [0080] [0080] [Table 5]<img file="JP4911376B2_D0005.tif" />[0081] From the examples of this third series, SiO in the binder₂It turns out that it is advantageous to add the material. This material is not required for photocatalysts, but it helps to make the coating more uniform and increase durability. In addition, the ratio r is important, but other parameters are also required, preferably 15-45 μg / cm, considering both the cost of the coating and the effect of thickness on the optical appearance.²The value Q, which is, is especially important. [0082] Of course, the present invention is not limited to these particular examples. In particular, by introducing a dopant into the crystal lattice, or as described above in WO97 / 10185, including Fe, Cu, Ru, Mo, Bi, Ta, Nb, Co, Ni, Va and the like. It is also within the scope of the present invention to dope the particles by coating them with a type of dopant to further improve the photocatalytic activity of the particles 5. [0083] In addition, adding an inorganic binder containing an oxide that is not photocatalytic or has little photocatalytic activity in the crystalline state, eg, SiO such as tetraethoxysilane (TEOS).₂It is also within the scope of the present invention to add precursors for other oxides of the type to the dispersion. [0084] The above-mentioned A / (B + M + Si) ratio is optimally in the range of 40/60 to 60/40, but if the requirements are not strict, 35/65 to 40/60 and 65/35 to 60/ 40 can be considered. [Simple explanation of drawings] FIG. 1 is the present invention.<u style="single">of</u>The structure of the photocatalyst coating is shown. FIG. 2 is the present invention.<u style="single">of</u>Scanning electron microscope (SEM) on the surface of the photocatalytic coating<u style="single">) Photo</u>Is true.