Window glass having photocatalytic function

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention is a window having a highly active photocatalyst capable of imparting various performances such as air purification, antibacterial, antifouling, and antifogging to indoor space in windowpanes installed in hospitals, offices, houses, vehicles, and automobiles. It's about glass.

【0002】

[Conventional technology]

In recent years, antibacterial agents have been in the limelight from the viewpoint of public health. Among them, antibacterial agents using titanium oxide fine particles have high photocatalytic activity and excellent durability, and have already been put into practical use.

【0003】

Recently, especially in newly built houses, attention has been paid to the harmful effects of organic substances such as formaldehyde used as wallpaper adhesives on the human body, and the application of titanium oxide, which has excellent photocatalytic activity, to window glass is being studied. .. However, those using titanium oxide fine particles impair the transparency of the glass, and therefore cannot be applied to the window glass of a general house. Therefore, it is desired to use a titanium oxide film.

【0004】

Furthermore, if the purpose is to decompose harmful substances in the air inside the house, the titanium oxide film formed on the glass must be on the inside of the building, but the photocatalytic activity of titanium oxide is limited to ultraviolet light. Since ordinary glass absorbs a lot of ultraviolet light, it does not show sufficient photocatalytic activity. Therefore, as shown in Japanese Patent Application No. 8-245886, a film in which fluorine is added to titanium oxide to exhibit photocatalytic activity even in visible light has been studied.

【0005】

By the way, Japanese Patent Application No. 8-245886 states that it is desirable that the titanium oxide film has a film thickness of 50 to 200 nm in order to exhibit sufficient photocatalytic activity. However, when a titanium oxide film having such a thickness is formed on the glass, if the film thickness distribution of the titanium oxide film is not good, the reflectance and the reflected color distribution of the window glass seen from the outside of the building become large and the reflected color unevenness. As a result, there arises a problem that the commercial value of the window glass is significantly impaired.

【0006】

[Problems to be Solved by the Invention]

The present invention has been made to solve such a problem, and is a window glass exhibiting photocatalytic activity with small variation in reflectance, less uneven reflection color, and excellent aesthetics, and titanium oxide having a special photocatalytic function. The purpose is to obtain the film by a highly productive method without taking measures to improve the film thickness distribution.

【0007】

[Means for solving problems]

That is, the present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 has a photocatalytic function in which a titanium oxide film having a photocatalytic function is provided on one surface of a transparent glass substrate. In the window glass having the window glass, at least one transparent thin film is provided between the transparent glass substrate and the titanium oxide film having a photocatalytic function so as to reduce reflection interference color unevenness seen from the substrate side on the incident side of light. The reflected color a is within ± 5% of the change width of the visible light reflectance from the transparent glass substrate side.^*And b^*The change width of is a^*And b^*It is a window glass having a photocatalytic function within ± 5 of.

【0008】

The invention according to claim 2 is the invention according to claim 1, wherein the in-plane distribution of the titanium oxide film having a photocatalytic function is within ± 10% of the central film thickness. ..

【0009】

Further, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the transparent thin film is provided in order from the glass substrate side, the first layer thin film having a high refractive index and the second layer having a low refractive index. It is a transparent thin film composed of a layered thin film.

【0010】

Furthermore, the invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the first layer thin film has a refractive index of 1.8 to 2.5 and a film thickness of 10 to 45 nm. Is a thin film having a refractive index of 1.45 to 1.75 and a film thickness of 10 to 45 nm.

【0011】

The invention according to claim 5 is the invention according to claim 4, wherein the second layer thin film is a thin film containing silicon oxide as a main component.

【0012】

Further, the invention according to claim 6 is a thin film in which the first layer thin film contains tin oxide or titanium oxide as a main component in the invention according to claim 4.

【0013】

Furthermore, the invention according to claim 7 is the titanium oxide film in which the titanium oxide film having a photocatalytic function contains fluorine in the invention according to any one of claims 1 to 6.

【0014】

That is, by forming at least one thin film in which the refractive index and the film thickness are adjusted between the transparent glass substrate and the titanium oxide film having a photocatalytic function, the variation in reflectance is small, and the reflection interference color unevenness (hereinafter, reflection) It is to obtain a window glass showing photocatalytic activity with little aesthetics (expressed as color unevenness).

【0015】

Hereinafter, the present invention will be described in detail. The in-plane film thickness distribution, which causes uneven reflection color, is a problem related to any film constituting the window glass having a photocatalytic function, but is transparent formed between the transparent glass substrate and the photocatalytic functional film. Since the thin film is thinner than the photocatalytic functional film, the influence on the reflected color unevenness is small. Therefore, in the window glass having such a photocatalytic function, it is the state of the film thickness distribution of the photocatalytic functional film that affects the reflected color unevenness.

【0016】

If the in-plane distribution of the film thickness of the photocatalyst functional film exceeds ± 10% of the central film thickness, the reflected color unevenness becomes conspicuous due to the interference effect of light. Therefore, the in-plane distribution of the film thickness is ± 10 of the central film thickness. It is preferably within the range of%.

【0017】

As a method for forming the photocatalytic functional film, the CVD method described later is excellent in terms of economy and productivity, but the photocatalytic functional film obtained by this method does not necessarily have an excellent film thickness distribution when the film thickness is thick. Cannot be said to indicate. Therefore, in order to reduce the reflectance distribution and reflection color unevenness caused by the film thickness distribution of the photocatalyst functional film, one or more transparent thin films in which the refractive index and the film thickness are adjusted are provided between the transparent substrate and the photocatalyst functional film. I decided to set it up.

【0018】

In the present invention, the reason why the reflectance distribution and the unevenness of the reflected color are reduced is that one or more thin films, preferably two layers, in which the refractive index and the film thickness are adjusted are formed between the transparent substrate and the photocatalytic functional film. This is because the light interference effect of the multilayer thin film is adjusted.

【0019】

Therefore, when a two-layer thin film is provided between the transparent substrate and the photocatalytic functional film, a film having a high refractive index is first placed on the transparent substrate side and then a film having a low refractive index is placed on the transparent substrate side in order to suppress the light interference effect related to the uneven reflection color. It is preferable to provide a film having a refractive index.

【0020】

Further, the change width of the visible light reflectance from the transparent glass substrate side exceeds ± 5%, and the reflected color a^*And b^*The change width of is a^*And b^*If it exceeds ± 5 of, the unevenness of the reflected color will increase and the appearance will be spoiled. Therefore, the range of change in the visible light reflectance should be within ± 5% and the reflected color a^*And b^*The range of change must be within ± 5.

【0021】

As the transparent substrate, a transparent resin or the like can be considered, but when used for a window glass or the like of a house, a glass plate is desirable from the viewpoint of durability, impact resistance and the like.

【0022】

Examples of the thin film having a refractive index of 1.45 to 1.75 include silicon oxide, silicon oxide containing carbon and nitrogen, and a metal oxide film mainly composed of silicon and aluminum.

【0023】

However, judging from the viewpoint that film formation can be easily performed, silicon oxide and silicon oxide containing carbon and nitrogen are preferable when the CVD method described later is used.

【0024】

Examples of thin films having a refractive index of 1.8 to 2.5 include tin oxide, indium oxide, zinc oxide, and titanium oxide. However, in the CVD method, they are easily available, easily formed, and relatively inexpensive raw materials. From the point of view, tin oxide or titanium oxide is preferable.

【0025】

If the film thickness of these transparent thin films is less than 10 nm, uniform film formation is not performed on the transparent substrate, and the effect of reducing color unevenness may not be obtained. Moreover, if it exceeds 45 nm, a large amount of raw materials are required and the manufacturing cost increases. Further, in the case of a thin film having a slow film forming speed, if the thickness is thicker than 45 nm, it takes time, the productivity is deteriorated, and the manufacturing cost is increased. Therefore, in both the single-layer film and the two-layer film, the film thickness of each is preferably 10 to 45 nm.

【0026】

Further, as the photocatalytic functional film, titanium oxide to which fluorine is added is preferably used from the viewpoint of exhibiting photocatalytic activity even in visible light and the ease of obtaining raw materials by the CVD method.

【0027】

As a method for forming these thin films, so-called physical methods such as vacuum vapor deposition method, sputtering method, ion plating method using each metal and each metal oxide, and glass obtained by heating gaseous steam of each metal compound. Chemical vapor deposition (CVD) by spraying onto a substrate to form a film, spraying by spraying droplets of a solution of each metal compound onto a heated glass substrate, and powder spraying by spraying powder consisting of a metal compound. So-called chemical methods such as.

【0028】

Of these, the film formation by the physical method is excellent in the uniformity of the film thickness, but it is difficult to mass-produce because the cut glass is washed and the film is formed in the vacuum apparatus. In addition, the chemical method is preferable from the viewpoint of dealing with the increase in size of the glass substrate.

【0029】

In addition, among the chemical methods, the spray method has the advantage that film formation can be performed at low cost because the method is simple, but control of sprayed droplets and production of reaction products, undecomposed products, etc. that should be exhausted. Since it is difficult to control the object, it is difficult to obtain the uniformity of the film thickness, and the strain of the glass is also increased. From the above, the CVD method is more suitable as the thin film forming method.

【0030】

When each metal oxide film is formed by the CVD method, a glass substrate cut into a size of about 500 mm square is generally heated and a gaseous metal compound is sprayed to form a film. However, recently, when a window glass having a photocatalytic functional film on which various thin films are formed is used for a building or the like, it has become necessary to further increase the size of the glass substrate.

【0031】

When a large-area cut glass substrate is heated and a gaseous metal compound is sprayed to form a film, a large amount of heat energy required for heating is required. Therefore, when obtaining a window glass having a large-area photocatalytic functional film, it is possible to form a film on a high-temperature glass ribbon by the CVD method using the thermal energy at the time of glass molding from the viewpoint of manufacturing cost and quality. desirable.

【0032】

Furthermore, by performing this CVD method in the tin float tank space, there is a high possibility that the defect of film removal, which is generally called a pinhole, can be reduced. Further, a method of forming a transparent thin film such as tin oxide or silicon oxide by a CVD method and forming a titanium oxide film having a photocatalytic function by a spray method is also conceivable.

【0033】

As the silicon raw material of the silicon oxide formed by the CVD method, monosilane, disilane, trisilane, monochlorosilane, dichlorosilane, 1,2-dimethylsilane, 1,1,2-trimethyldisilane, 1,1,2,2 -Tetramethyldisilane and the like, examples of the oxidizing agent include oxygen, steam, dry air, carbon dioxide, carbon monoxide, nitrogen dioxide and the like.

【0034】

Further, when silane is used, unsaturated hydrocarbon gas such as ethylene, acetylene, and toluene may be added for the purpose of preventing oxidation until it reaches the glass surface and for controlling the refractive index of the obtained silicon oxide film. Absent.

【0035】

Examples of the aluminum raw material for the aluminum oxide include trimethylaluminum, aluminum triisopropoxyside, diethylaluminum chloride, aluminum acetylacetonate, and aluminum chloride.

【0036】

Examples of the titanium raw material of titanium oxide formed by CVD include titanium tetrachloride and titanium isopropoxide. Examples of the fluorine raw material to be added include hydrogen fluoride, trifluoroacetic acid, bromotrifluoromethane, chlordifluoromethane and the like.

【0037】

Titanium raw materials for titanium oxide formed by the spray method include titanium tetrachloride, titanium tetraethoxydo, acetylacetone titanyl, primary titanium sulfate, secondary titanium sulfate, titanium tetrabutoxide, titanium isopropoxyside, titanium methoxydo, and titanium. Diisopropoxybis octylene glycolide, titanium dinormal propoxybis octylene glycolide, titanium diisopropoxymonooctylene glycoxyacetylacetonate, titanium dinormalbutoxymonooctylene glycoxyacetylacetonate, titanium tetraoctylene glycoside Examples thereof include titanium, titanium dinormal propoxybisacetylacetonate, and the like.

【0038】

As tin compound raw materials used in the CVD method, tin tetrachloride, dimethyl tin dichloride, dibutyl tin dichloride, tetrabutyl tin, tetramethyl tin, dioctyl tin dichloride, monobutyl tin trichloride, etc. are used as oxidizing agents for obtaining tin oxide. Examples include oxygen, water vapor, and dry air.

【0039】

In addition to the above elements, silicon, aluminum, zinc, copper, indium, bismuth, gallium, boron, vanadium, manganese, zirconium, fluorine, antimony and the like may be appropriately added as long as the refractive index of the coating does not change significantly. ..

【0040】

The silicon oxide film, aluminum oxide film, etc. formed between the tin oxide film, which is a transparent conductive film, and the transparent substrate have the purpose of preventing sodium in the glass from invading the photocatalytic functional film and reducing the photocatalytic activity ( There is also a so-called alkaline barrier layer).

【0041】

In the window glass having a photocatalytic function of the present invention, a silicon oxide film, a tin oxide film, a titanium oxide film and the like are formed on a glass substrate by a CVD method, and then a titanium oxide film which is a photocatalytic function film is formed on the silicon oxide film, a tin oxide film, a titanium oxide film and the like. By controlling the film thickness of the silicon oxide, tin oxide, and titanium oxide films formed on the glass, the reflectance distribution and the reflection interference color unevenness are reduced. ..

【0042】

In addition, the refractive index distribution and the reflection interference color are controlled by controlling the refractive index of the undercoat layer formed between the photocatalytic functional film and the glass, instead of forming a thin film on the transparent substrate side on which the photocatalytic functional film is not formed. By controlling the film thickness, the window glass has a photocatalytic function with excellent productivity.

【0043】

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail below with reference to Examples and Comparative Examples.

【0044】

(Examples 1 and 2) Ordinary soda lime silica glass cut into a size of 450 × 450 mm was placed on a mesh belt and heated to about 570 ° C through a heating furnace.

【0045】

The glass was treated with a mixed gas of monobutyltin trichloride vapor, oxygen, water vapor and nitrogen as it passed under the first film forming nozzle to form a tin oxide film. Then, when passing under the next film forming nozzle, it was treated with a mixed gas composed of monosilane, oxygen and nitrogen, a film composed of silicon oxide was formed, and the glass was once taken out through a slow cooling step.

【0046】

After that, it is placed on a mesh belt again and heated to about 570 ° C through a heating furnace, and then when it passes under the multiple film forming nozzles, it is subjected to a mixed gas consisting of titanium isopropoxide, oxygen, nitrogen, and trifluoroacetic acid. It was treated to form a film made of titanium oxide. In the examples and comparative examples, the film thickness of each film was controlled by changing the concentration of the raw materials used.

【0047】

The obtained glass substrate was subjected to the photocatalytic activity, the film thickness and refractive index of each film, the film thickness range of the titanium oxide film having a photocatalytic function, the reflectance distribution of the obtained glass, the reflectance color distribution, and the like. The reflectance and the reflected color range were evaluated, and the values other than the photocatalytic activity evaluation are shown in Table 1. Reflected color Color unevenness was hardly observed.

【0048】

(Evaluation method of photocatalytic activity) The catalytic activity of the samples obtained in Examples 1 and 2 is coated with 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) on the surface and irradiated with light. It was investigated by a method for measuring the rate at which a catalyst photodecomposes TMCTS (Tada, Langmuir, Vol. 12, No. 4, pp. 966-971, 1996). UV / O the above sample₃After cleaning (50 ° C-10 minutes), it was set in a vacuum desiccator, depressurized to about 10 Torr with a vacuum pump, and then the internal temperature was maintained at 80 ° C. After closing the system, 200 μL of TMCTS was injected with a syringe and then heated for 30 minutes. Further, the unreacted TMCTS was cold trapped by raising the temperature to 100 ° C. and heating for 30 minutes while reducing the pressure with a vacuum pump. As a result, a TMCTS monolayer was formed on the various photocatalytic thin films of the above sample. The surface of the above sample, which had a hydrophilic surface, changed to water-repellent due to the formation of a TMCTS monolayer. By irradiating each sample at a distance of 20 cm with a 2 kW high-pressure mercury lamp as a light source in the vertical direction from the glass side, the methyl group of the TMCTS monomolecular film was oxidatively decomposed, and the hydrophilicity of the surface gradually increased. The higher the oxidative decomposition rate of the TMCTS monolayer, the higher the photocatalytic activity of the sample.

【0049】

When the decomposition rate of TMCTS of the samples of Examples 1 and 2 was examined, both were 0.02 (/ min) or more. From the results of Japanese Patent Application No. 8-245886, it can be said that this exhibits sufficient photocatalytic activity.

【0050】

(Measurement of Refraction Rate, Film Thickness and Film Thickness Distribution) In the film formation of the transparent thin film and the titanium oxide film having a photocatalytic function in Examples 1 and 2, only the single layer film was formed before and after the formation of these multilayer films. The film was formed to be formed, and the refractive index and film thickness of the transparent thin film and the film thickness distribution of the titanium oxide film having a photocatalytic function were determined.

【0051】

For example, in Example 1, ordinary soda lime silica glass having a thickness of 1 mm cut into a size of 450 × 450 mm is placed on a mesh belt and heated to about 570 ° C through a heating furnace, and below the film forming nozzle. The glass was treated with a mixed gas composed of monosilane, oxygen, and nitrogen to form a film mainly composed of silicon oxide, and the glass was taken out through a slow cooling step. Alternatively, ordinary soda lime silica glass with a thickness of 1 mm cut into a size of 450 × 450 mm is placed on a mesh belt, heated to about 570 ° C through a heating furnace, and then passed under the film forming nozzle. At that time, it was treated with a mixed gas composed of titanium isopropoxide, oxygen, nitrogen and trifluoroacetic acid, a film composed of titanium oxide was formed, and the glass was taken out through a slow cooling step.

【0052】

In this way, a glass on which only a single-layer film was formed was obtained, and the refractive index of the film at a wavelength of 633 nm was obtained from these films by ellipsometry. The refractive index values in Table 1 are obtained in this way. Regarding the coatings of silicon oxide and aluminum oxide, the film thickness was also determined by setting the extinction coefficient of the coating to 0 at the time of measurement by ellipsometry. In the case of tin oxide or titanium oxide, zinc powder was applied to a film masked with tape, the film was etched by pouring dilute hydrochloric acid over it, and the film thickness was determined using a stylus meter.

【0053】

When determining the film thickness distribution of a titanium oxide film having a photocatalytic function, select several points with different reflection colors from the glass surface with the film, and use a stylus meter in the same manner as above to coat the film. The film thickness of was determined.

【0054】

(Measurement of Reflectance and Reflective Color) In Examples 1 and 2, the reflectance and reflective color of the glass on which the titanium oxide film having a photocatalytic function was formed were measured by the following methods. The visible light reflectance of the obtained glass was measured according to JIS R 3106-1985, and the visible light reflection color was measured by a Hitachi 330-type spectrophotometer according to JIS Z 8722-1982.^*a^*b b^*Color system chromaticity index a^*b b^*The values in Table 1 were calculated from. Visible light reflectance and a^*b b^*The maximum and minimum values of the distributed values were determined by measuring the in-plane reflectance and the reflected color of the glass at different positions.

【0055】

[table 1]

----------------------------------- 1st layer 2nd layer TiO2 reflectance Reflective color distribution Refractive index film thickness Refractive index film thickness film thickness range distribution Oxide (nm) Oxide (nm) (nm) (%) a^* b b^*----------------------------------- Example 1 Sn 2.02 25 Si 1.46 25 63 ~ 77 ± 1.5 ± 1.5 ± 3.5 Example 2 Sn 2.02 25 Si 1.46 25 72 ~ 88 ± 3.0 ± 0.5 ± 2.5 Example 3 Sn 2.02 25 Si 1.65 25 63 ~ 77 ± 2.5 ± 0.5 ± 2.0 Example 4 Sn 2.02 25 Si 1.65 25 72 ~ 88 ± 2.0 ± 1.0 ± 1.0 Example 5 Ti 2.37 15 Si 1.65 25 72 ~ 88 ± 2.0 ± 1.5 ± 3.0 Example 6 Ti 2.37 15 Si 1.46 25 72 ~ 88 ± 2.5 ± 1.0 ± 2.0 ----------------------------------- Comparative Example 1 Si 1.46 50 63 ~ 77 ± 3.5 ± 1.0 ± 13.0 Comparative Example 2 Si 1.65 75 63 ~ 77 ± 3.0 ± 1.0 ± 8.0 Comparative Example 3 Sn 2.02 25 Si 1.65 50 63 ~ 77 ± 1.0 ± 3.5 ± 10.5 Comparative Example 4 Ti 2.37 15 Al 1.79 20 72 ~ 88 ± 2.0 ± 2.0 ± 9.0 Comparative Example 5 Si 1.46 25 Sn 2.02 25 72 ~ 88 ± 5.5 ± 9.5 ± 12.5 ----------------------------------- ----------------------------------- 1st layer 2nd layer TiO2 reflectance Reflective color Refractive index film thickness Refractive index film thickness film thickness range range range Oxide (nm) Oxide (nm) (nm) (%) a^* b b^*----------------------------------- Example 1 Sn 2.02 25 Si 1.46 25 63 ~ 77 20 ~ 23 -1 ~ 2-2 ~ 5 Example 2 Sn 2.02 25 Si 1.46 25 72 ~ 88 16 ~ 22 -1 ~ 0 3 ~ 8 Example 3 Sn 2.02 25 Si 1.65 25 63 ~ 77 17 ~ 22 2 ~ 3-1 ~ 3 Example 4 Sn 2.02 25 Si 1.65 25 72 ~ 88 15 ~ 19 1 ~ 3 1 ~ 3 Example 5 Ti 2.37 15 Si 1.65 25 72 ~ 88 13 ~ 17 6 ~ 9-12 -6 Example 6 Ti 2.37 15 Si 1.46 25 72 ~ 88 14 ~ 19 5 ~ 7 -6 ~ -2 ----------------------------------- Comparative Example 1 Si 1.46 50 63 ~ 77 27 ~ 34 -7 ~ -5 4 ~ 30 Comparative Example 2 Si 1.65 75 63 ~ 77 22 ~ 28 -4 ~ -2 2 ~ 18 Comparative Example 3 Sn 2.02 25 Si 1.65 50 63 ~ 77 24 ~ 26 -9 ~ -2-13 ~ 8 Comparative Example 4 Ti 2.37 15 Al 1.79 20 72 ~ 88 12 ~ 16 11 ~ 15-19 -1 Comparative Example 5 Si 1.46 25 Sn 2.02 25 72 ~ 88 12 ~ 23 -1 ~ 18 -1 ~ 24 ----------------------------------- [0056]

(Examples 3 to 4) Ordinary soda lime silica glass was melted in a float kiln, and the molten substrate was poured into a tin tank to form a plate. This flat glass was transported to a thickness of 3 mm. The space on the glass of the tin tank was composed of 98% by volume of nitrogen and 2% by volume of hydrogen, and was held at a slightly positive pressure from the surroundings to maintain a non-oxidizing atmosphere.

【0057】

The plate-shaped glass is treated with a mixed gas consisting of vapor of dimethyltin dichloride, oxygen, water vapor, helium, and nitrogen when passing under the plurality of film forming nozzles in the first half in the tin tank, at which time tin oxide is formed. A coating consisting of was formed. Then, when passing under the plurality of film forming nozzles in the latter half, it was treated with a mixed gas composed of monosilane, ethylene, oxygen and nitrogen to form a film made of silicon oxide.

【0058】

After passing through the outlet of the float section, the glass was sprayed with a solution containing a mixture of acetylacetone titanyl, trifluoroacetic acid, toluene, xylene and alcohol by a spray method to form a film made of titanium oxide. After that, it entered the slow cooling section, and was cut into a glass plate having a size of 450 mm × 450 mm in the cutting step through the slow cooling step.

【0059】

The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1. Reflected color No color unevenness was observed. Regarding the photocatalytic activity, when the decomposition rate of TMCTS of the samples of Examples 3 to 4 was examined, both were 0.02 (/ min) or more as in Example 1, and it could be said that they showed sufficient photocatalytic activity.

【0060】

(Example 5) Ordinary soda lime silica glass cut into a size of 450 × 450 mm was placed on a mesh belt and heated to about 570 ° C through a heating furnace. The glass was treated with a mixed gas of titanium isopropoxide, oxygen and nitrogen as it passed under the first film forming nozzle to form a coating of titanium oxide. When passing under the next film forming nozzle, it was treated with a mixed gas composed of monosilane, oxygen, and nitrogen to form a film made of silicon oxide, and the glass was once taken out through a slow cooling step.

【0061】

After that, it is placed on a mesh belt again and heated to about 570 ° C through a heating furnace, and then when it passes under the multiple film forming nozzles, it is subjected to a mixed gas consisting of titanium isopropoxide, oxygen, nitrogen, and trifluoroacetic acid. It was treated to form a film made of titanium oxide. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1. Reflected color Color unevenness was hardly observed. As for the photocatalytic activity, it showed sufficient photocatalytic activity as in Example 1.

【0062】

(Example 6) Ordinary soda lime silica glass cut into a size of 450 × 450 mm was placed on a mesh belt and heated to about 570 ° C through a heating furnace. The glass was treated with a mixed gas of titanium isopropoxide, oxygen and nitrogen as it passed under the first film forming nozzle to form a coating of titanium oxide. When passing under the next film forming nozzle, it is treated with a mixed gas composed of monosilane, ethylene, oxygen, and nitrogen to form a film composed of silicon oxide, and once the glass is taken out through a slow cooling step, it is again performed. After being placed on a mesh belt and heated to about 570 ° C through a heating furnace, it is treated with a mixed gas consisting of titanium isopropoxide, oxygen, nitrogen, and trifluoroacetic acid as it passes under multiple film forming nozzles, and is oxidized. A film made of titanium was formed. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1. Reflected color No color unevenness was observed. As for the photocatalytic activity, it showed sufficient photocatalytic activity as in Example 1.

【0063】

(Comparative Example 1) Ordinary soda lime silica glass cut to a size of 450 × 450 mm was placed on a mesh belt and heated to about 570 ° C through a heating furnace. When this glass passes under the first film forming nozzle, it is treated with a mixed gas composed of monosilane, oxygen, and nitrogen to form a film mainly composed of silicon oxide, and after the glass is once taken out through a slow cooling step. After being placed on the mesh belt again and heated to about 570 ° C through a heating furnace, it is treated with a mixed gas consisting of titanium isopropoxide, oxygen, nitrogen, and trifluoroacetic acid when passing under the multiple film forming nozzles. A film made of titanium oxide was formed. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are as shown in Table 1, and strong reflection color unevenness was observed.

【0064】

(Comparative Example 2) At the time of the first silicon oxide film formation, a silicon oxide and titanium oxide film was formed in the same manner as in Comparative Example 1 except that monosilane, ethylene, oxygen and nitrogen were used as the mixed gas. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1, and similar to Comparative Example 1, strong color unevenness of the reflected color was observed.

【0065】

(Comparative Example 3) Tin oxide, silicon oxide, and titanium oxide film were formed in the same manner as in Example 1 except that monosilane, ethylene, oxygen, and nitrogen were used as the mixed gas during the film formation of silicon oxide in the second layer. It was. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1, and similar to Comparative Example 1, strong color unevenness of the reflected color was observed.

【0066】

(Comparative Example 4) Ordinary soda lime silica glass cut into a size of 450 × 450 mm was placed on a mesh belt and heated to about 570 ° C through a heating furnace. The glass was treated with a mixed gas of titanium isopropoxide, oxygen and nitrogen as it passed under the first film forming nozzle to form a coating of titanium oxide. When passing under the next film forming nozzle, it is treated with a mixed gas consisting of aluminum isopropoxide, oxygen, and nitrogen to form a film made of aluminum oxide, and once the glass is taken out through a slow cooling step, it is taken out again. After being placed on a mesh belt and heated to about 570 ° C through a heating furnace, it is treated with a mixed gas consisting of titanium isopropoxide, oxygen, nitrogen and trifluoroacetic acid as it passes under multiple film forming nozzles. A film made of titanium oxide was formed. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1, and similar to Comparative Example 1, strong color unevenness of the reflected color was observed.

【0067】

(Comparative Example 5) Ordinary soda lime silica glass cut to a size of 450 × 450 mm was placed on a mesh belt and heated to about 570 ° C through a heating furnace. The glass was treated with a mixed gas of monosilane, oxygen and nitrogen as it passed under the first film formation nozzle to form a film of silicon oxide. When passing under the next film forming nozzle, it is treated with a mixed gas consisting of steam, oxygen, water vapor, and nitrogen of monobutyltin trichloride, a film made of tin oxide is formed, and the glass is taken out once through a slow cooling step. After that, it is placed on a mesh belt again and heated to about 570 ° C through a heating furnace, and then when it passes under the multiple film forming nozzles, it is a mixed gas composed of titanium isopropoxide, oxygen, nitrogen, and trifluoroacetic acid. A film made of titanium oxide was formed. The same evaluation as in Example 1 was performed using the obtained glass substrate. The results are shown in Table 1, and similar to Comparative Example 1, strong color unevenness of the reflected color was observed.

【0068】

Regarding the photocatalytic activity of Comparative Examples 1 to 5, the photocatalytic activity was sufficient as in Example 1.

【0069】

[Effect of the invention]

According to the present invention, there is a means for improving the film thickness distribution of a titanium oxide film having a special photocatalytic function for a window glass having a photocatalytic function having a small variation in reflectance and excellent aesthetics with little unevenness in reflected color. It can be provided at low cost without taking any measures.