JPH1160281A - Photocatalyst glass and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photocatalyst glass prevented in the diffusion of Na ions from the glass, capable of sufficiently exhibiting the function of the photocatalyst and capable of persisting duration properties such as hot warm water, moisture, alkali and warm salt water resistances over a long period by forming a SiO2 coating film containing Al2 O3 and subsequently a coating film containing TiO2 as a main component on the surface of a soda lime glass substrate. SOLUTION: This photocatalyst glass is obtained by forming a SiO2 coating film containing Al2 O3 preferably in an amount of 1-80 wt.% and subsequently a coating film containing TiO2 as a main component preferably in a TiO2 content of 10-100 wt. % and preferably further containing one or more kinds of metal oxides selected from SiO2 , Al2 O3 , P2 O5 , B2 O3 , ZrO2 , SnO2 and Ta2 O5 on the surface of a soda lime glass substrate. The glass can be produced by applying a coating solution comprising a SiO2 solution containing Al on the surface of a soda lime glass substrate, applying a solution comprising a mixture sol containing a TiO2 precursor and/or TiO2 on the coating film, drying the coating films and subsequently baking the dried coating films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalytic glass used for window materials for buildings, automobiles and the like, and glass articles in various fields such as mirrors, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, a film having a photocatalytic function has been formed on a glass surface for antifouling, deodorizing, antibacterial, hydrophilic, and the like. For example, a plate-like member which is adapted a part photocatalyst fine powder mainly comprising anatase TiO ₂ described in JP-A-5 over 253,544 are exposed from the binder layer surface described in Japanese Patent Laid-Open No. 7-232080 Are fine particles of TiO ₂ , ZnO, SrTiO ₂ , Fe ₂ O ₃ , W
O ₃ , FeTiO ₂ , Bi ₂ O ₃ , SnO _2, etc., and the gap filling particles of the photocatalyst particles are Sn, Ti, Ag, Cu, Zn, Fe, P
t, Co, multifunctional material having a photocatalytic function is a metal or an oxide of Ni, average crystal grain size of the photocatalytic Hei 9-59042 JP contains about 0.1μm or less of the TiO ₂ particles A transparent substrate or the like covered with an antifogging film is known.

Conventionally, when coating various functional films on a glass surface, an undercoat film is formed under the functional film in order to prevent diffusion of sodium ions from the glass to the functional film. It has been known. For example, surface-treated glass having a metal oxide film containing SiO ₂ as a main component in the lower layer of the ultraviolet absorbing film containing ZnO of JP-A 4-18237 JP, a glass plate of JP-A 7-315880 JP On the surface, a thin film mainly composed of SiO ₂ , T
iO ₂ as main components a thin film, the transparent conductive film-attached glass plate is sequentially coated film on the basis of SnO _2, JP-A-8-1
No. 90088 discloses a glass article or the like comprising a metal oxide barrier layer for preventing diffusion of alkali metal ions from a glass substrate and a metal-containing coating on the barrier layer.

[0004]

In the above-mentioned conventional photocatalytic glass in which a photocatalytic film is formed on glass, when the photocatalytic film is directly coated on the glass surface, if the treatment is performed at a high temperature, sodium ions contained in the glass are removed. diffused into the photocatalyst film, will neutralize the electrons to accelerate the oxidation of the TiO ₂ photocatalyst film, the above-described photocatalytic function is a drawback that impairs.

When an SiO ₂ film as an undercoat layer is coated under the photocatalytic film, the photocatalytic film and the S
Adhesion with the SiO ₂ film was not sufficient, and the photocatalytic film peeled off in a durability evaluation test.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and as a result of various studies on the composition of the undercoat layer, Al ₂ O was found in the undercoat film.
_{By including 3} , the denseness of the film is increased. As a result, in endurance tests such as warm water resistance and salt warm water resistance, the dissolution of SiO ₂ in the film is prevented, and the adhesion strength between the undercoat layer and the photocatalytic film is significantly improved while maintaining alkali barrier properties. It has also been found that alkali barrier properties do not decrease even if the glass is subjected to high temperature treatment such as thermal processing after film formation.

According to the present invention, a SiO ₂ film containing Al ₂ O ₃ is formed as a first layer on the surface of a soda lime glass substrate, and a film mainly composed of TiO ₂ is formed as a second layer thereon. It relates to a coated photocatalytic glass.

The content of Al ₂ O ₃ in the first layer is 1
The content is preferably from 80 to 80% by weight, more preferably from 5 to 60% by weight.

Further, when the content of TiO _{2 in} the second layer is 10
It is preferably from 100 to 100% by weight. Further, components other than TiO ₂ in the second layer include SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ ,
At least one of B ₂ O ₃ , ZrO ₂ , SnO ₂ and Ta ₂ O ₅
Preferably, it is a kind of metal oxide. When SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ , and B ₂ O ₃ are used among these metal oxides, they function as network-forming oxides, and ZrO ₂ , Sn
When O ₂ or Ta ₂ O ₅ is used, the denseness of the film increases,
As a result, the film strength is improved. Further, ZrO ₂ has excellent alkali resistance, SnO ₂ makes it possible to impart conductivity to the film, and Ta ₂ O ₅ does not contribute to the photoexcitation of TiO _2.
There are advantages such as the ability to cut off ultraviolet light near 0 nm.

Further, the film thickness of the first layer and the second layer is
It is suitable that each is 50 to 500 nm. Also,
The present invention is directed to a second layer made of a mixed sol containing a TiO ₂ precursor and / or TiO ₂ after coating a coating solution composed of a SiO ₂ solution containing Al as a first layer on a surface of a soda lime glass substrate. The present invention relates to a method for producing a photocatalytic glass obtained by applying a solution for use, drying and firing.

The first layer coating solution is preferably composed of a hydrolyzate of an alkoxysilane compound containing a nitrate, an organic acid salt, an acetylacetonate compound and an alkoxide compound of an Al element.

Further, when the starting material of TiO ₂ in the second layer is crystalline fine particles, the content of TiO _{2 in} the second layer is 1%.
It is preferably from 0 to 90% by weight, more preferably from 20 to 80% by weight.

When the solution of TiO ₂ in the second layer is a starting material, the content of TiO _{2 in} the second layer is 50 to 10%.
It is preferably 0% by weight, more preferably 70 to 100% by weight.

[0014]

DETAILED DESCRIPTION OF THE INVENTION A photocatalytic glass formed on a glass surface and comprising a first layer as an undercoat and a second layer as a photocatalytic function is obtained as follows.

The soda-lime glass substrate is a common plate glass or so-called float plate glass which is generally used for automobiles and architectural glass, etc., and various colored glass such as clear, green and bronze, and various functional glasses. Needless to say, it can be used as a tempered glass, a glass similar thereto, a laminated glass, a double-glazed glass, and various flat glass products such as a flat plate or a bent plate.
The thickness is, for example, about 1.0 mm or more and about 12 mm.
About 2.0 mm or more and about 10 mm or less for architectural use and about 1.5 m for automobile use.
The glass is preferably about m or more and about 6.0 mm or less, more preferably about 2.0 mm or more and about 5.0 mm or less.

A first layer of SiO ₂ film and a second layer of TiO ₂
The main raw material of the film is the above-mentioned metal alkoxides. Specific examples include Si alkoxides such as tetraethoxysilane, tetramethoxysilane, monomethyltriethoxysilane, monomethyltrimethoxysilane, dimethyldimethoxysilane and dimethyldimethoxysilane. As ethoxysilanes, other tetraalkoxysilane compounds, other alkylalkoxysilane compounds, and Ti alkoxides, tetraisopropoxytitanium, tetranormal butoxytitanium, triisopropoxytitanium monoacetylacetonate, and the like can be used.

Further, the Al element added to the first layer includes metal alkoxides, acetylacetonates, nitrates,
At least one of the organic acid salts can be used;
The first layer is used as a mixture with a hydrolyzate of alkoxysilanes, which is a raw material of SiO ₂ .

The diluting solvent is preferably an alcoholic solvent, and specific examples thereof include methanol and ethanol.
, Ethanol, propanol, butanol, ethylene glycol, hexylene glycol, and esters such as ethyl acetate, butyl acetate, and amyl acetate; further, methyl cellosolve, ethyl cellosolve, butyl cellosolve, and the like. Cellosolves and their mixed solvents, as well as polyethylene glycol (average molecular weight 200) and polypropylene glycol (average molecular weight 4
00) or the like, or an appropriate amount of a methyl silicone such as dimethyl silicone or a fluorine-based leveling agent as a leveling agent. Alcohols or cellosolves, which are originally contained in the solution, alone or as a mixture,
The solution may be selected in consideration of the evaporation rate of the solution and the viscosity of the film.

Further, the content of Al ₂ O ₃ in the first layer is 1 to
It is preferably 80% by weight, and if it is 80% by weight or more, the photoactivity is remarkably reduced due to the reduction of the Na ion barrier effect of the first layer undercoat film, and the alkali resistance is also remarkably reduced. . If the content is less than 1% by weight, the adhesion of the photocatalyst film is reduced.

[0020] Incidentally, TiO ₂ as the TiO ₂ precursor of the second layer, which is hydrolyzed by adding water to the acetylacetonates of the added stabilizer Ti alkoxides solution or Ti
Sol or Ti acetylacetonates, TiCl ₄ ,
It is a solution in which Ti (SO ₄ ) ₂ or the like is dissolved in various solvents.

In the mixed sol containing TiO ₂ , the TiO ₂ precursor may be made of SiO ₂ , Al ₂ O ₃ , P other than TiO _2.
A mixture of at least one of metal oxides such as ₂ O ₅ , B ₂ O ₃ , ZrO ₂ , SnO ₂ and Ta ₂ O _5;
It is a TiO ₂ mixed sol or the like in which TiO ₂ crystalline or amorphous TiO ₂ fine particles are dispersed in the metal oxide sol using a dispersant or the like.

The content of TiO _{2 in} the second layer is 10 to 10
0% by weight is preferable, and oxides other than TiO ₂ include S
_{iO 2, Al 2 O 3,} P 2 O 5, B 2 O 3, ZrO 2, SnO 2, Ta
₂ O ₅ or the like can be used. In particular, SiO ₂ is preferable from the viewpoint of film strength.

When the TiO ₂ in the second layer is crystalline fine particles, the content of the TiO ₂ is preferably 10 to 90% by weight, and when it is 10% or less, the photoactivity is remarkably reduced. % Or more, the film strength and film formability are reduced.

Further, when TiO ₂ in the second layer starts from a solution, the content of TiO ₂ is preferably from 50 to 100% by weight, and if it is less than 50%, the photoactivity is remarkably reduced. is there.

The coating method is not particularly limited, but from the viewpoint of productivity and the like, for example, a spin coating method or a dip coating method, a reverse coating method, a flexographic printing method, and other methods. Roll coating method,
Further, a nozzle coating method, a spray coating method, a screen printing method and the like can be appropriately employed. The solid content concentration in the coating liquid when forming a coating film by these coating methods is about 1 to 30% by weight, and the coating liquid viscosity is 1 to 100%.
cP is preferred.

Further, the drying treatment after the application of the first and second layers is preferably performed at a drying temperature of about normal temperature to about 300 ° C. and a drying time of about 0.5 to 60 minutes, more preferably the drying temperature. But the drying time is about 100-250 ° C
It is about 1 to 30 minutes. The baking treatment after the drying of the second layer is preferably performed at a baking temperature of about 400 to 700 ° C. and a baking time of about 1 to 30 minutes. Preferably, the heat strengthening and / or hot bending of the glass is performed at a temperature of about 550 to 700 ° C. for a time of about 0.5 to 500 ° C.
More preferably, it is performed for about 10 minutes.

The film composition of the present invention comprises the above-mentioned 5
Even when heat strengthening and / or hot bending at a high temperature of 50 ° C. or more is performed, there is an advantage that alkali does not diffuse from glass and alkali barrier properties do not decrease.

The thickness of the first layer is about 50 to 500 nm, and if it is less than 50 nm, the photocatalytic function of the second layer is reduced by the influence of Na ions from the glass substrate,
It is because it is economically useless if it exceeds the number, and it becomes a factor of the appearance of cracks. More preferably, about 70 to 130
nm.

The thickness of the second layer is preferably about 50 to 500 nm, though it depends on the content of TiO ₂ . More preferably, it is 70 to 150 nm. If the thickness is 50 nm or less, sufficient photoactivity cannot be obtained, and if the thickness is 500 nm or more, the photoactivity cannot be improved, the film strength is reduced, and cracks are generated. More preferably, it is 70 to 150 nm.

As described above, the film composition of the present invention has an advantage of sufficiently exhibiting the functions of alkali barrier properties and photoactivity even when the film thickness is small. By providing a SiO ₂ film containing Al ₂ O ₃ as a first layer under the _second photocatalytic film, diffusion of sodium ions from the soda lime glass substrate into the film is prevented, and the photocatalytic function is improved. In addition to fully exhibiting, the adhesion strength between the first layer and the second layer is strengthened, and the durability such as hot water resistance, moisture resistance, alkali resistance, and hot salt water resistance is improved. It is a photocatalytic glass of more reliable and stable quality that withstands long-term use.

[0031]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to these examples.

[0032]

Example 1 2 g of tetraethoxysilane, aluminum nitrate
1g of SiO 9_Two/ Al_TwoO_Three= 80 _/20 weight ratio), water
0.7 g of water for decomposition, 0.06 g of 60% nitric acid as a catalyst, and
Mix and stir 40 g of ethanol as a diluting solvent.
Solution. This is a 10cm square saw with a thickness of 2mm
A film is formed on a Dali lime silica glass substrate with a spin coater,
After drying at 250 ° C. for 5 minutes and cooling to room temperature, the second layer
Eyes were also formed with a spin coater. The second layer
The coating solution was titania sol: Atron NTi-
8g 500 (manufactured by Nippon Soda) and silica sol solution CSG-D
3.3 g of I-0600 (manufactured by Chisso) were mixed (TiO 2_Two/ Si
O_Two= 80/20 weight ratio), diluted 4 times with ethanol
Was used. After forming the second layer, dry at 250 ° C for 5 minutes
After pre-baking at 500 ° C for 5 minutes,
By performing the firing, the film thickness of both the first layer and the second layer is reduced.
A 100 nm photocatalytic film was obtained.

[0033]

Example 2 10 g of titania sol: Atron NTi-500 was applied to the second layer coating solution with ethanol.
The procedure was the same as in Example 1, except that a one-fold dilution was used. The thickness of the obtained second layer TiO ₂ film was 90 nm.

[0034]

EXAMPLE 3 tetraethoxysilane 1.3g, aluminum nitrate nonahydrate _{2.8g (SiO 2 / Al 2 O} 3 = 50/50 by weight), water O.7g for hydrolysis, 60 as a catalyst 0.06% nitric acid
g, and the same procedure as in Example 1 except that 46 g of ethanol as a diluting solvent was mixed and stirred and used as a coating solution for the first layer. The thickness of the obtained first layer was 100 nm.

[0035]

Example 4 Silica sol solution CSG-DI-0600
A 2 g alumina sol (SiO ₂ / Al ₂ O ₃ = 90/10 weight ratio) prepared in advance and mixed with 18 g (manufactured by Chisso Corporation) and diluted with ethanol three-fold was used as the first layer coating solution. Except for this, it was the same as Example 1. The alumina sol was stabilized by mixing 10.5 g of isopropyl alcohol and 6 g of aluminum-sec-butoxide with 3 g of ethyl acetoacetate, and then hydrolyzing H ₂ O.
0.5 g was obtained by mixing and stirring. First layer SiO ₂ -Al ₂
An O ₃ film having a thickness of 100 nm was obtained.

[0036]

Example 5 Silica sol solution CSG-DI-0600
Aluminum nitrate 9 hydrate 1 in 20 g (manufactured by Chisso)
0 g (SiO ₂ / Al ₂ O ₃ = 30/70 weight ratio) was added, mixed and stirred, and diluted 4 times with ethanol to obtain a coating solution for the first layer.
ST-K03 (Ishihara Techno Co., Ltd.) (TiO ₂ / SiO ₂ = 50/50)
(Weight ratio) diluted 5 times with ethanol was used in the same manner as in Example 1 except that the coating solution for the second layer was used. The thickness of the obtained first layer SiO ₂ —Al ₂ O ₃ film is 100 nm.
The thickness of the second layer was 150 nm.

[0037]

[Comparative Example 1] Sol-gel solution of silica CSG-DI-O6
The same procedure as in Example 1 was carried out except that OO (manufactured by Chisso, solid content concentration: 6% by weight) was used as the coating solution for the first layer. The obtained first SiO ₂ film had a thickness of 100 nm.

[0038]

Comparative Example 2 Sol-gel solution of silica CSG-DI-O6
Example 1 was repeated except that 4 g of titania sol prepared in advance was mixed and stirred with 16 g of OO (SiO ₂ / TiO ₂ = 80/20 weight ratio), and a three-fold dilution with ethanol was used as the first layer coating solution. The same as above. The titania sol was obtained by mixing and stirring 9 g of isopropyl alcohol and 3 g of titanium-iso-propoxide with 1 g of acetylacetone, and then mixing and stirring 0.2 g of H ₂ O for hydrolysis. The thickness of the obtained first-layer SiO ₂ —TiO ₂ film was 100 nm.

[0039]

Comparative Example 3 Silica Sol Solution CSG-DI-0600
(Manufactured by Chisso Corporation) 16g previously prepared zirconia sol _{4g (SiO 2 / Zr0 2 =} 80/20 weight ratio) mixture was stirred, to a diluted to 3 times with ethanol and the coating solution of first layer Except for the above, it was the same as Example 1. The zirconia sol was stabilized by mixing 1 g of acetylacetone with 15 g of isopropyl alcohol and 4 g of zirconium-n-butoxide, and then 0.2 g of H ₂ O for hydrolysis.
Was obtained by mixing and stirring. The obtained first layer SiO ₂ —Zr
The thickness of the O ₂ film was 100 nm.

The obtained photocatalytic glass was evaluated as follows. [Photoactivity test] Using a 1% by weight acetone solution of oleic acid, oleic acid was uniformly adhered to the surface of the photocatalyst film to artificially form stains. Black Light F15T8BL
B (Sankyo Denki) was irradiated with 0.5 mW / cm2 (365 nm) of ultraviolet light for 2 hours. The photoactivity was evaluated by the change in the contact angle of water before and after irradiation. [Water resistance test] The film was immersed in warm water at 60 ° C. for 10 days to evaluate changes in appearance and film strength (examination of film peeling by rubbing strongly with a gauze cloth in warm water). [Moisture resistance test] The composition was allowed to stand in steam at 50 ° C and a relative humidity of 98% for 30 days to evaluate changes in appearance and film strength. [Acid resistance test] The specimen was immersed in 0.1% hydrochloric acid at room temperature for 48 hours to evaluate changes in appearance and film strength. [Alkali Resistance Test] The film was immersed in a 20% aqueous sodium carbonate solution at room temperature for 48 hours to evaluate changes in appearance and film strength. [Warm salt water resistance test] The specimen was immersed in a 3% saline solution at 60 ° C for 48 hours to evaluate changes in appearance and film strength.

Table 1 shows the performance evaluation results in the examples and comparative examples. In the photoactivity test, oleic acid is attached as an artificial soil, and the higher the photocatalytic function, the more the soil can be decomposed. That is, the smaller the contact angle after ultraviolet irradiation, the higher the photoactivity. Example 1
5 and Comparative Example 1 had a contact angle of water of 40 before ultraviolet irradiation.
What was about 55 ° was significantly reduced to about 2 to 6 ° after irradiation. From these results, in Examples 1 to 5 and Comparative Example 1, since the alkali barrier effect of the first layer was sufficiently functioning, the film having TiO ₂ of the second layer was a good photocatalyst. It can be confirmed that it has a photoactive function. On the other hand, in Comparative Examples 2 and 3, it can be confirmed that the photocatalytic performance is reduced as compared with the other cases, although there is photoactivity.

With respect to the warm water resistance test, Examples 1 to 5 and Comparative Examples 2 to 3 showed no change in appearance and film strength even after 10 days. In Comparative Example 1, the second layer film was peeled off on the second day.

In the moisture resistance test, no change was observed after 30 days in Examples 1 to 5 and Comparative Examples 2 to 3, whereas in Comparative Example 1, the second layer film was peeled off on the 12th day. . Regarding the acid resistance test, no change was observed in both the examples and the comparative examples.

With respect to the alkali resistance test, Examples 1 to
5 and Comparative Examples 2-3 did not change at all after 48 hours. On the other hand, in Comparative Example 1, the second layer film was peeled off after 11 hours. In the warm salt water resistance test, in Examples 1 to 5 and Comparative Examples 2 to 3, no change was observed even after 48 hours, whereas in Comparative Example 1, the second layer film was peeled off after 5 hours.

In Table 1, (○) indicates that there was no change after the test and good results were obtained, and (×)
Indicates that the film was peeled off during the test. As shown in the above evaluation results, Examples 1 to 5 of the present invention are Comparative Examples 1 to 3.
In comparison with the above, all the evaluation items of photoactivity, warm water resistance, moisture resistance, alkali resistance, and salt water resistance are extremely excellent, and the adhesion strength between the first layer film and the second layer film is extremely large and strong. In addition, it was found that the alkali barrier effect was sufficient. On the other hand, in Comparative Examples 2 and 3, better results were obtained in the durability test of hot water resistance, moisture resistance, alkali resistance, and hot salt water resistance than Comparative Example 1, and even though they had photocatalytic performance, they were irradiated with ultraviolet light. The contact angle afterward is 10 to 2 compared to the embodiment.
Since it is higher by about 0 °, the photoactivity is reduced, and it can be seen that the alkali barrier property is inferior to that of the examples.

[0046]

By the lower layer of the photocatalytic film according to the present invention providing the Al ₂ 0 ₃ -SiO ₂ film to prevent diffusion of sodium ions from a soda lime glass substrate to the photocatalyst film, with sufficiently exhibit the photocatalytic function, the When the Al element added to one layer interacts with the Ti element of the photocatalytic film as the second layer, the adhesion strength between the first and second layers is strengthened, and the warm water resistance, moisture resistance, Long-lasting durability, such as alkali resistance and hot salt water resistance, can provide photocatalytic glass of reliable and stable quality in harsh environments, and is widely used in various other glass articles such as construction, vehicles, mirrors, etc. Can be used.

Further, the present invention has an advantage in that even if heat strengthening and / or hot bending is performed at a high temperature of 550 ° C. or more after film formation, alkali does not diffuse from glass and alkali barrier properties do not decrease.

Further, the present invention has an advantage that the alkali barrier property and the photoactive function can be sufficiently exhibited even if the first and second layers are thin.

[0049]

[Table 1]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiji Honjo 1510 Oguchicho, Matsusaka-shi, Mie Central Glass Co., Ltd.

Claims (9)

[Claims] An SiO ₂ film containing Al ₂ O ₃ is formed as a first layer on a surface of a soda lime glass substrate, and a second layer is formed thereon.
Photocatalytic glass in which a film mainly composed of TiO ₂ is formed as a layer. 2. The photocatalytic glass according to claim 1, wherein the content of Al ₂ O ₃ in the first layer is 1 to 80% by weight. 3. The TiO ₂ content in the second layer is 10 to 100.
The photocatalytic glass according to claim 1, which is in a weight percent. 4. Components other than TiO _{2 in} the second layer are SiO ₂ ,
_{Al 2 O 3, P 2 O} 5, B 2 O 3, ZrO 2, SnO 2, Ta 2 at least one of claims 3, wherein the photocatalyst glass is a metal oxide of the O _5. 5. The first and second layers each have a thickness of 50
The photocatalytic glass according to claim 1, having a thickness of from 500 to 500 nm. 6. A first layer on a surface of a soda lime glass substrate.
Containing Al as the _TwoCoated with a coating solution consisting of a solution
Later, TiO_TwoPrecursor and / or TiO_TwoMixed zo containing
The solution for the second layer is applied, dried and fired.
A method for producing a photocatalytic glass. 7. The production of a photocatalytic glass according to claim 6, wherein the coating solution for the first layer comprises a hydrolyzate of an alkoxysilane compound containing a nitrate, an organic acid salt, an acetylacetonate compound and an alkoxide compound of an Al element. Method. 8. When the starting material of TiO _{2 in} the second layer is crystalline fine particles, the content of TiO _{2 in} the second layer is 10 to 90%.
The method for producing a photocatalytic glass according to claim 6, wherein the content is% by weight. 9. When the TiO _{2 in} the second layer is a solution as a starting material, the content of TiO _{2 in} the second layer is 50 to 100% by weight.
The method for producing a photocatalytic glass according to claim 6, wherein