Formation of photocatalyst film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for forming a photocatalytic film having high activity and strong film strength at a low temperature.

【0002】

[Conventional technology]

When the photocatalyst is irradiated with light having an energy equal to or higher than the band gap, electrons are generated in the conduction band and holes are generated in the valence band by photoexcitation. The strong reducing power of electrons and the strong oxidizing power of holes generated by this photoexcitation are being studied for use in decomposition / purification of organic substances, decomposition of water, removal of nitrogen oxides, etc., and are used for antibacterial and purification. Practical use is being promoted in some fields.

【0003】

Photocatalysts have been studied for application as catalysts that can obtain strong decomposition activity, such as antifouling, antibacterial, deodorizing, and purification of harmful gases such as NOx. In addition, studies have been made to apply cleaning with raindrops by utilizing the superhydrophilic effect of the photocatalyst. Already, it has been put to practical use for air purifier filters, antifouling of road lighting and fluorescent lamps, antifogging and water repellency of mirrors and lenses, antifouling of automobile painted surfaces, and antifouling of building materials and tiles. ..

【0004】

As a photocatalyst, for example, titanium oxide having high activity and excellent chemical stability is formed in the form of fine particles or a film. The fine particle photocatalyst is generally formed into a film by adhering to a substrate via an adhesive. As the binder having adhesive performance, a silica-based material or a fluororesin material is used. In the method of fixing the photocatalyst particles with a binder, it is necessary to use a porous material in order to prevent the photocatalyst from being buried in the binder and impairing the catalytic activity. Further, in order to obtain a highly active film, it is necessary to make the binder as porous as possible, which causes a problem that adhesion and film strength are impaired.

【0005】

On the other hand, even in the photocatalyst fixing method using a binder, a film having strong adhesion can be formed by sacrificing the photocatalytic activity. Since superhydrophilicity can be obtained even with relatively weak photocatalytic activity, it is possible to prevent stains with a large cleaning effect by raindrops. This has been put to practical use for antifouling of automobiles. However, in a room where the cleaning effect by raindrops cannot be expected, there is a problem that the antifouling effect can hardly be obtained because the photocatalytic activity is weak, which is not practical. As described above, in the method of fixing the photocatalyst with a binder, it is difficult to achieve both film strength and activity in principle, and no significant improvement can be expected.

【0006】

Therefore, as a general method of directly forming a photocatalyst material into a film without using a binder, there is a method of forming a titanium oxide film by using a sol-gel method, and a raw material solution such as titanium alkoxide or titanium chelate is used as a substrate. After coating and drying, a photocatalyst film is formed by firing at a high temperature of 500 ° C. or higher to form a photocatalyst film.

【0007】

Since the method of directly forming the photocatalyst film by the sol-gel method does not require the use of a binder, there is no problem that the photocatalyst is buried in the binder, and a film having high film strength and high activity can be obtained. Moreover, since a transparent film can be obtained, various colors can be obtained as needed by changing the color of the base, and it can also be used for applications that emphasize interiors.

【0008】

[Problems to be Solved by the Invention]

However, in order to obtain an active photocatalyst film by the sol-gel method, it is necessary to heat it to a temperature at which it crystallizes, and high-temperature firing at 500 ° C. or higher is required. Therefore, it is a technique that can be formed only on a substrate having excellent heat resistance, and there is a problem that the fields in which it can be applied are extremely limited.

【0009】

That is, in the conventional photocatalytic film forming method by the sol-gel method, it is difficult to form a film having high activity and excellent adhesion and transparency at a low temperature, and it adheres firmly to the plastic and is transparent. It is not possible to form an excellent highly active photocatalyst film. Therefore, the fields in which the excellent functions of the photocatalyst can be exhibited are limited.

【0010】

In view of the above, it is an object of the present invention to form a photocatalyst film at a low temperature so that a photocatalyst film having high activity and strong film strength can be provided on a plastic having low heat resistance.

【0011】

[Means for solving problems]

In the problem-solving means according to the present invention, in order to form a strongly highly active photocatalyst film on a substrate having low heat resistance, a thin film deposition method or a sputtering method, which is a general thin film forming method, is adopted and the substrate is heated. By utilizing the energy of electrons, ions, and active particles existing in the space where the metal raw material or metal oxide raw material as a photocatalyst is placed so that the film can be formed without suppressing the temperature rise of the substrate. It forms a photocatalytic film at low temperatures. Active particles are, for example, radicals (free atoms) in plasma, which is a space in which ions and electrons of molecules and atoms exist, excited atoms and molecules, and are chemically extremely active particles. Then, in order to utilize these, the substrate may be irradiated in the form of low-energy excitation lines.

【0012】

That is, the metal raw material or the metal oxide raw material is once decomposed to the molecular level or the atomic level by a vapor deposition method or a sputtering method, and a film is formed on the substrate to form a photocatalyst film. Since the raw material molecule or the raw material atom becomes a high energy state, the crystallization of the formed photocatalyst film can be promoted at a low temperature, the crystallinity of the photocatalyst film is improved, and high activation can be achieved. Further, by irradiating the substrate with excitation rays, the surface of the substrate is cleaned by electrons and ions to be surface-modified, and the film strength is increased.

【0013】

In this way, while irradiating a substrate such as plastic, rubber, or ceramics having low heat resistance with a low-energy excitation ray using only one of ion beam, electron beam, radical beam, and plasma, or a combination of these, while irradiating the substrate. Since a metal raw material or a metal oxide raw material is formed on a substrate by a vapor deposition method or a sputtering method, a photocatalyst film can be directly formed without using a binder, and there is no problem that the photocatalyst is buried in the binder, so that a highly active photocatalyst film can be obtained. It is formed. Further, in the conventional sol-gel method, high temperature heating of about 500 ° C. or higher is required to crystallize the photocatalyst film, but the raw material becomes a high energy state due to the irradiation of excitation rays at the time of film formation, so that the substrate is heated. Is unnecessary, and a well-crystallized film can be formed even at a low temperature. Further, when a titanium oxide photocatalyst film is formed using titanium or titanium oxide as a raw material, a transparent film can be easily obtained.

【0014】

Here, when the kinetic energy of the charged particles in the excitation line is set to 200 eV or less, as a result of the study by the inventors, it has been clarified that a highly active photocatalytic film can be formed at a low temperature. If the kinetic energy exceeds 200 eV, the film formed is sputtered, so that the film forming speed decreases and efficient film formation cannot be performed. Further, high-energy excitation ray irradiation raises the surface temperature of the substrate, which causes a problem that it cannot be applied to a substrate having low heat resistance.

【0015】

When plastic is used as the substrate, it is preferable to form a buffer film that is not subject to photocatalytic action on the plastic substrate. Then, a photocatalyst film is formed on the buffer film. This is because the photocatalytic film has high activity, and when the photocatalytic film is formed directly on the plastic, there is a problem that the plastic is decomposed by the photocatalytic action, and the quality of the plastic is deteriorated or the adhesion is lowered. However, once a buffer film is formed on the plastic by a vapor deposition method or a sputtering method, the buffer film is not decomposed by the photocatalyst even if the photocatalyst film is formed on the buffer film. Can be prevented from being decomposed. As the buffer film, for example, an inorganic material such as silica, alumina, or metal may be used, and the buffer film is formed in the form of a film.

【0016】

Further, instead of the inorganic material, a fluororesin film or a silicone resin film that is not subjected to photocatalytic action may be formed. Since the fluororesin or the silicone resin is not decomposed by the photocatalyst, even if the photocatalyst film is formed on the buffer film, the plastic is protected by the fluororesin or the silicone resin, and the activity of the photocatalyst can prevent the plastic from being decomposed. it can.

【0017】

The plastics used are polyimide resin, polyester resin, hydrocarbon resin, polyether resin, and acrylic resin. The polyester resin contains a polycarbonate resin. Hydrocarbon-based resins include polyethylene resins, polypropylene resins, polystyrene resins, and ABS (acrylonitrile-butadiene-styrene) resins. Examples of the polyether resin include a polyacetal resin and a polyphenylene oxide resin. Acrylic resins include methyl methacrylate resins. Further, the shape is a plate-shaped molded product or a film-shaped product. In particular, since the film form is excellent in flexibility, a photocatalyst sheet having a photocatalyst film formed on the film is fitted on the surface of an industrial product such as an appliance, an apparatus, an electric appliance, or a building material having an arbitrary shape. It can be attached, and antifouling, antibacterial, and purifying functions can be easily added, and the photocatalytic film can be utilized.

【0018】

By the way, in the thin film deposition method and the sputtering method, it is necessary to install the substrate in the vacuum chamber of the thin film forming apparatus at the time of film formation. In particular, when the surface area of the photocatalyst forming surface is large, the substrate may not be accommodated in the vacuum chamber. Further, even if the size can be accommodated in the vacuum chamber, there is a problem that the number of substrates that can be accommodated in the vacuum chamber is limited and the production efficiency is poor. Therefore, by forming a film-like substrate, the film can be wound in a roll shape, so that the wound film can be pulled out and wound in a roll-to-roll manner to continuously form a photocatalyst film. Therefore, the production efficiency can be improved and the production cost can be extremely reduced. Moreover, since the film thus produced can be used as a photocatalyst film simply by forming a sheet having a predetermined shape and attaching it to the surface of an industrial product, the photocatalyst film can be used regardless of the material of the industrial product that requires the function of a photocatalyst. There is an advantage that a film suitable for formation can be freely selected.

【0019】

Further, a fluororesin or a silicone resin may be used as a substrate, and a photocatalyst film can be directly formed on the substrate. Since these resins are relatively excellent in flexibility, by forming them into a film, the production efficiency is improved as described above, and it is not necessary to form a buffer film between the substrate and the photocatalyst film. , The film formation time can be shortened, and the production cost can be significantly reduced.

【0020】

The polyimide resin has a high heat resistance temperature of about 300 ° C, and is suitable for being attached to the surface of equipment such as electric appliances that require heat resistance. Further, when the photocatalyst film is formed on the film, the film can be heated to the heat resistant temperature of the polyimide resin, so that the film strength is high, and the adhesion between the photocatalyst film and the film is particularly excellent and the reliability is high. A photocatalyst sheet can be obtained. Further, when the photocatalyst film is formed, the temperature of the film rises because the excitation line is irradiated, but since the polyimide resin has a high heat resistant temperature, the excitation line can be sufficiently irradiated, and a highly active photocatalyst film can be obtained relatively easily. Be done. Further, even if the temperature of the film rises due to variations in the manufacturing process, problems such as stretching or deterioration of the film due to heat are unlikely to occur, and a high-quality photocatalyst film can be obtained.

【0021】

Further, the polyester resin, the polycarbonate resin, and the polypropylene resin are inexpensive, and at the same time, a film having excellent transparency can be obtained. Therefore, there is an advantage that a transparent photocatalyst sheet can be formed and a photocatalyst film in consideration of interior properties can be easily produced. In addition, polyester resin and polycarbonate resin are inexpensive but have relatively excellent heat resistance, and the film is less likely to be deformed even if the temperature of the film rises due to variations in the manufacturing process, and the film is used in a relatively high temperature environment. It has the feature of withstanding, and a high-quality, versatile photocatalyst sheet can be obtained. Since ABS resin is inexpensive and is used in large quantities for the exterior of household electrical appliances, etc., the ABS resin film on which the photocatalyst film is formed can be easily heat-bonded to various devices using ABS resin. , If you use the same color, it will look better.

【0022】

Since the photocatalyst film of the present invention does not use a binder, a transparent film can be formed, and by forming a transparent film such as silica as a buffer film on plastic, the photocatalyst film becomes a transparent film. Therefore, by changing the color of the base, it is possible to make various colors as needed, which is most suitable for use in an application that emphasizes the interior. In particular, a transparent photocatalyst sheet can be easily produced by using a transparent resin film. Since interior equipment is required for household equipment, it is necessary to use various colors as needed. However, if a transparent photocatalyst sheet is attached, the interior can be considered without damaging the color of various equipment. Wider range of use.

【0023】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a thin film forming apparatus used for forming a photocatalyst film according to an embodiment of the present invention. This device is an electron beam vapor deposition device, 1 is a vacuum chamber, 2 is a vacuum exhaust port, 3 is an electron beam source that generates electron beam 4, 5 is a vapor deposition raw material, 6 is an excitation radiation source, 7 is a substrate holder, 8 Is the substrate, 9 is the evaporation material, and 10 is the bias power supply.

【0024】

Then, the substrate 8 made of plate-shaped or film-shaped plastic, rubber, ceramics, etc. is fixed to the substrate holder 7, the vapor-deposited raw material 5 made of an inorganic material is put in a pot, vacuum exhausted, and oxygen ions are emitted from the excitation radiation source 6. , Oxygen radical, oxygen plasma mixed excitation line is irradiated to the substrate 8. At the same time, the thin-film deposition material 5 is exposed to an electron beam 4 and heated to evaporate the vapor-deposited raw material 5 and adhere to the substrate 8 to form a buffer film 11. Here, the inorganic material is a material that is not subjected to photocatalytic action, and specifically, is silica, alumina, or a metal such as aluminum, silver, copper, or zinc.

【0025】

When a fluororesin or a silicone resin is used instead of the inorganic material, a buffer film 11 made of the fluororesin or the silicone resin is formed. That is, these resins are not photocatalytic and protect the substrate 8 from photocatalytic action.

【0026】

Next, the vapor deposition material 5 made of a metal raw material or a metal oxide raw material is placed in a pot, and the vapor deposition material 5 is evaporated by the electron beam 4 while irradiating the substrate 8 with the same excitation wire as described above to cause molecules or atoms. And adhered on the buffer film 11 to form a photocatalyst made of a metal oxide. As a result, the photocatalyst film 12 as shown in FIG. 2 is formed. At this time, the raw material adhering on the substrate 8 due to the excited rays becomes a high-energy state, and the crystallization of the photocatalyst film 12 formed into a film proceeds without heating the substrate 8. Here, the metal raw material or the metal oxide raw material is titanium oxide, tungsten oxide, vanadium oxide, zirconium oxide, titanium, tungsten or the like.

【0027】

When a fluororesin or silicone resin that is not decomposed by a photocatalyst is used as the substrate 8, a thin-film deposition material 5 made of a metal raw material or a metal oxide raw material is placed in a pot, and mixed excitation of oxygen, ions, oxygen radicals, and oxygen plasma is performed. While irradiating the wire toward the substrate 8, the vapor deposition raw material 5 is evaporated by the electron beam 4 to be decomposed into molecules or atoms, which are directly adhered to the substrate 8 to form a photocatalyst made of a metal oxide. As a result, the photocatalyst film 12 as shown in FIG. 3 is formed.

【0028】

Since the photocatalyst film can be formed at a low temperature by forming a film while irradiating the substrate with excitation rays in this way, the photocatalyst film can be formed on a substrate such as plastic having low heat resistance. Then, the crystallization of the photocatalyst film is promoted, the crystal becomes closer to a single crystal, and defects are reduced. Therefore, a highly crystalline photocatalyst film is obtained, and the activity is increased. In addition, the excitation line cleans the surface of the substrate or the surface of the buffer film formed on the substrate and makes it uneven, so that the photocatalyst film formed on this surface adheres firmly and the film strength is increased. Become stronger. Since no introduction gas is required for vapor deposition, the structure of the forming apparatus can be simplified and the forming time can be shortened.

【0029】

Then, as described above, a photocatalytic film can be formed on a substrate such as plastic, but in order to exert a photocatalytic action in actual use, it must be formed on the surface of an industrial product such as an electric appliance. If it is a small product that can be accommodated in the vacuum chamber of the vapor deposition apparatus, the photocatalyst film may be formed directly on the surface of the product by the above-mentioned forming method. When the product cannot be housed in a vacuum chamber, the substrate can be formed into a film, and a photocatalyst film is formed on the substrate to form a photocatalyst sheet according to the shape of the product, so that the product can be attached to the surface of the product.

【0030】

It should be noted that the present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention. That is, even if a sputtering method is used instead of the vapor deposition method, it is possible to form a photocatalyst film by performing sputtering while irradiating the excitation rays in the same manner.

【0031】

[Example]

(Example 1) Silicon oxide (silica) by EB (electron beam) vapor deposition method while irradiating a 6 cm × 3 cm polyester resin substrate with mixed excitation lines of oxygen ions, oxygen radicals, and oxygen plasma using SiO as a vapor deposition material. ) Was formed. Next, using TiO as a vapor deposition material, a titanium oxide photocatalyst was formed by the EB vapor deposition method while irradiating the substrate with mixed excitation lines of oxygen ions, oxygen radicals, and oxygen plasma. At this time, a DC voltage was applied to the substrate holder holding the substrate, and the voltage was adjusted so that the kinetic energy of the charged particles in the excitation line became 80 eV. For the excitation ray irradiation, an excitation radiation source EBS-23 manufactured by Cryovac was used. The film thickness was adjusted so that the film thickness was 3000 Å.

【0032】

(Example 2) Using TiO as a vapor deposition material, a titanium oxide photocatalyst was formed by the EB vapor deposition method while irradiating the substrate with a mixed excitation line of oxygen ions, oxygen radicals, and oxygen plasma. A 6 cm × 3 cm silicone resin substrate was used as the substrate, and an excitation radiation source EBS-23 manufactured by Cryovac was used for the excitation ray irradiation. A DC voltage was applied to the substrate holder during film formation, and the kinetic energy of the charged particles in the excitation line was adjusted to 80 eV. The film thickness was adjusted so that the film thickness was 3000 Å.

【0033】

(Example 3) Using TiO as a vapor deposition material, a titanium oxide photocatalyst was formed by the EB vapor deposition method while irradiating the substrate with a mixed excitation line of oxygen ions, oxygen radicals, and oxygen plasma. A 6 cm × 3 cm fluororesin substrate was used as the substrate, and an excitation radiation source EBS-23 manufactured by Cryovac was used for the excitation ray irradiation. A DC voltage was applied to the substrate holder during film formation, and the kinetic energy of the charged particles in the excitation line was adjusted to 80 eV. The film thickness was adjusted so that the film thickness was 3000 Å.

【0034】

(Comparative Example 1) Using TiO as a vapor deposition material, a titanium oxide photocatalyst was formed by the EB vapor deposition method. At this time, the oxygen gas pressure is 5 × 10.^-5Oxygen gas was introduced to become Torr. The substrate used was a 6 cm × 3 cm silicone resin substrate. The film thickness was adjusted so that the film thickness was 3000 Å.

【0035】

(Comparative Example 2) Using TiO as a vapor deposition material, a titanium oxide photocatalyst is formed by the EB vapor deposition method while irradiating a 6 cm × 3 cm polyester resin substrate with a mixed excitation line of oxygen ions, acid cord radicals, and oxygen plasma. went. At this time, a DC voltage was applied to the substrate holder, and the voltage was adjusted so that the kinetic energy of the charged particles in the excitation line became 80 eV. For the excitation ray irradiation, an excitation radiation source EBS-23 manufactured by Cryovac was used. The film thickness was adjusted so that the film thickness was 3000 Å.

【0036】

(Comparative Example 3) Using TiO as a vapor deposition material, a titanium oxide photocatalyst was formed by the EB vapor deposition method while irradiating the substrate with mixed excitation lines of oxygen ions, oxygen radicals, and acid cord plasma. A 6 cm × 3 cm silicone resin substrate was used as the substrate, and an excitation radiation source EBS-23 manufactured by Cryovac was used for the excitation ray irradiation. A DC voltage was applied to the substrate holder during film formation, and the kinetic energy of the charged particles in the excitation line was adjusted to 220 eV. The film thickness was adjusted so that the film thickness was 3000 Å.

【0037】

The samples obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were separately placed in a 5 liter container, and acetaldehyde, which is one of the malodorous substances, was injected to a concentration of 100 ppm. Next, using a 6 W black light, the photocatalyst film on the sample surface was irradiated with ultraviolet rays, and the time for the acetaldehyde concentration to decrease to 1 ppm was measured.

【0038】

After measuring the acetaldehyde decomposition rate, the sample was irradiated with black light, and irradiation was continued until the total irradiation time reached 240 hours. After that, it was examined whether or not the sample was discolored and whether or not the photocatalyst film was peeled off by rubbing with a finger. The results are shown in Table 1. Table 1 also shows the presence or absence of substrate deformation and the film formation rate after sample preparation in each Example and Comparative Example.

【0039】

[table 1]

<img file="JP2000296332A_D0001.tif" />In the sample of Example 1 in which the titanium oxide photocatalyst was formed by EB deposition while irradiating an excitation line in which the kinetic energy of the charged particles was set to 80 eV after forming a silica buffer film on the polyester film, acetaldehyde was used in 2.3 hours. Disassembled. The same level of acetaldehyde decomposition rate was also obtained in the samples of Examples 2 and 3 using silicone resin and fluororesin as the substrate. On the other hand, in the sample of Comparative Example 1 in which the excitation rays were not irradiated during the formation of titanium oxide, the acetaldehyde decomposition rate was extremely slow, 1/10 or less. Further, in the sample of Comparative Example 2 in which the titanium oxide photocatalyst film was directly formed without providing the buffer film on the polyester film, the acetaldehyde decomposition rate was the same level as that of the samples of Examples 1 to 3, but was black for 240 hours. Discoloration of the substrate was observed after the light irradiation. In addition, the adhesion strength decreased, and peeling of the film was observed. It is considered that the silicone resin, the fluororesin, and the silica are hardly decomposed by the photocatalyst, but the polyester is decomposed by the photocatalyst, so that the substrate is discolored and the adhesion strength is lowered.

【0040】

In the sample of Comparative Example 3 in which the excitation line intensity at the time of forming the titanium oxide photocatalyst film was increased to 200 eV or more, the acetaldehyde decomposition rate was at the same level as that of the samples of Examples 1 to 3, but the film formation rate was the same as that of Examples 1 to 3. It was less than half of the sample of 3. In addition, the substrate was deformed after the film formation. That is, it is considered that the excitation line intensity is too strong, so that the film formed on the substrate is sputtered by the excitation line, and the film formation rate is reduced. Further, it is considered that the temperature of the substrate became high due to the strong irradiation intensity of the excitation line, and the substrate was thermally deformed.

【0041】

(Example 4) A sample of the photocatalyst film prepared in Example 1 was adhered to the surface of a 6 cm × 3 cm white ABS resin substrate with an epoxy resin.

【0042】

(Comparative Example 4) A 6 cm × 3 cm white ABS resin substrate was used as Comparative Example 4.

【0043】

1 m sample of Example 4 and Comparative Example 4³I put it in an acrylic box and burned 10 cigarettes. After taking each sample out of the box, the color of the sample was confirmed. Next, a 6 W white fluorescent lamp was irradiated for 240 hours at a distance of 10 cm from the sample. After that, the color of each sample was examined. The results are shown in Table 2.

【0044】

[Table 2]

<img file="JP2000296332A_D0002.tif" />Both the samples of Example 4 and Comparative Example 4 were stained with cigarette smoke and colored yellow before irradiation with the fluorescent lamp. However, in the sample of Example 4, the yellow coloring caused by the cigarette disappeared after the irradiation with the fluorescent lamp and the sample became white, and the purifying effect due to the action of the photocatalyst was observed. On the other hand, in the sample of Comparative Example 4 in which the photocatalyst film was not formed, tobacco stains remained even after irradiation with the fluorescent lamp, and coloring was observed.

【0045】

[Effect of the invention]

As is clear from the above description, in the photocatalyst film forming method according to the present invention, a highly active photocatalyst film having high film strength can be formed at a low temperature by forming a film while irradiating with excitation rays. Therefore, a highly active photocatalyst film can be formed on plastics such as ABS resin having a low heat resistant temperature.

【0046】

Here, if a film-like substrate in which a buffer film is formed of an inorganic material, a fluororesin, or a silicone resin, or a film of a fluororesin or a silicone resin is used as the substrate, the film strength does not deteriorate and the film is highly reliable. A photocatalyst sheet is obtained. Since such a photocatalyst sheet is flexible, it can be easily attached to the surface of various industrial products, and the functions of the photocatalyst such as antifouling and deodorization can be exhibited everywhere.

【0047】

Further, since a photocatalyst film having high activity and excellent transparency can be obtained, a transparent photocatalyst sheet is produced by forming a photocatalyst film on a transparent film such as polyester resin, polycarbonate resin, or polypropylene resin. be able to. Therefore, the photocatalyst sheet can be made into various colors as needed by changing the color tone of the base, so that the function of the photocatalyst can be added to industrial products considering interior characteristics, especially household appliances such as electric appliances. Suitable for cases.

[Simple explanation of drawings]

[Figure 1]

Schematic configuration diagram of the film forming apparatus for forming the photocatalyst film of the present invention [Figure 2]

Cross-sectional view of the photocatalyst sheet with the buffer film formed [Fig. 3]

Sectional view of photocatalyst sheet [Explanation of symbols]

1 Vacuum chamber 2 Vacuum exhaust port 3 electron source 4 electron beam 5 Thin film deposition material 6 Excitation source 7 Board holder 8 board 9 Evaporative raw material 10 Bias power supply 11 Buffer membrane 12 Photocatalytic membrane