Photocatalytic sheet, photocatalytic sheet laminate, and deodorizing unit

Abstract

The present invention provides a photocatalytic sheet comprising a photocatalytic layer having excellent homogeneity and a plastic sheet having excellent light transmittance. [Solution] The photocatalytic sheet of the present invention comprises a translucent plastic sheet having first and second main surfaces, a first photocatalytic layer provided on the first main surface, and a first metal oxide layer provided between the first main surface and the first photocatalytic layer, wherein the first photocatalytic layer is in contact with the first metal oxide layer, and the first metal oxide layer is an aluminum oxide vapor-deposited film or a silicon oxide-aluminum oxide vapor-deposited film, and when the first metal oxide layer is a silicon oxide-aluminum oxide vapor-deposited film, the ratio of the mass b of silicon oxide to the mass a of aluminum oxide in the first metal oxide layer (b / a) is (0.001 / 100) or more and (80 / 20) or less.

Description

Technical Field

[0001] The present invention relates to a photocatalyst sheet, a photocatalyst sheet laminate, and a deodorizing unit.

Background Art

[0002] Photocatalyst particles are particles having photocatalytic activity generated by receiving light. By utilizing the photocatalytic activity, for example, it becomes possible to decompose harmful substances in the air. In order to utilize the photocatalytic activity, it is necessary to fix the photocatalyst particles to a substrate. Conventionally, an opaque photocatalyst carrier in which a photocatalyst is supported on an opaque substrate is common. However, when light is irradiated from one side, the light-irradiated surface can activate the photocatalyst, but the back surface is not irradiated with light or does not receive sufficient light to activate the photocatalyst, and the substrate surface cannot be effectively utilized. Further, Patent Document 1 discloses a laminated film including a polyester substrate, an alumina vapor deposition layer on the surface thereof, a mixed layer of tetraethoxysilane and polyvinyl alcohol further thereon, a photocatalyst layer composed of a titanium dioxide inclusion adhesive layer further thereon, and a polyethylene sealant layer further thereon.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the photocatalyst-functional film disclosed in Patent Document 1 is a laminated film composed of multiple layers, so it has low transparency and poor light transmittance of the irradiated light. Further, since the photocatalyst layer is encapsulated in the laminated film and cannot contact the malodorous components in the surrounding environment, it is insufficient in terms of exhibiting deodorizing properties. Conventionally, wet coating and dry coating methods have been considered for forming a photocatalytic layer on the surface of a substrate. However, these methods have the drawback of losing the transparency of the substrate supporting the photocatalyst, making it difficult to effectively utilize the irradiated light. For example, if a plastic substrate with a water-repellent surface is treated to become hydrophilic by UV irradiation or by applying a primer material before wet coating, the plastic substrate itself often oxidizes and yellows, or the transparency of the substrate is lost due to the influence of the primer material. Furthermore, in the dry coating process, the photocatalytic layer is formed by vapor deposition, which can make it difficult for the photocatalytic material to exhibit its original photocatalytic deodorizing performance due to thermal degradation or changes in its crystal structure. The present invention has been made in view of these circumstances, and provides a photocatalytic sheet comprising a photocatalytic layer having excellent homogeneity and a plastic sheet having excellent light transmittance. [Means for solving the problem]

[0005] The present invention provides a photocatalytic sheet comprising a translucent plastic sheet having first and second main surfaces, a first photocatalytic layer provided on the first main surface, and a first metal oxide layer provided between the first main surface and the first photocatalytic layer, wherein the first photocatalytic layer is in contact with the first metal oxide layer, and the first metal oxide layer is an aluminum oxide vapor-deposited film or a silicon oxide-aluminum oxide vapor-deposited film, and when the first metal oxide layer is a silicon oxide-aluminum oxide vapor-deposited film, the ratio of the mass b of silicon oxide to the mass a of aluminum oxide in the first metal oxide layer (b / a) is (0.001 / 100) or more and (80 / 20) or less. [Effects of the Invention]

[0006] The photocatalytic sheet of the present invention has a structure in which a first metal oxide layer and a first photocatalytic layer are laminated on a first main surface of a translucent plastic sheet. Therefore, deterioration of the translucent plastic during the manufacturing process can be suppressed, and the translucent plastic can have excellent light transmission. As a result, light transmitted through the first photocatalytic layer can efficiently reach the back surface of the photocatalytic sheet. Furthermore, it becomes possible to irradiate the first photocatalytic layer with light transmitted through the translucent plastic sheet. In addition, since the first metal oxide layer is an aluminum oxide vapor-deposited film or the silicon oxide-aluminum oxide vapor-deposited film described above, the photocatalytic layer can have excellent homogeneity. This has been revealed by experiments conducted by the inventors. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of a photocatalytic sheet according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of a photocatalytic sheet according to one embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view of a photocatalytic sheet laminate according to one embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view of a photocatalytic sheet laminate according to one embodiment of the present invention. [Figure 5] This is a schematic cross-sectional view of an odor-eliminating unit according to one embodiment of the present invention. [Figure 6] This is a schematic cross-sectional view of an odor-eliminating unit according to one embodiment of the present invention. [Figure 7] This table shows the composition of the coating solution used to form the photocatalytic layer. [Figure 8] This table shows the composition and evaluation results of the metal oxide layers included in Examples 1-13 and Comparative Examples 1-5. [Modes for carrying out the invention]

[0008] The photocatalytic sheet of the present invention comprises a translucent plastic sheet having first and second main surfaces, a first photocatalytic layer provided on the first main surface, and a first metal oxide layer provided between the first main surface and the first photocatalytic layer, wherein the first photocatalytic layer is in contact with the first metal oxide layer, and the first metal oxide layer is an aluminum oxide vapor-deposited film or a silicon oxide-aluminum oxide vapor-deposited film, and when the first metal oxide layer is a silicon oxide-aluminum oxide vapor-deposited film, the ratio of the mass b of silicon oxide to the mass a of aluminum oxide in the first metal oxide layer (b / a) is (0.001 / 100) or more and (80 / 20) or less.

[0009] The thickness of the first metal oxide layer is preferably 0.1 μm or more and 0.5 μm or less. The thickness of the translucent plastic sheet is preferably 7 μm or more and 500 μm or less. Preferably, the photocatalytic sheet of the present invention further comprises a second photocatalytic layer provided on a second main surface and a second metal oxide layer provided between the second main surface and the second photocatalytic layer, wherein the second photocatalytic layer is in contact with the second metal oxide layer, and the second metal oxide layer is an aluminum oxide vapor-deposited film or a silicon oxide-aluminum oxide vapor-deposited film, and when the second metal oxide layer is a silicon oxide-aluminum oxide vapor-deposited film, the ratio (b / a) of the mass b of silicon oxide to the mass a of aluminum oxide in the second metal oxide layer is (0.001 / 100) or more and (80 / 20) or less. The thickness of the second metal oxide layer is preferably 0.1 μm or more and 0.5 μm or less.

[0010] Preferably, the first photocatalytic layer comprises photocatalytic particles and a siloxane compound, and the proportion of the siloxane compound in the first photocatalytic layer is 0.5 wt% or more and 30 wt% or less. Preferably, the siloxane compound is bonded to both the first metal oxide layer and the photocatalytic particles. The siloxane compound preferably contains a silicon atom bonded to three oxygen atoms.

[0011] The present invention also provides a photocatalyst sheet laminate having a laminated structure or a wound structure in which the photocatalyst sheets of the present invention are laminated, the laminated structure or the wound structure having an air flow path between the photocatalyst sheets. The present invention also provides a deodorizing unit having the photocatalyst sheet of the present invention and a light source unit provided to irradiate the photocatalyst sheet with light. Preferably, the deodorizing unit of the present invention further has a fan provided so that air flows parallel to the photocatalyst sheet.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

[0013] Photocatalytic sheet Each of FIGS. 1 and 2 is a schematic cross-sectional view of the photocatalyst sheet of the present embodiment. The photocatalyst sheet 20 of the present embodiment includes a translucent plastic sheet 2 having a first major surface 6 and a second major surface 7, a photocatalyst layer 3a provided on the first major surface 6, and a metal oxide layer 4a provided between the first major surface 6 and the photocatalyst layer 3a. The photocatalyst layer 3a is in contact with the metal oxide layer 4a. The metal oxide layer 4a is an aluminum oxide vapor deposition film or a silicon oxide-aluminum oxide vapor deposition film. When the metal oxide layer 4a is a silicon oxide-aluminum oxide vapor deposition film, the ratio (b / a) of the mass b of silicon oxide to the mass a of aluminum oxide in the metal oxide layer 4a is not less than (0.001 / 100) and not more than (80 / 20).

[0014] In addition, the photocatalyst sheet 20 may further include a photocatalyst layer 3b provided on the second major surface 7 and a metal oxide layer 4b provided between the second major surface 7 and the photocatalyst layer 3b. The photocatalyst layer 3b is in contact with the metal oxide layer 4b. The metal oxide layer 4b is an aluminum oxide vapor deposition film or a silicon oxide-aluminum oxide vapor deposition film. When the metal oxide layer 4b is a silicon oxide-aluminum oxide vapor deposition film, the ratio (b / a) of the mass b of silicon oxide to the mass a of aluminum oxide in the metal oxide layer 4b is not less than (0.001 / 100) and not more than (80 / 20).

[0015] The translucent plastic sheet 2 is, for example, a polyester film such as a polyethylene terephthalate film or a polyethylene naphthalate film, a polyolefin film such as a polyethylene film or a polypropylene film, a polyamide film such as a nylon film, or a polycarbonate film. Particularly preferred are a nylon film (polyamide film) and a polyester film having high heat resistance. The film thickness of the translucent plastic sheet is preferably not less than 7 μm and not more than 100 μm, and more preferably not less than 10 μm and not more than 100 μm. If the film thickness is too thin, it is likely to be deformed during the formation of the photocatalyst layers 3a and 3b, making it difficult to form homogeneous photocatalyst layers 3a and 3b. If the film thickness is too thick, transparency cannot be maintained, and problems occur in the photocatalytic activity due to poor light transmission. The translucent plastic sheet 2 has a first major surface 6 and a second major surface 7. The first major surface 6 is one of the front and back surfaces of the translucent plastic sheet 2, and the second major surface 7 is the other of the front and back surfaces of the translucent plastic sheet 2. The translucent plastic sheet 2 may be a flat sheet as shown in FIG. 1, or may be a pleated sheet as shown in FIG. 2.

[0016] The metal oxide layers 4a and 4b are aluminum oxide vapor-deposited films or silicon oxide-aluminum oxide vapor-deposited films. The metal oxide layer 4a is provided between the first main surface 6 of the translucent plastic sheet 2 and the photocatalyst layer 3a. The metal oxide layer 4a can come into contact with the first main surface 6. The metal oxide layer 4a also comes into contact with the photocatalyst layer 3a. The metal oxide layer 4b is provided between the second main surface 7 of the translucent plastic sheet 2 and the photocatalytic layer 3b. The metal oxide layer 4b can come into contact with the second main surface 7. The metal oxide layer 4b also comes into contact with the photocatalytic layer 3b.

[0017] When the metal oxide layer 4a or 4b is a silicon oxide-aluminum oxide vapor-deposited film, the ratio of the mass b of silicon oxide to the mass a of aluminum oxide in the metal oxide layer 4a or 4b (b / a) is (0.001 / 100) or more and (80 / 20) or less. Alternatively, the metal oxide layer 4a or 4b is an aluminum oxide vapor-deposited film. This makes it possible to set the surface wetting tension of the surface of the metal oxide layer 4a or 4b to 60 mN / m (dyne / cm) or more, resulting in good wetting spread of the hydrophilic photocatalytic coating solution for forming the photocatalytic layer 3a or 3b, and enabling the formation of a homogeneous photocatalytic layer 3a or 3b. Furthermore, it is possible to suppress the decrease in light transmittance of the translucent plastic sheet 2, allowing light to be efficiently irradiated to both the photocatalytic layer 3a and the photocatalytic layer 3b, and enabling both sides of the photocatalytic sheet 20 to have photocatalytic activity. The thickness of the metal oxide layer 4a or 4b is, for example, 0.1 μm or more and 0.5 μm or less. This allows the photocatalytic layer 3a or 3b to have high durability. If the film thickness is too thin, defects may occur in the metal oxide layer 4a or 4b, and it may not be possible to form a homogeneous metal oxide layer 4a or 4b. If the film thickness is too thick, cracks may occur in the metal oxide layer 4a or 4b, and problems may arise with the transparency and homogeneity of the metal oxide layer 4a or 4b.

[0018] The metal oxide layer 4a or 4b can be formed by a deposition method such as a physical deposition method including vacuum deposition, sputtering, or ion plating, or a chemical deposition method including plasma chemical vapor deposition. When forming the metal oxide layer 4a or 4b, the deposition may be performed in a single step while adjusting the film thickness with a film thickness gauge, or it may be performed in multiple steps. Specific deposition sources that can be used include aluminum oxide powder and aluminum oxide powder.

[0019] The photocatalytic layer 3a or 3b is a layer that contains a photocatalyst and exhibits photocatalytic activity upon exposure to light. Examples of photocatalysts (photocatalytic particles) include tungsten oxide and titanium oxide. Commercially available photocatalysts containing tungsten oxide or titanium dioxide can be used to form the photocatalytic layer 3a or 3b. Furthermore, a metal or metal compound may be immobilized on the surface of the photocatalytic particles as a co-catalyst to reduce the energy gap of the various photocatalysts and improve their responsiveness in the visible light region. In this case, it is preferable to add a transition metal as the metal in the metal compound. Platinum group metals such as platinum, palladium, rhodium, iridium, ruthenium, and osmium are preferred. The 50% volume cumulative diameter of the photocatalytic particles contained in the photocatalytic layer 3a or 3b is preferably between 5 nm and 200 nm. A diameter of 5 nm or more results in less aggregation in the coating solution and easier redispersion. A diameter of 200 nm or less allows for easy uniform mixing with other components during the processing step and reduces detachment from the photocatalytic sheet 20, which is desirable. Particle size can be measured using laser diffraction particle size analyzers, dynamic light scattering particle size analyzers, and the like.

[0020] The proportion of photocatalyst in the photocatalytic layer 3a or 3b is, for example, 70 wt% to 98 wt%. The photocatalytic layer 3a is provided on the metal oxide layer 4a and is in contact with the metal oxide layer 4a. The photocatalytic layer 3b is provided on the metal oxide layer 4b and is in contact with the metal oxide layer 4b. Furthermore, the photocatalytic layer 3a or 3b can be provided adjacent to the air channel. This allows for the efficient decomposition of organic compounds in the air flowing through the air channel by the photocatalytic activity of the photocatalytic layer 3a or 3b. When both photocatalytic layers 3a and 3b are provided, the translucent plastic sheet, which is the base material, has excellent light transmission properties, making it possible to irradiate either the photocatalytic layer 3a or 3b with light that has passed through the translucent plastic sheet, thereby generating photocatalytic activity in both the photocatalytic layers 3a and 3b on both sides.

[0021] The photocatalyst contained in photocatalyst layer 3a and the photocatalyst contained in photocatalyst layer 3b may be the same or different. For example, the photocatalyst contained in photocatalyst layer 3a may be tungsten oxide, and the photocatalyst contained in photocatalyst layer 3b may be titanium dioxide. This allows photocatalytic activity to be generated by using light of different wavelengths in photocatalyst layer 3a and photocatalyst layer 3b, enabling efficient decomposition of organic compounds in the air. Furthermore, the photocatalyst contained in photocatalyst layer 3a and the photocatalyst contained in photocatalyst layer 3b may both be tungsten oxide or titanium dioxide.

[0022] The photocatalytic layer 3a or 3b may contain photocatalytic particles and a siloxane compound as a binder. The siloxane compound is a compound having siloxane units and may be a dehydrated condensate of a silane coupling agent obtained by hydrolysis. The siloxane compound may also contain a silicon atom bonded to three oxygen atoms. The siloxane compound may also be a dehydrated condensate of trisilanol. The proportion of the siloxane compound in the photocatalytic layer 3a or 3b may be 0.5 wt% to 30 wt%. This allows the photocatalytic layer 3a or 3b to have high durability. Furthermore, it is possible to suppress the impairment of the photocatalytic activity of the photocatalytic layer 3a or 3b by the siloxane compound, and to suppress the embedding of photocatalytic particles in the siloxane compound binder.

[0023] The photocatalytic layer 3a or 3b can be formed, for example, by wet coating a coating solution containing photocatalytic particles having at least tungsten oxide and / or titanium oxide and a component having siloxane units onto the metal oxide layer 4a or 4b and then drying it. The siloxane unit component included in the coating solution can be any commercially available hydroxysilane, alkoxysilane, or organopolysiloxane. Hydroxysilanes and alkoxysilanes are compounds in which 1 to 3 of the four bonds of a silicon atom are bonded to a hydroxyl group or an alkoxy group, and the remaining bond is bonded to an organic substituent. Organopolysiloxanes are compounds with a linear, branched, or cyclic structure in which the main chain consists of diorganosiloxane units and both ends of the molecular chain have triorganosiloxy groups. Among these, the following hydroxysilane components are particularly preferred. ·R-Si(OH)3 Examples of vinyl-based trihydroxysilanes include vinyltrihydroxysilane, 3-aminopropyltrihydroxysilane, 3-glycidoxypropyltrihydroxysilane, 3-methacryloxypropyltrihydroxysilane, and 3-mercaptopropyltrihydroxysilane, but 3-glycidoxypropyltrihydroxysilane is particularly preferred. (HO)3Si-(CH2) n -Si(OH)3 Examples of alkane skeleton structures for 1,2-bis(trihydroxysilyl)alkanes include ethylene groups (-(CH2)2-), hexamethylene groups (-(CH2)6-), and octamethylene groups (-(CH2)8-), but 1,2-bis(trihydroxysilyl)ethane with an ethylene group (-(CH2)2-) is particularly preferred.

[0024] Furthermore, the siloxane compound contained in the photocatalytic layer 3a or 3b may be bonded to both the metal oxide layer 4a or 4b and the photocatalytic particles. The component containing siloxane units contained in the coating solution undergoes dehydration condensation with the photocatalytic particles and also undergoes dehydration condensation with the silicon oxide-aluminum oxide (mass ratio 80:20~0:100) metal oxide layer 4a or 4b formed on the surface of the translucent plastic sheet, resulting in strong covalent bonding.

[0025] The photocatalytic layer 3a or 3b may further contain antibacterial components and adsorbent components in addition to photocatalytic particles and a siloxane compound binder. The antibacterial component may be copper ions, silver ions, or zinc ions. Water-soluble copper, silver, and zinc compounds may be used as raw materials. The adsorbent component is a component with gas adsorption properties, and examples of such components include zeolite, silicon dioxide, silicates, activated carbon, titania, calcium phosphate, alumina, aluminum hydroxide, magnesium hydroxide, and citric acid.

[0026] The coating solution (wet coating solution) used to form the photocatalytic layer 3a or 3b can be prepared by mixing a component having siloxane units as a binder, photocatalytic particles containing tungsten oxide or photocatalytic particles containing titanium oxide, and water. To improve dispersibility, the photocatalytic particles may be mixed in a photocatalytic solution in which they are dispersed in a dispersion medium. The component R-Si(OH)3, (HO)3Si-(CH2) has a siloxane unit as a binder. n -Si(OH)3 is R-Si(OR')3 and (R'O)3Si-(CH2), respectively. nTrialkoxysilane represented by -Si(OR')3 may be obtained by hydrolyzing the alkoxy group by mixing a binder solution, in which trialkoxysilane is dissolved in water, with an acidic aqueous solution. Examples of dispersion media included in the dispersion of photocatalytic particles include polar solvents, more specifically, water and ethanol. Examples of solvents and dispersion media included in the binder solution include polar solvents, more specifically, water, methanol, ethanol, and propanol.

[0027] The method of applying the coating solution for the photocatalytic layer onto the metal oxide layer 4a or 4b on the translucent plastic sheet (wet coating method) is not particularly limited. Examples include spin coating, dip coating, spray coating, roll coating, gravure coating, wire bar coating, air knife coating, and inkjet coating. The coating solution for the photocatalytic layer only needs to be applied to at least a portion of the translucent plastic sheet. The thickness of the formed photocatalytic layer 3a or 3b is not particularly limited. Regardless of the thickness of the photocatalytic layer 3a or 3b obtained by any coating method, the effects of the photocatalytic sheet of this embodiment can be obtained. The method for drying the applied photocatalytic coating layer is not particularly limited. Examples include room temperature drying, aeration drying, and forced drying using a dryer. The drying temperature is preferably between 20°C and 150°C.

[0028] Photocatalytic sheet laminate Figures 3 and 4 are schematic cross-sectional views of the photocatalytic sheet laminate 30 of this embodiment. The photocatalytic sheet laminate 30 of this embodiment has a laminated structure or a wound structure in which photocatalytic sheets 20 are stacked, and the laminated structure or the wound structure has air channels 5 between the photocatalytic sheets 20. The photocatalytic sheet laminate 30 may consist of one sheet or multiple sheets. The photocatalytic layer 3a or 3b of the photocatalytic sheet 20 included in the photocatalytic sheet laminate 30 is provided adjacent to the air channels 5. As a result, organic compounds flowing through the air channels 5 can be decomposed by the photocatalytic activity of the photocatalytic layer 3a or 3b. The photocatalytic sheet 20 included in the photocatalytic sheet laminate 30 may be a flat sheet type, as shown in the photocatalytic sheet laminate 30 in Figure 3, or a pleated sheet type, as shown in the photocatalytic sheet laminate 30 in Figure 4. Furthermore, the photocatalytic sheet 20 included in the photocatalytic sheet laminate 30 may be processed into a corrugated honeycomb shape.

[0029] Deodorizing unit Figures 5 and 6 are schematic cross-sectional views of the deodorizing unit 40 of this embodiment. The deodorizing unit 40 of this embodiment includes a photocatalytic sheet 20 and a light source unit 8 provided to irradiate the photocatalytic sheet 20 with light. The deodorizing unit 40 may also have a housing 10 that houses the photocatalytic sheet 20. The housing 10 may also house the light source unit 8. The deodorizing unit 40 may also have a fan 9 provided so that air flows parallel to the photocatalytic sheet 20. The photocatalytic sheet 20 included in the deodorizing unit 40 does not necessarily have to form a photocatalytic sheet laminate 30 as shown in Figure 5, but it may also be formed as a photocatalytic sheet laminate 30 as shown in Figure 6. Furthermore, although Figures 5 and 6 show a flat-sheet type photocatalytic sheet 20, the deodorizing unit 40 may also have a pleated-sheet type photocatalytic sheet 20. In addition, the photocatalytic sheet 20 included in the deodorizing unit 40 may be processed into a corrugated honeycomb shape.

[0030] The housing 10 may have an air intake port 11 and an exhaust port 12, and the fan 9 may be configured to draw air into the housing 10 from the air intake port 11 and exhaust the air from inside the housing 10 from the exhaust port 12. The photocatalytic sheet 20 or photocatalytic sheet laminate 30 may be housed in the housing 10 such that the airflow inside the housing 10 is parallel to the photocatalytic sheet 20. The housing 10 may be light-transmitting. In this case, the light source unit 8 can be placed outside the housing 10. Alternatively, sunlight or light from a lighting fixture can be used to irradiate the photocatalytic layer 3a or 3b instead of the light source unit 8. The light source unit 8 is provided to irradiate the photocatalytic layer 3a or 3b with light, and is, for example, an LED light source, a fluorescent lamp, or an incandescent light bulb. The light source unit 8 may be provided to irradiate the photocatalytic layer 3a or 3b with light from a direction perpendicular to the upper surface of the photocatalytic layer 3a or 3b, as shown in Figure 5, or it may be provided to irradiate light in a direction parallel to the photocatalytic sheet 20, as shown in Figure 6. Furthermore, the deodorizing unit 40 may have a controller provided to control the light source unit 8 or the fan 9.

[0031] Photocatalytic slurry (0.05 wt % Pt-WO 3 Preparation of dispersion 200 g of tungsten oxide (manufactured by Kishida Chemical Co., Ltd.) and 1000 mL of pure water were mixed, and tungsten oxide particles were dispersed in this mixture while irradiating it with ultrasound to obtain dispersion A of tungsten oxide particles. Hexachloroplatinum(VI) hexahydrate (manufactured by Kishida Chemical Co., Ltd., purity 98.5%) was dissolved in dispersion A to obtain dispersion B of tungsten oxide particles. The amount of hexachloroplatinum(VI) hexahydrate added was such that the ratio of the weight of elemental platinum to the weight of tungsten oxide particles was 0.05% by weight. Dispersion B was heated at 100°C to evaporate the water and calcined to obtain platinum-supported tungsten oxide particles. These platinum-supported tungsten oxide particles were crushed with pure water in a bead mill to prepare a 20% by weight aqueous dispersion of platinum-supported tungsten oxide (photocatalytic slurry).

[0032] Photocatalytic slurry (TiO 2 Preparation of dispersion Titanium dioxide (TKP-101 manufactured by Teika Co., Ltd.) and pure water were mixed, and titanium dioxide particles were dispersed in this mixture while irradiating it with ultrasound to prepare a 20% by weight TiO2 aqueous dispersion (photocatalytic slurry).

[0033] Preparation of photocatalytic coating solution 1 A coating solution 1 having the composition shown in the table in Figure 7 was prepared. Specifically, photocatalytic coating solution 1 (total solids concentration: 5.6% by weight) was prepared by mixing and stirring 3-glycidoxypropyltriethoxysilane, which is the raw material for the first binder (3-glycidoxypropyltrihydroxysilane), 1,2-bis(triethoxysilyl)ethane, which is the raw material for the second binder (1,2-bis(trihydroxysilyl)ethane), 25 g of photocatalytic slurry (0.05 wt% Pt-WO3 dispersion), and 74.4 g of pure water. 3-glycidoxypropyltriethoxysilane hydrolyzes in the mixture to change into the first binder (3-glycidoxypropyltrihydroxysilane). Also, 1,2-bis(triethoxysilyl)ethane hydrolyzes in the mixture to change into the second binder (1,2-bis(trihydroxysilyl)ethane).

[0034] Preparation of photocatalytic coating solution 2 A coating solution 2 having the composition shown in the table in Figure 7 was prepared. Specifically, photocatalytic coating solution 2 (total solids concentration: 5.6% by weight) was prepared by mixing and stirring 3-glycidoxypropyltriethoxysilane, which is the raw material for the first binder (3-glycidoxypropyltrihydroxysilane), 1,2-bis(triethoxysilyl)ethane, which is the raw material for the second binder (1,2-bis(trihydroxysilyl)ethane), 25 g of photocatalytic slurry (TiO2 dispersion), and 74.4 g of pure water.

[0035] Manufacturing of photocatalytic sheets Photocatalytic sheets of Examples 1-13 and Comparative Examples 1-5, having the metal oxide layer compositions shown in the table in Figure 8, were manufactured. A translucent plastic sheet (substrate) made of A4-sized polyester film (manufactured by Toyobo Co., Ltd.) was used. The thickness of the translucent plastic sheet is shown in the table in Figure 8.

[0036] In Examples 1-6, 13, and Comparative Examples 1-5, a metal oxide layer was formed on one surface (either the front or back surface) of a translucent plastic sheet using electron beam evaporation. In Examples 7-12, a metal oxide layer was formed on both surfaces (both the front and back surfaces) of the translucent plastic sheet using electron beam evaporation. The metal oxide layer consisted of an aluminum oxide vapor-deposited film, a silicon oxide vapor-deposited film, or a silicon oxide-aluminum oxide vapor-deposited film. Aluminum oxide particles, silicon oxide particles, or both aluminum oxide particles and silicon oxide particles were used as the vapor deposition source in a crucible. The thickness of the metal oxide layer, the proportion of silicon oxide in the metal oxide layer, and the proportion of aluminum oxide are shown in the table in Figure 8. Film thickness adjustment was performed using a quartz crystal film thickness gauge. The silicon oxide-aluminum oxide mass ratio composition was measured using an X-ray fluorescence analyzer (Rigaku Corporation's "ZSX Primus IV") according to a pre-prepared calibration curve.

[0037] In Examples 1-6, 13, and Comparative Examples 1-5, the above-described photocatalytic coating solution 1 (0.05 wt% Pt-WO3 + first and second binders) was applied onto a metal oxide layer using a #5.5 wireless bar coater (OSP-12 manufactured by OSG System Products), and the coated material was dried in a constant temperature bath set to 80°C for 1 hour to obtain a photocatalytic sheet. As the photocatalytic coating solution 1 dries on the metal oxide layer, it is thought that a dehydration condensation reaction occurs between two silanol groups (SiOH) contained in the first and second binders, a dehydration condensation reaction occurs between the hydroxyl groups (OH) on the surface of the metal oxide layer and the silanol groups contained in the first or second binder, and a dehydration condensation reaction occurs between the hydroxyl groups (OH) on the surface of the tungsten oxide particles and the silanol groups (SiOH) contained in the first or second binder. The first and second binders are thought to become siloxane compounds (dehydration condensates of the first and second binders) that are chemically bonded to the surface of the metal oxide layer and the surface of the tungsten oxide particles.

[0038] In Examples 7-12, the above-mentioned photocatalytic coating solution 1 (0.05 wt% Pt-WO3 + first and second binders) was applied to the metal oxide layer on the surface using a #5.5 wireless bar coater (OSP-12, manufactured by OSG System Products), and the coated material was dried in a constant temperature bath set to 80°C for 1 hour to form the photocatalytic layer on the surface. Subsequently, the above-mentioned photocatalytic coating solution 2 (TiO2 + first and second binders) was applied to the metal oxide layer on the back surface using a #5.5 wireless bar coater, and the coated material was dried in a constant temperature bath set to 80°C for 1 hour to form the photocatalytic layer on the back surface and obtain a photocatalytic sheet. As the photocatalytic coating solution 2 dries on the metal oxide layer, it is thought that a dehydration condensation reaction occurs between two silanol groups (SiOH) contained in the first and second binders, a dehydration condensation reaction occurs between the hydroxyl groups (OH) on the surface of the metal oxide layer and the silanol groups contained in the first or second binder, and a dehydration condensation reaction occurs between the hydroxyl groups (OH) on the surface of the titanium oxide particles and the silanol groups (SiOH) contained in the first or second binder. The first and second binders are thought to become siloxane compounds (dehydration condensates of the first and second binders) that are chemically bonded to the surface of the metal oxide layer and the surface of the titanium oxide particles.

[0039] Evaluation of the homogeneity of the photocatalytic layer The homogeneity of the photocatalytic layer was evaluated by visually observing the photocatalytic layer of the photocatalytic sheets in Examples 1-13 and Comparative Examples 1-5. The evaluation results are shown in the table in Figure 8. In this evaluation, photocatalytic sheets in which defects such as holes or indentations were observed in the photocatalytic layer were evaluated as "×", and photocatalytic sheets in which no defects were found were evaluated as "〇". The photocatalytic sheets in Examples 1-13 and Comparative Examples 1, 2, and 5 were evaluated as "〇". In these photocatalytic sheets, it is thought that a highly homogeneous photocatalytic layer was formed because the wettability of the surface of the metal oxide layer to the photocatalytic coating solution was high. The photocatalytic sheets in Comparative Examples 3 and 4 were evaluated as "×". In these photocatalytic sheets, it is thought that defects occurred in the photocatalytic layer because the wettability of the surface of the metal oxide layer to the photocatalytic coating solution was low.

[0040] Durability Test Durability tests were conducted on the photocatalytic layer of the photocatalytic sheets in Examples 1-13 and Comparative Examples 1-5. Specifically, four strips of mending tape (3M "Model No. 810-3-12" cut to a length of 50 mm and a width of 12 mm) were attached in parallel to the surface of the photocatalytic layer. Next, the four strips of mending tape were peeled off the surface of the photocatalytic layer. The adhesive surfaces of the four peeled-off strips of mending tape were visually inspected to check for any adhesion of the peeled-off photocatalytic layer. Based on these observations, the durability of the photocatalytic layer was evaluated, and the evaluation results are shown in the table in Figure 8. In Figure 8, a "○" indicates a photocatalytic sheet in which no adhesion of the peeled-off photocatalytic layer was observed on any of the four strips of mending tape, and a "×" indicates a photocatalytic sheet in which adhesion of the peeled-off photocatalytic layer was observed on two or more of the four strips of mending tape.

[0041] The durability of the photocatalytic layer in the photocatalytic sheets of Examples 1 to 13 was evaluated as "○". It was found that the photocatalytic layers of these photocatalytic sheets possess excellent durability. The durability evaluation of the photocatalytic layer in the photocatalytic sheets of Comparative Examples 1 to 5 was "×". In Comparative Example 1, the low durability of the photocatalytic layer is thought to be due to the thinness of the metal oxide layer. In Comparative Example 2, the high thickness of the metal oxide layer is thought to be due to the low durability of the photocatalytic layer. In Comparative Examples 3 and 4, defects were observed in the photocatalytic layer, which is thought to be due to the low durability of the photocatalytic layer. In Comparative Example 5, the low durability of the photocatalytic layer is thought to be due to the thinness of the translucent plastic sheet (substrate).

[0042] The table in Figure 8 also shows the overall evaluation. In the table in Figure 8, the overall evaluation for Examples 1 to 13, where both the homogeneity evaluation and the durability evaluation were "○", was "○", while the overall evaluation for Comparative Examples 1 to 5, where at least one of the homogeneity evaluation or durability evaluation was "×", was "×". [Explanation of Symbols]

[0043] 2: Translucent plastic sheet 3a, 3b: Photocatalytic layer 4a, 4b: Metal oxide layer 5: Air channel 6: First main surface 7: Second main surface 8: Light source unit 9: Fan 10: Housing 11: Intake port 12: Exhaust port 20: Photocatalytic sheet 30: Photocatalytic sheet laminate 40: Deodorizing unit

Claims

1. The material comprises a translucent plastic sheet having first and second main surfaces, a first photocatalyst layer provided on the first main surface, and a first metal oxide layer provided between the first main surface and the first photocatalyst layer. The first photocatalytic layer is in contact with the first metal oxide layer. The first metal oxide layer is an aluminum oxide vapor-deposited film or a silicon oxide-aluminum oxide vapor-deposited film. A photocatalytic sheet characterized in that, when the first metal oxide layer is a silicon oxide-aluminum oxide vapor-deposited film, the ratio of the mass b of silicon oxide to the mass a of aluminum oxide in the first metal oxide layer (b / a) is (0.001 / 100) or more and (80 / 20) or less.

2. The photocatalytic sheet according to claim 1, wherein the thickness of the first metal oxide layer is 0.1 μm or more and 0.5 μm or less.

3. The photocatalytic sheet according to claim 1, wherein the thickness of the translucent plastic sheet is 7 μm or more and 500 μm or less.

4. The present invention further comprises a second photocatalytic layer provided on a second main surface, and a second metal oxide layer provided between the second main surface and the second photocatalytic layer. The second photocatalytic layer is in contact with the second metal oxide layer. The second metal oxide layer is an aluminum oxide vapor-deposited film or a silicon oxide-aluminum oxide vapor-deposited film. The photocatalytic sheet according to claim 1, wherein, when the second metal oxide layer is a silicon oxide-aluminum oxide vapor-deposited film, the ratio of the mass b of silicon oxide to the mass a of aluminum oxide in the second metal oxide layer (b / a) is (0.001 / 100) or more and (80 / 20) or less.

5. The photocatalytic sheet according to claim 4, wherein the thickness of the second metal oxide layer is 0.1 μm or more and 0.5 μm or less.

6. The first photocatalytic layer comprises photocatalytic particles and a siloxane compound. The photocatalytic sheet according to claim 1, wherein the proportion of the siloxane compound in the first photocatalytic layer is 0.5 wt% or more and 30 wt% or less.

7. The photocatalytic sheet according to claim 6, wherein the siloxane compound is bonded to both the first metal oxide layer and the photocatalytic particles.

8. The photocatalytic sheet according to claim 6, wherein the siloxane compound comprises a silicon atom bonded to three oxygen atoms.

9. The photocatalytic sheet according to any one of claims 1 to 8 is laminated in a laminated structure or a wound structure, The laminated structure or the wound structure is a photocatalytic sheet laminate having air channels between the photocatalytic sheets.

10. A deodorizing unit comprising a photocatalytic sheet according to any one of claims 1 to 8, and a light source unit provided to irradiate the photocatalytic sheet with light.

11. The deodorizing unit according to claim 10, further comprising a fan provided so as to allow air to flow parallel to the photocatalytic sheet.

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