Photocatalyst coated body

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention is suitable for preventing contamination of outer walls of automobiles, ships, aircraft, buildings, etc., windowpanes, transparent plastic members, etc., for preventing fogging, for shielding ultraviolet rays, etc., and also has a photocatalyst coating having excellent weather resistance. Regarding the body.

【0002】

[Problems to be solved by conventional techniques and inventions]

Recently, the photoactivity of titanium oxide has attracted attention, and its use in various applications such as air purification, sterilization, deodorization, anti-fog, water purification, and self-cleaning has been proposed. There are three types of titanium oxide crystal structure: high-temperature rutile type, low-temperature anatase type, and tetragonal brucite type, which belong to the tetragonal system, but the most commonly used is the tetragonal type. There are two crystal types, rutile type titanium oxide is widely used, but anatase type has higher photocatalytic activity.

【0003】

Titanium oxide having such photoactivity exhibits strong oxidizing power on the surface when it absorbs ultraviolet rays of 400 nm or less, and decomposes compounds in contact with the surface. Therefore, for example, when pollutants or odorous substances adhere to the surface containing titanium oxide, those substances are oxidatively decomposed, and the effects of stain prevention and deodorization are exhibited. In addition, when it absorbs light rays such as ultraviolet rays, the surface becomes superhydrophilic and water droplets are not formed, so that it exhibits anti-fog properties.

【0004】

When a photocatalyst is used by adhering it to an outer wall material, window glass, etc. for the above purpose, the surface (outer surface) exposed to the outside air has sufficient weather resistance to withstand harsh climatic conditions and removes stains due to rain, etc. Easy properties (self-cleaning) are required, and the surface facing the room (inner surface) must sufficiently exhibit photoactivity such as air purifying action, bactericidal action, deodorizing action, and antifogging action. In order to improve the weather resistance and durability of the photocatalyst layer, it is necessary to make the particle size of the titanium oxide particles relatively large or to fix the titanium oxide particles with a weather resistant resin, but this tends to reduce the photoactivity. is there. On the other hand, in order to obtain sufficient light activity was relatively small particle size of the titanium oxide particles Ri, it is necessary or increase the exposure of the titanium oxide particles, Then weather resistance and durability is lowered, pollution The adsorptivity of substances tends to increase. Therefore, there is a demand for a technique capable of forming a photocatalyst layer that simultaneously satisfies photoactivity and weather resistance in a member used for applications such as blocking the room from the outside air.

【0005】

Therefore, an object of the present invention is to have sufficient weather resistance, durability and self-cleaning property on the outer surface of a base material such as an outer wall material, a window glass, a transparent plastic member, etc. used for blocking the room from the outside air as well as photoactivity. The present invention provides a photocatalyst coating body provided with a photocatalyst layer and a photocatalyst layer having high photoactivity on the inner surface.

【0006】

[Means for solving problems]

As a result of diligent studies in view of the above objectives, the present inventors satisfy the above requirements by forming photocatalytic layers containing titanium oxide particles having different average particle sizes on one surface and the other surface of the base material. It was discovered that a photocatalytic coating can be obtained. The present inventors also improve the weather resistance, durability and self-cleaning property of the photocatalyst layer on the outer surface by using a fluororesin having sufficient durability as a binder for the photocatalyst layer on the surface exposed to the outside air. I found that I could do it. The present invention has been completed based on such findings.

【0007】

That is, the photocatalyst coating body of the present invention has photocatalyst layers on both sides of the base material, and the first photocatalyst layer formed on one surface of the base material contains photocatalyst particles having an average particle size of 30 to 100 nm. The second photocatalyst layer containing and formed on the other surface is characterized by containing photocatalyst particles having an average particle size of 5 to 25 nm.

【0008】

By dispersing the photocatalyst particles in the first photocatalyst layer in a binder made of a fluororesin, excellent durability, weather resistance and self-cleaning property can be exhibited. Further, the photocatalyst particles in the second photocatalyst layer are dispersed in a binder made of a ceramic sol and exhibit high photoactivity.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

[1] Composition of photocatalyst coating [A] First Example In the photocatalyst coating body according to the first embodiment of the present invention, as shown in FIG. 1, a first photocatalyst layer 2 containing photocatalyst particles having an average particle size of 30 to 100 nm is formed on one surface of the base material 1. A second photocatalyst layer 3 containing photocatalyst particles having an average particle size of 5 to 25 nm is formed on the other surface.

【0010】

(1) Base material As the base material 1, metal, ceramics, resin, wood, or a composite thereof can be used. It can be selected according to the application after processing as a photocatalyst coating body, and the size and shape of the base material are not particularly limited. In particular, in the case of a transparent glass plate or plastic plate, an ultraviolet absorbing effect can be utilized in addition to a pollution preventing effect, a self-cleaning effect, an antifogging effect, a deodorizing effect, a bactericidal effect and the like.

【0011】

(2) First photocatalyst layer (a) Photocatalytic particles The first photocatalyst layer 2 is a layer exposed to the outside air, and the average particle size of the titanium oxide particles in the layer is 30 to 100 nm. If the average particle size of the titanium oxide particles is less than 30 nm, the weather resistance of the first photocatalyst layer 2 is insufficient, and if it exceeds 100 nm, the photoactivity decreases.

【0012】

(b) Binder In order to fix the titanium oxide particles to the surface of the substrate, the titanium oxide particles are uniformly dispersed in the binder. As the binder, a fluororesin having excellent weather resistance and durability and being inert to titanium oxide particles is used. Examples of the fluororesin that can be used include polytetrafluoroethylene, polyvinylidene fluoride resin, vinyl ether-fluoroolefin copolymer, vinyl ester-fluoroolefin copolymer and the like. A cross-linking agent, a dispersant, or the like may be blended in the binder.

【0013】

(c) Blending ratio The compounding ratio (weight ratio) of the titanium oxide particles and the binder resin is preferably 1: 9 to 9: 1, and more preferably 2: 8 to 8: 2. If the weight ratio of the titanium oxide particles / binder resin is less than 1: 9, the photoactivity is insufficient, and if it exceeds 9: 1, the weather resistance and durability of the first photocatalyst layer 2 are lowered.

【0014】

(d) Thickness The thickness of the first photocatalyst layer 2 is preferably about 0.5 to 50 μm. If the thickness of the first photocatalyst layer 2 is less than 0.5 μm, the photoactivity is insufficient, and if it exceeds 50 μm, the quality becomes excessive. A more preferred thickness is 1.0 to 20 μm. In general, it is preferable to make the thickness of the first photocatalyst layer 2 as thin as possible from the viewpoint of preventing distortion of transmitted light such as window glass and maintaining the light transmittance.

【0015】

(3) Second photocatalyst layer (a) Photocatalytic particles The second photocatalyst layer 3 is a layer facing the room, and the average particle size of the titanium oxide particles in the second photocatalyst layer 3 is 5 to 25 nm. If the average particle size of the titanium oxide particles is less than 5 nm, the photoactivity is insufficient, and if it exceeds 25 nm, the weather resistance of the second photocatalyst layer 3 becomes insufficient.

【0016】

(b) Binder The second photocatalyst layer 3 preferably contains a binder that uniformly disperses the titanium oxide fine particles. It is preferable to form the binder from the ceramic sol in order to maintain the activity of titanium oxide, improve the adhesion to the substrate, improve the strength of the photocatalyst layer, and the like. As a ceramic sol for a binder, the general formula: M (OR)_n(However, M is a metal element other than titanium, R is an alkyl group, and n is the oxidation number of the metal element.) It is preferable that the metal alkoxide obtained by the sol-gel method is obtained. Silicon alkoxide is preferable as the metal alkoxide for the binder, for example, Si (OCH).₃) ₄, Si (OC₂H₅) ₄, Si (i-OC₃H₇) ₄, Si (t-OC)₄H₉) ₄And so on. Also aluminum alkoxides (eg Al (OCH)₃)₃, Al (OC₂H₅)₃, Al (i-OC₃H₇) ₃, Al (t-OC₄H₉) ₃Etc. may be used.

【0017】

(c) Blending ratio In the second photocatalyst layer 3, the compounding ratio (weight ratio) of the titanium oxide fine particles and the binder is preferably about 50/50 to 80/20. If the proportion of the titanium oxide fine particles is less than 50% by weight, the photocatalytic activity is insufficient, and if it exceeds 80% by weight, the strength of the second photocatalytic layer 3 becomes insufficient.

【0018】

(d) Thickness The thickness of the second photocatalyst layer 3 is preferably 0.5 to 3.0 μm. There is no photocatalytic activity below 0.5 μm, and there is little further improvement in photoactivity above 3.0 μm.

【0019】

[B] Second Example In the case of a base material 1 containing a component having reactivity with titanium oxide such as sodium such as window glass, when a photocatalyst layer made of titanium oxide is directly formed, titanium oxide and sodium react with each other to increase photoactivity. Since there is a risk of deterioration, it is preferable to form the barrier layer 4 on the base material 1 in advance by a vapor deposition method as shown in FIG. Although the barrier layer 4 is shown only under the second photocatalyst layer 3 in FIG. 2, it may be formed under the first photocatalyst layer 2.

【0020】

The barrier layer 4 deposited on at least one surface of the base material 1 is generally made of oxide-based ceramics. Silicon oxide (SiO), especially in consideration of the affinity with the components in the photocatalyst layer formed above.₂) Or titanium oxide (TiO₂) Is preferable.

【0021】

Examples of the vapor deposition method for the barrier layer 4 include a sputtering method, a vacuum vapor deposition method, a CVD method, and an ion plating method. Oxide-based ceramics such as silicon oxide do not have a particular affinity for plastics. Therefore, when the base material 1 is a plastic, in order to improve the denseness of the barrier layer 4 and the adhesion to the base material 1. , It is necessary to use the vapor deposition method. Further, since the vapor-deposited layer of the oxide-based ceramics can be made very thin, deformation stress is not applied to the base material 1 after the formation of the barrier layer 4, and deformation of the base material 1 can be prevented.

【0022】

The thickness of the barrier layer 4 is preferably 30 to 300 nm. If the thickness of the barrier layer 4 is less than 30 nm, the separation between the base material 1 and the second photocatalyst layer 3 is insufficient, and fine cracks occur in the second photocatalyst layer 3. Further, even if the thickness of the barrier layer 4 exceeds 300 nm, the base material protection effect cannot be further improved. A more preferred thickness of barrier layer 4 is 50-100 nm.

【0023】

[2] Method for manufacturing photocatalyst coating [A] Formation of first photocatalytic layer As the coating liquid for forming the first photocatalyst layer 2, it is preferable that titanium oxide fine particles or sol and a fluororesin are dissolved and dispersed in an appropriate solvent. Titanium oxide sol is a sol-gel hydrolysis intermediate product of titanium alkoxide. In the sol-gel method, titanium alkoxide is used as a starting material, and the compound is hydrolyzed and polymerized in a solution to obtain sol fine particles of a metal oxide or hydroxide. A preferred example of titanium alkoxide is Ti (OCH).₃) ₄, Ti (OC₂H₅) ₄, Ti (i-OC₃H₇) ₄, Ti (t-OC)₄H₉) ₄And so on. The titanium oxide fine particles may be gelled titanium oxide sol.

【0024】

In order to uniformly apply the coating liquid containing titanium oxide on the base material 1 or the barrier layer 4, a spin coating method, a doctor blade coating method, a spray method, or the like is used. After application and drying, bake at room temperature to 350 ° C if necessary.

【0025】

[B] Formation of second photocatalytic layer As the coating liquid for forming the second photocatalyst layer 3, it is preferable that the coating liquid contains a mixture of a titanium oxide sol and a ceramic sol other than titanium oxide as a main component. After coating and drying in the same manner as in the first photocatalyst layer 2, the titanium oxide sol and other ceramic sol are gelled (solidified) by leaving it in the air or heat-treating it to room temperature to 200 ° C.

【0026】

[3] Action of each photocatalytic layer The first and second photocatalyst layers 2 and 3 formed by the above method have the following actions. (B) Since pollutants, odorous substances, fungi, etc. adhering to the surface of any photocatalyst layer are decomposed, they have a pollution prevention action, a self-cleaning action (self-cleaning action), a deodorizing action, a bactericidal action, and the like. (B) The second photocatalyst layer 3 has a superhydrophilic action (anti-fog action) due to water molecules (hydroxyl groups) adhering to the surface. (C) When the base material 1 is transparent, the action of reducing the amount of ultraviolet rays transmitted by absorbing the ultraviolet rays of titanium oxide can be utilized. (D) In particular, since the first photocatalyst layer 2 uses a fluororesin as a binder, it has excellent water repellency, weather resistance and durability.

【0027】

[Example]

The present invention will be described in more detail with reference to the following specific examples, but the present invention is not limited to those examples.

【0028】

Example 1 Fluorine-based resin-based coating liquid (trade name: Super Garako, manufactured by SOFT99 Corporation) 50 parts by weight (solid content standard) of titanium oxide fine particles (average particle size: 55 nm) are mixed with 100 parts by weight to make them uniform. A coating liquid for the first photocatalyst layer was prepared by dispersing in. A mixed solution (weight ratio: 50/50) of titanium oxide fine particles (average particle size: 6.8 nm) and silicon oxide sol was used as a coating solution for the second photocatalyst layer.

【0029】

A thin film of silicon oxide having a thickness of 80 nm was formed on one side of a transparent plate glass having a thickness of 1.0 mm by a vacuum vapor deposition method, and then a coating liquid for a first photocatalyst layer was applied to the surface without the thin film by a spray method. The first photocatalytic layer was formed by baking at 80 ° C after drying. Next, the coating liquid for the second photocatalyst layer was applied to the surface of the silicon oxide thin film by a spray method, and after drying, it was allowed to stand for 24 hours to solidify.

【0030】

The following experiments were performed on the obtained photocatalyst coating (test piece A) and the glass plate (test piece B) on which no photocatalyst layer was formed on any surface. (1) Anti-fog The surfaces of test pieces A and B were exposed to exhaled air to check for fogging, and then steam of warm water at 90 ° C. was contacted for 1 hour. As a result, in the test piece A, fogging did not occur on the second photocatalyst layer side, but in the test piece B, fogging occurred on both sides.

【0031】

(2) Contamination prevention Specimens A (with the first photocatalyst layer facing up) and B were left outdoors for 1 month, respectively, and the surface stains were observed with the naked eye. As a result, the first photocatalyst layer of the test piece A was significantly less contaminated than the surface of the test piece B. When water was sprayed onto each test piece with a hose, the dirt on the test piece A could be easily removed.

【0032】

(3) Deodorant When the test piece A was left in a room containing a small amount of ammonia gas for one week while being irradiated with ultraviolet rays, the odor was examined. As a result, the odor of ammonia in the room was significantly reduced.

【0033】

(4) Sterilization Mold was sprayed on the surface of the second photocatalyst layer of the test piece A and the surface of the test piece B, and left in a high humidity condition for one month. As a result, mold colonies were observed on the surface of the test piece B, but there was substantially no mold on the surface of the second photocatalyst layer of the test piece A.

【0034】

(5) UV shielding When the transmittance of the test piece A and the test piece B was measured by irradiating the test piece A with ultraviolet rays, the transmittance of the test piece A was 5% of the transmittance of the test piece B.

【0035】

From the above results, it can be seen that the photocatalytic coating material of the present invention has an excellent anti-fog effect, anti-contamination effect, deodorant effect, bactericidal effect and ultraviolet shielding effect.

【0036】

[Effect of the invention]

As described in detail above, the photocatalyst coating material of the present invention has photocatalyst layers containing titanium oxide having different average particle sizes on both sides of the substrate, while (first photocatalyst layer) is weather resistant in addition to photoactivity. It has properties and durability, and the other (second photocatalytic layer) has high photoactivity. Therefore, by setting the first photocatalyst layer on the side exposed to the outside air and the second photocatalyst layer on the side facing the room, excellent weather resistance, durability and self-cleaning property, as well as remarkable anti-pollution action and self-cleaning property are provided. It can exert its action, anti-fog property, deodorant action, bactericidal action, ultraviolet absorption action and the like. The photocatalyst coating material of the present invention having such characteristics can be used as long as it is a transparent base material such as glass, such as window glass and transparent plastic members for automobiles, ships, aircraft, etc., exterior materials for buildings, interior materials, and water around. Suitable for materials, window glass, etc.

[Simple explanation of drawings]

[Figure 1]

It is a partial cross-sectional view which shows the layer structure of the photocatalyst coating body by 1st Example of this invention.

[Figure 2]

It is a partial cross-sectional view which shows the layer structure of the photocatalyst coating body by 2nd Example of this invention.

[Explanation of symbols]

1 ... Base material 2 ... First photocatalyst layer 3 ... Second photocatalyst layer 4 Barrier layer