Photocatalyst member

The present invention relates to a photocatalyst member having a photocatalytic function, particularly a photocatalyst member having the lowest concentration of photocatalytic particles on the surface of the photocatalyst layer.

Various members have been developed that have a photocatalytic function by forming a photocatalytic layer on the surface of a base material such as ceramic, metal, or synthetic resin. It is used for carport roofing materials, soundproofing boards for highways, etc., and it is placed inside air purifiers and coolers by making it more hydrophilic and exhibiting hydrophilicity.

Among these members, roofing materials and soundproof plates made of synthetic resin have a problem that cracks occur due to thermal expansion and contraction of the synthetic resin base material because a photocatalyst layer is formed on the surface of the synthetic resin base material. was there. For this reason, a self-cleaning member has been developed in which a self-cleaning coating composition containing a trifunctional silicone resin, one of whisker, mica, talc, etc., and photocatalyst particles is applied to a base material. (Patent Document 1). In addition, a synthetic resin member having a photocatalytic function that eliminates the occurrence of cracks by reducing the thickness of the photocatalyst layer to 5 to 35 nm has also been developed (Patent Document 2). Further, there is also known a resin plate in which the concentration of photocatalyst particles contained in the photocatalyst layer is increased toward the surface side to enhance the photocatalyst function (Patent Document 3).<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2002-69376</text></patcit><patcit num="2"><text>Japanese Patent Application Laid-Open No. 2005-14350</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2004-98629</text></patcit>

<p> However, since the self-cleaning member of Patent Document 1 contains any of whiskers, mica, and talc, only a colored photocatalyst layer can be formed, and the self-cleaning member cannot be a translucent or transparent member. It was. Further, since the synthetic resin member of Patent Document 2 has a thin photocatalyst layer formed on the surface, when an object hits the member, the layer is scratched or peeled off, and the entire photocatalyst function is uniform. It had the problem of not being able to exert it. Further, the resin plate of Patent Document 3 has a problem that the photocatalyst particles existing on the surface side fall off and the photocatalyst layer is cracked. The present invention has been made to solve the above problems, and is to provide a photocatalyst member having a photocatalytic function, particularly a photocatalyst member in which photocatalyst particles of a photocatalyst layer are hard to fall off.</p>

<p> Therefore, the first photocatalyst member according to the present invention is a member formed by forming a photocatalyst layer on the surface of a synthetic resin base material, and the concentration of photocatalyst particles contained in the photocatalyst layer is the thinnest on the surface of the photocatalyst layer. It is characterized by being. In the present invention, it is preferable that a silica layer is further formed on the surface of the photocatalyst layer.</p><p> The second photocatalyst member according to the present invention is a member formed by forming a photocatalyst layer on the surface of a synthetic resin base material, and is characterized in that a silica layer is formed on the surface of the photocatalyst layer. ..</p><p> In the present invention, the thickness of the photocatalyst layer is preferably 5 to 35 nm, and the thickness of the silica layer is preferably 10 to 500 nm.</p>

<p> The first photocatalyst member of the present invention exerts a photocatalytic function by the photocatalyst particles contained in the photocatalyst layer, decomposes malodor, exerts antibacterial / antifungal action, and exhibits hydrophilicity. When the concentration of the photocatalyst particles contained in the photocatalyst layer is the thinnest on the surface of the photocatalyst layer, the photocatalyst particles are less likely to fall off even if an object hits them during transportation or installation, and a stable photocatalyst function is provided for a long period of time. Demonstrate. When the silica layer is formed on the surface of the photocatalyst layer, the silica layer protects the photocatalyst layer, so that the photocatalyst particles do not fall off even if they are hit by an object, and the photocatalyst particles are less likely to be scratched, which promotes the above effect. can do.</p><p> In the second photocatalyst member of the present invention, the silica layer formed on the surface of the photocatalyst layer makes it difficult for the photocatalyst layer to be scratched even if an object hits the member, and the photocatalyst particles do not peel off. The photocatalytic function can be exhibited for a long period of time.</p><p> In the present invention, even if a silica layer is formed on the surface of the photocatalyst layer, the reason why the photocatalytic function of the photocatalyst layer extends to the surface is not clear. However, the applicant may scatter the electrons and holes expressed in the photocatalytic layer, or the radical species, reactive oxygen species, chemical species, etc. expressed by them, or pass through the coarse and dense coarse part of the silica layer, or chain. At present, it is speculated that the photocatalytic function is exhibited despite the presence of the silica layer.</p><p> Further, when the thickness of the photocatalyst layer is as thin as 5 to 35 nm, the internal residual stress of the photocatalyst layer can be reduced, and even if the photocatalyst member thermally expands and contracts, the stress that causes cracks does not increase and cracks occur. I won't let you. Therefore, the appearance does not become cloudy due to light scattering of cracks, and the initial appearance can be maintained. When the base material is a translucent base material, it can be a photocatalyst member that retains the translucency for a long period of time. Further, when the photocatalyst member is colored, the initial hue can be maintained.</p><p> When the thickness of the outermost silica layer is 10 nm or more, the hard coat function can be exhibited, and the peeling and cracking of the photocatalyst layer due to hitting an object can be suppressed. The thicker the silica layer, the higher the surface hardness and rigidity, and the silica layer itself will not be scratched. However, if the thickness is 500 nm or more, the photocatalytic capacity will decrease. It is preferably about ~ 500 nm.</p>

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

FIG. 1 is a partially enlarged cross-sectional view showing an embodiment of the photocatalyst member of the present invention.

The photocatalyst member A shown in FIG. 1 is a plate-shaped member formed by forming an adhesive layer 2, a protective layer 3, and a photocatalyst layer 4 in this order on one surface of a synthetic resin base material 1 and laminating them. .. Then, the concentration of the photocatalyst particles contained in the photocatalyst layer 4 gradually increases from the surface toward the inside, and the surface of the photocatalyst layer 4 has the thinnest concentration. In addition, each of these layers may be formed on both sides of the base material 1. Moreover, the concentration of the photocatalyst particles may be changed stepwise.

The synthetic resin base material 1 may be formed of either a thermoplastic resin or a curable resin, but is preferably formed of a thermoplastic resin having good processability. As the thermoplastic resin, for example, a polycarbonate resin, an acrylic resin, a vinyl chloride resin, a polyethylene terephthalate resin, or the like is used. Among them, the above-mentioned resin having translucency is preferable, and further, since the polycarbonate resin has excellent impact resistance and translucency, a roofing material having a photocatalytic function, a carport roofing material, and a soundproof plate It can be used as a building material such as a wainscot or a carport, or as a road material.

The thickness of the base material 1 is not limited, and the shape thereof is not limited to a plate shape, but when used for the above-mentioned roofing material, carport, wainscot, etc., the thickness is 0.5 to 0.5 to 4 mm plate-shaped, corrugated plate-shaped, half-folded and other shapes are preferably used. Further, in the case of a soundproof plate, a plate-like plate having a thickness of 4 to 10 mm is used. Further, a base material 1 to which a heat ray absorbing function, a heat ray reflecting function, a weather resistance function, an electromagnetic wave absorbing function, an electromagnetic wave reflecting function, an antistatic function, a hard coat function and the like are added may be used.

The adhesive layer 2 is a layer formed by using an adhesive resin such as a urethane resin, an acrylic resin, a polyvinyl alcohol resin, a vinyl acetate resin, a thermoplastic epoxy resin, or a silicone resin. Among these adhesive resins, an acrylic resin that adheres well to the base material 1 and the protective layer 3 is most preferably used. The thickness of the adhesive layer 2 is preferably formed to be about 0.1 to 50 μm. If it is thinner than 0.1 μm, the adhesiveness may be poor and peeling may occur, and if it is thicker than 50 μm, the adhesiveness is not improved. It is a waste of material. A more preferable thickness is 1 to 10 μm.

The protective layer 3 is a layer for preventing the photocatalytic action of the photocatalyst layer 4 from acting on the adhesive layer 2 and even the synthetic resin base material 1, and is composed of an inorganic substance such as silica and a silicone resin such as polydimethylsiloxane. the composition is prepared by uniformly mixing a binder resin such as acrylic resin or fluorine resin, or made by forming a composition consisting of inorganic matter and organic matter, such as a copolymer resin of silicone resin and acrylic resin inorganic - Organic substances or silicone resins are used. The thickness of the protective layer 3 is preferably formed to be about 0.01 to 10 μm, and if it is thinner than 0.01 μm, the photocatalytic function cannot be effectively blocked, and the photocatalytic action extends to the adhesive layer 2 and the synthetic resin base material 1. It is not preferable because it deteriorates, and even if it is thicker than 10 μm, the blocking function is not further improved, which is a waste of material. A more preferable thickness is 0.5 to 5 μm.

At least one of the adhesive layer 2 or the protective layer 3 may contain an ultraviolet absorber. If the base material 1 has a weather resistant function, it may not be contained, but if the protective layer 3 contains an ultraviolet absorber, the deterioration of the adhesive layer 2 is prevented and the adhesive effect is maintained for a long period of time. It can also have the effect of maintaining. As the ultraviolet absorber, a benzotriazole-based, benzophenone-based, triazine-based, benzoate-based agent, or a light stabilizer (HALS) is used. Among them, those having a molecular weight of 390 or more of the ultraviolet absorber are preferably used.

The photocatalyst layer 4 is a layer formed by dispersing photocatalyst particles and silica or silicone resin in an amount of 1% by mass or less, if necessary, or a binder, and the photocatalyst particles contained in the photocatalyst layer 4. Is gradually increased or gradually increased from the surface of the photocatalyst layer toward the inside of the photocatalyst layer so that the surface of the photocatalyst layer 4 has the thinnest concentration. The photocatalytic particles exert photocatalytic functions such as decomposing malodor, antibacterial and antifungal action, and exhibiting hydrophilicity.

Since the photocatalyst layer 4 has the thinnest photocatalyst particle concentration on the surface of the photocatalyst layer 4, which is the surface of the member, the initial photocatalyst function is higher than that of the photocatalyst layer in which the surface particle concentration is uniformly or intentionally increased. Although it becomes weaker, if it is irradiated with ultraviolet rays for a little longer, the photocatalyst function is exhibited to the same extent, and for example, the photocatalyst member A having hydrophilicity with a water contact angle of 10 ° or less can be obtained. Since the concentration of the photocatalyst particles on the surface of the photocatalyst layer 4 is low, the photocatalyst particles are less likely to fall off even if an object hits the photocatalyst layer 4 during transportation or installation, and exhibits a stable photocatalyst function for a long period of time. It becomes possible to make it. Further, since the concentration of the photocatalyst particles is gradually increased from the surface of the photocatalyst layer toward the inside, the boundary inside the photocatalyst layer disappears, and peeling or cracking occurs inside the photocatalyst layer when an impact or a temperature change is applied. It becomes difficult to do.

Known photocatalyst particles are used, for example, titanium oxide, zinc oxide, tin oxide, SrTiO.₃, WO₃Metal oxides such as are used. Of these, titanium oxide, particularly anatase-type titanium oxide, is most preferably used because it exhibits a good photocatalytic function and is easily available. The photocatalyst particles are contained in the entire photocatalyst layer 4 in an amount of 5 to 50% by mass, so that the concentration of the photocatalyst particles on the surface is 0 to 5% by mass and the innermost concentration is 5 to 50% by mass. The concentration is gradually increased or gradually increased from the surface to the inside. When the total content of the photocatalyst particles is 5% by mass or less, it is difficult to exert the photocatalytic function. On the other hand, even if it is 50% by mass or more, the photocatalyst function is not further improved and the material is wasted, and when the binder component is insufficient and the strength of the film itself is lost and impact or temperature change is applied, the inside of the photocatalyst layer is applied. Peeling and cracking are likely to occur.

As the silica, an inorganic material mainly composed of silica such as a silica precursor and water glass, or a silicone resin is used alone or in combination, and even if a photocatalyst function acts on these, it does not deteriorate. This silica or the like is contained in the photocatalyst layer 4 in an amount of 95 to 50% by mass, and forms the photocatalyst layer 4 together with the photocatalyst particles.

It is desirable that the photocatalyst layer 4 has a thickness of 5 to 35 nm, more preferably 10 to 30 nm so that cracks do not occur. The reason why cracks do not occur when the thickness is within the above range is considered as follows. Since the photocatalyst layer 4 is an inorganic layer composed of photocatalyst particles and silica or silicone resin, when the residual stress inside the layer exceeds a certain level, cracks are generated to release the stress. And this tendency becomes larger as the thickness of the photocatalyst layer 4 becomes thicker. In the present invention, since the base material 1 is made of synthetic resin, when heat or the like is applied to the photocatalyst member A, the base material 1 thermally expands and contracts, and the photocatalyst layer 4 also tries to expand and contract accordingly, but mainly inorganic. The photocatalyst layer 4 cannot follow and the internal stress of the layer 4 becomes large, and when it exceeds a certain level, cracks are generated to release the internal stress. Therefore, by making the thickness of the photocatalyst layer 4 as thin as possible, it is possible to reduce the internal stress and prevent the occurrence of cracks. According to the results of the applicant's experiment, the thickness should be 35 nm or less. It was found that the photocatalyst layer 4 did not crack even when the base material 1 was formed of resin and expanded and contracted by heat. However, if the thickness is too thin, the photocatalytic function deteriorates too much, so it is preferable to set the thickness to 5 nm or more.

The method of laminating and integrating the adhesive layer 2, the protective layer 3, and the photocatalyst layer 4 on the base material 1 is not particularly limited, and can be produced by, for example, the following method.

One method is to change the mixing ratio of the photocatalyst particles and silica or silicone resin, add a small amount of dispersant or binder resin (1% by mass or less) as necessary, and several types uniformly dispersed in a solvent or water. A paint for a photocatalyst layer, a paint for a protective layer in which an inorganic substance such as silica and an organic substance such as a resin are uniformly dispersed in a solvent, and a paint for an adhesive layer in which an adhesive resin is uniformly dispersed in a solvent are produced. Then, the adhesive layer paint is applied to the surface of the synthetic resin base material 1 to form the adhesive layer 2, the protective layer paint is applied onto the protective layer 3 to form the protective layer 3, and the photocatalyst particle concentration is formed on the protective layer 3. The photocatalyst member A is manufactured by sequentially applying the paint for the photocatalyst layer in the order of the paint for the dark photocatalyst layer to the light paint to form the photocatalyst layer 4 whose concentration gradually decreases or the concentration changes stepwise to form the lightest concentration on the surface. can do.

Another method is to add one type of photocatalytic paint that is uniformly dispersed in a solvent or water by adding photocatalyst particles and silica or silicone resin in a fixed proportion, or if a dispersant or binder resin is required, in a very small amount. Further, the adhesive layer paint and the protective layer paint are prepared in the same manner as described above. Then, the adhesive layer paint and the protective layer paint are applied to the synthetic resin base material 1, respectively, to form the adhesive layer 2 and the protective layer 3, and the photocatalyst layer paint is applied on the protective layer 3. Then, since the dispersant and the binder are not present or only a very small amount is present in this photocatalytic paint, silica and titanium oxide are dispersed in a separated state, and the specific gravity is heavy in the applied photocatalytic paint. Titanium oxide sinks inside, and a photocatalyst layer 4 in which the photocatalyst particle concentration gradually increases from the surface of the photocatalyst layer toward the inside is formed on the protective layer 3, and the photocatalyst member A is manufactured.

In the photocatalyst member A thus obtained, the photocatalyst function of the photocatalyst particles contained in the photocatalyst layer 4 is exerted on the surface of the photocatalyst member A to decompose malodor, perform antibacterial and antifungal action, and so on. It exhibits hydrophilicity. Further, since the concentration of the photocatalyst particles in the photocatalyst layer 4 is the lowest on the surface thereof, the photocatalyst particles are less likely to fall off even if an object hits the photocatalyst member A, and a stable photocatalyst function is exhibited for a long period of time.

FIG. 2 is a partially enlarged cross-sectional view showing another embodiment of the photocatalyst member of the present invention.

The photocatalyst member B shown in FIG. 2 has a plate-like shape in which an adhesive layer 2, a protective layer 3, a photocatalyst layer 4, and a silica layer 5 are formed and laminated in this order on one surface of a synthetic resin base material 1. It is a member. Then, the concentration of the photocatalyst particles contained in the photocatalyst layer 4 gradually increases from the surface toward the inside, and the surface of the photocatalyst layer 4 has the thinnest concentration. In addition, each of these layers may be formed on both sides of the base material 1. Moreover, the concentration of the photocatalyst particles may be changed stepwise.

Since the synthetic resin base material 1, the adhesive layer 2, the protective layer 3, and the photocatalyst layer 4 of the photocatalyst member B are the same as the respective layers of the photocatalyst member A shown in FIG. 1, they are designated by the same reference numerals and the description thereof will be omitted. To do.

The silica layer 5 is a transparent layer made of silica which is an inorganic particle, and this silica does not decompose even if a photocatalytic function acts on it. Then, surface hardness and rigidity are imparted to the photocatalyst member B to make it difficult to damage during transportation or use, and even if an object hits the photocatalyst member B, the impact force is absorbed to make it difficult for the photocatalyst layer 4 to crack. , It is also possible to prevent the photocatalyst particles from falling off. The silica layer 5 is an inorganic layer formed by adding a small amount of an inorganic substance, a silicone resin, a dispersant, a binder, or the like to silica as a main component. The thickness of the silica layer 5 is preferably 10 to 500 nm. If the thickness is thinner than 10 nm, the surface hardness and rigidity of the silica layer 5 are not significantly improved, and if the thickness is 500 nm or more, the photocatalytic function is applied to the surface of the base material. It becomes impossible to demonstrate with. A more preferable thickness is 20 to 200 nm.

As described above, the reason why the photocatalyst function is exhibited on the surface of the photocatalyst member B even if the photocatalyst layer 4 is covered with the silica layer 5 is not clear at this time. However, when light is incident on the photocatalyst layer 4 through the transparent silica layer 5, the photocatalyst function is exerted, and the electrons and holes expressed in the photocatalyst layer, or the radical species, reactive oxygen species, chemical species, etc. expressed by them are scattered. At present, it is speculated that the photocatalyst is exhibited in spite of the presence of the silica layer by passing through the coarse and dense part of the silica layer, chaining, and the like.

Such a photocatalyst member B can be produced, for example, by the following method. Several types of paints for the photocatalyst layer, protective layer paints, and adhesive layer paints similar to those used in the production of the photocatalyst member A are prepared, and silica layer paints in which silica is dissolved in a solvent or water are prepared. To make. Then, the adhesive layer 2, the protective layer 3, and the photocatalyst layer 4 in which the concentration of the photocatalyst particles changes and the concentration on the surface becomes the thinnest are formed on the surface of the synthetic resin base material 1 in the same manner as described above, and further The photocatalyst member B can be manufactured by applying the silica layer paint to the silica layer 5 to form the silica layer 5.

FIG. 3 is a partially enlarged cross-sectional view showing still another embodiment of the photocatalyst member of the present invention.

The photocatalyst member C shown in FIG. 3 has a plate shape in which an adhesive layer 2, a protective layer 3, a photocatalyst layer 40, and a silica layer 5 are formed and laminated in this order on one surface of a synthetic resin base material 1. It is a member of. The photocatalyst particles contained in the photocatalyst layer 40 are uniformly dispersed and contained in the photocatalyst layer 40, unlike the above-described embodiments. In addition, each of these layers may be formed on both sides of the base material 1.

Since the synthetic resin base material 1, the adhesive layer 2, the protective layer 3, and the silica layer 5 of the photocatalyst member C are the same as the respective layers of the photocatalyst member B shown in FIG. 2, they are designated by the same reference numerals and the description thereof will be omitted. To do.

The photocatalyst layer 40 is a layer formed by uniformly dispersing photocatalyst particles and silica or silicone resin in an amount of 1% by mass or less of a dispersant or a binder, if necessary. The photocatalytic particles exert photocatalytic functions such as decomposing malodor, antibacterial and antifungal action, and exhibiting hydrophilicity. Since the photocatalyst particles contained in the photocatalyst layer 40 are uniformly dispersed, many photocatalyst particles are also present on the surface side, so that the photocatalyst function can be increased accordingly. Also in this embodiment, the photocatalyst function exhibited in the photocatalyst layer 40 is exhibited on the surface of the member C, but the reason why the photocatalyst function is exhibited even though the photocatalyst layer 40 is covered with the silica layer 5 is unclear. However, the applicant speculates as described above.

Such a photocatalyst member C can be produced, for example, by the following method. One type of paint for photocatalyst with a constant photocatalyst particle concentration and addition of a dispersant or binder (less than 1% by mass) was prepared in the same manner as above, and a paint for a protective layer used for manufacturing the photocatalyst member B. , Adhesive layer paint and silica layer paint are prepared respectively. Then, the adhesive layer 2 and the protective layer 3 are formed on the surface of the synthetic resin base material 1 in the same manner as described above, and the photocatalyst paint is further applied to form the photocatalyst layer 4 in which the photocatalyst particles are uniformly dispersed. The photocatalyst member C can be manufactured by applying the silica layer coating material on the silica layer 5 to form the silica layer 5.

Hereinafter, a specific description will be given based on the examples.

(Example 1) Photocatalyst Three types of photocatalyst layers having a blending ratio of fine powder of titanium oxide and silica of 1: 2, 1: 1, 2: 1 and photocatalytic particle concentrations of low concentration, medium concentration, and high concentration. A paint for a protective layer in which a polydimethylsiloxane and an acrylic resin were uniformly mixed, and a paint for an adhesive layer in which an acrylic adhesive resin was dissolved in a solvent were prepared. A low-concentration photocatalyst layer paint is applied to one side of the polyethylene terephthalate film, then a medium-concentration photocatalyst layer paint is applied, and then a high-concentration photocatalyst layer paint is applied and dried. The thinnest photocatalyst layer was formed on the side. Subsequently, the coating material for the protective layer was applied onto the photocatalyst layer and dried to form the protective layer. Further, a transfer film was produced by applying the coating material for an adhesive layer and drying it to form an adhesive layer.

The adhesive layer of the transfer film is laminated on the surface of a transparent polycarbonate resin base material having a thickness of 2 mm so as to be on the polycarbonate resin base material side and heat-bonded, and then the polyethylene terephthalate film is peeled off to form an adhesive layer of the transfer film. , The protective layer and the photocatalyst layer were transferred to the surface of the polycarbonate resin base material to prepare a plate-shaped translucent polycarbonate resin plate.

1mW / cm with a black light blue (BLB) lamp on the photocatalytic layer of this resin plate²Each test piece a, b, c, d was prepared by irradiating with the ultraviolet rays of the above for 24 hours, 48 hours, 72 hours, and 96 hours. 20 ml of ion-exchanged water was dropped onto the test piece e before irradiation of the BLB lamp and each test piece a, b, c, d after irradiation using a microsyringe, and the water droplets on the surface of each test piece were image-processed. Using (CA-A, manufactured by Kyowa Interface Science Co., Ltd.), the contact angle of each test piece was measured by the 3-point method.

As a result, the test piece a irradiated for 24 hours was 72 °, the test piece b irradiated for 48 hours was 52 °, the test piece c irradiated for 72 hours was 39 °, and the test piece d irradiated for 96 hours was 3 °. The contact angles were shown respectively, but the test piece e that was not irradiated with the BLB lamp was 78 ° and did not exhibit hydrophilicity. Further, as compared with the test piece g of Comparative Example 1 described later, the test piece g shows a contact angle of 5 degrees in 24 hours, and the irradiation time required for this resin plate to have the same contact angle is long. Although it took time, it was found that the same degree of hydrophilicity was exhibited by irradiating over time.

Further, a fastness test was carried out on the photocatalyst layer of this resin plate using a test device compliant with JIS L0823-1971 (friction tester for dye fastness test). A gold cloth No. 3 was used for the wiping cloth, and it was confirmed whether the photocatalyst layer remained after 100 round trips with a load of 200 g. As a result, it was found that the photocatalyst layer remained and the photocatalyst particles did not fall off.

(Example 2) A coating material for a silica layer was prepared in which silica was uniformly dispersed in a solvent. A paint for a silica layer is applied to one side of a polyethylene terephthalate film to form a silica layer, and then the paint for a medium-concentration photocatalyst layer used in Example 1 is applied and dried to form a photocatalyst layer. Further, the protective layer paint is applied onto the photocatalyst layer and dried to form a protective layer, and further, the adhesive layer paint is applied and dried to form an adhesive layer to prepare a transfer film. did. Then, as in Example 1, this transfer film is thermocompression-bonded to a polycarbonate resin substrate and transferred, and an adhesive layer, a protective layer, a photocatalyst layer, and a silica layer are formed on the surface of the polycarbonate resin substrate, respectively, in a plate shape. A translucent polycarbonate resin plate was prepared.

The photocatalyst layer of this resin plate was irradiated with ultraviolet rays for 96 hours in the same manner as in Example 1 to obtain a test piece f. When the contact angle of this test piece f was measured, it showed a contact angle of 5 °. From this result, it was found that the resin plate of Example 2 exerts a photocatalytic function in spite of the presence of a silica layer on the surface. Further, when the above-mentioned fastness test was carried out on the photocatalyst layer of this resin plate, the photocatalyst particles of the photocatalyst layer did not fall off.

(Comparative Example 1) A paint for a medium-concentration photocatalyst layer was prepared by adjusting the mixing ratio of the fine powder of photocatalytic titanium oxide and silica to 1: 1 and adding 2% by mass of a dispersant and 3% by mass of a binder resin. The protective layer paint and the adhesive layer paint used in Example 2 were prepared. Then, these were applied to a polyethylene terephthalate film and dried to form a photocatalyst layer, a protective layer, and an adhesive layer having a uniform photocatalyst particle concentration to prepare a transfer film. Then, as in Example 1, this transfer film is thermocompression-bonded to a polycarbonate resin substrate and transferred to form an adhesive layer, a protective layer, and a photocatalyst layer on the surface of the polycarbonate resin substrate. A resin plate was prepared.

The photocatalyst layer of this resin plate was irradiated with ultraviolet rays for 24 hours in the same manner as in Example 1 to obtain a test piece g. When the contact angle of this test piece g was measured, it showed a contact angle of 5 °. Further, when the photocatalyst layer of this resin plate was subjected to a fastness test in the same manner as in Examples 1 and 2, the photocatalyst particles of the photocatalyst layer fell off.

From this result, the test piece g in which the photocatalyst layer in which the photocatalyst particles are uniformly dispersed is formed on the surface of the resin plate has a lower photocatalyst particle concentration in the surface portion than the test pieces a, b, c, and d. It was found that the required contact angle was obtained by short-time irradiation. However, when a fastness test was carried out on this photocatalyst layer, it was found that the photocatalyst particles fell off and did not have a long-term function.

<figref num="1">It is a partially enlarged sectional view which shows one Embodiment of this invention.</figref><figref num="2">It is a partially enlarged sectional view which shows the other embodiment of this invention.</figref><figref num="3">It is a partially enlarged sectional view which shows still another Embodiment of this invention.</figref>

Code description

A, B, C Photocatalyst member 1 Synthetic resin base material 2 Adhesive layer 3 Protective layer 4, 40 Photocatalyst layer 5 Silica layer