Hydrophilicity-imparting material, hydrophilicity-exhibiting material, and their production

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a hydrophilicity-imparting material that imparts hydrophilicity to the surface of a substrate, a hydrophilicity-demonstrating material that exhibits hydrophilicity on the surface of the substrate, and a method for producing the same.

【0002】

[Conventional technology]

Conventionally, fogging prevention has been known as an advantage of imparting hydrophilicity to the surface of a base material. For example, by imparting hydrophilicity to the surface of glass or lens, fogging of these glass or lens can be prevented. Therefore, various techniques as described below have been proposed.

【0003】

The simplest method is to apply an antifogging composition containing a hydrophilic organic compound such as polyethylene glycol to the surface of a base material to form an antifogging film. In addition, a technique has been proposed in which the polymer layer provided on the surface of the base material is subjected to ultraviolet irradiation, alkali treatment, etc. to generate acidic groups in the polymer layer, and the presence of these acidic groups makes the surface of the polymer layer hydrophilic. (Actual Kaihei 3-129357). In addition, we also know a technique for forming a graft polymer film by graft-polymerizing an acrylic monomer having a hydrophilic group and a monomer having a hydrophobic group from the beginning, and making the film surface hydrophilic by the presence of the hydrophilic group and the hydrophobic group. (Actual Kaihei 5-68006).

【0004】

By the way, in recent years, it has been discovered that the surface can be prevented from becoming dirty by making the surface hydrophilic (Polymer, Vol. 44, May 1995, p.307). For this reason, attempts are being made to form a coating film made of a hydrophilic graft polymer on the outer wall of a building or the body of a vehicle such as an automobile or a train to prevent stains on these surfaces.

【0005】

[Problems to be Solved by the Invention]

However, the above-mentioned conventional technique has the following problems. The antifogging film formed on the surface of the base material is only temporarily present on the surface of the base material due to the application of the composition, and is relatively easily removed by washing the surface of the base material with water or the like. Therefore, the anti-fog effect cannot be obtained within a short period of time. Further, in the polymer layer having a hydrophilic surface, the hydrophilicity of the surface is lost with the passage of time due to the influence of the adhering contaminants, and the antifogging effect is also lowered accordingly.

【0006】

Hydrophilicity can be converted by the contact angle with water, and the smaller the contact angle, the better the wettability with water, and the more difficult it is for water that comes into contact with the hydrophilic surface to stay on the contact surface. If the water does not stop easily in this way, the dirt components such as urban dust contained in rainwater and the like flow down from the hydrophilic surface together with the water, and the dirt prevention effect is enhanced. However, in the graft polymer to which hydrophilicity is imparted as described above, water is relatively easy to stop on the surface because the hydrophilicity converted by the contact angle with water is about 30 to about 40 °. , The antifouling effect and the antifogging effect were not always sufficient. In addition, inorganic dust represented by clay minerals has a contact angle with water of about 20 to about 50 °, and therefore exhibits an affinity with a graft polymer having the above contact angle and easily adheres to the surface of the graft polymer. .. In combination with this, it has been difficult for the coating film or film of the graft polymer to exhibit a high antifouling effect particularly against inorganic dust.

【0007】

The present invention has been made to solve the above problems, and to provide a new material which imparts high hydrophilicity to the surface of a base material reliably and for a long period of time and which has high hydrophilicity reliably and for a long period of time. Is the purpose.

【0008】

[Means for solving problems and their actions / effects]

In order to solve such a problem, the hydrophilicity-imparting material of the first invention is a hydrophilicity-imparting material that imparts hydrophilicity to the surface of the base material, and generates excitation electrons and holes by the energy of the irradiated light. It contains a photocatalyst that functions as a catalyst and generates a hydroxyl group through the generation of a hydroxyl radical in the presence of water or water and oxygen on the surface of the catalyst, and a compound that has the property of chemically adsorbing the hydroxyl group. Is chemically adsorbed and retained on the surface of the photocatalyst and the compound, and the retained hydroxyl group imparts hydrophilicity.

【0009】

In the hydrophilicity-imparting material of the first invention having the above structure, a hydroxyl group is generated by a photocatalyst when irradiated with light, and the generated hydroxyl group is chemically adsorbed and retained on the surface of the compound as well as the photocatalyst. Since the water content (water vapor in the air, rainwater, etc.) on the surface of the catalyst does not become zero, it can be said that hydroxyl groups are constantly generated while the light is irradiated. Therefore, the hydroxyl groups are held at an extremely high density, and the holding is performed by a bond called chemisorption, so that it can be said that the hydroxyl groups are firmly held. On the other hand, while the photocatalyst does not generate hydroxyl groups while the light is not irradiated, the hydroxyl groups that have been generated up to that point are firmly retained on the surface of the photocatalyst and the compound, and the hydroxyl groups may be inadvertently removed. Absent. Moreover, if the light is irradiated again, even if the density of the hydroxyl groups has decreased by then, the state of holding the high density is quickly restored. Therefore, if the hydrophilicity-imparting material of the first invention is fixed to the surface of some base material, the surface of the base material can be surely made highly hydrophilic, and this high hydrophilicity can be surely maintained for a long period of time. Therefore, if the hydrophilicity-imparting material of the first invention is fixed to the surface of the inner and outer walls of a building or the surface of a vehicle body such as an automobile or a train, the high hydrophilicity imparted in this way provides a high antifouling effect. Can be done. In this case, if it rains occasionally on these surfaces, the dust and pollutants on the surface will be washed away from the surface together with the rainwater due to the high hydrophilicity imparted to these surfaces, and these surfaces will be self-cleaned. .. That is, so-called rain streak stains in which dust or the like remains on the streaks along the flow of water are effectively suppressed. Further, if the hydrophilicity-imparting material of the first invention is fixed to the surface of glass, a lens, a mirror, or the like, it is possible to obtain a high antifogging effect with high hydrophilicity.

【0010】

In the hydrophilicity-imparting material of the first invention having the above structure, the following aspects can be adopted. In the first aspect, in imparting hydrophilicity, it is preferable to impart hydrophilicity of about 10 ° or less in terms of the contact angle with water.

【0011】

In this way, the antifogging effect on the surface of the base material on which the hydrophilicity-imparting material of the present invention is fixed is further enhanced, which is preferable. Further, since the contact angle in this first aspect is extremely lower than the contact angle of urban dust containing a large amount of lipophilic components and inorganic dust such as clay minerals, the group to which the hydrophilicity-imparting material of the present invention is fixed is fixed. These dusts do not exert an affinity on the surface of the material, and the stain prevention effect can be further enhanced, which is preferable. As the contact angle approaches zero degrees, the hydrophilicity increases and water diffuses on the film on the surface of the base material and easily flows. Therefore, not only the above-mentioned urban dust but also inorganic dust easily flows down from the surface of the base material together with water. In this case, in order to enhance the stain prevention effect, it is more preferable that the contact angle is about 5 ° or less and close to zero.

【0012】

In the second aspect, the photocatalyst is TiO.₂, ZnO, SnO₂, SrTiO₃, WO₃, Bi₂O₃, Fe₂O₃At least one metal oxide selected from.

【0013】

These metal oxides are preferable because they are easily available without any particular hindrance in their formation. Further, since the metal element and the oxygen element are present on the surface, chemical adsorption of hydroxyl groups is likely to occur, which is preferable. Especially titania (TiO₂) Is most preferable because it is harmless to the human body and chemically stable, and the crystal form may be either anatase or rutile. Anatase-type titania has the advantage that the sol can be easily obtained on the market by dispersing it as very fine particles, and the thickness of the sol can be reduced when it is fixed to the surface of the base material. Since rutile-type titania can be sintered at a high temperature, it can be sintered and formed on the surface of the base material, and can be fixed to the surface of the base material with high strength and wear resistance, which is preferable. In this case, each of the above metal oxides functions independently as a photocatalyst, but the characteristics of the catalytic function are superior or inferior among the metal oxides. For example, titania, ZnO, SrTiO₃Each metal oxide in the group of SnO₂, WO₃, Bi₂O₃, Fe₂O₃Since the catalytic function is superior to that of each metal oxide in the group of, when the metal oxide belonging to the former group is used as a photocatalyst, the metal oxide belonging to the latter group is a metal element and an oxygen element as described above. Is present on the surface and chemical adsorption of hydroxyl groups is likely to occur, so that it can be a compound contained together with a photocatalyst. Specifically, when titania is used as a photocatalyst, SnO₂May be a compound together with this photocatalyst.

【0014】

In the third aspect, the compound is a compound having a moist heat equal to or higher than that of the photocatalyst.

【0015】

Wet heat can be regarded as an index showing the retention characteristics of hydroxyl groups on the surface of a substance in which hydroxyl groups can be present on the surface. The higher the heat of wetness, the higher the degree of hydroxyl group retention and the higher the hydroxyl group density. Therefore, according to this third aspect, the hydroxyl groups generated by the photocatalyst can be chemically adsorbed and retained on the compound at a higher density and more effectively, and high hydrophilicity can be imparted to the surface of the base material more reliably and for a long period of time. Can be done. In this case, the wet heat of titania, which is particularly preferable as a photocatalyst, is 320 to 512x10 in the anatase type.^-3Jm^-2, Rutile type 293 ~ 645x10^-3Jm^-2Because it is 500x10^-3Jm^-2It is more preferable that the compound has the above wet heat.

【0016】

In the fourth aspect, the compound is SiO₂, Al₂O₃, ZrO₂, GeO₂, ThO₂, At least one metal oxide selected from ZnO.

【0017】

Since these metal oxides have a moist heat equal to or higher than that of titania, which is particularly preferable as a photocatalyst, the retention density of hydroxyl groups is further increased, which is preferable. In particular, silica (SiO)₂), Alumina (α-Al₂O₃), GeO₂, ThO₂Has an upper limit of 1000x10 in the range of wet heat^-3Jm^-2It is more preferable because it exceeds.

【0018】

Since ZnO is a photocatalyst and a metal oxide having a high moist heat, it goes without saying that when ZnO is selected as the photocatalyst, ZnO is not selected as the compound having a high moist heat.

【0019】

In a fifth aspect, the compound can be adjusted and contained in a particle size range of about 0.005 to about 0.1 μm.

【0020】

Hydroxyl radicals ( OH; this is a code to distinguish them from hydroxyl groups and indicate a lack of valence electrons) are constantly generated during light irradiation of the photocatalyst, but are generated. Since OH itself is a radical in nature, it reacts within a very short time and changes to a hydroxyl group or reacts with other substances. And, the spread of the system in which OH reacts is defined by the time when OH can exist as a radical, and this time is about 10^-6~ About 10^-8Since it is sec, it is about 0.05 μm in terms of diffusion distance. Therefore, if the compound is adjusted in a particle size range of about 0.1 μm or less, when the photocatalyst is in contact with or in close proximity to the compound particles on both sides, the photocatalyst is generated. OH reaction It will be included in the system of.

【0021】

That is, as schematically shown in FIG. 1, the compound (SiO)₂) Is adjusted in the particle size range of about 0.1 μm or less, the OH produced by the photocatalysts (TiO2) on both sides of this compound reaches the surface of the compound particles from both sides, and almost all the surfaces of the compound. OH will be chemically adsorbed as a hydroxyl group. Therefore, according to this fourth aspect, the hydroxyl groups generated by the photocatalyst can be chemically adsorbed and retained on the surface of the compound particles at a higher density more effectively, and highly hydrophilicity is imparted to the surface of the substrate more reliably and for a long period of time. can do. Further, when the particle size is about 0.005 μm or more, the particle size can be adjusted by a well-known method such as a ball mill or a sol-gel method, and a specific particle size adjustment process is not required, which is preferable. In this case, it is preferable that the photocatalyst is also adjusted in particle size within the above particle size range from the viewpoint of dispersion and mixing of particles. However, even when the particles of the compound exceed the above particle size range, if the photocatalyst particles are in contact with or close to a plurality of locations on the surface of one compound particle at intervals of 1 μm or less, the compound Since the plurality of locations on the particle surface are individually included in the reaction system, even compound particles exceeding the above particle size range are included in the reaction system, and there is no particular problem.

【0022】

In the sixth aspect, when the weight of the compound is expressed as a and the weight of the photocatalyst is expressed as b, the solid content ratio defined by a / (a + b) is about 0.01 to about 0.5. It is contained.

【0023】

As in this sixth aspect, when the solid content ratio a / (a + b) is about 0.01 or more, the number of compounds that chemically adsorb and retain hydroxyl groups is not too small, so that hydroxyl groups are retained at high density. Is surely caused, and this is preferable because high hydrophilicity can be imparted. Further, when the solid content ratio a / (a + b) is about 0.5 or less, the amount of the photocatalyst represented by b is not too small with respect to the above compound, and a sufficient amount of the photocatalyst is surely used. High water acidity can be imparted through the formation of hydroxyl groups, which is preferable.

【0024】

In the seventh aspect, the photocatalyst supports and fixes particles of a metal or a metal compound capable of exhibiting a property of enhancing the production of hydroxide radicals on the surface.

【0025】

According to this seventh aspect, since the generation of hydroxide radicals in the photocatalyst is enhanced by the particles of the metal or metal compound supported and fixed on the surface, the hydroxyl groups can be more reliably retained at a high density and high hydrophilicity can be exhibited. .. In this case, examples of such metals or metal compounds include metals such as Pt, Rh, Pd, Cu, Ag, and Zn and salts of these metals. Then, for the support on the surface of the photocatalyst, an appropriate method such as a dipping method, a photoprecipitation method, a mixing method, or a chemical precipitation method may be adopted.

【0026】

The eighth aspect is the hydrophilicity-imparting material obtained by mixing and dispersing the hydrophilicity-imparting material of the first invention or each aspect thereof in a paint or a glaze.

【0027】

In this eighth aspect, as described above, high hydrophilicity can be reliably maintained for a long period of time in the coating film on the surface of the one coated with this paint or in the glaze on the surface of the one coated with the glaze. ..

【0028】

In this case, the paint or glaze that is the target of mixing and dispersing the photocatalyst and the compound may be an existing one, and in the case of the glaze, the photocatalyst and the compound are contained in the solution together with the glaze raw material such as feldspar and frit such as potassium carbonate. It is dispersed. When the photocatalyst and the compound are dispersed and mixed, they may be blended together with the above-mentioned glaze raw materials in the process of producing the glaze, or may be blended into the completed glaze prior to the glaze.

【0029】

The hydrophilic exhibiting material of the second invention is a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of the base material, and as the surface layer, the hydrophilicity of the first invention or each aspect thereof. It is characterized by having a surface layer made of an imparting material.

【0030】

The hydrophilic exhibiting material of the third invention is a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of the base material, and the surface layer is the hydrophilicity of the first invention or each aspect thereof. The imparting material is a surface layer formed on the surface of the base material with a binder interposed therebetween.

【0031】

In the third invention, it is preferable that the binder is a binder made of a material whose softening temperature is lower than the softening temperature of the base material, or is a glaze.

【0032】

In the second and third inventions having the above structure, the surface layer itself made of the hydrophilicity-imparting material reliably maintains high hydrophilicity for a long period of time as described above. Therefore, according to the hydrophilic exhibiting materials of the second and third inventions having such a surface layer, it is possible to provide a new material capable of reliably and long-term exhibiting high hydrophilicity.

【0033】

The hydrophilic demonstrating material of the fourth invention is a hydrophilic demonstrating material having a surface layer exhibiting hydrophilicity on the surface of the base material, and the surface layer causes excited electrons and holes by the energy of the irradiated light. It is a surface layer formed by containing a photocatalyst that is generated and functions as a catalyst, and generates a hydroxyl group through the generation of water or water and an acid radical on the surface of the catalyst in the presence of oxygen, and is the surface of the surface of the surface layer. It is characterized in that the roughness is about 0.15 μm or more and about 1 μm or less in terms of centerline average roughness (Ra).

【0034】

In the hydrophilic exhibiting material of the fourth invention, the photocatalyst forming the surface layer constantly generates hydroxyl groups during irradiation with light, and the surface of the surface layer has high hydroxyl groups. Retained at density. Therefore, while the hydrophilic exhibiting material is placed under light irradiation, high hydrophilicity can be reliably exerted due to the presence of hydroxyl groups at a high density. However, when the amount of sunshine is small or cloudy weather continues for a long period of time due to regional characteristics, for example, in the winter season in high latitude areas, the generation of hydroxyl groups by the photocatalyst becomes low, so the retention density of hydroxyl groups decreases and it becomes hydrophilic. The sex is reduced.

【0035】

In the hydrophilic exhibiting material of the fourth invention, in addition to exhibiting hydrophilicity in the surface layer with a photocatalyst as described above, the surface roughness of the surface layer surface is about 0.15 in terms of center line average roughness (Ra). It is set to about 1 μm or less at μm or more. The surface roughness affects the contact angle of water on the surface, and it is said that there is the following relationship between the two.

【0036】

cosθ = νxcosθ' Here, θ'is the contact angle (constant) when the surface is smooth. ν is an apparent area ratio to the area when a surface with surface roughness is converted into a smooth surface, and its value increases as the surface roughness increases.

【0037】

Therefore, when the surface roughness becomes rough, ν increases and the contact angle θ decreases. Therefore, it was decided to adjust the contact angle θ and the hydrophilicity by the surface roughness which is a physical factor of the surface layer surface. In the hydrophilic exhibiting material of the fourth invention, by setting the surface roughness in the above range, water droplets existing in the surface layer can be easily spread due to a physical factor of surface roughness. Therefore, in the hydrophilic exhibiting material of the fourth invention, the hydrophilicity exhibited by the photocatalyst through the formation of the hydroxyl group described above is complemented by the synergistic effect of the physical contact angle reducing effect through the adjustment of the surface roughness. Therefore, high hydrophilicity can be obtained. In other words, under light irradiation, the high hydrophilicity based on the continuous generation of hydroxyl groups by the photocatalyst and the physical contact angle reduction effect based on the surface roughness combine to exhibit high hydrophilicity more quickly. Can be maintained. Further, even if the hydroxyl group generation by the photocatalyst becomes low and the hydrophilicity caused by the photocatalyst decreases, the decrease in hydrophilicity on the surface of the surface layer is suppressed by the physical contact angle reducing effect based on the surface roughness, and the hydrophilicity is somewhat high. Can maintain hydrophilicity as it is. Therefore, the hydrophilic exhibiting material of the fourth invention can also provide a new material capable of reliably exhibiting high hydrophilicity for a long period of time.

【0038】

The hydrophilic exhibiting material of the fifth invention is a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of the base material, and as the surface layer, the hydrophilicity of the first invention or each aspect thereof. It has a surface layer made of an imparting material, and the surface roughness of the surface of the surface layer is about 0.15 μm or more and about 1 μm or less in terms of center line average roughness (Ra).

【0039】

In the hydrophilic exhibiting material of the fifth invention, the surface layer itself made of the hydrophilic imparting material reliably maintains high hydrophilicity for a long period of time as described above, and further, the physical contact angle based on the surface roughness. The reduction effect can be synergistically achieved. Therefore, according to the hydrophilic exhibiting material of the fifth invention having such a surface layer, it is possible to provide a new material capable of reliably exhibiting high hydrophilicity for a long period of time.

【0040】

In the above-mentioned second to fifth inventions, the following aspects can be adopted. In the first aspect, the substrate is any of ceramic, resin, metal, glass, pottery or wood. Therefore, if the hydrophilic exhibiting material of this aspect is used for the wall material of the inner and outer walls of a building or the steel plate of the vehicle body of an automobile, a train, etc., it has a high hydrophilicity exhibited in the surface layer and a high stain prevention effect. Can be played. Further, when it is used for window glass of buildings, houses, vehicles, etc., it is possible to exert a high anti-fog effect in addition to a high anti-staining effect, and it is preferable that window cleaning or the like is unnecessary or the frequency of cleaning is reduced.

【0041】

In the second aspect, the surface layer is formed by firing. According to this aspect, the surface layer can be firmly formed on the base material.

【0042】

The method for producing a hydrophilic exhibiting material of the sixth invention is a method for producing a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of a base material, and is the method for producing a hydrophilic exhibiting material according to the first invention or each aspect thereof. The step of preparing the hydrophilic imparting material sol in which the imparting material or the hydrophilic imparting material is dispersed to form a sol, and the hydrophilic imparting material or the hydrophilic imparting material sol are arranged in layers on the surface of the base material. It is characterized by having a step of forming the surface layer from the layered arrangement of the hydrophilicity-imparting material or the hydrophilicity-imparting material sol.

【0043】

In this case, the hydrophilicity-imparting material sol can be obtained by dispersing the hydrophilicity-imparting material in a solution such as water or alcohol.

【0044】

According to the production method of the sixth invention, since no special step is required, it is possible to easily produce a novel hydrophilic exhibiting material capable of reliably exhibiting high hydrophilicity for a long period of time. At this time, in forming the surface layer, an appropriate method, for example, heat treatment or drying treatment can be adopted depending on the arranged hydrophilicity-imparting material or hydrophilicity-imparting material sol.

【0045】

In the sixth invention, in the arrangement step, when the hydrophilicity-imparting material or the hydrophilicity-imparting material sol is arranged in a layer on the surface of the base material, the hydrophilicity-imparting material or the hydrophilicity-imparting material is arranged. A method for producing a hydrophilic exhibiting material having a step of placing, coating or printing the sol on the surface of the base material in a layered manner has the following advantages.

【0046】

According to the sixth invention, it is possible to easily produce a novel hydrophilic exhibiting material which is made of a hydrophilic imparting material and can exhibit high hydrophilicity reliably and for a long period of time in a surface layer having a substantially uniform thickness. .. The layered coating of the hydrophilicity-imparting material on the surface of the base material can be carried out by an appropriate coating method such as spray coating, and the layered printing can be carried out by an appropriate printing method such as roll printing.

【0047】

The method for producing a hydrophilic exhibiting material according to the seventh invention is a method for producing a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of the base material, and is the above-mentioned first invention or the hydrophilicity of each aspect thereof. A step of preparing a hydrophilicity-imparting material or a hydrophilicity-imparting material sol in which the hydrophilicity-imparting material is dispersed to form a sol, and a step of arranging a binder in a layer on the surface of the base material to form a binder layer. The arrangement step of arranging the hydrophilicity-imparting material or the hydrophilicity-imparting material sol in a layer on the surface of the binder layer, and the temperature higher than the softening temperature of the binder in the range of 30 ° C. or more and 300 ° C. or less, and the above. It is characterized by having a step of forming the surface layer from the layered excrement of the hydrophilic imparting material or the hydrophilic imparting material sol by heat treatment in a temperature environment lower than the softening temperature of the base material.

【0048】

According to the seventh invention, at the boundary between the binder layer and the surface layer, the hydrophilicity-imparting material in the surface layer, specifically, the photocatalyst and the compound are held in a state of being buried in the binder layer, and the surface layer is held in the binder layer. It can be formed on the layer surface. Therefore, the surface layer can be firmly fixed to the binder layer, and the photocatalyst of the hydrophilic imparting material and the compound can be effectively brought into contact with the outside air. Therefore, it is possible to produce a novel hydrophilic exhibiting material capable of reliably exhibiting high hydrophilicity in the surface layer for a long period of time. In this case, since the heating temperature is set to be 30 ° C. or more higher than the softening temperature of the binder, it is preferable that the softening of the binder by heating does not inadvertently require a long period of time. In addition, since the heating temperature is not higher than the softening temperature of the binder by more than 300 ° C, rapid melting of the binder is avoided, and the photocatalyst and compound of the hydrophilic imparting material are excessively filled, uneven surfaces are generated, or pinholes are generated. It is possible to suppress problems such as the occurrence of.

【0049】

In the sixth and seventh inventions described above, it is preferable that the step of forming the surface layer includes a step of heat treatment in a temperature environment of about 150 to about 1300 ° C. In this way, it is possible to produce a novel hydrophilic exhibiting material capable of reliably and for a long period of time exhibiting high hydrophilicity in the surface layer by using the existing heating device. In this case, if the heat treatment temperature is set to about 150 ° C. or higher, it matches the heat treatment temperature of the existing glaze or paint (inorganic paint), and it is not necessary to change the heat treatment conditions from the conventional one. Further, if the heat treatment temperature is set to about 1300 ° C or less, the heat treatment temperature is matched with the heat treatment temperature at the time of production of the base material requiring heat treatment, for example, tiles and ceramics, and the heat treatment conditions do not need to be changed from the conventional ones.

【0050】

The method for producing a hydrophilic exhibiting material according to the eighth invention is a method for producing a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of a base material, and excite electrons and holes due to the energy of irradiated light. To prepare particles of a photocatalyst that functions as a catalyst and generate hydroxyl groups through the generation of hydroxide radicals in the presence of water or moisture and oxygen on the surface of the catalyst, and prepare a suspension in which the photocatalyst particles are dispersed. The step of preparation, heating of the surface of the base material, and spray coating of the suspension on the surface of the base material are performed while adjusting the temperature and the amount of coating to adjust the surface layer composed of the photocatalytic particles. It is characterized by having a step of forming the surface roughness so that the average roughness (Ra) of the center line is about 0.15 μm or more and about 1 μm or less.

【0051】

The method for producing a hydrophilic exhibiting material according to the ninth invention is a method for producing a hydrophilic exhibiting material having a surface layer exhibiting hydrophilicity on the surface of the base material, and is the above-mentioned first invention or the hydrophilicity of each aspect thereof. The step of preparing a suspension in which the sex-imparting material is dispersed in particles, heating of the surface of the base material and spray application of the suspension to the surface of the base material are performed, and temperature adjustment and application amount adjustment are performed. It is necessary to have a step of forming the surface layer composed of the hydrophilic imparting material particles so that the surface roughness is about 0.15 μm or more and about 1 μm or less in the center line average roughness (Ra). A characteristic method for producing a hydrophilic exhibiting material.

【0052】

According to the method for producing a hydrophilic exhibiting material of the eighth and ninth inventions, the surface layer surely exhibits and maintains high hydrophilicity as described above, and further, physical based on the surface roughness. It is possible to produce a novel hydrophilic exhibiting material capable of layering the effect of reducing the contact angle. If the surface layer is fired in the production method of the present invention, the surface layer can be firmly fixed and formed on the surface of the base material, which is more preferable.

【0053】

[Other Aspects of the Invention]

The present invention can also take other aspects such as the following, and the first other aspect is a method for producing a hydrophilic imparting material that imparts hydrophilicity to the surface of a base material, and is irradiated. The first, in which particles of the photocatalyst that generate excitation electrons and holes by the energy of light and function as a catalyst and generate hydroxyl groups through the generation of water or water and hydroacid radicals in the presence of oxygen on the surface of the catalyst are dispersed. The step (A) of preparing the sol, the step (B) of preparing the second sol in which the particles of the compound having the property of chemically adsorbing the hydroxyl group are dispersed, and the first sol and the second sol. It is characterized by including a step (C) of mixing.

【0054】

According to the production method of another aspect, the photocatalyst and the compound can be easily dispersed in the solvent by mixing the first and second sol. The mixed sol that has undergone step (C) is a sol in which only the photocatalyst and the compound are almost uniformly mixed and dispersed without the photocatalyst alone or the compound being aggregated and present. It becomes. Therefore, this mixed sol is suitable for use as a hydrophilicity-imparting material sol, and facilitates compounding of a photocatalyst and a compound into a material used in a liquid state, for example, a paint or a glaze. Further, since the first and second sol are easily weighed because of the sol shape, the mixing ratio of the photocatalyst and the compound can be easily adjusted through the weighing of each sol. Further, if the solvent in the mixed sol is removed by a method such as drying, a solid and granular hydrophilicity imparting material in which the photocatalyst and the compound are mixed substantially uniformly can be obtained.

【0055】

In this case, it is preferable to use the same solvent for the first sol and the second sol, or to use a so-called familiar solvent.

【0056】

In the production method of the other aspect described above, the step (B) may include a step of adjusting the particles of the compound so as to have a particle size range of about 0.005 to about 0.1 μm.

【0057】

According to this aspect, the compound particles can be included in the reaction system of OH produced by the photocatalyst, and OH reaches almost all the surfaces of the compound particles and is chemically adsorbed as a hydroxyl group on the surface. Will be. Therefore, according to this aspect, the hydroxyl group generated by the photocatalyst can be chemically adsorbed and retained on the surface of the compound particles at a higher density more effectively, and high hydrophilicity can be imparted to the surface of the base material more reliably and for a long period of time. It is possible to easily produce a novel hydrophilicity-imparting material that can be produced. Further, when the particle size is about 0.005 μm or more, the particle size can be adjusted by a well-known method such as a ball mill or a sol-gel method, and a specific particle size adjustment process is not required, which is preferable.

【0058】

Further, in the production method of the other aspect described above, the step (A) can include a step of adjusting the particles of the photocatalyst in a particle size range of about 0.005 to about 0.1 μm.

【0059】

According to this aspect, it is possible to easily obtain a hydrophilic imparting material in which a photocatalyst that generates a hydroxyl group and a compound that retains a hydroxyl group are mixed substantially uniformly.

【0060】

Further, in each of the above-mentioned production methods of the other aspects, the step (C) is defined by a / (a + b) when the weight of the compound is expressed as a and the weight of the photocatalyst is expressed as b. It is possible to have a step of blending the first sol and the second sol so that the solid content ratio is about 0.01 to about 0.5.

【0061】

According to this aspect, the amount of the compound for retaining the hydroxyl group is not too small, and the amount of the photocatalyst is not too small with respect to the above compound, so that high hydrophilicity is surely and long-term. It is possible to easily obtain a hydrophilic imparting material that can be imparted over.

【0062】

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described based on examples.

【0063】

First, the formulation of the hydrophilicity-imparting material used in the examples will be described. Anatase-type titania is used as the photocatalyst, and silica (SiO) is used as the metal oxide to be blended with this photocatalyst.₂), Alumina (Al₂O₃), SnO₂And ZrO₂Was used. Then, the following steps were taken when preparing the hydrophilicity-imparting material.

【0064】

Photocatalyst and metal oxide sol procurement Prepare a titania sol with a known weight ratio of titania. The prepared titania sol has three types of average particle size of about 0.02 μm, about 0.01 μm, and about 0.007 μm. For metal oxides such as silica, the following sol (metal oxide sol) having a known weight ratio was prepared.

【0065】

Silica: Two types of sol with an average particle size of about 0.01 to about 0.02 μm and about 0.007 to about 0.009 μm. Alumina: A sol with an average particle size of about 0.01 to about 0.02 μm. SnO₂: A sol with an average particle size of about 0.002 μm. ZrO₂: A sol with an average particle size of about 0.07 μm.

【0066】

Adjustment of hydrophilicity imparting material After that, the above metal oxide sol is mixed and stirred with the above various titanium sol (photocatalytic sol), and the titanium mixed sol (Ti / Si sol, Ti / Al sol, Ti / Sn sol and Ti / Zr sol) is mixed. obtain. In this case, in adjusting each of the above titania mixed sol, when the weight of the metal oxide in each mixed sol is expressed as a and the weight of the photocatalyst (titania) is expressed as b, it is defined by a / (a + b). The mixed amount of titania sol and metal oxide sol was weighed so that the solid content ratio was 0.2.

【0067】

In addition to the above-mentioned steps, particles of the above-mentioned metal oxides such as silica and alumina whose particle size has been adjusted can be added and dispersed in the procured titania to obtain a Ti / Si sol or the like. Further, it is also possible to alternately or simultaneously disperse the titania particles whose particle size has been adjusted and the metal oxide particles such as silica and alumina in the solvent to obtain a sol in which the titania particles and the metal oxide particles are dispersed from the beginning. Needless to say, each of the above sol may be a commercially available product.

【0068】

Next, the hydrophilicity imparted by using the hydrophilicity imparting material (Ti / Si sol, Ti / Al sol, Ti / Sn sol and Ti / Zr sol titania mixed sol) adjusted as described above. The sol will be described. In this example, this hydrophilic exhibiting material was used as a tile and manufactured as follows.

【0069】

A glazed tile is prepared as a base material, and each of the above titania mixed sol having a specified concentration is spray-coated on the tile surface so that the film thickness is about 0.5 μm. Next, the tiles after spray coating of the titania mixed sol were fired for about 60 minutes at a temperature considering the melting temperature of the photocatalyst titania and each metal oxide (about 850 ° C in this example). The final hydrophilic exhibiting material (hydrophilic exhibiting tile) having a surface layer on the surface of the base material was used. This surface layer is a surface layer composed of titania and metal oxides such as silica and alumina. RHK (Roller Hers Kiln) was used for firing.

【0070】

It was decided to evaluate the hydrophilic tiles produced in this way based on the contact angle with water. The outline of the test is as follows.

【0071】

First, in order to compare with the example product of the present invention, a tile that has just been glazed (with an untreated tile), a comparative example tile having a surface layer consisting only of titania sol, and a hydrophilic demonstrating tile of the example (implementation). Example tile) was prepared as follows. The spray coating amount of titania sol in the comparative example tile is set so that the film thickness is about 0.5 μm as in the example tile. The firing conditions are also the same as those of the example tiles. That is, since the comparative example tile has only titania in the surface layer of the tile surface and exhibits the hydrophilicity as a reference on the comparative control, by comparing this comparative example tile with each of the above-mentioned example tiles, The presence or absence and the degree of improvement in hydrophilicity obtained by blending each metal oxide will be clarified.

【0072】

The above untreated tiles, comparative example tiles and each example tile were tested as follows. For the test, a sample piece of an appropriate size was used for each tile, and the contact angle of the water droplets dropped on the sample piece was determined immediately after the tile was manufactured and by a lamp that irradiates ultraviolet rays (light reception of the sample piece at a wavelength of 320 to 380 nm). The amount is about 1mW / cm²) Was irradiated with ultraviolet rays for about 24 hours, and after being left in a dark place for about 48 hours after the irradiation with ultraviolet rays, the measurements were taken. The results are shown in Table 1.

【0073】

[table 1]

<img file="JPH10237416A_D0001.tif" />【0074】

As is clear from Table 1, the contact angle of the untreated tiles hardly changed and the hydrophilicity of the surface did not change, whereas the contact angles of the comparative example tiles and the example tiles decreased by ultraviolet irradiation. However, the hydrophilicity of the surface was improved through the formation of hydroxyl groups by titania subjected to ultraviolet irradiation. Moreover, the contact angle at this time is halved in the comparative example tile regardless of the size of the flow diameter of titania, and in the example tile, regardless of which metal oxide is mixed in the example tile. The contact angle was reduced more than that of the comparative example tile, and higher hydrophilicity could be exhibited than that of the comparative example tile. In particular, Example tile 1 mixed with silica having an average flow diameter of about 0.007 to about 0.009 μm and SnO.₂, ZrO₂In Example tiles 3, 4, and 6 mixed with alumina, the contact angle was significantly reduced as compared with Comparative Example tiles, and significantly higher hydrophilicity could be exhibited as compared with Comparative Example tiles.

【0075】

Further, in the comparative example tile, the contact angle almost returns to the initial value immediately after manufacturing when placed in a dark place, whereas in the example tile, the contact angle is lower than the initial value of each tile. I only returned to. From this, it can be said that the tiles of each example can maintain high hydrophilicity even in a dark place due to the mixed metal oxides. In particular, in Example tiles 1 to 4, a contact angle slightly exceeding the contact angle exhibited by the comparative example tiles under light irradiation can be obtained even in a dark place, and high hydrophilicity can be maintained even in a dark place. It was. Then, in the example tile 6 in which alumina is mixed, a contact angle almost the same as the contact angle under light irradiation can be obtained even in a dark place, and the hydrophilicity enhanced by light irradiation can be obtained almost as it is even in a dark place. I was able to maintain it.

【0076】

In addition, the surface condition of each example tile was excellent with no abnormality observed in the degree of unevenness. Moreover, when a sliding wear test using a plastic eraser was attempted in accordance with JIS-A6808, the surface layer of each example tile showed no deterioration or peeling even after about 40 reciprocating slides, and was resistant to peeling. It was also found to have excellent wear resistance. This means that the hydrophilicity-imparting material produced by the above-mentioned method of mixing sol can be applied not only to firing paints and glazes, but also to firing, printing, binders and the like. In addition, as described above, a new hydrophilicity-imparting material that can reliably impart high hydrophilicity and a new hydrophilicity-demonstrating material that can reliably maintain high hydrophilicity for a long period of time are mixed with the above-mentioned sol. It can be said that it can be easily manufactured.

【0077】

Next, the relationship between the degree of mixing (blending) of the mixed metal oxide and the hydrophilicity was evaluated by taking silica as an example of the metal oxide.

【0078】

The prepared tiles are as follows. (1) Example tile Titania sol (average particle size of titania particles: about 0.02 μm) and colloidal silica (average particle size of silica particles: about 0.007 to about 0.009 μm), whose weight ratio of titania is known, are prepared, and the weight of titania is increased. Prepare mixed suspensions that are the same but have different solid content ratios defined by a / (a + b) when the weight of silica is expressed as a and the weight of titania is expressed as b. This suspension serves as the hydrophilic imparting material in this example. Then, each of these suspensions is applied to the surface of the non-glazing tile as the base material so that the film thickness is about 0.5 μm, and fired at about 850 ° C for about 60 minutes at RHK to form the base. An example tile (hydrophilic tile) having a surface layer on the surface of the material was used. The solid content ratio was set to a value in the range of 0.01 to 0.6. (2) Comparative example tile It is a tile having a surface layer composed only of titania sol containing titania having the above particle size, and the firing conditions and the like are the same as those of the example tile. In this comparative example tile, the solid content ratio of silica is zero. (3) Unprocessed tile It is a non-glazing tile.

【0079】

For these tiles, the contact angle with water was set to the contact angle with water immediately after the tile was manufactured, and the lamp that irradiates ultraviolet rays (at a wavelength of 320 to 380 nm, the amount of light received by the sample piece was about 1 mW / cm).²) Was irradiated with ultraviolet rays for about 24 hours, and after being left in a dark place for about 48 hours after the irradiation with ultraviolet rays, the measurements were taken. Even in this evaluation test, the comparative example tile exhibits the standard hydrophilicity. Therefore, by comparing this comparative example tile with each example tile having a different silica compounding amount, a quantitative photocatalyst is blended. The effect of the amount of silica compounded on the improvement of hydrophilicity is clarified. The results are shown in Table 2.

【0080】

[Table 2]

<img file="JPH10237416A_D0002.tif" />【0081】

As is clear from Table 2, the reason why the contact angle was reduced more than that of the comparative example tiles, that is, the hydrophilicity was improved under light irradiation and in a dark place, was that the silica compounding amount was 0.01 to 0.5 in terms of solid content ratio. In the example tiles in the range of, when the solid content ratio was 0.6, the contact angle was reduced only to the same extent as in the comparative example. That is, when the silica compounding amount is in the range of 0.01 to 0.5 in terms of solid content ratio, high hydrophilicity can be exhibited regardless of whether it is under light irradiation or in a dark place. In this case, if the solid content ratio is 0.01 or more, the amount of silica that chemically adsorbs and retains the hydroxyl group is not too small, so that the hydroxyl group can be reliably retained on the surface at a high density, thereby ensuring high hydrophilicity. Can be demonstrated. Further, when the solid content ratio is 0.5 or less, the amount of titania is not too small with respect to silica, and high hydrophilicity is imparted through reliable formation of hydroxyl groups with a sufficient amount of photocatalyst (titania). be able to. When the solid content ratio is 0.1 to 0.3, the contact angle is significantly reduced, that is, the hydrophilicity is improved as compared with the comparative example tile, which is more preferable.

【0082】

Next, the relationship between the surface roughness of the surface layer and the hydrophilicity will be described. First, a method for adjusting the surface roughness will be described. Prepare titania sol (average particle size of titania particles: about 0.02 μm, fixed component concentration 1.0 wt%) and spray coat on the surface of glazed tiles (base materials) with different surface temperatures so that the film thickness is about 0.5 μm. To do. Next, it was fired at RHK at about 840 ° C for about 60 minutes to obtain an example tile (hydrophilic demonstrating tile) having a surface layer on the surface of the base material. Then, the surface temperature of the tile at the time of spray application was measured with a radiation thermometer, and the surface roughness of the tile surface after firing was measured as the center line average roughness (Ra) with a shape measuring instrument. The results are shown in Fig. 2.

【0083】

From Fig. 2, if the tile surface is controlled to 60 to 120 ° C, the surface roughness of the surface layer of the tile surface can be set to about 0.15 to 0.25 μm in terms of center line average roughness (Ra). .. In this case, the surface roughness of the glazed tile itself, which is the base material, was about 0.08 μm in terms of the center line average roughness (Ra), so it can be said that the surface roughness of the surface layer can be adjusted by controlling the temperature of the tile surface. .. The surface roughness can be controlled by controlling the tile surface temperature for the following reasons.

【0084】

When the spray-coated titania sol spray particles reach the heated tile surface, they receive heat from the tile and vaporize, and the fixed amount (in this case, titania) contained in the spray particles remains on the tile surface. At this time, since the spray particles are vaporized more rapidly as the tile surface temperature is higher, the spray particles are vaporized on the tile surface before the spray particles spread, and the fixed components are relatively aggregated and remain. Therefore, the higher the tile surface temperature, the rougher the surface roughness.

【0085】

In addition, prepare titania sol (average particle size of titania particles: about 0.02 μm, fixed fraction ratio of titania is constant), and film thickness on the surface of glazed tile (base material) with constant surface temperature (about 90 ° C). Apply so that the size is about 0.125 to 1 μm. Next, the tiles were fired at RHK at about 840 ° C. for about 60 minutes to obtain example tiles (hydrophilic tiles) having different film thicknesses on the surface layer of the base material surface. In this case, since the amount (weight) of titania in the surface layer is different depending on the film thickness, it can be said that this example tile is also a tile having a different titania weight in the surface layer. Then, the relationship between the surface roughness (center line average roughness (Ra)) and the film thickness (average film thickness) of the tile surface after firing was investigated. The results are shown in Fig. 3.

【0086】

From FIG. 3, if the average film thickness is about 0.5 μm or more, the surface roughness of the surface layer of the tile surface can be about 0.22 to 0.25 μm in terms of the center line average roughness (Ra). In this case as well, the surface roughness of the glazed tile itself, which is the base material, was 0.08 μm in terms of the center line average roughness (Ra), so it can be said that the surface roughness of the surface layer can be adjusted through the adjustment of the film thickness.

【0087】

Next, the tiles whose surface roughness of the surface layer was adjusted by controlling the tile surface temperature were evaluated as follows. The evaluation included untreated tiles (center line average roughness (Ra): about 0.08 μm) that had a glazed surface but did not have a surface layer containing titania, which is a photocatalyst, and the surface roughness of the tile surface. Tiles with center line average roughness (Ra) of 0.10 μm, 0.16 μm, and 0.21 μm were used. In addition, in the test for evaluation, a sample piece of an appropriate size was used for each of these tiles, and the contact angle of the water droplets dropped on the sample piece was measured by a lamp that irradiates ultraviolet rays (sample at a wavelength of 320 to 380 nm). The amount of light received by one piece is about 1 mW / cm²The measurements were taken at the time when the ultraviolet irradiation in) was about 8 hours, the time when the ultraviolet irradiation was about 24 hours, and the time when it was left in a dark place for another 48 hours. The results are shown in Table 3.

【0088】

[Table 3]

<img file="JPH10237416A_D0003.tif" />【0089】

As is clear from Table 3, in the untreated tiles, the contact angle hardly changed and the surface hydrophilicity did not change, whereas in the tiles having a surface layer formed from titania sol, all the tiles had no change. In the light irradiation environment, the contact angle decreased, and the hydrophilicity of the surface was improved through the formation of hydroxyl groups by the titania irradiated with ultraviolet rays. Moreover, the contact angle at this time decreases as the surface roughness becomes coarser, and the contact angle of the tiles having a surface roughness of 0.16 μm and 0.21 μm is greatly reduced as compared with the tile having a surface roughness of 0.10 μm. Remarkably high hydrophilicity could be exhibited.

【0090】

In addition, in the tiles with each surface roughness, the contact angle increases because the generation of hydroxyl groups due to ultraviolet irradiation is stopped in any tile, but the tiles with surface roughness of 0.16 μm and 0.21 μm are present. The degree of increase in contact angle was smaller than that of tiles with a surface roughness of 0.10 μm, and the hydrophilicity did not decrease significantly. In particular, for a tile with a surface roughness of 0.21 μm, the contact angle in a dark place is smaller than the contact angle when a tile with a surface roughness of 0.10 μm is irradiated with ultraviolet rays for 24 hours. It increased only to the contact angle and remained highly hydrophilic. From these facts, if the surface roughness of the surface layer formed from titania sol is 0.16 μm or more in terms of center line average roughness (Ra), even if the surface layer contains only titania as a photocatalyst, it will have high hydrophilicity. It can be said that it can be maintained in the dark.

【0091】

Next, the relationship between the surface roughness of the surface layer and the hydrophilicity was evaluated by another method. The evaluation at this time was made by a stain test on the tile surface. In the test, as in the case of the above evaluation, the untreated tile (center line average roughness (Ra): about 0.08 μm) and the surface roughness of the tile surface are center line average roughness (Ra) of 0.10 μm. , 0.16 μm, 0.21 μm tiles were used. In addition, the stain test for evaluation is based on the Building Material Testing Center Standard (JSTM). It was carried out in accordance with the flow-down pollution promotion test method specified in J7602T-1992). In this case, prior to the test, each tile was irradiated with a lamp that irradiates ultraviolet rays (the amount of light received by the sample piece is about 1 mW / cm2 at a wavelength of 320 to 380 nm) for about 24 hours, and then for 48 hours. Stored in the dark for 48 hours. That is, the above test was carried out in a dark place after irradiation with ultraviolet rays and storage in a dark place. Then, the color value at the time when the flow-down pollution promotion test was repeated for 10 cycles was measured, and the evaluation was made by the comparison value (ΔE *) with the color value before the start of the test. As for the color value, the surface region where the pollution is severe and the surface region where the pollution is not advanced are visually selected, and the surface region of each tile is measured at 5 points each, and the comparison value obtained for each surface region ( The average value of ΔE *) was used as the measured value. The results are shown in Table 4.

【0092】

[Table 4]

<img file="JPH10237416A_D0004.tif" />【0093】

As is clear from Table 4, for untreated tiles, the maximum comparison value ( E *) obtained in the heavily polluted surface area and the minimum comparison value ( E *) obtained in the less polluted surface area. While there is a difference of 15.2 from E *), the difference in comparison value ( E *) is smaller for tiles with a surface layer formed from titania sol than for untreated tiles, and the stain prevention effect is improved. I was able to get it. It should be noted that this effect was obtained because the hydrophilicity of the surface was improved through the formation of hydroxyl groups by titania subjected to ultraviolet irradiation. Moreover, the difference in this comparison value (ΔE *) decreases as the surface roughness becomes coarser, and the tiles with surface roughness of 0.16 μm and 0.21 μm are larger than the tiles with surface roughness of 0.10 μm. It was reduced, and it was possible to obtain a higher antifouling effect with remarkable high hydrophilicity. Moreover, such an antifouling effect could be clearly confirmed visually. In particular, for tiles with a surface roughness of 0.21 μm, the difference in comparison values ( E *) is only 0.6, and numerically, the properties are almost the same before and after the test against stains. It can be said that there is. From these facts, if the surface roughness of the surface layer formed from titania sol is 0.16 or more in center line average roughness (Ra), even if the surface layer contains only titania as a photocatalyst, it is high through high hydrophilicity. It can be said that the stain prevention effect and the streak stain prevention effect can be exhibited.

【0094】

Next, the relationship between the surface roughness of the surface layer and the hydrophilicity was evaluated from another viewpoint. The tiles and test methods used for the evaluation test at this time are as follows.

【0095】

The prepared tiles are as follows. (1) Example tile This example tile is a tile having a surface layer formed by blending titania with silica. This surface layer is made by adding colloidal silica (average flow diameter of silica particles: about 0.007 to about 0.009 μm) to titania sol (average flow diameter of titania particles: about 0.02 μm) with a known weight ratio of titania. It is formed (calcined) from the mixed suspension blended so that the ratio is 0.2 under the above-mentioned conditions (thickness: about 0.5 μm, firing temperature: about 830 ° x 60 minutes). Then, the surface roughness in the surface layer is adjusted through the control of the tile surface temperature. (2) Comparative example tile The comparative example tile is a tile having a surface layer formed from silica, and the surface layer is obtained by applying colloidal silica (average flow diameter of silica particles: about 0.007 to about 0.009 μm) to the surface of the glazed tile. It is formed (baked) under the conditions described above (thickness: about 0.5 μm, firing temperature: about 830 ° x 60 minutes). And even in this surface layer, the surface roughness is adjusted through the control of the tile surface temperature as in the above-mentioned embodiment tile. (3) Unprocessed tile A glazed tile that does not have a surface layer containing a photocatalyst and has a different surface roughness on the tile surface (glaze surface).

【0096】

The test method is as follows. In the test, 5 wt% corbon black, 67.5 wt% yellow ocher, 22.5 wt% calcined Kanto loam and 1 wt% silica powder were suspended as contaminants, and this contaminant was suspended at a rate of 1 g / liter. A liquid was used. The suspension was continuously added dropwise to the surface of each of the above tile sample pieces tilted at about 20 degrees from a height of about 20 cm at intervals of 1 drop / sec for 5 hours. Then, the color value after dropping for 5 hours was measured, and the degree of stain was evaluated by the comparison value (ΔE *) with the color value before the start of dropping (before the start of the test). The results are shown in Fig. 4. According to this test, the dropped suspension constantly flows down the tile surface, so the degree of adhesion of the above pollutants to the tile surface (surface layer surface), the presence or absence of detergency with water, and the degree of cleaning are determined. Can be evaluated. For the example tiles, the comparison value (ΔE *) was obtained for the same example tile when it was irradiated with ultraviolet rays for about 8 hours by the above lamp and when it was stored in a dark place for about 48 hours. It was.

【0097】

As shown in FIG. 4, in the untreated tile and the comparison tile, the comparison value (ΔE *) of the color value was about 4 or more, and the stain prevention effect could not be obtained. On the other hand, in each of the example tiles that exhibit and maintain high hydrophilicity by UV irradiation as described above, the color value comparison value (ΔE *) is almost equal to zero regardless of the surface roughness, and a high stain prevention effect. I was able to get. When the tiles of this example are not exposed to ultraviolet irradiation for a period of about 48 hours, the hydrophilicity decreases as explained in Tables 2 and 3, so the comparative value ( E *) increases and becomes dirty. The preventive effect is reduced. However, in the example tiles whose surface roughness is 0.15 μm or more in center line average roughness (Ra), even when placed in a dark place, the surface roughness of the untreated tile is 0.15 μm or more. The comparison value (ΔE *) can be made smaller than that of the example tile, and an excellent stain prevention effect can be obtained as compared with the untreated tile and the comparative example tile. From these facts, it can be considered as follows.

【0098】

In the comparative example tile, although the surface roughness of the surface layer is 0.15 μm or more, since this surface layer is made of silica, it does not exhibit high hydrophilicity through the formation of hydroxyl groups, and it is made of silica. Only low hydrophilicity based on the originally retained hydroxyl group can be exhibited. Then, as described above, in this comparative example tile, the comparative value (ΔE *) of the color value was large, and it was not possible to obtain the stain prevention effect. On the other hand, in the example tile, when the hydrophilicity is once increased by ultraviolet irradiation and the high hydrophilicity is maintained to some extent, specifically, when the tile is placed in a dark place after light irradiation. In addition, if the surface roughness of the surface layer was 0.15 μm or more, a higher stain prevention effect than that of the comparative example tile could be obtained. Therefore, the effect of reducing the contact angle through the adjustment of the surface roughness is not sufficiently exhibited when the hydrophilicity of the surface is low, and is obtained in combination with the high hydrophilicity of the surface. Conceivable. Then, as shown in FIG. 4, according to the example tile having a surface roughness of 0.2 μm or more, the effect of reducing the contact angle through the adjustment of the surface roughness and the high hydrophilicity of the surface are synergistic. It is considered that the comparison value (ΔE *) of the color value could be set to 1 or less even when the color value was placed in a dark place, and a high antifouling effect in a dark place could be obtained.

【0099】

Next, further examples will be described. In other examples, the procedure for forming a surface layer made of a hydrophilic imparting material having a photocatalyst such as titania and a specific metal oxide such as silica on the tile surface is different. In another embodiment, first, a base material for forming a surface layer is prepared. The equipment may be ceramic, resin, metal, glass, pottery, wood, etc., and if it is a base material used for building structures such as buildings, houses, bridges, road sound insulation walls, etc., the surface of these building structures themselves. It is preferable because the stain prevention effect can be obtained.

【0100】

Next, a binder layer is formed on the surface of the prepared base material. The binder layer is formed by selecting a binder material whose softening temperature is lower than the softening temperature of the base material and using this binder material by an appropriate method. For example, when the base material is tile, enamel or ceramic, the glaze layer or printing layer for coloring the surface can be used as it is as the binder layer. After the binder layer is formed, the mixed sol of the above-described embodiment is applied or printed on the surface of the binder layer, or mixed particles of titania particles and silica particles obtained by removing the solvent from the sol are sprayed. To form a hydrophilic imparting material layer which will be a surface layer later. Alternatively, a hydrophilic imparting material layer may be formed on a separately produced binder layer, and the binder layer may be placed on the surface of the base material. In these cases, the hydrophilicity-imparting material layer may be formed in the binder layer so as not to be separated from the binder layer at the time of subsequent firing.

【0101】

After that, the heat treatment is performed in a temperature environment that is higher than the softening temperature of the binder material of the binder layer in the range of 30 ° C. or higher and 300 ° C. or lower and lower than the softening temperature of the base material. By undergoing this heat treatment, the binder material is melted and solidified, the binder layer is firmly fixed to the tile surface, and the surface layer is formed from the hydrophilic imparting material layer. At this time, at the boundary with the binder layer, the particles of the hydrophilic imparting material (titania particles, silica particles) in the surface layer settle in the binder layer in the process of melting the binder material, and these particles are buried in the binder layer. It is held and firmly fixed to the binder layer. Further, in the hydrophilicity-imparting material layer, adjacent particles are bonded to each other by intermolecular force between the particles or sintering by firing to form a surface layer, and in this surface layer, titania and silica are respectively formed on the surface. Expose the particles. Therefore, the surface layer can be firmly fixed to the binder layer, and the particles of titania and silica can be effectively brought into contact with the outside air. Therefore, according to the production method in the other embodiment described above, it is possible to easily produce a building structure material or the like having a surface layer capable of exhibiting a high stain prevention effect based on high hydrophilicity.

【0102】

In this case, since the heating temperature is set to 30 ° C or more higher than the softening temperature of the binder material, it is preferable that the softening of the binder material by heating does not inadvertently take a long time, and it hinders the sedimentation and retention of the titania and silica particles. It is preferable because it is not messy. In addition, since the heating temperature is not higher than the softening temperature of the binder by more than 300 ° C, rapid melting of the binder material is avoided, and excessive sedimentation of titania and silica particles, generation of uneven surfaces, or pinholes occur. It is preferable because it can suppress problems such as occurrence. The heating temperature is preferably a temperature higher than the softening temperature of the binder material in the range of 50 ° C. or higher and 150 ° C. or lower.

【0103】

Next, another embodiment will be described. In this example, metal particles such as Pt, Rh, Pd, Cu, Ag, and Zn are supported and fixed on the particle surface of titania, which is a photocatalyst. In the production thereof, a sol in which these metal particles are dispersed in a titania sol may be prepared, and the sol may be used in place of the titania sol in each of the above-mentioned examples to form (fire) a surface layer. In this way, the above-mentioned metal enhances the generation of hydroxide radicals on the surface of titania, and can more reliably retain hydroxyl groups at a high density, thereby exhibiting high hydrophilicity. In this case, it may be a salt of the above metal.

【0104】

Returning to (Table 1), in Example tile 1 mixed with silica and Example tile 6 mixed with alumina, the contact angle was significantly reduced as compared with the comparative example tile containing only titania, and compared with the comparative example tile. It was possible to exhibit remarkably high hydrophilicity. Therefore, next, a mixture of titania and both silica and alumina was evaluated. The tiles and test methods used for the evaluation test at this time are as follows.

【0105】

(Procurement of photocatalyst and metal oxide sol) TiO₂Sol: Average particle size approx. 0.02 μm (manufactured by Ishihara Sangyo) SiO₂Sol: Average particle size approx. 0.007 to approx. 0.009 μm (Nissan Chemical Industries Snowtex S) Al2O₃Sol: Average particle size of about 0.01 to about 0.02 μm (Nissan Chemical Alumina Sol 520) (Adjustment of hydrophilicity-imparting material) To mix the metal oxide sol, the above sol is diluted in advance so that the solid content concentration becomes 0.4% by weight, and the titania sol and colloidal silica sol (Table 5) are mixed in the ratio shown in (Table 5) below. Nissan Chemical Snowtex S) was mixed and stirred, and then a predetermined amount of alumina sol was added and sufficiently stirred. At this time, sedimentation of the metal oxide did not occur. In addition, a mixed sol to which the alumina sol was not added and a mixed sol to which the colloidal silica sol was not added were also prepared. 0.4% by weight The weight of the liquid used for titania sol is a 0.4% by weight Colloidal silica sol used liquid weight b 0.4 Weight of liquid used in% alumina sol c Then, the solid content ratio in the total mixed sol is 0.4% by weight, and the solid content ratio of titania, silica, and alumina is a: b: c. (Making hydrophilic tiles) Glazed tiles (TOTO) AB06E11) was prepared as a base material, and a predetermined amount of each of the above titania mixed sol was spray-coated on the tile surface so that the film thickness was about 0.4 μm. This was fired at RHK (Roller Hers Kiln) at a maximum temperature of about 850 ° C to about 900 ° C and a firing time of about 60 minutes.

【0106】

[Table 5]

<img file="JPH10237416A_D0005.tif" />【0107】

The hydrophilicity was evaluated by the static contact angle of water. First, the test tiles were irradiated with a BLB fluorescent lamp (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB) having an ultraviolet illuminance of 1.2 mW / cm2 for 24 hours, and then the contact angle with water was measured. Then, it was stored in the shade for 72 hours (stored in a dark place), and the contact angle with water was measured. The results are shown in (Table 5) and FIGS. 5 and 6. In addition, the film strength was evaluated using the Mohs hardness. The results are shown in (Table 5) and FIGS. 7 and 8.

【0108】

Here, FIG. 5 is a graph showing the relationship between the amount of titania added and the contact angle of water under light irradiation, FIG. 6 is a graph showing the relationship between the amount of alumina added and the contact angle of water in a dark place, and FIG. 7 is a graph showing the relationship. A graph showing the relationship between the amount of alumina and silica added and the film strength, and FIG. 8 is a graph showing the relationship between the amount added and the film strength when only silica is added. The number of plots in the figure is smaller than the number of samples in (Table 5), because the numerical values of multiple samples overlap in one plot.

【0109】

From (Table 5) and FIG. 5, under ultraviolet irradiation, TiO₂/ (TiO₂+ SiO₂+ Al₂O₃) 0.5, the contact angle with water is 10 ° or less, and it can be seen that sufficient hydrophilicity is achieved. In addition, from (Table 5) and FIG. 6, TiO under storage in a dark place.₂If the amount of is the same, Al₂O₃It can be seen that the larger the amount of the addition, the higher the hydrophilicity is maintained. In addition, from (Table 5) and FIGS. 7 and 8, (SiO₂+ Al₂O₃) / (TiO₂+ SiO₂+ Al₂O₃) 0.5, SiO₂It can be seen that the hardness is increased by adding the above amount and by increasing the amount of the addition.

【0110】

To summarize the above, photocatalyst (TiO₂) To SiO₂And Al₂O₃By adding, the hydrophilicity under light irradiation is improved as compared with the photocatalyst alone, and the ability to maintain hydrophilicity in the dark is also improved, and further SiO₂And Al₂O₃It was also confirmed that the film hardness and denseness were improved by adding. Among these effects, it is considered that the improvement of hydrophilicity is mainly brought about by the addition of alumina, and the improvement of film hardness is mainly brought about by the addition of silica.

【0111】

And the above effects can be expected in particular. TiO₂/ (TiO₂+ SiO₂+ Al₂O₃) 0.5 (SiO₂+ Al₂O₃) / (TiO₂+ SiO₂+ Al₂O₃) 0.5 When the condition of is satisfied.

【0112】

Further, using the above Samples 2 and 8, a photocatalytic nitric oxide purification test was conducted. The device used was a fixed-bed flow reactor at normal temperature and pressure, and a sample tile of about 250 cm was placed in the reactor of this device.²Install and air air containing about 1ppm of nitric oxide (NO) here at a space velocity of 960h^-1The NOx concentration at the outlet of the reactor was measured using a chemiluminescent NOx concentration measuring device. In a dark place without light irradiation, the NOx concentration at the reactor outlet remained at 1 ppm, but when the sample tile was irradiated with ultraviolet rays (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB, wavelength was about 300 nm to about 400 nm). UV intensity in the range is about 0.4 mW / cm²), The NOx concentration at the reactor outlet decreased immediately. When the NOx purification rate was calculated from the total amount of NO supplied 1 hour from the start of UV irradiation and the total amount of NOx discharged from the reactor outlet, it was 16% for sample 2 and 25.4% for sample 8. From this, TiO₂, Al₂O₃And SiO₂It was found that the photocatalytic mixture consisting of the above three components has a high NOx purification ability.

【0113】

Furthermore, the above TiO₂, Al₂O₃And SiO₂Regarding the photocatalyst mixture consisting of the above three components, the following experiments were carried out for each mixing ratio based on hydrophilicity and film strength.

【0114】

(Procurement of photocatalyst and metal oxide sol) TiO₂Sol: Nissan Chemical Industries, Ltd. Titanium oxide sol TA-15 (solid content 15%) Al₂O₃Sol: Nissan Chemical Alumina Sol 520 (solid content 5%) SiO₂Sol: Nihon Synthetic Rubber Grasca T2202 (silica content 22%) [0115]

(Adjustment of coating liquid) After mixing the above raw materials at a constant ratio, dilute them 3 times with ethanol to prepare a coating liquid. The component ratios of the prepared coating liquid are shown in (Table 6) below.

【0116】

[Table 6]

<img file="JPH10237416A_D0006.tif" />【0117】

(Coating method) A tile is used as the base material, and a spin coating method (a method in which a coating liquid is dropped on the center of the base material and then the base material is rotated to form a film having a uniform thickness by centrifugal force) is performed. After applying each coating solution, it was heated at 150 ° C. for 30 minutes to cure.

【0118】

(Evaluation) For film hardness, a pencil hardness test (JIS K5400 paint general test) was conducted. The results are shown in (Table 7). Regarding hydrophilicity, the prepared sample was exposed to ultraviolet rays (manufactured by Sankyo Electric Co., Ltd., black light blue, FL20BLB, 1.2 mW / cm).²) Was irradiated. The results are shown in (Table 8).

【0119】

[Table 7]

<img file="JPH10237416A_D0007.tif" />【0120】

[Table 8]

<img file="JPH10237416A_D0008.tif" />【0121】

From (Table 7), SiO₂/ TiO₂Binders (SiO) with a value of 0.1 or less₂It can be seen that the film strength is extremely reduced due to the lack of sol). Also, from (Table 8), SiO₂/ TiO₂Is in the range of 1/5 to 2₂O₃/ TiO₂When is 1/12 to 2, it can be seen that the effect of improving the hydrophilicity rate by adding alumina is exhibited.

【0122】

In addition, Fig. 9 shows the amount of ultraviolet rays irradiated at 0.03 mW / cm.²The time course of the water contact angle between the alumina-added system and the non-added system is shown when the value is reduced, and it can be seen from this figure that the alumina addition effect is exhibited even in the region where the amount of ultraviolet rays is weak.

【0123】

That is, TiO₂, SiO₂Photocatalytic paint consisting of SiO₂/ TiO₂Is in the range of 1/5 to 2₂O₃TiO₂If only 1/12 to 2 is added to the above, high hydrophilicity can be exhibited.

【0124】

Although the examples of the present invention have been described above, the present invention is not limited to the above-mentioned examples and embodiments, and it is needless to say that the present invention can be carried out in various modes without departing from the gist of the present invention. ..

[Simple explanation of drawings]

[Figure 1]

Explanatory drawing which shows typically how the hydroxide radical generated by the photocatalyst titania is adsorbed on the silica surface.

[Figure 2]

The graph which shows the relationship between the tile surface temperature at the time of applying titania sol and forming a surface layer, and the surface roughness of the tile surface layer after firing.

[Fig. 3]

The graph which shows the relationship between the average film thickness of the surface layer at the time of applying titania sol and forming a surface layer, and the surface roughness of the tile surface layer after firing.

[Fig. 4]

A graph showing the relationship between the color value comparison value (ΔE *) and the surface roughness in the stain test by the flow-down pollution promotion test method.

[Fig. 5]

The graph which shows the relationship between the amount of titania addition and the contact angle of water under light irradiation.

[Fig. 6]

The graph which shows the relationship between the amount of alumina addition and the contact angle of water in a dark place.

[Fig. 7]

The graph which shows the relationship between the addition amount of alumina and silica, and the film strength.

[Fig. 8]

The graph which shows the relationship between the addition amount and the film strength when only silica is added.

[Fig. 9]

The amount of ultraviolet rays to irradiate is 0.03 mW / cm²The graph which shows the time-dependent change of the water contact angle between the alumina-added system and the non-added system when it is made small.