Low-reflectivity base, solar cell module using the same, and method of manufacturing low-reflectivity base

The present invention relates to a low-reflectivity substrate having a reduced reflectance and an increased amount of light transmission, a solar cell module using the same, and a method for manufacturing a low-reflection substrate.

In recent years, solar cells that directly convert solar energy into electrical energy are expected to be a next-generation energy source, especially from the viewpoint of global environmental problems. There are various types of solar cells, such as those using compound semiconductors or organic materials, but the mainstream at present is the one using silicon as the material. With the rapid spread of photovoltaic power generation systems, higher efficiency of solar cells is required, and even in solar cell modules, light reflection on the surface of the light-transmitting substrate arranged on the light receiving surface of the solar cells is reduced to reduce the sun. Improving the light transmittance to the battery cell is a very effective means. On the other hand, Patent Document 1 (Japanese Unexamined Patent Publication No. 11-179835) proposes a surface protective material in which titanium oxide fine particles are supported on the surface of a fluororesin-based film with a binder, for example, silicon dioxide. It is necessary to attach the film with an adhesive, and it is difficult in terms of productivity because a very complicated work is added especially in a solar cell module having a large light receiving area.

Further, Patent Document 2 (Japanese Unexamined Patent Publication No. 50-70040) describes that the surface of a lens substrate is etched to form fine irregularities having a predetermined pattern in order to reduce the reflectance. However, since the laser light interference is used for the etching process, the processing device becomes large-scale, and it is difficult in terms of productivity especially in a solar cell module or the like having a large light receiving area.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 11-179835</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 50-70040</text></patcit>

<p> The present invention has been made in view of the above prior art, and an object of the present invention is to provide a low-reflection substrate that reduces light reflection on the surface of the substrate and improves the light transmittance of a solar cell or the like. There is. Another object of the present invention is to provide a solar cell module using the above-mentioned low-reflection substrate.</p>

<p> An object of the present invention is a low-reflectivity substrate containing copper and zirconium-containing anatase-type titanium oxide and a silicon compound, and having a porous film having an average thickness of 50 nm to 300 nm and a maximum height of 30 nm or less on the surface. The anatase-type titanium oxide is composed of a mixture of anatase-type titanium oxide obtained by heating amorphous titanium oxide and anatase-type titanium oxide not obtained by heating amorphous titanium oxide. Achieved by a low reflectance substrate characterized by.</p><p> The low-reflectance substrate of the present invention is a reflectance reducing agent containing a thermally decomposable organic compound, an organosilicon compound and / or an inorganic silicon compound, and a mixture of copper and zirconium-containing amorphous titanium peroxide and anatase-type titanium peroxide. A low-reflectance substrate having an average thickness of 50 nm to 300 nm and a maximum height of 30 nm or less, which is obtained by applying the above to the surface of the substrate and heating the substrate, may be provided. In this case, regardless of the specific method for producing the reflectance-reduced porous film, all the substrates provided with the surface layer corresponding to the reflectance-reduced porous film are included in the category of the low-reflectance substrate of the present invention.</p><p> The average thickness of the reflectance-reduced porous film is preferably 130 nm to 180 nm.</p><p> The low-reflection substrate can be suitably used for a solar cell module.</p><p> The low-reflectivity substrate of the present invention is a reflectance reducing agent containing a pyrolyzable organosilicon compound, an organosilicon compound and / or an inorganic silicon compound, and a mixture of copper and zirconium-containing amorphous titanium peroxide and anatase-type titanium peroxide. Can be produced by applying the above to the surface of the substrate and heating it.</p><p> The pyrolytic organic compound is preferably a sugar or a sugar alcohol.</p><p> It is preferable that at least a part of the substrate is made of glass.</p><p> The heating is preferably performed at a temperature of 400 ° C. or higher.</p>

<p> According to the present invention, it is possible to provide a low-reflection substrate that reduces light reflection on the surface of the substrate and improves the light transmittance of a solar cell or the like. Therefore, the solar cell module provided with the low-reflection substrate of the present invention can bring about high power generation efficiency. In particular, in the present invention, the anatase-type titanium oxide obtained by heating amorphous titanium oxide using a reflectance reducing agent containing anatase-type titanium peroxide in addition to copper and zirconium-containing amorphous titanium peroxide. Since a reflectance-reducing film containing a mixture of anatase-type titanium oxide, which is not obtained by heating amorphous titanium oxide, is formed on the substrate, the light transmittance of the substrate can be further enhanced.</p><p> Further, when the average thickness of the reflectance-reduced porous film is 130 nm to 180 nm, the light transmittance can be further improved.</p>

In the present invention, a reflectance reducing agent which is a composition containing a thermally decomposable organosilicon compound, an organosilicon compound and / or an inorganic silicon compound, and a mixture of copper and zirconium-containing amorphous titanium peroxide and anatase-type titanium peroxide is used. A low-reflection substrate is produced by applying it to the surface of the substrate and heat-treating it.

In the present invention, "light" means an electromagnetic wave such as ultraviolet rays, visible rays, and infrared rays, and here, "visible light" means an electromagnetic wave having a wavelength of 380 nm to 780 nm.

As the substrate used in the present invention, various light-transmitting substrates can be used. The material of the substrate is not particularly limited, and hydrophilic or hydrophobic inorganic substrates and organic substrates, or a combination thereof can be used.

Examples of the inorganic substrate include transparent or translucent glass such as soda lime glass, quartz glass and heat-resistant glass, and a substrate made of a metal oxide such as indium tin oxide (ITO). Moreover, as an organic-based substrate, for example, a substrate made of plastic can be mentioned. More specifically, for example, plastics include polyethylene, polypropylene, polycarbonate, acrylic resin, polyester such as PET, thermoplastic resin such as polyamide, ABS resin and polyvinyl chloride, and polyurethane, melamine resin and urea resin. Examples thereof include thermosetting resins such as silicone resin, fluororesin, and epoxy resin. From the viewpoint of heat resistance, an inorganic substrate is preferable, and in particular, a substrate made of at least a part or preferably a whole glass is preferable. A thermosetting resin is preferable as the material of the organic substrate.

The shape of the substrate is not particularly limited, and any shape such as a cube, a rectangular parallelepiped, a sphere, a spindle shape, a sheet shape, a film shape, and a fibrous shape can be taken. The surface of the substrate may be made hydrophilic or hydrophobic by corona discharge treatment, ultraviolet irradiation treatment, or the like. The surface of the substrate may have a flat surface and / or a curved surface, and may be embossed, but smoothness is more preferable.

The reflectivity reducing agent used in the present invention is at least a mixture of a pyrolytic organic compound, an organosilicon compound and / or an inorganic silicon compound, and a copper- and zirconium-containing amorphous titanium peroxide and anatase-type titanium peroxide. It is a liquid composition containing.

The thermally decomposable organic compound is not particularly limited as long as it is an organic compound that decomposes by heating, but a compound that decomposes by heating and releases gas is preferable. The heating temperature is preferably 400 ° C. or higher, more preferably 450 ° C. or higher, and even more preferably 500 ° C. or higher. Examples of the pyrolytic organic compound include sugar or sugar alcohol, a water-soluble organic polymer, and a mixture thereof. Sugar or sugar alcohol is preferable, and sugar is more preferable.

Here, the "sugar" is a carbohydrate having a large number of hydroxy groups and carbonyl groups, and examples thereof include monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Examples of the monosaccharide include glucose, fructose, galactose, mannose, ribose, erythrose and the like. Examples of the disaccharide include maltose, lactose, sucrose (sucrose) and the like. Examples of oligosaccharides include fructooligosaccharides and galactooligosaccharides. Examples of the polysaccharide include starch, cellulose, pectin and the like. These may be used alone or as a mixture. From the viewpoint of usability, the sugar is preferably highly water-soluble. Therefore, in the present invention, one or a mixture of two or more selected from the group consisting of monosaccharides and disaccharides is preferably used.

The "sugar alcohol" is a reduced carbonyl group of a sugar. Specific examples of the sugar alcohol include erythritol, threitol, arabitol, xylitol, ribitol, mannitol, sorbitol, and multitoinositol. These may be used alone or as a mixture of two or more.

As the "water-soluble organic polymer", any thermally decomposable organic polymer can be used as long as it is water-soluble, but a polyether such as polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol block copolymer or the like can be used. Polyvinyl alcohol; polyacrylic acid (including salts such as alkali metal salt and ammonium salt), polymethacrylic acid (including salts such as alkali metal salt and ammonium salt), polyacrylic acid-polymethacrylic acid (including alkali metal salt, alkali metal salt, etc.) Copolymers (including salts such as ammonium salts); polyacrylamide; polyvinylpyrrolidone and the like can be mentioned.

The water-soluble organic polymer may be used alone, but since it can function as a solubilizing agent for sugars and / or sugar alcohols, it can be blended with sugars or sugar alcohols. As a result, the sugar or sugar alcohol can be satisfactorily dissolved in the reflectance reducing agent.

The concentration of the thermally decomposable organic compound in the composition can be appropriately changed depending on the degree of surface treatment of the substrate, but is typically 0.01 to 15% by weight, preferably 0.05 to 1.0% by weight. It is more preferably 0.1 to 5.0% by weight.

Examples of the organosilicon compound used in the present invention include various organosilane compounds and silicones such as silicone oil, silicone rubber and silicone resin. These may be used alone or as a mixture. As the silicone, those having an alkyl silicate structure or a polyether structure in the molecule, or those having both an alkyl silicate structure and a polyether structure are preferable. Here, the alkyl silicate structure refers to a structure in which an alkyl group is bonded to a silicon atom of a siloxane skeleton. On the other hand, the polyether structure refers to a structure having an ether bond, but are not limited to, specifically, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyethylene oxide - polypropylene emissions oxide block Examples thereof include molecular structures such as a copolymer, a polyethylene polytetramethylene glycol copolymer, and a polytetramethylene glycol-polypropylene oxide copolymer. Among them, the polyethylene oxide-polypropylene oxide block copolymer is suitable from the viewpoint that the wettability on the surface of the substrate can be controlled by its blocking degree and molecular weight.

As the organosilicon compound, silicone having both an alkyl silicate structure and a polyether structure in the molecule is particularly preferable. Specifically, polyether-modified silicones such as polyether-modified polydimethylsiloxane are suitable. This can be produced by a known method, for example, by the method described in Synthesis Examples 1, 2, 3, 4 of JP-A-4-242499, Reference Example of JP-A-9-165318, and the like. be able to. In particular, polyethylene oxide-polypropylene oxide block copolymer-modified polydimethylsiloxane obtained by reacting a double-terminal metalyl polyethylene oxide-polypropylene oxide block copolymer with dihydropolydimethylsiloxane is preferable. Specifically, use TSF4445, TSF4446 (GE Toshiba Silicone Co., Ltd.), KP series (Shin-Etsu Chemical Co., Ltd.), SH200, SH3746M, DC3PA, ST869A (Toray Dow Corning Co., Ltd.), etc. Can be done.

The concentration of the organosilicon compound in the composition can be appropriately changed depending on the degree of surface treatment of the substrate, but is typically 0.01 to 5.0% by weight, preferably 0.05 to 2.0% by weight. , More preferably 0.1 to 1.0% by weight.

Examples of the inorganic silicon compound used in the present invention include silica (silicon dioxide), silicon nitride, silicon carbide, silane, and the like, but silica is preferable. As the silica, fumed silica, colloidal silica, precipitated silica and the like can be used, but colloidal silica is preferable. Commercially available colloidal silica includes, for example, PL-1, PL-3 (Fuso Chemical Industry Co., Ltd.), and as polysilicates, WM-12 (manufactured by Tama Chemical Industry Co., Ltd.), Methyl silicate 51 (Colcoat Co., Ltd.). ) Etc. can be used.

The concentration of the inorganic silicon compound in the composition can be appropriately changed depending on the degree of surface treatment of the substrate, but is typically 0.01 to 95% by weight, preferably 0.1 to 90% by weight. , More preferably 10 to 80% by weight.

The copper and zirconium-containing amorphous titanium peroxide used in the present invention is a mixture of copper and zirconium and amorphous titanium peroxide. A mixture of copper-doped amorphous titanium peroxide and zirconium-doped amorphous titanium peroxide may be used, but both copper and zirconium-doped amorphous titanium peroxide should be used. Is preferable.

As a method for producing the amorphous titanium peroxide containing copper and / or zirconium, a production method based on the hydrochloric acid method or the sulfuric acid method, which is a general method for producing titanium dioxide powder, may be adopted, or various liquids may be produced. A method for producing a dispersed titania solution may be adopted. And copper and / or zirconium can be composited with titanium peroxide at any stage of production.

For example, specific methods for producing copper and / or zirconium-containing titanium peroxide include the following first to third production methods and conventionally known sol-gel methods.

First manufacturing method First, a compound of tetravalent titanium such as titanium tetrachloride is reacted with a base such as ammonia to form titanium hydroxide. Next, this titanium hydroxide is peroxozized with an oxidizing agent to form ultrafine particles of amorphous titanium peroxide. This reaction is preferably carried out in an aqueous medium. Furthermore, it is also possible to transfer to anatase-type titanium peroxide by arbitrary heat treatment. At least one of copper and / or zirconium, or a compound thereof, is mixed in any of the above steps.

The oxidizing agent for peroxolation is not particularly limited, and various types of peroxoized titanium, that is, those capable of forming titanium peroxide can be used, but hydrogen peroxide is preferable. When a hydrogen peroxide solution is used as the oxidizing agent, the concentration of hydrogen peroxide is not particularly limited, but 30 to 40% is preferable. It is preferable to cool the titanium hydroxide before peroxoification. The cooling temperature at that time is preferably 1 to 5 ° C.

FIG. 1 shows an example of the first manufacturing method. In the production method shown, an aqueous solution of titanium tetrachloride and aqueous ammonia are mixed in the presence of at least one of copper and / or zirconium or a compound thereof, and the hydroxide of the metal and the hydroxide of titanium are mixed. To produce a mixture of. The concentration and temperature of the reaction mixture at that time are not particularly limited, but are preferably diluted and at room temperature. This reaction is a neutralization reaction, and it is preferable that the pH of the reaction mixture is finally adjusted to around 7.

The copper and / or zirconium thus obtained and the hydroxide of titanium are washed with pure water, cooled to around 5 ° C., and then peroxozylated with hydrogen peroxide solution. This makes it possible to produce an aqueous dispersion containing fine particles of titanium peroxide having an amorphous peroxo group containing the metal, that is, an aqueous dispersion containing metal-doped titanium peroxide.

Second manufacturing method A compound of tetravalent titanium such as titanium tetrachloride is peroxozized with an oxidizing agent, and this is reacted with a base such as ammonia to form ultrafine particles of amorphous titanium peroxide. This reaction is preferably carried out in an aqueous medium. Furthermore, it is also possible to transfer to anatase-type titanium peroxide by optionally heating and embedding. At least one of copper and / or zirconium, or a compound thereof, is mixed in any of the above steps.

Third manufacturing method A compound of tetravalent titanium such as titanium tetrachloride is reacted at the same time as an oxidizing agent and a base to simultaneously form titanium hydroxide and peroxoize it to form ultrafine particles of amorphous titanium peroxide. This reaction is preferably carried out in an aqueous medium. Furthermore, it is also possible to transfer to anatase-type titanium peroxide by optionally heating and embedding. At least one of copper and / or zirconium, or a compound thereof, is mixed in any of the above steps.

In general, amorphous titanium peroxide is transferred to anatase-type titanium peroxide by heating. In the first to third production methods, a mixture of amorphous titanium peroxide and anatase-type titanium peroxide obtained by heating the amorphous titanium peroxide can also be used as the metal-doped titanium peroxide.

Manufacturing method by sol-gel method A solvent such as water or alcohol, an acid or a base catalyst is mixed and stirred with the titanium alkoxide to hydrolyze the titanium alkoxide to produce an ultrafine titanium peroxide sol solution. Before or after this hydrolysis, copper and / or zirconium, or at least one of their compounds, is mixed. The titanium peroxide thus obtained is an amorphous type having a peroxo group.

As the above titanium alkoxide, the general formula: Ti (OR ́)₄(However, R ́ is an alkyl group), or a compound in which one or two alkoxide groups (OR ́) in the above general formula are substituted with a carboxyl group or a β-dicarbonyl group, or those. Is preferred.

As a specific example of the above titanium alkoxide, Ti (O-isoC)₃H₇)₄, Ti (O-nC₄H₉)₄, Ti (O-CH₂CH (C₂H₅) C₄H₉)₄, Ti (OC₁₇H₃₅)₄, Ti (O-isoC₃H₇)₂[CO (CH)₃) CHCOCH₃]₂, Ti (O-nC₄H₉)₂[OC₂H₄N (C₂H₄OH)₂]₂, Ti (OH)₂[OCH (CH)₃) COOH]₂, Ti (OCH₂CH (C₂H₅) CH (OH) C₃H₇)₄, Ti (O-nC₄H₉)₂(OCOC₁₇H₃₅) Etc. can be mentioned.

Compound of tetravalent titanium The tetravalent titanium compound used in the production of metal-doped titanium oxide is orthotitanium acid (H) when reacted with a base.₄TiO₄), Various titanium compounds can be used as long as they can form titanium hydroxide. For example, there are water-soluble inorganic acid salts of titanium such as titanium tetrachloride, titanium sulfate, titanium nitrate and titanium phosphate. In addition, a water-soluble organic acid salt of titanium such as titanium oxalate can also be used. Among these various titanium compounds, titanium tetrachloride is preferable because it is particularly excellent in water solubility and components other than titanium do not remain in the dispersion liquid of metal-doped titanium peroxide.

When a solution of a tetravalent titanium compound is used, the concentration of the solution is not particularly limited as long as a titanium hydroxide gel can be formed, but a relatively dilute solution is preferable. Specifically, the solution concentration of the tetravalent titanium compound is preferably 5 to 0.01% by weight, more preferably 0.9 to 0.3% by weight.

base As the base to be reacted with the above-mentioned tetravalent titanium compound, various bases can be used as long as they can react with the tetravalent titanium compound to form titanium hydroxide, such as ammonia, caustic soda, sodium carbonate, and the like. Caustic potash and the like can be exemplified, but ammonia is preferable.

When the above-mentioned base solution is used, the concentration of the solution is not particularly limited as long as a titanium hydroxide gel can be formed, but a relatively dilute solution is preferable. Specifically, the concentration of the base solution is preferably 10 to 0.01% by weight, more preferably 1.0 to 0.1% by weight. In particular, when aqueous ammonia is used as the base solution, the concentration of ammonia is preferably 10 to 0.01% by weight, more preferably 1.0 to 0.1% by weight.

Metal compound Examples of copper and zirconium compounds include the following, respectively. Cu compound: Cu (OH)₂, Cu (NO)₃)₂, CuSO₄, CuCl₂, Cu (CH)₃COO)₂ Zr compound: Zr (OH)₃, ZrCl₂, ZrCl₄

The concentration of titanium peroxide (total amount including coexisting copper and / or zirconium) in the aqueous dispersion obtained by the first to third production methods is preferably 0.05 to 15% by weight, more preferably 0.1 to 5% by weight. preferable. Regarding the blending amount of copper and / or zirconium, the molar ratio of titanium and the metal component is preferably 1: 1 from the present invention, but is preferably 1: 0.01 to 1: 0.5 from the viewpoint of the stability of the aqueous dispersion. , 1: 0.03 to 1: 0.1 is more preferable.

Commercially available products of copper and / or zirconium-containing amorphous titanium peroxide include, for example, copper-doped titania aqueous dispersion Z18-1000nA and copper and zirconium-doped titania aqueous dispersion Z18-1000SuperA (all manufactured by Sustainable Technology Co., Ltd.). Can be mentioned.

The reflectance reducing agent used in the present invention includes anatase-type titanium peroxide as well as copper and zirconium-containing amorphous titanium peroxide obtained as described above. As the anatase-type titanium peroxide, amorphous titanium peroxide may be transferred by heating, but anatase-type titanium peroxide in which amorphous titanium peroxide is not transferred by heating is preferable. That is, the anatase-type titanium peroxide contained in the reflectance reducing agent may be one in which a part of the amorphous-type titanium peroxide is transferred by heating and formed in-situ, but at least a part thereof (preferably). Is preferably added separately from the outside.

The concentration of the mixture of copper and zirconium-containing amorphous titanium peroxide and anatase-type titanium peroxide in the composition can be appropriately changed depending on the degree of surface treatment of the substrate, but is typically. Is 0.01 to 20% by weight, preferably 0.05 to 15% by weight, and more preferably 0.1 to 10% by weight.

The reflectance reducing agent used in the present invention preferably contains an aqueous medium which is water, alcohol or a mixture thereof, or a non-aqueous medium such as an organic solvent. In terms of the solubility of the pyrolytic organic compound, the reflectance reducing agent preferably contains an aqueous medium. The concentration of these media is typically 50-99.9% by weight, preferably 60-99% by weight, more preferably 70-97% by weight.

The low-reflection substrate of the present invention can be produced by applying the above-mentioned reflectance reducing agent to the surface of the substrate and heating the substrate.

The means and method for applying the reflectance reducing agent are not particularly limited, and any means and method can be used. For example, any coating method such as a dip method, a spray method, a roll coater method, a spin coater method, and a sponge sheet method can be used. In particular, since the hydrophilic sponge sheet can efficiently absorb the reflectance reducing agent and transfer it to the substrate, it is possible to suppress scattering loss and form an economically uniform reflectance reducing film.

The heating is not particularly limited as long as it is above the temperature at which the thermally decomposable organic compound in the reflectance reducing agent is decomposed, but the thermally decomposable organic compound is a sugar or sugar alcohol, or a water-soluble organic polymer. In the case of, the temperature at which decomposition gas such as water vapor or carbon dioxide is generated is preferable, 400 ° C or higher is more preferable, 450 ° C or higher is even more preferable, and 500 ° C or higher is even more preferable. The upper limit of the heating temperature is not particularly limited, but from the viewpoint of affecting various characteristics of the substrate, it is preferably 1000 ° C or lower, more preferably 850 ° C or lower, and 800 ° C or lower. Even more preferable. The heating time is also not particularly limited as long as the pyrolytic organic compound can be sufficiently carbonized, but is preferably 1 minute to 3 hours, more preferably 1 minute to 1 hour, and even more preferably 1 minute to 30 minutes.

When untempered glass is used as the substrate, the temperature is preferably the temperature required for strengthening the untempered glass, for example, the temperature is preferably 650 ° C or higher. Here, the untempered glass means a glass whose strength is improved by heat treatment, and it does not matter whether or not the glass has already been heat-treated before heating.

By heating, titanium peroxide in the reflectance reducing agent is changed to titanium oxide (titanium dioxide). At this time, the amorphous titanium oxide is further transferred to the anatase type titanium oxide (generally, the amorphous titanium oxide is transferred to the anatase type by heating at 100 ° C. for 2 hours or more). Therefore, copper and / or zirconium-containing anatase-type titanium oxide obtained by the process of amorphous titanium peroxide amorphous titanium oxide anatase-type titanium oxide is present on the surface of the low-reflection substrate of the present invention. Further, the anatase-type titanium peroxide already contained in the reflectance reducing agent is changed to anatase-type titanium oxide as it is by heating.

On the surface of the heat-treated substrate, a porous layer having a large number of fine irregularities is formed on the surface by ejecting decomposition products (water vapor, carbon dioxide, etc.) derived from the thermally decomposable organic compound in the reflectance reducing agent. Will be done. Due to these fine irregularities, the reflectance of the surface of the substrate is reduced, and as a result, the light transmittance of the substrate is improved. The average thickness of the porous layer is 50 to 300 nm, preferably 80 to 250 nm, more preferably 100 to 200 nm, and particularly preferably 130 to 180 nm.

The porous layer has a surface roughness with a maximum height (Rmax) of 30 nm or less, and the maximum height is more preferably 25 nm or less, more preferably 5 to 20 nm. By setting the average thickness of the reflectance-reducing film to 50 nm to 300 nm, a porous film with reduced reflectance of a certain thickness or more is secured from the substrate side even if it has an uneven shape (Rmax 30 nm). For example, when the film thickness of the reflectance-reducing film is 300 nm, the thickness of the reflectance-reducing porous film below the deepest part of the film surface is approximately 270 nm to 295 nm. When the film thickness of the reflectance-reducing film is 160 nm, the thickness of the reflectance-reduced porous film below the deepest part of the film surface is approximately 130 nm to 155 nm. When the film thickness of the reflectance-reducing film is 80 nm, the thickness of the reflectance-reduced porous film below the deepest part of the film surface is approximately 50 nm to 75 nm.

In the present invention, the surface of the substrate itself is not formed with fine irregularities by etching or the like, but a thin porous layer is formed on the surface of the substrate to form fine irregularities on the surface of the substrate. No microfabrication is required, and unevenness can be easily formed. Further, since the reflectance reducing agent, which is a precursor of the porous layer, is applied to the surface of the substrate by coating, the surface of the substrate can be treated over a wide range, and the substrate has a curved surface like a lens. However, unevenness can be easily formed. Further, even in the case of a solar cell module or the like that employs a texture structure on the surface of the light transmissive substrate, the reflectance reducing film can be easily formed.

Therefore, in the present invention, it is possible to reduce the reflectance of the substrate by a simple method applicable regardless of the material and shape of the substrate, whereby the transmittance is increased and the optical characteristics are improved. A sex substrate can be provided.

In addition to the above-mentioned components, the reflectance reducing agent of the present invention may contain various positively charged substances, negatively charged substances, or mixtures thereof. As a result, contamination of the surface of the substrate is avoided or reduced, so that low reflectivity can be maintained for a long period of time.

Examples of the positively charged substance include cations; a conductor or a dielectric having a positive charge; a composite of a conductor having a positive charge and a dielectric or a semiconductor; or a mixture thereof.

The cation is not particularly limited, but is an ion of an alkali metal such as sodium and potassium; an ion of an alkaline earth metal such as calcium; aluminum, tin, cesium, indium, cerium, selenium, chromium and nickel. , Antimony, iron, copper, manganese, tungsten, zirconium, zinc and other metal element ions are preferable, and copper ion is particularly preferable. Further, an organic molecule having a cationic dye such as methyl violet, bismarck brown, methylene blue or malachite green, or a cationic group such as silicone modified by a quaternary nitrogen atom-containing group can also be used. The valence of the ion is not particularly limited, and for example, a cation having a valence of 1 to 4 can be used.

It is also possible to use a metal salt as a source of the metal ions. Specifically, aluminum chloride, 1st and 2nd tin chloride, chromium chloride, nickel chloride, 1st and 2nd antimony chloride, 1st and 2nd iron chloride, cesium chloride, indium trichloride, 1st cerium chloride, Examples thereof include various metal salts such as selenium tetrachloride, cupric chloride, manganese chloride, tungsten tetrachloride, tungsten oxydichloride, potassium tungstate, zirconium oxychloride, zinc chloride and barium carbonate. Further, metal hydroxides such as aluminum hydroxide, iron hydroxide, chromium hydroxide and indium hydroxide, hydroxides such as silicate tungsten acid, and oxides such as oil and fat oxides can also be used.

Examples of the conductor or dielectric having a positive charge include a conductor or a dielectric in which a positive charge is generated other than the above-mentioned cations. For example, the conductor used is a metal from the viewpoint of durability. Desirably, metals such as aluminum, tin, cesium, indium, cerium, selenium, chromium, nickel, antimony, iron, silver, copper, manganese, platinum, tungsten, zirconium, zinc and the like, and metals oxide can be mentioned. In addition, composites or alloys of these metals can also be used. The shape of the conductor is not particularly limited, and any shape such as a particle shape, a flaky shape, and a fibrous shape can be taken.

As the conductor, metal salts of some metals can also be used. Specifically, aluminum chloride, 1st and 2nd tin chloride, chromium chloride, nickel chloride, 1st and 2nd antimony chloride, 1st and 2nd iron chloride, silver nitrate, cesium chloride, indium trichloride, 1st chloride. Various metal salts such as cerium, selenium tetrachloride, cupric chloride, manganese chloride, platinum chloride, tungsten tetrachloride, tungsten oxydichloride, potassium tungstate, gold chloride, zirconium oxychloride, zinc chloride, etc. It can be exemplified. Further, hydroxides or oxides such as indium hydroxide and silicotungstic acid can also be used.

Examples of the dielectric having a positive charge include dielectrics such as wool and nylon that are positively charged by friction.

Next, FIG. 2 shows the principle of applying a positive charge by the complex. FIG. 2 is a conceptual diagram in which a combination of a conductor-dielectric or a semiconductor-conductor is arranged on the surface or a surface layer of a substrate (not shown). A conductor can have a positively charged state on its surface due to the presence of free electrons that can move freely inside at a high concentration. It is also possible to use a conductive substance containing cations as the conductor.

On the other hand, the dielectric or semiconductor adjacent to the conductor is dielectrically polarized due to the influence of the surface charge state of the conductor. As a result, a negative charge is generated on the side adjacent to the conductor and a positive charge is generated on the non-adjacent side of the dielectric or the semiconductor. Due to these actions, the surface of the conductor-dielectric or semiconductor-conductor combination becomes positively charged, and the positive charge is applied to the surface of the substrate. The size of the complex (meaning the length of the longest axis passing through the complex) can be in the range of 1 nm to 100 μm, preferably 1 nm to 10 μm, more preferably 1 nm to 1 μm, more preferably 1 nm to 100 nm. ..

The conductor constituting the composite used in the present invention is preferably a metal from the viewpoint of durability, and aluminum, tin, cesium, indium, cerium, selenium, chromium, nickel, antimony, iron, silver, copper, manganese, and platinum. , Tungsten, zirconium, zinc and other metals. In addition, oxides, complexes or alloys of these metals can also be used. The shape of the conductor is not particularly limited, and any shape such as a particle shape, a flaky shape, and a fibrous shape can be taken.

As the conductor, metal salts of some metals can also be used. Specifically, aluminum chloride, 1st and 2nd tin chloride, chromium chloride, nickel chloride, 1st and 2nd antimony chloride, 1st and 2nd iron chloride, silver nitrate, cesium chloride, indium trichloride, 1st chloride. Cerium, selenium tetrachloride, cupric chloride, manganese chloride, platinum chloride, tungsten tetrachloride, tungsten oxydichloride, potassium tungstate, gold chloride, zirconium oxychloride, zinc chloride, lithium iron phosphate, etc. Various metal salts can be exemplified. Further, hydroxides of the above-mentioned conductor metals such as aluminum hydroxide, iron hydroxide and chromium hydroxide, and oxides of the above-mentioned conductor metals such as zinc oxide can also be used.

Conductors include polyaniline, polypyrrole, polythiophene, polythiophene vinylone, polyisothianaften, polyacetylene, polyalkylpyrrole, polyalkylthiophene, poly-p-phenylene, polyphenylene vinylone, polymethoxyphenylene, polyphenylensulfide, polyphenylene oxide, poly. Conductive polymers such as anthracene, polynaphthalene, polypyrrole, and polyazulene can also be used.

Examples of semiconductors include C, Si, Ge, Sn, GaAs, Inp, GeN, ZnSe, and PbSnTe, and semiconductor oxide metals, opto-semiconductor metals, and opto-semiconductor oxides can also be used. Preferably, titanium oxide (TiO)₂), ZnO, SrTiOP₃, CdS, CdO, CaP, InP, In₂O₃, CaAs, BaTiO₃, K₂NbO₃, Fe₂O₃, Ta₂O₃, WO₃, NiO, Cu²O, SiC, SiO₂, MoS₃, InSb, RuO₂, CeO₂Etc. are used, but those in which the photocatalytic activity is inactivated with Na or the like are desirable.

As the dielectric, barium titanate (PZT), which is a ferroelectric substance, so-called SBT, BLT and the following PZT, PLZT (Pb, La) (Zr, Ti) O₃, SBT, SBTN-SrBi₂(Ta, Nb)₂O₉, BST (Ba, Sr) TiO₃, LSCO (La, Sr) CoO₃, BLT, BIT (Bi, La)₄Ti₃O₁₂, BSO-Bi₂SiO₅And other composite metals can be used. Further, silane compounds and silicone compounds which are organic silicon compounds, so-called organically modified silica compounds, organic polymer insulating films, allylene ether-based polymers, benzocyclobutene, fluoropolymer parylene N or F, fluorinated amorphous carbon, etc. Various low dielectric materials can also be used.

Next, Fig. 3 shows the mechanism by which contaminants are removed from the surface of the positively charged substrate.

First, a positive charge is applied to the surface of the substrate (Fig. 3 (1)).

Pollutants are deposited on the surface of the substrate and are photooxidized by the action of electromagnetic waves such as sunlight. The photooxidation reaction is the action of electromagnetic waves such as sunlight, which causes water (H) on the surface of organic or inorganic substances.₂O), oxygen (O)₂) From hydroxyl radical ( OH) and singlet oxygen (¹O₂) Is generated, an electron (e) is generated from the organic or inorganic substance.^-) Is pulled out and oxidized. Due to this oxidation, the molecular structure of organic substances changes, and a discoloration or embrittlement phenomenon called deterioration is observed, and rust occurs in inorganic substances, especially metals. The surface of these "oxidized" organic or inorganic substances is an electron (e).^-) Is pulled out to be positively charged. In this way, the pollutants are also positively charged (Fig. 3 (2)).

Electrostatic repulsion between positive charges is generated between the surface of the substrate and the pollutant, and a repulsive detachment force is generated in the pollutant. This reduces the adhesion of contaminants to the surface of the substrate (Fig. 3 (3)).

Pollutants are easily removed from the substrate by physical action such as wind and rain (Fig. 3 (4)). As a result, the substrate is self-cleaned.

Examples of the negatively charged substance include anions; a conductor or a dielectric having a negative charge; a composite of a conductor having a negative charge and a dielectric or a semiconductor; or a mixture thereof.

The anion is not particularly limited, but is a halide ion such as a fluoride ion, a chloride ion or an iodide ion; an inorganic ion such as a hydroxide ion, a sulfate ion, a nitrate ion or a carbonate ion. ; Organic ions such as acetate ion can be mentioned. The valence of the ion is not particularly limited, and for example, 1 to tetravalent anions can be used.

Examples of the negatively charged conductor or dielectric include conductors or dielectrics that generate a negative charge other than the above-mentioned anions, and examples thereof include metals such as gold, silver, and platinum; Elements such as selenium and tellurium; sulfides such as arsenic sulfide, antimony sulfide, mercury sulfide; clay, glass powder, quartz powder, asbestos, starch, cotton, silk, wool, etc .; Examples of dye colloids such as. Among these, colloids of metals such as gold, silver and platinum are preferable, and silver colloids are more preferable. In addition to this, negative electrodes of batteries made of various conductors described above, and dielectrics such as negatively charged Teflon (registered trademark), vinyl chloride, polyethylene, and polyester can be mentioned.

As the semiconductor, those described above can be used.

The surface of the negatively charged substrate electrostatically repels the negatively charged contaminants, as in the case of the positively charged substrate shown in FIG. 3, so that the contaminants reach the surface of the substrate. Can be avoided.

On the other hand, some pollutants initially had a positive charge but became negatively charged due to interaction with other objects (friction, etc.). Such positively and negatively charged contaminants are easily adsorbed on the surface of a single charged substrate. Therefore, in that case, by applying both positive and negative charges to the substrate, it is possible to prevent these contaminants from adhering to the surface of the substrate.

For example, for pollutants having both positive and negative charges such as pollen, by blending both the positive charge substance and the negative charge substance in the reflectance reducing agent of the present invention, adhesion to these substrates can be avoided. Or it can be reduced. For example, on the surface of a substrate having a positive charge and a negative charge, contaminant attractants having a negative charge or an amphoteric charge such as yellow sand, kalion clay fine powder, algae, pollen, chloride ions in tap water, etc. are electrostatically charged. It repels the charge and prevents it from adhering to the surface of the substrate. Therefore, it is possible to prevent the change in the surface characteristics of the substrate due to the adhesion of such impurities and keep the surface of the substrate clean. If either the amount of positive charge or the amount of negative charge is excessively large, the tendency to adsorb positively charged impurities or positively charged contaminants due to photooxidation increases, and as a result, the surface of the substrate may be contaminated. Therefore, it is preferable that the amount of positive charge and the amount of negative charge are apparently balanced on the surface of the substrate, and specifically, the voltage band on the surface of the substrate is preferably in the range of -50V to 50V. is there.

Further, a pollutant composed of an insulator (for example, silicone oil) having a relatively small amount of positive or negative charge is a pollutant when only a strong positive or negative charge is present on the surface of the substrate depending on the type of the substance. Since the surface charge of the substance may be inverted and the contaminated substance may be adsorbed on the surface of the substrate as a result, such adsorption is avoided or reduced by coexisting both the positively charged substance and the negatively charged substance. By doing so, it is possible to prevent a decrease in the transmittance.

FIG. 4 is a conceptual diagram showing one aspect of imparting a positive charge and a negative charge to the surface of the substrate.

FIG. 4 is a conceptual diagram showing an example of a positive charge and negative charge imparting mechanism. Dielectric or semiconductor-a conductor having a negative charge-dielectric or a semiconductor-a conductor having a positive charge on a substrate (not shown). There is a combination of.

As the conductor having a negative charge and the conductor having a positive charge shown in FIG. 4, those described above can be used.

As shown in FIG. 4, the dielectric or semiconductor adjacent to the negatively charged conductor is dielectrically polarized due to the influence of the surface charge state of the conductor. As a result, a positive charge is generated on the side adjacent to the conductor having a negative charge, and a negative charge is generated on the dielectric or the semiconductor on the side adjacent to the conductor having a positive charge. Due to these actions, the surface of the dielectric or semiconductor-conductor-dielectric or semiconductor-conductor combination shown in FIG. 4 becomes negatively charged together with positive charges, and when the number of positive charges and the number of negative charges are the same, , The surface of the substrate is apparently kept electrically neutral. The size of the complex of the conductor and the dielectric or semiconductor (meaning the length of the longest axis passing through the complex) is 1 nm to 100 μm, preferably 1 nm to 10 μm, more preferably 1 nm to 1 μm, and more preferably 1 nm. It can be in the range of 100 nm.

FIG. 5 is a conceptual diagram showing another aspect of imparting positive and negative charges to the surface of the substrate.

In FIG. 5, the conductor having a negative charge and the conductor having a positive charge are adjacent to each other, and the positive charge and the negative charge are in a state of being small due to contact disappearance or the like. As the conductor having a negative charge and the conductor having a positive charge, those described above can be used.

Positively and negatively charged substrates can also remove positively charged contaminants. Figure 6 shows the mechanism by which positively charged and negatively charged contaminants are removed from the surface of the positively and negatively charged substrate. For convenience, the layers containing the positively charged substance and the negatively charged substance are arranged as a single layer, but may be a plurality of layers.

First, as shown in FIG. 6, a positive charge and a negative charge are applied to the surface of the substrate (Fig. 6 (1)).

Pollutants are deposited on the surface of the substrate and are photooxidized by the action of electromagnetic waves such as sunlight. In this way, the pollutants are also positively charged (Fig. 6 (2)).

Electrostatic repulsion between positive charges is generated between the surface of the substrate and the pollutant, and a repulsive detachment force is generated in the pollutant. This reduces the ability of contaminants to adhere to the surface of the substrate (Fig. 6 (3)).

Pollutants are easily removed from the substrate by physical action such as wind and rain (Fig. 6 (4)). As a result, the substrate is self-cleaned.

The reflectance reducing agent may contain various metals (Ag, Pt). In addition, various substances such as metal salts can be contained within a range that does not inactivate the function. Examples of the metal salt include metal salts such as aluminum, tin, chromium, nickel, antimony, iron, silver, cesium, indium, cerium, selenium, copper, manganese, calcium, platinum, tungsten, zirconium, and zinc. In addition, hydroxides or oxides can be used for some metals or non-metals. Specifically, aluminum chloride, first and second tin chloride, chromium chloride, nickel chloride, first and second antimony chloride, first and second iron chloride, silver nitrate, cesium chloride, indium trichloride, first chloride. Various metals such as cerium, selenium tetrachloride, cupric chloride, manganese chloride, calcium chloride, ferric chloride, tungsten tetrachloride, tungsten oxydichloride, potassium tungstate, ferric chloride, zirconium oxychloride, zinc chloride A salt can be exemplified. Examples of the compound other than the metal salt include indium hydroxide, silicotungstic acid, silica sol, calcium hydroxide and the like.

By the way, since the positively charged substance, the negatively charged substance, or a combination thereof makes the surface of the substrate hydrophilic, the formation of water droplets on the surface of the substrate is prevented or reduced. Therefore, it is possible to avoid a decrease in light transmission due to refraction and diffuse reflection due to water droplets on the surface of the substrate.

In the present invention, an intermediate layer may be present between the porous layer and the surface of the substrate. The intermediate layer can be made of, for example, various organic or inorganic substances capable of imparting hydrophilicity or hydrophobicity or water repellency or oil repellency to the substrate.

The substrate obtained by the present invention can be used in any field, and is particularly effective as a component of an apparatus for which improvement in light transmission and reduction in reflectance are required. For example, face glass of photocells such as solar cells; face glass of various displays such as liquid crystal displays, plasma displays, organic EL displays, and brown tube televisions; optical elements such as lenses; building members such as window glasses; and various light receivers. , Light emitters, projectors, polarizing glass, optical glass and the like. In particular, when it is used on the face glass of a photovoltaic cell such as a solar cell used outdoors or on the surface of a generator cell, it can contribute to the improvement of power generation efficiency due to its low reflectivity.

The low-reflection substrate of the present invention can be suitably used for a solar cell module.

Since the solar cell module is installed outdoors, weather resistance is required. Therefore, in general, a solar cell module is manufactured by heating a thermoplastic resin or the like to seal the solar cell and arranging a light-transmitting substrate on the surface thereof. Then, in order to improve the power generation efficiency of the solar cell, it is preferable that the reflectance of the surface of the solar cell module is as low as possible.

As a method for reducing the reflectance of the surface of the solar cell module, the surface of the light-transmitting substrate on the surface of the solar cell module is previously coated with a reflectance-reducing film that can withstand the heating temperature in the manufacturing process of the solar cell module, or It is necessary to coat the surface of the light-transmitting substrate with a reflectance-reducing film when the production of the solar cell module is completed or when the heating step is completed. Therefore, when a film for reducing reflectance that cannot withstand the heating temperature is attached to the surface of a light-transmitting substrate with an adhesive, the film is attached when the heating step is completed, but resin sealing is performed. At this time, it is necessary to remove deposits such as resin residue adhering to the surface of the light transmissive substrate and clean the surface of the light transmissive substrate so as not to impair the adhesion to the film.

Further, as a method of suppressing light reflection on the surface of the light-transmitting substrate, there is a method of adopting a so-called texture structure in which relatively large irregularities are formed on the surface of the light-transmitting substrate. Since it accumulates in the recesses, the installation angle of the solar cell module is restricted, and it becomes necessary to process the surface of the light-transmitting substrate to make it difficult to adhere. In the case of a light-transmitting substrate having relatively large irregularities on the surface shape as described above, it is difficult to attach the film to the surface with an adhesive.

Furthermore, solar cells have a unique wavelength of electromagnetic waves (sunlight in this case) that contributes to solar cell power generation, and it is necessary to consider not only weather resistance but also light transmission to a specific wavelength. That is, in general, various metals, metal oxides, organic metal compounds, and inorganic metal compounds are added to the light-transmitting substrate as needed to adjust the light absorption / reflection characteristics. , The reflectance of a specific wavelength region is lowered. For example, infrared rays and the like may be cut, but it is also important to improve the transmittance of wavelengths that positively contribute to power generation.

As described above, it is necessary to consider various factors in the solar cell module. However, the solar cell module having the low-reflection substrate of the present invention as a component does not require a film for reducing reflectance, and the surface irregularities are fine, so that the installation angle may be limited. No further surface treatment is required. Further, since the low-reflection substrate of the present invention has high light transmission, the solar cell module having the substrate as a component has high power generation efficiency.

The solar cell module provided with the low-reflection substrate of the present invention can be manufactured as follows.

After cleaning at least the light-receiving surface of the glass plate serving as the low-reflection substrate as the surface material (front cover member) of the solar cell module, the above-mentioned reflectance reducing agent is dropped with the light-receiving surface front side of the glass plate facing up. After applying evenly to the surface of the glass plate, it is naturally dried or forcibly dried for about 10 to 30 minutes, and then heated at 450 ° C or more and less than 850 ° C for about 10 minutes to strengthen the glass and reduce the reflectance. The sugar is calcined to form a reflectance-reducing film having an average thickness of 50 nm to 300 nm. In this way, a reflectance reducing film is formed on the surface, and a reinforced low-reflection substrate is completed.

Next, when a solar cell using a silicon substrate is used, the solar cells are connected to each other with a wiring material called an interconnector to form a solar cell string, and a plurality of solar cell strings are wired with a bus bar. Materials are used to connect to each other to form a solar cell cell array.

Then, the EVA (ethylene vinyl acetate) resin sheet as a sealing material is placed on the glass plate as the low-reflective substrate with the surface side facing down, and the solar cell cell array is placed on the EVA (ethylene vinyl acetate) resin sheet. Then, an EVA resin sheet to be a sealing material is further arranged on the EVA resin sheet, and finally, a weather resistant film to be a back surface cover member formed of an acrylic resin or the like is sequentially laminated to form a laminate. In this state, the laminate is heated at a temperature of about 150 ° C. and pressed in a vacuum-conditioned container to depressurize and remove air bubbles entering each layer. In the laminating process, the EVA resin is melted and crosslinked and cured, so that the solar cell cell array is sealed by the EVA resin and the laminated body is integrated. After integrating the entire laminate, the EVA resin or weather-resistant film that protrudes from the end face is cut, and a moisture-resistant insulating material such as butyl rubber is attached to the cut surface including the end face of the glass plate, and an aluminum frame is attached. The solar cell module is completed by connecting a terminal box to a pair of external terminals extending to the outside via a string and removing dust and EVA residue on the surface of the glass plate. Even if the solar cell is a thin-film solar cell module formed on a glass substrate or the like, it can be manufactured basically through the same process.

Hereinafter, the present invention will be illustrated in more detail by way of examples, but the present invention is not limited to the examples.

(Evaluation liquid 1) Amorphous titanium peroxide aqueous dispersion prepared by the following method, copper-doped titania (amorphous titanium peroxide) aqueous dispersion (Z18-1000nA (manufactured by Sustainable Technology Co., Ltd.) (concentration 0.6% by weight) )), Amorphous titanium peroxide aqueous dispersion (B51 (manufactured by Sustainable Technology Co., Ltd.) (adjusted to a concentration of 0.6% by weight)), and polysilicate (WM-12 (Tama Chemical Industry Co., Ltd.)). (Manufactured by Co., Ltd.)) is mixed at a ratio of 1: 1: 1: 7 (weight ratio), and the mixture is further mixed with an aqueous dispersion of an organic silicon compound (ZB (manufactured by Sustainable Technology Co., Ltd.)). Evaluation solution 1 was prepared by adding 10% by weight and 1% by weight of commercially available white sugar.

(Preparation of zirconium-doped amorphous titanium peroxide aqueous dispersion) 50% titanium tetrachloride solution (manufactured by Sumitomo Citix Co., Ltd.) 20 g and ZrCl in 1000 ml of pure water₂O 8H₂Add pure water to a solution in which 1.696 g of O (zirconium dichloride: manufactured by Wako Pure Chemical Industries, Ltd.) is completely dissolved, and prepare a solution prepared by measuring up to 2000 ml. A 10-fold diluted aqueous ammonia solution of 25% aqueous ammonia (manufactured by Takasugi Pharmaceutical Co., Ltd.) was added dropwise thereto to adjust the pH to 7.0, and a mixture of zirconium hydride and titanium hydroxide was precipitated. Decantation cleaning of this precipitate with pure water so that the conductivity of the supernatant liquid becomes 0.8 mS / m or less is repeated, and when the cleaning is completed when the conductivity reaches 0.702 mS / m, hydroxylation at a concentration of 0.79 wt% is completed. 626g of thing was made. Next, 56 g of 35% hydrogen peroxide solution (manufactured by Taiki Yakuhin Kogyo Co., Ltd.) was added to this containing solution at room temperature, and when the mixture was stirred for 16 hours, a yellowish brown 0.88 wt% zirconium-doped amorphous titanium peroxide solution was added. 680g was obtained.

(Evaluation liquid 2) Zirconium and copper-doped titania (amorphous titanium peroxide) aqueous dispersion: Z18-1000superA (manufactured by Sustainable Technology Co., Ltd.) (adjusted to a concentration of 0.6% by weight), anatase-type titanium peroxide aqueous dispersion (B51 (B51) Sustainable Technology Co., Ltd. (manufactured to a concentration of 0.6% by weight)) and polysilicate ((WM-12 (manufactured by Tama Chemical Industry Co., Ltd.)) in a ratio of 1: 1: 8 (weight ratio). Mix at a ratio, and add 10% by weight of organic silicon compound aqueous dispersion (ZB (manufactured by Sustainable Technology Co., Ltd.)) and 1% by weight of commercially available white sugar to this mixture to evaluate the mixture. 2 was prepared.

(Evaluation liquid 3) Copper-doped titania (amorphous titanium peroxide) aqueous dispersion (Z18-1000nA (manufactured by Sustainable Technology Co., Ltd.) (adjusted to a concentration of 0.6% by weight)) and polysilicate (WM-12 (Tama Chemical Industry Co., Ltd.)) (Manufactured by Co., Ltd.)) was mixed at a ratio of 1: 9 (weight ratio) to prepare Evaluation Solution 3.

(Evaluation liquid 4) Copper-doped titania (amorphous titanium peroxide) aqueous dispersion (Z18-1000nA (manufactured by Sustainable Technology Co., Ltd.) (adjusted to a concentration of 0.6% by weight)) and polysilicate (WM-12 (Tama Chemical Industry Co., Ltd.) (Manufactured by Co., Ltd.)) is mixed at a ratio of 1: 9 (weight ratio), and further, 10% by weight of organosilicon compound aqueous dispersion (ZB (manufactured by Sustainable Technology Co., Ltd.)) is added to this mixture. And 1% by weight of commercially available white sugar was added to prepare an evaluation solution 4.

(Preparation of evaluation board) Evaluation liquids 1 to 4 were applied to a transparent white glass substrate having a thickness of 2.8 mm by the sponge sheet method, and fired at 580 ° C for 30 minutes. The evaluation substrates thus obtained were designated as Examples 1 and 2 and Comparative Examples 1 and 2, respectively. Except for Comparative Example 1, a porous layer having a large number of fine irregularities as shown in FIGS. 7 and 8 was formed on the surface thereof. The thickness of the porous layer was about 150 nm on average. On the other hand, Comparative Example 3 was obtained by firing in the same manner without applying the evaluation liquid.

(Evaluation of optical characteristics) The transmittance and reflectance of visible light were measured under the following conditions using an ultraviolet / visible light photometer V-550DS (JASCO Corporation) for each of Examples 1 and 2 and Comparative Examples 1 to 3. .. Metering mode:% T,% R, Response: Medium, Scanning speed 100 nm / min, Start wavelength 780 nm, End wavelength 380 nm, Data acquisition interval 1.0 nm. The measurement was repeated 4 times, and the average value was taken as the transmittance and reflectance. The results are shown in Tables 1 and 2.

<tables num="1"><img file="JP2009212435A_D0001.tif" /></tables>

From the results in Table 1, Examples 1 and 2 obtained by using the evaluation liquids 1 and 2 containing anatase-type titanium peroxide in advance have excellent transmittance, and in particular, copper and zirconium-doped titanium peroxide are used. It can be seen that Example 2 obtained by using the evaluation solution 2 to be used is excellent. On the other hand, Comparative Example 1 obtained by using the evaluation liquid 3 containing no sugar has the lowest transmittance among the surface-treated substrates. Comparative Example 2 obtained by using the evaluation solution 4 containing sugar has a higher transmittance than Comparative Example 1, but since the evaluation solution does not contain anatase-type titanium peroxide in advance, Examples Transmittance is slightly lower than 1 and 2.

(Evaluation of film thickness dependence) Next, the reflectance-reduced film thickness dependence of light transmittance was evaluated using the following evaluation substrates 1 to 4 and a comparison substrate.

(Evaluation board 1) Evaluation liquid 2 was coated on a glass substrate having a thickness of 1.8 mm and fired to form a porous layer. The film thickness of the porous layer was 80 to 130 nm (interference film color: gray).

(Evaluation board 2) Evaluation liquid 2 was coated on a glass substrate having a thickness of 1.8 mm and fired to form a porous layer. The film thickness of the porous layer was 130 to 180 nm (interference film color: blue).

(Evaluation board 3) Evaluation liquid 2 was coated on a glass substrate having a thickness of 1.8 mm and fired to form a porous layer. The film thickness of the porous layer was 180 to 250 nm (interference film color: yellow).

(Evaluation board 4) Evaluation liquid 2 was coated on a glass substrate having a thickness of 1.8 mm and fired to form a porous layer. The film thickness of the porous layer was 250 to 300 nm (interference film color: purple).

(Comparison board) A glass substrate with a thickness of 1.8 mm.

(Evaluation of optical characteristics) For each of the evaluation substrates 1 to 4 and the comparison substrate, the transmittance of the substrates was measured under the following conditions using an ultraviolet visible near infrared spectrophotometer UV-3100 (Shimadzu Corporation). Measurement mode: spectrum, scan speed: high speed, start wavelength 1500 nm, end wavelength 300 nm, data acquisition interval 2.0 nm. The measurement was repeated 4 times, and the average value of wavelengths of 300 nm to 1200 nm was used as the transmittance. The results are shown in Table 2.

<tables num="2"><img file="JP2009212435A_D0002.tif" /></tables>

From the results in Table 2, it can be seen that the transmittance changes depending on the thickness of the porous layer. The order of improving the transmittance of evaluation boards 1 to 4 is as follows: evaluation board 2&gt; evaluation board 3&gt; evaluation board 1&gt; evaluation board 4

<figref num="1">The figure which shows the outline of an example of the 1st manufacturing method of metal-doped titanium peroxide.</figref><figref num="2">Conceptual diagram showing a positive charge applying mechanism by a complex</figref><figref num="3">Conceptual diagram showing the mechanism by which contaminants are removed from the surface of a positively charged substrate</figref><figref num="4">Conceptual diagram showing an example of a positive charge and negative charge imparting mechanism by a complex</figref><figref num="5">Conceptual diagram showing other examples of positive and negative charge imparting mechanisms by the complex</figref><figref num="6">Conceptual diagram showing the mechanism by which contaminants are removed from the surface of a positively and negatively charged substrate.</figref><figref num="7">Perspective view showing the state of the surface of Examples 1 and 2 and Comparative Example 2 after the heat treatment.</figref><figref num="8">Cross-sectional view showing the state of the surfaces of Examples 1 and 2 and Comparative Example 2 after the heat treatment.</figref>