Reflectance improving agent for base substance and method of manufacturing high reflection type base substance using the same

The present invention relates to a reflectance improver that increases the light reflectance of the substrate, and a method for producing a highly reflective substrate, which comprises performing a surface treatment with the reflectance improver.

In the field of photovoltaic cells that directly convert light energy into electrical energy, for example, amorphous silicon type and polycrystalline type solar cells are known. Currently, opaque solar cells are the mainstream, but amorphous silicon and the like are used. There are also transparent or translucent thin-film type solar cells that use significantly less. There are also types of solar cells that do not use amorphous silicon. For example, CIGS type or dye-sensitized solar cells that use copper-indium-gallium-selenium-based materials, which are non-silicon semiconductor materials. Batteries are known. However, since all of these have low power generation efficiency, efforts are being made to achieve high power generation efficiency for each type.

In addition, among various displays, since the liquid crystal itself is not a light emitter, a backlight using a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) as a light source is provided on the back side of the liquid crystal panel. There is. In order to effectively transmit the light from the backlight to the viewer side, it is necessary to highly efficiently reflect the light emitted in a direction other than the liquid crystal panel and guide it to the liquid crystal panel.

Therefore, various substrates such as optical elements having high reflection efficiency are required. Until now, light-transmissive high-reflectors that utilize the surface of metal compounds centered on Ag and Al have been the mainstream, but if a light-transmitting type substrate with high reflectance can be obtained, While maintaining the see-through characteristics of transparent or translucent solar cells, the light transmitted through the solar cells can be returned to the solar cells to improve power generation efficiency, or the visual characteristics of the display can be maintained while maintaining the backlight. It becomes possible to reduce the energy consumption of the lighting device such as. Further, although a black back sheet is used for the opaque solar cell, it is possible to reduce the light absorption thereof. However, it has been said that the conventional light-transmitting type highly reflective substrate has a high light absorption of the reflective film and has a problem in transparency.

Japanese Patent Application Laid-Open No. 2007-22844 describes that an oxide composite film composed of a composite containing titanium oxide, zirconium oxide and / or hafnium oxide is formed on the surface of the substrate. Optical properties such as film reflectance are not disclosed.<patcit num="1"><text>JP-A-2007-22844</text></patcit>

<p> The present invention has been made in view of the above-mentioned prior art, and in order to suitably produce a highly reflective substrate used for various applications such as a photovoltaic cell and a display, the reflectance of an arbitrary substrate is improved. The purpose is to provide a simple means that can be used.</p>

<p> An object of the present invention is achieved by a reflectance improver containing titanium oxide and zirconium oxide and / or hafnium oxide.</p><p> The titanium oxide is preferably titanium peroxide. Further, the titanium oxide is preferably amorphous type and / or anatase type.</p><p> It is preferable that at least a part of the titanium oxide is metal-doped titanium oxide.</p><p> The reflectance improver of the present invention preferably contains the titanium oxide and the zirconium oxide and / or hafnium oxide in a molar ratio of 1: 0.01 to 1:0.5.</p><p> The reflectance improver of the present invention further (1) Cation; (2) Conductors or dielectrics with a positive charge; (3) A composite of a conductor having a positive charge and a dielectric or a semiconductor. It can contain one or more positively charged substances selected from the group consisting of.</p><p> Further, the reflectance improver of the present invention is further used. (4) Anion; (5) Conductor or dielectric with negative charge; (6) A composite of a conductor having a negative charge and a dielectric or a semiconductor; It can contain one or more negatively charged substances selected from the group consisting of.</p><p> The reflectance improver of the present invention can contain both the positively charged substance and the negatively charged substance.</p><p> The method for producing a highly reflective substrate of the present invention is carried out by applying the reflectance improver to the surface of the substrate, heating and / or exposing it.</p><p> It is preferable that at least a part of the substrate is light transmissive. Moreover, it is preferable that the surface is smooth.</p><p> The highly reflective substrate of the present invention can be obtained by the above-mentioned production method, and can further include a high light transmissive layer or a low light reflective layer. Further, the highly reflective substrate of the present invention preferably has a highly reflective film having an average thickness of 50 nm to 300 nm on the surface.</p><p> The highly reflective substrate can be suitably used as a component of an optical element or a photovoltaic cell.</p>

<p> According to the present invention, it is possible to provide a substrate having improved reflectance by a simple method regardless of the material and shape of the substrate. Therefore, according to the present invention, a highly reflective substrate can be easily and economically produced. The substrate obtained by the present invention can be particularly preferably used as, for example, an optical element for a display that is required to have high reflectivity, or a constituent article of a photovoltaic cell.</p><p> In addition, the substrate of the present invention can exhibit high light transmittance while having high reflectivity. That is, the substrate of the present invention can have high transparency as well as high reflectivity. In particular, when the substrate of the present invention has a high light transmissive layer or a low light reflective layer, this effect is enhanced by the combination of these layers and the high reflectivity of the substrate.</p>

In the present invention, high reflectance is achieved by applying a reflectance improver, which is a composition essential containing titanium oxide and a reflectance improver containing zirconium oxide and / or hafnium oxide, to the surface of a substrate and heat-treating it. Manufacture a sex substrate. That is, the present invention relates to the reflectance improver and a method for producing a highly reflective substrate using the reflectance improver. Therefore, the present invention is also a method for surface-treating a substrate using the reflectance improver. In addition, "improvement" of the reflectance means increasing the reflectance and increasing the reflectance. Further, "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 to be surface-treated according to the present invention, various light-transmitting or light-impermeable substrates can be used. It is preferable that at least a part, preferably all of the substrate is light-transmitting. 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 a light-impermeable substrate made of various metals, ceramics, etc., transparent or translucent glass such as soda lime glass, quartz glass, and heat-resistant glass, or indium tin oxide (ITO). Examples thereof include a light-transmitting substrate made of a metal oxide such as. Moreover, as an organic-based substrate, for example, a substrate made of plastic can be mentioned. More specifically, for example, plastics include polyesters such as polyethylene, polypropylene, boron carbonate, acrylic resin and PET, thermoplastic resins 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 that is light-transmitting at least in part or in whole 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 spherical shape, 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 a smooth surface is preferable.

The reflectance improver used in the present invention is a liquid composition containing at least titanium oxide and zirconium oxide and / or hafnium oxide. In order to achieve the object of the present invention, a layer containing titanium oxide and zirconium and / or hafnium may be finally formed on the surface of the substrate. The layer may be formed by a dry method such as CVD or sputtering, but the economically excellent method using a liquid high reflectance film forming agent will be described below.

Titanium oxide used in the present invention means an oxide of titanium, for example, TiO.₂, TiO₃, TiO, TiO₃/ nH₂Various titanium monoxide such as O, titanium dioxide, titanium peroxide and the like can be mentioned, but titanium peroxide having a peroxo group is preferable. Further, titanium oxide is preferably in the form of fine particles. Titanium oxide may be in any crystalline form of amorphous type, anatase type, brookite type and rutile type, but amorphous type and anatase type are preferable, and anatase type is particularly preferable. It may be a mixture of an amorphous type and anatase type. The substrate treated with the combination of anatase-type titanium oxide with zirconium oxide and / or hafnium oxide does not interfere with the opto-semiconductor properties of titanium oxide. As the titanium oxide, in the present invention, various commercially available crystalline titanium oxide sol solutions may be used.

Further, at least a part of titanium oxide is preferably metal-doped titanium oxide. The metal is preferably at least one of the metal elements selected from the group consisting of gold, silver, platinum, copper, nickel, cobalt, tin and aluminum. As the metal-doped titanium oxide, a mixture of commercially available various crystalline titanium oxide sol solutions and various metal sol solutions may be used.

As the metal-doped titanium oxide, metal-doped titanium peroxide is particularly preferable. As a method for producing the metal-doped titanium dioxide, 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 liquid-dispersed titania solutions may be produced. May be adopted. Then, the metal can be composited with titanium peroxide regardless of the manufacturing stage.

The reflectance improver of the present invention reacts, for example, a solution of a tetravalent titanium compound with a basic solution in the presence of a zirconium compound and / or a hafnium compound to hydroxylate titanium hydroxide and zirconium. It can be prepared by forming a mixture of the compound and / or a hydroxide of hafnium and then peroxoizing the mixture with an oxidizing agent. Specific examples thereof 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. In any of the above steps, at least one of zirconium oxide and hafnium oxide is mixed. Alternatively, the same step as the formation of the amorphous titanium peroxide may be performed on the zirconium compound and / or the hafnium compound to form each peroxide, and then mixed with a predetermined amount of the amorphous titanium peroxide.

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 a basic solution such as aqueous ammonia are mixed in a state where at least one of zirconium oxide and hafnium oxide coexist, and the hydroxide of the metal and the hydroxide of titanium are mixed. To produce a mixture of. If desired, they may be mixed in the presence of at least one of gold, silver, platinum, copper, nickel, cobalt, tin, aluminum and their compounds. 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 metal and titanium hydroxides thus obtained are washed with pure water, cooled to around 5 ° C., and then peroxozylated with hydrogen peroxide solution. This results in titanium peroxide with an amorphous peroxo group containing zirconium oxide and / or hafnium oxide and optionally at least one metal of gold, silver, platinum, copper, nickel, cobalt, tin and aluminum. An aqueous dispersion containing fine particles can be produced.

[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 zirconium oxide and hafnium oxide is mixed in any of the above steps. If desired, at least one of gold, silver, platinum, copper, nickel, cobalt, tin, aluminum and compounds thereof may be mixed.

[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 zirconium oxide and hafnium oxide is mixed in any of the above steps. If desired, at least one of gold, silver, platinum, copper, nickel, cobalt, tin, aluminum and compounds thereof may be mixed.

Needless to say, 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 be used as titanium oxide.

[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. At least one of zirconium oxide and hafnium oxide is mixed either before or after this hydrolysis. If desired, at least one of gold, silver, platinum, copper, nickel, cobalt, tin, aluminum and compounds thereof may be 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.

Further, a hydroxide may be prepared separately from the titanium salt solution by the first to third production methods, the sol-gel method and other metal compounds, mixed with each other, and then an oxidizing agent may be added. , Each may be neutralized separately to form a zirconium peroxide or a hafnium peroxide, which may then be mixed to the required concentration.

Hereinafter, the raw materials used in the present invention will be further described.

(Compound of tetravalent titanium) The tetravalent titanium compound used in the production of 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 titanium oxide.

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 react with the above 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. Although caustic potash and the like can be exemplified, 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 2.0 to 0.5% 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 4.0 to 1.0% by weight.

(Oxidant) As the oxidizing agent for oxidizing the titanium hydroxide formed above, various oxidizing agents can be used without limitation as long as they can form a peroxozide after oxidation, but metal ions are contained in the produced film-forming liquid. Alternatively, hydrogen peroxide that does not generate residues such as acid ions is desirable.

(Metal compound) Examples of the compounds of zirconium, hafnium, and gold, silver, platinum, copper, nickel, cobalt, tin, and aluminum are as follows. Zr compound: Zr (OH)₄, ZrCl₄, ZrO₂, ZrSiO4, ZrCl₂O 8H₂O Hf compound: Hf (OH)₄, HfCl₄, HfO₂Au compounds: AuCl, AuCl₃, AuOH, Au (OH)₂, Au₂O, Au₂O₃Ag compound: AgNO₃, AgF, AgClO₃, AgOH, Ag (NH₃) OH, Ag₂SO₄Pt compound: PtCl₂, PtO, Pt (NH₃) Cl₂, PtO₂, PtCl₄, [Pt (OH)₆〕^2-Cu compound: Cu (OH)₂, Cu (NO)₃)₂, CuSO₄, CuCl₂, Cu (CH)₃COO)₂Ni compound: Ni (OH)₂, NiCl₂Co compound: Co (OH) NO₃, Co (OH)₂, CoSO₄, CoCl₂Sn compound: SnO, SnO₂, SnCl_2、SnCl₄Al compound: Al₂O₃, Al (OH)₂, AlCl₂

The concentration of titanium peroxide in the aqueous dispersion obtained by the first to third production methods (total amount including coexisting zirconium, hafnium, gold, silver, platinum, copper, nickel, cobalt, tin, and aluminum) is 0.05. It is preferably ~ 15% by weight, more preferably 0.1 ~ 5% by weight. Regarding the blending amount of zirconium, hafnium, gold, silver, platinum, copper, nickel, cobalt, tin, and aluminum, the molar ratio of titanium to the metal component is preferably 1: 1 from the present invention, but aqueous dispersion. From the viewpoint of liquid stability, 1: 0.01 to 1: 0.5 is preferable, and 1: 0.02 to 1: 0.1 is more preferable. Metal compounds such as titanium oxide produced by these methods are amorphous or exist as particles having a particle size of 2 to 20 nm.

Examples of commercially available titanium peroxide include amorphous titanium peroxide aqueous dispersion SP185, silica-doped amorphous titanium peroxide aqueous dispersion SPS185, and silver-doped titania aqueous dispersion SP-10 (Sustainable Technology Co., Ltd.). Can be mentioned. Examples of commercially available titanium peroxide containing zirconium oxide include copper and zirconium-doped titania aqueous dispersion Z18-1000SuperA.

The reflectance improver used in the present invention preferably contains amorphous titanium peroxide and / or anatase type titanium peroxide obtained as described above. The anatase-type titanium peroxide may be one in which amorphous titanium peroxide is transferred by heating (typically after coating on the surface of a substrate, which will be described later), but in the case of amorphous titanium peroxide, which is transferred by heating. Amorphous titanium peroxide is preferred. That is, the anatase-type titanium peroxide contained in the reflectance improver 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 titanium oxide in the reflectance improver can be appropriately changed depending on the degree of surface treatment of the substrate, but is typically 0.01 to 10% by weight, preferably 0.1 to 5% by weight. Yes, more preferably 0.2 to 2.0% by weight.

The reflectance improver of the present invention can include an aqueous medium which is water, alcohol or a mixture thereof, or a non-aqueous medium such as an organic solvent. From the viewpoint of solubility, workability, and environmental protection, the reflectance improver of the present invention preferably contains an aqueous medium. The concentration of these media is typically 50-99.9% by weight, preferably 60-99.8% by weight, more preferably 70-99.6% by weight.

The reflectance improver of the present invention is applied to the surface of a substrate and heated. As a result, the reflectance of the surface of the substrate is increased and the light transmission is reduced. The means and method for applying the reflectance improver are not particularly limited, and any means and method can be used. For example, a dip method, a spray method, a slit coater method, a roll coater method, a spin coater method, etc. Any coating method such as the sponge sheet method can be used.

The heating is not particularly limited, but is more preferably room temperature to 800 ° C, even more preferably 100 to 650 ° C, and even more preferably 200 to 550 ° C. When the temperature is less than 200 ° C, it is preferable to expose the substrate by selecting an electromagnetic wave having a wavelength of 400 nm or less, such as ultraviolet rays, according to the type of the substrate. Irradiation time has a relationship of long wavelength&gt; short wavelength. The heating time is also not particularly limited, but is preferably 1 minute to 3 hours, more preferably 1 minute to 1 hour, and even more preferably 1 minute to 30 minutes.

By heating, if titanium peroxide is present in the reflectance improver, titanium peroxide 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, when the reflectance improver of the present invention contains amorphous titanium peroxide, the anatase-type titanium oxide obtained by the process of amorphous titanium peroxide-&gt; amorphous titanium oxide-&gt; anatase-type titanium oxide is on the substrate surface. Exists on. Further, when the anatase-type titanium peroxide is already contained in the reflectance improver, it is changed to anatase-type titanium oxide as it is by heating.

A highly reflective film in which titanium oxide fine particles and zirconium oxide and / or hafnium oxide fine particles coexist is formed on the surface of the heat-treated substrate. This highly reflective film increases the reflectance of the surface of the substrate, and as a result, the light transmittance of the substrate decreases. The average film thickness of the highly reflective film is not particularly limited as long as the reflectance of the substrate is improved, but is preferably 0.05 to 1 μm (50 to 1000 nm), more preferably 100 to 800 nm, and further 120 to 600 nm. More preferably, 150 to 400 nm is particularly preferable.

In the present invention, it is not necessary to perform physical processing such as polishing on the surface itself of the substrate. Further, since the reflectance improver is applied to the surface of the substrate by coating, the surface of the substrate can be treated over a wide range. Further, even a substrate having a complicated shape such as a lens can be easily surface-treated. Therefore, in the present invention, it is possible to improve the reflectance of the substrate by a simple method applicable regardless of the material and shape of the substrate. Thereby, for example, in the case of a light-transmitting substrate, the reflectance thereof can be increased while maintaining the transparency of the substrate. In particular, when the highly reflective film obtained by the present invention is used in combination with a high light transmitting layer or a low light reflecting layer, the transmitted light is increased and the high reflecting property is increased by the high light transmitting layer or the low light reflecting layer. Since the light absorption by the membrane is substantially offset, the transmittance does not decrease as a whole. Therefore, the substrate of the present invention can be suitably used for applications that require not only high reflectivity but also high reflectivity and high transparency.

In addition to the above-mentioned components, the reflectance improver 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 high 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, 1 to tetravalent cations 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 freely move 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, 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. 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 sulfide, polymethoxyphenylene, polyphenylene sulfide, 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, and an iodide ion; an inorganic ion such as a hydroxide ion, a sulfate ion, a nitrate ion, and 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, platinum, and tin; Elements such as sulfur, selenium, tellurium; sulfides such as arsenic sulfide, antimony sulfide, mercury sulfide; clay, glass powder, quartz powder, asbestos, starch, cotton, silk, wool, etc .; Examples thereof include colloids of dyes such as naphthol yellow. Among these, colloids of metals such as gold, silver, platinum and tin 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 improver 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 also electrostatically charged. It repels the surface and prevents it from adhering to the surface of the substrate. Therefore, it is possible to prevent changes 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 pollutants due to negatively charged impurities or 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 reflectance.

The reflectance improver 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, etc. 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.

In the present invention, an intermediate layer may be present between the highly reflective film 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 in which light reflectance is improved or light transmittance is required to be improved. For example, the back panel of a photovoltaic cell such as a solar cell, and the back sheet: the back panel of various displays such as a liquid crystal display, a plasma display, an organic EL display, and a CRT television; an optical element such as a lens; a building member such as a window glass; , Can be used for various light receivers, light emitters, projectors, polarizing glasses, optical glasses, and the like. In particular, when it is used for the back panel of a translucent or transparent photovoltaic cell such as a solar cell used outdoors and an opaque black backsheet, it contributes to the improvement of power generation efficiency due to its high reflectivity and is semi-transparent. In the case of a transparent type or a transparent type (see-through type), the commercial characteristics of the solar cell can be utilized due to its high transparency.

Further, when the substrate is surface-treated with a reflection improver containing a positively charged substance, a negatively charged substance or a mixture thereof, electrostatic repulsion on the surface of the substrate is combined with the effect of preventing the formation of water droplets due to the hydrophilicity of the surface of the substrate. Since the adhesion of contaminants is avoided or reduced over a long period of time, the high reflectivity of the substrate can be maintained over time.

The reflectance improver of the present invention can exhibit even higher reflectance characteristics when used in combination with a surface having high transparency or low reflectance. For example, by imparting the highly reflective film obtained by the present invention in combination with a highly transparent layer or a low reflective layer to a substrate, transparency can be maintained while further improving light reflectivity.

The method for forming a highly permeable or low-reflectivity surface is not particularly limited, but as a reflectance reducing agent, a pyrolytic organic compound, and titanium oxide and / or an organosilicon compound and / or an inorganic silicon A reflectance reducing agent, which is a composition essentially containing a compound, can be used. As a commercially available reflectance reducing agent, there is Titania High Coat ZT: ZT16-50A (manufactured by Sustainable Technology Co., Ltd.).

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 monosaccharides 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.

Since the water-soluble organic polymer can function as a solubilizing agent for sugar or sugar alcohol, it is preferably blended with sugar or sugar alcohol. As a result, 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 10% by weight. It is more preferably 1.0 to 5.0% by weight.

Examples of the organosilicon compound 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, and is not limited to these, and specifically, all of polyethylene oxide, polypropylene oxide, polytetramethylene oxide, and polyethylene oxide-polypropylene oxide block are used. Examples thereof include molecular structures such as polymers, polyethylene polytetramethylene glycol copolymers, and polytetramethylene glycol-polypropylene oxide copolymers. 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 include silica (silicon dioxide), silicon nitride, silicon carbide, and silane, 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.), WM-12 (Tama Chemical Industry Co., Ltd.), and silica sol 51 (Colcoat Co., Ltd.) as polysilicates. ) 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 98% by weight, preferably 0.1 to 90% by weight. , More preferably 10 to 80% by weight.

The reflectance reducing agent preferably contains an aqueous medium such as 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 reflectance reducing agent is applied to the surface of the substrate and heated. As a result, the reflectance of the surface of the substrate is reduced and the light transmittance is improved. The means and method for applying the reflectance reducing agent are not particularly limited, and any means and method can be used. For example, a dip method, a spray method, a roll coater method, a spin coater method, a sponge sheet method, etc. Any coating method can be used.

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.

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. Therefore, it can be said that the porous layer is a low-reflection film. The average thickness of the porous layer is not particularly limited as long as the transmittance of the substrate is improved, but is preferably 0.05 to 0.3 μm (50 to 300 nm), more preferably 80 to 250 nm, and further 100 to 250 nm. More preferably, 120 to 200 nm is particularly preferable.

The surface of the porous layer has a maximum height (R)._max) It is preferable to have a surface roughness of 50 nm or less, and the maximum height is more preferably 30 nm or less. However, the porous layer is formed from the surface of the substrate, and the depth of the pores may be the thickness of the layer or the thickness of the surface layer. The presence of such a large number of fine irregularities reduces the reflectance on the surface of the substrate, and as a result, improves the light transmittance of the substrate. The particle size of titanium oxide contained in the porous layer is preferably 1 nm to 100 nm, more preferably 1 nm to 50 nm, and even more preferably 1 nm to 20 nm.

Here, instead of forming fine irregularities on the surface of the substrate itself by etching or the like, fine irregularities are formed on the surface of the substrate by forming a thin porous layer on the surface, so that the surface of the substrate itself is fine. No processing 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.

By using the reflectance improver of the present invention in combination with the surface of various high-transparency layers or low-reflection layers, the reflectance of the substrate is improved by a simple method applicable regardless of the material and shape of the substrate. This makes it possible to provide a highly reflective substrate having improved optical properties, particularly a highly reflective and transparent substrate.

FIG. 4 is a schematic cross-sectional view showing an aspect in which the reflectance improver of the present invention is used in combination with a highly transparent or low reflective layer.

In the embodiment shown in FIG. 4, 1 represents a light-transmitting substrate, 2 represents a low-reflection film formed by the above-mentioned reflectance reducing agent, and 3 represents a high-reflection film formed by the reflectance improving agent of the present invention. Represents a sex membrane.

In the example shown in FIG. 4A, the highly reflective film 3 is formed on the A-side surface of the light-transmitting substrate 1, and the low-reflective film 2 is formed on the B-side surface.

In the example shown in FIG. 4 (b), the low-reflection film 2 is formed on the A-side surface of the light-transmitting substrate 1, and the high-reflection film 3 is further formed on the surface of the low-reflection film 2. There is.

In the example shown in FIG. 4 (c), the low-reflection film 2 is formed on both the A-side and the B-side of the light-transmitting substrate 1, and the high-reflection film 3 is further formed on the B-side surface. ing.

The three types of substrates shown in FIGS. 4 (a), (b), and (c) can be highly reflective and transparent, and this effect can be obtained even when the incident light comes from either side of A or B, or from both sides. Is demonstrated.

FIG. 5 is a schematic cross-sectional view showing another aspect in which the reflectance improver of the present invention and the above-mentioned reflectance reducing agent are used in combination.

The example shown in FIG. 5 shows a photovoltaic cell having two see-through type (semi-transparent type) power generators 4 and 4', and a low-reflective film 2 is formed on the A-side surface of the power generator 4 to generate power. A highly reflective film 3a is formed on the B-side surface of the body 4'. In addition, the highly reflective film 3b also exists between the generator 4 and the generator 4'. In this example, the light from the A side reaches the generator 4 well due to the low-reflection film 2, and power is generated. A part of the light that has passed through the generator 4 is reflected by the highly reflective film 3b and reaches the generator 4 again. As a result, the power generation efficiency of the power generator 4 is improved. On the other hand, the light that has passed through the generator 4 reaches the generator 4'and generates electricity. Then, the light that has passed through the generator 4'is reflected by the highly reflective film 3a and reaches the generator 4'again. Then, the light that has passed through the generator 4'again is reflected by the highly reflective film 3b and reaches the generator 4'again. This is repeated, and light is delivered to the generator 4'from both the highly reflective films 3a and 3b. As a result, the power generation efficiency of the generator 4'is also improved.

In the case of this type, the wavelength band of high reflection can be selected by adjusting the film thickness of the highly reflective film 3, so that more power can be generated by combining with the power generation wavelength band of the generators 4 and 4'. Efficiency is improved. For example, the peak wavelength band of light can be adjusted to the low wavelength side when the film thickness is thin (80 nm to 180 nm) and to the high wavelength side when the film thickness is thick (180 nm to 280 nm).

FIG. 6 is a schematic cross-sectional view showing another aspect of using the reflectance improver of the present invention.

In the example shown in FIG. 6, the highly reflective film 3 formed by the present invention is provided on one surface of the back sheet 1', and the power generator 4 is further arranged on the surface of the highly reflective film 3. There is. In this example, the highly reflective film 3 enhances the reflectivity of the backsheet 1', which improves the power generation efficiency of the generator 4.

As described above, the power generation efficiency of the photovoltaic cell is improved by appropriately treating the power generator by using the reflectance improver of the present invention and, if necessary, the above-mentioned reflectance reducer in combination. Can be done.

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

(Example 1) Zirconium-doped amorphous titanium peroxide aqueous dispersion 50% titanium tetrachloride solution (manufactured by Sumitomo Corporation) 20 g and ZrCl in 1,000 ml of pure water₂O 8H₂Prepare a solution prepared by adding pure water to a solution in which 1.696 g of O (zirconium trichloride: manufactured by Wako Pure Chemical Industries, Ltd.) is completely dissolved, and measuring up to 2,000 ml. Ammonia water obtained by diluting 25% aqueous ammonia (manufactured by Takasugi Pharmaceutical Co., Ltd.) 10 times 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 becomes 0.8 mS / m or less is repeated, and when the cleaning is completed when the conductivity reaches 0.702 mS / m, a hydroxide having a concentration of 0.79% is obtained. Was produced in 626g. Next, 56 g of 35% hydrogen peroxide solution (manufactured by Taiki Yakuhin Kogyo Co., Ltd.) was added to this dispersion at room temperature, and the mixture was stirred for 16 hours. 680 g of the coating liquid of the present invention containing titanium peroxide was obtained. The concentration was 0.4w%.

(Example 2) Hafnium-doped amorphous titanium peroxide aqueous dispersion 50% titanium tetrachloride solution (manufactured by Sumitomo Corporation) 20 g and HfCl in 1,000 ml of pure water₄(Hafnium chloride: manufactured by Mitsuwa Chemical Co., Ltd.) Pure water is added to a solution in which 1.686 g is completely dissolved, and a solution made up to 2,000 ml is prepared. Ammonia water obtained by diluting 25% aqueous ammonia (manufactured by Takasugi Pharmaceutical Co., Ltd.) 10 times was added dropwise thereto to adjust the pH to 7.0, and a mixture of hafnium hydroxide and titanium hydroxide was precipitated. Decantation cleaning of this precipitate with pure water so that the conductivity of the supernatant becomes 0.8 mS / m or less is repeated, and when the cleaning is completed when the conductivity reaches 0.772 mS / m, mixed hydroxylation at a concentration of 0.90% is completed. A product of 491 g was produced. Next, 112 g of 35% hydrogen peroxide solution (manufactured by Taiki Yakuhin Kogyo Co., Ltd.) was added to this dispersion at room temperature, and the mixture was stirred for 16 hours. 600 g of the coating liquid of the present invention containing titanium was obtained. The concentration was 0.4w%.

(Example 3) Zirconium + hafnium-doped amorphous titanium peroxide aqueous dispersion Dispersion of Example 1: Dispersion of Example 3: Amorphous titanium peroxide (0.4w%) (SPS170: Sustainable Technology Co., Ltd.) = 1: 1: 1 and zirconium + hafnium-doped amorphous A type titanium peroxide aqueous dispersion was used. The concentration was 0.4 wt%.

(Example 4) Zirconium + hafnium-doped amorphous type + anatase type titanium peroxide aqueous dispersion The aqueous dispersion of Example 3 and anatase-type titanium peroxide (SAS170: manufactured by Sustainable Technology Co., Ltd.) are mixed 1: 1 to form a zirconium + hafnium-doped amorphous type + anatase-type titanium peroxide aqueous dispersion. did. The concentration was 0.4 wt%.

(Example 5) Zirconium + positively charged metal-doped amorphous titanium peroxide aqueous dispersion Dispersion of Example 1: Positively charged titanium water peroxide dispersion (Z18-1000A: manufactured by Sustainable Technology Co., Ltd.) = 8: 2 mixed, zirconium + positively charged metal-doped amorphous titanium peroxide water It was used as a dispersion. The concentration was 0.4 wt%.

(Example 6) Zirconium + negatively charged metal-doped amorphous titanium peroxide aqueous dispersion Dispersion of Example 1: Negatively charged titanium water peroxide dispersion (P00138: Sustainable Technology Co., Ltd.) = 1: 1 mixed and zirconium + negatively charged metal-doped amorphous titanium peroxide aqueous dispersion And said. The concentration was 0.4 wt%.

(Example 7) Zirconium + amphoteric charge metal-doped amorphous titanium peroxide aqueous dispersion Dispersion of Example 5: Dispersion of Example 6 = 1: 1 was mixed to give a zirconium + positively charged metal + negatively charged metal-doped amorphous titanium peroxide aqueous dispersion. The concentration was 0.4 wt%.

(Comparative Example 1) Amorphous titanium peroxide aqueous dispersion An amorphous titanium peroxide aqueous dispersion (SPS140: manufactured by Sustainable Technology Co., Ltd.) without metal doping was used as an amorphous titanium peroxide aqueous dispersion.

(Preparation of evaluation board) Blue float glass for building materials (thickness 3 mm, transparent) was prepared as a substrate, and the dispersions of Examples 1 to 7 and Comparative Example 1 were applied at 19 g / m.²In the amount of (wet state), it was applied to one side of the substrate using a commercially available sponge sheet, dried, and then kept at 200 ° C. for 30 minutes in a heating tank to be fixed by heating. In this way, the following evaluation substrates 1 to 7 and comparative evaluation substrate 1 were prepared. The film thickness was approximately 150 nm to 180 nm. The float glass itself without surface treatment was used as the comparative evaluation substrate 2.

Evaluation board 1: Using Example 1 Evaluation board 2: The one using Example 2 Evaluation board 3: The one using Example 3 Evaluation board 4: Using Example 4 Evaluation board 5: Using Example 5 Evaluation board 6: The one using Example 6 Evaluation board 7: Using Example 7 Comparative evaluation board 1: Using Comparative Example 1 Comparative evaluation board 2: No surface treatment

(Evaluation 1) The visible light reflectance and transmittance of the evaluation substrates 1 to 7 and the comparative evaluation substrates 1 to 2 were measured using an ultraviolet-visible spectrophotometer (ISV-469V550: manufactured by JASCO Corporation). Specifically, each substrate was irradiated with light from the surface-treated side, the reflectance and transmittance in the visible light wavelength band (780 nm to 380 nm) were measured, and the average was calculated. The results are shown in Table 1.

<tables num="1"><img file="JP2010113158A_D0001.tif" /></tables>

When the non-surface treatment side of the substrate was measured in the same manner, it was almost the same as that of the comparative evaluation substrate 2.

From the results in Table 1, zirconium and / or hafnium, as compared to the substrate surface-treated with amorphous titanium peroxide (comparative evaluation substrate 1) and the substrate not surface-treated (comparative evaluation substrate 2). In addition, it can be seen that the substrates (evaluation substrates 1 to 7) provided with the layer made of titanium peroxide doped with various other metals have high reflectivity of incident light. Moreover, the evaluation substrate 1 also has a relatively high transmittance, and it can be seen that the evaluation substrate 1 maintains high transparency.

(Reference example 1) Highly permeable or lowly reflective titania aqueous dispersion Titania water dispersion (active ingredient concentration 0.6w% (ZT16-50A: Sustainable Technology Co., Ltd.)) and organosilicon aqueous dispersion (ZB: Sustainable Technology Co., Ltd.) at 10: 2. The mixture was mixed in a ratio to obtain a highly permeable or low-reflectivity-imparting titania aqueous dispersion.

(Preparation of evaluation board) As substrates, blue float glass for building materials (thickness 3 mm, transparent) and polycarbonate sheet (thickness 2 mm, transparent, manufactured by Takiron Co., Ltd.) were prepared. 16 g / m of the dispersion liquid of Reference Example 1 on one surface of the glass substrate²It was applied in an amount of (wet state), applied using a commercially available sponge sheet, dried, and then maintained at 200 ° C. for 30 minutes in a heating tank for heating and fixing. 19 g / m of the dispersion of Example 3 on the other surface²Similarly, the coating, drying, and heating were performed in the amount of (wet state) to obtain an evaluation substrate 8 having a cross-sectional structure shown in FIG. 4 (a). 16 g / m of the dispersion liquid of Reference Example 1 on one surface of the glass substrate²It was applied in an amount of (wet state), applied using a commercially available sponge sheet, dried, and then maintained at 200 ° C. for 30 minutes in a heating tank to be fixed by heating. Further, 19 g / m of the dispersion liquid of Example 3 was added to the surface thereof.²The same amount of (wet state) was applied, dried, and heated to obtain an evaluation substrate (glass) 9 having a cross-sectional structure shown in FIG. 4 (b). The same operation was performed on the polycarbonate substrate to obtain an evaluation substrate (PC) 9. 16 g / m of the dispersion liquid of Reference Example 1 on both sides of the glass substrate²It was applied in an amount of (wet state), applied using a commercially available sponge sheet, dried, and then maintained at 200 ° C. for 30 minutes in a heating tank to be fixed by heating. Further, 19 g / m of the dispersion liquid of Example 3 was applied to one surface.²The evaluation substrate 10 having the cross-sectional structure shown in FIG. 4 (c) was obtained by applying, drying and heating in the same manner in the amount of (wet state). The film thickness of the high-transparency or low-reflection layer obtained by the dispersion liquid of Reference Example 1 is approximately 100 to 120 nm, and the film thickness of the high-reflection layer obtained by the dispersion liquid of Example 3 is approximately 150 nm to 180 nm. there were. The glass substrate and the polycarbonate substrate itself, which were not surface-treated, were designated as comparative evaluation substrates 3 and 4, respectively.

(Evaluation 2) The visible light reflectance and transmittance of the evaluation substrates 8 to 10 and the comparative evaluation substrates 3 to 4 were measured using an ultraviolet-visible spectrophotometer (ISV-469V550: manufactured by JASCO Corporation). Specifically, each substrate was irradiated with light from the surface-treated side, the reflectance and transmittance in the visible light wavelength band (780 nm to 380 nm) were measured, and the average was calculated. The results are shown in Table 2. In Table 2, the values in parentheses indicate the values measured for the incident light from the B side shown in FIG. The values in parentheses indicate the values measured for the incident light from the A side shown in FIG.

<tables num="2"><img file="JP2010113158A_D0002.tif" /></tables>

From the results in Table 2, there is no difference in the reflectance improvement tendency regardless of whether the incident light reaches the substrate from either the A side or the B side. Therefore, both sides of the evaluation boards 8 to 10 can be used as highly reflective surfaces. In particular, the evaluation substrate 9 corresponding to the cross-sectional structure of FIG. 4 (b) had the highest reflectance, and specifically, the reflectance was higher in the order of Example 9&gt; Example 10&gt; Example 8.

The wavelength dependence of the transmittance and reflectance of the comparative evaluation substrate 3 and the comparative evaluation substrate 4 for each of the evaluation substrate (glass) 9 and the evaluation substrate (PC) 9 is shown in FIGS. 7 and 8. From these results, it can be seen that the evaluation substrate 9 exhibits high reflectance especially in the visible light region (380 nm to 780 nm).

<figref num="1">The figure which shows the outline of an example of the 1st manufacturing method of titanium oxide.</figref><figref num="2">Conceptual diagram showing the mechanism of positive charge application by the 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">Schematic cross-sectional view showing one embodiment in which the reflectance improver of the present invention and the above-mentioned reflectance reducing agent are used in combination.</figref><figref num="5">Schematic cross-sectional view showing another aspect in which the reflectance improver of the present invention and the above-mentioned reflectance reducing agent are used in combination.</figref><figref num="6">Schematic cross-sectional view showing another aspect of using the reflectance improver of the present invention.</figref><figref num="7">Diagram showing the wavelength dependence of the transmittance and reflectance of the evaluation substrate (glass) 9 and the comparative evaluation substrate 3.</figref><figref num="8">Diagram showing the wavelength dependence of the transmittance and reflectance of the evaluation board (PC) 9 and the comparative evaluation board 4.</figref>

Code description

1 ... Base, 1'... Backsheet, 2 ... Low reflective film, 3 ... Highly reflective film, 4, 4'... Power generator