JP2014019822A - Resin composition for solar cell encapsulation material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition for solar cell encapsulation material capable of improving the initial conversion efficiency of a solar cell module by reflecting the light that is not received by a power generation element, by a rear surface encapsulation material and re-receiving it by the power generation element, where as there is no decrease in the initial adhesion strength with an inorganic material member which is in contact with the encapsulation material, delamination of the adhesion surface over time is unlikely to occur and maintaining the high conversion efficiency becomes possible, and also to provide a solar cell encapsulation material.SOLUTION: Such a resin composition for solar cell encapsulation material comprises titanium dioxide with an average primary particle size of 0.15 to 0.45 μm (A), and an ethylene-based resin (B). The titanium dioxide (A) has a surface coating layer that is formed from 2 to 7 pts.wt of metal oxide comprising oxides of silicon (C) relative to 100 pts.wt of the titanium dioxide before surface coating.

Description

  The present invention relates to a resin composition for a solar cell encapsulant.

In recent years, the photovoltaic power generation system has been gaining attention all over the world as a clean and sustainable energy system from the viewpoint of global warming countermeasures and replacement of fossil fuels that are feared to be depleted. Therefore, the market size of solar cells is increasing year by year. In addition, the photovoltaic power generation system has been attracting attention from the viewpoints of the recent safety concerns of nuclear power generation and private power generation in an emergency. However, reducing the power generation cost is the biggest challenge for further expansion of the photovoltaic power generation system. In recent years, the power generation cost of photovoltaic power generation has been greatly reduced due to technological innovation. However, the power generation cost of solar power generation at present is still higher than other energy sources, and technical innovations such as higher efficiency and longer life of solar cell modules are required.
Currently, the mainstream photovoltaic power generation is composed of silicon-based solar cell modules such as crystalline silicon and amorphous silicon, and compound semiconductor-based solar cell modules such as CdTe and CIGS and peripheral devices. Moreover, these solar cell modules are of a super straight structure sandwiched between sealing elements from both sides of the power generation element, such as transparent substrate / surface sealing material / power generation element / back surface sealing material / back surface protection member, or transparent substrate / Power generation element / sealing material / back surface protection member A power generation element formed on the surface of the substrate is laminated with a sealing material and a back surface protection member. In general, on the back side of the light receiving surface of a power generation element using a crystalline silicon cell, an aluminum paste is printed on the entire surface of a silicon wafer in order to efficiently extract generated power. In addition, a heat-strengthened white plate glass is usually used for the transparent substrate, and a weather-resistant resin sheet is used for the back surface protection member.
However, in recent years, from the viewpoint of weather resistance, a transparent substrate is often used for the back surface protection member.

  In order to increase the efficiency of the solar cell module, in addition to improving the power generation efficiency of the power generation element itself, it is considered to increase the amount of light received by the power generation element. Therefore, Patent Document 1 discloses that titanium dioxide is added to the back surface protection sheet to reflect incident light and increase the amount of light received by the power generation element. Patent Document 2 discloses that titanium dioxide is blended with a solar cell sealing material to reflect incident light and increase the amount of light received by a power generation element.

JP 2007-208179 A JP 2008-103471 A

  However, in recent years, from the viewpoint of improving the durability of the solar cell module, the use of a glass protective plate without using a resin-made back protective sheet has increased, so that the back protective sheet of Patent Document 1 cannot be used. There is a case.

  Moreover, although a solar cell sealing material seals by closely_contact | adhering with the glass surface of a solar cell module, the sealing material of patent document 2 originates in containing titanium dioxide, and adhesiveness with a glass surface or Adhesiveness with the aluminum back electrode of the power generation element is lowered. This usually involves adding a silane coupling agent having a functional device that reacts with organic materials and inorganic materials in order to increase the adhesion between the transparent substrate and the aluminum back electrode and the sealing material. The compounded titanium oxide also reacts with the functional group of the silane coupling agent. Therefore, there is a problem that not only the initial adhesive strength is lowered but also the sealing material is peeled off from the glass surface when used outdoors for a long time.

  In the present invention, since light can be efficiently reflected, the amount of light received by the power generation element is increased, so that the initial conversion efficiency is improved, and the adhesiveness between the sealing material and the inorganic material member in contact with the sealing material is good. Therefore, it aims at providing the resin composition for solar cell sealing materials which can manufacture the solar cell sealing material which suppresses the fall of initial stage adhesive strength, and also does not produce peeling even if it uses for a long period of time.

  The present invention relates to a solar cell encapsulating structure comprising titanium dioxide having an average primary particle size of 0.15 to 0.45 μm having a surface coating layer formed of a metal oxide containing a silicon oxide, and an ethylene-based resin. It is a resin composition for materials.

According to the present invention having the above configuration, the use of titanium dioxide having an average primary particle size of 0.15 to 0.45 μm allows reflection of wavelengths in the near-infrared region, which contributes to power generation, so that the initial conversion efficiency is high. Increase. Compared with the case where the titanium dioxide is blended in the back surface protective sheet, this reflection can contribute to the improvement of conversion efficiency because the sealing material has a short distance to the power generation element and the reflected light is not easily attenuated.
Usually, a silane coupling agent is blended in the sealing material in order to improve adhesion with glass or an inorganic material member adjacent to the sealing material such as the power generation element aluminum back electrode. This silane coupling agent is hydrolyzed by moisture in the atmosphere to form silanol, and then moves to the interface with the sealing material by hydrogen bonding with the surface of the inorganic material, and then is subjected to strong chemical reaction by dehydration condensation reaction. By forming the bond, the glass surface and the sealing material are in close contact with each other. However, conventionally, this silane coupling agent has been bonded to the surface functional group of titanium dioxide by hydrogen bonding, contrary to the original intention, and the adhesion to the surface of the inorganic material has been lowered. However, in the present invention, since the surface of titanium dioxide was coated with a metal oxide, the charge and polarity changed, and the silanol group of the silane coupling agent became difficult to form a hydrogen bond with the titanium dioxide surface. Good adhesion can be realized by easily forming a hydrogen bond with the surface.

  According to the present invention, since the amount of light received by the power generation element can be increased, the initial conversion efficiency is improved, and furthermore, the adhesion between the sealing material and the inorganic material member in contact with the sealing material is good. In addition, it was possible to provide a resin composition for a solar cell encapsulant and a solar cell encapsulant that hardly inhibit peeling even when used for a long time.

It is a schematic diagram which shows an example of sectional drawing of a solar cell module. It is a schematic diagram which shows an example of sectional drawing of a solar cell module. It is sectional drawing for showing the layer structure of the sample for adhesive evaluation. It is sectional drawing for showing the sample for adhesive evaluation.

  First, the present invention will be described in detail. In the present specification, the description of “any number A or more and any number B or less” and “any number A to any number B” is a range larger than the number A and the number A, and the number B And a range smaller than the number B.

  Titanium dioxide blended in the resin composition for solar cell encapsulant of the present invention has a property of reflecting visible light and infrared light contained in sunlight. Although the spectral sensitivity differs depending on the type, the solar cell has a sensitivity peak from the visible light to the near-infrared light region. Spectral sensitivity refers to a characteristic that expresses the efficiency of power generation in a solar cell for each wavelength. Therefore, the light that has not been received by the power generation element is reflected by the titanium dioxide mixed in the sealing material, so that the light reception to the power generation element becomes possible and the conversion efficiency is improved. This effect contributes more to power generation because the amount of light is less attenuated than when reflected by the back surface protection sheet. Moreover, the titanium dioxide used for this invention can suppress the fall of the adhesiveness of a sealing material and the inorganic material member which a sealing material contacts by coat | covering the surface with a specific inorganic substance. In order to increase the adhesion between the inorganic material and the sealing material, a silane coupling agent is usually used. This is because the silane coupling agent has a functional group that binds to an organic material and an inorganic material in the molecule, and acts as an intermediary between the organic material and the inorganic material. This silane coupling agent is hydrolyzed by moisture to become silanol, and subsequently moves to the substrate surface by hydrogen bonding with the inorganic surface, and then forms a strong chemical bond by dehydration condensation reaction. In parallel with this reaction, silanol groups are condensed with each other to produce a siloxane oligomer. In general, chemical bonding with a silane coupling agent is very likely to occur on the glass surface or aluminum back electrode, which is an inorganic material member, and titanium dioxide is known to be less reactive than the inorganic material. ing. However, in ethylene-based resins, the reactivity of the silane coupling agent is greatly increased, so the reaction occurs not only on the glass surface of the transparent substrate and the aluminum back electrode, but also on the titanium dioxide surface. Adhesive strength with a sealing material falls. In the present invention, a surprising effect has been found in that the transition of the silane coupling agent to titanium dioxide is suppressed by coating titanium dioxide with oxides of aluminum and silicon having higher reactivity. This is presumably because the surface charge and polarity changed depending on the type of coating, and hydrogen bonding with the silanol group of the silane coupling agent was less likely to occur. As a result, chemical bonding between the transparent substrate and the silane coupling agent occurs preferentially, and a decrease in the initial adhesive strength is suppressed. Therefore, peeling of the adhesive surface over time is unlikely to occur, and high conversion efficiency can be maintained.

  The resin composition for a solar cell encapsulant of the present invention is a titanium dioxide having an average primary particle diameter of 0.15 to 0.45 μm having a surface coating layer formed of a metal oxide (C) containing a silicon oxide. (A) and an ethylene-type resin (B) are included. And titanium dioxide (A) has a surface coating layer formed with 2 to 7 parts by weight of metal oxide (C) containing silicon oxide with respect to 100 parts by weight of titanium dioxide before surface coating. Is preferred. It is preferable to form a solar cell encapsulant (hereinafter also referred to as encapsulant) using this solar cell encapsulant resin composition.

  In the present invention, the titanium dioxide (A) preferably has an average primary particle size of 0.15 to 0.45 μm. And from a viewpoint of light scattering, 0.15-0.35 micrometer is more preferable. When the average primary particle diameter is less than 0.15 μm or exceeds 0.45 μm, the light scattering efficiency in the spectral sensitivity region of the solar cell power generation element is lowered, and the contribution to the conversion efficiency may be lowered. Further, as the crystal form of titanium dioxide, rutile type, anatase type and brookite type can be used, but rutile type is preferable. Since the rutile type has a higher refractive index and higher light scattering efficiency than other types, it can further contribute to the conversion efficiency. The average primary particle diameter of titanium dioxide is an average of particle diameters (for example, 20 to 50 particles) that can be observed from an enlarged image of a scanning electron microscope.

Moreover, it is important that titanium dioxide (A) has a surface coating layer formed of a metal oxide (C) containing an oxide of silicon. The presence of this surface coating layer changes the surface charge state of titanium dioxide and makes it difficult for hydrogen bonding to occur with the silane coupling agent. Thereby, the silane coupling agent easily moves to the interface between the inorganic material such as glass and the sealing material. As a result, the adhesion between the sealing material and the inorganic material member in contact with the sealing material is improved. From the viewpoint of the surface charge state, the silicon oxide is preferably contained in an amount of 1 to 5 parts by weight with respect to 100 parts by weight of titanium dioxide before surface coating. The silicon oxide may be a silicon hydrated oxide, and silica or hydrated silica (SiO ₂ .nH ₂ O) is preferable.

The metal oxide (C) preferably further contains an oxide of aluminum. By coating titanium dioxide with aluminum oxide, the lipophilicity is increased and the dispersibility in the ethylene-based resin is improved. The aluminum oxide is preferably 1 to 4 parts by weight with respect to 100 parts by weight of titanium dioxide before surface coating. The aluminum oxide may be an aluminum hydrated oxide, preferably hydrated alumina (Al ₂ O ₃ .nH ₂ O). The metal oxide (C) may be surface-coated with an oxide of zirconium in addition to an oxide of silicon and an oxide of aluminum.

  A method for forming the surface coating layer containing the metal oxide (C) on the titanium dioxide surface will be described.

  A known method can be used as a method of coating the titanium dioxide particles with the metal oxide (C). For example, when coating with silicon oxide, an aqueous solution of silicon oxide is added to an aqueous slurry in which titanium dioxide particles are dispersed, and the pH is adjusted to 4 to 9 using an aqueous solution of an acidic compound or a basic compound. A surface coating layer can be formed. Then, you may perform filtration, washing | cleaning, and drying as needed. As the acidic oxide used for adjusting the pH, inorganic acids such as sulfuric acid and hydrochloric acid, or organic acids such as acetic acid and formic acid can be used. Moreover, as a basic compound, well-known compounds, such as sodium hydroxide, potassium hydroxide, and ammonia, can be used. The non-volatile content of titanium dioxide particles in the aqueous slurry is preferably 50 to 800 g / l, more preferably 100 to 600 g / l. A coating layer having a uniform thickness can be easily obtained by setting the concentration to a predetermined nonvolatile content.

  Examples of the silicon oxide include water-soluble alkali metal silicates such as sodium silicate.

  When coating with aluminum oxide or zirconium oxide, the same method as for coating with silicon oxide can be used. The coating using these metal oxides may be coated with a mixture with silicon oxide, or may be laminated and coated with a plurality of layers. Moreover, although these coating | coated orders are not restrict | limited, it is preferable from a viewpoint of the surface charge state of titanium dioxide to coat | cover so that an aluminum oxide may become an outermost layer. Furthermore, in the manufacturing process of titanium dioxide, operations such as dehydration, drying, and pulverization are easy, which is preferable.

  Examples of the aluminum oxide include sodium aluminate, aluminum sulfate, and aluminum nitrate, aluminum chloride, alumina, hydrous alumina, and the like. Examples of the zirconium oxide include zirconium sulfate, zirconium nitrate, and zirconium chloride.

Titanium dioxide (A) preferably forms a coating layer using an organic substance after forming a surface coating layer containing a metal oxide (C).
Examples of organic substances include polyhydric alcohols, organosilicon compounds, amines, amino acids, fatty acids, carboxylates, metal soaps, and waxes. Of these, polyhydric alcohols and organosilicon compounds are preferred. One or more organic substances can be used. The surface coating amount using an organic substance is preferably 0.1 to 3 parts by weight, and more preferably 0.1 to 1.5 parts by weight with respect to 100 parts by weight of titanium dioxide before treatment.

  Specific examples of the polyhydric alcohol that can be used in the present invention include trimethylol ethane, trimethylol propane, ditrimethylol propane, trimethylol propane ethoxylate, pentaerythritol, and the like, and trimethylol propane, trimethylol ethane preferable.

  Examples of the organosilicon compound that can be used in the present invention include organosilane, organopolysiloxane, and organosilazane.

  Specifically, as the organosilane, aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxy Silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ- (methacryloyloxypropyl) trimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyl Triethoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, hexylmethyldimethoxysilane, hexylmethyldiethoxysilane, cyclohexyl Dimethyldiethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, phenyltriethoxysilane, trifluoropropyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, or their hydrolysis products. It is done.

  Organopolysiloxanes include dimethylpolysiloxane, methylhydrogen polysiloxane, methylmethoxypolysiloxane, methylphenylpolysiloxane, dimethylpolysiloxanediol, dimethylpolysiloxane dihydrogen, side chain or both-end amino-modified polysiloxane, side chain or both. End- or single-end epoxy-modified polysiloxane, double-end or single-end methacryl-modified polysiloxane, side-chain or double-end carboxyl-modified polysiloxane, side-chain or double-end or single-end carbinol-modified polysiloxane, double-end phenol-modified polysiloxane, Side-chain or both-end mercapto-modified polysiloxane, both-end or side-chain polyether-modified polysiloxane, side-chain alkyl-modified polysiloxane, side-chain methylstyryl-modified polysiloxane, Chain higher carboxylic acid ester-modified polysiloxane, a side-chain fluoroalkyl-modified polysiloxanes, side-chain alkyl-carbinol-modified polysiloxane, the side chain amino both end carbinol-modified polysiloxanes or copolymers thereof, and the like.

  Examples of organosilazanes include hexamethylsilazane and hexamethylcyclotrisilazane.

  Formation of the coating layer using an organic substance is carried out by solid-liquid separation of titanium dioxide whose surface is coated with a metal oxide from an aqueous slurry, drying it, and then bringing the organic compound into contact with the organic compound in the gas phase. Or a method of contacting the titanium dioxide and the organic compound in an aqueous slurry.

  A method for forming a coating layer of an organic compound by contacting with the organic compound in a gas phase includes a dry pulverizer such as a fluid energy pulverizer and an impact pulverizer, a high-speed stirrer such as a Henschel mixer and a super mixer, and the like. It can be carried out by stirring and mixing the titanium dioxide and the organic compound.

  The method of forming a coating layer of an organic compound by bringing it into contact with the aqueous slurry is performed by adding the organic compound to the aqueous slurry, followed by stirring and mixing after coating with a metal oxide. Can do.

Examples of the ethylene resin (B) include polyvinyl butyral resins, ionomer resins, polyacrylic resins, polymethacrylic resins, polyvinyl alcohol resins, copolymer resins using at least ethylene, polyvinyl acetate resins, and the like. A modified resin or the like is preferable. Among these, a copolymer resin using at least ethylene is more preferable. The copolymer resin using at least ethylene is a copolymer of two or more types of monomers, and is not particularly limited as long as at least one of the monomers is an ethylene monomer. Specifically, ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene ethyl acrylate copolymer, ethylene methyl methacrylate copolymer, ethylene ethyl methacrylate copolymer, ethylene ionomer, ethylene acetate Examples include vinyl multi-component copolymers, ethylene methyl acrylate multi-component copolymers, ethylene ethyl acrylate multi-component copolymers, ethylene methyl methacrylate multi-component copolymers, and ethylene ethyl methacrylate multi-component copolymers. It is done. Among these, an ethylene vinyl acetate copolymer is preferable. Furthermore, in the lamination process when manufacturing a solar cell module, the power generation element is not easily damaged, and from the viewpoint of improving the transparency and productivity of the solar cell encapsulant, synthesis of ethylene vinyl acetate copolymer is performed using vinyl acetate. Is preferably used in an amount of 15 to 40% by weight, more preferably 25 to 35% by weight.
In the present invention, the ethylene resin (B) preferably has a melt flow rate (hereinafter simply referred to as MFR) of 0.1 to 60 g / 10 min, and more preferably 0.5 to 45 g / 10 min. By setting the MFR within a predetermined range, the moldability, mechanical strength, and the like can be improved. The melt flow rate is a numerical value measured according to JIS K7210.

  The resin composition for a solar cell encapsulant of the present invention can be blended with titanium dioxide (A) and an ethylene resin (B) in a compounding amount according to the raw material ratio of the encapsulant. In this case, 2 to 25 parts by weight of titanium dioxide (A) is preferably blended with 100 parts by weight of ethylene-based resin (B), and more preferably 5 to 20 parts by weight. By blending 2 to 25 parts by weight, it is easy to obtain a reflection effect.

  Moreover, it is preferable to manufacture the resin composition for solar cell sealing materials of this invention as what is called a masterbatch which mix | blended titanium dioxide (A) with high concentration. Once the masterbatch is manufactured, when the masterbatch is mixed with the main resin of the sealing material, for example, ethylene vinyl acetate copolymer, the titanium dioxide (A) is uniformly in the sealing material. Easy to disperse. Specifically, it is preferable to mix 20 to 200 parts by weight of titanium dioxide (A) with respect to 100 parts by weight of the ethylene-based resin (B), and more preferably 50 to 200 parts by weight.

  The resin composition for a solar cell encapsulant of the present invention is optionally added with a crosslinking agent, a crosslinking aid, a silane coupling agent, an ultraviolet absorber, a light stabilizer, an antioxidant, a flame retardant, a dispersant, and the like. It is also possible to mix an agent. As these additives, known compounds can be used for solar cell sealing materials. Furthermore, various additives can be produced by blending with titanium dioxide (A) and ethylene resin (B), but when producing a solar cell encapsulant, a resin composition for solar cell encapsulant It is also possible to add it separately from the product.

  The crosslinking agent is used for imparting cohesive force to the ethylene-based resin, and an organic peroxide is generally used. Although the addition amount is not particularly limited, it is preferably used in an amount of 0.05 to 1.5 parts by weight with respect to a total of 100 parts by weight of the ethylene resin and titanium dioxide. Specific examples include tert-butyl peroxyisopropyl carbonate, tert-butyl peroxy-2-ethylhexyl isopropyl carbonate, tert-butyl peroxyacetate, tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di (Tert-butylperoxy) hexane, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 2,5-dimethyl-2,5-di (Tert-butylperoxy) hexane, 1,1-di (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (tert-butylperoxy) cyclohexane, 1,1-di (Tert-hexylperoxy) cyclohexane, 1,1-di tert-amylperoxy) cyclohexane, 2,2-di (tert-butylperoxy) butane, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-diperoxybenzoate, tert-butyl hydroperoxide, p -Mentane hydroperoxide, dibenzoyl peroxide, p-chlorobenzoyl peroxide, tert-butylperoxyisobutyrate, n-butyl-4,4-di (tert-butylperoxy) valerate, ethyl-3,3 -Di (tert-butylperoxy) butyrate, hydroxyheptyl peroxide, dichlorohexanone peroxide, 1,1-di (tert-butylperoxy) 3,3,5-trimethylcyclohexane, n-butyl-4,4- Te t- butyl peroxy) valerate, 2,2-di (tert- butylperoxy) include butane and the like.

  The crosslinking aid is used to improve the reaction efficiency between the ethylene resin and the crosslinking agent. For example, compounds having a plurality of vinyl groups such as polyallyl compounds and polyacryloxy compounds are preferred. The crosslinking aid is preferably used in an amount of 0.05 to 1.5 parts by weight with respect to a total of 100 parts by weight of the ethylene resin and titanium dioxide. Specific examples include triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and the like.

  The silane coupling agent is used to improve the adhesion of the molded member. Examples thereof include compounds having a hydrolyzable group such as an unsaturated group such as a vinyl group, an acryloxy group or a methacryloxy group, or an alkoxy group. The silane coupling agent is preferably used in an amount of 0.05 to 1.5 parts by weight with respect to a total of 100 parts by weight of the ethylene resin and titanium dioxide. Specific examples include vinyltrichlorosilane, vinyltris (βmethoxyethoxy) silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. , Γ-glycidoxypropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, Examples thereof include N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane.

The resin composition for a solar cell encapsulant of the present invention can be produced by melting and kneading a raw material containing titanium dioxide (A) and an ethylene-based resin (B) and further forming into a pellet form. This pellet is preferably produced as a master batch in which titanium dioxide is blended at a high concentration. Here, the melt kneading of the raw materials is performed separately after mixing the raw materials in advance using a general high-speed shearing type mixer such as a Henschel mixer, a super mixer, etc. It may be put into a kneader. Or it can manufacture also by mix | blending all the raw materials which can be used for a sealing material.
For the melt-kneading, for example, a two-roll, three-roll, pressure kneader, Banbury mixer, single-screw kneading extruder, or twin-screw kneading extruder is preferably used.

  The solar cell sealing material of this invention can be manufactured by melt-kneading the resin composition for solar cell sealing materials, and then shape | molding it. As the forming method, a known sheet forming method such as a T-die extruder or a calendar forming machine can be used. The thickness of the solar cell encapsulant is preferably about 0.1 to 1 mm.

  In addition, when the solar cell encapsulant is produced by using the solar cell encapsulant resin composition as a master batch, the ethylene-based resin for dilution and the master batch are melt-kneaded and then molded in the same manner as described above. It is preferable to manufacture.

An example of the configuration of the solar cell module of the present invention will be described with reference to FIG. 1 and FIG. The solar cell module of FIG. 1 is manufactured by first depositing a compound semiconductor to be the power generating element 13 on the transparent substrate 11, laminating the solar cell sealing material 12 and the back transparent substrate 14, and heating and pressing. can do. The transparent substrates 11 and 14 are preferably heat strengthened white plate glass. Moreover, it is preferable to use a vacuum laminator with a temperature controller for the heating and pressurization.
Moreover, the solar cell module of FIG. 2 which does not vapor-deposit a power generation element can be manufactured by sealing the upper and lower sides of a solar cell element with a solar cell sealing material. For example, the transparent substrate 15, the solar cell sealing material 16 </ b> A, the power generation element 17, the solar cell sealing material 16 </ b> B, and the back transparent substrate 18 can be laminated in this order, and heated and pressurized. The transparent substrates 15 and 18 are preferably heat strengthened white plate glass. In general, a vacuum laminator can be used for heating and pressurization.

  EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, a part means a weight part and% means weight%, respectively.

  The example of the surface coating method by the metal oxide of titanium dioxide is shown below. The surface coating method is not limited to the following method.

<Titanium dioxide surface coating layer formation 1>
Rutile titanium dioxide particles having an average particle size of 0.37 μm were mixed with water to prepare an aqueous slurry having a titanium dioxide weight of 300 g / l. While this slurry was kept at 60 ° C., 2.5 parts by weight of sodium silicate in terms of SiO ₂ was added to 100 parts by weight of titanium dioxide before surface coating while stirring. Next, the coating layer of silicon oxide was formed by adjusting the pH to about 5 with sulfuric acid. Thereafter, the mixture was filtered and washed, further dried at 120 ° C. for 16 hours, and pulverized with a jet mill to obtain titanium dioxide (A-1) coated with a silicon hydroxide. The inorganic treatment amount of titanium dioxide was measured by chemical composition analysis using a fluorescent X-ray apparatus.

<Titanium dioxide surface coating layer formation 2>
Rutile titanium dioxide particles having an average particle diameter of 0.26 μm were mixed with water to prepare an aqueous slurry having a titanium dioxide weight of 300 g / l. While maintaining this slurry at 60 ° C., 4.0 parts by weight of sodium silicate in terms of SiO ₂ was added to 100 parts by weight of titanium dioxide before being surface-coated while stirring. Next, the coating layer of silicon oxide was formed by adjusting the pH to about 5 with sulfuric acid. Subsequently, after adding 2.5 parts by weight of sodium aluminate in terms of Al ₂ O ₃ to 100 parts by weight of titanium dioxide before surface coating with stirring, aluminum oxidation is performed by adjusting the pH to 5 with sulfuric acid. A coating layer of the product was formed. Thereafter, the mixture was filtered, washed, dried at 120 ° C. for 16 hours, and pulverized with a jet mill to obtain titanium dioxide (A-2) coated with a silicon hydroxide and an aluminum hydroxide.

<Titanium dioxide surface coating layer formation 3>
Rutile titanium dioxide particles having an average particle diameter of 0.22 μm were mixed with water to prepare an aqueous slurry having a titanium dioxide weight of 300 g / l. While maintaining this slurry at 60 ° C., 1.5 parts by weight of sodium silicate in terms of SiO ₂ was added to 100 parts by weight of titanium dioxide before being surface-coated while stirring. Next, the coating layer of silicon oxide was formed by adjusting the pH to about 5 with sulfuric acid. Subsequently, 0.7 parts by weight of zirconium sulfate oxide in terms of ZrO ₂ and 2.0 parts by weight of sodium aluminate in terms of Al ₂ O ₃ with respect to 100 parts by weight of titanium dioxide before the surface treatment of titanium dioxide with stirring. After the addition, the aluminum oxide coating layer was formed by adjusting the pH to 5 with sulfuric acid. Thereafter, the mixture was filtered, washed, dried at 120 ° C. for 16 hours, and pulverized with a jet mill to obtain titanium dioxide (A-3) coated with a silicon oxide and an aluminum oxide.

<Titanium dioxide surface coating layer formation 4>
Rutile titanium dioxide particles having an average particle diameter of 0.28 μm were mixed with water to prepare an aqueous slurry having a titanium dioxide weight of 300 g / l. While maintaining this slurry at 60 ° C., 4.0 parts by weight of sodium aluminate in terms of Al ₂ O ₃ was added to 100 parts of titanium dioxide before surface coating with stirring, and then the pH was adjusted with sulfuric acid. By adjusting to 5, an aluminum oxide coating layer was formed. Thereafter, the mixture was filtered, washed, further dried at 120 ° C. for 16 hours, and pulverized with a jet mill to obtain titanium dioxide (A-14) coated with aluminum oxide.

  As described in Table 1 for (A-4) to (A-13), (A-15), and (A-16) by the same method as above, a surface coating layer using a metal oxide for titanium dioxide was prepared. Formed.

  Further, (A-9) to (A-13), (A-16), and (A-17) formed a surface coating layer using the organic substance (c) shown in Table 1.

  Next, an example of a surface coating method using an organic substance of titanium dioxide is shown below. The surface coating method is not limited to the following method.

(Titanium dioxide surface coating layer formation 5)
Titanium dioxide formed with a metal oxide coating layer is filtered from an aqueous slurry, washed, dried at 120 ° C. for 16 hours, and pulverized with a jet mill while hexyl with respect to 100 parts by weight of titanium dioxide before surface coating. Titanium dioxide (A-9) and (A-13) having a surface coating layer using an organic substance were obtained by adding 0.7 parts by weight of triethoxysilane, and mixing and coating.

(Titanium dioxide surface coating layer formation 6)
Titanium dioxide having a metal oxide coating layer is filtered from an aqueous slurry, washed, dried at 120 ° C. for 16 hours, and pulverized with a jet mill while triturating with respect to 100 parts by weight of titanium dioxide before surface coating. 0.5 parts by weight of methylolethane was added, mixed and coated to obtain titanium dioxide (A-10), (A-12) and (A-16) having a surface coating layer using an organic substance.

(Titanium dioxide surface coating layer formation 7)
Titanium dioxide having a metal oxide coating layer is filtered from an aqueous slurry, washed, dried at 120 ° C. for 16 hours, and pulverized with a jet mill, and methylated relative to 100 parts by weight of titanium dioxide before surface coating. 0.35 parts by weight of hydrogen polysiloxane was added, mixed and coated to obtain titanium dioxide (A-11) having a surface coating layer using an organic substance. Moreover, (A-17) was obtained by surface-coating methylhydrogen polysiloxane on titanium dioxide not treated with a metal oxide.

  Table 1 shows the coating composition and properties of titanium dioxide.

(B) Ethylene resin (B-1) Ultracene 751 (produced by Tosoh Corporation, ethylene vinyl acetate copolymer, vinyl acetate content: 28%, MFR: 5.7)
(B-2) Everflex V523 (Mitsui / DuPont Polychemical Co., Ltd., ethylene vinyl acetate copolymer, vinyl acetate content: 33%, MFR: 14)

[Example 1]
After putting 50 parts of Ultrasen 751 and 50 parts of titanium dioxide (A-1) into a super mixer (manufactured by Mitsui Mining Co., Ltd.) and stirring at a temperature of 25 ° C. for 3 minutes, a twin screw extruder (manufactured by Nippon Placon Co., Ltd.) ) And melt-kneaded at a temperature of 140 ° C. to obtain a master batch of a resin composition for a solar cell encapsulant.
Separately, a crosslinker master batch in which Ultrasen 751 and a crosslinking agent, a crosslinking aid, and a silane coupling agent were blended, and a UV absorber master batch in which Ultrasen 751 and a UV absorber were blended were prepared.
Ultrasen 751 was added so that the master resin batch for the solar cell encapsulant resin composition, the cross-linking agent master batch, the stabilizer master batch, and the blending amounts shown in Table 2 were added. Charged to a T-die extruder. Next, extrusion molding was performed at 90 ° C. to obtain solar cell sealing materials 12 and 19 (thickness 500 μm). In addition, the kind and compounding quantity of the crosslinking agent, the crosslinking assistant, the silane coupling agent, and the ultraviolet absorber in the solar cell encapsulant are as follows with respect to 100 parts in total of Ultracene 751 and titanium dioxide. I used it.
Crosslinking agent: t-butylperoxy-2-ethylhexyl monocarbonate 0.6 parts Crosslinking aid: triallyl isocyanurate 0.6 parts Silane coupling agent: γ-methacryloxypropyltrimethoxysilane 0.4 parts UV absorber : 2-hydroxy-4 octoxybenzophenone 0.2 part

[Examples 2 to 17]
Solar cell encapsulants 12 and 19 were obtained in the same manner as in Example 1 except that ethylene resin and titanium dioxide were mixed so as to have the composition shown in Table 2, respectively.

[Comparative Examples 1-8]
In Comparative Examples 1 to 8, 50 parts of an ethylene-based resin and 50 parts of titanium dioxide shown in Table 1 were put into a supermixer (manufactured by Mitsui Mining Co., Ltd.) and stirred at a temperature of 25 ° C. for 3 minutes. The master batch of the resin composition for solar cell sealing materials was obtained by throwing into the shaft extruder (made by Nippon Placon Co., Ltd.), and melt-kneading at the temperature of 140 degreeC. Other than that was carried out similarly to Example 1, and obtained the crosslinking agent masterbatch and the ultraviolet absorber masterbatch. The solar cell encapsulant masterbatch, the crosslinker masterbatch, the UV absorber masterbatch, and an ethylene resin were further blended and the blending ratios shown in Table 3 were used, as in Example 1. Solar cell sealing materials 12 and 19 were obtained.

  The solar cell sealing materials obtained in Examples 1 to 17 and Comparative Examples 1 to 8 were evaluated according to the following criteria, and the evaluation results are shown in Table 4.

[Preparation of test sample 1]
As shown in FIG. 2, the obtained solar cell encapsulant 19 was sandwiched between a 3 mm thick glass plate 20, a 50 μm thick release sheet 21, and a 300 μm thick protective member 22. Then, it heated for 5 minutes at 150 degreeC under vacuum using the vacuum laminator, and was thermocompression bonded for 15 minutes after that, and the sealing material was bridge | crosslinked. The release sheet is inserted only for the half area, and the glass plate 20 and the sealing material 19 are not bonded to each other at the inserted portion. Next, the laminated body of the sealing material and the protective member was cut into a 1 cm wide strip to obtain a test sample 1 having a width of 1 cm shown in FIG. Then, the 180 degree | times glass peeling test was implemented about the sample which left still for 24 hours in temperature 23 degreeC and humidity 50% RH environment, and the sample after an endurance test. The release sheet is treated with silicone. The protective member has a three-layer structure in which a linear low density polyethylene resin layer, an adhesive layer, and a polyethylene terephthalate resin layer are laminated, and the surface in contact with the sealing material is a linear low density polyethylene resin layer.

[180 degree glass peeling test]
The peel strength between the sealing material and the glass plate was measured using a test sample 1 shown in FIG. Specifically, as shown in FIG. 4, the test sample is sandwiched between the knob of the tensile tester (manufactured by Toyo Seiki) and the other part of the transparent substrate 20 that is not in close contact with the sealing material 19, and the other is sealed. A 180 ° peel test was performed at a tensile speed of 300 mm / min with the laminate portion of the material 19 and the protective member 22 interposed therebetween.

  The endurance test was conducted by a pressure cooker test, and the test sample 1 was allowed to stand for 96 hours in an environment of temperature 105 ° C. and humidity 100% RH.

[Preparation of test sample 2 (solar cell module)]
The obtained solar cell encapsulant 12 (thickness 500 μm) is sandwiched between the glass plate 11 (thickness 3 mm) on which the power generating element 13 is deposited and the glass plate (thickness 3 mm) of the back transparent substrate 14, and a vacuum laminator 1 was heated at 150 ° C. for 5 minutes under vacuum, and then thermocompression bonded for 15 minutes to crosslink the sealing material, thereby producing the solar cell module of FIG.

[Conversion efficiency retention]
Test 2 was tested by a dump heat test using a constant temperature and humidity tester at a temperature of 85 ° C. and a humidity of 85% RH for 4000 hours, and the change in conversion efficiency was evaluated for the sample after the test. did. This conversion efficiency was calculated from the incident light energy, the output at the optimum operating point, and the area of the power generation element. In the evaluation method, the conversion efficiency of the power generation element alone was set to 100, and the conversion efficiency before the sample test (initial conversion efficiency) and the conversion efficiency after the test (time-dependent conversion efficiency) were obtained.

  From the results of Table 4, in Examples 1 to 17, the initial conversion efficiency was improved, and excellent glass adhesiveness and conversion efficiency retention rate exceeding the comparative example were obtained. In the present invention, the surface of titanium dioxide is coated with an inorganic substance containing silicon oxide, so there is no reduction in initial glass adhesive strength compared to titanium dioxide without surface coating, and high sealing performance is achieved. Therefore, a surprising result was obtained that the deterioration of the solar cell was suppressed over time and a high conversion efficiency retention rate was made possible.

DESCRIPTION OF SYMBOLS 11 Transparent substrate 12 Solar cell sealing material 13 Power generation element 14 Back surface transparent substrate 15 Transparent substrate 16A Solar cell sealing material 16B Solar cell sealing material 17 Power generation element 18 Back surface transparent substrate 19 Solar cell sealing material 20 Glass plate 21 Release Sheet 22 Protective member 23 Glass bonding surface 24 Glass non-bonding surface

[Examples 2 to 17]
Solar cell encapsulants 12 and 19 were obtained in the same manner as in Example 1 except that ethylene resin and titanium dioxide were mixed so as to have the composition shown in Table 2, respectively. In the present application, Examples 1, 4 and 9 are reference examples.

Claims (8)

Including titanium dioxide (A) having an average primary particle size of 0.15 to 0.45 μm, and an ethylene-based resin (B),
The titanium dioxide (A) has a surface coating layer formed of 2 to 7 parts by weight of a metal oxide (C) containing a silicon oxide with respect to 100 parts by weight of titanium dioxide before surface coating. A resin composition for a battery sealing material.   The resin composition for a solar cell encapsulant according to claim 1, wherein the metal oxide (C) further contains an oxide of aluminum.   3. The solar cell sealing according to claim 1, wherein the metal oxide (C) contains 1 to 5 parts by weight of an oxide of silicon based on 100 parts by weight of titanium dioxide before surface coating. Resin composition for materials.   The titanium dioxide (A) further has a surface coating layer formed of an organic material, and the resin composition for a solar cell encapsulant according to any one of claims 1 to 3.   The solar cell sealing material formed by shape | molding the resin composition for solar cell sealing materials in any one of Claims 1-4. Including 100 parts by weight of an ethylene-based resin (B) and 20 to 200 parts by weight of titanium dioxide (A) having an average primary particle size of 0.15 to 0.45 μm,
The titanium dioxide (A) has a surface coating layer formed of 2 to 7 parts by weight of a metal oxide (C) containing a silicon oxide with respect to 100 parts by weight of titanium dioxide before surface coating. Master batch for battery encapsulant.   A solar cell sealing material obtained by mixing and molding an ethylene-based resin and the master batch for solar cell sealing material according to claim 6.   The solar cell module provided with the solar cell sealing material of Claim 5 or 7 at least.

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