JP2010186932A - Surface protection sheet for solar cell and solar cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protection sheet for a solar cell, having good bondability with a sealing film mainly containing an ethylene vinyl acetate copolymer. <P>SOLUTION: The surface protection sheet for a solar cell, having good bondability with a sealing film mainly containing an ethylene vinylacetate copolymer includes: an ethylene vinyl acetate copolymer resin composition layer containing 100 pts.wt. ethylene vinyl acetate copolymer containing 15-50 wt.% content of vinyl acetate and 0.01-1.5 pts.wt. epoxy compound, and subjected to oxidation treatment; and a resin film layer. A solar cell uses the protection sheet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface protective sheet for a solar cell and a solar cell using the same.

  In recent years, solar cells are rapidly spreading as means for solving problems such as depletion of petrochemical resources and progress of environmental destruction. In general, solar cells use solar cells such as crystalline silicon, and are laminated with front side surface protective material, sealing film, solar cell, sealing film, back side surface protective material, etc., and vacuum suction heating lamination. Manufactured using laws.

  The front side surface protective material is a glass substrate with sufficient strength to protect the solar cell, or a resin film such as a polyester film, and the back side surface protective material is a lightweight and durable polyester film or fluororesin. A resin film such as a film is generally used.

  On the other hand, the sealing film is required to have performance such as transparency, flexibility, electrical insulation and durability, and generally a film mainly composed of ethylene-vinyl acetate copolymer is used for solar cells and peripheral wiring. The front side surface protection member and the back side surface protection member also serve as an adhesive.

  However, since the adhesion between the polyester film generally used for the backside surface protective material and the sealing film mainly composed of ethylene-vinyl acetate copolymer is not so good, styrene-olefin copolymer is used for the purpose of improving the adhesive strength. Providing a thermal adhesive layer (hot melt adhesive layer) of a polymer resin has been proposed (see, for example, Patent Document 1).

  In addition, it has been proposed to provide an adhesion improving layer composed of a polyester resin or a polyurethane resin on a polyester film (see, for example, Patent Document 2). Furthermore, it has been proposed to provide an easy-adhesion layer containing an oxazoline group-containing polymer as a crosslinking agent (see, for example, Patent Document 3).

JP 2003-060218 A (Claims) JP 2007-136911 A (Claims) JP 2006-261288 A (Claims)

  However, the method proposed in Patent Documents 1 to 3 uses an ethylene-vinyl acetate copolymer in order to adhere a sealing film (hereinafter sometimes simply referred to as a sealing film) and a polyester film. Since an adhesive layer different from the vinyl acetate copolymer is provided, there is a problem that the adhesiveness is not sufficient, and an organic solvent which is an environmental burden must be used to form the adhesive layer.

  As a result of intensive studies to solve the above problems, the inventors of the present invention consisted of 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15 to 50% by weight and 0.01 to 1.5 parts by weight of an epoxy compound. The present invention was completed by finding that a surface protective sheet for a solar cell having good adhesion to a sealing film can be obtained by laminating a resin film on an oxidized ethylene-vinyl acetate copolymer resin composition layer. I came to let you.

  That is, the present invention relates to an oxidized ethylene-vinyl acetate copolymer comprising 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15 to 50% by weight and 0.01 to 1.5 parts by weight of an epoxy compound. The present invention relates to a surface protection sheet for a solar cell comprising a resin composition layer and a resin film layer, and a solar cell using the same.

  Hereinafter, the present invention will be described in detail.

  The surface protective sheet for a solar cell of the present invention comprises an ethylene-vinyl acetate copolymer comprising 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15 to 50% by weight and 0.01 to 1.5 parts by weight of an epoxy compound. A layer made of a polymer resin composition is oxidized and then laminated on a resin film.

  The thickness of the ethylene-vinyl acetate copolymer resin composition layer is not particularly limited, and is preferably 0.5 to 1000 μm because the adhesion between the obtained solar cell surface protective sheet and the sealing film is improved. 500 μm is more preferable, and 1 to 100 μm is particularly preferable.

  In addition, the thickness of the resin film layer is not particularly limited, and is more preferably 5 to 3000 μm and 5 to 250 μm, and particularly preferably 10 to 150 μm because of high durability and strength.

  The resin film used in the present invention is not particularly limited. For example, polytetrafluoroethylene, 4-fluorinated ethylene-perchloroalkoxy copolymer, 4-fluorinated ethylene-6-fluorinated propylene copolymer, 2-ethylene. -4-Fluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, and other fluorine resin films, polyethylene terephthalate, polyethylene naphthalate and other polyester films, polycarbonate films, polyamide films, polymethyl methacrylate films, polyvinyl alcohol films, Examples thereof include a resin film such as an ethylene-vinyl acetate copolymer saponified film. Among them, a polyester film is preferable because of excellent heat resistance and durability, and a polyethylene terephthalate film and a polyethylene naphthalate film are particularly preferable.

  The ethylene-vinyl acetate copolymer used in the present invention is not particularly limited as long as the vinyl acetate content measured according to JIS K6924 (1997 edition) is 15 to 50% by weight, and a known one can be used. Those having a vinyl acetate content of 20 to 35% by weight are preferred. Moreover, the vinyl acetate in the ethylene-vinyl acetate copolymer may be partially saponified. In general, since an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20 to 35% by weight is used for the sealing film, the ethylene-vinyl acetate copolymer used in the present invention has a vinyl acetate content of less than 15% by weight. Adhesive strength between the solar cell surface protective sheet and the sealing film obtained in the present invention is not sufficient, and even if it exceeds 50% by weight, the adhesive strength between the solar cell surface protective sheet and the sealing film obtained in the present invention is sufficient. Not.

  The melt index (hereinafter abbreviated as MI) measured in accordance with JIS K7210 (1995 edition) of an ethylene-vinyl acetate copolymer is 0.1 to 800 g / 10 from the viewpoint of fluidity and adhesive strength during molding. Minutes, preferably 0.1 to 100 g / 10 minutes, more preferably 1.0 to 15 g / 10 minutes.

  The epoxy compound used in the present invention is not particularly limited as long as it has an epoxy group, and known compounds can be used.

  Examples of the epoxy compound include an epoxy-modified diene copolymer, an unsaturated epoxy (co) polymer, an epoxidized vegetable oil, a silane coupling agent having an epoxy group and an alkoxy group, and an epoxy resin. Among them, the adhesive strength between the layer comprising the ethylene-vinyl acetate copolymer resin composition and the resin film is improved, so that an epoxy-modified diene copolymer, an unsaturated epoxy (co) polymer, an epoxidized vegetable oil, an epoxy group, and A silane coupling agent having an alkoxy group is preferred, and a silane coupling agent having an epoxy group and an alkoxy group is more preferred.

  The epoxy-modified diene copolymer can be obtained, for example, by epoxy-modifying a diene polymer. Examples of the diene polymer that forms the epoxy-modified diene polymer include 1,3-butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 1,3. Examples thereof include homopolymers such as pentadiene, 1,3-hexadiene, 2,4-hexadiene, and 2,4-heptadiene, or two or more types of copolymers. Styrene, acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, and the like may be copolymerized with a diene monomer. The method for producing a diene polymer is, for example, copolymerizing a mixture of a diene monomer and other monomers that can be copolymerized as necessary in the presence of a radical generator or a chain transfer agent in a solvent. Can be obtained. In addition, it can be obtained by a generally known method such as an anionic polymerization method.

  In order to obtain an epoxy-modified diene polymer, the epoxy modification method of the diene polymer is not particularly limited, and examples thereof include a method of treating with hydrogen peroxide and an organic peracid.

  The molecular end group of the epoxy-modified diene polymer is not particularly limited, and may be modified with a hydroxyl group, a carboxyl group, an epoxy group, or the like.

  The epoxy-modified diene polymer may be partially or completely hydrogenated.

  The number average molecular weight of the epoxy-modified diene polymer is preferably 5000 or more because the adhesion between the ethylene-vinyl acetate copolymer resin composition layer and the resin film is improved.

  The epoxy group content of the epoxy-modified diene polymer is preferably 5% or more as the oxirane oxygen content because the adhesion between the ethylene-vinyl acetate copolymer resin composition layer and the resin film is improved. The oxirane oxygen content can be determined by dissolving a sample in a solvent such as benzene, adding an indicator such as crystal violet, and titrating with a hydrogen bromide standard solution.

  The epoxy-modified diene polymer having the above structure and performance is not particularly limited as long as the above-mentioned diene polymer is epoxy-modified, and liquid epoxidized polybutadiene is most preferable. The liquid polybutadiene forming the liquid epoxidized polybutadiene may be either 1,2-polybutadiene or 1,4-polybutadiene. Examples include “Epolide RB3600” manufactured by Daicel Chemical Industries, and “BF-1000” manufactured by Asahi Denka Kogyo, and “Epolide RB3600” is most preferable.

  Examples of the unsaturated epoxy (co) polymer include those containing a monomer residue having an unsaturated group capable of radical polymerization and an epoxy group, and a monomer having an unsaturated group and an epoxy group ( Hereinafter, a homopolymer of an unsaturated epoxy monomer) or a copolymer of the monomer and another monomer having an unsaturated group can be mentioned.

  Such unsaturated epoxy monomers are not particularly limited, and examples thereof include glycidyl acrylate, glycidyl methacrylate, β-methyl glycidyl acrylate, β-methyl glycidyl methacrylate, glycidyl itaconate, glycidyl buteninate, glycidyl Unsaturated glycidyl esters such as xenoate and glycidyl oleate; Unsaturated glycidyl ethers such as allyl glycidyl ether, p-ethylenylphenyl glycidyl ether and propenyl glycidyl ether; Glycidyl styrenes such as p-glycidyl styrene; Epoxy alkenes such as epoxybutene, 3,4-epoxy-1-pentene, 3,4-epoxy-3-methylpentene, and 5,6-epoxy-1-hexene are ethylene-vinyl acetate copolymer trees. Since the adhesiveness of the layer which consists of a fat composition, and a resin film can be improved, it is preferable. These may be used alone or in combination.

  Examples of other monomers having an unsaturated group copolymerizable with an unsaturated epoxy monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2- Acrylic esters having an alkyl group such as ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, cetyl acrylate, cetyl methacrylate, stearyl acrylate, stearyl methacrylate; aromatic vinyl such as styrene, α-methylstyrene, o-chlorostyrene, vinylnaphthalene Compounds: cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile, polyethylene glycol acrylate, polypropylene acrylate Polyalkylene glycol acrylates such as glycol, polyalkylene glycol methacrylates; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, etc., and one or more of these Can be used in combination. Among these, acrylic acid esters are most preferable because the layer made of the ethylene-vinyl acetate copolymer resin composition and the resin film exhibit good adhesiveness.

  The amount of the unsaturated epoxy monomer in the unsaturated epoxy (co) polymer is 15 to 100 mol% because the adhesion between the layer comprising the ethylene-vinyl acetate copolymer resin composition and the resin film is improved. It is preferably 20 to 98 mol%.

  The weight average molecular weight of the unsaturated epoxy (co) polymer is preferably 1000 to 20000, more preferably 4000 to 20000, because the adhesion between the layer composed of the ethylene-vinyl acetate copolymer resin composition and the resin film is improved. preferable.

  The unsaturated epoxy (co) polymer can be produced by a known method. For example, the solution polymerization method is obtained by copolymerizing a mixture of an unsaturated epoxy monomer and another copolymerizable monomer in a solvent at 40 to 150 ° C. in the presence of a radical generator or a chain transfer agent. It is done. In addition, it can be obtained by a generally known method such as a suspension polymerization method or an emulsion polymerization method.

  Examples of the epoxidized vegetable oil include epoxidized soybean oil and epoxidized linseed oil.

  Examples of the silane coupling agent having an epoxy group and an alkoxy group include β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, Examples include γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycidoxypropylmethyldiethoxysilane is particularly preferable.

  These silane coupling agents having an epoxy group and an alkoxy group may be used alone or in combination of two or more, and may be used in combination with other silane coupling agents or titanium-based coupling agents. . As the silane coupling agent having an epoxy group and an alkoxy group used in the present invention, known ones can be used, for example, manufactured by Chisso Corporation, trade names: Silaace S510, S520, S530, manufactured by Shin-Etsu Chemical Co., Ltd. Product names: Shin-Etsu Silicone KBM303, KBM403, KBE402, KBE403 and the like.

  Examples of the epoxy resin include monofunctional epoxy compounds such as phenyl glycidyl ether, lauryl glycidyl ether, phenoxypolyethylene glycol glycidyl ether, benzoic acid glycidyl ether; terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, phthalic acid diglycidyl ester, Examples include bifunctional epoxy compounds such as p-phenylene diglycidyl ether, diethylene glycol diglycidyl ester, diethylene glycol diglycidyl ether, 2,2-bis (4-glycidyloxyphenyl) propane, and bisphenol A type epoxy resin. A bifunctional epoxy compound is preferable, and 2,2-bis (4-glycidyloxyphenyl) propane is particularly preferable.

  These epoxy compounds can be used alone or in combination of two or more.

  The amount of the epoxy compound used in the present invention is 0.01 to 1.5 parts by weight, preferably 0.05 to 1.0 parts by weight, based on 100 parts by weight of the ethylene-vinyl acetate copolymer. It is.

  When the epoxy compound is less than 0.01 parts by weight, the adhesion between the layer composed of the ethylene-vinyl acetate copolymer resin composition and the resin film is not improved. The surface of the surface protection sheet may become sticky, or the adhesion between the layer made of the ethylene-vinyl acetate copolymer resin composition and the resin film may deteriorate.

  It is preferable that the ethylene-vinyl acetate copolymer resin composition used in the present invention further contains a cross-linking agent because the durability of the resulting surface protection sheet for solar cells is improved.

  The amount of the crosslinking agent is preferably from 0.1 to 5 parts by weight, more preferably from 0.3 to 2.0 parts by weight based on 100 parts by weight of the ethylene-vinyl acetate copolymer, because generation of gas in the crosslinking step can be suppressed. Part.

  As a cross-linking agent that is preferably further included in the present invention, a cross-linking agent having a 10-hour half-life temperature of 80 to 120 ° C., particularly 85 to 95 ° C. is preferably used because it can suppress the generation of gas in the cross-linking step. The time until the residual amount is reduced to half of the initial value when the crosslinking agent is decomposed is called a half-life, and the 10-hour half-life temperature means a temperature at which the half-life is 10 hours.

  As the cross-linking agent, an organic peroxide is preferably used because a layer composed of an ethylene-vinyl acetate copolymer resin composition having improved moisture resistance can be obtained by a simple method such as a thermal decomposition method.

  Examples of the crosslinking agent that is preferably further included in the present invention include 2,5-dimethylhexane, 2,5-dihydroperoxide, 3-di-t-butyl peroxide, t-dicumyl peroxide, 2,5. -Dimethyl-2,5-bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,5di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert- Butylperoxy) hexyne, dicumyl peroxide, α, α′-bis (tert-butylperoxysopropyl) benzene, n-butyl-4,4-bis (tert-butylperoxy) butane, tert-butylper Oxy-2-ethylhexyl monocarbonate, 2,2-bis (tert-butylperoxy) butane, 1,1-bis (tert-butyl) Tilperoxy) cyclohexane, 1,1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-di (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, t-butyl Peroxybenzoate; benzoyl peroxide and the like.

  Among these, since generation of gas in the crosslinking step can be suppressed, 1,1-di (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, tert-butylperoxy 2-ethylhexyl monocarbonate, 2,5 -Dimethyl-2,5 di (tert-butylperoxy) hexane is preferred.

  The ethylene-vinyl acetate copolymer resin composition used in the present invention preferably further contains a crosslinking aid together with a crosslinking agent because the durability of the resulting surface protection sheet for solar cells is improved. Examples of the crosslinking aid include trifunctional crosslinking aids such as triallyl cyanurate and triallyl isocyanurate, and monofunctional or bifunctional crosslinking aids such as (meth) acrylic esters (eg, NK ester). Can be mentioned. Of these, triallyl cyanurate and triallyl isocyanurate are preferable, and triallyl isocyanurate is particularly preferable.

  The amount of the crosslinking aid is preferably from 0.1 to 5 parts by weight, preferably from 1.0 to 2.0 parts by weight based on 100 parts by weight of the ethylene-vinyl acetate copolymer, because generation of gas in the crosslinking step can be suppressed. More preferred is 0.1 to 0.5 part by weight.

  The ethylene-vinyl acetate copolymer resin composition used in the present invention preferably further contains an adhesion improver because the adhesion between the layer made of the ethylene-vinyl acetate copolymer resin composition and the resin film is improved.

  As the adhesion improver, a silane coupling agent can be used. For example, γ-chloropropylmethoxysilane, vinylethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane. Vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Especially, since generation | occurrence | production of the gas in a bridge | crosslinking process can be suppressed highly, (gamma) -methacryloxypropyl trimethoxysilane is mentioned especially preferable.

  The amount of the adhesion improver is preferably from 0.1 to 1 part by weight, preferably from 0.1 to 0.7 part by weight based on 100 parts by weight of the ethylene-vinyl acetate copolymer, because generation of gas in the crosslinking step can be suppressed. It is more preferable that

  Various resins can be added to the ethylene-vinyl acetate copolymer resin composition according to the present invention as needed within a range not impairing the effects of the present invention, such as high density polyethylene, medium density polyethylene, low density polyethylene, Polyethylene such as linear low density polyethylene and ultra-low density polyethylene; ethylene-α-olefin copolymer, ethylene-vinyl ester copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene- Acrylic ester copolymer, ethylene-methacrylic ester copolymer, ethylene-vinyl alcohol resin, ethylene-propylene copolymer and other ethylene-based copolymers, polypropylene, polypropylene-based copolymers, and chlorinated products of these polyolefin resins Can be mentioned.

  Moreover, various additives can be added to the ethylene-vinyl acetate copolymer resin composition in the present invention as necessary within a range not impairing the effects of the present invention. Examples of the additives include antioxidants, neutralizers, acid acceptors, dyes, organic pigments, inorganic pigments, inorganic reinforcing agents, plasticizers, processing aids such as acrylic processing aids, ultraviolet absorbers, and light stability. Agent, foaming agent, lubricant, wax, crystal nucleating agent, plasticizer, mold release agent, hydrolysis inhibitor, antiblocking agent, antistatic agent, antifogging agent, antifungal agent, rust inhibitor, ion trap agent, difficult Examples thereof include a flame retardant, a flame retardant aid, an inorganic filler, and an organic filler.

  In the present invention, the surface protective sheet for a solar cell comprises an ethylene-vinyl acetate copolymer comprising 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15 to 50% by weight and 0.01 to 1.5 parts by weight of an epoxy compound. It can manufacture by laminating | stacking to a resin film, after oxidizing a polymer resin composition layer. For example, an ethylene-vinyl acetate copolymer resin composition is extruded and laminated with a resin film after oxidation treatment, and an ethylene-vinyl acetate copolymer resin composition is formed into a film and then oxidized to thermal lamination. And a method of laminating with a resin film by a heat sealing method, a vacuum laminating method or the like.

  At that time, the ethylene-vinyl acetate copolymer resin composition is prepared by, for example, mixing an ethylene-vinyl acetate copolymer and an epoxy compound as they are, melt-mixing the ethylene-vinyl acetate copolymer and the epoxy compound with an extruder, etc. -Dissolve vinyl acetate copolymer and epoxy compound in a solvent, mix the solution, remove the solvent, and master batch kneaded epoxy compound in ethylene-vinyl acetate copolymer in advance and pellets of ethylene-vinyl acetate copolymer Can be provided by dry blending.

  The oxidation treatment can include, for example, chromic acid treatment, sulfuric acid treatment, air oxidation, ozone treatment, corona discharge treatment, flame treatment, plasma treatment, etc. Among them, corona discharge can be efficiently improved. At least one of treatment, ozone treatment, flame treatment and / or plasma treatment is preferred, corona discharge treatment and ozone treatment are more preferred, and ozone treatment is particularly preferred.

Corona discharge treatment is widely used as a continuous treatment technique for resin films and sheet surfaces, and is performed by passing the film through a corona atmosphere generated by a corona discharge treatment machine. It is preferable to perform a discharge treatment with a corona discharge density of 1 to 100 W · min / m ² because the adhesion between the layer made of the ethylene-vinyl acetate copolymer resin composition and the resin film is improved.

  The flame treatment is performed by bringing the film surface into contact with a flame generated when natural gas, propane, or the like is burned.

  Plasma treatment is an excited inert gas in which argon or helium, neon, hydrogen, oxygen, air, or other simple substance or mixed gas is electronically excited with a plasma jet, and then charged particles are removed to make it electrically neutral. Is sprayed onto the film surface.

When the ethylene-vinyl acetate copolymer resin composition is subjected to an extrusion laminating method, at least the surface on the side in contact with the resin film of the molten film made of the ethylene-vinyl acetate copolymer resin composition extruded from the die is air or ozone gas. It is preferable to oxidize by. In the case of ozone treatment in which oxidation with ozone gas proceeds, it is preferable to spray 0.5 mg or more of ozone gas per 1 m ^{2 of the} molten film.

  The temperature during extrusion lamination is preferably 50 to 250 ° C, and more preferably 70 to 190 ° C.

  Examples of the method for forming the ethylene-vinyl acetate copolymer resin composition into a film include an inflation molding method, a T-die cast molding method, a calendar molding method, a press molding method, and a solution casting method.

  In addition, the surface of the resin film on the side in contact with the ethylene-vinyl acetate copolymer resin composition is oxidized in order to improve the adhesion between the layer comprising the ethylene-vinyl acetate copolymer resin composition and the resin film. It is preferable. Examples of the oxidation treatment include corona discharge treatment, flame treatment, and plasma treatment. Corona discharge treatment and plasma treatment are preferable, and at least one kind of treatment is preferably performed.

  It is preferable to perform the oxidation treatment at the time of stacking in-line.

  The obtained surface protection sheet for solar cells is preferably heat-treated at 30 ° C. or more for 10 hours or more in order to improve the adhesion between the layer comprising the ethylene-vinyl acetate copolymer resin composition and the resin film.

  The surface protective sheet for a solar cell of the present invention may further include a moisture-proof layer, a white layer, a durable layer, and the like on the resin film side. As a moisture-proof layer, the film which vapor-deposited inorganic oxides, such as aluminum oxide and a silicon oxide, is mentioned, for example. Examples of the white layer include a polyester film coated with a white pigment, a polyester film containing a white pigment or foamed, and the like. Examples of the durable layer include a fluororesin film, a polyester film, and a fluorine-based paint.

  Lamination can be performed, for example, by using an ester adhesive or a urethane adhesive by a dry laminating method or the like.

  The solar cell of the present invention comprises an ethylene-vinyl acetate copolymer which comprises 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15-50% by weight and 0.01-1.5 parts by weight of an epoxy compound. A solar cell surface protective sheet comprising a polymer resin composition layer and a resin film layer, and an ethylene-vinyl acetate copolymer resin composition layer comprising a solar battery cell and an ethylene-vinyl acetate copolymer To form an inner layer, and the resin film layer forms an outer layer. The configuration of the solar cell of the present invention is not particularly limited as long as it includes the surface protective sheet for solar cells of the present invention. For example, the surface protective sheet for solar cells / ethylene-vinyl acetate copolymer of the present invention from the light receiving surface side. Sealing film comprising: solar cell / sealing film comprising ethylene-vinyl acetate copolymer / surface protective sheet for solar battery of the present invention, surface protective sheet for solar battery of the present invention / ethylene-vinyl acetate copolymer A sealing film comprising: a solar cell / a surface protective sheet for a solar cell according to the present invention, a surface protective sheet for a solar cell according to the present invention / solar battery cell / a sealing film composed of an ethylene-vinyl acetate copolymer / of the present invention. Surface protective sheet for solar cell, surface protective sheet for solar cell of the present invention / solar battery cell / surface protective sheet for solar battery of the present invention, glass substrate / sealing film made of ethylene-vinyl acetate copolymer / Positive cell / encapsulation film made of ethylene-vinyl acetate copolymer / surface protective sheet for solar battery of the present invention, glass substrate / encapsulation film made of ethylene-vinyl acetate copolymer / solar battery cell / of the present invention Examples include a surface protective sheet for solar cells.

  According to the present invention, there is provided a surface protective sheet for a solar cell, which has a very wide industrial application range and has good adhesion to a sealing film mainly composed of an ethylene-vinyl acetate copolymer. This surface protection sheet for solar cells is useful as a surface protection material for solar cells.

  The present invention will be described in more detail with reference to the following examples. However, these are examples for helping understanding of the present invention, and the present invention is not limited to these examples. Commercially available products were used unless otherwise specified.

<Ethylene-vinyl acetate copolymer>
Ethylene-vinyl acetate copolymer-1 (hereinafter referred to as EVA-1); Ultracene (registered trademark) 751 (vinyl acetate content 28% by weight, MFR = 5.7 g / 10 min, density = 952 kg / m ³ ), Manufactured by Tosoh Corporation, ethylene-vinyl acetate copolymer-2 (hereinafter referred to as EVA-2); Ultrasen (registered trademark) 637 (vinyl acetate content 20% by weight, MFR = 8.0 g / 10 minutes, Density = 941 kg / m ³ ), manufactured by Tosoh Corporation, ethylene-vinyl acetate copolymer-3 (hereinafter referred to as EVA-3); Ultrasen (registered trademark) YX13 (vinyl acetate content 32 wt%, MFR = 1) . .0g / 10 min, density = 956kg ^{/ m} 3), manufactured by Tosoh Corp. ethylene - vinyl acetate copolymer 4 (hereinafter, referred to as EVA-4); Ultrathene (TM 625 (vinegar . Vinyl content 15 wt%, MFR = 14g / 10 min, density = 935 kg ^{/ m} 3), manufactured by Tosoh Corp. ethylene - vinyl acetate copolymer 5 (hereinafter, referred to as EVA-5); Levapren (TM) 600 HV (vinyl acetate content 60 wt%), ethylene-vinyl acetate copolymer-6 (hereinafter referred to as EVA-6) manufactured by LANXESS; Mersen H (registered trademark H-6410M (saponification with vinyl acetate content 28 wt%) Product, MFR = 16 g / 10 min, density = 950 kg / m ³ ), manufactured by Tosoh Corporation <epoxy compound>
(1) Silane coupling agent having epoxy group and alkoxy group γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Shin-Etsu Silicone KBM403, hereinafter referred to as EP-A)
(2) Epoxy-modified diene copolymer Liquid epoxidized polybutadiene (manufactured by Daicel Chemical Industries, Ltd., trade name Epolide RB3600, number average molecular weight 5900, hereinafter referred to as EP-B)
(3) Epoxidized vegetable oil Epoxidized soybean oil (Asahi Denka Kogyo Co., Ltd., trade name O-130P, hereinafter referred to as EP-C)
(4) Unsaturated epoxy copolymer 280 g of glycidyl methacrylate, 200 g of ethyl acrylate, and 3.0 g of azobisisobutyronitrile were dissolved in 1 L of benzene and polymerized in a nitrogen stream at 60 ° C. for 3 hours. The polymer was precipitated with n-hexane and dried under reduced pressure at 50 ° C. to obtain an unsaturated epoxy copolymer EP-D. The amount of glycidyl methacrylate was 50 mol%, and the weight average molecular weight was 30000.

<Resin film>
(1) Polyethylene terephthalate film Lumirror (registered trademark) T60 (thickness: 125 μm), manufactured by Toray Industries, Inc. (2) Polyethylene naphthalate film Teonex (registered trademark) Q51 (thickness: 75 μm), Teijin DuPont Films Co., Ltd. <Sealing film >
In order to measure the adhesive strength, a sealing film mainly composed of an ethylene-vinyl acetate copolymer was prepared. 100 parts by weight of EVA-1 as an ethylene-vinyl acetate copolymer, 2 parts by weight of 1,1-di (tert-hexylperoxy) -3,3,5-trimethylcyclohexane as a crosslinking agent, and trimethyl as a crosslinking aid 2 parts by weight of allyl isocyanurate and 0.5 parts by weight of γ-methacrylopropyltrimethoxysilane as a silane coupling agent were blended and melt kneaded in a 20 mmφ single screw extruder set at a temperature of 110 ° C. to obtain pellets. It was.

  The obtained pellet was compression molded to produce a sealing film-1 having a thickness of 0.5 mm. The compression molding was performed by heating at 110 ° C. for 300 seconds and then cooling at 30 ° C. for 300 seconds.

<Measurement of adhesive strength>
Peeling test was performed when a tensile tester (manufactured by Shimadzu Corp., trade name: Autograph DCS500) was used, and a resin film was sandwiched with a chuck under the conditions of a sample width of 15 mm and a peeling speed of 300 mm / min. The strength was measured and the peel strength was defined as the adhesive strength.

Example 1
100 parts by weight of EVA-1 as an ethylene-vinyl acetate copolymer and 0.1 parts by weight of EP-A as an epoxy compound were blended and melt-kneaded in a 20 mmφ single screw extruder set at a temperature of 110 ° C. Obtained.

The obtained pellets were supplied to an extruder of an extrusion laminator having a screw of 25 mmφ, and Lumirror (registered trademark) T60 (thickness: 125 μm) was extruded on a corona-treated surface from a T die at a temperature of 190 ° C., and ethylene-vinyl acetate. The copolymer resin composition was laminated to a thickness of 100 μm to obtain a solar cell surface protective sheet. At that time, ozone treatment was performed by spraying 1.0 mg of ozone gas per 1 m ^{2 of} film on the surface of the melted film of the ethylene-vinyl acetate copolymer resin composition in contact with the resin film.

  After storing the obtained surface protection sheet for solar cells in an oven kept at 40 ° C. for 20 hours, the layer composed of the ethylene-vinyl acetate copolymer resin composition and the sealing film-1 are in contact with each other. The sealing film-1 is sandwiched between the obtained surface protection sheets for solar cells, and temporarily bonded at a temperature of 100 ° C. for 5 minutes using a far-infrared heating furnace (manufactured by Tapi Thermology Co., Ltd.), and then set to a temperature of 150 ° C. In the oven for 20 minutes. Then, it cut | disconnected to 15 mm width, and was set as the adhesion test piece. The results of measuring the adhesive strength are shown in Table 1.

実施例２、４〜６
エチレン−酢酸ビニル共重合体としてＥＶＡ−１を１００重量部、エポキシ化合物としてＥＰ−Ａを０．１重量部を用いた代わりに、表１に示すエチレン−酢酸ビニル共重合体、エポキシ化合物、配合量を用いた以外は実施例１と同様に太陽電池用表面保護シートを作製し評価した。評価した結果を表１に示す。

Examples 2, 4-6
Instead of using 100 parts by weight of EVA-1 as the ethylene-vinyl acetate copolymer and 0.1 parts by weight of EP-A as the epoxy compound, the ethylene-vinyl acetate copolymer, epoxy compound, and compounding shown in Table 1 were used. A solar cell surface protective sheet was prepared and evaluated in the same manner as in Example 1 except that the amount was used. The evaluation results are shown in Table 1.

Example 3
100 parts by weight of EVA-3 as an ethylene-vinyl acetate copolymer and 0.1 parts by weight of EP-B as an epoxy compound were blended and melt-kneaded in a 20 mmφ single-screw extruder set at a temperature of 110 ° C. Obtained.

The obtained pellets were compression molded to obtain a film made of an ethylene-vinyl acetate copolymer resin composition having a thickness of 0.5 mm. The compression molding was performed by heating at 110 ° C. for 300 seconds and then cooling at 30 ° C. for 300 seconds. One side of the film is subjected to corona treatment under the condition of 50 W · min / m ² , then Teonex (registered trademark) Q51 (thickness: 75 μm) is used as the resin film, and one side thereof is subjected to corona treatment, and the polyethylene naphthalate film The corona-treated surface of the film and the corona-treated surface of the ethylene-vinyl acetate copolymer resin composition were combined, and heat-bonded at a temperature of 100 ° C. for 5 minutes using a far-infrared heating furnace (manufactured by Tapi Thermology) And the surface protection sheet for solar cells was obtained.

  The obtained surface protection sheet for solar cells was allowed to stand in an environment having a temperature of 23 ° C. and a relative humidity of 50% for 3 days, and then the adhesive strength of the obtained surface protection sheet for solar cells was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 1 and 3-5
Instead of using 100 parts by weight of EVA-1 as the ethylene-vinyl acetate copolymer and 0.1 parts by weight of EP-A as the epoxy compound, the ethylene-vinyl acetate copolymer, epoxy compound, and compounding shown in Table 1 were used. A solar cell surface protective sheet was prepared and evaluated in the same manner as in Example 1 except that the amount was used. The evaluation results are shown in Table 1. However, in Comparative Example 5, no ozone treatment was performed.

Comparative Example 2
Instead of using 100 parts by weight of EVA-1 as the ethylene-vinyl acetate copolymer and 0.1 parts by weight of EP-A as the epoxy compound, the ethylene-vinyl acetate copolymer, epoxy compound, and compounding shown in Table 1 were used. A solar cell surface protective sheet was prepared and evaluated in the same manner as in Example 3 except that the amount was used. The evaluation results are shown in Table 1.

  In Comparative Example 1, since the vinyl acetate content of the ethylene-vinyl acetate copolymer used was too small, the adhesive strength of the obtained surface protection sheet for solar cells was low.

  In Comparative Example 2, the vinyl acetate content of the ethylene-vinyl acetate copolymer used was too high, and the resulting adhesive strength of the solar cell surface protective sheet was low.

  In Comparative Example 3, since the epoxy compound was not used, the adhesive strength of the obtained solar cell surface protective sheet was low.

  In the comparative example 4, the adhesive strength of the surface protection sheet for solar cells obtained when there was too much quantity of the epoxy compound used was low.

  In Comparative Example 5, since the oxidation treatment was not performed, the adhesive strength of the solar cell surface protective sheet was low.

Example 7
100 parts by weight of EVA-1 as an ethylene-vinyl acetate copolymer, 0.1 parts by weight of EP-A as an epoxy compound, 1,1-di (tert-hexylperoxy) -3, 3, 5 as a crosslinking agent -20 mmΦ in which 2 parts by weight of trimethylcyclohexane, 2 parts by weight of triallyl isocyanurate as a crosslinking aid and 0.5 parts by weight of γ-methacrylopropyltrimethoxysilane as a silane coupling agent were mixed and set at a temperature of 110 ° C The mixture was melt kneaded with a single screw extruder to obtain pellets.

The obtained pellets were compression molded to produce a film having a thickness of 0.5 mm. The compression molding was performed by heating at 110 ° C. for 300 seconds and then cooling at 30 ° C. for 300 seconds. One side of the film was subjected to corona treatment under the condition of 50 W · min / m ² to obtain a film made of an ethylene-vinyl acetate copolymer resin composition.

  Thereafter, using Lumirror (registered trademark) T60 (thickness: 125 μm) as a resin film, one side of the film was subjected to corona treatment, and a film comprising the corona-treated surface of the polyethylene terephthalate film and an ethylene-vinyl acetate copolymer resin composition. The corona-treated surfaces were combined, and heat-bonded at a temperature of 100 ° C. for 5 minutes using a far-infrared heating furnace (manufactured by Tapi Thermology Co., Ltd.) to obtain a surface protection sheet for solar cells.

  The obtained solar cell surface protective sheet was allowed to stand in an environment at a temperature of 23 ° C. and a relative humidity of 50% for 3 days, and then the adhesive strength of the obtained solar cell surface protective sheet was measured in the same manner as in Example 1. The adhesive strength was 51 N / 15 mm.

Example 8
In order from the bottom, a glass substrate (manufactured by Hokuriku plate glass), a sealing film-1, and a solar cell surface protective sheet obtained in Example 1 are stacked so that the resin film is on the outside as a front side surface protective material. Using an external heating furnace (manufactured by Tapi Thermogaku Co., Ltd.), after temporary bonding at a temperature of 100 ° C. for 5 minutes, heat bonding was performed in an oven set at a temperature of 150 ° C. for 20 minutes to produce a laminate equivalent to a solar cell. The obtained laminate corresponding to the solar cell had good adhesion between the layers.

Example 9
Two solar cell surface protection sheets obtained in Example 3 were stacked so that the ethylene-vinyl acetate copolymer composition layer was in contact with each other, and a far-infrared heating furnace (manufactured by Tapi Thermal Engineering Co., Ltd.) was used. After temporary bonding at a temperature of 100 ° C. for 5 minutes, thermal bonding was performed for 20 minutes in an oven set at a temperature of 150 ° C. to produce a laminate equivalent to a solar cell. The obtained laminate corresponding to the solar cell had good adhesion between the layers.

  The surface protection sheet for solar cells of the present invention has good adhesion to a sealing film mainly composed of an ethylene-vinyl acetate copolymer, and is useful as a surface protection sheet for solar cells of solar cells.

Claims (10)

An ethylene-vinyl acetate copolymer resin composition layer comprising 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 15 to 50% by weight and 0.01 to 1.5 parts by weight of an epoxy compound, and an oxidation treatment; A surface protective sheet for solar cells, comprising a resin film layer. The surface protective sheet for solar cells according to claim 1, wherein the resin film is a polyester film. The surface protection sheet for solar cells according to claim 2, wherein the polyester film is a polyethylene terephthalate film or a polyethylene naphthalate film. The surface protection sheet for solar cells according to any one of claims 1 to 3, wherein the resin film is oxidized. The surface protection sheet for solar cells according to any one of claims 1 to 4, wherein the oxidation treatment is corona discharge treatment, ozone treatment, flame treatment and / or plasma treatment. The epoxy compound is a silane coupling agent having an epoxy group and an alkoxy group, an epoxy-modified diene copolymer, an epoxidized vegetable oil, and / or an unsaturated epoxy (co) polymer. The surface protection sheet for solar cells of any one of claim | item 5. The surface protection sheet for solar cells according to any one of claims 1 to 6, wherein the epoxy compound is a silane coupling agent having an epoxy group and an alkoxy group. The ethylene-vinyl acetate copolymer resin composition further comprises 0.1 to 5 parts by weight of a crosslinking agent with respect to 100 parts by weight of the ethylene-vinyl acetate copolymer. The surface protection sheet for solar cells according to any one of the items. 9. The sun according to claim 8, wherein the ethylene-vinyl acetate copolymer resin composition further comprises 0.1 to 5 parts by weight of a crosslinking aid with respect to 100 parts by weight of the ethylene-vinyl acetate copolymer. Battery surface protection sheet. The solar cell characterized by including the surface protection sheet for solar cells of any one of Claims 1-9.