JP2010199532A - Backsheet for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backsheet for a solar cell that is excellent in heat resistance, steam barrier properties, and weatherability, and is less apt to undergo hydrolysis even when used outdoors for long. <P>SOLUTION: The backsheet for a solar cell comprises a resin layer (B) as a base material layer, a resin layer (A) laminated on one side of the resin layer (B), a resin layer (C) laminated on the other side of the resin layer (B), and a steam barrier layer D laminated on an external surface of the resin layer A or C, between the resin layers A, B, or between the resin layers B, C, the thickness (H<SB>A</SB>) of the resin layer A, the thickness (H<SB>B</SB>) of the resin layer B, and the thickness (H<SB>C</SB>) of the resin layer C satisfying the following expressions (1) and (2). The backsheet for the solar cell has a dimensional change ratio of ±1% or below through 30-minute standing at 150°C and has a reflectance of 50% or higher as measured with light having wavelengths of 400-1,400 nm. expression (1): 0.5≤H<SB>A</SB>/H<SB>C</SB>≤1.3, expression (2): 0.4≤(H<SB>A</SB>+H<SB>C</SB>)/H<SB>B</SB>≤2.4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a solar cell backsheet having high light reflectivity, excellent heat resistance and water vapor barrier properties, excellent weather resistance, hydrolysis resistance and flexibility, and curling is suppressed. About.

In recent years, solar cells have been attracting attention as an energy supply means to replace petroleum, which causes global warming, and the demand for the solar cells is increasing. With increasing demand for solar cells, there is a demand for stable supply and cost reduction of parts such as solar cell backsheets, and demands for improving the power generation efficiency of solar cells are also increasing.
The solar cell backsheet is laminated on the sealing resin surface after sealing the silicon cell with a sealing resin such as ethylene vinyl acetate resin under the glass plate.

  Conventionally, as a back sheet for a solar cell, a sheet in which a white thermoplastic resin sheet is laminated on both sides of a polyester sheet is used in order to increase the reflectance of sunlight and increase the power generation efficiency of the solar cell. (Patent Documents 1 and 2).

  However, since the solar cell backsheet is laminated on the sealing resin surface of the solar cell as described above, the water vapor barrier prevents the water vapor from entering the sealing resin from the backsheet and deteriorating the silicon cells. It is also required to have sex.

JP 2006-270025 A JP 2007-177136 A

  The present invention has a high light reflectance, a white color, low thermal deformation and excellent heat resistance, and is resistant to hydrolysis even when used outdoors for a long period of time. A solar cell backsheet that has excellent water vapor barrier properties, is difficult to break even in the form of a film, has excellent flexibility, has excellent workability, productivity, and handleability, and curling is suppressed. For the purpose of provision.

  As a result of diligent research to solve the above problems, the inventors of the present invention have a white laminate in which three resin layers are laminated and a water vapor barrier layer is provided, satisfying a specific dimensional change rate, and each layer. When the thickness of the film satisfies a predetermined relationship, the light reflectance is high, the water vapor barrier property and the heat resistance are excellent, the hydrolysis is difficult to occur even when used outdoors for a long time, and the Generation | occurrence | production was also prevented and it discovered that the laminated body excellent in flexibility can be obtained, and came to complete this invention.

That is, the present invention
A resin layer (B) which is a base material layer;
A resin layer (A) laminated on one side of the resin layer (B);
A resin layer (C) laminated on the other side of the resin layer (B);
Laminated on the outer surface of the resin layer (A) or the resin layer (C), or between the resin layer (A) and the resin layer (B) or between the resin layer (B) and the resin layer (C). A water vapor barrier layer (D);
The thickness (H _A ) of the resin layer ( _A ), the thickness (H _B ) of the resin layer ( _B ), and the thickness (H _C ) of the resin layer ( _C ) are represented by the following formulas (1) and (2): ), A dimensional change rate when left at 150 ° C. for 30 minutes is ± 1% or less, and a solar cell backsheet having a reflectance of light having a wavelength of 400 to 1400 nm is 50% or more.
_{0.5 ≦ H A / H C ≦} 1.3 ... (1)
_{0.4 ≦ (H A + H C} ) / H B ≦ 2.4 ... (2)
Moreover, according to preferable embodiment of this invention, the solar cell module which comprises the said solar cell backsheet of this invention is provided.

The solar cell backsheet of the present invention is a white laminate in which three resin layers are laminated and a water vapor barrier layer is provided, which satisfies a specific rate of dimensional change and has a predetermined thickness. Therefore, it has high light reflectivity, excellent water vapor barrier properties and heat resistance, is resistant to hydrolysis even when used outdoors for a long time, has excellent weather resistance, prevents curling, and can be used. Excellent flexibility.
Moreover, since the back sheet for solar cells of this invention can be comprised as a molded resin layer, all three layers can manufacture easily.
Furthermore, in the solar cell backsheet of the present invention, a solar cell backsheet excellent in flame retardancy and scratch resistance is obtained by laminating the protective layer (E) as the outermost layer on the layer (C) side. Can do.

It is sectional drawing which shows preferable embodiment of the solar cell backsheet of this invention. It is sectional drawing which shows other preferable embodiment of the solar cell backsheet of this invention. It is sectional drawing which shows embodiment provided with the protective layer of the solar cell backsheet of FIG. It is sectional drawing which shows embodiment provided with the protective layer of the solar cell backsheet of FIG.

  The present invention will be described in detail below. In the present specification, “(co) polymerization” means homopolymerization and copolymerization, “(meth) acryl” means acryl and / or methacryl, and “(meth) acrylate” Means acrylate and / or methacrylate.

Base material layer of the present invention (resin layer (B))
The resin layer (B) constituting the base material layer of the solar battery back sheet of the present invention provides heat resistance for long-term use under irradiation of light such as sunlight, and at the same time after printing on the solar battery back sheet of the present invention. Even if it receives a large temperature history during drying, surface treatment, or other secondary processing, it has a function of keeping thermal shrinkage small. Moreover, this base material layer can be created by molding a resin containing a colorant or a resin not containing it as a film or sheet.

  As the thermoplastic resin (I) constituting the base material layer (hereinafter also referred to as “component (I)”), those having a low dimensional change rate are preferable. Specific examples include aromatic vinyl resins (for example, Styrene resin, rubber reinforced styrene resin, acrylonitrile / styrene resin, and (co) polymers obtained by polymerizing monomers containing aromatic vinyl compounds such as (co) polymers of aromatic vinyl compounds Resin), polyolefin resin (for example, polyethylene resin, polypropylene resin, ethylene-α-olefin resin, etc.), polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, saturated polyester resin, Polycarbonate resin, acrylic resin (for example, (co) polymer of (meth) acrylic acid ester compound), fluorine resin, ethylene -Vinyl acetate resin and the like can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

From the viewpoint of heat resistance, the thermoplastic resin (I) preferably has a glass transition temperature of 120 ° C. or higher, more preferably 120 to 220 ° C., still more preferably 130 to 190 ° C., and even more preferably 140 to 170 ° C. Even more preferably, 145 to 160 ° C. is particularly preferable. When the glass transition temperature is less than 120 ° C., the heat resistance is not sufficient.
When the thermoplastic resin (I) has a plurality of glass transition temperatures, the higher temperature is set as the glass transition temperature of the thermoplastic resin (I). For example, when the thermoplastic resin (I) is a resin containing a resin component and a rubber component, the thermoplastic resin (I) has a glass transition temperature of the resin component and a glass transition temperature of the rubber component. Usually, since the glass transition temperature of the resin component is higher, the glass transition temperature of the resin component is set as the glass transition temperature of the thermoplastic resin (I).

As the thermoplastic resin (I), typically, an aromatic vinyl resin (I-1), for example, a monomer (ii) containing an aromatic vinyl compound in the presence of a rubbery polymer (i). A rubber-reinforced aromatic vinyl resin (I-1-1) obtained by polymerizing styrene, a (co) polymer (I-1-2) of a monomer (ii) containing an aromatic vinyl compound, and rubber weight A rubber-reinforced aromatic vinyl resin (I-1-1) obtained by polymerizing a monomer (ii) containing an aromatic vinyl compound in the presence of the coalescence (i) and a monomer containing an aromatic vinyl compound ( and a mixture of (ii) the (co) polymer (I-1-2).
The (co) polymer (I-1-2) is obtained by polymerizing the monomer (ii) containing an aromatic vinyl compound in the absence of the rubbery polymer (i). The rubber-reinforced aromatic vinyl resin (I-1-1) usually includes a copolymer obtained by graft copolymerization of a monomer (ii) containing an aromatic vinyl compound with the rubbery polymer (i) and a rubbery material. The ungrafted component which is not grafted to the polymer [the same kind as the above (co) polymer (I-1-2)] is included. A preferred thermoplastic resin (I) is a rubber-reinforced aromatic vinyl resin (I-1) obtained by polymerizing a monomer (ii) containing an aromatic vinyl compound in the presence of the rubber polymer (i). -1) and optionally an aromatic vinyl resin (I-1) containing a (co) polymer (I-1-2) of a monomer (ii) containing an aromatic vinyl compound.

  The aromatic vinyl resin (I-1) in the present invention preferably contains at least one rubber-reinforced aromatic vinyl resin (I-1-1) from the viewpoint of impact resistance and flexibility. May contain the (co) polymer (I-1-2). The content of the rubbery polymer (i) is preferably 5 to 40 parts by mass, more preferably 8 to 30 parts by mass, and still more preferably 10 to 100 parts by mass of the aromatic vinyl resin (I-1). 20 parts by mass, particularly preferably 12 to 18 parts by mass. If the content of the rubbery polymer (i) exceeds 40 parts by mass, the heat resistance may not be sufficient, and film processing may be difficult. On the other hand, if the content of the rubbery polymer (i) is less than 5 parts by mass, the impact resistance and flexibility may not be sufficient.

  In addition, the aromatic vinyl resin (I-1) is preferably made of a polymer obtained by polymerizing a monomer (ii) containing an aromatic vinyl compound by further containing a maleimide compound from the viewpoint of heat resistance. The content of the repeating unit derived from the maleimide compound with respect to 100% by mass of the aromatic vinyl resin (I-1) is usually preferably 0 to 30% by mass, and preferably 1 to 30% by mass. Is more preferable, it is still more preferable that it is 5-27 mass%, it is still more preferable that it is 10-27 mass%, and it is especially preferable that it is 15-25 mass%. When the content of the repeating unit derived from the maleimide compound is less than 1% by weight, the heat resistance may be insufficient, and when it exceeds 30% by mass, the flexibility of the solar cell backsheet is insufficient. There is a possibility. Moreover, even if the repeating unit derived from the maleimide compound is derived from the rubber-reinforced aromatic vinyl resin (I-1-1), the (co) polymer (I-1-2) It may be derived. As will be described later, the glass transition temperature of the aromatic vinyl resin (I-1) can be adjusted by the content of the repeating unit derived from the maleimide compound, and the repetition derived from the maleimide compound. The (co) polymer (I-1-2) containing units is convenient for preparing an aromatic vinyl resin (I-1) having a desired glass transition temperature.

The rubbery polymer (i) is not particularly limited, but conjugated diene rubber such as polybutadiene, butadiene / styrene random copolymer, butadiene / styrene block copolymer, butadiene / acrylonitrile copolymer, and hydrogenated product thereof. (That is, hydrogenated conjugated diene rubber), non-diene rubbers such as ethylene-α-olefin rubber, acrylic rubber, silicone rubber, and silicone / acrylic composite rubber, which are used alone or in combination Two or more kinds can be used in combination.
Among these, from the viewpoint of weather resistance, ethylene-α-olefin rubber (i-1), hydrogenated conjugated diene rubber (i-2), acrylic rubber (i-3), silicone rubber (i-4) ) And silicone / acrylic composite rubber (i-5) are preferred, and among these, acrylic rubber (i-3), silicone rubber (i-4) and silicone / acrylic composite rubber (i-5) are more preferred, Silicone / acrylic composite rubber (i-5) is particularly preferred from the viewpoint of flexibility. In addition, these can be used individually by 1 type or in combination of 2 or more types.

  Examples of the ethylene-α-olefin rubber (i-1) include an ethylene-α-olefin copolymer and an ethylene-α-olefin-nonconjugated diene copolymer. Examples of the α-olefin constituting the ethylene-α-olefin rubber (i-1) include α-olefins having 3 to 20 carbon atoms. Specifically, propylene, 1-butene, 1- Examples include pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadecene and 1-eicosene. These α-olefins can be used alone or in admixture of two or more. The carbon number of the α-olefin is preferably 3 to 20, more preferably 3 to 12, and still more preferably 3 to 8. If the number of carbon atoms exceeds 20, the copolymerizability is lowered and the surface appearance of the molded product may not be sufficient. Typical ethylene-α-olefin rubbers (i-1) include ethylene / propylene copolymers, ethylene / propylene / nonconjugated diene copolymers, ethylene / butene-1 copolymers, and ethylene / butene-1. -Non-conjugated diene copolymers are exemplified. The mass ratio of ethylene / α-olefin is preferably 5 to 95/95 to 5, more preferably 50 to 90/50 to 10, still more preferably 60 to 88/40 to 12, and particularly preferably 70 to 85/30. ~ 15. When the α-olefin mass ratio exceeds 95, the weather resistance is not sufficient. On the other hand, when the α-olefin mass ratio is less than 5, the rubber elasticity of the rubbery polymer is not sufficient, and the flexibility as a film may not be sufficient. There is.

Non-conjugated dienes include alkenyl norbornenes, cyclic dienes and aliphatic dienes, with 5-ethylidene-2-norbornene and dicyclopentadiene being preferred. These non-conjugated dienes can be used alone or in admixture of two or more. The ratio of the nonconjugated diene to the total amount of the ethylene-α-olefin rubber (i-1) is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and further preferably 0 to 10% by mass. If the proportion of non-conjugated diene exceeds 30% by mass, the molded appearance and weather resistance may not be sufficient. In addition, the amount of unsaturated groups in the ethylene-α-olefin rubber (i-1) is preferably in the range of 4 to 40 in terms of iodine value.
The Mooney viscosity (ML _{1 + 4} , 100 ° C .; conforming to JIS K6300) of the ethylene-α-olefin rubber (i-1) is preferably 5 to 80, more preferably 10 to 65, and still more preferably 15 to 45. When the Mooney viscosity of the component (i-1) exceeds 80, polymerization becomes difficult. On the other hand, when the Mooney viscosity is less than 5, impact resistance and flexibility as a film may be insufficient. .

  Examples of the hydrogenated conjugated diene rubber (i-2) include hydrogenated products of conjugated diene block copolymers having the following structure. That is, the polymer block A composed of aromatic vinyl compound units and the double bond portion of the polymer composed of conjugated diene compound units having a 1,2-vinyl bond content exceeding 25 mol% are hydrogenated at 95 mol% or more. Polymer block B, polymer block C formed by hydrogenating 95 mol% or more of a double bond portion of a polymer comprising a conjugated diene compound unit having a 1,2-vinyl bond content of 25 mol% or less, and an aroma A block copolymer comprising a combination of two or more of polymer blocks D obtained by hydrogenating 95 mol% or more of the double bond portion of a copolymer of an aromatic vinyl compound unit and a conjugated diene compound unit. is there.

  Examples of the aromatic vinyl compound used in the production of the polymer block A include styrene, α-methylstyrene, methylstyrene, vinylxylene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, fluorostyrene, pt- Examples thereof include butyl styrene, ethyl styrene and vinyl naphthalene, and these can be used alone or in combination of two or more. Of these, styrene is preferred. The proportion of the polymer block A in the block copolymer is preferably 0 to 65% by mass, more preferably 10 to 40% by mass in the block copolymer. When the polymer block A exceeds 65% by mass, the impact resistance may not be sufficient.

  The polymer blocks B, C and D can be obtained by hydrogenating a polymer of a conjugated diene compound. Examples of the conjugated diene compounds used for the production of the polymer blocks B, C and D include 1,3-butadiene, isoprene, 1,3-pentadiene, chloroprene, etc., but can be used industrially and have physical properties. In order to obtain an excellent hydrogenated conjugated diene rubber (i-2), 1,3-butadiene and isoprene are preferred. These can be used individually by 1 type or in mixture of 2 or more types. Examples of the aromatic vinyl compound used in the production of the polymer block D include the same aromatic vinyl compounds used in the production of the polymer block A, and these may be used alone or in combination of two types. The above can be mixed and used. Of these, styrene is preferred.

  The hydrogenation rate of the polymer blocks B, C and D is 95 mol% or more, preferably 96 mol% or more. If it is less than 95 mol%, gelation may occur during the polymerization, and the polymerization may not be stably performed. The 1,2-vinyl bond content of the polymer block B is preferably more than 25 mol% and 90 mol% or less, and more preferably 30 to 80 mol%. If the 1,2-vinyl bond content of the polymer block B is 25 mol% or less, rubber properties may be lost and impact resistance may not be sufficient, whereas if it exceeds 90 mol%, chemical resistance May not be sufficient. Further, the 1,2-vinyl bond content of the polymer block C is preferably 25% by mole or less, and more preferably 20% by mole or less. When the 1,2-vinyl bond content of the polymer block C exceeds 25 mol%, scratch resistance and sliding properties may not be sufficiently exhibited. The 1,2-vinyl bond content of the polymer block D is preferably 25 to 90 mol%, more preferably 30 to 80 mol%. If the 1,2-vinyl bond content of the polymer block D is less than 25 mol%, rubber properties may be lost and impact resistance may not be sufficient. On the other hand, if it exceeds 90 mol%, May not be sufficient. The content of the aromatic vinyl compound in the polymer block D is preferably 25% by mass or less, and more preferably 20% by mass or less. If the content of the aromatic vinyl compound in the polymer block D exceeds 25% by mass, the rubbery properties are lost and the impact resistance may not be sufficient.

  The molecular structure of the block copolymer may be branched, radial, or a combination thereof, and the block structure may be a diblock, a triblock, a multiblock, or a combination thereof. For example, A- (BA) n, (AB) n, A- (BC) n, C- (BC) n, (BC) n, A- (DA) n, (AD) n, A- (DC) n, C- (DC) n, (DC) n, A- (BCDD), (AB) (C-D) n, where n is an integer of 1 or more, preferably ABA, ABBA, ABBC, It is a block copolymer having a structure of A-D-C or C-B-C.

  The weight average molecular weight (Mw) of the hydrogenated conjugated diene rubber (i-2) is preferably 10,000 to 1,000,000, more preferably 30,000 to 800,000, and more preferably 50,000 to 500,000. If Mw is less than 10,000, flexibility as a film may not be sufficient, while if it exceeds 1 million, polymerization becomes difficult.

  The acrylic rubber (i-3) is a polymer of alkyl acrylate having 2 to 8 carbon atoms in the alkyl group. Specific examples of the alkyl acrylate include ethyl acrylate, propyl acrylate, Examples include n-butyl acrylate, isobutyl acrylate, hexyl acrylate, n-octyl acrylate, and 2-ethylhexyl acrylate. These can be used alone or in combination of two or more. Preferred alkyl acrylates are (n-, i) -butyl acrylate or 2-ethylhexyl acrylate. In addition, a part of acrylic acid alkyl ester can be substituted by another monomer which can be copolymerized up to 20% by mass. Examples of the other monomer include vinyl chloride, vinylidene chloride, acrylonitrile, vinyl ester, alkyl methacrylate ester, methacrylic acid, acrylic acid, and styrene.

  For the acrylic rubber (i-3), it is preferable to select the type of monomer and the amount of copolymerization so that the glass transition temperature thereof is −10 ° C. or lower. The acrylic rubber is preferably copolymerized with a crosslinkable monomer as appropriate, and the amount of the crosslinkable monomer used is usually 0 to 10% by mass, preferably 0 as a ratio in the acrylic rubber. 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass.

  Specific examples of the crosslinkable monomer include mono- or polyethylene glycol diacrylate such as ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol Mono- or polyethylene glycol dimethacrylate such as ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, diallyl maleate, diallyl succinate, triallyl triazine and other di- or triallyl compounds, allyl methacrylate, allyl acrylate, etc. Examples include allyl compounds and conjugated diene compounds such as 1,3-butadiene. It is. The acrylic rubber is produced by a known polymerization method, and a preferred polymerization method is an emulsion polymerization method.

  As the silicone rubber (i-4), any of those obtained by a known polymerization method can be used. From the viewpoint of ease of graft polymerization, a polyorganosiloxane rubber weight obtained by emulsion polymerization in a latex state can be used. Combined latex is preferred.

  The latex of the polyorganosiloxane rubber-like polymer can be obtained by a known method, for example, a method described in US Pat. Nos. 2,891,920 and 3,294,725. I can do it. For example, using a homomixer or an ultrasonic mixer, a method of shearing and mixing the organosiloxane and water in the presence of a sulfonic acid-based emulsifier such as alkylbenzene sulfonic acid or alkyl sulfonic acid can be mentioned. Alkylbenzenesulfonic acid is suitable because it acts as an emulsifier for organosiloxane and also as a polymerization initiator. In this case, it is preferable to use an alkylbenzene sulfonic acid metal salt, an alkyl sulfonic acid metal salt, or the like in combination because it has an effect of maintaining a stable polymer during graft polymerization. If necessary, a graft crossing agent or a crosslinking agent may be co-condensed within a range not impairing the target performance of the present invention.

The organosiloxane used is, for example, the general formula R _m SiO _{(4-m) / 2} (wherein R is a substituted or unsubstituted monovalent hydrocarbon group, and m represents an integer of 0 to 3). ) And has a linear, branched or cyclic structure, and is preferably an organosiloxane having a cyclic structure. Examples of the substituted or unsubstituted monovalent hydrocarbon group possessed by the organosiloxane include a methyl group, an ethyl group, a propyl group, a phenyl group, and a substituted hydrocarbon group obtained by substituting them with a cyano group. I can do it.

  Specific examples of the organosiloxane include, in addition to cyclic compounds such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and trimethyltriphenylcyclotrisiloxane, linear or A branched organosiloxane can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

  The organosiloxane may be a polyorganosiloxane condensed in advance, for example, having a polystyrene-reduced weight average molecular weight of about 500 to 10,000. Further, when the organosiloxane is a polyorganosiloxane, the molecular chain terminal may be blocked with, for example, a hydroxyl group, an alkoxy group, a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, or a methyldiphenylsilyl group. Good.

  As the graft crossing agent, for example, a compound having both an unsaturated group and an alkoxysilyl group can be used. Specific examples of such compounds include p-vinylphenylmethyldimethoxysilane, 1- (m-vinylphenyl) methyldimethylisopropoxysilane, 2- (p-vinylphenyl) ethylmethyldimethoxysilane, 3- (p-vinylphenoxy). ) Propylmethyldiethoxysilane, 3- (p-vinylbenzoyloxy) propylmethyldimethoxysilane, 1- (o-vinylphenyl) -1,1,2-trimethyl-2,2-dimethoxydisilane, 1- (p -Vinylphenyl) -1,1-diphenyl-3-ethyl-3,3-diethoxydisiloxane, m-vinylphenyl- [3- (triethoxysilyl) propyl] diphenylsilane, [3- (p-isopropenyl) Benzoylamino) propyl] phenyldipropoxysilane, 2- (m-vinylpheny E) ethylmethyldimethoxysilane, 2- (o-vinylphenyl) ethylmethyldimethoxysilane, 1- (p-vinylphenyl) ethylmethyldimethoxysilane, 1- (m-vinylphenyl) ethylmethyldimethoxysilane, 1- (o -Vinylphenyl) ethylmethyldimethoxysilane and the like, and mixtures thereof. Among these, p-vinylphenylmethyldimethoxysilane, 2- (p-vinylphenyl) ethylmethyldimethoxysilane, and 3- (p-vinylbenzoyloxy) propylmethyldimethoxysilane are preferable, and p-vinylphenylmethyldimethoxysilane is preferred. Is more preferable.

  The proportion of the grafting agent used is usually 0 to 10 parts by mass, preferably 0.2 to 10 parts by mass, more preferably 0.5 to 100 parts by mass with respect to 100 parts by mass of the total amount of the organosiloxane, the grafting agent and the crosslinking agent. 5 parts by mass. When the amount of the grafting agent used is large, the molecular weight of the grafted vinyl polymer is lowered, and as a result, sufficient impact resistance cannot be obtained. Further, oxidative deterioration is more likely to proceed than the double bond of the polyorganosiloxane rubber polymer after grafting, and a graft copolymer having good weather resistance cannot be obtained.

  The average particle diameter of the polyorganosiloxane rubber-like polymer latex particles is usually 0.5 μm or less, preferably 0.4 μm or less, and more preferably 0.05 to 0.4 μm. This average particle size can be easily controlled by the amount of the emulsifier and water, the degree of dispersion when mixed using a homomixer or an ultrasonic mixer, or the method of charging the organosiloxane. When the average particle diameter of the latex particles exceeds 0.5 μm, the gloss is inferior.

  Moreover, the polystyrene conversion weight average molecular weight of the polyorganosiloxane rubber polymer obtained as described above is usually 30,000 to 1,000,000, preferably 50,000 to 300,000. When the weight average molecular weight is less than 30,000, there is a possibility that sufficient flexibility as a film cannot be obtained. On the other hand, when the weight average molecular weight exceeds 1,000,000, the entanglement between the polymer chains of the rubber becomes strong and the rubber elasticity is lowered, so that the flexibility as a film is lowered and the graft particles are hardly melted. The film appearance may be damaged.

  The weight average molecular weight can be easily adjusted by changing the condensation polymerization temperature and time during preparation of the polyorganosiloxane rubbery polymer. That is, the lower the condensation polymerization temperature and / or the longer the cooling time, the higher the polymer. Moreover, a polymer can be made high molecular weight also by adding a small amount of a crosslinking agent.

  The molecular chain terminal of the polyorganosiloxane rubber polymer may be blocked with, for example, a hydroxyl group, an alkoxy group, a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, or a methyldiphenylsilyl group.

  The use amount of the emulsifier is usually 0.1 to 5 parts by mass, preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the total amount of the organosiloxane, the grafting agent and the crosslinking agent. In addition, the usage-amount of water in this case is 100-500 mass parts normally with respect to 100 mass parts of total amounts of organosiloxane, a graft crossing agent, and a crosslinking agent, Preferably it is 200-400 mass parts. The condensation temperature is usually 5 to 100 ° C.

  In the production of the polyorganosiloxane rubber polymer, a crosslinking agent can be added as a third component in order to improve the impact resistance of the resulting graft copolymer. Examples of this crosslinking agent include trifunctional crosslinking agents such as methyltrimethoxysilane, phenyltrimethoxysilane, and ethyltriethoxysilane, and tetrafunctional crosslinking agents such as tetraethoxysilane. Two or more of these can be used in combination. Moreover, you may use the crosslinked prepolymer prepolymerized by condensation as these crosslinking agents. The addition amount of the crosslinking agent is usually 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the total amount of the organosiloxane, the grafting agent and the crosslinking agent. is there. When the addition amount of the cross-linking agent exceeds 10 parts by mass, the flexibility of the polyorganosiloxane rubber-like polymer is impaired, so that the flexibility of the film may be lowered.

  The silicone / acrylic composite rubber (i-5) refers to a rubbery polymer containing a polyorganosiloxane rubber and a polyalkyl (meth) acrylate rubber. Preferred silicone-acrylic composite rubber (i-5) is a composite rubber having a structure in which polyorganosiloxane rubber and polyalkyl (meth) acrylate rubber are intertwined with each other so that they cannot be separated.

  Examples of the polyalkyl (meth) acrylate rubber include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, ethoxyethoxyethyl acrylate, methoxytripropylene glycol acrylate, and 4-hydroxybutyl acrylate. And those obtained by copolymerizing alkyl (meth) acrylates (monomers) such as lauryl methacrylate and stearyl methacrylate. These alkyl (meth) acrylates can be used alone or in combination of two or more.

  Further, in the monomer of the alkyl (meth) acrylate, aromatic vinyl compounds such as styrene, α-methylstyrene and vinyltoluene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; methacrylic acid-modified silicone, fluorine-containing Various vinyl monomers such as vinyl compounds may be included as a copolymerization component in the range of 30% by mass or less.

  The polyalkyl (meth) acrylate rubber is preferably a copolymer having two or more glass transition temperatures. Such a polyalkyl (meth) acrylate rubber is preferable for exhibiting flexibility in the film.

  As said polyorganosiloxane rubber, what copolymerized organosiloxane can be used. Examples of the organosiloxane include various reduced products having three or more members, preferably hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrimethyl. Examples thereof include siloxane, tetramethyltetraphenylcyclotetrasiloxane, and octaphenylcyclotetrasiloxane. These organosiloxanes can be used alone or in admixture of two or more. The amount of these organosiloxanes used is preferably 50% by mass or more, more preferably 70% by mass or more in the polyorganosiloxane rubber component.

  The silicone / acrylic composite rubber (i-5) can be produced, for example, by the method described in JP-A-4-239010, Japanese Patent No. 2137934, and the like. As such a silicone / acrylic composite rubber graft copolymer, for example, “Metablene SX-006 (trade name)” manufactured by Mitsubishi Rayon Co., Ltd. is commercially available.

  The monomer (ii) containing an aromatic vinyl compound in the present invention typically includes a monomer (ii) consisting only of an aromatic vinyl compound, both an aromatic vinyl compound and a vinyl cyanide compound. A monomer (ii) is mentioned and what contains both an aromatic vinyl compound and a vinyl cyanide compound is preferable.

  Examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, vinyltoluene, vinylxylene, ethylstyrene, dimethylstyrene, p-tert-butylstyrene, vinylnaphthalene, methoxystyrene, Examples thereof include monobromostyrene, dibromostyrene, tribromostyrene, and fluorostyrene. Of these, styrene and α-methylstyrene are preferred. Moreover, these aromatic vinyl compounds can be used individually by 1 type or in combination of 2 or more types.

  Examples of the vinyl cyanide compound include acrylonitrile, methacrylonitrile, α-chloro (meth) acrylonitrile and the like. Of these, acrylonitrile is preferred. Moreover, these vinyl cyanide compounds can be used individually by 1 type or in combination of 2 or more types.

  In addition, the monomer (ii) containing an aromatic vinyl compound may contain another compound copolymerizable with an aromatic vinyl compound or a vinyl cyanide compound. Such other compounds include (meth) acrylic acid esters, maleimide compounds, other functional group-containing unsaturated compounds (for example, unsaturated acids, epoxy group-containing unsaturated compounds, hydroxyl group-containing unsaturated compounds, oxazoline group-containing) Unsaturated compounds, acid anhydride group-containing unsaturated compounds, and the like). These can be used individually by 1 type or in combination of 2 or more types. The amount of the other compound used is preferably 0 to 50% by mass, more preferably 1 to 40% by mass, and further preferably 1 to 30%, based on 100% by mass of the monomer (ii) containing the aromatic vinyl compound. % By mass.

  (Meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, (meth ) Isobutyl acrylate and the like. These can be used individually by 1 type or in combination of 2 or more types. Of these, methyl methacrylate is preferred.

  Examples of the unsaturated acid include acrylic acid, methacrylic acid, itaconic acid, maleic acid and the like. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of maleimide compounds include maleimide, N-methylmaleimide, N-butylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide and the like. These can be used individually by 1 type or in combination of 2 or more types. In order to introduce a maleimide compound unit into the copolymer resin, maleic anhydride may be (co) polymerized and post-imidized. It is preferable to contain a maleimide compound as another copolymerizable compound from the viewpoint of improving the heat resistance of the thermoplastic resin (I).

  The content of the maleimide compound is usually preferably 0 to 30% by mass as the content of the repeating unit derived from the maleimide compound with respect to 100% by mass of the thermoplastic resin (I). It is more preferably 30% by mass, even more preferably 5 to 27% by mass, still more preferably 10 to 27% by mass, and particularly preferably 15 to 25% by mass. When the content of the repeating unit derived from the maleimide compound is less than 1% by mass, the heat resistance may be insufficient, and when it exceeds 30% by mass, the flexibility of the solar cell backsheet is insufficient. There is a possibility.

  Examples of the epoxy group-containing unsaturated compound include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of the hydroxyl group-containing unsaturated compound include 3-hydroxy-1-propene, 4-hydroxy-1-butene, cis-4-hydroxy-2-butene, trans-4-hydroxy-2-butene, and 3-hydroxy-2. -Methyl-1-propene, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxystyrene and the like. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of the oxazoline group-containing unsaturated compound include vinyl oxazoline. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of the acid anhydride group-containing unsaturated compound include maleic anhydride, itaconic anhydride, citraconic anhydride, and the like. These can be used individually by 1 type or in combination of 2 or more types.

  As the monomer (ii) containing an aromatic vinyl compound, those containing mainly an aromatic vinyl compound and a vinyl cyanide compound are preferable, and the total amount of these compounds is a monomer containing an aromatic vinyl compound ( ii) Preferably it is 70-100 mass% with respect to the whole quantity, More preferably, it is 80-100 mass%. The use ratio of the aromatic vinyl compound and the vinyl cyanide compound is preferably 5 to 95% by mass and more preferably 5 to 95% by mass, and more preferably 50 to 95% by mass, when the total of these is 100% by mass. % And 5 to 50% by mass, still more preferably 60 to 95% by mass and 5 to 40% by mass, particularly preferably 65 to 85% by mass and 15 to 35% by mass.

  According to a preferred embodiment of the present invention, the thermoplastic resin (I) is selected from the group consisting of acrylic rubber (i-3), silicone rubber (i-4) and silicone / acrylic composite rubber (i-5). A rubber-reinforced aromatic vinyl resin (I-1-1 ') obtained by polymerizing a monomer (ii) containing an aromatic vinyl compound in the presence of the selected rubbery polymer (i), and optionally A rubber-reinforced aromatic vinyl resin composed of a (co) polymer (I-1-2 ′) of a monomer (ii) containing an aromatic vinyl compound is used. Among them, a silicone / acrylic composite rubber reinforced styrene resin using a silicone / acrylic composite rubber (i-5) as the rubbery polymer (i), and a silicone rubber (i-4) as the rubbery polymer (i). And a mixture of a silicone rubber reinforced styrene resin using an acrylic rubber (i-3) as a rubbery polymer (i), and a silicone / acrylic composite rubber. Reinforced styrene resin is particularly preferable.

  The rubber-reinforced aromatic vinyl resin (I-1-1) can be obtained by a known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, or a polymerization method combining these.

  The graft ratio of the rubber-reinforced aromatic vinyl resin (I-1-1) is preferably 20 to 170%, more preferably 30 to 170%, and still more preferably 40 to 150%. If this graft ratio is too low, flexibility as a film may not be sufficient. On the other hand, when the graft ratio is too high, the viscosity of the thermoplastic resin increases, and it may be difficult to reduce the thickness.

The graft ratio can be determined by the following formula (4).
Graft rate (mass%) = ((S−T) / T) × 100 (4)
In the above formula, S represents 1 gram of rubber-reinforced aromatic vinyl resin (I-1-1) in 20 ml of acetone (acetonitrile in the case of acrylic rubber) and is shaken under a temperature condition of 25 ° C. After shaking for 2 hours, the mixture is centrifuged for 60 minutes in a centrifuge (rotation speed: 23,000 rpm) under a temperature condition of 5 ° C., and the mass of the insoluble matter obtained by separating the insoluble matter and the soluble matter. (G), and T is the mass (g) of the rubbery polymer contained in 1 gram of the rubber-reinforced aromatic vinyl resin (I-1-1). The mass of the rubbery polymer can be obtained by a method of calculating from a polymerization prescription and a polymerization conversion rate, a method of obtaining from an infrared absorption spectrum (IR), and the like.

  The graft ratio is, for example, the type and amount of chain transfer agent used during the production of the rubber-reinforced aromatic vinyl resin (I-1-1), the type and amount of polymerization initiator, and the monomer during polymerization. It can adjust by selecting suitably the addition method and addition time of a component, polymerization temperature, etc.

  The intrinsic viscosity [η] (in methyl ethyl ketone, 30 ° C.) of the acetone-soluble component (acetonitrile-soluble component in the case of acrylic rubber) of the rubber-reinforced aromatic vinyl resin (I-1-1) is preferably 0.00. It is 1-2.5 dl / g, More preferably, it is 0.2-1.5 dl / g, More preferably, it is 0.25-1.2 dl / g. It is preferable that the intrinsic viscosity is within this range from the viewpoint of obtaining a solar cell backsheet having high film processability and high thickness accuracy.

  The intrinsic viscosity [η] of the acetone-soluble component (acetonitrile-soluble component in the case of acrylic rubber) of the rubber-reinforced aromatic vinyl resin (I-1-1) was measured by the following method. First, the acetone-soluble component of the rubber-reinforced aromatic vinyl resin (I-1-1) (acetonitrile-soluble component in the case of acrylic rubber) was dissolved in methyl ethyl ketone to prepare five samples having different concentrations. The intrinsic viscosity [η] was determined from the results of measuring the reduced viscosity of each concentration at 30 ° C. using an Ubbelohde viscosity tube. The unit is dl / g.

  The intrinsic viscosity [η] is, for example, the type and amount of chain transfer agent used during the production of the rubber-reinforced aromatic vinyl resin (I-1-1), the type and amount of polymerization initiator, It can adjust by selecting suitably the addition method and addition time of a monomer component, polymerization temperature, etc. Moreover, it can adjust by selecting and mix | blending the said (co) polymer (I-1-2) which has different intrinsic viscosity [(eta)] suitably.

  The thermoplastic resin (I) may be used by blending the necessary parts of each component in advance, mixing with a Henschel mixer, etc., melting and kneading with an extruder, and pelletizing each component. Or you may supply directly to an extruder and may perform a film process or a sheet process. At this time, the thermoplastic resin (I) includes an antioxidant, an ultraviolet absorber, a weathering agent, an anti-aging agent, a filler, an antistatic agent, a flame retardant, an antifogging agent, a lubricant, an antibacterial agent, and an antifungal agent. , Tackifiers, plasticizers, colorants, graphite, carbon black, carbon nanotubes, pigments (for example, pigments having infrared absorption and reflection capabilities, and functionalities) are not impaired. It can also be added in a range.

Resin layer of the present invention (resin layer (A))
Although it does not restrict | limit especially as a resin component which comprises a resin layer (A), The thermoplastic resin (II) is preferable from the point of the moldability of a solar cell backsheet. Further, the thermoplastic resin (II) may have a glass transition temperature lower than that of the thermoplastic resin (I) constituting the resin layer (B) from the viewpoint of imparting flexibility to the solar cell backsheet. preferable. The glass transition temperature of the thermoplastic resin (II) is preferably 90 to 200 ° C, more preferably 95 to 160 ° C, still more preferably 95 to 150 ° C, and particularly preferably 110 to 140 ° C. When the glass transition temperature of the thermoplastic resin (II) is higher than 200 ° C., the flexibility of the solar cell backsheet tends to be deteriorated. On the other hand, when the glass transition temperature is lower than 90 ° C., the heat resistance is increased. Tends to be insufficient.
When the thermoplastic resin (II) has a plurality of glass transition temperatures, the higher temperature is set as the glass transition temperature of the thermoplastic resin (I). For example, when the thermoplastic resin (II) is a resin containing a resin component and a rubber component, the thermoplastic resin (II) has a glass transition temperature of the resin component and a glass transition temperature of the rubber component. Usually, since the glass transition temperature of the resin component is higher, the glass transition temperature of the resin component is set as the glass transition temperature of the thermoplastic resin (II).

  Examples of the thermoplastic resin (II) include aromatic vinyl resins (for example, rubber-reinforced styrene resins, acrylonitrile / styrene resins, (co) polymers of other aromatic vinyl compounds), polyolefin resins ( For example, polyethylene resin, polypropylene resin, ethylene-α-olefin resin, etc.), polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, saturated polyester resin (for example, polyethylene terephthalate, polybutylene) Terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, etc.), polycarbonate resins, acrylic resins (eg, (co) polymers of (meth) acrylate compounds), fluorine resins, ethylene / vinyl acetate resins, etc. Is mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among these, it is preferable to use the aromatic vinyl resin (II-1) from the viewpoint that hydrolysis does not easily occur even when used outdoors for a long period of time.

  The aromatic vinyl resin (II-1) (hereinafter also referred to as “component (II-1)”) used in the present invention is typically aromatic in the presence of the rubbery polymer (a). A rubber-reinforced aromatic vinyl resin (II) obtained by polymerizing a monomer containing a vinyl compound (that is, an aromatic vinyl compound and optionally another monomer copolymerizable with the aromatic vinyl compound) (b) -1-1), (co) polymer (II-1-2) of monomer (b) containing an aromatic vinyl compound, and resin (II-1-1) and (co) polymer (II-1) -2). The latter (co) polymer (II-1-2) is obtained by polymerizing the monomer (b) containing an aromatic vinyl compound in the absence of the rubbery polymer (a). . In the rubber-reinforced aromatic vinyl resin (II-1-1), a copolymer obtained by graft-copolymerizing a monomer (b) containing an aromatic vinyl compound to a rubber polymer (a) and a rubber material are usually used. The ungrafted component which is not grafted to the polymer [the same as the above (co) polymer (II-1-2)] is included.

  The aromatic vinyl resin (II-1) in the present invention preferably contains at least one rubber-reinforced aromatic vinyl resin (II-1-1) from the viewpoint of impact resistance and flexibility. If desired, the (co) polymer (II-1-2) may be contained. The content of the rubber polymer (a) is preferably 5 to 40 parts by mass, more preferably 8 to 30 parts by mass, and still more preferably 10 to 10 parts by mass, with the aromatic vinyl resin (II-1) being 100 parts by mass. 20 parts by mass, particularly preferably 12 to 18 parts by mass. If the content of the rubbery polymer (a) exceeds 40 parts by mass, the heat resistance may not be sufficient and film processing may be difficult. On the other hand, when the content of the rubbery polymer (a) is less than 5 parts by mass, the flexibility may not be sufficient.

  As the rubber polymer (a), those described as the rubber polymer (i) can be used, and the preferable rubber polymer (a) is the same as the rubber polymer (i). However, in the solar cell backsheet of the present invention, the rubbery polymer (a) used in the aromatic vinyl resin (II-1) is the rubbery polymer (i) used in the thermoplastic resin (I). May be the same or different.

  As the monomer (b) containing an aromatic vinyl compound, those described as the monomer (ii) containing an aromatic vinyl compound can be used, and a monomer (b) containing a preferred aromatic vinyl compound can be used. Is the same as the monomer (ii) containing the aromatic vinyl compound. However, in the solar cell backsheet of the present invention, the monomer (b) containing the aromatic vinyl compound used in the aromatic vinyl resin (II-1) is the aromatic used in the thermoplastic resin (I). It may be the same as or different from the monomer (ii) containing a vinyl compound.

  The aromatic vinyl resin (II-1) preferably contains a repeating unit derived from a maleimide compound from the viewpoint of heat resistance, and the aromatic vinyl resin (II-1) is 100% by mass. The content of the repeating unit derived from the maleimide compound is usually preferably 0 to 30% by mass, more preferably 1 to 30% by mass, and even more preferably 5 to 25% by mass. Preferably, it is 10-20 mass%, and it is especially preferable. The repeating unit derived from the maleimide compound may be derived from the rubber-reinforced aromatic vinyl resin (II-1-1) or derived from the (co) polymer (II-1-2). It may be. The glass transition temperature of the aromatic vinyl resin (II-1) can be adjusted by the content of the repeating unit derived from the maleimide compound, as will be described later. The contained (co) polymer (II-1-2) is convenient for preparing an aromatic vinyl resin (II-1) having a desired glass transition temperature.

  According to a preferred embodiment of the present invention, the thermoplastic resin (II) is selected from the group consisting of acrylic rubber (i-3), silicone rubber (i-4) and silicone / acrylic composite rubber (i-5). A rubber-reinforced aromatic vinyl resin (II-1-1) obtained by polymerizing a monomer (b) containing an aromatic vinyl compound in the presence of the selected rubbery polymer (a) and, if desired, the fragrance An aromatic vinyl resin comprising a (co) polymer (II-1-2) of a monomer (b) containing an aromatic vinyl compound is used. Among them, a silicone / acrylic composite rubber reinforced styrene resin using a silicone / acrylic composite rubber (i-5) as the rubbery polymer (b), and a silicone rubber (i-4) as the rubbery polymer (b). ) Is preferably a mixture of a silicone rubber-reinforced styrene resin using acryl-based rubber and an acrylic rubber-reinforced styrene resin using acrylic rubber (i-3) as the rubbery polymer (b). Reinforced styrene resin is particularly preferable.

  The aromatic vinyl resin (II-1) can be obtained by a known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, or a polymerization method combining these.

  The graft ratio of the rubber-reinforced aromatic vinyl resin (II-1-1) is preferably 20 to 170%, more preferably 30 to 170%, and still more preferably 40 to 150%. If this graft ratio is too low, flexibility as a film may not be sufficient. On the other hand, when the graft ratio is too high, the viscosity of the thermoplastic resin increases, and it may be difficult to reduce the thickness.

  The graft ratio can be measured by the same method as described for the rubber-reinforced aromatic vinyl resin (I-1-1).

  The graft ratio is, for example, the type and amount of chain transfer agent used during the production of the rubber-reinforced aromatic vinyl resin (II-1-1), the type and amount of polymerization initiator, and the monomer during polymerization. It can adjust by selecting suitably the addition method and addition time of a component, polymerization temperature, etc.

  The intrinsic viscosity [η] (in methyl ethyl ketone, 30 ° C.) of the acetone-soluble component (acetonitrile-soluble component in the case of acrylic rubber) of the rubber-reinforced aromatic vinyl resin (II-1-1) is preferably 0.00. It is 1-2.5 dl / g, More preferably, it is 0.2-1.5 dl / g, More preferably, it is 0.25-1.2 dl / g. It is preferable that the intrinsic viscosity is within this range from the viewpoint of obtaining a solar cell backsheet with high wall thickness accuracy.

  The intrinsic viscosity [η] can be measured in the same manner as the measurement performed with the rubber-reinforced aromatic vinyl resin (I-1-1).

  The intrinsic viscosity [η] is, for example, the type and amount of chain transfer agent used in the production of rubber-reinforced aromatic vinyl resin (II-1-1), the type and amount of polymerization initiator, It can be adjusted by appropriately selecting the addition method and addition time of the monomer component, the polymerization temperature and the like. Moreover, it can adjust by selecting suitably and mixing the (co) polymer (II-1-2) which has different intrinsic viscosity [(eta)].

  Aromatic vinyl resin (II-1) may be used by blending the required parts of each component in advance, mixing with a Henschel mixer, etc., melting and kneading with an extruder, and pelletizing. May be directly supplied to a film molding machine or an extrusion molding machine to perform film processing or sheet processing. At this time, the aromatic vinyl resin (II-1) includes an antioxidant, an ultraviolet absorber, a weathering agent, an anti-aging agent, a filler, an antistatic agent, a flame retardant, an antifogging agent, a lubricant, an antibacterial agent, An antifungal agent, a tackifier, a plasticizer, a colorant, graphite, carbo black, a carbon nanotube, and the like can be added within a range that does not impair the object of the present invention.

Resin layer of the present invention (resin layer (C))
As a resin component which comprises a resin layer (C), what was mentioned above about the resin layer (A) can be used, and the thermoplastic resin (II) is preferable from the point of the moldability of the solar cell backsheet. Further, the thermoplastic resin (II) may have a glass transition temperature lower than that of the thermoplastic resin (I) constituting the resin layer (B) from the viewpoint of imparting flexibility to the solar cell backsheet. preferable. The glass transition temperature of the thermoplastic resin (II) is preferably 90 to 200 ° C, more preferably 95 to 160 ° C, still more preferably 95 to 150 ° C, and particularly preferably 110 to 140 ° C. When the glass transition temperature of the thermoplastic resin (II) is higher than 200 ° C., the flexibility of the solar cell backsheet tends to be deteriorated. On the other hand, when the glass transition temperature is lower than 90 ° C., the heat resistance is increased. Tends to be insufficient. In addition, all the description including the description of the preferable thermoplastic resin (II) mentioned above regarding the resin layer (A) is applied also to the resin component which comprises the resin layer (C) as it is.

  According to a preferred embodiment of the present invention, as the thermoplastic resin (II) constituting the resin layer (C), acrylic rubber (i-3), silicone rubber (i-4), and silicone / acrylic composite rubber ( i-5) A rubber-reinforced aromatic vinyl resin (II-1) obtained by polymerizing a monomer (b) containing an aromatic vinyl compound in the presence of a rubbery polymer (a) selected from the group consisting of -1) and, if desired, a rubber-reinforced styrene resin comprising a (co) polymer (II-1-2) of the monomer (b) containing the aromatic vinyl compound. Among them, a silicone / acrylic composite rubber reinforced styrene resin using a silicone / acrylic composite rubber (i-5) as the rubbery polymer (b), and a silicone rubber (i-4) as the rubbery polymer (b). ) Is preferably a mixture of a silicone rubber-reinforced styrene resin using acryl-based rubber and an acrylic rubber-reinforced styrene resin using acrylic rubber (i-3) as the rubbery polymer (b). Reinforced styrene resin is particularly preferable.

Water vapor barrier layer of the present invention (layer (D))
The water vapor barrier layer of the present invention comprises the outer surface of the layer (A) or the layer (C), or between the layer (A) and the layer (B) or the layer (B) and the layer (C). ). This water vapor barrier layer has a function of preventing water vapor from passing through the solar cell backsheet of the present invention, and is not particularly limited as long as this function is provided. High is preferred. The total light transmittance of the water vapor barrier layer is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. The haze of the water vapor barrier layer is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less. The total light transmittance and haze are measured according to JIS K 7136 or JIS K 7105. Further, the moisture permeability of the water vapor barrier layer (also referred to as water vapor permeability) is preferably 3 g / m ² · d or less when measured under conditions of a temperature of 40 ° C. and a humidity of 90% in accordance with JIS K 7129. 1 g / m ² · d or less is more preferable, and 0.7 g / m ² · d or less is even more preferable.

As the water vapor barrier layer, a thin film layer made of metal and / or metal oxide can be usually used. Examples of the metal include aluminum, and examples of the metal oxide include silicon oxide and / or aluminum oxide. The thin film layer may be formed by plating or vapor-depositing the metal or metal oxide on the layer (A), (B) or (C).
The water vapor barrier layer may be formed using a water vapor barrier film in which the thin film layer is previously deposited on a synthetic resin film. From the viewpoint of cost, it is preferable to use a water vapor barrier film in which the thin film layer is deposited on a synthetic resin film having a thickness of preferably 5 to 50 μm, more preferably about 10 to 15 μm. As such a resin film, generally, a synthetic resin not containing a colorant formed as a film or a sheet can be used, and it is preferably transparent or translucent, and more preferably transparent. As such a synthetic resin, a polyethylene terephthalate (PET) film is generally used. Commercially available products can be used as the water vapor barrier film. For example, “Tech Barrier AX (trade name)” manufactured by Mitsubishi Plastics, “GX Film (trade name)” manufactured by Toppan Printing Co., Ltd., “Toyobo” Ecosia VE500 (trade name) "and the like.

  This water vapor barrier film is laminated on the outer surface of the resin layer (A) or the resin layer (C) after obtaining a laminate comprising three layers of the resin layers (A), (B) and (C). Or, before obtaining the laminate, it may be previously laminated on the resin layer (A), the resin layer (B) or the resin layer (C), or the resin layer (A), ( You may laminate | stack simultaneously with B) and (C). The laminating method may be a method of laminating by an adhesive using a dry laminating method, and by co-extrusion simultaneously with molding of at least one of the resin layers (A), (B) and (C) without using an adhesive. A method of laminating or a method of laminating by coextrusion simultaneously with molding of the resin layers (A), (B) and (C) may be used. As said adhesive agent, a polyurethane-type adhesive agent, an epoxy-type adhesive agent, an acrylic adhesive agent etc. can be used, It is preferable to use a polyurethane-type adhesive agent among them.

The solar cell backsheet of the present invention preferably exhibits a water vapor permeability of 3 g / m ² · d or less in a water vapor transmission test at a temperature of 40 ° C. and a humidity of 90% RH in accordance with JIS K 7129B. When the water vapor permeability is higher than 3 g / m ² · d, the durability of the solar cell may be impaired.

Configuration of Back Sheet for Solar Cell The back sheet for solar cell of the present invention has a resin layer (B) as a base material layer, a resin layer (A) disposed on one side thereof, and a resin layer ( C), and the resin layer (A) or the outer surface of the resin layer (C), or between the resin layer (A) and the resin layer (B), or between the resin layer (B) and the resin layer (C) A structure in which the water vapor barrier layer (D) is disposed between the two. Among these, it is preferable to provide a water vapor | steam barrier layer (D) on the outer surface of a resin layer (A) or a resin layer (C) from the point of the ease of manufacture. As shown in FIG. 1, when using a commercially available water vapor barrier film D comprising a synthetic resin film D1 and a metal and / or metal oxide thin film layer D2 laminated thereon as the water vapor barrier layer (D), such a commercially available water vapor barrier layer (D). Since the water vapor barrier film D is generally inferior in weather resistance, it is preferably laminated on the outer surface of the resin layer (A). Since the resin layer (A) is arranged on the solar battery silicon cell S side, in this case, the water vapor barrier layer (D) is advantageously protected by the resin layers (A) to (C). In the case where the synthetic resin film D1 is made of a material having poor hydrolysis resistance such as a polyethylene terephthalate (PET) film, the water vapor barrier layer (D) is formed of a resin layer (A It is preferable to laminate toward the side of). In this case, the synthetic resin film D1 is convenient because it is protected from the ingress of external moisture by the thin film layer D2. In FIG. 1, S is a solar cell silicon cell, A is a resin layer (A), B is a resin layer (B), C is a resin layer (C), D is a water vapor barrier layer (D), and D1 is a synthetic resin. A film, D2, indicates a thin film layer.
The back sheet for a solar cell of the present invention has a dimensional change rate of ± 1% or less when left at 150 ° C. for 30 minutes. By setting the dimensional change rate to ± 1% or less, a solar cell backsheet with excellent heat resistance can be obtained. The dimensional change rate when left at 150 ° C. for 30 minutes is preferably ± 0.8% or less, and more preferably ± 0.6% or less. In order to make the dimensional change rate of the solar cell backsheet of the present invention ± 1% or less, the heat resistance of the thermoplastic resin (I) used for the resin layer (B) is increased, and the above formula ( when _{0.4 ≦ (H a + H C} ) / H B ≦ 2.4 conditions are satisfied as indicated by 2), the dimensional change rate of the back sheet for a solar cell of the present invention is usually such heat-resistant resin layer This is referred to as a dimensional change rate of (B). The thermoplastic resin (I) constituting the heat resistant resin layer (B) preferably has a glass transition temperature of 120 ° C. or higher.
The solar cell backsheet of the present invention is a light-reflective white solar cell backsheet, and specifically has a light reflectance of 50% or more at a wavelength of 400 to 1400 nm. By setting the light reflectance to 50% or more, a solar cell backsheet having excellent reflectivity can be obtained. The reflectance of light at a wavelength of 400 to 1400 nm of the solar cell backsheet is preferably 60% or more, particularly preferably 70% or more.
In the present invention, that the reflectance of light having a wavelength of 400 to 1400 nm is 50% or more means that the maximum reflectance in the wavelength range of 400 to 1400 nm is 50% or more. Therefore, it does not require that the reflectance of light of all wavelengths within the range of 400 to 1400 nm is 50% or more. In general, if the reflectance of light having a certain wavelength within a wavelength range of 400 to 1400 nm is 50% or more, it is considered that the reflectance of light having a wavelength adjacent thereto is also increased to the same extent.
In the present invention, the reflectance of light having a wavelength of 400 to 1400 nm is preferably 50% or more, preferably the reflectance of light in a wavelength region of 30% or more of a wavelength of 400 to 1400 nm is 50% or more, more preferably The reflectance of light in a wavelength region of 50% or more of wavelengths 400 to 1400 nm is 50% or more. When the reflectance of light is 50% or more in a wider range of a wavelength region of 400 to 1400 nm, the conversion efficiency of the solar cell can be further improved when used as a solar cell backsheet.
In order for the reflectance of the light having a wavelength of 400 to 1400 nm to be 50% or more in the solar cell backsheet of the present invention, at least one of the resin layer (A), the resin layer (B), and the resin layer (C). The layer preferably contains a color pigment with high brightness, and more preferably contains a white pigment. Moreover, it is more preferable that a coloring pigment with high brightness is contained in two or more layers among the resin layer (A), the resin layer (B), and the resin layer (C), and a white pigment is contained. More preferably. Furthermore, it is particularly preferable that the resin layer (A), the resin layer (B), and the resin layer (C) all contain a highly colored pigment, and most preferably a white pigment. preferable.
The L value (brightness) of the layer containing the color pigment with high brightness is preferably 55 or more, more preferably 70 or more, and 80 or more when configured as a solar cell backsheet. Is even more preferred, with 95 or more being particularly preferred.

The color pigment having high brightness is not particularly limited as long as it has a property of reflecting light having a wavelength of 400 to 1400 nm, and a white pigment is preferably used. Examples of the white pigment include ZnO, TiO ₂ , Al ₂ O ₃ .nH ₂ O, [ZnS + BaSO ₄ ], CaSO ₄ .2H ₂ O, BaSO ₄ , CaCO ₃ , 2PbCO ₃ .Pb (OH) _{2 and the} like. These can be used alone or in combination of two or more.
The white pigment is preferably titanium oxide.
As the titanium oxide, titanium oxides such as anatase form and rutile form can be used as the crystal form, but the rutile form is preferred. The average primary particle diameter of titanium oxide is preferably about 0.1 to 0.5 μm, more preferably about 0.15 to 0.35 μm. The average primary particle diameter of titanium oxide can be measured by an image analyzer based on, for example, a transmission electron micrograph. As the titanium oxide, those having a large average primary particle diameter and those having a small average primary particle diameter can be used in combination.
The content of the pigment in the layer containing the colored pigment having high brightness is not particularly limited as long as other performances are not impaired, but the reflectance of light at a wavelength of 400 to 1400 nm of the solar cell backsheet is 50% or more. It is preferable to contain a sufficient amount, specifically, 1 to 40 parts by weight, preferably 2 to 35 parts by weight, more preferably 3 to 30 parts by weight with respect to 100 parts by weight of the resin component constituting the layer. Is most preferred. If the content is less than 1 part by mass, the effect of reflection is not sufficient, and if it exceeds 40 parts by mass, the flexibility of the solar cell backsheet becomes insufficient.

In a preferred embodiment of the solar cell backsheet of the present invention, as described above, the resin layer (B) has a glass transition temperature of 120 ° C. or higher in order to impart heat resistance and flexibility to the solar cell backsheet. It is preferable that the resin layer (A) and the resin layer (C) are made of a thermoplastic resin (II) having a glass transition temperature lower than that of the thermoplastic resin (I). The glass transition temperature of the thermoplastic resin (I) constituting the resin layer (B) is preferably 120 to 220 ° C. It is convenient that the thermoplastic resin (II) constituting the resin layer (A) and the resin layer (C) has the same structure. The glass transition temperature (Tg (II)) of the thermoplastic resin (II) constituting the resin layer (A) and the resin layer (C) preferably satisfies the following formula (3):
Tg (II) ≦ Tg (I) −10 ° C. (3)
It is more preferable that the following formula (3 ′) is satisfied,
Tg (I) -50 ° C. ≦ Tg (II) ≦ Tg (I) −10 ° C. (3 ′)
It is more preferable that the following formula (3 ″) is satisfied.
Tg (I) -30 ° C. ≦ Tg (II) ≦ Tg (I) −15 ° C. (3 ″)

When the glass transition temperatures of the thermoplastic resin (I) and the thermoplastic resin (II) do not satisfy the formula (3), the effect of improving the flexibility of the resulting solar cell backsheet may be insufficient. When the difference between the glass transition temperature (Tg (I)) of the thermoplastic resin (I) and the glass transition temperature (Tg (II)) of the thermoplastic resin (II) exceeds 50 ° C., a solar cell backsheet Tends to be difficult to manufacture.
The glass transition temperature of the thermoplastic resin (I) and the thermoplastic resin (II) is the type or amount of the rubbery polymer (i) or (a) used, or the monomer containing the aromatic vinyl compound used. It can be adjusted by appropriately selecting the type or amount of (ii) or (b), and can be preferably adjusted by changing the amount of the maleimide compound. Moreover, a glass transition temperature can also be adjusted by mix | blending additives and fillers, such as a plasticizer and an inorganic filler.

  In the solar cell backsheet of the present invention, the thermoplastic resin (I) of the resin layer (B) and the thermoplastic resin (II) of the resin layer (A) and the resin layer (C) are all formed of the silicone It contains a silicone / acrylic composite rubber reinforced styrene resin obtained by polymerizing the monomer ((ii), (a)) containing the aromatic vinyl compound to the acrylic composite rubber (i-5). A resin composition containing a derived repeating unit is preferable from the viewpoint of the balance of weather resistance, heat resistance, hydrolysis resistance, and flexibility. In this case, from the viewpoint of the balance of weather resistance, heat resistance, hydrolysis resistance, and flexibility, the silicone / acrylic composite rubber reinforced styrene resin constituting the thermoplastic resin (I) of the resin layer (B) is a rubber. The amount is 10 to 20 parts by mass with respect to 100 parts by mass of the thermoplastic resin (I), the glass transition temperature is 150 to 160 ° C., and the content of the repeating unit derived from N-phenylmaleimide is the thermoplastic resin. (I) Silicone / acrylic composite rubber reinforced styrene-based resin constituting thermoplastic resin (II) of resin layer (A) and resin layer (C), preferably 15-30% by mass with respect to 100% by mass Has a rubber amount of 10 to 20 parts by mass with respect to 100 parts by mass of the aromatic vinyl resin (II-1), a glass transition temperature of 120 to 140 ° C., and a repetition derived from N-phenylmaleimide It is preferable that the content of position is 10 to 20% by weight with respect to 100 wt% aromatic vinyl resin (II-1).

  The solar cell backsheet of the present invention may be in the form of a sheet or film. For example, when the solar cell backsheet of the present invention is a film, it can be produced by a method that can be used for producing a thermoplastic film, such as a solution casting method, a melt extrusion method, a coextrusion method, a melt press method, or the like. . The melt extrusion method is excellent for large-scale production, but the solution cast method and the melt press method are also useful for small-scale, special purpose, or quality evaluation purposes. In the melt extrusion method, a T-die method or an inflation method is used. In the melt press method, a calendar method is used. When the solar cell backsheet of the present invention is a sheet, it can be produced by a method that can be used for producing a thermoplastic sheet, such as a coextrusion method.

In the T-die method, there is an advantage that it can be produced at a high speed. In that case, the resin temperature at the time of molding is not lower than the melting temperature and lower than the decomposition temperature of the resin, and is generally a temperature of 150 to 250 ° C. Is appropriate.
The specifications and molding conditions of the inflation molding machine are not limited, and conventionally known methods and conditions can be used. For example, the diameter of the extruder is 10 to 600 mm, and the ratio L / D of the diameter D and the length L from the bottom of the hopper to the tip of the cylinder is 8 to 45. The die has a shape generally used for inflation molding, and has a flow path shape such as a spider type, a spiral type, or a stacking type, and has a diameter of 1 to 5000 mm.
As the calender method molding machine, for example, any of a series type, an L type, an inverted L type, a Z type, and the like can be used.

  Further, the solar cell backsheet of the present invention may be formed by, for example, thermal lamination or extrusion lamination after forming a single layer film by T-die molding or inflation molding. It is preferable to mold using a multilayer extruder.

When the solar cell backsheet of the present invention comprises a resin layer (A), a resin layer (B), a resin layer (C) and a water vapor barrier layer (D), the thickness of the solar cell backsheet is preferably 30 to 500 μm, more preferably 70 to 450 μm, and still more preferably 80 to 400 μm.
If the thickness is too thin, the strength of the solar cell backsheet will be insufficient, and the solar cell backsheet may be broken during use. On the other hand, if the thickness is too thick, it will be difficult to process the solar cell backsheet. There is a tendency that problems such as reduction in flexibility as a back sheet for a solar cell and bending whitening occur.
Solar cell back sheet of the present invention, the ratio to the thickness _{(H C)} of the resin layer having a thickness _{(H A)} of the resin layer _{(A) (C) (H} A / H C) is, 0.5 ≦ _{H A} / H _C ≦ 1.3 is satisfied. By satisfying this condition, curling can be prevented from occurring in the solar cell backsheet.
Solar cell back sheet of the present invention, the ratio to the thickness _{(H C)} of the resin layer having a thickness _{(H A)} of the resin layer _{(A) (C) (H} A / H C) is, 0.6 ≦ _{H A} it is preferable to satisfy / _{H C} ≦ 1.2, it is more preferable to satisfy the _{0.7 ≦ H a / H C ≦} 1.1.
The solar cell backsheet of the present invention has a ratio of the total thickness of the resin layer (B) to the thickness (H _B ) of the resin layer ( _A ) and the thickness (H _C ) of the resin layer ( _C ) ( _{(H a + H C) /} H B) is, satisfies _{0.4 ≦ (H a + H C} ) / H B ≦ 2.4. By satisfying this condition, a solar cell backsheet excellent in the balance between heat resistance and flexibility can be obtained.
The solar cell backsheet of the present invention has a ratio of the total thickness of the resin layer (B) to the thickness (H _B ) of the resin layer ( _A ) and the thickness (H _C ) of the resin layer ( _C ) ( _{(H a + H C) /} H B) is preferably satisfies the _{0.5 ≦ (H a + H C} ) / H B ≦ 2.3.

The thickness of the resin layer _{(B) (H} B) is preferably from 10 to 300 [mu] m, more preferably 30～250Myuemu. When the resin layer (B) is too thin, the heat resistance is inferior, and when it is too thick, the flexibility is inferior. Further, the thickness (H _A ) of the resin layer ( _A ) and the thickness (H _C ) of the resin layer (C) are preferably 10 to 300 μm, more preferably 30 to 240 μm. When the resin layers (A) and (C) are too thin, the flexibility is inferior, and when they are too thick, the heat resistance is inferior.
Further, for example, when the total thickness of the solar cell backsheet is 250 μm, the thickness of the resin layer (A) / resin layer (B) / resin layer (C) is preferably 30 to 100/50 to 190/30. It is -100 micrometers, More preferably, it is 40-90 / 70-170 / 40-90 micrometers, More preferably, it is 50-80 / 90-150 / 50-80 micrometers. When the thickness of the resin layer (A) exceeds 100 μm, the heat resistance tends to be insufficient. On the other hand, when the thickness of the resin layer (A) is less than 30 μm, the flexibility of the solar cell backsheet film is low. There is a tendency to become insufficient.

Moreover, a protective layer (E) can be laminated | stacked on the said layer (C) side as an outermost layer if desired to the solar cell backsheet of this invention. In particular, it is preferable to provide the protective layer (E) as the outermost layer on the layer (C) side that is located on the side opposite to the solar battery cell from the viewpoints of power generation efficiency, adhesion to the solar battery cell, and the like. For example, when the water vapor barrier layer (D) is provided on the outer surface of the layer (A), the protective layer (E) can be laminated on the outer surface of the layer (C), and the water vapor barrier layer ( When D) is provided on the outer surface of the layer (C), the protective layer (E) can be laminated on the outer surface of the layer (D). In particular, when the water vapor barrier layer (D) is provided on the outer surface of the layer (C), since the vapor deposition layer of the water vapor barrier layer (D) is located on the outer surface, the protective layer (E ) Serves to protect the vapor deposition layer, and can improve the durability of the water vapor barrier property, while the layer (A) is laminated on the solar cell, so that the laminate and the solar cell have high adhesion. Sex can be achieved.
This protective layer (E) is a physical performance such as scratch resistance and punching resistance, chemical performance such as chemical resistance, or thermal performance such as flame retardancy in the cover film and backsheet for solar cells. In the present invention, those that improve the flame retardancy and scratch resistance of the solar cell backsheet are preferred.
Examples of the protective layer (E) include fluororesin films such as polyvinyl fluoride films and ethylene-tetrafluoroethylene copolymer films, polycarbonate films, polyarylate films, polyethersulfone films, polysulfone films, and polyacrylonitrile films. Polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, cellulose acetate film, acrylic resin film, weather resistant polypropylene film and the like can be used. Among these, as the protective layer used in the present invention, a fluororesin film, a polyethylene terephthalate film, and a polyethylene naphthalate film are preferable because they are excellent in flame retardancy and scratch resistance. The polyethylene terephthalate film and the polyethylene naphthalate film are each preferably excellent in hydrolysis resistance. These may use a single film or a laminated film in which two or more kinds are laminated.
The thickness of the protective layer (E) is preferably 25 to 300 μm, more preferably 25 to 200 μm. When the thickness of the protective layer (E) is less than 25 μm, the effect of protecting the laminate is insufficient. When the thickness of the protective layer (E) exceeds 300 μm, the flexibility of the laminate is insufficient, and the weight of the laminate is also not preferable.
When the solar cell backsheet of the present invention comprises a resin layer (A), a resin layer (B), a resin layer (C), a water vapor barrier layer (D), and a protective layer (E), The thickness is preferably 55 to 800 μm, more preferably 95 to 700 μm, and still more preferably 105 to 600 μm.

Furthermore, since the back sheet for a solar cell of the present invention is usually used as a surface where the resin layer (A) receives light such as sunlight, an adhesive layer or an adhesive layer is provided on the surface of the resin layer (C) serving as the back surface. By forming, it can be set as an adhesive film, an adhesive film, an adhesive sheet, an adhesive sheet, etc. A protective film for protecting these layers may be further provided on the surface of the adhesive layer or the adhesive layer.
Moreover, between the resin layer (B) of the solar cell backsheet and the resin layer (A) or the resin layer (C), as long as the decorative layer is manufactured, as long as the effect of the present invention is not lost. Other layers such as a layer made of the resulting recycled resin (usually a thermoplastic resin (I), a thermoplastic resin (II), and a mixture of these blends) can be laminated.

  The solar cell backsheet of the present invention can be suitably used as a solar cell backsheet, particularly a crystalline silicon solar cell backsheet.

  The solar cell module using the solar cell backsheet of the present invention is usually from a sunlight receiving surface side, such as a transparent substrate such as glass, a sealing film, a solar cell element, a sealing film, and the solar cell of the present invention. Consists of backsheet order.

  Glass is generally used as the transparent substrate. Although glass is excellent in transparency and weather resistance, since it has low impact resistance and is heavy, a weather-resistant transparent resin is also preferably used in the case of a solar cell placed on the roof of a general house. An example of the transparent resin is a fluorine resin film. The thickness of the transparent substrate is usually 3 to 5 mm when glass is used, and is usually 0.2 to 0.6 mm when transparent resin is used.

  An olefin resin is used as the sealing film. Here, the olefin-based resin is a general term for an olefin such as ethylene, propylene, butadiene, or isoprene, or a polymer obtained by polymerizing or copolymerizing a diolefin, and includes ethylene and other monomers such as vinyl acetate and acrylate. Also includes copolymers and ionomers. Specific examples include polyethylene, polypropylene, polymethylpentene, ethylene / vinyl chloride copolymer, ethylene / vinyl acetate copolymer (EVA), ethylene / vinyl alcohol copolymer, chlorinated polyethylene, and chlorinated polypropylene. Of these, EVA is widely used. EVA is sometimes applied as a pressure-sensitive adhesive or an adhesive, or may be used in a sheet form, but is generally used in a sheet form by thermocompression bonding. The thickness when used in the form of a sheet is usually 0.2 to 5.0 mm.

  As the solar cell element, known silicon can be used. The silicon may be amorphous silicon, single crystal silicon, or polycrystalline silicon. Comparing the sensitivity bands of the solar spectrum between amorphous silicon and polycrystalline silicon, amorphous silicon has a sensitivity band on the visible light side, whereas polycrystalline silicon has a sensitivity band on the infrared side. The energy distribution of sunlight is about 3% in the ultraviolet region, about 47% in the visible light region, and about 50% in the infrared region. By using a combination of the solar cell backsheet of the present invention with excellent reflection characteristics and a solar cell element, the power generation efficiency is excellent, and heat resistance, weather resistance, hydrolysis resistance and flexibility are also excellent. A solar cell module can be obtained.

  You may join the structural unit of said solar cell module using an adhesive agent. As the adhesive, a known adhesive can be used, and examples thereof include a butyl rubber adhesive, a silicone adhesive, and an EPDM adhesive.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example. In Examples and Comparative Examples, parts and% are based on mass unless otherwise specified.

1. Evaluation Method Measurement methods for various evaluation items in the following Examples and Comparative Examples are shown below.

1-1. Rubber content of thermoplastic resins (I) and (II) Calculated from the composition at the time of raw material charging.

1-2. N-phenylmaleimide unit content rate It calculated from the composition at the time of raw material preparation.

1-3. Glass transition temperature (Tg)
Based on JIS K7121, it measured using the differential scanning calorimeter DSC2910 type | mold (brand name; product made by TA Instruments).

1-4. Light reflectance (%) at a wavelength of 400 to 1400 nm of the laminate
It measured by JASCO Corporation V-670 using the test piece (50 mm x 50 mm) of a laminated body. The wavelength range was 200-2700 nm. The reflectance in the wavelength range of 400 to 1400 nm was measured. In addition, about the comparative example 3, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.

1-5. L value Using the test piece (50 mm x 50 mm x 100 micro | micron | mu) of a laminated body, the L value of the surface at the side of the resin layer (A) was measured with the spectrophotometer TCS-II by Toyo Seiki. In addition, about the comparative example 3, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.

1-6. Dimensional change rate after 30 minutes at 150 ° C. of layered product or layer (B) alone (%) (heat resistance)
Draw a square of 50 mm (MD) x 50 mm (TD) in the center of the surface of the test piece of 100 mm (MD: resin extrusion direction from T die) x 100 mm (TD: direction orthogonal to MD), and in a 150 ° C constant temperature bath For 30 minutes, and then taken out and measured for dimensional changes in the MD and TD directions of the test piece. The length after heating was the average of the measured values of the length in the MD and TD directions of the square. The shrinkage rate was determined based on the following formula from the measured dimensions before and after heating.

1-7. Flexibility (bending test)
A test piece of 100 mm (MD) × 100 mm (TD) was cut out from the laminate, bent along the symmetry axis in the MD direction, and then bent along the symmetry axis in the TD direction. The bent specimen was reciprocated twice on each crease at a speed of 5 mm / sec using a manual crimping roll (2000 g) according to JIS Z0237. Thereafter, the folds were expanded and returned to the original state, and the state of the test piece was visually observed. The judgment criteria are shown below. The test results show that the folds are not broken, and the flexibility is excellent. In addition, about the comparative example 2, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.

A: The crease is not broken, and the crease is not broken even if it is bent and expanded again.
○: The crease is not cracked, but the crease is cracked when it is bent and expanded again.
X: The crease is broken.

1-8. Hydrolysis resistance (pressure cooker test)
1-8-1. Preservation of breaking stress A test piece of 150 mm (MD) x 15 mm (TD) was cut out from the laminate, and allowed to stand for 100 or 200 hours under conditions of a temperature of 120 ° C and a humidity of 100%, and then an AG2000 tensile tester (manufactured by Shimadzu Corporation). The breaking stress of the test piece was measured according to JIS K 7127. The distance between chucks at the time of sample setting was 100 mm, and the tensile speed was 300 mm / min. From the measured value of the breaking stress obtained, the retention rate of the breaking stress was determined by the following formula. In addition, about the comparative example 2, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.

  The hydrolysis resistance was evaluated according to the following criteria based on the obtained retention rate of the breaking stress. The higher the retention rate, the better the hydrolysis resistance.

○: Breaking stress retention exceeds 80%.
Δ: Retention rate of breaking stress is 50 to 80%.
X: Retention rate of breaking stress is less than 50%.

1-8-2. Elongation retention The breaking elongation was measured simultaneously with the measurement of 1-8-1. From the measured value of the obtained elongation, the retention rate of elongation was obtained by the following formula.

From the obtained elongation retention, hydrolysis resistance was evaluated according to the following criteria. The higher the retention rate, the better the hydrolysis resistance.
○: Retention rate of elongation exceeds 80%.
(Triangle | delta): Retention rate of elongation is 50 to 80%.
X: Retention rate of elongation is less than 50%.

1-8-3. Measurement of curled (deformed) state A test piece of 150 mm (MD) × 15 mm (TD) was cut out from the laminate, and the test piece was curled (deformed) after being left at a temperature of 120 ° C. and a humidity of 100% for 100 or 200 hours. ) The state was visually observed and evaluated according to the following criteria. In addition, about the comparative example 2, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.
○: No curling (deformation).
X: There is curl (deformation).

1-9. Conversion efficiency improvement rate 1/4 polycrystalline silicon in which the conversion efficiency of a single cell was measured in advance using a Solar Simulator PEC-11 manufactured by Peccell in a room adjusted to a temperature of 25 ° C. ± 2 ° C. and a humidity of 50 ± 5% RH. A module having a thickness of 3 mm on the surface of the cell and a laminate on the back surface, the silicon cell was sealed with EVA, and a conversion efficiency was measured. In order to reduce the influence of temperature, the conversion efficiency was measured immediately after irradiation with light. The improvement rate of conversion efficiency was obtained by the following equation. When the improvement rate of the conversion efficiency is increased, the power generation efficiency of the solar cell is improved. In addition, about the comparative example 2, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.

1-10. Weather resistance A 50 mm (MD) x 30 mm (TD) test piece was cut out from the laminate, and an exposure test was performed by repeating the conditions of Steps 1 to 4 shown below using a metalling weather meter MV3000 (manufactured by Suga Test Instruments). A change in color tone ΔE before and after 100 hours of exposure was calculated. In addition, about the comparative example 2, it measured by the method similar to the above except having used the single layer body instead of the obtained laminated body.

Step 1: Irradiation 0.53 kW / m ² , 63 ° C., 50% RH, 4 hours Step 2: Irradiation + rainfall 0.53 kW / m ² , 63 ° C., 95% RH, 1 minute Step 3: Dark 0 kW / m ² , 30 ° C, 98% RH, 4 hours Step 4: Irradiation + rainfall 0.53 kW / m ² , 63 ° C, 95% RH, 1 minute

ΔE was calculated by the following equation by measuring Lab (L: brightness, a: redness, b: yellowness) using a spectrophotometer V670 (manufactured by JASCO).

In the formula, L ₁ , a ₁ and b ₁ represent values before exposure, and L ₂ , a ₂ and b ₂ represent values after exposure. The smaller the value of ΔE, the smaller the color change and the better the weather resistance. The evaluation criteria are as follows.

○: ΔE is 10 or less.
×: ΔE exceeds 10.

1-11. Water vapor barrier property (water vapor permeation test)
Based on JIS K7129B, the measurement was performed under the following measurement conditions.
Test apparatus: PERMATRAN W3 / 31 (manufactured by MOCON).
Test temperature: 40 ° C.
Test humidity: 90% RH (actual humidity control).
Transmission surface: The layer (C) side of the laminate was disposed on the water vapor side.

1-12. Flame retardance Using a UL94 V test burner, the lower end of a vertically suspended test piece (width 20 mm x length 100 mm) was indirect flamed for 5 seconds with the burner tip 10 mm away from the test piece. After completion of the flame contact, the combustion state of the flame contact portion of the test piece was visually observed and evaluated according to the following criteria.
○: No ignition.
X: There is ignition.

1-13. Scratch resistance Using a reciprocating friction tester manufactured by Toko Seimitsu Kogyo Co., Ltd., the surface of the test piece was subjected to 500 reciprocating frictions with a cotton canvas Kanaki No. 3 and a vertical load of 500 g. .
○: Scratches are not observed.
Δ: Slight scratches are observed.
X: Scratches are clearly observed.

2. 2. Manufacturing method of laminated body 2-1. Raw materials used 2-1-1. Butadiene rubber reinforced styrene resin [Preparation of butadiene graft copolymer (a)]
In a glass reaction vessel equipped with a stirrer, 75 parts of ion exchange water, 0.5 part of potassium rosinate, 0.1 part of t-dodecyl mercaptan, polybutadiene latex (average particle size: 270 nm, gel content 90%) 32 Part (solid content conversion), 8 parts of styrene-butadiene copolymer latex (styrene content 25%, average particle size 550 nm), 15 parts of styrene and 5 parts of acrylonitrile were added, and the temperature was increased while stirring in a nitrogen stream. When the internal temperature reached 45 ° C., a solution in which 0.2 parts of sodium pyrophosphate, 0.01 parts of ferrous sulfate heptahydrate and 0.2 parts of glucose were dissolved in 20 parts of ion-exchanged water was added. Thereafter, 0.07 part of cumene hydroperoxide was added to initiate polymerization, and polymerization was carried out for 1 hour. Subsequently, 50 parts of ion-exchanged water, 0.7 part of potassium rosinate, 30 parts of styrene, 10 parts of acrylonitrile, 0.05 part of t-dodecyl mercaptan and 0.01 part of cumene hydroperoxide are continuously added over 3 hours. did. After polymerization for 1 hour, 0.2 part of 2,2'-methylene-bis (4-ethylene-6-t-butylphenol) was added to complete the polymerization. Magnesium sulfate was added to this latex to coagulate the resin component. Thereafter, it was washed with water and further dried to obtain a polybutadiene-based graft copolymer (A). The graft ratio was 72%, and the intrinsic viscosity [η] of the acetone-soluble component was 0.47 dl / g.

2-1-2. Silicone / Acrylic Composite Rubber Reinforced Styrene Resin “Metbrene SX-006 (trade name)” manufactured by Mitsubishi Rayon Co., Ltd. (resin modifier, silicone / acrylic composite rubber grafted with acrylonitrile-styrene copolymer, 50% rubber, graft 80% rate, intrinsic viscosity [η] (in methyl ethyl ketone, 30 ° C.) 0.38 dl / g, glass transition temperature (Tg) 135 ° C.) were used.

2-1-3. Silicone rubber reinforced styrene resin / acrylic rubber reinforced styrene resin mixture [Preparation of silicone rubber reinforced styrene resin (I-1)]
1.3 parts of p-vinylphenylmethyldimethoxysilane and 98.7 parts of octamethylcyclotetrasiloxane are mixed, and this is put into 300 parts of distilled water in which 2.0 parts of dodecylbenzenesulfonic acid is dissolved, and 3 parts by a homogenizer. The mixture was stirred and dispersed for emulsification. This mixed solution was transferred to a separable flask equipped with a condenser, a nitrogen inlet and a stirrer, and heated at 90 ° C. for 6 hours and kept at 5 ° C. for 24 hours while stirring and mixing, thereby completing the condensation. The resulting polyorganosiloxane rubbery polymer had a condensation rate of 93%. The latex was neutralized to pH 7 with an aqueous sodium carbonate solution. The resulting polyorganosiloxane rubbery polymer latex had an average particle size of 0.3 μm.
In a 7-liter glass flask equipped with a stirrer, 100 parts of ion exchange water, 1.5 parts of potassium oleate, 0.01 parts of potassium hydroxide, 0.1 part of t-dodecyl mercaptan, the polyorganosiloxane latex A batch polymerization component consisting of 40 parts (in terms of solid content), 15 parts of styrene, and 5 parts of acrylonitrile was added, and the temperature was raised while stirring. When the temperature reaches 45 ° C., an activity comprising 0.1 part of ethylenediaminetetraacetate sodium, 0.003 part of ferrous sulfate, 0.2 part of sodium formaldehyde sulfoxylate dihydrate and 15 parts of ion-exchanged water Aqueous agent solution and 0.1 part of diisopropylbenzene hydroperoxide were added and the reaction was continued for 1 hour.
Thereafter, 50 parts of ion-exchanged water, 1 part of potassium oleate, 0.02 part of potassium hydroxide, 0.1 part of t-dodecyl mercaptan, 0.2 part of diisopropylbenzene hydroperoxide, 30 parts of styrene, and 10 parts of acrylonitrile. A mixture of incremental polymerization components consisting of a monomer was continuously added over 3 hours, and the reaction was continued. After completion of the addition, the reaction was further continued for 1 hour with stirring, and then 0.2 part of 2,2-methylene-bis- (4-ethylene-6-t-butylphenol) was added to obtain a polymer latex. Furthermore, 1.5 parts of sulfuric acid was added to the latex and coagulated at 90 ° C., followed by dehydration, washing with water, and drying to obtain a powdery silicone rubber-reinforced styrene resin (I-1). The graft ratio was 84%, and the intrinsic viscosity [η] (in methyl ethyl ketone, 30 ° C.) was 0.60 dl / g.

[Preparation of Acrylic Rubber Reinforced Styrene Resin (I-2)]
Solid content containing acrylic rubbery polymer (volume average particle diameter 100 nm and gel content 90%) obtained by emulsion polymerization of 99 parts of n-butyl acrylate and 1 part of allyl methacrylate in a reactor. 50 parts of latex with a concentration of 40% (in terms of solid content) was added, and further diluted with 1 part of sodium dodecylbenzenesulfonate and 150 parts of ion-exchanged water. Thereafter, the inside of the reactor was replaced with nitrogen gas, and 0.02 part of disodium ethylenediaminetetraacetate, 0.005 part of ferrous sulfate and 0.3 part of sodium formaldehydesulfoxylate were added, and the mixture was stirred up to 60 ° C. The temperature rose.
On the other hand, 1.0 part of terpinolene and 0.2 part of cumene hydroperoxide are dissolved in 50 parts of a mixture of 37.5 parts of styrene and 12.5 parts of acrylonitrile in a container, and then the inside of the container is replaced with nitrogen gas. A monomer composition was obtained.
Next, polymerization was performed at 70 ° C. while adding the monomer composition to the reactor at a constant flow rate over 5 hours to obtain a latex. Magnesium sulfate was added to this latex to coagulate the resin component. Then, acrylic rubber reinforced styrene resin (I-2) was obtained by washing with water and further drying. The graft ratio was 93%, and the intrinsic viscosity [η] (in methyl ethyl ketone, 30 ° C.) was 0.30 dl / g.

2-1-4. Styrene-acrylonitrile copolymer "SAN-H (trade name)" (AS resin) manufactured by Techno Polymer Co., Ltd.

2-1-5. N-Phenylmaleimide-acrylonitrile-styrene copolymer “Polyimilex PAS1460 (trade name)” manufactured by Nippon Shokubai Co., Ltd. (N-phenylmaleimide-acrylonitrile-styrene copolymer, N-phenylmaleimide unit content 40%)

2-1-6. Polyethylene terephthalate “Novapex GM700Z (trade name)” manufactured by Mitsubishi Chemical Corporation was used. The glass transition temperature (Tg) was 75 ° C.

2-1-7. Titanium oxide (white)
“Taipec CR-60-2 (trade name)” (average primary particle size 0.21 μm) manufactured by Ishihara Sangyo Co., Ltd.
“Taipeku CR-50-2 (trade name)” (average primary particle size: 0.25 μm) manufactured by Ishihara Sangyo Co., Ltd.
“Taipeku CR-58-2 (trade name)” manufactured by Ishihara Sangyo Co., Ltd. (average primary particle size 0.28 μm).

2-2. Molding materials for resin layers (A), (B) and (C) After mixing the components described in Table 1 or Table 2 in the proportions described in Table 1 or Table 2 using a Henschel mixer, a twin-screw extruder (Nippon Steel) Melted and kneaded with Tokosho, TEX44, barrel temperature of 270 ° C., and pelletized. The obtained composition was evaluated according to the above evaluation method. The results are shown in Tables 1 and 2.

2-3. Material of layer (D) (water vapor barrier layer) The water vapor barrier film described in Table 3 was used. In these water vapor barrier films, a transparent thin film layer made of metal and / or metal oxide is formed as a water vapor barrier layer on one side of a transparent polyethylene terephthalate (PET) film. In Table 3, moisture permeability, total light transmittance, and haze are values measured by the methods as described above.

2-4. Layer (E) (Protective layer)
The following commercially available PET film was used.
(E-1): PET film “Lumirror X10S” (trade name) manufactured by Toray Industries, Inc. with a film thickness of 50 μm.
(E-2): PET film “Melinex 238” (trade name) manufactured by Teijin DuPont Films Co., Ltd. having a film thickness of 75 μm.
(E-3): 50 μm thick PEN film “Teonex Q51” (trade name) manufactured by Teijin DuPont Films Ltd.

3-1. Manufacture of laminated film (Examples 1-14, Comparative Examples 1-10)
A film was produced by the following method.
First, a multilayer film forming machine equipped with a T die (die width: 1400 mm, lip interval: 0.5 mm) and three extruders with a screw diameter of 65 mm was used, and the above layers (A) and (B ) And (C) were supplied as shown in Table 4-1 or Table 4-2, and the resin was discharged from the T die at a melting temperature of 270 ° C. to obtain a soft film. Then, this soft film was surface-adhered to a cast roll (roll surface temperature: 95 ° C.) with an air knife, cooled and solidified to obtain a film. In that case, the thickness of the whole film and each thickness of layer (A) / layer (B) / layer (C) are adjusted by adjusting the operating conditions of the extruder and the cast roll. -2 as described. Thereafter, the layer (D) made of the film shown in Table 4-1 or Table 4-2 is applied to the surface of the layer (A) of the obtained film with the adhesive shown in Table 4-1 or Table 4-2. Used and pasted. At that time, the thin film layer (water vapor barrier layer) of the water vapor barrier film constituting the layer (D) was laminated toward the layer (A) side. That is, a laminate having the configuration shown in FIG. 1 was obtained. The evaluation results of the obtained film are shown in Table 4-1 or Table 4-2.
The thickness of the film was measured using a thickness gauge (model “ID-C1112C, manufactured by Mitutoyo Co., Ltd.), and after 1 hour from the start of film production, the film was cut out, centered in the film width direction, and directed from the center to both ends The thickness was measured at intervals of 10 mm, and the average value was taken, and the value at the measurement point in the range of 20 mm from the edge of the film was removed from the calculation of the average value.

  From the results of Table 4-1, the laminates of Examples 1 to 14 have high light reflectance, excellent conversion efficiency of solar cells, excellent heat resistance and water vapor barrier properties, and further weather resistance, Excellent hydrolyzability and flexibility.

From the results in Table 4-2, the following can be understood.
Comparative Example 1 is an example lacking the layer (D) and is inferior in water vapor barrier properties.
Comparative Example 2 is a two-layer product lacking a resin layer (B) having high heat resistance, and is inferior in heat resistance.
Comparative Example 3 is a single layer product of the resin layer (B) having high heat resistance, and is inferior in flexibility.
In Comparative Example 4, the resin layer (B) is a three-layer product inferior in heat resistance and inferior in heat resistance.
Comparative Example 5 is a three-layer product in which none of the resin layers contains a white pigment, and the reflectance of light having a wavelength of 400 to 1400 nm of the laminate is less than 50%, and is inferior in conversion efficiency of the solar cell.
Comparative Example 6 is a three-layer product having H _A / H _C of less than 0.5, causes curling in the pressure cooker test, and is inferior in heat deformability.
Comparative Example 7, H A _/ H _C is a three-layer product of greater than 1.3, resulting curl in pressure cooker test, poor thermal deformation resistance.
Comparative Example _{8, (H A + H C)} / H B is a three-layer product of less than 0.4, less flexible.
Comparative Example 9 is a three-layer product in which (H _A + H _C ) / H _B exceeds 2.4, and is inferior in heat resistance.
Comparative Example 10 is a three-layer product in which all layers are composed of a polyethylene terephthalate resin having a low glass transition temperature, but is inferior in heat resistance and inferior in hydrolysis resistance and weather resistance.

3-2. Examples 15-17
A film was produced in the same manner as in Example 2, Example 7 or Example 14, except that the water vapor barrier layer (D) was laminated on the outer surface of the layer (C). At that time, the layer (D) was laminated so that the thin film layer (water vapor barrier layer) of the water vapor barrier film constituting the layer (D) was located on the outer surface. That is, a laminate having the configuration shown in FIG. 2 was obtained.
The obtained film was used as a test piece and evaluated according to the above evaluation method. The results are shown in Table 5.

3-3. Example 18
The PET film shown in Table 6 was attached to the outer surface of the layer (C) of the film obtained in Example 2 as a protective layer (E) using a polyurethane-based adhesive (coating thickness: 8 μm). That is, a laminate having the configuration shown in FIG. 3 was obtained.
The obtained film was used as a test piece and evaluated according to the above evaluation method. The results are shown in Table 6.

3-4. Examples 19-27
Protect the PET film or PEN film of Table 6 on the outer surface of the layer (D) of the film obtained in Example 15, Example 16 or Example 17 with a polyurethane-based adhesive (coating thickness: 8 μm). Pasted as layer (E). That is, a laminate having the configuration shown in FIG. 4 was obtained.
The obtained film was used as a test piece and evaluated according to the above evaluation method. The results are shown in Table 6.

  Table 6 shows that it is preferable to laminate the protective layer (E) in the present invention on the outer surface of the resin layer (C) or the water vapor barrier layer (D) because scratch resistance and flame retardancy are improved.

  The solar cell backsheet of the present invention comprises a resin laminate having high light reflectivity, excellent heat resistance and water vapor permeability, and is also excellent in weather resistance, hydrolysis resistance and flexibility. Therefore, it is suitable as a solar cell backsheet used in a harsh environment exposed to sunlight.

A ... layer (A), B ... layer (B), C ... layer (C), D ... layer (D), E ... layer (E), D1 ... synthetic resin film, D2 ... thin film layer, S ... solar cell Silicon cell.

Claims (15)

A resin layer (B) which is a base material layer;
A resin layer (A) laminated on one side of the resin layer (B);
A resin layer (C) laminated on the other side of the resin layer (B);
Laminated on the outer surface of the resin layer (A) or the resin layer (C), or between the resin layer (A) and the resin layer (B) or between the resin layer (B) and the resin layer (C). A water vapor barrier layer (D);
The thickness (H _A ) of the resin layer ( _A ), the thickness (H _B ) of the resin layer ( _B ), and the thickness (H _C ) of the resin layer ( _C ) are represented by the following formulas (1) and (2): ), The dimensional change rate when left at 150 ° C. for 30 minutes is ± 1% or less, and the reflectance of light having a wavelength of 400 to 1400 nm is 50% or more.
_{0.5 ≦ H A / H C ≦} 1.3 ... (1)
_{0.4 ≦ (H A + H C} ) / H B ≦ 2.4 ... (2)   The solar cell backsheet according to claim 1, wherein at least one of the resin layer (A), the resin layer (B), and the resin layer (C) is a resin layer containing a white pigment.   The resin layer (B) is made of a thermoplastic resin (I) having a glass transition temperature of 120 ° C. or higher, and the resin layer (A) and the resin layer (C) have a glass transition temperature lower than that of the thermoplastic resin (I). The solar cell backsheet according to claim 1 or 2, comprising a plastic resin (II).   Rubber-reinforced aromatic vinyl resin (II-1-1) obtained by polymerizing a monomer (b) containing an aromatic vinyl compound in the presence of a rubbery polymer (a) And an aromatic vinyl resin (II-1) containing a (co) polymer (II-1-2) of a monomer (b) containing an aromatic vinyl compound if desired, and the aromatic vinyl resin (II-1) The solar cell backsheet according to claim 3, wherein the content of the rubbery polymer (a) is 5 to 40 parts by mass with respect to 100 parts by mass.   The rubbery polymer (a) is at least one selected from the group consisting of ethylene-α-olefin rubbers, hydrogenated conjugated diene rubbers, acrylic rubbers, silicone rubbers, and silicone / acrylic composite rubbers. Item 5. The solar cell backsheet according to Item 4.   The aromatic vinyl resin (II-1) comprises a maleimide compound as the monomer (b) containing an aromatic vinyl compound, and the aromatic vinyl resin (II-1) is 100% by mass with respect to 100% by mass. The solar cell backsheet according to claim 4 or 5, wherein the content of the repeating unit derived from the maleimide compound is 1 to 30% by mass.   Rubber-reinforced aromatic vinyl resin (I-1-1) obtained by polymerizing monomer (ii) containing an aromatic vinyl compound in the presence of rubber polymer (i), thermoplastic resin (I) And an aromatic vinyl resin (I-1) containing a (co) polymer (I-1-2) of a monomer (ii) optionally containing an aromatic vinyl compound, the aromatic vinyl fat (I-1) The back sheet for a solar cell according to any one of claims 3 to 6, wherein the content of the rubbery polymer (i) is 5 to 40 parts by mass with respect to 100 parts by mass.   The rubbery polymer (i) is at least one selected from the group consisting of ethylene-α-olefin rubbers, hydrogenated conjugated diene rubbers, acrylic rubbers, silicone rubbers, and silicone / acrylic composite rubbers. Item 8. The solar cell backsheet according to Item 7.   The aromatic vinyl resin (I-1) comprises a maleimide compound as the monomer (ii) containing an aromatic vinyl compound, and the aromatic vinyl resin (I-1) is 100% by mass with respect to 100% by mass. The back sheet for a solar cell according to claim 7 or 8, wherein the content of the repeating unit derived from the maleimide compound is 1 to 30% by mass.   The glass transition temperature (Tg (I)) of the thermoplastic resin (I) is 120 to 220 ° C. The solar cell backsheet according to any one of claims 3 to 9. The solar cell backsheet according to claim 10, wherein the glass transition temperature (Tg (II)) of the thermoplastic resin (II) satisfies the following formula (3).
Tg (II) ≦ Tg (I) −10 ° C. (3)   The thickness of the solar cell backsheet is 30-500 micrometers, The solar cell backsheet as described in any one of Claims 1-11.   The solar cell backsheet according to any one of claims 1 to 11, comprising a protective layer (E) as an outermost layer of the layer (C).   The solar cell backsheet according to claim 13, wherein the solar cell backsheet has a thickness of 55 to 800 μm.   The solar cell module which comprises the solar cell backsheet as described in any one of Claims 1-14.

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