JP2009181989A - Back sheet for solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back sheet for solar cells which, even when it has a black colored or chromatically colored appearance, can reflect infrared light having certain wavelengths to prevent heat accumulation and, at the same time, has excellent heat resistance and water vapor barrier property. <P>SOLUTION: Disclosed is the back sheet for solar cells including the following layer (B) as a base material layer, the following layer (A) stacked on one side of the layer (B), the following layer (C) stacked on the other side of the layer (B), and a water vapor barrier layer (D). A thickness (H<SB>A</SB>) of the following layer (A), a thickness (H<SB>B</SB>) of the following layer (B) and a thickness (H<SB>C</SB>) of the following layer (C), satisfy an expression (1) of 0.75≤H<SB>A</SB>/H<SB>C</SB>≤1.25 and an expression (2) of 0.4≤(H<SB>A</SB>+H<SB>C</SB>)/H<SB>B</SB>≤2.4. Layer (A): A colored resin layer of which the light absorption is not more than 10% at a wavelength of 800 nm to 1400 nm. Layer (B): A thermoplastic resin layer which satisfies a dimensional change rate of not more than ±1% as measured under conditions of standing at 150°C for 30 min. Layer C: A colored resin layer having a light reflectance of not less than 50% at a wavelength of 400 nm to 1400 nm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solar cell backsheet that absorbs visible light when irradiated with light but reflects infrared light to prevent heat storage and has excellent heat resistance and water vapor barrier properties. Further, the present invention relates to a solar cell backsheet that is excellent in weather resistance, hydrolysis resistance and flexibility, and curling is suppressed.

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 solar cells has increased. 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 back sheet for a solar cell 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).

On the other hand, since solar cells are arranged on the roof of a house or the like, in recent years, a solar cell backsheet colored in a dark color such as black has been required from the viewpoint of design.
However, conventional black solar cell backsheets are generally formed by kneading carbon black into a resin, and carbon black absorbs sunlight to increase the temperature, so that the power generation efficiency of the solar cell In addition to lowering the durability, the durability may also be reduced.

On the other hand, a low heat storage solar cell backsheet formed by kneading an inorganic pigment having infrared reflection characteristics into rubber-reinforced vinyl resin has also been proposed (Patent Document 3), but the infrared reflectance is further improved. Is required.
Also proposed is a solar cell backsheet that is provided with a black resin layer containing a perylene pigment on the surface and reflects near infrared light with a reflectance of light with a wavelength of 800 to 1100 nm of 30% or more to prevent heat storage. However, since the substrate is made of a polyethylene terephthalate film, there is a drawback that the weather resistance and hydrolysis resistance are poor.
In addition, 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 JP 2007-103813 A JP 2007-128943 A

  The present invention has the property of preventing heat storage by reflecting infrared rays of a specific wavelength even if it is colored black or chromatic in appearance, and has low heat deformation and excellent heat resistance. Even if it is used outdoors for a long time, it is difficult to cause hydrolysis and has excellent weather resistance. Also, it has excellent water vapor barrier properties, and even in the form of a film, it is difficult to break and has excellent flexibility, workability, productivity and handling. An object is to provide a solar cell backsheet that has good properties and curling is suppressed.

  As a result of intensive studies to solve the above problems, the present inventors have arranged a colored resin layer having a low infrared light absorption rate on one side of a thermoplastic resin layer having specific heat resistance, and the thermoplastic By arranging a water vapor barrier layer on the outer surface or interlayer of an infrared reflective laminate in which a colored resin layer having a high light reflectance is arranged on the other side of the resin layer, infrared rays can be transmitted even if they are colored in appearance. The present inventors have found that a solar cell backsheet having the property of reflecting and preventing heat storage and having excellent heat resistance and water vapor barrier properties can be obtained, and the present invention has been completed.

That is, the present invention
The following layer (B) which is a base material layer;
The following layer (A) laminated on one side of the layer (B);
The following layer (C) laminated on the other side of the layer (B);
The outer surface of the layer (A) or the layer (C), or between the layer (A) and the layer (B) or between the layer (B) and the layer (C). A water vapor barrier layer (D);
The thickness (H _A ) of the following layer ( _A ), the thickness (H _B ) of the following layer ( _B ), and the thickness (H _C ) of the following layer ( _C ) are represented by the following formulas (1) and (2): ) Is provided.
Layer (A): a colored resin layer having an absorption rate of light having a wavelength of 800 to 1400 nm of 10% or less,
Layer (B): a thermoplastic resin layer having a dimensional change rate of ± 1% or less when left at 150 ° C. for 30 minutes,
Layer (C): a colored resin layer having a reflectance of 50% or more of light having a wavelength of 400 to 1400 nm.
_{0.75 ≦ H A / H C ≦} 1.25 ... (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.

In the solar cell backsheet of the present invention, an infrared transmissive colored resin layer (A) is laminated on one side of a heat-resistant thermoplastic resin layer (B), and an infrared reflective resin layer ( Since C) is laminated, when the colored resin layer (A) is irradiated with light, the colored resin layer (A) absorbs visible light and exhibits a colored appearance, but allows infrared light to pass through, The infrared light transmitted through the layer (B) is reflected by the resin layer (C) and is emitted again from the layer (B) and the layer (A), thereby improving the power generation efficiency of the solar cell. Moreover, since the solar cell backsheet of this invention is equipped with the water vapor | steam barrier layer (D) in the outer surface or interlayer, it does not deteriorate the silicon cell of a solar cell.
Therefore, the solar cell backsheet of the present invention is suitable for outdoor use that is exposed to sunlight or wind and rain for a long period of time because it suppresses heat generation and heat storage by infrared rays and has heat resistance and water vapor barrier properties. is there.
Moreover, since the thickness of each layer of layer (A)-(C) satisfy | fills the predetermined relationship, the curl does not generate | occur | produce in the solar cell backsheet of this invention.
Moreover, since the back sheet | seat for solar cells of this invention can comprise any layer as a molded resin layer, it can manufacture easily.

  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 (layer (B))
The layer (B) constituting the base material layer of the solar battery backsheet of the present invention is a thermoplastic resin layer having a dimensional change rate of ± 1% or less when left at 150 ° C. for 30 minutes. This base material layer provides durability for long-term use under irradiation of light such as sunlight, and at the same time, a large temperature during drying or surface treatment after printing on the solar battery backsheet of the present invention, or other secondary processing. Even if it receives a history, it has a function of keeping dimensional changes due to thermal contraction and thermal expansion small. Moreover, this base material layer has a function of transmitting infrared rays that have passed through the layer (A) and transmitting infrared rays that have been reflected from the layer (C), and has passed through the layer (A). Higher infrared transmittance is preferred. The layer (B) having such a function can be usually formed by molding a resin not containing a colorant as a film or a sheet, and is preferably transparent or translucent, and more preferably transparent.

  The thermoplastic resin (I) constituting the base material layer (hereinafter also referred to as “component (I)”) is not particularly limited as long as it satisfies the above dimensional change rate. As a specific example, Vinyl resins (eg, aromatic resins such as styrene resins, rubber-reinforced styrene resins, acrylonitrile / styrene resins, (co) polymers of aromatic vinyl compounds), polyolefin resins (eg, polyethylene resins) , 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, (meta ) (Co) polymers of acrylic ester compounds), fluororesins, ethylene / vinyl acetate resins and the like. 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., and even more preferably 130 to 190 ° C. Still more preferably, the temperature is 140-170 ° C, even more preferably 145-160 ° C. When the glass transition temperature is less than 120 ° C., the heat resistance is not sufficient.

The thermoplastic resin (I) is typically a vinyl resin (I ′), that is, a rubber obtained by polymerizing a vinyl monomer (ii) in the presence of a rubbery polymer (i). Examples thereof include a reinforced vinyl resin (I-1) and / or a (co) polymer (I-2) of the vinyl monomer (ii). The latter (co) polymer (I-2) is obtained by polymerizing the vinyl monomer (ii) in the absence of the rubbery polymer (i). The rubber-reinforced vinyl resin (I-1) is usually not grafted onto the rubber polymer and the copolymer obtained by graft copolymerization of the vinyl monomer (ii) with the rubber polymer (i). Ungrafted components [same as the above (co) polymer (I-2)] are included.
Among them, a preferred thermoplastic resin (I) is a vinyl monomer comprising an aromatic vinyl compound and optionally another monomer copolymerizable with the aromatic vinyl compound in the presence of the rubbery polymer (i). It is a rubber-reinforced styrene resin (I-1 ′) and / or a (co) polymer (I-2 ′) of the vinyl monomer (ii ′) obtained by polymerizing the body (ii ′).

  The thermoplastic resin (I) of the present invention preferably contains at least one rubber-reinforced vinyl resin (I-1) from the viewpoint of impact resistance and flexibility. If desired, the (co) polymer (I-2) may be contained. The content of the rubbery polymer (i) is preferably 5 to 40 parts by weight, more preferably 8 to 30 parts by weight, still more preferably 10 to 20 parts by weight, particularly preferably 100 parts by weight of the component (I). Is 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.

  The vinyl resin (I ′) preferably includes a maleimide compound unit as the vinyl monomer (ii) from the viewpoint of heat resistance, and is based on 100% by mass of the vinyl resin (I ′). In general, the content of the maleimide compound unit is preferably 0 to 30% by mass, more preferably 1 to 30% by mass, and even more preferably 5 to 27% by mass. It is still more preferable that it is -27 mass%, and it is especially preferable that it is 15-25 mass%. When the content of the maleimide compound unit exceeds 30% by mass, the flexibility of the solar cell backsheet becomes insufficient. Further, the maleimide compound unit may be derived from the rubber-reinforced vinyl resin (I-1) or may be derived from the (co) polymer (I-2). As described later, the glass transition temperature of the vinyl resin (I ′) can be adjusted by the content of the maleimide compound unit, and the (co) weight containing the maleimide compound unit as a constituent monomer. The union (I-2) is convenient for preparing a vinyl-based resin (I ′) 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 a maximum of 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. When the organosiloxane is a polyorganosiloxane, the molecular chain end 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 vinyl monomer (ii) in the present invention typically includes an aromatic vinyl compound and a vinyl cyanide compound, and preferably includes both an aromatic vinyl compound and a vinyl cyanide compound.

  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 to the aromatic vinyl compound and vinyl cyanide compound, the vinyl monomer (ii) may use other compounds copolymerizable with these. 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 such other compound used is preferably 0 to 50% by mass, more preferably 1 to 40% by mass, and further preferably 1 to 30% by mass, based on 100% by mass of the vinyl monomer (ii). .

  (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 and more preferably 1 to 30% by mass as the maleimide compound unit with respect to 100% by mass of the thermoplastic resin (I). 5 to 27% by mass is even more preferable, 10 to 27% by mass is even more preferable, and 15 to 25% by mass is particularly preferable. When the maleimide compound unit is less than 1% by mass, the heat resistance is insufficient. On the other hand, when it exceeds 30% by mass, the flexibility as a film may be insufficient.

  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 vinyl monomer (ii), it is preferable to mainly use an aromatic vinyl compound and a vinyl cyanide compound, and the total amount of these compounds is preferably from 70 to 70% based on the total amount of the vinyl monomer. It is 100 mass%, 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 styrene resin (I-1 ′) obtained by polymerizing a vinyl monomer (ii ′) containing an aromatic vinyl compound in the presence of the selected rubbery polymer (i), and optionally A rubber-reinforced styrene resin composed of a (co) polymer (I-2 ′) of a vinyl monomer (ii ′) 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 vinyl resin (I-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 vinyl resin (I-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 vinyl resin (I-1) in 20 ml of acetone (acetonitrile in the case of acrylic rubber) and shakes for 2 hours with a shaker at 25 ° C. After that, the mass (g) of insoluble matter obtained by centrifuging for 60 minutes with a centrifuge (rotation speed: 23,000 rpm) under a temperature condition of 5 ° C. to separate the insoluble matter and the soluble matter. Yes, T is the mass (g) of the rubber-like polymer contained in 1 gram of the rubber-reinforced vinyl resin (I-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 vinyl resin (I-1), the type and amount of polymerization initiator, and the addition of monomer components during polymerization. It can be adjusted by appropriately selecting the method, addition time, polymerization temperature and the like.

  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 vinyl resin (I-1) is preferably 0.1 to 2. 0.5 dl / g, more preferably 0.2 to 1.5 dl / g, still more preferably 0.25 to 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 (in the case of acrylic rubber, acetonitrile-soluble component) of the rubber-reinforced vinyl resin (I-1) was measured by the following method. First, the acetone-soluble component of the rubber-reinforced vinyl resin (I-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 vinyl resin (I-1), the type and amount of polymerization initiator, and the monomer used during polymerization. It can adjust by selecting suitably the addition method and addition time of a component, polymerization temperature, etc. Moreover, the said (co) polymer (I-2) which has different intrinsic viscosity [(eta)] can be adjusted by selecting suitably and mix | blending.

  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. It may be directly supplied to a machine or an extrusion molding machine to perform film processing or sheet processing. 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.

Colored resin layer of the present invention (layer (A))
The layer (A) of the present invention is an infrared transmissive colored resin layer, and specifically, a colored resin layer having an absorption rate of light having a wavelength of 800 to 1400 nm of 10% or less. The layer (A) can be constituted, for example, by adding a colorant, particularly an infrared transmitting colorant, to the resin component constituting the layer (A).
In the present invention, the absorptance of light having a wavelength of 800 to 1400 nm is 10% or less, which means that the minimum value of the absorptance in the wavelength range of 800 to 1400 nm is 10% or less. It is not required that the light absorptance of all the wavelengths is 10% or less. In general, it is considered that if the absorptance of light of a certain wavelength within a wavelength range of 800 to 1400 nm is 10% or less, the absorptance of light of a wavelength adjacent thereto is also lowered to the same extent.

  The infrared transmissive colorant absorbs visible light and develops color, but has a property of transmitting infrared light. Specific examples thereof include perylene black pigments. Such a perylene-based black pigment is commercially available as Paliogen Black S 0084, Paliogen Black L 0086, Lumogen Black FK4280, Lumogen Black FK4281 (trade name: manufactured by BASF). Moreover, the perylene-type pigment described in Unexamined-Japanese-Patent No. 2007-128943 can also be used as an infrared transparent colorant. Such infrared transmitting colorants can be used singly or in combination of two or more.

  Further, the infrared transmitting colorant can be used in combination with other pigments, dyes and other colorants as long as the infrared transparency of the layer (A) is not impaired. As other colorants, known inorganic pigments and organic pigments and dyes can be used. For example, when a yellow pigment is used in combination with the perylene black pigment, a brown layer (A) is obtained, and when a blue pigment is used in combination, an amber layer (A) is obtained, and a white pigment is used. When used in combination, a gray layer (A) is obtained.

The degree of coloration of the layer (A) is not particularly limited as long as the infrared transparency of the layer (A) is satisfied. Usually, the L value (lightness) of the surface on the layer (A) side of the solar cell backsheet is 40 or less. It is sufficient that the pigment is colored to an extent that it is preferably 35 or less, more preferably 30 or less. In addition, the surface on the layer (A) side of the solar cell backsheet means the surface of the layer (A) when the water vapor barrier layer (D) is not provided on the outer surface of the layer (A), When the water vapor barrier layer (D) is provided on the outer surface of the layer (A), it means the surface of the layer (D).
The content of the colorant in the layer (A) (total amount of the infrared transmissive colorant and other colorants) is not particularly limited as long as the infrared transmissive property of the layer (A) is not impaired. 0.1 to 5 parts by mass is preferable, 0.1 to 4.5 parts by mass is more preferable, and 0.5 to 4.0 parts by mass is even more preferable with respect to 100 parts by mass of the resin component constituting the component. If the content of the colorant is less than 0.1 parts by mass, coloring may be insufficient, and if the content of the colorant exceeds 5 parts by mass, infrared transmission may be insufficient or manufacturing costs may increase. There is.

  Although it does not restrict | limit especially as a resin component which comprises a layer (A), The thermoplastic resin (II) is preferable from the point of the moldability of a solar cell backsheet. Moreover, it is preferable that thermoplastic resin (II) has a glass transition temperature lower than thermoplastic resin (I) which comprises the said layer (B) from the point which provides flexibility to the solar cell backsheet. . 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.

  Examples of the thermoplastic resin (II) include styrene 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 (for example, (co) polymers of (meth) acrylate compounds), fluorine resins, ethylene / vinyl acetate resins, etc. It is done. These can be used individually by 1 type or in combination of 2 or more types. Among these, it is preferable to use styrene resin (II-1) from the viewpoint that hydrolysis does not easily occur even when used outdoors for a long period of time.

  The styrene resin (II-1) (hereinafter also referred to as “component (II-1)”) used in the present invention is typically an aromatic vinyl compound in the presence of the rubbery polymer (a). And, optionally, a rubber-reinforced styrene resin composition (II-1-1) obtained by polymerizing a vinyl monomer (b) comprising another monomer copolymerizable with the aromatic vinyl compound and / or It is a (co) polymer (II-1-2) of the vinyl monomer (b). The latter (co) polymer (II-1-2) is obtained by polymerizing the vinyl monomer (b) in the absence of the rubbery polymer (a). The rubber-reinforced styrene resin (II-1-1) is usually grafted onto a rubber polymer and a copolymer obtained by graft copolymerization of the vinyl monomer (b) onto the rubber polymer (a). Ungrafted component [the same as the above (co) polymer (II-1-2)].

  Component (II-1) of the present invention preferably contains at least one rubber-reinforced styrene-based resin (II-1-1) from the viewpoint of impact resistance and flexibility. You may contain a polymer (II-1-2). 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 20 parts by mass, with 100 parts by mass of the component (II-1). Especially preferably, it is 12-18 mass parts. 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 rubber polymer (a) used in the styrene resin (II-1) is the same as the rubber polymer (i) used in the thermoplastic resin (I). May be different or different.

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

  The styrene resin (II-1) preferably contains a maleimide compound unit from the viewpoint of heat resistance, and the maleimide compound unit with respect to 100% by mass of the styrene resin (II-1). The content of is usually preferably 0 to 30% by mass, more preferably 1 to 30% by mass, even more preferably 5 to 25% by mass, and 10 to 20% by mass. Particularly preferred. The maleimide compound unit may be derived from the rubber-reinforced styrene resin (II-1-1) or may be derived from the (co) polymer (II-1-2). The glass transition temperature of the styrene resin (II-1) can be adjusted by the content of the maleimide compound unit as described later, and a (co) polymer containing the maleimide compound unit as a constituent monomer. (II-1-2) is convenient for preparing a styrenic 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). Rubber-reinforced styrene resin (II-1-1) obtained by polymerizing vinyl monomer (b) containing an aromatic vinyl compound in the presence of selected rubbery polymer (a), and optionally A rubber-reinforced styrene resin composed of a (co) polymer (II-1-2) of the vinyl monomer (b) 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 styrenic resin (II-1) can be obtained by a known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, or a combination of these.

  The graft ratio of the rubber-reinforced styrene resin (II-1-1) is preferably 20 to 170%, more preferably 30 to 170%, 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 vinyl resin (I-1).

  The graft ratio is, for example, the type and amount of chain transfer agent used during the production of the rubber-reinforced styrene resin (II-1-1), the type and amount of polymerization initiator, and the monomer component during polymerization. The addition method, addition time, polymerization temperature, and the like can be appropriately selected.

  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 styrene resin (II-1-1) is preferably 0.1. -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 vinyl resin (I-1).

  The intrinsic viscosity [η] is, for example, the type and amount of chain transfer agent used in the production of the rubber-reinforced styrene 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 and mix | blending the said (co) polymer (II-1-2) which has different intrinsic viscosity [(eta)] suitably.

  The styrenic resin (II-1) 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. It may be directly supplied to a film forming machine or an extrusion molding machine to perform film processing or sheet processing. At this time, the styrene 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, Molds, tackifiers, plasticizers, colorants, graphite, carbo black, carbon nanotubes, and the like may be added as long as the object of the present invention is not impaired.

Colored resin layer of the present invention (layer (C))
The layer (C) of the present invention is a light-reflective colored resin layer. Specifically, the reflectance of light having a wavelength of 400 to 1400 nm is 50% or more, preferably 60% or more, particularly preferably 70% or more. This is a colored resin layer. The layer (C) can be formed, for example, by molding a resin in which a resin component constituting the layer (C) contains a colorant having high brightness. Accordingly, the degree of coloring of the layer (C) is not particularly limited as long as the reflectance is satisfied, but usually the L value (lightness) of the surface on the layer (C) side of the solar cell backsheet is preferably 55 or more, preferably Is 70 or more, more preferably 80 or more, and particularly preferably 95 or more. In addition, the surface on the layer (C) side of the solar cell backsheet means the surface of the layer (C) when the water vapor barrier layer (D) is not provided on the outer surface of the layer (C), When the water vapor barrier layer (D) is provided on the outer surface of the layer (C), it means the surface of the layer (D). In the present invention, a white surface or back surface is conventionally known for use in a solar battery backsheet. In the present invention, such a high whiteness layer functions as an infrared reflecting layer that has passed through the colored resin layer (A). I decided to let them.
In the present invention, the reflectance of light having a wavelength of 400 to 1400 nm is 50% or more means that the maximum value of reflectance in the wavelength range of 400 to 1400 nm is 50% or more, It does not require that the reflectance of light of all wavelengths 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 addition, since the layer (C) has a function of reflecting the infrared rays transmitted through the layer (A) and the layer (B), the reflectance of light having a wavelength of 800 to 1400 nm is 50% or more. The maximum reflectance in the wavelength range of 800 to 1400 nm is preferably 50% or more.

The colorant with high brightness blended in the layer (C) is not particularly limited as long as it has a property of reflecting infrared rays, and a white pigment is usually 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 content of the pigment in the layer (C) is not particularly limited as long as the infrared reflectivity of the layer (C) is not impaired, but the L value (brightness) of the surface on the layer (C) side of the solar cell backsheet is 55. It is preferable to contain an amount sufficient for the above, and specifically, 1 to 40 parts by mass is preferable and 3 to 40 parts by mass is more preferable with respect to 100 parts by mass of the resin component constituting the layer (C). 5-30 mass parts is still more preferable, and 10-25 mass parts is especially preferable. When the content is less than 1 part by mass, the effect of infrared reflection is not sufficient, and when it exceeds 40 parts by mass, the flexibility of the film becomes insufficient.

  As a resin component which comprises a layer (C), what was mentioned above about the layer (A) can be used, and the thermoplastic resin (II) is preferable from the point of the moldability of the solar cell backsheet. Moreover, it is preferable that thermoplastic resin (II) has a glass transition temperature lower than thermoplastic resin (I) which comprises the said layer (B) from the point which provides flexibility to the solar cell backsheet. . 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 descriptions including the description of the preferable thermoplastic resin (II) described above regarding the layer (A) are also applied to the resin component constituting the layer (C) as it is.

  According to a preferred embodiment of the present invention, as the thermoplastic resin (II) constituting the layer (C), acrylic rubber (i-3), silicone rubber (i-4), and silicone / acrylic composite rubber (i) -5) A rubber-reinforced styrene resin (II-1) obtained by polymerizing a vinyl 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 vinyl monomer (b). 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 an action of preventing water vapor from passing through the solar cell backsheet of the present invention, and is not particularly limited as long as this action is provided, but the layer (A) In the case of being provided between the outer surface or between the layer (A) and the layer (B) or between the layer (B) and the layer (C), as in the case of the layer (B). It is necessary to have sex. 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 may be laminated on the outer surface of layer (A) or layer (C) after obtaining a laminate comprising three layers (A), (B) and (C). Alternatively, before obtaining the laminate, the layers (A), (B) or the layer (C) may be laminated in advance, or the layers (A), (B) and (C) may be laminated at the same time. May be. The laminating method may be a method of laminating by an adhesive using a dry laminating method, and by coextrusion simultaneously with molding of at least one of the layers (A), (B) and the layer (C) without using an adhesive. A method of laminating or a method of laminating by coextrusion at the same time as forming the 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 layer (B) as a base material layer, an infrared transmissive colored resin layer (A) is disposed on one side thereof, and the other side. An infrared reflective colored resin layer (C) is disposed on the outer surface of the layer (A) or the layer (C), or between the layer (A) and the layer (B) or the layer ( A structure in which a water vapor barrier layer (D) is disposed between B) and the layer (C) is provided. Among these, it is preferable to provide a water vapor | steam barrier layer (D) on the outer surface of the said layer (A) or the said 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 layer (A). Since the layer (A) is disposed on the solar silicon cell S side, in this case, the layer (D) is advantageously protected by the layers (A) to (C). In the case where the synthetic resin film D1 is a material having poor hydrolysis resistance such as a polyethylene terephthalate (PET) film, the layer (D) is formed by replacing the thin film layer D2 with the layer (A) as shown in FIG. It is preferable to laminate toward the side. 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 layer (A), B is a layer (B), C is a layer (C), D is a layer (D), D1 is a synthetic resin film, and D2 is a thin film. Indicates the layer.

In preferable embodiment of the solar cell backsheet of this invention, as mentioned above, in order to provide heat resistance and flexibility to a solar cell backsheet, the said layer (B) is glass transition temperature 120 degreeC or more. The layer (A) and the layer (C) are composed of a styrene resin (II-1) having a glass transition temperature lower than that of the thermoplastic resin (I). The styrenic resin (II-1) constituting the layer (A) and the layer (C) is advantageously the same except for the pigment to be blended. The glass transition temperature (Tg (I)) of the thermoplastic resin (I) in the layer (B) and the glass transition temperature (Tg (I) of the styrene resin (II-1) constituting the layers (A) and (C). II)) preferably satisfies the following formula (3):
(Tg (I) −Tg (II)) ≧ 10 ° C. (3)
It is more preferable that the following formula (3 ′) is satisfied,
50 ° C. ≧ (Tg (I) −Tg (II)) ≧ 10 ° C. (3 ′)
It is more preferable that the following formula (3 ″) is satisfied.
30 ° C. ≧ (Tg (I) −Tg (II)) ≧ 15 ° C. (3 ″)

When the glass transition temperature of the thermoplastic resin (I) and the styrene resin (II-1) does not satisfy the formula (3), the effect of improving the flexibility of the solar cell backsheet obtained may be insufficient. is there. Moreover, when the difference between the glass transition temperature (Tg (I)) of the thermoplastic resin (I) and the glass transition temperature (Tg (II)) of the styrene resin (II-1) exceeds 50 ° C., for solar cells. The back sheet tends to be difficult to manufacture.
The glass transition temperature of the thermoplastic resin (I) (particularly the vinyl resin (I ′)) and the styrene resin (II-1) is the type or amount of the rubbery polymer (i) or (a) used, or , And can be adjusted by appropriately selecting the type or amount of the vinyl monomer (ii) or (b) to be used, 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 layer (B) and the styrene resin (II-1) of the layer (A) and the layer (C) are both of the above-mentioned silicone acrylic Resin comprising a silicone / acrylic composite rubber reinforced styrene resin obtained by polymerizing the vinyl monomer ((ii), (a)) to the composite rubber (i-5) and containing a maleimide compound unit A composition 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 layer (B) 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 N-phenylmaleimide unit is 100% by mass of the thermoplastic resin (I). The silicone / acrylic composite rubber reinforced styrene resin constituting the styrene resin (II-1) of the layer (A) and the layer (C) preferably has a rubber amount of styrene. 10 to 20 parts by mass with respect to 100 parts by mass of the resin based resin (II-1), the glass transition temperature is 120 to 140 ° C., and the content of the N-phenylmaleimide unit is 100 based on the styrene resin (II-1). 1 to mass% It is preferably 20% by mass.

  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, for example, 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.

The thickness of the solar cell backsheet of the present invention thus obtained is preferably 30 to 500 μm, more preferably 100 to 400 μm, and still more preferably 150 to 350 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.
The backsheet for a solar cell of the present invention, a layer a layer thickness of _{(A) (H A) (} C) the thickness of the _{(H C)} for the ratio _(H A / H _C) is, 0.75 ≦ _H A / _{H C} ≦ 1.25 is satisfied. By satisfying this condition, curling can be prevented from occurring in the solar cell backsheet.
As long as the water vapor barrier layer (D) has a thickness of 5 to 20 μm, the outer surface of the layer (A) or the layer (C) or the layer (A) and the layer (B) The curl is not generated in the solar cell backsheet of the present invention even when it is disposed between or between the layer (B) and the layer (C). Only a small amount of curl is generated.
The backsheet for a solar cell of the present invention, the layer (A) the ratio to the thickness _{(H A)} and a total thickness of the layer thickness _{(H C)} of the layer _{(C) (B) (H} B) of _{((H A} + H _C ) / H _B ) 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.

  Further, for example, when the total thickness of the solar cell backsheet is 250 μm, the thickness of the layer (A) / layer (B) / layer (C) / layer (D) is preferably 30 to 100/50 to 190. / 30 to 100/5 to 50 μm, more preferably 40 to 90/70 to 170/40 to 90/5 to 40 μm, and still more preferably 50 to 80/90 to 150/50 to 80/5 to 20 μm. When the thickness of the layer (A) and / or the layer (C) exceeds 100 μm, the heat resistance tends to be insufficient, whereas the thickness of the layer (A) and / or the layer (C) is less than 30 μm. The flexibility of the solar cell backsheet tends to be insufficient.

Furthermore, since the back sheet for a solar cell of the present invention is usually used as a surface on which the layer (A) receives light such as sunlight, it adheres to the surface of the layer (C) or the surface of the layer (D) as the back surface. By forming a layer or an adhesive layer, an adhesive film, an adhesive film, an adhesive sheet, an adhesive sheet or the like can be obtained. A protective film for protecting these layers may be further provided on the surface of the adhesive layer or the adhesive layer.
Moreover, between each layer of the back sheet | seat for solar cells, in the range which does not lose the effect of this invention, if desired, a decorative layer, the recycling resin produced at the time of manufacture (usually thermoplastic resin (I), thermoplastic resin ( It is also possible to laminate other layers such as layers consisting of II) and mixtures of these blends).

  The solar cell backsheet of the present invention can be suitably used particularly as 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. Among these, a transparent substrate, a sealing film, a solar cell element, and a sealing film comprise a solar cell silicon cell.

  Generally, glass is 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 generic 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, preferably polycrystalline silicon. This is due to the following reason. 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, and the energy ratio in the infrared region is large. Therefore, the power generation efficiency is further improved by using a combination of the solar cell backsheet of the present invention that has not only low heat storage but also infrared reflection characteristics and polycrystalline silicon as a solar cell element.

  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, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. 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. Absorption rate (%) of light having a wavelength of 800 to 1400 nm of the layer (A) alone
After forming the layer (A) having the thickness described in Table 4-1 or Table 4-2 alone with a T-die, the test piece (50 mm × 50 mm) was used and V-670 (wavelength range 200) manufactured by JASCO Corporation. ˜2700 nm), the transmittance and reflectance in the wavelength range of 800 to 1400 nm were measured, and the absorptance was determined based on the following equation.

1-5. Reflectance (%) of light having a wavelength of 400 to 1400 nm of the layer (C) alone
After forming a layer (C) having a thickness described in Table 4-1 or Table 4-2 alone with a T-die, the test piece (50 mm × 50 mm) was used and V-670 (wavelength range 200) manufactured by JASCO Corporation. The reflectance in the wavelength range of 400 to 1400 nm was measured by ˜2700 nm.

1-6. L value The L value of the single layer was measured with a spectrophotometer TCS-II manufactured by Toyo Seiki using a test piece of 50 mm × 50 mm × 100 μm. The L value of the laminate is the L value of the surface on the layer (A) side of the solar battery backsheet (the L value of the surface of the layer (D) in the following Examples 1 to 7 and Comparative Examples 2, 3 and 5) In Example 1, the L value of the surface of the layer (A)) and the L value of the surface on the layer (C) side (in Examples 1 to 7 below and Comparative Examples 1 to 3 and 5 of the layer (C) of the laminate) The L value of the surface was measured with the above spectrophotometer.

1-7. Heat resistance 1-7-1. Dimensional change rate after 30 minutes at 150 ° C. for the layer (B) alone (%)
100 mm (MD: resin extrusion direction from T die) × 100 mm (TD: orthogonal to MD) after forming a layer (B) having a thickness described in Table 4-1 or Table 4-2 alone with a T die Direction), draw a 50mm (MD) x 50mm (TD) square in the center of the surface of the test piece, leave it in a thermostatic bath at 150 ° C for 30 minutes, and then take it out to measure the dimensional change of the test piece in the MD and TD directions. did. 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.

1-7-2. Dimensional change rate after 30 minutes at 150 ° C of laminate (%)
It measured by the method similar to said 1-7-1 except having used the laminated body instead of the layer (B).

1-8. Flexibility (bending test)
A test piece of 100 mm (MD) × 100 mm (TD) was cut out from the solar cell backsheet, 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.

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.

1-9. Hydrolysis resistance (pressure cooker test)
1-9-1. Maintenance of breaking stress A test piece of 150 mm (MD) x 15 mm (TD) was cut out from a solar cell backsheet 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 (Shimadzu) The breaking stress of the test piece was measured in accordance with 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.

  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%.

1-9-2. Elongation retention The breaking elongation was measured simultaneously with the measurement of 1-9-1. 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%.

1-9-3. 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.
○: No curling (deformation).
X: There is curl (deformation).

1-10. 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 back sheet for solar cell sandwiched 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.

1-11. Thermal storage temperature In a chamber adjusted to a temperature of 25 ° C. ± 2 ° C. and a humidity of 50 ± 5% RH, an 80 mm × 50 mm (thickness is described in Table 4-1 or Table 4-2) solar cell backsheet test piece The surface (surface on the layer (A) side) was irradiated with an infrared lamp (output: 100 W) from a height of 200 mm, and the surface temperature of the test piece after 60 minutes was measured using a surface thermometer. The unit is ° C.

1-12. Weather resistance A test piece of 50 mm (MD) × 30 mm (TD) was cut out from the solar cell backsheet, and the exposure test was repeated by using the Metalling Weather Meter MV3000 (manufactured by Suga Test Instruments) under the conditions of Steps 1 to 4 below. The color change value ΔE before and after 100 hours of exposure was calculated.

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.

1-13. 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.

2. 2. Manufacturing method of solar cell backsheet 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. Infrared transparent organic black pigment (transparent black)
"Lumogne Black FK4280 (product name)" manufactured by BASF

2-1-8. Carbon black (black)
"Carbon black # 45 (trade name)" manufactured by Mitsubishi Chemical

2-1-9. Titanium oxide (white)
"Taipeke CR-60-2 (trade name)" manufactured by Ishihara Sangyo Co., Ltd.

2-2. Layer (A) (Infrared transparent colored resin layer)
The components described in Table 1 were mixed at a ratio described in Table 1 using a Henschel mixer, and then melt-kneaded with a twin-screw extruder (manufactured by Nippon Steel, TEX44, barrel temperature 270 ° C.) to form a pellet. The obtained composition was evaluated according to the above evaluation method. The results are shown in Table 1.

2-3. Layer (B) (base material layer)
The components listed in Table 2 were mixed by a Henschel mixer at the ratios listed in Table 2, and then melt-kneaded with a twin-screw extruder (manufactured by Nippon Steel Works, TEX44, barrel temperature 270 ° C.) to be pelletized. The obtained composition was evaluated according to the above evaluation method. The results are shown in Table 2.

2-4. Layer (C) (Infrared reflective colored resin layer)
The components described in Table 1 were mixed at a ratio described in Table 1 using a Henschel mixer, and then melt-kneaded with a twin-screw extruder (manufactured by Nippon Steel, TEX44, barrel temperature 270 ° C.) to form a pellet. The obtained composition was evaluated according to the above evaluation method. The results are shown in Table 1.

2-5. 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.

3. Manufacture of solar cell backsheets (Examples 1-8, Comparative Examples 1-9)
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 Table 4-1 or Table 4-2, the following is clear. Examples 1 to 8, which are backsheets for solar cells including the layer (A), the layer (B), the layer (C), and the layer (D) of the present invention, are formed of the layer (A) via the layer (D). It has a colored appearance by seeing through the color, has excellent flexibility, excellent water vapor barrier properties, good infrared transmittance, low heat storage, excellent heat resistance as a laminate, curl There was no occurrence and the power generation efficiency was improved. Moreover, Examples 1-7 which used the rubber | gum reinforcement | strengthening styrene-type resin for all of the layer (A), the layer (B), and the layer (C) were further excellent in hydrolysis resistance. In addition, the layer (A), the layer (B), and the layer (C) were all subjected to silicone / acrylic composite rubber reinforced styrene resin or a mixture of silicone rubber reinforced styrene resin and acrylic rubber reinforced styrene resin. Examples 1-6 were further excellent in weather resistance.

The comparative example 1 is an example which is not provided with a layer (D), and water vapor | steam barrier property was inferior. Comparative Example 2 uses an infrared absorbing carbon black instead of the infrared transmitting colorant of the layer (A), but the layer (A) has a high light absorptance of light having a wavelength of 800 to 1400 nm, and stores heat. Inferior in efficiency and power generation efficiency. Comparative Example 3 lacks the layer (B) of the present invention, has a large dimensional change rate (%) after 30 minutes at 150 ° C., and is inferior in heat resistance of the laminate. Comparative Example 4 is a white sheet that contains titanium oxide as a pigment in the layer (B) of the present invention and is used without the layers (A) and (C), but is inferior in flexibility. In Comparative Example 5, the layer (B) does not satisfy the heat resistance requirement of the present invention, but the layer (B) alone has a large dimensional change rate (%) after 150 ° C. for 30 minutes, and the heat resistance of the laminate. Inferior to sex. Comparative Examples 6 and 7 are examples of out of the range ratio to the thickness _{(H C) (H A /} H C) of the present invention the layer (C) of the thickness _{(H A)} of the layer (A), Carl Occurrence was seen. Comparative Examples 8 and 9, the layer ratio thicknesses _{(H B)} of the sum of the layer thickness _{(H C)} of the thickness of the _{(A) (H} A) and the layer _{(C) (B) ((} H A + H C) / H _B ) is an example outside the scope of the present invention, and was inferior to either the flexibility or heat resistance of the laminate.

  The solar cell backsheet of the present invention has the property of reflecting infrared rays to prevent heat storage while having a colored resin surface, and has excellent heat resistance and water vapor barrier properties, and further, weather resistance, Since it can also be excellent in hydrolysis resistance and flexibility, it can be used as a back sheet for a solar cell used in a severe environment exposed to sunlight.

It is sectional drawing which shows preferable embodiment of the solar cell backsheet of this invention.

Explanation of symbols

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

Claims (14)

The following layer (B) which is a base material layer;
The following layer (A) laminated on one side of the layer (B);
The following layer (C) laminated on the other side of the layer (B);
The outer surface of the layer (A) or the layer (C), or between the layer (A) and the layer (B) or between the layer (B) and the layer (C). A water vapor barrier layer (D);
The thickness (H _A ) of the following layer ( _A ), the thickness (H _B ) of the following layer ( _B ), and the thickness (H _C ) of the following layer ( _C ) are represented by the following formulas (1) and (2): ) Satisfying the solar cell back sheet.
Layer (A): a colored resin layer having an absorption rate of light having a wavelength of 800 to 1400 nm of 10% or less,
Layer (B): a thermoplastic resin layer having a dimensional change rate of ± 1% or less when left at 150 ° C. for 30 minutes,
Layer (C): a colored resin layer having a reflectance of 50% or more of light having a wavelength of 400 to 1400 nm.
_{0.75 ≦ H A / H C ≦} 1.25 ... (1)
_{0.4 ≦ (H A + H C} ) / H B ≦ 2.4 ... (2)   The L value (brightness) of the surface on the layer (A) side of the solar cell backsheet is 40 or less, and the L value (brightness) of the surface on the layer (C) side of the solar cell backsheet is 70 or more. The solar cell backsheet according to claim 1.   The solar cell backsheet according to claim 2, wherein the layer (A) is made of a resin containing an infrared transmitting colorant.   The solar cell backsheet according to claim 3, wherein the layer (C) is made of a resin containing a white pigment.   The layer (B) is made of a thermoplastic resin (I) having a glass transition temperature of 120 ° C. or higher, and the layer (A) and the layer (C) have a glass transition temperature lower than that of the thermoplastic resin (I). The solar cell backsheet according to claim 1, comprising a plastic resin (II).   The thermoplastic resin (II) is a vinyl monomer comprising an aromatic vinyl compound and optionally another monomer copolymerizable with the aromatic vinyl compound in the presence of the rubber polymer (a) ( a styrene-based resin containing a rubber-reinforced styrene-based resin (II-1-1) obtained by polymerizing b) and, if desired, a (co) polymer (II-1-2) of a vinyl-based monomer (b) The sun according to claim 5, wherein the content of the rubbery polymer (a) is 5 to 40 parts by mass with respect to 100 parts by mass of the styrene resin (II-1). Battery backsheet.   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. The solar cell backsheet according to claim 6.   The styrene resin (II-1) contains a maleimide compound unit as the vinyl monomer (b), and the maleimide compound unit is contained in 100% by mass of the styrene resin (II-1). The backsheet for solar cell according to claim 7, wherein the amount is 1 to 30% by mass.   The thermoplastic resin (I) is a rubber-reinforced vinyl resin (I-1) obtained by polymerizing a vinyl monomer (ii) in the presence of a rubbery polymer (i), and optionally a vinyl resin. It is a vinyl resin (I ′) containing the (co) polymer (I-2) of the monomer (ii), and the rubbery polymer (i) with respect to 100 parts by mass of the thermoplastic resin (I). The solar cell backsheet according to claim 5, wherein the content of the solar cell is 5 to 40 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. The solar cell backsheet according to claim 9.   The thermoplastic resin (I) comprises a maleimide compound unit as the vinyl monomer (ii), and the content of the maleimide compound unit is 1 to 100% by mass with respect to 100% by mass of the thermoplastic resin (I). It is 30 mass%, The solar cell backsheet of Claim 10. The glass transition temperature (Tg (I)) of the thermoplastic resin (I) is 120 to 220 ° C., and the glass transition temperature (Tg (II)) of the styrenic resin (II) is expressed by the following formula (3). The solar cell backsheet according to any one of claims 5 to 11, which is satisfied.
(Tg (I) −Tg (II)) ≧ 10 ° C. (3)   The solar cell backsheet according to claim 1, wherein the solar cell backsheet has a thickness of 150 to 350 μm.   A solar cell module comprising the solar cell backsheet of claim 1.

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