WO2009113174A1 - Back sheet for solar cell and solar cell module employing the same - Google Patents

Abstract

A back sheet for solar cells which is composed of superposed layers comprising a weatherable resin layer (1), a water-vapor-barrier layer (2), an adhesive layer (3), and a plastic film (4); and a solar cell module employing the back sheet. The weatherable resin layer (1) is obtained from a resin composition comprising: a vinyl copolymer (A) obtained by grafting a polyester to a copolymer obtained from monomers including an unsaturated dibasic acid as an essential ingredient; a polyisocyanate compound (B); and a polyester (C). The back sheet for solar cells is inexpensive and has excellent long-term outdoor weatherability.

Description

Solar cell backsheet and solar cell module using the same

The present invention relates to a solar cell backsheet in which a weather-resistant resin layer, a water vapor barrier layer, an adhesive layer and a plastic film are laminated. Specifically, the present invention relates to a solar cell backsheet that is inexpensive and has long-term outdoor weather resistance. Furthermore, this invention relates to the solar cell module which uses the said solar cell backsheet.

In recent years, solar cells have been attracting attention as a clean energy source free from environmental pollution due to increasing awareness of environmental problems, and earnestly researched and put into practical use in terms of the use of solar energy as a useful energy resource. There are various types of solar cells, and typical examples thereof include crystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, copper indium selenide solar cells, compound semiconductor solar cells and the like. ing. Among these, thin-film crystal solar cells, amorphous silicon solar cells, and compound semiconductor solar cells are relatively low in cost and can be increased in area, and therefore are actively researched and developed in various fields. Among these solar cells, thin-film solar cells typified by amorphous silicon solar cells in which silicon is laminated on a conductive metal substrate and a transparent conductive layer is further formed thereon are lightweight and impact resistant. It is promising as a future module form in solar cells because of its high flexibility.

By the way, these solar cells are provided with a surface protection sheet on the side where sunlight is incident for the purpose of protecting the surface. A back surface protection sheet is provided for the purpose of protecting the battery element (Patent Document 1, etc.).

Conventionally, the following sheets are known as back protection sheets for solar cells (back sheets for solar cells).
Patent Document 1 describes a back sheet made of a hydrolysis-resistant resin film made of a resin such as polyethylene terephthalate or polycarbonate, a resin film to which a metal oxide is attached, and a white resin film.
In Patent Document 2, a vapor deposition layer is provided on one surface of a base film made of various resins such as a cyclic polyolefin-based resin and a polycarbonate-based resin, and a hue is mutually formed on the vapor deposition layer and the other surface of the base film. The back surface protection sheet for solar cell modules which each provided the heat-resistant polyolefin-type resin film from which these differ is described.
Patent Document 3 describes a back protective sheet for a solar cell that uses a resin sheet made of a polyethylene resin on at least one layer of a polypropylene resin sheet.
However, the polyolefin resin and polycarbonate resin used for these backside protection sheets are not sufficiently weather resistant outdoors, so that when used for a long period of time, the appearance of the solar cell backsheet is impaired or curled. There is a problem that the output of the solar cell module is further reduced.

On the other hand, in Patent Document 4, an inorganic vapor deposition layer is provided on a weather-resistant substrate made of various resins such as a fluorine resin, a cyclic polyolefin resin, and a polycarbonate resin, and a colored polyester resin layer is formed on the inorganic vapor deposition layer. The back surface protection sheet for solar cells which laminated | stacked is described. Further, Patent Documents 5 and 6 also describe a back protective sheet for solar cells using a fluororesin film.
When using a fluorine-based resin film for a solar cell back surface protective sheet, there is a problem that the price of the fluorine-based resin film is high and the supply amount is small, making it difficult to obtain. Moreover, the back surface protection sheet for solar cells using a fluorine-type resin film also had the problem of being easy to curl.
Japanese Patent Laid-Open No. 2002-100788 Japanese Patent Laid-Open No. 2004-200322 JP 2004-223925 A Japanese Patent Laid-Open No. 2001-119051 JP 2003-347570 A JP 2004-352966 A

An object of the present invention is to provide a solar cell backsheet that overcomes conventional problems, is inexpensive, and has excellent long-term outdoor weather resistance, and a solar cell module that uses the solar cell backsheet.

The first invention is a solar cell backsheet having a weather resistant resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3) and a first plastic film (4),
The weather resistant resin layer (1) is
At least one unsaturated dibasic acid (a1) selected from maleic acid, maleic anhydride, fumaric acid, mesaconic acid, citraconic acid and citraconic anhydride and other monomers having an ethylenically unsaturated double bond ( a copolymer having a weight average molecular weight of 5,000 to 500,000, a functional group capable of reacting with a carboxyl group and / or an acid anhydride group, and an isocyanate group A vinyl copolymer (A) which is a graft polymer obtained by condensation and / or addition reaction with a polyester (b) having a functional group capable of reacting with a polyester and having a weight average molecular weight of 500 to 25,000 ,
Polyisocyanate compound (B) containing two or more isocyanate groups, and polyester (C) having two or more functional groups capable of reacting with isocyanate groups
A resin composition comprising:
In the vinyl copolymer (A) and the polyester (C), the number of isocyanate groups of the polyisocyanate compound (B) is 0.1 to 5.0 times the total number of functional groups capable of reacting with isocyanate groups. It is related with the solar cell backsheet characterized by being formed from the resin composition which is.

In the second invention, the copolymer (a) is:
At least one unsaturated dibasic acid (a1) selected from maleic acid, maleic anhydride, fumaric acid, mesaconic acid, citraconic acid and citraconic anhydride,
Monomer (a21) which has a functional group capable of reacting with an isocyanate group and an ethylenically unsaturated double bond, does not belong to the unsaturated dibasic acid (a1), and has an ethylenically unsaturated double bond The solar cell according to the first aspect of the present invention is a copolymer comprising the monomer (a22) which does not belong to any of the unsaturated dibasic acid (a1) and the monomer (a21). It is related with the back sheet.

In a third aspect of the present invention, the water vapor barrier layer (2) is a metal foil (21), or the metal oxide or the nonmetal inorganic oxide (22) is at least one surface of the second plastic film (23). It is the plastic film with a vapor deposition layer (24) vapor-deposited in (1), It is related with the solar cell backsheet of 1st or 2nd invention characterized by the above-mentioned.

According to a fourth aspect of the present invention, there is provided a vapor-deposited layer plastic film in which the water vapor barrier layer (2) is a metal oxide or non-metal inorganic oxide (22) deposited on at least one surface of the second plastic film (23) (24) is a laminated body in which two or more layers are laminated, and relates to a solar cell backsheet according to any one of the first to third inventions.

5th invention is located in the location which the vapor deposition layer which comprises the plastic film (24) with a vapor deposition layer contacts the 1st adhesive bond layer (3), It describes to 3rd or 4th invention characterized by the above-mentioned. The present invention relates to a solar cell backsheet.

The sixth invention is the solar cell backsheet according to any one of the first to fifth inventions, wherein the first plastic film (4) is a colorless or colored polyethylene terephthalate film. About.

According to a seventh aspect of the present invention, the weather resistant resin layer (1), the water vapor barrier layer (2), the first adhesive layer (3) and the first plastic film (4) are sequentially laminated in the order described above. The present invention relates to a solar cell backsheet according to any one of the first to sixth inventions.

The eighth invention further comprises a third plastic film (5) and a second adhesive layer (6), a weather resistant resin layer (1), a second plastic film (5), and a second adhesive. The agent layer (6), the water vapor barrier layer (2), the first adhesive layer (3), and the first plastic film (4) are sequentially laminated in the order described above. The present invention relates to a solar cell backsheet according to any one of the inventions.

The ninth invention further includes a fourth plastic film (7) and a third adhesive layer (8), the fourth plastic film (7), the third adhesive layer (8), and weather resistance. The resin layer (1), the water vapor barrier layer (2), the first adhesive layer (3) and the first plastic film (4) are sequentially laminated in the order described above, or the fourth plastic film ( 7), third adhesive layer (8), weather resistant resin layer (1), second plastic film (5a), second adhesive layer (6), water vapor barrier layer (2), first The solar cell backsheet according to the seventh or eighth invention, wherein the adhesive layer (3) and the first plastic film (4) are sequentially laminated in the order described above.

A tenth invention is a solar cell module using the solar cell backsheet of any of the seventh to ninth inventions, wherein the first plastic film (4) constituting the solar cell backsheet is provided. In addition, the present invention relates to a solar cell module, which is in direct contact with the solar cell element sealing layer (10) through or without a fourth adhesive layer (9).

The present invention provides a solar cell backsheet that is inexpensive and has long-term outdoor weather resistance, and a solar cell module using the backsheet.

A typical solar cell backsheet of the present invention comprising a weatherable resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3) and a first plastic film (4) laminated. It is sectional drawing. Weather resistant resin layer (1), third plastic film (5), second adhesive layer (6), water vapor barrier layer (2), first adhesive layer (3) and first plastic film base It is typical sectional drawing which shows another aspect of the solar cell backsheet of this invention formed by laminating | stacking material (4). Fourth plastic film (7), third adhesive layer (8), weather resistant resin layer (1), water vapor barrier layer (2), first adhesive layer (3) and first plastic film ( It is typical sectional drawing which shows another aspect of the solar cell backsheet of this invention formed by laminating | stacking 4).

Explanation of symbols

1: Weather-resistant resin layer 2: Water vapor barrier layer 3: First adhesive layer 4: First plastic film 5: Third plastic film 6: Second adhesive layer 7: Fourth plastic film 8: Third adhesive layer

The weather resistant resin layer (1) constituting the solar cell backsheet of the present invention will be described.
The weather-resistant resin layer (1) includes the vinyl copolymer (A), the polyisocyanate compound (B) containing two or more isocyanate groups, and two or more functional groups capable of reacting with isocyanate groups. It is formed from the resin composition containing the said polyester (C) to have. The vinyl copolymer (A) (hereinafter also simply referred to as “copolymer (A)”) is:
Copolymerization of at least one unsaturated dibasic acid selected from maleic acid, maleic anhydride, fumaric acid, mesaconic acid, citraconic acid and citraconic anhydride with another monomer having an ethylenically unsaturated double bond A copolymer (a) having a weight average molecular weight of 5,000 to 500,000,
Condensation with a polyester (b) having a functional group capable of reacting with a carboxyl group and / or an acid anhydride group and a functional group capable of reacting with an isocyanate group and having a weight average molecular weight of 500 to 25,000 and / or Alternatively, it is a graft polymer obtained by an addition reaction, and is used for imparting toughness, extensibility, flexibility, molding processability, weather resistance, and / or chemical resistance to the weather resistant resin layer (1).

The copolymer (A) is introduced as a side chain by grafting the polyester (b) to the main chain of the copolymer (a) obtained by polymerizing a monomer having an ethylenically unsaturated double bond. This is a polymer into which a functional group capable of reacting with an isocyanate group is introduced.

Examples of the functional group capable of reacting with an isocyanate group in the polyester (b) include a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an N-methylol group, and an N-alkoxymethyl group. Is preferred.

The specific method for introducing the side chain is not particularly limited. For example, first, the unsaturated dibasic acid (a1) and the other monomer having an ethylenically unsaturated double bond may be used together. Functionality capable of synthesizing the polymer (a) and then reacting with the carboxyl group and / or acid anhydride group in the copolymer (a) and the carboxyl group and / or acid anhydride group in the polyester (b) By condensation and / or addition reaction with a group, the polyester (b) can be grafted onto the main chain of the copolymer (a) and introduced as a side chain.

In addition, when higher toughness and weather resistance are required, a functional group capable of reacting with an isocyanate group is provided in the main chain of the vinyl copolymer (A) in order to obtain a higher crosslinking density. It is desirable to introduce. In that case, the copolymer (A) has an unsaturated dibasic acid (a1), a functional group capable of reacting with an isocyanate group, and an ethylenically unsaturated double bond. Monomer (a21) not belonging to (a1) and a single amount having an ethylenically unsaturated double bond and not belonging to any of the unsaturated dibasic acid (a1) and the monomer (a21) A copolymer (a) of the body (a22) is prepared, and subsequently, the copolymer (a), a functional group capable of reacting with a carboxyl group and / or an acid anhydride group, and an isocyanate group can be reacted. It can be obtained by condensation and / or addition reaction with polyester (b) having a functional group.

The unsaturated dibasic acid (a1) that can be used for the synthesis of the copolymer (a) is at least one selected from maleic acid, maleic anhydride, fumaric acid, mesaconic acid, citraconic acid, and citraconic anhydride. Unsaturated dibasic acids other than the unsaturated dibasic acid (a1) may be further used as necessary. Examples thereof include itaconic acid, crotonic acid, diphenylmethane-di-γ-ketocrotonic acid, and the like.

The unsaturated dibasic acid (a1) can be used singly or in combination of two or more depending on the performance required for the weather resistant resin layer (1). The proportion of the unsaturated dibasic acid (a1) in the total 100% by weight of the monomers constituting the copolymer (a) is preferably 0.01 to 30% by weight, more preferably 0.05 to 10% by weight. When the proportion of the unsaturated dibasic acid (a1) exceeds 30% by weight, the stability of the resulting copolymer (A) is lowered, and when it is less than 0.01% by weight, the resulting weather resistant resin The stretchability or flexibility of the layer (1) becomes insufficient.

The monomer (a21) having a functional group capable of reacting with an isocyanate group and an ethylenically unsaturated double bond and not belonging to the unsaturated dibasic acid (a1) is a functional group capable of reacting with an isocyanate group. A (meth) acrylic monomer having vinyl or a vinyl monomer can be used. Among these, a (meth) acrylic monomer is preferable in terms of reactivity and molding processability of the resulting weather resistant resin layer.

Examples of the functional group capable of reacting with an isocyanate group include a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an N-methylol group, and an N-alkoxymethyl group. From the viewpoint of properties, a hydroxyl group is preferred.

Examples of the (meth) acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Examples include polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, and polytetramethylene glycol mono (meth) acrylate.

Examples of (meth) acrylic monomers having an amino group include methylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate, butylaminoethyl (meth) acrylate, or t-butylaminoethyl (meth) acrylate Monoalkylaminoalkyl (meth) acrylate,
N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, or N, N-dialkylaminoethyl (meth) acrylate such as N, N-dibutylaminoethyl (meth) acrylate Can be mentioned.
Examples of the (meth) acrylic monomer having a carboxyl group include acrylic acid and methacrylic acid.

Examples of the (meth) acrylic monomer having an epoxy group include glycidyl (meth) acrylate.

Examples of the (meth) acrylic monomer having an N-methylol group include N-methylol (meth) acrylamide, N, N-dimethylol (meth) acrylamide and the like.

Examples of (meth) acrylic monomers having an N-alkoxymethyl group include N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, and N-butoxymethyl. (Meth) acrylamide having an N-monoalkoxymethyl group such as (meth) acrylamide,
N, N-di (methoxymethyl) (meth) acrylamide, N, N-di (ethoxymethyl) (meth) acrylamide, N, N-di (propoxymethyl) (meth) acrylamide, or N, N-di (butoxy) And (meth) acrylamide having an N, N-dialkoxymethyl group such as (methyl) (meth) acrylamide.
Examples of the vinyl monomer include hydroxystyrene or vinyl alcohol.

A monomer (a21) having a functional group capable of reacting with an isocyanate group and an ethylenically unsaturated double bond and not belonging to the unsaturated dibasic acid (a1) is required for the weather resistant resin layer (1). Depending on the performance to be performed, one kind or a combination of two or more kinds can be used. The proportion of the monomer (a21) is preferably 0.01 to 50% by weight, more preferably 0.1 to 20% by weight based on 100% by weight of the monomers constituting the copolymer (a). %, More preferably 0.1 to 10% by weight. When the proportion of the monomer (a21) exceeds 50% by weight, the storage stability of the obtained copolymer (A) decreases, and when it is less than 0.01% by weight, the resulting resin composition Pigment dispersibility, weather resistance resin layer toughness, weather resistance, and solvent resistance are reduced.

As the monomer (a22) having an ethylenically unsaturated double bond and not belonging to any of the unsaturated dibasic acid (a1) and the monomer (a21), a (meth) acrylic monomer Body, aromatic vinyl monomer, olefinic hydrocarbon monomer, vinyl ether monomer or the like.
Examples of the (meth) acrylic monomer as the monomer (a22) include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Or alkyl (meth) acrylate such as stearyl (meth) acrylate, benzyl (meth) acrylate, and the like.
Examples of the aromatic vinyl monomer include styrene, methyl styrene, and ethyl styrene.
Examples of the olefinic hydrocarbon monomer include ethylene, propylene, butadiene, isobutylene, isoprene, and 1,4-pentadiene.
Examples of vinyl ether monomers include vinyl methyl ether.
The monomer (a22) having an ethylenically unsaturated double bond and not belonging to any of the unsaturated dibasic acid (a1) and the monomer (a21) is added to the weather resistant resin layer (1). Depending on the required performance, one or a combination of two or more can be used.

The proportion of the monomer (a22) in the total 100% by weight of the monomers constituting the copolymer (a) is preferably 50 to 99.95% by weight, more preferably 75 to 99.5% by weight, More preferably, it is 90 to 99% by weight. When the proportion of the monomer (a22) exceeds 99.95% by weight, the resulting resin composition loses its extensibility, and when it is less than 50% by weight, the resulting copolymer (A) is stored. Stability is reduced.

The copolymer (a) can be obtained by a known method, for example, solution polymerization. Examples of the solvent include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether, or diethylene glycol methyl ether,
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone;
Ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, or diethylene glycol dimethyl ether;
Hydrocarbons such as hexane, heptane, or octane,
Aromatics such as benzene, toluene, xylene, or cumene,
Esters such as ethyl acetate or butyl acetate can be used.
Two or more solvents may be mixed and used.

The charging concentration of all monomers during the synthesis is preferably 0.1 to 80 parts by weight with respect to 100 parts by weight of the solvent.
As the polymerization initiator, a peroxide or an azo compound can be used, and examples thereof include benzoyl peroxide, azoisobutylvaleronitrile, azobisisobutyronitrile, di-t-butyl peroxide, t -Butyl perbenzoate, t-butyl peroctoate, cumene hydroxy peroxide and the like can be mentioned.
The polymerization temperature is preferably 50 to 200 ° C, particularly 70 to 140 ° C.
It is important that the copolymer (a) has a polystyrene-reduced weight average molecular weight by gel permeation chromatography (GPC) of 5,000 to 500,000, preferably 10,000 to 300,000. . When the weight average molecular weight of the copolymer (a) exceeds 500,000, the extensibility of the resulting weather resistant resin layer is lowered, and when it is less than 5,000, the toughness of the obtained weather resistant resin layer is reduced. And chemical resistance are reduced.

The glass transition temperature of the copolymer (a) is preferably 0 to 150 ° C., more preferably 5 to 100 ° C. When the glass transition temperature of the copolymer (a) exceeds 150 ° C., the extensibility of the resulting weather resistant resin layer decreases, and when it is less than 0 ° C., the chemical resistance of the obtained weather resistant resin layer. , Surface hardness decreases.

Examples of the polyester (b) used in the present invention include a functional group capable of reacting with a carboxyl group and / or an acid anhydride group and a functional group capable of reacting with an isocyanate group at a linear terminal or a branched terminal. A polyester having one or more of each can be used.

Examples of the functional group capable of reacting with a carboxyl group and / or an acid anhydride group in the polyester (b) include a hydroxyl group, an epoxy group, an amino group, and an isocyanate group. Hydroxyl groups are preferred in terms of moldability.
Examples of the functional group capable of reacting with the isocyanate group in the polyester (b) include a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an N-methylol group, and an N-alkoxymethyl group. A hydroxyl group is preferable in terms of the moldability of the weatherable resin layer to be obtained.
In the polyester (b), the functional group capable of reacting with the carboxyl group and / or the acid anhydride group and the functional group capable of reacting with the isocyanate group may be the same functional group or different functional groups.

Examples of the polyester (b) include a terminal hydroxyl group-containing polyester obtained by esterifying at least one dicarboxylic acid and at least one polyol such as a polyhydric alcohol, a polyhydric phenol, or an alkoxy modified product thereof, And a polyester in which the terminal hydroxyl group is modified with an amino group, a carboxyl group, an epoxy group, an N-methylol group, or an N-alkoxymethyl group.

Examples of dicarboxylic acids used in the production of polyester (b) include terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalic acid, 1,4-cyclohexanedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacin Examples thereof include dicarboxylic acids such as acid and dodecanedicarboxylic acid.

Examples of the polyhydric alcohol used in the production of the polyester (b) include 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 2-methyl-1,4- Butanediol, 1,2-dimethyl-1,4-butanediol, 2-ethyl-1,4-butanediol, 1,5-pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1 , 5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-ethyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 1,7-heptanediol, 2-methyl-1,7-heptanediol, 3-methyl-1,7-heptanediol, 4- Til-1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 2-ethyl-1,8-octanediol, 3-methyl-1,8-octanediol, 4 -Methyl-1,8-octanediol, 1,9-nonanediol, ethylene glycol, propylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol, cyclohexanedimethanol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, trimethylol Examples include propane, 1,1,1-trimethylolpropane ethylene glycol, glycerin, erythritol, xylitol, sorbitol, or mannitol.

Examples of the polyhydric phenol used in the production of the polyester (b) include catechol, resorcin, hydroquinone, hexyl resorcin, trihydroxybenzene, dimethylolphenol, and the like.

As a commercially available polyester having two or more hydroxyl groups (polyester polyol), for example,
Kuraray polyols P-510, P-1010, P-1510, P-2010, P-3010, P-4010, P-5010, P-6010, P-2011, P-2013, P-520 manufactured by Kuraray Co., Ltd. , P-1020, P-2020, P-1012, P-2012, P-530, P-1030, P-2030, PMHC-2050, PMHC-2050R, PMHC-2070, PMHC-2090, PMSA-1000, PMSA -2000, PMSA-3000, PMSA-4000, F-2010, F-3010, N-2010, PNOA-1010, PNOA-2014, O-2010,
Desmophene 650MPA, 651MPA / X, 670, 670BA, 680X, 680MPA, 800, 800MPA, 850, 1100, 1140, 1145, 1150, 1155, 1200, 1300X, 1652, 1700, 1800, RD181, manufactured by Sumitomo Bayer Urethane Co., Ltd. Byron 200, 560, 600 manufactured by Toyobo Co., Ltd., GK130, GK860, GK870, 290, GK590, GK780, GK790, etc. may be mentioned.

It is important that the weight average molecular weight of the polyester (b) is 500 to 25,000.
When the weight average molecular weight of the polyester (b) exceeds 25,000, the solubility in a solvent, the compatibility with the copolymer (a), and the reactivity with the copolymer (a) are reduced. The toughness of the resulting weather resistant resin layer is reduced. Moreover, when it is less than 500, sufficient extensibility and a softness | flexibility cannot be provided to a weather resistant resin layer.

The copolymer (A) includes a carboxyl group and / or an acid anhydride group in the copolymer (a), and a functional group capable of reacting with the carboxyl group and / or the acid anhydride group in the polyester (b). Can be obtained by condensation and / or addition reaction.
For example, when the functional group capable of reacting with a carboxyl group and / or an acid anhydride group in the polyester (b) is a hydroxyl group or an epoxy group, it is esterified, when it is an amino group, it is amidated, and when it is an isocyanate group, it is imidized. Can be obtained respectively.
As the reaction solvent, the solvent at the time of synthesizing the copolymer (a) can be used as it is, and, depending on the conditions at the time of synthesis and the conditions at the time of coating, other solvents can be added or desolvated. It doesn't matter.

As the reaction catalyst, for example, tertiary amine such as triethylamine, triethanolamine or ethylenediamine is used, and the reaction temperature is preferably 50 to 300 ° C.

The reaction ratio between the copolymer (a) and the polyester (b) is such that the carboxyl groups and / or the acid anhydride groups in the copolymer (a) The functional group capable of reacting with the acid anhydride group is preferably from 0.01 to 10 mol, more preferably from 0.1 to 5 mol, further preferably from 0.5 to 2 mol. preferable. When it exceeds 10 mol, the coating property of the resin composition and the toughness of the weather resistant resin layer are impaired, and when it is less than 0.01 mol, the extensibility and flexibility of the resulting weather resistant resin layer are impaired. descend.

Further, it is not always necessary to use one kind of each of the copolymer (a) and the polyester (b), and a plurality of kinds may be used depending on the purpose and necessary physical properties.

When the copolymer (A) has a hydroxyl group, the hydroxyl value is preferably 0.1 to 300 mgKOH / g, more preferably 1 to 100 mgKOH / g, still more preferably 1 to 50 mgKOH / g in terms of solid content. . When the hydroxyl value of the copolymer (A) exceeds 300 mgKOH / g, the storage stability of the copolymer (A) decreases, and when it is less than 0.1 mgKOH / g, the pigment dispersibility of the resin composition The toughness, extensibility, and chemical resistance of the resulting weather resistant resin layer are lowered.

The weight average molecular weight in terms of polystyrene by GPC of the copolymer (A) is preferably 5,000 to 500,000, more preferably 10,000 to 300,000. When the weight average molecular weight of the copolymer (A) exceeds 500,000, the solubility in a solvent and the extensibility of the weather resistant resin layer are lowered. When the copolymer (A) is less than 5,000, the resulting weather resistance is reduced. The toughness and chemical resistance of the resin layer are reduced.

The polyisocyanate compound (B) having two or more isocyanate groups constituting the present invention (hereinafter also simply referred to as “compound (B)”) is a copolymer (A), polyester (C) described later. Furthermore, the copolymer (A) and the polyester (C) are cross-linked to form a tough weather-resistant resin layer having extensibility, flexibility, molding processability, and chemical resistance.
In order to prevent the resulting weather resistant resin layer from changing from yellow to brown over time, it is preferable to use only an alicyclic or aliphatic compound, but an aromatic polyisocyanate compound can also be used.

Examples of the alicyclic polyisocyanate compound include isophorone diisocyanate, hydrogenated tolylene diisocyanate, or hydrogenated 4,4'-diphenylmethane diisocyanate.

Examples of the aliphatic polyisocyanate compound include trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, or lysine diisocyanate.

Examples of the aromatic polyisocyanate compound include diphenylmethane diisocyanate, toluylene diisocyanate, naphthylene-1,5-diisocyanate, o-xylene diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, triphenylmethane triisocyanate, or polymethylene polyisocyanate. Examples thereof include phenyl isocyanate.

The polyisocyanate compound (B) is a reaction product of the above compound [that is, the above-described alicyclic, aliphatic, or aromatic polyisocyanate compound exemplified as the compound (B)] with glycols or diamines. You may use a both terminal isocyanate adduct body, biuret modified body, or isocyanurate modified body.
In particular, when the polyisocyanate compound (B) contains an isocyanurate-modified product, particularly an isocyanurate ring-containing triisocyanate, it is preferable because a weather-resistant resin layer having toughness and extensibility can be obtained. Specific examples of the isocyanurate ring-containing triisocyanate include isocyanurate-modified isophorone diisocyanate (for example, Desmodule Z4470 manufactured by Sumitomo Bayer Urethane Co., Ltd.), isocyanurate-modified hexamethylene diisocyanate (for example, Sumidur manufactured by Sumitomo Bayer Urethane Co., Ltd.) N3300), isocyanurate-modified toluylene diisocyanate (for example, Sumidur FL-2, FL-3, FL-4, HL BA manufactured by Sumitomo Bayer Urethane Co., Ltd.).

The isocyanate group of the polyisocyanate compound (B) is, for example, methanol, ethanol, n-pentanol, ethylene chlorohydrin, isopropyl alcohol, phenol, p-nitrophenol, m-cresol, acetylacetone, ethyl acetoacetate, Alternatively, a block modified product obtained by blocking with a blocking agent such as ε-caprolactam may be used as the polyisocyanate compound (B).

Furthermore, as the polyisocyanate compound (B), a polyester (c) having two or more functional groups capable of reacting with an isocyanate group and a diisocyanate compound (d) having an isocyanate group at both ends are reacted. An isocyanate prepolymer may be used. When the polyisocyanate compound (B) contains the above-mentioned both-end isocyanate prepolymer, extensibility is obtained in a small amount, and the toughness of the coating film is not impaired.
A polyisocyanate compound (B) can be used 1 type or in combination of 2 or more types.

As the polyester (c) having two or more functional groups capable of reacting with an isocyanate group, the same polyester as the compound exemplified as the polyester (b) can be used.
Examples of the diisocyanate compound (d) having isocyanate groups at both ends include, for example, toluylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluylene diisocyanate, diphenylmethane diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4 ′. -Diphenylmethane diisocyanate, hexamethylene diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, lysine diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, or hydrogenated tolylene diisocyanate.

Both terminal isocyanate prepolymers are in a ratio such that the isocyanate group in the compound (d) is larger than 1 mole with respect to 1 mole of the functional group capable of reacting with the isocyanate group in the polyester (c). It is obtained by mixing the compound (d) and reacting by heating and stirring. The polystyrene equivalent weight average molecular weight of the prepolymer by GPC is preferably 500 to 50,000, more preferably 1,000 to 50,000, and still more preferably 1,000 to 10,000. When the weight average molecular weight of the prepolymer exceeds 50,000, solubility in a solvent and compatibility with other components decrease, and when it is less than 500, the toughness and elongation of the resulting weather resistant resin layer Lack of sex.

In order to impart flexibility and / or extensibility to the resulting weather resistant resin layer (1), and to impart resin pigment dispersibility to the resin composition forming the weather resistant resin layer (1), In order to increase the crosslinking density of the copolymer (A) and further improve the toughness, extensibility, and / or flexibility of the weather resistant resin layer (1), functional groups capable of reacting with isocyanate groups are added. It is important to contain two or more polyesters (C).

The polyester (C) is, for example, a polyester having two or more functional groups capable of reacting with an isocyanate group at a linear end or a branched end.

Examples of the functional group capable of reacting with an isocyanate group include a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an N-methylol group, or an N-alkoxymethyl group. Reactivity and molding of the resulting weather resistant resin layer From the viewpoint of processability, a hydroxyl group is preferred.

Further, the number of functional groups capable of reacting with an isocyanate group is particularly preferably 3, since it can be stretched in a small amount as compared with the case of 2 and the toughness of the coating film is not impaired.
As polyester (C), the polyester similar to the compound illustrated as said polyester (b) can be used.

The weight average molecular weight in terms of polystyrene by GPC of the polyester (C) is preferably 500 to 25,000, more preferably 1,000 to 10,000. When a weight average molecular weight exceeds 25,000, the solubility to a solvent will fall and the extensibility of the weather resistant resin layer (1) obtained will fall. On the other hand, if it is less than 500, the compatibility with other components decreases, making it difficult to produce a uniform and smooth weather-resistant resin layer (1), and the toughness of the resulting weather-resistant resin layer (1). Decreases.

Polyester (C) can be used alone or in combination of two or more depending on the performance required for the weather resistant resin layer (1).

The mixing ratio (weight ratio) of the copolymer (A) and the polyester (C) is preferably (A) / (C) = 95/5 to 10/90, more preferably (A) / (C) = 95/5 to 30/70, more preferably (A) / (C) = 95/5 to 50/50. When the ratio of polyester (C) exceeds 90, the toughness or chemical resistance of the resulting weather resistant resin layer (1) becomes low.

The resin composition for forming the weather-resistant resin layer (1) used in the present invention comprises a copolymer (A), a polyisocyanate compound (B), and a polyester (C). Isocyanate compound (B) is based on the total number of functional groups capable of reacting with isocyanate groups in copolymer (A) and polyester (C), depending on the performance required for weather resistant resin layer (1). It is important that the number of isocyanate groups is 0.1 to 5.0 times, preferably 0.5 to 3.0 times, more preferably 0.8 to 2 times. The ratio is such that it becomes 0 times.

The polyester (C) and polyisocyanate compound (B) may be reacted in advance to form a terminal isocyanate prepolymer. In this case, the resin composition is a composition containing the terminal isocyanate prepolymer obtained by reacting the copolymer (A) and the polyester (C) with the compound (B).

The resin composition used in the present invention has various kinds of functional groups in order to promote the crosslinking reaction between the copolymer (A) and the polyester (C) and the polyisocyanate compound (B). The crosslinking catalyst can be contained. Typical crosslinking catalysts include organometallic compounds, acids and their ammonium salts, lower amine salts, polyvalent metal salts, amines and organic peroxides.

Specific examples of organometallic compounds include sodium acetate, tin octylate, lead octylate, cobalt octylate, zinc octylate, calcium octylate, lead naphthenate, cobalt naphthenate, dibutyltin dioctate, dibutyltin dilaurate, dibutyltin Examples thereof include malate, dibutyltin di (2-ethylhexoate), diethylzinc, and tetra (n-butoxy) titanium.

Specific examples of acids include trichloroacetic acid, phosphoric acid, monoalkyl phosphoric acid, dialkyl phosphoric acid, β-hydroxyethyl (meth) acrylate phosphate ester, monoalkyl phosphorous acid, dialkyl phosphorous acid, p-toluenesulfone Examples include acid, phthalic anhydride, benzoic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, formic acid, acetic acid, propionic acid, itaconic acid, oxalic acid, and maleic acid.

Specific examples of amines include dicyclohexylamine, triethylamine, N, N-dimethylbenzylamine, N, N, N ′, N′-tetramethyl-1,3-butanediamine, diethanolamine, triethanolamine, or cyclohexylethylamine. Etc.
Organic peroxides include hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, dicumyl peroxide, diacetyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate Or t-butyl peroxylaurate.

Among these crosslinking catalysts, when the functional group involved in crosslinking of the copolymer (A) and the polyester (C) is a hydroxyl group, acids and their ammonium salts, lower amine salts, polyvalent metal salts, etc. Is preferred.
In the case of an amino group, it is preferable to use an organic peroxide, an acid anhydride, a carboxylic acid, or zinc oxide-magnesium.
In the case of a carboxyl group, it is preferable to use acids and their ammonium salts, lower amine salts, or polyvalent metal salts.
In the case of an epoxy group, it is preferable to use an organometallic compound, an amine or the like.
In the case of an N-methylol group or an N-alkoxymethyl group, it is preferable to use an acid, its ammonium salt, a lower amine salt, or a polyvalent metal salt.

Two or more kinds of these crosslinking catalysts may be used, and the total amount used is 0.01 to 10 with respect to 100 parts by weight of the total amount of the copolymer (A), the polyisocyanate compound (B) and the polyester (C). It is preferably part by weight, more preferably in the range of 0.1 to 5 parts by weight.

The resin composition for forming the weather-resistant resin layer (1) used in the present invention may contain various colorants such as pigments and dyes as long as the effects of the present invention are not hindered. May be.
As the pigment, conventionally known pigments can be used, and among them, those having high light resistance and high weather resistance are preferable. Specifically, for example, quinacridone, anthraquinone, perylene, perinone, diketopyrrolopyrrole, isoindolinone, condensed azo, benzimidazolone, monoazo, insoluble azo, naphthol, Organic pigments such as flavanthrone, anthrapyrimidine, quinophthalone, pyranthrone, pyrazolone, thioindigo, anthanthrone, dioxazine, phthalocyanine, or indanthrone, nickel dioxin yellow, copper azomethine yellow, etc. Examples include metal complexes, metal oxides such as titanium oxide, iron oxide, and zinc oxide, metal salts such as barium sulfate and calcium carbonate, inorganic pigments such as carbon black, aluminum, and mica, metal fine powder such as aluminum, and mica fine powder. It is done.

Examples of the dye include azo series, quinoline series, stilbene series, thiazole series, indigoid series, anthraquinone series, and oxazine series.
As the colorant, powder may be used as it is, or it may be used after being processed into a colored paste, a colored pellet or the like in advance.

Moreover, in order to raise the intensity | strength of the weatherable resin layer (1) obtained in a resin composition, in the range which does not prevent the effect of this invention, various heat | fever other than a copolymer (A) and polyester (C). A plastic resin may be contained.
Examples of the thermoplastic resin include polypropylene, polyethylene, ethylene-vinyl acetate copolymer, polyisobutylene, polybutadiene, polystyrene, polycarbonate, polymethylpentene, ionomer, acrylonitrile-butadiene-styrene resin, acrylic resin, polyvinyl alcohol, Examples thereof include polyamide resin, polyacetal, and polyester.

The amount of the thermoplastic resin added is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, based on 100 parts by weight of the total of the copolymer (A) and the polyester (C). If it exceeds 50 parts by weight, the compatibility with other components may decrease.

In addition, the resin composition, if necessary, within a range that does not interfere with the effect of the present invention, an ultraviolet absorber, an ultraviolet stabilizer, a radical scavenger, a filler, a thixotropy imparting agent, an anti-aging agent, an antioxidant, Antistatic agent, flame retardant, thermal conductivity improver, plasticizer, anti-sagging agent, antifouling agent, antiseptic, bactericidal agent, antifoaming agent, leveling agent, anti-blocking agent, curing agent, thickener, pigment dispersion Various additives such as an agent or a silane coupling agent may be added.

The resin composition used in the present invention is obtained by mixing a copolymer (A), a polyisocyanate compound (B), a polyester (C), and, if necessary, a colorant, a crosslinking catalyst, an additive, or a solvent. It is done.

Solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether, or diethylene glycol methyl ether,
Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone;
Ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, or diethylene glycol dimethyl ether;
Hydrocarbons such as hexane, heptane or octane,
Aromatics such as benzene, toluene, xylene, or cumene,
Among ethyl acetate or esters such as butyl acetate, an appropriate one is used according to the composition of the resin composition. Two or more solvents may be used.

Although there is no particular limitation on the mixing method, usually, the polyester (C), the polyisocyanate compound (B) and other components are mixed into the polymer solution obtained during the polymerization of the copolymer (A), What is necessary is just to stir with a shaking stirrer, a rotary stirrer, etc. Moreover, you may mix using a sand mill, 3 rolls, 2 rolls, etc. In order to improve coatability, a solvent may be further added or concentrated.

In addition, when adding a colorant, particularly a pigment, it is preferable to first prepare a pigment paste in which a colorant, a dispersion resin, and if necessary, a dispersant and a solvent are mixed, and then mix with other components.
As the dispersion resin, polyester (C) is preferably used, but is not particularly limited, and has a polar group excellent in pigment dispersibility, such as a hydroxyl group, a carboxyl group, a thiol group, an amino group, an amide group, and a ketone group. An acrylic resin, a polyurethane resin, a polyurea resin, a polyester resin, or the like can be used.
Examples of the dispersant include pigment derivatives, anionic surfactants, amphoteric surfactants, nonionic surfactants, titanium coupling agents, and silane coupling agents. In addition, the pigment surface can be modified by metal chelate, resin coating, or the like.

As a method of providing the weather resistant resin layer (1) on the water vapor barrier layer (2) or the fifth plastic film (5), a roll knife coater, a die coater, a roll coater, a bar coater, a gravure roll coater, a reverse roll coater , Dipping, blade coater, gravure coater, micro gravure coater, or comma coater, and the like, a method of coating the resin composition or a film formed from the resin composition by dry lamination, Examples of the method include pasting together with the water vapor barrier layer (2) or the fifth plastic film (5) by a conventionally known laminating method such as a roux lamination or thermal laminating method.

Next, the water vapor barrier layer (2) used in the solar cell backsheet of the present invention will be described.
As the water vapor barrier layer used in the present invention, a metal foil (21) or a vapor-deposited plastic film with a vapor deposition layer (24) can be preferably used. The plastic film (24) with a vapor deposition layer is obtained by vapor-depositing a metal oxide or a non-metal inorganic oxide (22) on the second plastic film (23).

As the metal foil (21), aluminum foil, iron foil, galvanized steel plate or the like can be used, and the thickness thereof is preferably in the range of 10 μm to 100 μm.

Examples of the plastic film (24) on which the metal oxide or the nonmetal inorganic oxide (22) is deposited include, for example, a polyester resin film such as polyethylene terephthalate or polynaphthalene terephthalate, a polyethylene resin film, a polypropylene resin film, On a second plastic film (23) such as a polyvinyl chloride resin film, a fluorine resin film, a polycarbonate resin film, a polysulfone resin film, or a poly (meth) acrylic resin film, a conventionally known vacuum deposition, Those deposited by using a PVD method such as ion plating or sputtering, or a CVD method such as plasma CVD or microwave CVD can be used.

Examples of the metal oxide or non-metal inorganic oxide (22) used for vapor deposition include oxides such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, and yttrium. Can be used. Alkali metal and alkaline earth metal fluorides can also be used, and these can be used alone or in combination.

The thickness of the vapor-deposited layer of these metal oxides or non-metallic inorganic oxides varies depending on the materials used, but is preferably 50 to 2500 mm, more preferably 300 to 1200 mm.

The vapor deposition layer of a metal oxide or a nonmetal inorganic oxide should just be provided in the at least one side of the 2nd plastic film (24), and may be provided in both surfaces. When it is provided only on one side, it is preferably provided on the surface opposite to the surface in contact with the weather resistant resin layer (1), that is, on the side in contact with the first adhesive layer (3). Furthermore, when the metal oxide or non-metal inorganic oxide (22) used for vapor deposition is used in a mixture of two or more, it can constitute a vapor deposition film in which different materials are mixed.

Furthermore, the plastic film with a vapor deposition agent layer (24) in which a metal oxide or a non-metal inorganic oxide (22) is vapor-deposited on at least one side of the second plastic film (23) can be a single vapor barrier layer (2 ), But can also be used in the form of a laminate in which two or more layers are laminated. When laminating two or more plastic films (24) with a vapor deposition agent layer, they can be bonded together by a conventionally known laminating method such as dry lamination, extrusion laminating, or thermal laminating.

Next, the first adhesive layer (3) used for the solar cell backsheet of the present invention will be described.
The first adhesive layer (3) is provided for bonding the water vapor barrier layer (2) and the first plastic film (4).
Examples of the type of adhesive used to form the first adhesive layer (3) include, for example, polyvinyl acetate adhesive, acrylic acid such as ethyl acrylate, ethyl butyl acrylate, or ethyl 2-ethylhexyl acrylate. (Meth) acrylic ester adhesives, cyanoacrylate adhesives composed of homopolymers such as acid alkyl esters, or copolymers of alkyl acrylates and methyl methacrylate, acrylonitrile, styrene, etc. Ethylene copolymer adhesive composed of a copolymer of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, methacrylic acid, polyolefin adhesive composed of polyethylene resin or polypropylene resin, cellulose Adhesives, polyester adhesives, Ether adhesive, polyamide adhesive, polyimide adhesive, urea resin or melamine resin amino resin adhesive, phenol resin adhesive, epoxy adhesive, polyester adhesive, polyurethane adhesive, A rubber adhesive made of chloroprene rubber, nitrile rubber, styrene-butadiene rubber, styrene-isoprene rubber, a silicone adhesive, or the like can be used.

In these adhesives, additives such as an ultraviolet absorber, a light stabilizer, an inorganic filler, and a colorant can be added within a range that does not affect the adhesive force.
Moreover, the said adhesive agent can form an adhesive bond layer (3) by coating with a roll coating, a gravure coat, a kiss coat, and other well-known coating methods, for example.
The coating ^{amount, 0.1g / m 2 ~ 15g /} m 2 is preferred dry film thickness.

Examples of the first plastic film (4) used in the solar cell backsheet of the present invention include polyester resin films such as polyethylene terephthalate and polynaphthalene terephthalate, polyethylene resin films, polypropylene resin films, and polyvinyl chloride. Plastic film such as plastic resin film, fluorine resin film, polycarbonate resin film, polysulfone resin film, poly (meth) acrylic resin film can be used, but polyethylene terephthalate is used in terms of weather resistance and film rigidity. A film is preferred.
Further, these films may have a single layer or a multilayer structure of two or more layers.

These first plastic films (4) may be colorless or may contain coloring components such as pigments or dyes. Examples of the method of containing the coloring component include a method of kneading the coloring component in advance at the time of film formation, a method of printing the coloring component on a colorless transparent film substrate, and the like. Further, a colored film and a colorless transparent film may be bonded together.

Hereinafter, the configuration of the solar cell backsheet of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of a solar cell backsheet of the present invention having a weather resistant resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3), and a first plastic film (4). FIG. 4 is a cross-sectional view showing an embodiment in which (1) to (4) are stacked in this order.
FIG. 2 is a solar cell backsheet of the present invention having a weatherable resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3), and a first plastic film (4). And a third plastic film (5) and a second adhesive layer (6), each layer being (1) / (5) / (6) / (2) / (3) / (4 It is typical sectional drawing which shows the aspect formed by laminating | stacking in order of ().
FIG. 3 is a solar cell backsheet of the present invention having a weatherable resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3), and a first plastic film (4). , A fourth plastic film (7) and a third adhesive layer (8), each layer being (7) / (8) / (1) / (2) / (3) / (4 It is typical sectional drawing which shows the aspect formed by laminating | stacking in order of ().
Although not shown, the solar cell backsheet of the present invention comprises a weather resistant resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3), a first plastic film (4), It can also be set as the aspect which has a 3rd plastic film (5), a 2nd adhesive bond layer (6), a 4th plastic film (7), and a 3rd adhesive bond layer (8), In that case, each layer Can be in a stacked state in the order of (7) / (8) / (1) / (5) / (6) / (2) / (3) / (4).

The third plastic film (5) in the embodiment of FIG. 2 and the fourth plastic film (7) in the embodiment of FIG. 3 are for the purpose of protecting the water vapor barrier layer when the weather resistant resin layer is thin. And it is provided as needed in order to endure the heat at the time of using it as a solar cell module.
Examples of the plastic film (5) and the plastic film (7) include polyester resin films such as polyethylene terephthalate and polynaphthalene terephthalate, polyethylene resin films, polypropylene resin films, polyvinyl chloride resin films, and polycarbonate resin films. Plastic films such as polysulfone resin films and poly (meth) acrylic resin films can be used. Among these, polyester-based resin films such as polyethylene terephthalate and polynaphthalene terephthalate, and polycarbonate-based resin films, which have resistance to temperature when used as a solar cell module, are preferable.

Further, the second adhesive layer (6) and the third adhesive layer (8) are formed using the same adhesive as that for forming the first adhesive layer (3) described above. The second adhesive layer (6) in the embodiment of FIG. 2 is used to bond the third plastic film (5) and the water vapor barrier layer (2), and in the embodiment of FIG. The third adhesive layer (8) is provided for bonding the fourth plastic film (7) and the weather resistant resin layer (1).

The solar cell backsheet of the present invention can be used as a solar cell module by combining conventionally known materials for forming a solar cell module, and the module includes a surface protection sheet, a solar cell element, and a solar cell element seal. It consists of a stop layer (10) and the solar cell backsheet of this invention.
As the surface protective sheet, glass, a plastic film, or a transparent vapor deposition film can be used as a single body or a laminate.

The solar cell element sealing layer (10) is a layer for sealing the solar cell element. Vinyl acetate-ethylene copolymer (EVA), polyvinyl butyral, silicone resin, epoxy resin, fluorinated polyimide resin, acrylic A resin mainly composed of a transparent resin such as a resin, a polyester resin, or a polyolefin-based resin can be used.
These materials may contain an ultraviolet absorber for the purpose of improving the weather resistance.

A solar cell module can be formed using the solar cell backsheet of the present invention. That is, the first plastic film (4) and the solar cell element sealing layer (10) in the solar cell backsheet are directly laminated with or without the fourth adhesive layer (9). By doing so, a solar cell module can be formed.

Examples of the fourth adhesive layer (9) include polyester resins, polyamide resins, polyurethane resins, epoxy resins, phenol resins, (meth) acrylic resins, polyvinyl acetate resins, and polyethylene aluminium. A resin composition containing a polyolefin-based resin such as polypropylene or a copolymer or modified resin thereof, a cellulose-based resin, or the like as a main component of the vehicle can be used. In the above, as a method for forming the coating agent layer, for example, a coating agent such as a solvent type, an aqueous type, or an emulsion type is used, and a coating method such as a roll coating method, a gravure roll coating method, a kiss coating method, or the like is used. It can be coated using the method.

Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention. In the examples, all parts and% indicate parts by weight and% by weight. Moreover, the weight average molecular weight of polystyrene conversion of the obtained polymer etc. was measured using the gel permeation chromatography (GPC) apparatus.

(Synthesis of weather resistant resin)
(Synthesis Examples a-1 to a-5)
In a four-necked flask equipped with a condenser, a stirrer, a thermometer, and a nitrogen inlet tube, the unsaturated dibasic acid (a1) shown in Table 1, other monomers having an ethylenically unsaturated double bond, and The solvent was charged based on the blending ratio (parts by weight) shown in Table 1, and the temperature was raised to 80 ° C. with stirring in a nitrogen atmosphere. The amount of azobisisobutyronitrile was 70% of the blending amount shown in Table 1. In addition, a polymerization reaction was carried out for 2 hours, and then azobisisobutyronitrile was added in an amount of 15% of the blending amount shown in Table 1 for a further 2 hours, and the remaining azobisisobutyronitrile was further added. And a polymerization reaction was further performed for 2 hours to obtain solutions of copolymers (a-1 to a-5). Table 1 shows the weight average molecular weight (Mw) and glass transition temperature (Tg) of each copolymer obtained.

The meanings of the abbreviations in Table 1 are as follows.
MAH: maleic anhydride HEMA: 2-hydroxyethyl methacrylate ST: styrene MMA: methyl methacrylate BMA: n-butyl methacrylate HA: hexyl acrylate HMA: hexyl methacrylate Tol: toluene BuAc: butyl acetate AIBN: azobisisobutyronitrile

(Synthesis Examples A1 to A7)
Into a four-necked flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen introduction tube, the copolymers (a-1 to a-5) prepared in the synthesis examples a-1 to a-4 and the polyester ( b) was added so that the blending amount (solid content weight) shown in Table 2 was obtained, and the temperature was raised to 80 ° C. with stirring in a nitrogen atmosphere, and triethylamine (TEA) was added based on the blending amount shown in Table 2. The mixture was heated and stirred for 6 hours to obtain a solution of copolymers (A1 to A7).
Table 2 shows the weight average molecular weight (Mw) and hydroxyl value (OHV) of the obtained copolymer (A).
The hydroxyl value (OHV) was measured as follows.
About 1 g of a sample is accurately weighed in a stoppered Erlenmeyer flask and dissolved by adding 100 mL of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixed solution. Further, exactly 5 mL of an acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to make a volume of 100 mL) was added and stirred for about 1 hour. To this, phenolphthalein reagent is added as an indicator and lasts for 30 seconds. Thereafter, the solution is titrated with a 0.1N alcoholic potassium hydroxide solution until the solution becomes light red.
The hydroxyl value was determined by the following formula. The hydroxyl value was a numerical value in the dry state of the resin (unit: mgKOH / g).
Hydroxyl value (mgKOH / g) = [{(ba) × F × 28.25} / S] / (Nonvolatile content concentration / 100) + D
However, S: Sample collection amount (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (mL)
b: Consumption of 0.1N alcoholic potassium hydroxide solution for empty experiment (mL)
F: Potency of 0.1N alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

In Table 2, the meanings of the abbreviations for polyester (b) are as follows.
P-3010: Polyester polyol (“Kuraray polyol P-3010” manufactured by Kuraray Co., Ltd., Mw = 3000)
P-510: Polyester polyol (Kuraray Co., Ltd. “Kuraray Polyol P-510”, Mw = 500)
GK870: Polyester polyol (“Byron GK870” manufactured by Toyobo Co., Ltd., Mw = 10000 to 15000)

(Preparation of solar cell backsheet)
Subsequently, the copolymers (A1 to A7), polyester (C), polyisocyanate compound (B) and additives obtained by the synthesis examples A1 to A7 were added according to the blending amounts (parts by weight) shown in Table 3. The resin composition for forming a weather resistant resin layer was obtained by blending.
A weather resistant resin layer (1) was formed on the water vapor barrier layer (2) or the plastic film (5) using the obtained resin composition. The resin composition was coated with a comma coater, dried and cured at 150 ° C. for 3 minutes, and thus a weather resistant resin layer (1) was obtained.
Next, each layer was laminated using an adhesive for dry lamination (a mixture of an adhesive main agent “AD-76P1” and a curing agent “CAT-10L” manufactured by Toyo Morton Co., Ltd.). A battery back sheet was obtained.
On the other surface of the plastic film (4), the adhesive shown in Table 4 was applied with a gravure coater and dried at 90 ° C. for 30 seconds to form a fourth adhesive layer (9).
Here, the back sheet for solar cell of the embodiment of FIG. 1 for Examples 1 to 16, the embodiment of FIG. 2 for Examples 17 to 19, and the embodiment of FIG. 3 for Examples 20 and 21 were used. Each was produced.

The meanings of the abbreviations in Table 3 are as follows.
<Regarding the polyisocyanate compound (B)>
Z4470: Isocyanurate-modified isophorone diisocyanate (“Death Module Z4470” manufactured by Sumitomo Bayer Urethane Co., Ltd.)
N3300: Isocyanurate-modified hexamethylene diisocyanate (“Sumijoule N3300” manufactured by Sumitomo Bayer Urethane Co., Ltd.)
HT: trimethylolpropane adduct-modified hexamethylene diisocyanate (“Sumijoule HT” manufactured by Sumitomo Bayer Urethane Co., Ltd.)
BL7175: Block-modified hexamethylene diisocyanate (“Death Module BL7175” manufactured by Sumitomo Bayer Urethane Co., Ltd.)
In Table 3, the equivalent ratio of isocyanate compound (B) is the ratio of the number of isocyanate groups to the total number of functional groups capable of reacting with isocyanate groups in copolymer (A) and polyester (C). To express.

<Additives>
Catalyst: Esteramine (“Desmolapi PP” manufactured by Sumitomo Bayer Urethane Co., Ltd.)
Resin 1: Acrylic polymer ("Acryt 1422TM" manufactured by Taisei Kako Co., Ltd.)
Black: Carbon pigment ("Prontex 85" manufactured by Degussa)
White: Titanium oxide pigment (Ishihara Sangyo Co., Ltd. “Taipeku CR97”)

<Regarding the weather-resistant resin layer (1)>
Fluororesin film: DuPont polyvinyl fluoride film “Tedlar” (thickness: 38 μm)

<Regarding the water vapor barrier layer (2)>
AL: Aluminum foil (thickness 30 μm)
Vapor deposition 1: A film obtained by vapor-depositing a mixture of silicon oxide and magnesium fluoride in a ratio of 90/10 to a thickness of 500 mm on one side of a polyethylene terephthalate film (thickness 12 μm).
(A weather-resistant resin layer was provided on the non-deposited surface, and an adhesive layer was provided on the vapor-deposited surface.)
Vapor deposition 2: A film in which a mixture of 90/10 of the ratio (mol%) of silicon oxide and magnesium fluoride was vapor deposited on both sides of a polyethylene terephthalate film (thickness 12 μm) to a thickness of 500 mm.
Vapor deposition 3: For two layers of polyethylene terephthalate film (thickness 12μm), two films with a mixture of silicon oxide and magnesium fluoride (mole%) 90/10 vapor deposited to a thickness of 500mm A composite film in which vapor-deposited surfaces are bonded to each other with an adhesive (a mixture of a urethane-based adhesive “AD-76P1” manufactured by Toyo Morton Co., Ltd. and an isocyanate-based curing agent “CAT-10L”).
Vapor deposition 4: Silicon oxide vapor-deposited polyethylene terephthalate film “MOS-TH” manufactured by Oike Kogyo Co., Ltd. (thickness: 12 μm)
(A weather-resistant resin layer was provided on the non-deposited surface, and an adhesive layer was provided on the vapor-deposited surface.)
Deposition 5: Alumina-deposited polyethylene terephthalate film “VMPET-1011HG” manufactured by Toyo Metallizing Co., Ltd. (thickness: 12 μm)
(A weather-resistant resin layer was provided on the non-deposited surface, and an adhesive layer was provided on the vapor-deposited surface.)

<Regarding plastic film (4)>
PET: colorless and transparent polyethylene terephthalate film (thickness: 188 μm)
White PET: White polyethylene terephthalate film (thickness: 188 μm)
Black PET: Black polyethylene terephthalate film (thickness: 188 μm)

<Regarding plastic films (5) and (7)>
PET: colorless and transparent polyethylene terephthalate film (thickness 100 μm)
PEN: colorless and transparent polyethylene naphthalate film (thickness 100 μm)

<Regarding the fourth adhesive layer (9)>
Byron 200: Toyobo's polyester resin "Byron 200"
VA9185: Toyo Ink's polyurethane resin “VA9185”

<Weather resistance evaluation>
A solar cell backsheet was tested for 3000 hours with a sunshine weather meter (120 minutes cycle, water spray 18 minutes, black panel temperature 63 ° C: JIS-K-7350 compliant). The appearance of the weather-resistant resin layer (1) of the back sheet for use was visually evaluated as follows.
○: No change compared with the initial stage Δ: Uneven gloss on the surface.
× ・ ・ ・ Appearance changes such as tearing of the sheet In addition, the decrease rate of the glossiness of the weather-resistant resin layer (1) surface after 3000 hours with a sunshine weather meter with respect to the initial value was measured using a gloss meter as follows: The street was evaluated.
○: Decreasing rate of less than 5% Δ: Decreasing rate of 5% or more and less than 10% × ... Decreasing rate of 10% or more

<Measurement of solar cell output>
Using the solar cell backsheets produced in the examples and comparative examples, one or more metal fluorides and silicon oxides selected from alkali metal fluorides and alkaline earth metal fluorides are deposited. Fluorine resin film / vinyl acetate-ethylene copolymer (EVA) / photovoltaic element / EVA / and back film for solar cell plastic film (4) are stacked and placed in a vacuum laminator and vacuumed to about 1 Torr. The solar cell module was manufactured by exhausting and heating at 140 ° C. for 30 minutes under pressure. In addition, the vapor deposition layer of the vapor-deposited fluororesin film is on the EVA side.
The obtained solar cell module was exposed to the outdoors, the solar cell output before and after the exposure was measured, and the reduction rate of the output was obtained.
○: Decreasing rate of less than 5% Δ: Decreasing rate of 5% or more and less than 10% x ... Decreasing rate of 10% or more Table 4 shows the above evaluation results.

<Evaluation of curls>
The solar cell backsheets produced in the examples and comparative examples were cut into a 30 cm square size and placed in an oven at 150 ° C. for 30 minutes, and then the degree of curling was placed on the table and the height from the table surface. Was evaluated as follows.
○: Less than 5 mm Δ: 5 mm or more and less than 10 mm x ... 10 mm or more

The solar cell backsheet according to the present invention can be used as a back protection sheet for solar cells, and a solar cell module can be produced using the solar cell backsheet.
As mentioned above, although this invention was demonstrated along the specific aspect, the deformation | transformation and improvement obvious to those skilled in the art are included in the scope of the present invention.

Claims (10)

A solar cell backsheet having a weatherable resin layer (1), a water vapor barrier layer (2), a first adhesive layer (3) and a first plastic film substrate (4),
The weather resistant resin layer (1) is
At least one unsaturated dibasic acid (a1) selected from maleic acid, maleic anhydride, fumaric acid, mesaconic acid, citraconic acid and citraconic anhydride and other monomers having an ethylenically unsaturated double bond ( a copolymer having a weight average molecular weight of 5,000 to 500,000, a functional group capable of reacting with a carboxyl group and / or an acid anhydride group, and an isocyanate group A vinyl copolymer (A) which is a graft polymer obtained by condensation and / or addition reaction with a polyester (b) having a functional group capable of reacting with a polyester and having a weight average molecular weight of 500 to 25,000 ,
Polyisocyanate compound (B) containing two or more isocyanate groups, and polyester (C) having two or more functional groups capable of reacting with isocyanate groups
A resin composition comprising:
In the vinyl copolymer (A) and the polyester (C), the number of isocyanate groups of the polyisocyanate compound (B) is 0.1 to 5.0 times the total number of functional groups capable of reacting with isocyanate groups. A back sheet for a solar cell, wherein the back sheet is formed from a resin composition. Copolymer (a)
At least one unsaturated dibasic acid (a1) selected from maleic acid, maleic anhydride, fumaric acid, mesaconic acid, citraconic acid and citraconic anhydride,
Monomer (a21) which has a functional group capable of reacting with an isocyanate group and an ethylenically unsaturated double bond, does not belong to the unsaturated dibasic acid (a1), and has an ethylenically unsaturated double bond And the monomer (a22) not belonging to any of the unsaturated dibasic acid (a1) and the monomer (a21)
The back sheet for a solar cell according to claim 1, wherein the back sheet is a copolymer comprising: Vapor deposition in which the water vapor barrier layer (2) is a metal foil (21) or a metal oxide or a non-metal inorganic oxide (22) is deposited on at least one surface of the second plastic film (23). The back sheet for a solar cell according to claim 1 or 2, wherein the back sheet is a plastic film with a layer (24). The water vapor barrier layer (2) is a two-layer plastic film (24) with a vapor deposition layer in which a metal oxide or a nonmetal inorganic oxide (22) is vapor-deposited on at least one surface of the second plastic film (23). It is a laminated body laminated | stacked above, The solar cell backsheet in any one of Claim 1 thru | or 3 characterized by the above-mentioned. The solar cell backsheet according to claim 3 or 4, wherein the vapor deposition layer constituting the plastic film with a vapor deposition layer (24) is located at a position in contact with the first adhesive layer (3). The solar cell backsheet according to any one of claims 1 to 5, wherein the first plastic film (4) is a colorless or colored polyethylene terephthalate film. The weather resistant resin layer (1), the water vapor barrier layer (2), the first adhesive layer (3), and the first plastic film (4) are sequentially laminated in the order described above. Item 7. A solar cell backsheet according to any one of Items 1 to 6. It further has a third plastic film (5) and a second adhesive layer (6), a weather resistant resin layer (1), a third plastic film (5), a second adhesive layer (6), 7. The sun according to claim 1, wherein the water vapor barrier layer (2), the first adhesive layer (3), and the first plastic film (4) are sequentially laminated in the above order. Battery backsheet. A fourth plastic film (7), a third adhesive layer (8), a fourth plastic film (7), a third adhesive layer (8), a weather resistant resin layer (1), The water vapor barrier layer (2), the first adhesive layer (3), and the first plastic film (4) are sequentially laminated in the order described above, or the fourth plastic film (7), Adhesive layer (8), weather resistant resin layer (1), third plastic film (5), second adhesive layer (6), water vapor barrier layer (2), first adhesive layer (3) The solar cell backsheet according to claim 7 or 8, wherein the first plastic film (4) is laminated in the order described above. It is a solar cell module which uses the solar cell backsheet in any one of Claims 7 thru | or 9, Comprising: The 1st plastic film (4) which comprises the said solar cell backsheet is a 4th adhesive agent. A solar cell module, wherein the solar cell module is in direct contact with or without the layer (9).

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