JP2013201416A - Back sheet for solar cell module and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back sheet which can constitute a solar cell module capable of maintaining high power generation efficiency over a long period of time, and to provide a solar cell module.SOLUTION: The back sheet for a solar cell module, which includes a water-impermeable sheet and a coating film formed on at least one surface of the water-impermeable sheet, is characterized in that: the coating film is made of a coating material containing a curable functional group-containing fluoropolymer; and a surface-treated layer is formed on at least that surface of the coating film which is on the side opposite to the water-impermeable sheet.

Description

The present invention relates to a solar cell module backsheet and a solar cell module.

A solar cell module is usually composed of a surface layer, a sealing material layer that seals solar cells, and a back sheet. As a sealing material for forming the sealing material layer, a copolymer of ethylene and vinyl acetate (hereinafter also referred to as EVA) is usually used.

The back sheet is required to have various properties such as mechanical strength, weather resistance, waterproof / moisture resistance, and electrical insulation. The structure of the normal back sheet has a multilayer structure, for example, the back layer / water-impermeable sheet / outermost side located on the solar cell sealing material side sequentially from the side in contact with the solar cell sealing material layer It consists of a weathering layer located in

In general, a resin sheet such as a polyvinyl fluoride film is used for the weather resistant layer and the back layer for reasons such as weather resistance, waterproof / moisture resistance, and excellent electrical insulation, and a water-impermeable sheet. For this, a PET film is used. In addition, when a high waterproof / moisture-proof effect is required for the back sheet, a PET film on which a metal compound such as silica is deposited or a metal layer such as aluminum foil is provided on the surface of the water-impermeable sheet. Yes.

The thickness of the back sheet is usually 20 to 500 μm in order to satisfy the required characteristics, various required characteristics such as durability and light shielding properties. However, in recent years, there has been a demand for weight reduction and thinning of the backsheet.

Therefore, it has been proposed to form a similar layer using a resin paint instead of the resin sheet. For example, use of an epoxy resin paint as a resin paint has been studied (for example, see Patent Document 1). However, epoxy resin paints are insufficient in terms of the weather resistance of the cured coating film, and have not yet been put into practical use.

Also proposed is a two-layer backsheet in which a metal substrate (water-impermeable sheet) is coated with a PVdF-based paint in which a specific amount of tetraalkoxysilane or a partial hydrolyzate thereof is blended with PVdF having no functional group. (For example, refer to Patent Document 2). Since this PVdF-based paint does not have a functional group, PVdF alone is inferior in adhesion to EVA as a sealant. Patent Document 2 attempts to improve this point by blending a specific amount of tetraalkoxysilane or its partial hydrolyzate and orienting the tetraalkoxysilane or its partial hydrolyzate at the interface with EVA.

Further, a back sheet for a solar cell module is proposed in which a cured coating film of a curable functional group-containing fluorine-containing polymer coating is formed on at least one surface of a water-impermeable sheet (see, for example, Patent Document 3). ). A curable tetrafluoroethylene (TFE) copolymer (Zeffle GK570) is disclosed as the curable functional group-containing fluorine-containing polymer. In Patent Document 3, by using the curable functional group-containing fluorine-containing polymer coating, the thickness of the back sheet can be reduced compared to the pasting of the sheet, and the film thickness is reduced while maintaining the mechanical strength. It is described that the adhesion to the water-impermeable sheet can be improved without introducing tetraalkoxysilane or the like by introducing a functional group into the fluorine-containing polymer. Yes.

Further, on one side or both sides of the base sheet, a repeating unit based on the fluoroolefin (a), a repeating unit based on the crosslinkable group-containing monomer (b), and a straight chain having 2 to 20 carbon atoms not containing a quaternary carbon atom. Cured coating film of paint containing fluorine-containing polymer (A) having repeating unit based on alkyl group-containing monomer (c) in which chain or branched alkyl group and polymerizable unsaturated group are linked by ether bond or ester bond A back sheet for a solar cell module in which a layer is formed has been proposed (for example, see Patent Document 4). In Patent Document 4, such a cured coating layer is particularly excellent in flexibility and adhesion to a base material, and is a lightweight and highly productive sun that does not cause problems of cracks, cracks, whitening, and peeling. It is described that a battery module back sheet is obtained.

JP-A-7-176775 JP 2004-214342 A International Publication No. 2007/010706 Pamphlet International Publication No. 2009/157449 Pamphlet

As described above, various solar cell module backsheets have been studied, but there is still room for study in order to achieve various required characteristics at a higher level.
For example, the conventional solar cell module has a problem that the power generation efficiency is greatly reduced when used for a long period of time. For example, a constant temperature and humidity test (one of accelerated tests described in IEC61215 which is an international standard) In the case of a dump heat test), the power generation efficiency calculated from the maximum output Pmax may be halved in a 4000 hour test that is said to correspond to 30 to 40 years in actual outdoor use. (See, for example, the 1st Stage High Reliability Solar Cell Module Development Evaluation Consortium Result Report (National Institute of Advanced Industrial Science and Technology, Photovoltaic Optical Research Center, 2011, p. 315).)

This invention is made | formed in view of the said present condition, and aims at providing the back sheet | seat which can comprise the solar cell module which can maintain high power generation efficiency over a long period of time, and a solar cell module. Is.

The present inventors have studied various types of solar cell modules excellent in power generation efficiency. As a back sheet constituting the solar cell module, the curable functional group-containing fluorine-containing polymer is provided on at least one surface of the water-impermeable sheet. When using a back sheet in which a coating film made of a coating material is formed and a surface treatment layer is formed on at least the surface of the coating film opposite to the water-impermeable sheet, a solar cell module including the back sheet It has been found that high power generation efficiency can be maintained even after long-term use. More specifically, when the surface treatment layer is in contact with the encapsulant layer in the solar cell module provided with the back sheet, the solar cell module can be found to maintain high power generation efficiency in long-term use. The inventors have conceived that the above problems can be solved brilliantly and have reached the present invention.

That is, the present invention is a back sheet of a solar cell module having a water-impermeable sheet and a coating film formed on at least one surface of the water-impermeable sheet, wherein the coating film is curable. A back sheet for a solar cell module comprising a paint containing a functional group-containing fluoropolymer, and a surface treatment layer formed on at least the surface of the coating film opposite to the water-impermeable sheet. .

The present invention is also a solar cell module including the back sheet and a sealing material layer formed on the back sheet (preferably on a surface treatment layer).
The present invention is described in detail below.

The back sheet of the solar cell module of the present invention (hereinafter, also simply referred to as the back sheet of the present invention) is a water-impermeable sheet and a coating film formed on at least one surface of the water-impermeable sheet ( Hereinafter, it is also referred to as a coating film in the present invention.

The said coating film consists of a coating material (henceforth the coating material in this invention) containing a curable functional group containing fluorine-containing polymer.
Each component of the paint of the present invention will be described.

As said curable functional group containing fluorine-containing polymer, the polymer which introduce | transduced the curable functional group into the fluorine-containing polymer is mentioned. The fluorine-containing polymer includes a resinous polymer having a clear melting point, an elastomeric polymer exhibiting rubber elasticity, and an intermediate thermoplastic elastomeric polymer.

Examples of the functional group that imparts curability to the fluorine-containing polymer include a hydroxyl group (however, the hydroxyl group contained in the carboxyl group is excluded; the same shall apply hereinafter), a carboxyl group, a group represented by —COOCO—, a cyano group, and an amino group. , A glycidyl group, a silyl group, a silanate group, an isocyanate group, and the like, which are appropriately selected according to the ease of production of the polymer and the curing system. Among these, at least one group selected from the group consisting of a hydroxyl group, a carboxyl group, a group represented by —COOCO—, a cyano group, an amino group, and a silyl group is preferable from the viewpoint of good curing reactivity. At least one group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a silyl group is more preferred, and in particular, a hydroxyl group and a carboxyl group from the viewpoint of easy availability of the polymer and good reactivity. More preferred is at least one group selected from the group consisting of These curable functional groups are usually introduced into the fluorinated polymer by copolymerizing a fluorinated monomer and a curable functional group-containing monomer.

Examples of the curable functional group-containing monomer include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an acid anhydride monomer, an amino group-containing monomer, and a silicone vinyl monomer. 1 type, or 2 or more types of these can be used.
The curable functional group-containing fluorine-containing polymer includes a polymer unit based on a fluorine-containing monomer, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an acid anhydride monomer, an amino group-containing monomer, and And a polymer unit based on at least one curable functional group-containing monomer selected from the group consisting of silicone vinyl monomers. The curable functional group-containing fluorine-containing polymer is a polymer unit based on a fluorine-containing monomer, and at least one curable functional group selected from the group consisting of a hydroxyl group-containing monomer and a carboxyl group-containing monomer. More preferably, it contains polymerized units based on group-containing monomers.

It is preferable that the polymer unit based on a curable functional group containing monomer is 1-20 mol% with respect to all the polymer units of a curable functional group containing fluorine-containing polymer. A more preferred lower limit is 2 mol%, and a more preferred upper limit is 10 mol%.

Examples of the curable functional group-containing monomer include, but are not limited to, the following. In addition, these 1 type (s) or 2 or more types can be used.

(1-1) Hydroxyl group-containing monomer:
Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2-methyl. Hydroxyl-containing vinyl ethers such as butyl vinyl ether, 5-hydroxypentyl vinyl ether and 6-hydroxyhexyl vinyl ether; hydroxyl-containing allyl ethers such as 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether and glycerol monoallyl ether . Among these, hydroxyl group-containing vinyl ethers, particularly 4-hydroxybutyl vinyl ether and 2-hydroxyethyl vinyl ether, are preferable in that they have excellent polymerization reactivity and functional group curability.

Examples of other hydroxyl group-containing monomers include hydroxyalkyl esters of (meth) acrylic acid such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.
In addition, the carboxyl group-containing monomer described later is not included in the hydroxyl group-containing monomer.

(1-2) Carboxyl group-containing monomer:
Examples of the carboxyl group-containing monomer include the general formula (1):

(Wherein R ³ , R ⁴ and R ⁵ are the same or different, and each is a hydrogen atom, an alkyl group, an aryl group, a carboxyl group or an alkoxycarbonyl group; n is 0 or 1) Unsaturated carboxylic acids such as carboxylic acids, unsaturated dicarboxylic acids, monoesters thereof; or general formula (2):

(Wherein R ⁶ and R ⁷ are the same or different and both are saturated or unsaturated linear or cyclic alkyl groups; n is 0 or 1; m is 0 or 1) And monomers.

Specific examples of the unsaturated carboxylic acids represented by the general formula (1) include, for example, acrylic acid, methacrylic acid, vinyl acetic acid, crotonic acid, cinnamic acid, itaconic acid, itaconic acid monoester, maleic acid, and maleic acid monoester. Examples include esters, fumaric acid, and fumaric acid monoesters. Among them, crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid, and fumaric acid monoester having low homopolymerization are preferable because homopolymers are low and it is difficult to form a homopolymer.

Specific examples of the carboxyl group-containing vinyl ether monomer represented by the general formula (2) include, for example, 3-allyloxypropionic acid, 3- (2-allyloxyethoxycarbonyl) propionic acid, 3- (2-ary One type or two or more types such as roxybutoxycarbonyl) propionic acid, 3- (2-vinyloxyethoxycarbonyl) propionic acid, 3- (2-vinyloxybutoxycarbonyl) propionic acid and the like can be mentioned. Among these, 3- (2-allyloxyethoxycarbonyl) propionic acid and the like are advantageous and preferable in terms of good monomer stability and polymerization reactivity.

As the carboxyl group-containing monomer, in addition to those represented by the general formula (1) or (2), for example, alkenyl esters of polybasic carboxylic acids such as vinyl phthalate and vinyl pyromellitic acid Can be used.

(1-3) Acid anhydride monomer:
Examples of the acid anhydride monomer include unsaturated dicarboxylic acid anhydrides such as maleic acid anhydride.

(1-4) Amino group-containing monomer:
Examples of the amino group-containing monomer include amino vinyl ethers represented by CH ₂ ═CH—O— (CH ₂ ) _x —NH ₂ (x = 0 to 10); CH ₂ ═CH—O—CO (CH ₂ ) amines represented by _{x -NH 2 (x = 1~10)} ; other aminomethylstyrene, vinylamine, acrylamide, vinylacetamide, vinylformamide or the like.

(1-5) Silicone vinyl monomer:
Examples of the silicone-based vinyl monomer include CH ₂ ═CHCO ₂ (CH ₂ ) ₃ Si (OCH ₃ ) ₃ , CH ₂ ═CHCO ₂ (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ , and CH ₂ ═C. _{(CH 3) CO 2 (CH} 2) 3 Si (OCH 3) 3, CH 2 = C (CH 3) CO 2 (CH 2) 3 Si (OC 2 H 5) 3, CH 2 = CHCO 2 (CH 2 _{) 3 SiCH 3 (OC 2 H} 5) 2, CH 2 = C (CH 3) CO 2 (CH 2) 3 SiC 2 H 5 (OCH 3) 2, CH 2 = C (CH 3) CO 2 (CH 2 ) ₃ Si (CH ₃ ) ₂ (OC ₂ H ₅ ), CH ₂ ═C (CH ₃ ) CO ₂ (CH ₂ ) ₃ Si (CH ₃ ) ₂ OH, CH ₂ ═CH (CH ₂ ) ₃ Si (OCOCH) _{3) 3, CH 2 = C} (C _{3) CO 2 (CH 2)} 3 SiC 2 H 5 (OCOCH 3) 2, CH 2 = C (CH 3) CO 2 (CH 2) 3 SiCH 3 (N (CH 3) COCH 3) 2, CH 2 = _{CHCO 2 (CH 2) 3 SiCH} 3 _{[ON (CH 3) C 2 H} 5 ] _{2, CH 2 = C (CH} 3) CO 2 (CH 2) 3 SiC 6 H 5 _[ON (CH _{3) C} 2 H _{5] 2,} etc. (meth) acrylic acid _{esters; CH 2 = CHSi [ON =} C (CH 3) (C 2 H 5)] 3, CH 2 = CHSi (OCH 3) 3, CH 2 = CHSi (OC ₂ H ₅ ) ₃ , CH ₂ = CHSiCH ₃ (OCH ₃ ) ₂ , CH ₂ = CHSi (OCOCH ₃ ) ₃ , CH ₂ = CHSi (CH ₃ ) ₂ (OC ₂ H ₅ ), CH ₂ = CHSi (CH ₃ ) _{2 iCH 3 (OCH 3) 2,} CH 2 = CHSiC 2 H 5 (OCOCH 3) 2, CH 2 = CHSiCH 3 _{[ON (CH 3) C 2 H} 5 ] _2, vinyl trichlorosilane or their partial hydrolysates And vinyl silanes such as trimethoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, trimethoxysilylbutyl vinyl ether, methyldimethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, and triethoxysilylpropyl vinyl ether.

As the fluorine-containing monomer, that is, a monomer for forming a fluorine-containing polymer into which a curable functional group is introduced, for example, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and , Fluorovinyl ether can be mentioned, and one or more of these can be used.
Among these, at least one selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride is preferable, and at least one selected from the group consisting of tetrafluoroethylene and chlorotrifluoroethylene It is more preferable that

Examples of the fluorine-containing polymer into which the curable functional group is introduced may include the following, depending on the polymer units constituting the polymer.

(1) Perfluoroolefin polymer mainly composed of perfluoroolefin units:
Specific examples include a homopolymer of tetrafluoroethylene (TFE), a copolymer of TFE and hexafluoropropylene (HFP), perfluoro (alkyl vinyl ether) (PAVE), and the like, and further copolymerizable therewith. And copolymers with other monomers.

Examples of the other copolymerizable monomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, cyclohexyl carboxyl. Carboxylic acid vinyl esters such as vinyl acid vinyl, vinyl benzoate, para-t-butyl vinyl benzoate; alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether; ethylene, propylene, n-butene, isobutene, etc. Non-fluorinated olefins; fluorinated monomers such as vinylidene fluoride (VdF), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), fluorovinyl ether, etc. The present invention is not limited only to.

Among these, TFE-based polymers mainly composed of TFE are preferable in terms of excellent pigment dispersibility, weather resistance, copolymerization, and chemical resistance.

Specific examples of the curable functional group-containing perfluoroolefin-based polymer include, for example, a copolymer of TFE / isobutylene / hydroxybutyl vinyl ether / other monomers, TFE / vinyl versatate / hydroxybutyl vinyl ether / other monomers. Copolymer, TFE / VdF / hydroxybutyl vinyl ether / other monomer copolymer, etc., especially TFE / isobutylene / hydroxybutyl vinyl ether / other monomer copolymer, TFE / versaic acid Vinyl / hydroxybutyl vinyl ether / copolymers of other monomers are preferred.

Examples of the TFE-based curable polymer composition for paint include Zeffle GK series manufactured by Daikin Industries, Ltd.

(2) CTFE polymer mainly composed of chlorotrifluoroethylene (CTFE) unit:
Specific examples include a copolymer of CTFE / hydroxybutyl vinyl ether / other monomers.

Examples of the CTFE-based curable polymer composition for paint include Lumiflon manufactured by Asahi Glass Co., Ltd., Fluoronate manufactured by DIC Co., Ltd., Cefral Coat manufactured by Central Glass Co., Ltd., and ZAFLON manufactured by Toa Gosei Co., Ltd. it can.

(3) VdF polymers mainly composed of vinylidene fluoride (VdF) units:
Specific examples include VdF / TFE / hydroxybutyl vinyl ether / a copolymer of other monomers.

(4) Fluoroalkyl group-containing polymer mainly composed of fluoroalkyl units:
Specific examples include CF ₃ CF ₂ (CF ₂ CF ₂ ) _n CH ₂ CH ₂ OCOCH═CH ₂ (mixture of n = 3 and 4) / 2-hydroxyethyl methacrylate / stearyl acrylate copolymer. .

Examples of the fluoroalkyl group-containing polymer include Unidyne and Ftone manufactured by Daikin Industries, Ltd., and Zonyl manufactured by DuPont.

Among these, in consideration of weather resistance and moisture resistance, perfluoroolefin-based polymers are preferable.

The said curable functional group containing fluorine-containing polymer can be manufactured by the method disclosed by Unexamined-Japanese-Patent No. 2004-204205, for example.

It is preferable that content of the said curable functional group containing fluorine-containing polymer in the coating material in this invention is 20-100 mass% with respect to 100 mass% of total amounts of the non volatile matter in a coating material.

The paint in the present invention preferably contains a curing agent.
The said hardening | curing agent is selected according to the functional group of a curable polymer, For example, with respect to a hydroxyl-containing fluorine-containing polymer, an isocyanate type hardening | curing agent, a melamine resin, a silicate compound, an isocyanate group containing silane compound etc. can illustrate preferably. In addition, amino-based curing agents and epoxy-based curing agents are used for carboxyl group-containing fluorine-containing polymers, and carbonyl-group-containing curing agents, epoxy-based curing agents, acid anhydride-based curing agents are used for amino group-containing fluorine-containing polymers. Is usually adopted.

As the curing agent, among them, a polyisocyanate compound derived from at least one isocyanate selected from the group consisting of xylylene diisocyanate (XDI) and bis (isocyanate methyl) cyclohexane (hydrogenated XDI, H6XDI), hexamethylene At least one compound selected from the group consisting of blocked isocyanate compounds based on diisocyanate (HDI), polyisocyanate compounds derived from hexamethylene diisocyanate (HDI), and polyisocyanate compounds derived from isophorone diisocyanate (IPDI) Is preferred.

The curing agent is derived from at least one isocyanate selected from the group consisting of xylylene diisocyanate (XDI) and bis (isocyanatomethyl) cyclohexane (hydrogenated XDI, H6XDI) (hereinafter also referred to as isocyanate (i)). By using a polyisocyanate compound (hereinafter also referred to as polyisocyanate compound (I)), the cured coating film obtained from the coating material according to the present invention has excellent adhesion to the sealing material of the solar cell module. Become. Furthermore, the back sheet of the solar cell module having the cured coating film has excellent blocking resistance to the surface with which the cured coating film comes into contact in a winding process or the like.
Examples of the polyisocyanate compound (I) include an adduct obtained by addition polymerization of the isocyanate (i) and a trihydric or higher aliphatic polyhydric alcohol, and an isocyanurate structure (nurate) comprising the isocyanate (i). And a biuret composed of the above-mentioned isocyanate (i).

As the adduct, for example, the following general formula (3):

(In the formula, R ¹ represents an aliphatic hydrocarbon group having 3 to 20 carbon atoms. R ² represents a phenylene group or a cyclohexylene group. K is an integer of 3 to 20). Those having the following structure are preferred.
R ¹ in the general formula (3) is a hydrocarbon group based on the trivalent or higher aliphatic polyhydric alcohol, more preferably an aliphatic hydrocarbon group having 3 to 10 carbon atoms, and 3 to 6 carbon atoms. The aliphatic hydrocarbon group is more preferable.
When R ² is a phenylene group, 1,2-phenylene group (o-phenylene group), 1,3-phenylene group (m-phenylene group), and 1,4-phenylene group (p-phenylene group) Any of these may be used. Of these, a 1,3-phenylene group (m-phenylene group) is preferable. It is also possible all R ² in the general formula (3) is the same phenylene group, or two or more may be mixed.
When R ² is a cyclohexylene group, it may be any of 1,2-cyclohexylene group, 1,3-cyclohexylene group, and 1,4-cyclohexylene group. Of these, a 1,3-cyclohexylene group is preferable. It is also possible all R ² in the general formula (3) is the same cyclohexylene group, or two or more may be mixed.
The k is a number corresponding to the valence of a trihydric or higher aliphatic polyhydric alcohol. As said k, More preferably, it is an integer of 3-10, More preferably, it is an integer of 3-6.

The isocyanurate structure has the following general formula (4) in the molecule:

It has 1 or 2 or more isocyanurate rings.
Examples of the isocyanurate structure include a trimer obtained by the trimerization reaction of the isocyanate, a pentamer obtained by the pentamerization reaction, and a heptamer obtained by the heptamization reaction.
Among them, the following general formula (5):

(Wherein, R ² has the general formula (3) is the same as R ² in.) Trimer is preferably represented by. That is, the isocyanurate structure is preferably a trimer of at least one isocyanate selected from the group consisting of xylylene diisocyanate and bis (isocyanatomethyl) cyclohexane.

The biuret is represented by the following general formula (6):

(Wherein, R ² has the general formula (3) is the same as R ² in.) Is a compound having a structure represented by, under different conditions than the case of obtaining the isocyanurate structure, the It can be obtained by trimerizing isocyanate.

The polyisocyanate compound (I) includes, among others, at least one isocyanate selected from the group consisting of the above adducts, that is, xylylene diisocyanate and bis (isocyanatomethyl) cyclohexane, and a trihydric or higher aliphatic polyhydric alcohol. Are preferably obtained by addition polymerization.

When the polyisocyanate compound (I) is an adduct of the isocyanate (i) and a trihydric or higher aliphatic polyhydric alcohol, the trihydric or higher aliphatic polyhydric alcohol is specifically glycerol. , Trimethylolpropane (TMP), 1,2,6-hexanetriol, trimethylolethane, 2,4-dihydroxy-3-hydroxymethylpentane, 1,1,1-tris (bishydroxymethyl) propane, 2,2 -Trihydric alcohols such as bis (hydroxymethyl) butanol-3; tetrahydric alcohols such as pentaerythritol and diglycerol; pentahydric alcohols such as arabit, ribitol, and xylitol (pentit); Such as hexahydric alcohol (hexit) That. Of these, trimethylolpropane and pentaerythritol are particularly preferable.

Moreover, as xylylene diisocyanate (XDI) used as a component of the adduct, 1,3-xylylene diisocyanate (m-xylylene diisocyanate), 1,2-xylylene diisocyanate (o-xylylene diisocyanate), 1 1,4-xylylene diisocyanate (p-xylylene diisocyanate), among which 1,3-xylylene diisocyanate (m-xylylene diisocyanate) is preferable.

The bis (isocyanatemethyl) cyclohexane (hydrogenated XDI, H6XDI) used as a component of the adduct is 1,3-bis (isocyanatemethyl) cyclohexane, 1,2-bis (isocyanatemethyl) cyclohexane, 1, 4-bis (isocyanatomethyl) cyclohexane can be mentioned, among which 1,3-bis (isocyanatemethyl) cyclohexane is preferred.

Suitable in the present invention by addition polymerization of at least one isocyanate selected from the group consisting of xylylene diisocyanate and bis (isocyanatomethyl) cyclohexane and an aliphatic polyhydric alcohol having 3 or more valences as described above. Adducts used in the above are obtained.

As an adduct preferably used in the present invention, specifically, for example, the following general formula (7):

(Wherein R ⁸ represents a phenylene group or a cyclohexylene group), that is, at least one isocyanate selected from the group consisting of xylylene diisocyanate and bis (isocyanatomethyl) cyclohexane; Mention may be made of polyisocyanate compounds obtained by addition polymerization of methylolpropane (TMP).
The phenylene group or cyclohexylene group represented by R ⁸ in the general formula (7) is as described for R ² in the general formula (3).

Commercially available products of the polyisocyanate compound represented by the general formula (7) include Takenate D110N (manufactured by Mitsui Chemicals, XDI and TMP adduct, NCO content 11.8%), Takenate D120N (Mitsui Chemicals) The product made from a company, the adduct of H6XDI and TMP, NCO content 11.0%), etc. are mentioned.

Specific examples of the polyisocyanate compound (I) having an isocyanurate structure include Takenate D121N (Mitsui Chemicals, H6XDI Nurate, NCO content 14.0%), Takenate D127N (Mitsui Chemicals, Inc.) H6XDI nurate, H6XDI trimer, NCO content 13.5%) and the like.

By using a blocked isocyanate based on hexamethylene diisocyanate (HDI) (hereinafter also simply referred to as a blocked isocyanate) as a curing agent, the coating material in the present invention has a sufficient pot life (pot life).
As the blocked isocyanate, those obtained by reacting a polyisocyanate compound derived from hexamethylene diisocyanate (hereinafter also referred to as polyisocyanate compound (II)) with a blocking agent are preferable.
As the polyisocyanate compound (II), for example, an adduct obtained by addition polymerization of hexamethylene diisocyanate and a trihydric or higher aliphatic polyhydric alcohol, an isocyanurate structure (nurate structure) composed of hexamethylene diisocyanate, And biuret which consists of hexamethylene diisocyanate can be mentioned.

Examples of the adduct include the following general formula (8):

(Wherein R ⁹ represents an aliphatic hydrocarbon group having 3 to 20 carbon atoms. K is an integer of 3 to 20).
R ⁹ in the general formula (8) is a hydrocarbon group based on the above trivalent or higher aliphatic polyhydric alcohol, more preferably an aliphatic hydrocarbon group having 3 to 10 carbon atoms, and 3 to 6 carbon atoms. The aliphatic hydrocarbon group is more preferable.
The k is a number corresponding to the valence of a trihydric or higher aliphatic polyhydric alcohol. As said k, More preferably, it is an integer of 3-10, More preferably, it is an integer of 3-6.

The isocyanurate structure has the following general formula (4) in the molecule:

It has 1 or 2 or more isocyanurate rings.
Examples of the isocyanurate structure include a trimer obtained by the trimerization reaction of the isocyanate, a pentamer obtained by the pentamerization reaction, and a heptamer obtained by the heptamization reaction.
Among them, the following general formula (9):

The trimer represented by these is preferable.

The biuret is represented by the following general formula (10):

And can be obtained by trimerizing hexamethylene diisocyanate under conditions different from those for obtaining the isocyanurate structure.

As the blocking agent, a compound having active hydrogen is preferably used. As the compound having active hydrogen, for example, at least one selected from the group consisting of alcohols, oximes, lactams, active methylene compounds, and pyrazole compounds is preferably used.

Thus, the blocked isocyanate is obtained by reacting a polyisocyanate compound derived from hexamethylene diisocyanate with a blocking agent, and the blocking agent includes alcohols, oximes, lactams, and active methylene compounds. And at least one selected from the group consisting of pyrazole compounds is one of the preferred embodiments of the present invention.

When the polyisocyanate compound (II) for obtaining the blocked isocyanate is an adduct of hexamethylene diisocyanate and a trihydric or higher aliphatic polyhydric alcohol, the trihydric or higher aliphatic polyhydric alcohol is specifically Glycerol, trimethylolpropane (TMP), 1,2,6-hexanetriol, trimethylolethane, 2,4-dihydroxy-3-hydroxymethylpentane, 1,1,1-tris (bishydroxymethyl) propane , Trihydric alcohols such as 2,2-bis (hydroxymethyl) butanol-3; tetrahydric alcohols such as pentaerythritol and diglycerol; pentahydric alcohols such as arabit, ribitol and xylitol (pentit); Lactitol, allozulcit It includes hexavalent alcohols (hexites) or the like is. Of these, trimethylolpropane and pentaerythritol are particularly preferable.
The adduct is obtained by addition polymerization of hexamethylene diisocyanate and the above trivalent or higher aliphatic polyhydric alcohol.

Specific examples of the compound having active hydrogen to be reacted with the polyisocyanate compound (II) include alcohols such as methanol, ethanol, n-propanol, isopropanol, and methoxypropanol; acetone oxime, 2-butanone oxime, and cyclohexanone. Oximes such as oximes; lactams such as ε-caprolactam; active methylene compounds such as methyl acetoacetate and ethyl malonate; pyrazole compounds such as 3-methylpyrazole, 3,5-dimethylpyrazole, and 3,5-diethylpyrazole And one or more of these can be used.
Among these, active methylene compounds and oximes are preferable, and active methylene compounds are more preferable.

Commercially available products of the above-mentioned blocked isocyanate include Duranate K6000 (manufactured by Asahi Kasei Chemicals Corporation, HDI active methylene compound block isocyanate), Duranate TPA-B80E (manufactured by Asahi Kasei Chemicals Corporation), Duranate MF-B60X (manufactured by Asahi Kasei Chemicals Corporation). , Duranate 17B-60PX (Asahi Kasei Chemicals Corporation), Coronate 2507 (Nippon Polyurethane Co., Ltd.), Coronate 2513 (Nippon Polyurethane Co., Ltd.), Coronate 2515 (Nippon Polyurethane Co., Ltd.), Sumijour BL-3175 (Sumi) Chemical Chemicals, Bayer Urethane Co., Ltd.), Luxate HC1170 (manufactured by Olin Chemicals), Luxate HC2170 (manufactured by Olin Chemicals), and the like.

As the curing agent, a polyisocyanate compound derived from hexamethylene diisocyanate (HDI) (hereinafter also referred to as polyisocyanate compound (III)) can be used. As polyisocyanate compound (III), what was mentioned above as polyisocyanate compound (II) is mentioned. Among these, an isocyanurate structure composed of hexamethylene diisocyanate is preferable.

Specific examples of the polyisocyanate compound (III) include Coronate HX (manufactured by Nippon Polyurethane Co., Ltd., isocyanurate structure of hexamethylene diisocyanate, NCO content 21.1%), Sumijour N3300 (manufactured by Sumika Bayer, Hexamethylene diisocyanate isocyanurate structure), Takenate D170N (Mitsui Chemicals, hexamethylene diisocyanate isocyanurate structure), and the like.

By using a polyisocyanate compound derived from isophorone diisocyanate (IPDI) as a curing agent (hereinafter also referred to as polyisocyanate compound (IV)), a solar cell module having a cured coating film obtained from the paint according to the present invention. The back sheet has excellent blocking resistance to the surface with which the cured coating film comes into contact in the winding process or the like.

Examples of the polyisocyanate compound (IV) include an adduct obtained by addition polymerization of isophorone diisocyanate and a trihydric or higher aliphatic polyhydric alcohol, an isocyanurate structure (nurate structure) composed of isophorone diisocyanate, and Biuret made of isophorone diisocyanate can be mentioned.

Examples of the adduct include the following general formula (11):

(In the formula, R ¹⁰ represents an aliphatic hydrocarbon group having 3 to 20 carbon atoms. R ¹¹ represents the following general formula (12):

It is group represented by these. k is an integer of 3-20. ) Is preferred.
R ¹⁰ in the general formula (11) is a hydrocarbon group based on the above trivalent or higher aliphatic polyhydric alcohol, more preferably an aliphatic hydrocarbon group having 3 to 10 carbon atoms, and 3 to 6 carbon atoms. The aliphatic hydrocarbon group is more preferable.
The k is a number corresponding to the valence of a trihydric or higher aliphatic polyhydric alcohol. As said k, More preferably, it is an integer of 3-10, More preferably, it is an integer of 3-6.

The isocyanurate structure has the following general formula (4) in the molecule:

It has 1 or 2 or more isocyanurate rings.
Examples of the isocyanurate structure include a trimer obtained by a trimerization reaction of isophorone diisocyanate, a pentamer obtained by a pentamerization reaction, a heptamer obtained by a heptamerization reaction, and the like.
Among them, the following general formula (13):

(Wherein R ¹¹ is the same as R ¹¹ in the general formula (11)). That is, the isocyanurate structure is preferably a trimer of isophorone diisocyanate.

The biuret is represented by the following general formula (14):

(Wherein, R ¹¹ has the general formula (11) in the same as R ¹¹ in.) Is a compound having a structure represented by, under different conditions than the case of obtaining the isocyanurate structure, isophorone It can be obtained by trimerizing diisocyanate.

Above all, the polyisocyanate compound (IV) is preferably at least one selected from the group consisting of the adduct and the isocyanurate structure. That is, the polyisocyanate compound (IV) is selected from the group consisting of an adduct obtained by addition polymerization of isophorone diisocyanate and a trihydric or higher aliphatic polyhydric alcohol, and an isocyanurate structure composed of isophorone diisocyanate. It is preferable that it is at least one kind.

When the polyisocyanate compound (IV) is an adduct of isophorone diisocyanate and a trihydric or higher aliphatic polyhydric alcohol, specific examples of the trihydric or higher aliphatic polyhydric alcohol include glycerol and trimethylol. Propane (TMP), 1,2,6-hexanetriol, trimethylolethane, 2,4-dihydroxy-3-hydroxymethylpentane, 1,1,1-tris (bishydroxymethyl) propane, 2,2-bis ( Trivalent alcohols such as hydroxymethyl) butanol-3; tetravalent alcohols such as pentaerythritol and diglycerol; pentavalent alcohols such as arabit, ribitol and xylitol (pentit); hexavalents such as sorbit, mannitol, galactitol and allozulcit Alcohol (hexit) etc. It is. Of these, trimethylolpropane and pentaerythritol are particularly preferable.

Adducts suitably used in the present invention can be obtained by addition polymerization of isophorone diisocyanate and a trihydric or higher aliphatic polyhydric alcohol as described above.

As an adduct preferably used in the present invention, specifically, for example, the following general formula (15):

(In the formula, R ¹² represents the following general formula (12):

It is group represented by these. ), That is, a polyisocyanate compound obtained by addition polymerization of isophorone diisocyanate and trimethylolpropane (TMP).

As a commercial item of the polyisocyanate compound (TMP adduct of isophorone diisocyanate) represented by the general formula (12), Takenate D140N (manufactured by Mitsui Chemicals, Inc., NCO content 11%) and the like can be mentioned.

Examples of commercially available isocyanurate structures made of isophorone diisocyanate include Desmodur Z4470 (manufactured by Sumika Bayer Urethane Co., Ltd., NCO content 11%).

Examples of the curing agent include polyisocyanate compounds derived from at least one isocyanate selected from the group consisting of xylylene diisocyanate (XDI) and bis (isocyanate methyl) cyclohexane (hydrogenated XDI, H6XDI), hexamethylene diisocyanate ( More preferred are at least one compound selected from the group consisting of blocked isocyanate compounds based on HDI) and polyisocyanate compounds derived from isophorone diisocyanate (IPDI).

When the paint in the present invention contains a polyisocyanate compound (I) derived from at least one isocyanate (i) selected from the group consisting of xylylene diisocyanate and bis (isocyanatomethyl) cyclohexane, the paint is obtained from the paint. Since the coating film has excellent adhesion to EVA, which is a general sealing material for solar cell modules, and also has excellent blocking resistance during winding, the sun is generally manufactured through a winding process. Suitable for battery module backsheet coating.
As will be described later, in the back sheet of the solar cell module, the coating film is formed on one side or both sides of the water-impermeable sheet.
When the coating film obtained from the coating material in the present invention is formed on one side of the water-impermeable sheet and the other surface of the water-impermeable sheet is a non-coating surface, the coating film is wound up. In this case, it comes into contact with the non-painted surface of the water-impermeable sheet. On the other hand, the above-mentioned coating film is formed on one side of a water-impermeable sheet, and the other side of the water-impermeable sheet is a coating film made of another coating material (a fluoropolymer coating material having no curable functional group described later) In the winding process, the coating film obtained from the coating material on the water-impermeable sheet is provided on the water-impermeable sheet. It comes into contact with a coating film or other sheet made of other paint. Moreover, when the coating film obtained from the coating material in the present invention is formed on both surfaces of the water-impermeable sheet, the coating film is formed on the other surface of the water-impermeable sheet in the winding process. Will come in contact with the same type of coating.
When the coating material in this invention contains polyisocyanate compound (I), the coating film obtained from this coating material can exhibit the blocking resistance outstanding with respect to the surface to contact in any of these cases.

When the coating material in this invention contains the polyisocyanate compound (IV) derived from isophorone diisocyanate (IPDI), the coating film obtained from this coating material is excellent in blocking resistance at the time of winding. Even when the coating film is formed on one side or both sides of the water-impermeable sheet, the coating film can exhibit excellent blocking resistance with respect to the contacting surface as described above.

When the paint in the present invention contains a blocked isocyanate based on hexamethylene diisocyanate (HDI), the paint has a significantly improved pot life compared to a conventional curable functional group-containing fluorine-containing polymer paint. The pot life indicating the usable time of the paint is one of important indexes from the viewpoint of increasing the degree of freedom of the process. If the pot life of the paint is long, it can be applied to applications that require a relatively long time for application. Also, if it is necessary to temporarily store or transfer the paint after it is prepared, The fluidity of the paint can be secured. Such a coating material is extremely useful for coating a back sheet of a solar cell module, for which a curable functional group-containing fluorine-containing polymer coating material has been suitably used.

The curing agent includes a polyisocyanate compound derived from at least one isocyanate selected from the group consisting of xylylene diisocyanate (XDI) and bis (isocyanate methyl) cyclohexane (hydrogenated XDI, H6XDI), and hexamethylene. Particularly preferred is at least one compound selected from the group consisting of blocked isocyanate compounds based on diisocyanate (HDI).

The content of the curing agent in the coating is preferably 0.1 to 5 equivalents relative to 1 equivalent of the curable functional group in the curable functional group-containing fluoropolymer, and is 0.5 to 1.5 equivalents. More preferably.

The content of the curable functional group in the curable functional group-containing fluorine-containing polymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis depending on the type of monomer.

The paint in the present invention can be prepared in a conventional manner in the form of a solvent-type paint, a water-type paint, a powder-type paint, and the like. Among these, the form of a solvent-type paint is preferable from the viewpoint of easiness of film formation, curability and good drying properties.

The solvent in the solvent-type paint is preferably an organic solvent, and esters such as ethyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, cellosolve acetate, and propylene glycol methyl ether acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone Cyclic ethers such as tetrahydrofuran and dioxane; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; aromatic hydrocarbons such as xylene, toluene and solvent naphtha; propylene glycol methyl ether and ethyl cellosolve Glycol ethers such as diethylene glycol esters such as carbitol acetate; n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, - undecane, n- dodecane, aliphatic hydrocarbons such as mineral spirit; a mixed solvent, and the like.
Of these, esters are preferable, and butyl acetate is particularly preferable.

When the paint in the present invention is a solvent-type paint, the concentration of the curable functional group-containing fluorine-containing polymer with respect to the total amount of the paint of 100% by mass is preferably 5 to 95% by weight, and preferably 10 to 70% by weight. More preferred.

Various additives can be further blended in the paint according to the present invention in accordance with required characteristics. Examples of the additive include a curing accelerator, a pigment, a pigment dispersant, an antifoaming agent, a leveling agent, an ultraviolet absorber, a light stabilizer, a thickener, an adhesion improver, and a matting agent.

Examples of the curing accelerator include organic tin compounds, acidic phosphate esters, reaction products of acidic phosphate esters and amines, saturated or unsaturated polycarboxylic acids or acid anhydrides thereof, organic titanate compounds, amine compounds, Examples include lead octylate.

1 type may be used for a hardening accelerator and it may use 2 or more types together. The blending ratio of the curing accelerator is preferably about 1.0 × 10 ^{−6 to} 1.0 × 10 ⁻² parts by weight, preferably 5.0 × 10 ⁻⁵ to 100 parts by weight of the curable functional group-containing fluoropolymer. About 1.0 × 10 ⁻³ parts by weight is more preferable.

The paint in the present invention preferably further contains a pigment. Thereby, the cured coating film obtained becomes excellent in UV shielding property. In addition, it is strongly desired to add a pigment from the viewpoint of making the appearance of the solar cell module beautiful.
Specific examples of pigments include inorganic pigments such as white pigments such as titanium oxide and calcium carbonate, black pigments such as carbon black, and Cu—Cr—Mn alloys, and other complex metals; phthalocyanines, quinacridones, azos, etc. However, it is not limited to these.

The addition amount of the pigment is preferably 0.1 to 200 parts by weight, and more preferably 0.1 to 160 parts by weight with respect to 100 parts by weight of the curable functional group-containing fluorine-containing polymer.

The coating material in the present invention preferably further contains an ultraviolet absorber. Since solar cells are used outdoors for a long time with strong ultraviolet rays, countermeasures against deterioration of the backsheet due to ultraviolet rays are required. If an ultraviolet absorber is added to the coating material in the present invention, a function of absorbing ultraviolet rays can be imparted to the cured coating layer.
As the ultraviolet absorber, both organic and inorganic ultraviolet absorbers can be used. Examples of the organic compound type include UV absorbers such as salicylic acid ester type, benzotriazole type, benzophenone type, and cyanoacrylate type, and inorganic type filler type inorganic UV absorbers such as zinc oxide and cerium oxide are preferable. .

An ultraviolet absorber may be used individually by 1 type, and may be used in combination of 2 or more type. The amount of the ultraviolet absorber is preferably 0.1 to 15% by mass with respect to 100% by mass of the total amount of the curable functional group-containing fluoropolymer in the paint. When the amount of the ultraviolet absorber is too small, the effect of improving the light resistance cannot be sufficiently obtained, and when the amount is too large, the effect is saturated.

The coating film in this invention can be formed by apply | coating this coating material to a water-impermeable sheet, and hardening | curing. The cured coating film is formed on the water-impermeable sheet by coating the water-impermeable sheet with the paint according to the present invention in accordance with the form of the paint.

The coating may be performed within a temperature range of normal conditions in the coating form, and curing and drying are performed at 10 to 300 ° C., usually 100 to 200 ° C. for 30 seconds to 3 days in the case of a solvent-type paint. Therefore, as the water-impermeable sheet constituting the back sheet of the solar cell module of the present invention, a material such as a Si-deposited PET sheet that is desired to avoid high-temperature treatment can be used without any problem. After curing and drying, curing may be performed, and curing is usually completed at 20 to 300 ° C. for 1 minute to 3 days.

The coating on the water-impermeable sheet may be performed by directly applying the paint according to the present invention to the water-impermeable sheet, or by applying it through a primer layer or the like.

The primer layer is formed by a conventional method using a conventionally known primer coating. Typical examples of the primer coating include epoxy resin, urethane resin, acrylic resin, silicone resin, polyester resin, and the like.

The coating film in the present invention preferably has a degree of cross-linking calculated as a gel fraction from Soxhlet extraction with acetone is 90 to 100%, more preferably 95 to 100%, and 98 to 100%. Is more preferable.

The film thickness of the cured coating film is preferably 5 μm or more from the viewpoint of good concealability, weather resistance, chemical resistance, and moisture resistance. More preferably, it is 7 micrometers or more, More preferably, it is 10 micrometers or more. The upper limit is preferably about 1000 μm, and more preferably 100 μm because if the thickness is too thick, the effect of reducing the weight cannot be obtained. The film thickness is particularly preferably 10 to 40 μm.

A surface treatment layer is formed on at least the surface opposite to the water-impermeable sheet of the coating film in the present invention.

The surface treatment layer is a layer obtained by subjecting the coating film to a surface treatment. Examples of the surface treatment include corona discharge treatment, plasma discharge treatment, chemical conversion treatment, and blast treatment. Any processing may adopt a conventionally known method.

Above all, the surface treatment layer is preferably obtained by corona discharge treatment and / or plasma discharge treatment. The discharge in the corona discharge treatment and the plasma discharge treatment is preferably performed at a line speed of 5 to 1000 m / min and a discharge intensity of 0.1 to 10 kW. The line speed is more preferably 10 to 1000 m / min, still more preferably 10 to 900 m / min. The discharge intensity is more preferably 0.1 to 8 kW, and further preferably 0.1 to 6 kW.
The treatment temperature can be arbitrarily set within a range of a lower limit of 0 ° C. and an upper limit of 100 ° C.

The said surface treatment layer may be formed only in the surface on the opposite side to the water-impermeable sheet of the said coating film, and may be formed in both surfaces.

The water-impermeable sheet that constitutes the back sheet of the solar cell module of the present invention is a layer that is provided so that moisture does not permeate the sealing material or solar cell, and is a material that does not substantially permeate water. Although it can be used, PET sheets, Si-deposited PET sheets, thin metal sheets such as aluminum and stainless steel, and the like are frequently used in terms of weight, price, flexibility, and the like. Of these, PET sheets are often used. The thickness is usually about 50 to 250 μm. Of these, Si vapor-deposited PET sheets are often used when moisture resistance is particularly required. The thickness is usually about 10 to 20 μm.

Moreover, in order to improve adhesiveness with the said coating film, you may perform conventionally well-known surface treatment to a water-impermeable sheet. Examples of the surface treatment include corona discharge treatment, plasma discharge treatment, chemical conversion treatment, and blast treatment in the case of a metal sheet.

The method for forming the coating film on the water-impermeable sheet is as described above.
The said coating film may be formed only in the single side | surface of the said water-impermeable sheet, and may be formed in both surfaces.

This invention is also a solar cell module which has the said back sheet and the sealing material layer formed on this back sheet.

Since the back sheet has a coating film made of a specific paint and surface-treated on one or both sides of the water-impermeable sheet, the solar cell module of the present invention including the back sheet is long. It is possible to maintain high power generation efficiency over a period.

Moreover, since the said back sheet is excellent also in adhesiveness with sealing material (for example, EVA), in the solar cell module of this invention provided with this back sheet, a space | gap arises in the interface of a sealing material layer and a back sheet. It is difficult and can protect a photovoltaic cell more reliably.

The solar cell module of the present invention can be used even in a hot and humid environment by having the above-described configuration.

The sealing material layer is a layer for sealing the solar battery cell, and is composed of ethylene / vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), silicone resin, epoxy resin, acrylic resin, or the like. It is preferable. Of these, EVA is preferably used.

The solar cell module of this invention WHEREIN: It is preferable that the said sealing material layer is formed on the surface treatment layer formed on the coating film in this invention. In this case, since the sealing material layer and the surface treatment layer are in direct contact with each other, the effect of maintaining the power generation efficiency over a long period of time and the effect of improving the adhesion between the sealing material layer and the back sheet are made more prominent. Can do.

As a preferable structure of the solar cell module, for example, those shown in FIGS.
In the first structure shown in FIG. 1, the solar cell 1 is sealed with a sealing material layer 2, and the sealing material layer 2 is sandwiched between a surface layer 3 and a back sheet 4. . The back sheet 4 further comprises a water-impermeable sheet 5 and a cured coating film 6 obtained from the paint in the present invention. In this first structure, the cured coating film 6 is provided only on the sealing material layer 2 side.

The sealing material layer 2 is made of an ethylene / vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), a silicone resin, an epoxy resin, an acrylic resin, or the like.
For the surface layer 3, a glass plate is usually used, but a flexible material such as a resin sheet may be used.

In the second structure shown in FIG. 2, the back sheet 4 has a three-layer structure in which a cured coating film 6 is formed on both surfaces of a water-impermeable sheet 5.

Although this 2nd structure increases the film thickness of a back sheet, the power generation efficiency maintenance and adhesion by the cured coating film 6 on the sealing material layer 2 side, and the cured coating film on the opposite side to the sealing material layer 2 6 has both advantages of weather resistance.

As a back sheet having a three-layer structure, a fluorine-containing polymer having a cured coating film obtained from the paint according to the present invention formed on one surface of a water-impermeable sheet and having no curable functional group on the other surface. It may be a three-layer back sheet formed by forming a cured coating film of a paint, a fluorine-containing polymer sheet, a polyester sheet, or a coating film (other sheet or coating film) of a polyester paint.

In the third structure shown in FIG. 3, the back sheet 4 has a cured coating film 6 obtained from the paint according to the present invention on the sealing material layer 2 side of the water-impermeable sheet 5, and the sealing material layer 2. It has a structure in which another coating film 7 is formed on the opposite side.
The material constituting the coating film 7 may be a cured coating film of a fluorine-containing polymer paint having no curable functional group, a fluorine-containing polymer sheet, a polyester sheet, or a coating film of a polyester paint.

As a cured coating film of the above-mentioned fluorine-containing polymer paint having no curable functional group, for example, a cured coating of a paint in which tetraalkoxysilane or a partial hydrolyzate thereof is blended with PVdF described in JP-A-2004-214342. Film, cured coating film of mixed paint of VdF / TFE / CTFE copolymer and alkoxysilane unit-containing acrylic resin, cured coating film of mixed paint of VdF / TFE / HFP copolymer and hydroxyl group-containing acrylic resin, VdF / Examples thereof include a cured coating film of a paint in which an aminosilane coupling agent is blended with an HFP copolymer. The film thickness is usually preferably 5 to 300 μm from the viewpoint of good concealability, weather resistance, chemical resistance, and moisture resistance. More preferably, it is 10-100 micrometers, More preferably, it is 10-50 micrometers. In this case also, a primer layer or the like may be interposed.

Examples of the fluoropolymer sheet include a PVdF sheet, a PVF sheet, a PCTFE sheet, a TFE / HFP / ethylene copolymer sheet, a TFE / HFP copolymer (FEP) sheet, a TFE / PAVE copolymer (PFA) sheet, and ethylene. Examples thereof include fluorine-containing polymer sheets used in current backsheets such as a / TFE copolymer (ETFE) sheet and an ethylene / CTFE copolymer (ECTFE) sheet. The film thickness is usually preferably 5 to 300 μm from the viewpoint of good weather resistance. More preferably, it is 10-100 micrometers, More preferably, it is 10-50 micrometers.

As said polyester sheet, what is used with the conventional back sheet can be used as it is, and the adhesion to the water-impermeable sheet 5 is an acrylic adhesive, urethane adhesive, epoxy adhesive, polyester adhesive. It can be performed by an agent or the like. The film thickness is usually preferably 5 to 300 μm from the viewpoint of good weather resistance, cost, and transparency. More preferably, it is 10-100 micrometers, More preferably, it is 10-50 micrometers.

Examples of the polyester paint include those using a saturated polyester resin using polyvalent carboxylic acid and polyhydric alcohol, and those using an unsaturated polyester resin using maleic anhydride, fumaric acid and the like and glycols, etc. A coating film can be formed by a coating method such as roll coating, curtain coating, spray coating, or die coating. The film thickness is preferably 5 to 300 μm from the viewpoint of good concealability, weather resistance, chemical resistance, and moisture resistance. More preferably, it is 10-100 micrometers, More preferably, it is 10-50 micrometers. In this case also, a primer layer or the like may be interposed.

In the solar cell module of the present invention, the maximum output after 4000 hours of the dump heat test is preferably 90% or more of the maximum output at the start of the test. Such a solar cell module can maintain high power generation efficiency even during long-term use. The maximum output after 4000 hours of the dump heat test is more preferably 94% or more of the maximum output at the start of the test.

Since the back sheet of the solar cell module of the present invention has the above-described configuration, it is possible to configure a solar cell module that can maintain high power generation efficiency over a long period of time.

FIG. 1 is a schematic cross-sectional view of a first structure of a solar cell module. FIG. 2 is a schematic cross-sectional view of a second structure of the solar cell module. FIG. 3 is a schematic cross-sectional view of a third structure of the solar cell module.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Preparation Example 1
Curable TFE copolymer (Zeffle GK570 manufactured by Daikin Industries, Ltd., solid content 65 mass%, hydroxyl value 60 mg KOH / g, solvent: butyl acetate) 202 parts by mass, titanium oxide (Sakai Chemical Industry Co., Ltd.) as a white pigment D918) 263 parts by mass and 167 parts by mass of butyl acetate were premixed under stirring, and then 632 parts by mass of glass beads having a diameter of 1.2 mm were added and dispersed at 1500 rpm for 1 hour with a pigment disperser. Thereafter, the glass beads were filtered through a # 80 mesh sieve, and 283 parts by mass of a curable TFE copolymer (Zeffle GK570) and 85 parts by mass of butyl acetate were added to the solution to prepare a white dispersion liquid 1.

100 parts by weight of this white dispersion 1 7 parts by weight of a curing agent (Sumijour N3300 (manufactured by Sumika Bayer)) (1.0 equivalent to 1 equivalent of the curable functional group in the curable TFE copolymer) The paint 1 was prepared.

Preparation Example 2
100 parts by mass of white dispersion 1 prepared in Preparation Example 1 above, 14 parts by mass of Takenate D120N (Mitsui Chemicals) as a curing agent (1 per 1 equivalent of the curable functional group in the curable TFE copolymer) (Corresponding to 0.0 equivalent), and paint 2 was prepared.

Preparation Example 3
100 parts by mass of the white dispersion 1 prepared in Preparation Example 1 above, 14 parts by mass of Takenate D140N (Mitsui Chemicals) as a curing agent (1 per 1 equivalent of the curable functional group in the curable TFE copolymer) (Corresponding to 0.0 equivalent), and paint 3 was prepared.

Preparation Example 4
Curable CTFE copolymer (Lumiflon LF200 manufactured by Asahi Glass Co., Ltd., solid content 60% by mass, hydroxyl value 52 mg KOH / g, solvent: xylene) 202 parts by mass, titanium oxide (manufactured by Sakai Chemical Industry Co., Ltd.) as a white pigment D918) 242 parts by mass and 154 parts by mass of butyl acetate were premixed with stirring, and then 632 parts by mass of glass beads having a diameter of 1.2 mm were added and dispersed with a pigment disperser at 1500 rpm for 1 hour. Thereafter, the glass beads were filtered through a # 80 mesh sieve, and 283 parts by mass of curable CTFE copolymer (Lumiflon LF200) and 78 parts by mass of butyl acetate were added to the solution to prepare a white dispersion 2.

100 parts by weight of this white dispersion 2 6 parts by weight of a curing agent (Sumijour N3300 (manufactured by Sumika Bayer)) (1.0 equivalent to 1 equivalent of the curable functional group in the curable CTFE copolymer) The paint 4 was prepared.

Production Example 1
As a water-impermeable sheet, a PET film (Lumirror S10 manufactured by Toray Industries, Inc., thickness 250 μm. Sheet A) is used, and the coating 1 prepared in Preparation Example 1 on one side of the sheet A has a dry film thickness of 10 μm. It was coated with a coater so as to become, and dried at 120 ° C. for 2 minutes. Further, the other surface was similarly coated and dried to prepare a backsheet A1 having a three-layer structure.

Production Example 2
Back sheet A2 was produced in the same manner as in Production Example 1 using paint 2 produced in Preparation Example 2.

Production Example 3
Back sheet A3 was produced in the same manner as in Production Example 1 using paint 3 produced in Preparation Example 3.

Production Example 4
A backsheet A4 was produced in the same manner as in Production Example 1 using the paint 4 produced in Preparation Example 4.

The surface on the EVA adhesive layer side of the backsheets A1 to A4 produced in Production Examples 1 to 4 (surface to be adhered to the EVA layer in the process described later) is a line speed of 100 m / min, discharge strength using a corona discharge treatment machine. Processing was performed at 1 kW to prepare surface-treated back sheets B1 to B4.

Example 1
In order to obtain a solar cell module configured as shown in FIG. 2, a resin comprising a tempered glass plate (18 cm square) as the surface layer 3 and an ethylene-vinyl acetate copolymer (EVA) as the sealing material layer 2. The sheet (18 cm square), the polycrystalline silicon solar cell (15 cm square) for the solar battery cell 1, and the back sheet B1 (18 cm square) prepared above and subjected to corona discharge treatment as the back sheet 4 were used. Laminate with the corona-treated surface facing towards the EVA side, and laminate using a vacuum laminator (manufactured by NPC) at a temperature of 135 ° C., evacuation for 5 minutes, and atmospheric pressure for 15 minutes. Was made. When the laminated body for solar cell modules was produced, the electric wire wired to the solar cell was taken out between the solar cell 1 and the sealing material layer 2 to the outside.

Next, the end face of the solar cell module laminate produced above is sealed with a frame (aluminum), and a commercially available silicone sealant (manufactured by Toray Dow Corning Co., Ltd.) is placed between the frame and the solar cell module laminate. The solar cell module M1 was produced by pouring, bonding and sealing, and curing at room temperature for 1 week.

Example 2
Using the surface-treated backsheet B2 as the backsheet 4, a solar cell module M2 was produced in the same manner as in Example 1.

Example 3
Using the surface-treated backsheet B3 as the backsheet 4, a solar cell module M3 was produced in the same manner as in Example 1.

Example 4
Using the surface-treated backsheet B4 as the backsheet 4, a solar cell module M4 was produced in the same manner as in Example 1.

Comparative Example 1
In place of the back sheet 4 of Example 1, a back sheet T1 in which a commercially available vinyl fluoride polymer (PVF) film for a solar battery back sheet is laminated on a water-impermeable sheet instead of the cured coating film 6 is particularly a surface. Used without treatment. Otherwise, a solar cell module M5 was produced in the same manner as in Example 1.

Comparative Example 2
In place of the backsheet 4 of Example 1, a surface of a backsheet K1 in which a commercially available vinylidene fluoride polymer (PVDF) film for solar battery backsheet is laminated on a water-impermeable sheet instead of the cured coating film 6 Used without treatment. Otherwise, a solar cell module M6 was produced in the same manner as in Example 1.

Comparative Example 3
Instead of the back sheet 4 of Example 1, a back sheet A1 that was not subjected to surface treatment was used. Otherwise, a solar cell module M7 was produced using the same method as in Example 1.

The test method and measurement method are as follows.

(Film thickness)
According to JIS C-2151, it measured with the micrometer (made by Mitutoyo Corporation).

(Power generation efficiency)
According to JIS C8913, it measured using the solar simulator (made by Nisshinbo Mechatronics).

(Accelerated endurance test (dump heat test, high temperature and humidity test))
The test was conducted according to JIS C60068-2-78 with reference to JIS C8990 (temperature: 85 ° C., relative humidity: 85%).
Every time an arbitrary time elapses, the power generation efficiency was measured by the method described above. The results are shown in Table 1.

1: Solar cell 2: Sealing material layer 3: Surface layer 4: Back sheet 5: Water-impermeable sheet 6: Cured coating film 7: Other coating film

Claims (8)

A water-impermeable sheet, and a solar cell module backsheet having a coating film formed on at least one surface of the water-impermeable sheet,
The coating film is made of a paint containing a curable functional group-containing fluorine-containing polymer,
A back sheet for a solar cell module, wherein a surface treatment layer is formed on at least the surface of the coating film opposite to the water-impermeable sheet. The solar cell module backsheet according to claim 1, wherein the surface treatment layer is obtained by corona discharge treatment and / or plasma discharge treatment. The curable functional group-containing fluorine-containing polymer is a polymer unit based on a fluorine-containing monomer, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an acid anhydride monomer, an amino group-containing monomer, and The back sheet of the solar cell module according to claim 1 or 2, comprising a polymer unit based on at least one curable functional group-containing monomer selected from the group consisting of silicone vinyl monomers. The backsheet for a solar cell module according to claim 3, wherein the fluorine-containing monomer is at least one selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride. The coating is further derived from a polyisocyanate compound derived from at least one isocyanate selected from the group consisting of xylylene diisocyanate and bis (isocyanatomethyl) cyclohexane, a blocked isocyanate compound based on hexamethylene diisocyanate, and derived from hexamethylene diisocyanate. The back sheet of the solar cell module according to claim 1, 2, 3 or 4, comprising at least one compound selected from the group consisting of a polyisocyanate compound and a polyisocyanate compound derived from isophorone diisocyanate. A solar cell module comprising: the backsheet according to claim 1, and a sealing material layer formed on the backsheet. The solar cell module according to claim 6, wherein the sealing material layer is formed on the surface treatment layer. The solar cell module according to claim 6 or 7, wherein the maximum output after 4000 hours of the dump heat test is 90% or more of the maximum output at the start of the test.

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