TW201345980A - Coating material, coating film, solar-cell-module backsheet, and solar-cell module - Google Patents

Abstract

The purpose of the present invention is to provide the following: a coating material that can form a coating film with excellent block resistance; said coating film; a solar-cell-module backsheet that includes said coating film; and a solar-cell module. The present invention is a coating material characterized by containing the following: a fluorine-containing polymer that contains a curable functional group; and a polyisocyanate compound derived from isophorone diisocyanate.

Description

Coating, coating film, back panel of solar cell module and solar cell module

The invention relates to a coating, a coating film, a back sheet of a solar battery module, and a solar battery module. More specifically, it relates to a coating suitable for coating a back sheet of a solar cell module, a coating film obtained from the coating, and a back sheet and a solar cell module of the solar cell module having the coating film.

The solar cell module is usually composed of a surface layer, a sealing material layer for sealing the solar cell unit, and a back sheet. The sealing material forming the sealant layer is usually a copolymer of ethylene and vinyl acetate (hereinafter also referred to as EVA).

For the back sheet, various properties such as mechanical strength, weather resistance, water resistance, moisture resistance, and electrical insulation are required. Generally, the structure of the backboard is a multi-layer structure, for example, from the side in contact with the sealing material layer of the solar cell unit, sequentially composed of a weathering layer/electrically insulating layer/waterproof/wetproof layer/back layer on the back side of the solar cell. .

Generally, the weather-resistant layer and the back surface layer use a polyvinyl fluoride film for the reasons of weather resistance, water repellency, moisture resistance, and electrical insulation, and a PET film is used as the base material sheet. Further, when the back sheet requires a high waterproof and moisture-proof effect, a PET film on which a metal compound such as cerium oxide is deposited or a metal layer such as aluminum foil is provided on the surface of the base sheet.

In order to satisfy various required characteristics such as required characteristics, durability, and light blocking properties, the thickness of the back sheet is usually set to 20 to 500 μm. However, in recent years, lightweight and thin film of the back sheet have been demanded.

Therefore, it is proposed to use a resin coating to form the same layer in place of the resin sheet. For example, an epoxy resin paint is used as a resin paint (see, for example, Patent Document 1). However, the epoxy resin coating is still insufficient in the weather resistance of the cured coating film, and has not been put into practical use.

Further, a two-layer structure back sheet in which a metal substrate (water-impermeable sheet) is coated with a PVdF-based coating material in which a specific amount of tetraalkoxysilane or a partial hydrolyzate thereof is blended in a PVdF having no functional group is proposed. (See, for example, Patent Document 2). Since this PVdF-based coating material does not have a functional group due to PVdF, it is inferior to the EVA of the sealing material when it is used alone. In this regard, in Patent Document 2, it is intended to improve the orientation of the tetraalkoxynonane or a partial hydrolyzate thereof to the interface with EVA by blending a specific amount of tetraalkoxynonane or a partial hydrolyzate thereof.

In addition, a back sheet of a solar cell module in which a cured coating film of a fluoropolymer coating containing a curable functional group is formed on at least one surface of a water-impermeable sheet is proposed (see, for example, Patent Document 3). The curable functional group-containing fluoropolymer is, for example, a curable tetrafluoroethylene (TFE) copolymer (Zeffle GK570). Patent Document 3 discloses that by using the curable functional group-containing fluoropolymer coating material, the thickness of the back sheet can be made thinner and the mechanical strength can be maintained while being bonded to a conventional sheet. The film formation and weight reduction or the introduction of a functional group into the fluoropolymer can improve the adhesion to the water-impermeable sheet without adding a tetraalkoxy decane or the like.

Further, it is proposed to form a solar battery module back with a hard coat layer containing a coating of a fluoropolymer (A) on one side or both sides of a base sheet. The plate (see, for example, Patent Document 4), the fluoropolymer (A) has a repeating unit derived from a fluoroolefin (a), a repeating unit derived from a bridging group-containing monomer (b), and a non-four-order A repeating unit of an alkyl group-containing monomer (c) in which a carbon atom has a carbon number of 2 to 20 and a linear or branched alkyl group and a polymerizable unsaturated group are bonded by an ether bond or an ester bond. Patent Document 4 discloses that the cured coating film layer is excellent in flexibility and adhesion to a substrate, and does not cause cracking, breakage, whitening or peeling, and is lightweight and has excellent productivity. The backplane for the module.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 7-176775

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-214342

[Patent Document 3] International Publication No. 2007/010706

[Patent Document 4] International Publication No. 2009/157449

As described above, although various coatings for forming a cured coating film which can be suitably used for a back sheet of a solar cell module have been examined, there is still room for review in order to realize various required characteristics at a higher level.

For example, conventional coatings also require more adequate inhibition of adhesion. In addition, the adhesion means that when the coated product is wound or stacked, the contact faces (the coated surface and the uncoated surface, the coated surface and the other coated surface, etc.) are unnecessarily formed and become difficult to peel off, or The coating film of the coated surface is attached to the contact surface with the coating surface phenomenon.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coating material capable of forming a coating film excellent in blocking resistance, a coating film, and a back sheet and solar cell of the solar battery module having the coating film. Module.

The present inventors conducted various investigations on a coating material which can form a coating film excellent in adhesion resistance to a contact surface, and found that in a coating material containing a fluoropolymer containing a curing functional group, by appropriately selecting a kind of hardening agent It is possible to obtain a coating which can provide a hardened coating film which is more excellent in adhesion resistance to a contact surface than a conventional coating. In other words, when the hardener is a polyisocyanate compound derived from ISOPHORONE DIISOCYANATE, when the article (sheet or the like) on which the coating film is formed is wound or stacked, compared with the conventional one The coating film obtained by the coating can more sufficiently inhibit the adhesion of the coating film to the non-coated surface or other coated surface that is in contact with the coating film. Further, it has been found that by forming the coating film on a substrate such as a water-impermeable sheet or the like, a back sheet of a solar cell module excellent in adhesion resistance to a contact surface can be obtained, and the present invention has been completed.

In other words, the present invention is a coating characterized by containing a fluoropolymer containing a curable functional group and a polyisocyanate compound derived from a diisocyanate isophorone.

The present invention is a coating film which is characterized by the above coating.

The present invention relates to a back sheet of a solar cell module, which is characterized in that it has a water-impermeable sheet and is formed on at least one side of the water-impermeable sheet. A coating film composed of the above coating material.

The present invention relates to a solar cell module characterized by having a water-impermeable sheet, a coating film formed of the coating material formed on at least one side of the water-impermeable sheet, and a sealing material layer formed on the coating film. .

The invention is described in detail below.

The coating of the present invention contains a fluoropolymer having a curable functional group.

The fluoropolymer containing a curable functional group is, for example, a polymer in which a fluoropolymer introduces a curable functional group. Further, the fluoropolymer includes a resinous polymer having a clear melting point, an elastomeric polymer exhibiting rubber elasticity, and a thermoplastic elastomeric polymer in between.

The functional group which imparts curability to the fluoropolymer, for example, has a hydroxyl group (except for a hydroxyl group contained in a carboxyl group, the same applies hereinafter), a carboxyl group, a group represented by -COOCO-, a cyano group, an amine group, and a glycidyl group. Further, a decyl group, a silanate group, an isocyanate group or the like can be appropriately selected in accordance with the ease of production of the polymer or the curing system. Among them, from the viewpoint of good curing reactivity, 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 amine group, and a decyl group is preferred; more preferably, it is selected. At least one group of a group of a free hydroxyl group, a carboxyl group, an amine group, and a decyl group; in particular, a viewpoint that the polymer is easily obtained or has good reactivity, and more preferably selected from the group consisting of a hydroxyl group and a carboxyl group. At least 1 group. These hardening functional groups are usually introduced into the fluoropolymer by copolymerization of a fluorine-containing monomer and a monomer having a curable functional group.

a monomer having a hardening functional group, for example, a monomer having a hydroxyl group, and a carboxyl group One type or two or more kinds of these may be used as the monomer, the amine group-containing monomer, and the polyoxymethylene-based vinyl monomer.

The fluoropolymer containing a curable functional group preferably contains a polymerization unit derived from a fluorine-containing monomer, and a monomer selected from a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amine group-containing monomer, and a polyfluorene. A polymerization unit of at least one type of a curing functional group-containing monomer in which the oxygen-based vinyl monomer is a group. Further, the fluoropolymer containing a curable functional group preferably contains at least one selected from the group consisting of a polymerization unit derived from a fluorine-containing monomer and a monomer selected from a monomer containing a hydroxyl group and a monomer having a carboxyl group. A unit of polymerization of a monomer of a hardenable functional group.

The polymerization unit derived from the monomer having a curable functional group is preferably from 1 to 20 mol% based on the total polymerization unit of the fluoropolymer containing the curable functional group. A more preferred lower limit is 2 mol%, and a more preferred upper limit is 10 mol%.

a fluorine-containing monomer, that is, a monomer for forming a fluoropolymer into which a curable functional group is introduced, for example, tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and fluorovinyl ether; One or two or more of these may be used.

Among them, 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 is more preferable.

Specific examples of the fluorine-containing polymer into which the monomer having a curing functional group or the curable functional group is introduced will be described later.

The coating system of the present invention further contains a polyisocyanate compound derived from isophorone diisocyanate (IPDI) (hereinafter sometimes referred to simply as poly Isocyanate compound). The polyisocyanate compound functions as a hardener in the coating of the present invention. When the polyisocyanate compound as described above is used as a curing agent, when the cured coating film obtained from the coating material of the present invention and the substrate (water-impermeable sheet) constitute the back sheet of the solar cell module, in the winding step or the like, The cured coating film is excellent in blocking resistance to the surface to be contacted.

The polyisocyanate compound may, for example, be an addition product obtained by subjecting the above-mentioned isophorone diisocyanate to an aliphatic polyol having three or more members, and an adduct obtained from isophorone diisocyanate. A polycyanate structure (nurate structure) and a biuret composed of isophorone diisocyanate.

The above adduct is preferably, for example, the following general formula (1): (In the formula, R ¹ represents an aliphatic hydrocarbon group having 3 to 20 carbon atoms. The R ² system has the following chemical formula (2): The group represented. The k is an integer represented by 3 to 20).

R ¹ in the above general formula (1) is based on the hydrocarbon group of the above-described trivalent or higher aliphatic polyol, more preferably an aliphatic hydrocarbon group having 3 to 10 carbon atoms, and more preferably an aliphatic hydrocarbon group having 3 to 6 carbon atoms.

The k-series corresponds to the number of valences of the aliphatic polyhydric alcohol of 3 or more. The above k is preferably an integer of 3 to 10, more preferably an integer of 3 to 6.

One or more of the above polycyanate structural system molecules have the following chemical formula (3): Indicates the cyanurate ring.

The above-mentioned cyanurate structure, for example, a trimer obtained by trimerization of isophorone diisocyanate, a pentamer obtained by pentamerization reaction, and a heptapolymerization reaction Heptamer and so on.

Among them, it is preferable to use the following general formula (4): (Wherein, R ² the same system (1) of the general formula R ²⁾ of the trimer. In other words, the above trimeric cyanate structure is preferably a trimer of isophorone diisocyanate.

The above biuret has the general formula (5) below: (Wherein, R ² the same line (1) in the general formula R ²⁾ a compound represented by the structure of, and obtaining the different cyanurate structured body of conditions, by a diisocyanate iso The phorone is obtained by three quantifications.

The polyisocyanate compound is preferably at least one selected from the group consisting of the above-mentioned adduct and the above-mentioned trimeric cyanate structure. In other words, the polyisocyanate compound is preferably selected from the group consisting of an addition product obtained by addition polymerization of an isophorone diisocyanate and an aliphatic polyol having 3 or more members, and isophorone diisocyanate. At least one of the tricyanate structures is a group.

Specific examples of the above polyisocyanate compound will be described later.

The coating material of the present invention may further contain other components as long as it contains the above-mentioned curable functional group-containing fluoropolymer and the above polyisocyanate compound. One or two or more kinds of these other components can be used.

Hereinafter, the coating of the present invention will be described in more detail with reference to specific examples.

<Fluoropolymer containing a curable functional group>

The monomer having a curable functional group is, for example, the following, but is not limited thereto. One or two or more of these may be used.

(1-1) Hydroxyl-containing monomer:

The hydroxyl group-containing monomer is, for example, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4- a hydroxyl group-containing vinyl ether such as hydroxybutyl vinyl ether, 4-hydroxy-2-methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether or 6-hydroxyhexyl vinyl ether; 2-hydroxyl group A hydroxyl group-containing allyl ether such as ethyl allyl ether, 4-hydroxybutyl allyl ether or glycerol monoallyl ether. Among these, a hydroxyl group-containing vinyl ether, particularly 4-hydroxybutyl vinyl ether or 2-hydroxyethyl vinyl ether, is preferable in terms of polymerization reactivity and hardenability of a functional group.

Other hydroxyl group-containing monomers include, for example, hydroxyalkyl (meth)acrylate such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

(1-2) Monomers containing a carboxyl group:

The monomer having a carboxyl group, for example, has the general formula (6): (wherein R ³ , R ⁴ and R ⁵ are the same or different and each are a hydrogen atom, an alkyl group, a carboxyl group or an ester group; n is 0 or 1) represents an unsaturated monocarboxylic acid or an unsaturated dicarboxylic acid. An unsaturated carboxylic acid such as a monoester or an acid anhydride; or a general formula (7): (wherein R ⁶ and R ⁷ are the same or different, each being a saturated or unsaturated linear or cyclic alkyl group; n is 0 or 1; m is 0 or 1) represents a carboxyl group-containing vinyl ether. Monomers, etc.

Specific examples of the above-mentioned carboxyl group-containing vinyl ether monomer include acrylic acid, methacrylic acid, vinyl acetic acid, crotonic acid, cinnamic acid, 3-allyloxypropionic acid, and 3-(2-allyloxy). Ethoxycarbonyl)propionic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, maleic anhydride, fumaric acid, fumaric acid monoester, vinyl phthalate, benzene Tetra-vinyl acetate and the like. Among these, crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, 3-allyloxypropionic acid, which are less polymerizable, are homopolymerized. It is preferred because it is low in nature and hard to produce a homopolymer.

Specific examples of the carboxyl group-containing vinyl ether monomer represented by the above general formula (7) include, for example, 3-(2-allyloxyethoxycarbonyl)propionic acid and 3-(2-allyloxybutylene). One or two or more kinds of oxycarbonyl)propionic acid, 3-(2-vinyloxyethoxycarbonyl)propionic acid, and 3-(2-vinyloxybutoxycarbonyl)propionic acid. Among these, 3-(2-allyloxyethoxycarbonyl)propionic acid or the like is preferred because it has good stability or polymerization reactivity.

(1-3) Amino group-containing monomer:

The amine group-containing monomer, for example, an amine vinyl ether represented by CH ₂ =CH-O-(CH ₂ ) _x -NH ₂ (x=0~10), with CH ₂ =CH-O- Allylamines represented by CO(CH ₂ ) _x -NH ₂ (x=1~10); others such as aminomethylstyrene, vinylamine, acrylamide, vinylacetamide, ethylene Carbenamide and the like.

(1-4) Polyfluorene-based vinyl monomer:

Polyoxymethylene-based vinyl monomer, for example, CH ₂ =CHCO ₂ (CH ₂ ) ₃ Si(OCH ₃ ) ₃ , CH ₂ =CHCO ₂ (CH ₂ ) ₃ Si(OC ₂ H ₅ ) ₃ , 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(CH 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 such as (meth) acrylates; 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 (OCH3) ₂ , CH ₂ =CHSi(OCOCH ₃ ) ₃ , CH ₂ =CHSi(CH ₃ ) ₂ (OC ₂ H ₅ ), CH ₂ =CHSi(CH ₃ ) ₂ SiCH 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 decane such as vinyl trichloromethane or a partial hydrolyzate thereof; trimethoxy decyl ethyl vinyl ether, triethoxy decyl ethyl vinyl ether, trimethoxy decyl butyl Vinyl ethers such as vinyl ether, methyl dimethoxy decyl alkyl vinyl ether, trimethoxy decyl propyl vinyl ether, and triethoxy decyl propyl vinyl ether.

The fluoropolymer to which the curable functional group is introduced depends on, for example, the polymerization unit constituting the polymer.

(1) Perfluoroolefin-based polymers mainly composed of perfluoroolefin units:

Specific examples include a homopolymer of tetrafluoroethylene (TFE) or a copolymer of TFE and hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), and the like, and, for example, A copolymer of other monomers polymerized, and the like.

Other monomers copolymerizable as described above, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, trimethyl vinyl acetate, vinyl hexanoate, versatic acid Vinyl esters of vinyl ester, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate, vinyl Benzoic acid, vinyl p-t-butyl benzoate, etc.; methyl An alkyl vinyl ether such as vinyl ether, ethyl vinyl ether, butyl vinyl ether or cyclohexyl vinyl ether; a non-fluorinated olefin such as ethylene, propylene, n-butene or isobutylene; A fluorine-based monomer such as ethylene (VdF), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF) or fluorovinyl ether, but is not limited thereto.

Among these, the TFE-based polymer mainly composed of TFE is preferable because it is excellent in pigment dispersibility, weather resistance, copolymerization property, and chemical resistance.

Specific perfluoroolefin-based polymers containing a hardening functional group, for example, a copolymer of TFE/isobutylene/hydroxybutyl vinyl ether/other monomer, TFE/versatic acid vinyl ester/hydroxybutyl group a copolymer of vinyl ether/other monomer, a copolymer of TFE/VDF/hydroxybutyl vinyl ether/other monomer, etc., preferably a copolymer of TFE/isobutylene/hydroxybutyl vinyl ether/other monomer , TFE / versatic acid vinyl ester / hydroxybutyl vinyl ether / copolymer of other monomers, and the like.

The TFE-based coating composition for a coating material is, for example, a ZEFFLE (registered trademark) GK series manufactured by Daikin Industries Co., Ltd., and the like.

(2) CTFE-based polymers mainly composed of chlorotrifluoroethylene (CTFE) units:

Specific examples thereof include a copolymer of CTFE/hydroxybutyl vinyl ether/other monomer.

For the CTFE-based coating composition for a coating, for example, Lumiflon (registered trademark) manufactured by Asahi Glass Co., Ltd., Fluonate (registered trademark) manufactured by DIC Co., Ltd., and Cefral Coat (registered by Central Glass Co., Ltd.) Trademark), Zaflon (registered trademark) of East Asia Synthetic Co., Ltd., etc.

(3) VdF-based polymers mainly composed of vinylidene fluoride (VdF) units:

Specific examples thereof include a copolymer of VdF/TFE/hydroxybutyl vinyl ether/other monomer.

(4) A fluorine-containing alkyl group mainly composed of a fluoroalkyl unit:

Specific examples thereof include CF ₃ CF ₂ (CF ₂ CF ₂ ) _n CH ₂ CH ₂ OCOCH=CH ₂ (a mixture of n=3 and 4)/2-hydroxyethyl methacrylate/stearyl acrylate copolymer, and the like. .

Examples of the fluorine-containing alkyl group-containing polymer include Unidyne (registered trademark) or Ftone (registered trademark) manufactured by Daikin Industries Co., Ltd., and Zonyl (registered trademark) manufactured by Dupont Co., Ltd., and the like.

Among these, in view of weather resistance and moisture resistance, a perfluoroolefin-based polymer is preferred.

The fluoropolymer containing a curable functional group can be produced, for example, by the method disclosed in JP-A-2004-204205.

The content of the above-mentioned curable functional group-containing fluoropolymer in the coating material of the present invention is preferably from 20 to 95% by mass based on 100% by mass based on the total amount of the nonvolatile components in the coating material. More preferably 40 to 95% by mass.

<polyisocyanate compound>

When the polyisocyanate compound is an adduct of the above-mentioned isophorone diisocyanate and a trihydric or higher aliphatic polyol, the aliphatic polyhydric alcohol having 3 or more members, specifically, for example, glycerin or trimethylol Propane (TMP), 1,2,6-hexanetriol, trimethylolethane, 2,4-dihydroxy-3-hydroxymethylpentane, 1,1,1-cis (dihydroxymethyl) a 3-valent alcohol such as propane or 2,2-bis(hydroxymethyl)butanol-3; a 4-valent alcohol such as pentaerythritol or diglycerin; and a 5-valent alcohol such as arabitol, ribitol or xylitol. Alcohol, pentite); sorbitol, mannitol, galactitol, allodulcit, etc. A diol (hexite) or the like. Among them, preferred are trimethylolpropane and pentaerythritol.

The adduct of the present invention can be obtained by addition polymerization of isophorone diisocyanate with an aliphatic polyol having a weight of 3 or more as described above.

The adduct which is suitable for use in the present invention, specifically, for example, has the following general formula (8): (wherein R ⁸ is represented by the following chemical formula (2): The group represented by the group), that is, the polyisocyanate compound obtained by addition polymerization of isophorone diisocyanate and trimethylolpropane (TMP).

The commercially available product of the polyisocyanate compound (the TMP addition substance of the isophorone diisocyanate) represented by the above general formula (8) is, for example, Takenate (registered trademark) D140N (manufactured by Mitsui Chemicals, Inc., containing NCO 11). %)Wait.

City of cyanurate structure composed of isophorone diisocyanate For sale, for example, Desmodur (registered trademark) Z4470 (manufactured by Susei Bayer Aurethane Co., Ltd., containing NCO 11%) and the like.

The content of the polyisocyanate compound is from 0.1 to 5 equivalents, preferably from 0.5 to 1.5 equivalents, per equivalent of the curable functional group in the curable functional group-containing fluoropolymer.

The content of the curable functional group in the fluoropolymer containing the curable functional group is determined by appropriate combination of NMR, FT-IR, elemental analysis, fluorescent X-ray analysis, and neutralization titration depending on the kind of the monomer. get.

In the present specification, the content of the curable functional group-containing fluoropolymer and the polyisocyanate compound is the mass of the nonvolatile matter obtained by removing each solvent or the like.

The coating material of the present invention is prepared into a form of a solvent-based paint, an aqueous paint, a powder paint, or the like by a usual method. Among them, a form of a solvent-based paint is preferred from the viewpoints of easiness of film formation, curability, and good drying property.

The solvent in the solvent-based coating material is preferably an organic solvent, an ester of ethyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, ceramide acetate, propylene glycol methyl ether acetate, etc.; acetone, A Ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; cyclic ethers such as tetrahydrofuran and dioxane; N,N-dimethylformamide, N,N-dimethyl B Amidoxime such as decylamine; aromatic hydrocarbons such as xylene, toluene, and solvent petroleum brain; glycol ethers such as propylene glycol methyl ether and ethyl cyanidin; Alcohol esters; n-pentane, n-hexane, n-heptane, n-octane, n-decane, n-decane, n-undecane, n-dodecane, mineral spirits, etc. Aliphatic hydrocarbons; such mixed solvents and the like.

More preferably, it is an ester, and more preferably butyl acetate.

When the coating material of the present invention is used as a solvent-based coating material, the concentration of the fluoropolymer containing a curable functional group is preferably from 5 to 95% by weight, more preferably from 10 to 70% by weight, based on 100% by mass of the total amount of the coating material.

In the coating of the present invention, various additives may be further blended in accordance with the required characteristics. Examples of the additive include a hardening accelerator, a hardening retarder, a pigment, a pigment dispersant, an antifoaming agent, a flat agent, an ultraviolet absorber, a photostabilizer, a tackifier, a adhesion improver, a matting agent, and the like.

Examples of the hardening accelerator include an organotin compound, an acid phosphate, a reactant of an acidic phosphate and an amine, a saturated or unsaturated polycarboxylic acid or an anhydride thereof, an organic titanate compound, an amine compound, lead octoate, and the like.

One type of the hardening accelerator may be used or two or more types may be used in combination. The blending ratio of the hardening accelerator is preferably from 1.0 × 10 ^-6 to 1.0 × 10 ^-2 parts by weight, more preferably from 5.0 × 10 ^-5 , based on 100 parts by weight of the fluoropolymer containing the curable functional group. ~1.0×10 ^-3 parts by weight or so.

The coating of the present invention further preferably contains a pigment. Thereby, the obtained hardened coating film is excellent in UV shielding property. Further, from the viewpoint of making the appearance of the solar cell module beautiful, it is strongly desired to add a pigment.

Specific examples of the pigment include inorganic pigments such as white pigment titanium oxide, calcium carbonate, or black pigment carbon black, Cu-Cr-Mn alloy, and the like; phthalocyanine, quinophthalone or azo. Organic pigments and the like, but are not limited thereto.

The amount of the pigment added is preferably from 0.1 to 200 parts by weight, more preferably from 0.1 to 160 parts by weight, based on 100 parts by weight of the fluoropolymer containing the curable functional group. Quantities.

The coating material of the present invention further preferably contains an ultraviolet absorber. Since the solar cell is used during the outer period of the ultraviolet ray house, the back plate is required to have countermeasures against ultraviolet ray deterioration. When an ultraviolet absorber is added to the coating material of the present invention, the function of ultraviolet absorbing can be imparted to the cured coating film layer.

The ultraviolet absorber can be used, for example, any of an organic or inorganic ultraviolet absorber. Examples of the organic system include ultraviolet absorbers such as salicylate-based, benzotriazole-based, benzophenone-based, and cyanoacrylate-based; and inorganic-based inorganic-based fillers such as zinc oxide and cerium oxide. A UV absorber or the like is preferred.

The ultraviolet absorbers may be used alone or in combination of two or more. The amount of the ultraviolet absorber is 100% by mass, preferably 0.1 to 15% by mass based on the total amount of the fluoropolymer containing the curable functional group in the coating material. When the amount of the ultraviolet absorber is too small, the effect of improving the light resistance cannot be sufficiently obtained, and even if it is too much, the effect is saturated.

The present invention is also a coating film obtained from the above coating. The coating film can be formed by applying the coating of the present invention to a suitable substrate according to the use and curing. The formation of the cured coating film on the substrate is carried out by applying the coating of the present invention to the substrate in accordance with the coating form thereof.

The coating may be carried out in a temperature range normally under the conditions of the coating form, and when the solvent-based coating material is cured and dried, it is carried out at 10 to 300 ° C, usually at 100 to 200 ° C for 30 seconds to 3 days. Therefore, when the coating of the present invention is applied to the back sheet of the solar cell module, the water-impermeable sheet can also be used to avoid high-temperature treatment such as Si-deposited PET sheet. hardening After drying, it can also be matured. The ripening is usually carried out at 20~300 °C for 1 minute to 3 days.

The coating of the substrate can be carried out by directly applying the coating material of the present invention to a substrate, or by applying a primer layer or the like.

The formation of the primer layer is carried out in accordance with a general method using a conventionally known primer paint. The primer for the primer may, for example, be an epoxy resin, a urethane resin, an acrylic resin, a polyoxymethylene resin, a polyester resin or the like as a representative example.

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 μm or more, and more preferably 10 μm or more. Since the weight reduction effect cannot be obtained because it is too thick, the upper limit is preferably about 1000 μm, more preferably about 100 μm. The film thickness is particularly preferably 10 to 40 μm.

Since the coating film obtained from the coating material of the present invention is excellent in blocking resistance even at the time of winding, it can be suitably used for application of a back sheet of a solar cell module which is generally produced by a winding step.

When applied to the back sheet of the solar cell module, the coating film is formed on one side or both sides of a substrate such as a water-impermeable sheet.

When the coating film obtained from the coating material of the present invention is formed on one side of the substrate, and the other surface of the substrate is a non-coated surface, the coating film is brought into contact with the non-coated surface of the substrate in the winding step. Further, the coating film is formed on one surface of the substrate, and the other surface of the substrate is provided with a coating film made of another coating material (a hard coating film or a polyester coating of a fluoropolymer coating having no curable functional group, which will be described later). When the coating film, primer layer, etc. or other sheets are obtained from the coating of the present invention The coating film is brought into contact with a coating film or other sheet formed of other coating materials on the substrate in the winding step. Further, when the coating film obtained from the coating material of the present invention is formed on both surfaces of the substrate, the coating film is brought into contact with the same type of coating film formed on the other surface of the substrate in the winding step.

When the coating film obtained from the coating material of the present invention has any of the above conditions, it can exhibit excellent blocking resistance to the contact surface.

The present invention is also a back sheet of a solar cell module having a water-impermeable sheet and a coating film formed of the above-mentioned coating material formed on at least one side of the water-impermeable sheet.

The water-impermeable sheet is provided so that moisture does not permeate through the sealing material or the layer of the solar cell, and can be used as long as it is substantially impervious to water, but in terms of weight, price, flexibility, and the like, most of them are used. A PET sheet, a Si vapor-deposited PET sheet, a metal foil such as aluminum or stainless steel, or the like is used. Among them, PET flakes are often used. The thickness is usually about 50 to 250 μm. Among them, in particular, when it is required to prevent moisture, a conventional Si vapor-deposited PET sheet is used. The thickness is usually about 10 to 20 μm.

Further, in order to improve the adhesion to the coating film, a conventionally known surface treatment can be performed on the water-impermeable sheet. The surface treatment includes, for example, a corona discharge treatment, a plasma discharge treatment, and a chemical conversion treatment; and a metal foil, for example, sandblasting treatment or the like.

The method of forming the above coating film on the above water-impermeable sheet is as described above.

The coating film may be formed only on one side of the water-impermeable sheet or on both sides.

The present invention is also a solar cell module having a water-impermeable sheet, a coating film formed of the above-mentioned coating material formed on at least one surface of the water-impermeable sheet, and a sealing material layer formed on the coating film.

Preferred configurations of the solar cell module include those shown in Figs. 1 to 3, for example.

In the first structure shown in FIG. 1, the solar battery cell 1 is sealed to the sealing material layer 2, and the sealing material layer 2 is sandwiched between the surface layer 3 and the backing plate 4. The back sheet 4 is further composed of a water-impermeable sheet 5 and a cured coating film 6 obtained from the coating of the present invention. In the first structure, the cured coating film 6 is provided only on the side of the sealing material layer 2.

The sealing material layer 2 is composed of an ethylene/vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), a polyoxyxylene resin, an epoxy resin, an acrylic resin or the like.

In the surface layer 3, a glass plate is usually used, but a flexible material such as a resin sheet can also be used.

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

This second structure has an advantage of both the cured coating film 6 on the side of the sealing material layer 2 and the cured coating film 6 on the side opposite to the sealing material layer 2, although the film thickness of the back sheet is increased.

The back sheet of the three-layer structure may be formed of a hard coat film obtained from the paint of the present invention on one side of the water-impermeable sheet, and a hard coat film of a fluoropolymer paint having no curable functional group on the other side, a coating film (other sheet or coating film) of a fluoropolymer sheet, a polyester sheet or a polyester coating The back panel of the 3-layer structure.

The third structure shown in FIG. 3 is formed with a hard coating film 6 obtained from the coating material of the present invention on the side of the sealing material layer 2 of the water-impermeable sheet 5, and another coating film 7 is formed on the opposite side to the sealing material layer 2. Construction.

The material constituting the coating film 7 may be a cured coating film of a fluoropolymer coating material having no curable functional group, or may be a coating film of a fluoropolymer sheet, a polyester sheet, or a polyester coating material.

Further, in order to further improve the adhesion between the coating film and the sealing material layer, a conventionally known surface treatment may be performed on the coating film. The surface treatment can be, for example, a corona discharge treatment, a plasma discharge treatment, a chemical conversion treatment, a sandblasting treatment, or the like.

The hardened coating film of the fluoropolymer coating material having no curable functional group, for example, is hardened by coating a tetraalkoxy decane or a partial hydrolyzate thereof in PVdF as described in JP-A-2004-214342. a hardened coating film of a coating film, a mixed coating of a VdF/TFE/CTFE copolymer and an acrylic resin containing an alkoxydecane unit, a hardened coating film of a mixed coating of a VdF/TFE/HFP copolymer and a hydroxyl group-containing acrylic resin, A hardened coating film of a coating of an amine-based decane coupling agent in a VdF/HFP copolymer. The film thickness is usually preferably from 5 to 300 μm from the viewpoint of good concealability, weather resistance, chemical resistance, and moisture resistance. More preferably, it is 10 to 100 μm, and more preferably 10 to 50 μm. At this time, a primer layer or the like may be interposed.

Examples of the above fluoropolymer sheet include PVdF flakes or PVF flakes, PCTFE flakes, TFE/HFP/ethylene copolymer flakes, TFE/HFP copolymer (FEP) flakes, TFE/PAVE copolymer (PFA) flakes, and ethylene. a fluoropolymer sheet of a back sheet such as a /TFE copolymer (ETFE) sheet, an ethylene/CTFE copolymer (ECTFE) sheet, or the like. The film thickness is usually preferably from 5 to 300 μm from the viewpoint of good weather resistance. More preferably, it is 10 to 100 μm, and more preferably 10 to 50 μm.

The polyester sheet can be directly used as a user of a conventional back sheet, and the water-impermeable sheet 5 can be followed by an acrylic adhesive, a urethane-based adhesive, an epoxy-based adhesive, and a poly The ester-based adhesive or the like is carried out. The film thickness is usually preferably from 5 to 300 μm from the viewpoint of weather resistance, cost, and transparency. More preferably, it is 10 to 100 μm, and more preferably 10 to 50 μm.

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

Furthermore, the coating material of the present invention can be applied to various substrates or sheets produced by the winding step, and can be directly applied to a substrate of metal, resin or the like, or to a washable bottom, in addition to the use of the above solar cell module. Overcoating on primer coatings such as wash primers, rust-preventive coatings, epoxy coatings, acrylic coatings, and polyester resin coatings.

Since the coating material of the present invention is formed by the above-described constitution, it is possible to form a coating film having excellent blocking resistance at the time of winding. This coating film is extremely suitable as a coating for the back sheet of a solar cell module.

The invention is explained in more detail by way of examples, but the invention is not limited to the examples.

Modulation example 1

202 parts by mass of a curable TFE-based copolymer (ZEFFLE GK570, manufactured by Daikin Industries Co., Ltd., solid content: 65 mass%, hydroxyl group: 60 mgKOH/g, solvent: butyl acetate), and titanium oxide as a white pigment 263 parts by mass of D918) and 167 parts by mass of butyl acetate were pre-mixed under stirring, and then 632 parts by mass of glass beads having a diameter of 1.2 mm were added, and dispersed by a pigment disperser at 1,500 rpm for 1 hour. Then, the glass beads were filtered through a #80 mesh sieve, and 283 parts by mass of a curable TFE-based copolymer (ZEFFLE GK570) and 85 parts by mass of butyl acetate were added to the solution to prepare a white paint.

In 100 parts by mass of the white paint, 7 parts by mass of a hardener (Takenate D140N, an addition product of IPDI and TMP, an NCO content of 10.8%) was blended (relative to the curable TFE copolymer). The curable functional group was prepared by adding 1 equivalent of the curable functional group to 1.0 equivalent.

Example 1

A PET film (Lumirror S10 manufactured by Toray Industries, Ltd., thickness: 250 μm, and sheet A) was used as the water-impermeable sheet, and the coating material 1 prepared in Preparation Example 1 was applied thereto by using an applicator so that the dried film thickness was 10 μm. One side of the sheet A was dried at 120 ° C for 2 minutes to produce a back sheet A1 having a two-layer structure. This sample was investigated for resistance to adhesion. The results are shown in Table 1.

The test method and measurement method are as follows.

(Adhesion resistance test)

This is carried out in accordance with JIS K5600-3-5. The prepared coating was applied onto a 50 mm × 100 mm PET film, and dried by heating in a dryer (ESPEC, SPHH-400) at 120 ° C for 2 minutes. Then, the test piece was taken out and allowed to cool to room temperature. Next, the film was sandwiched by glass so that the coated surface of the test piece and the uncoated surface were overlapped by an area of 50 mm × 50 mm. The weight of 20 kg was applied thereto, and the pressure was maintained at 40 ° C for 24 hours while applying a pressure of 0.08 MPa to the contact faces of the films.

In the evaluation, two films were allowed to cool to room temperature, and two films were stretched to the left and right to visually observe the state at this time, and the peeling property of the backing plate A1 and PET and the degree of coating film disorder were evaluated in five stages.

The evaluation criteria are as follows.

5: Natural separation.

4: Separate 2 pieces with only a very small force.

3: When applying force, it is peeled off, and the surface of the coating film is slightly disordered.

2: When applying force, it is peeled off, and the surface of the coating film is disordered.

1: Even if the force is applied, it cannot be peeled off.

(film thickness)

It measured by the micrometer (made by Mitsutoyo Corporation) according to JIS C-2151.

Example 2

In addition to the use of Desmodur Z4470 (manufactured by Bayer Aurethane Co., Ltd., IPDI cyanurate structure, NCO content 11%) as a hardener, 28.4 parts by mass (relative to the curable TFE-based copolymer) A coating material 2 was prepared in the same manner as in Preparation Example 1 except that the curable functional group was equivalent to 1.0 equivalent, and a back sheet A2 having a two-layer structure was produced in the same manner as in Example 1. The adhesion resistance of this sample was investigated. The results are shown in Table 1.

Comparative example 1

In addition to Coronate HX (made from Japan Polyurethane Co., Ltd., a trimeric isocyanate structure of hexamethylene diisocyanate, NCO content of 21.1%) as a hardener, 14.8 parts by mass (relative to the hardenable TFE system) Comparative Comparative Coating Material 1 was prepared in the same manner as in Preparation Example 1 except that the curable functional group in the polymer was equivalent to 1.0 equivalent. The comparative backing plate A1 having a two-layer structure was produced in the same manner as in Example 1. The adhesion resistance of this sample was investigated. The results are shown in Table 1.

From the results of Examples 1 and 2 and Comparative Example 1, it was found that the coating films of Examples 1 and 2 using a polyisocyanate compound derived from isophorone diisocyanate as a curing agent were used. When the coating film of Comparative Example 1 of the hardener used was known, it was found that the blocking resistance was excellent. Therefore, it has been confirmed that the constitution of the present invention has technical significance.

1‧‧‧Solar battery unit

2‧‧‧ Sealing layer

3‧‧‧ surface layer

4‧‧‧ Backboard

5‧‧‧Watertight sheets

6‧‧‧ hardened film

7‧‧‧Other coatings

Fig. 1 is a schematic cross-sectional view showing a first structure of a solar battery module.

Fig. 2 is a schematic cross-sectional view showing a second structure of a solar battery module.

Fig. 3 is a schematic cross-sectional view showing a third structure of a solar battery module.

Claims (9)

A coating comprising a fluoropolymer containing a curable functional group and a polyisocyanate compound derived from isophorone diisocyanate. The coating material of claim 1, wherein the fluoropolymer containing a curable functional group contains a polymerization unit based on a fluorine-containing monomer, and is selected from the group consisting of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and an amine group-containing unit. A polymerization unit of at least one type of a curing functional group-containing monomer in which the body and the polyoxynphthyl vinyl monomer are grouped. The coating material according to claim 2, wherein the fluorine-containing single system is at least one selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene and vinylidene fluoride. The coating material according to claim 1, wherein the polyisocyanate compound is selected from the group consisting of an addition product obtained by subjecting an isophorone diisocyanate to an aliphatic polyol having 3 or more members by addition polymerization, and At least one of the group consisting of the cyanurate structures composed of isophorone diisocyanate. A coating according to claim 1, 2, 3 or 4, which further comprises a pigment. A coating according to claim 1, 2, 3, 4 or 5 further comprising an ultraviolet absorber. A coating film characterized by a coating material as disclosed in claim 1, 2, 3, 4, 5 or 6. A back sheet of a solar cell module, characterized by having a water-impermeable sheet and being formed on at least one side of the water-impermeable sheet A coating film consisting of a coating material of the first, second, third, fourth, fifth or sixth aspect of the patent application. A solar cell module characterized by having a water-impermeable sheet and a coating comprising a coating formed on at least one side of the water-impermeable sheet, as in the first, second, third, fourth, fifth or sixth aspect of the patent application. a film and a sealing material layer formed on the coating film.