TWI638014B - Coating, coating film, back panel of solar cell module and solar cell module - Google Patents

Abstract

The present invention provides a coating film obtained by the coating material, a coating film obtained from the coating material, and a back sheet and a solar cell module of the solar cell module having the coating film.

The present invention is a coating characterized by a fluoropolymer containing a curable functional group and a blocked isocyanate based on hexamethylene diisocyanate.

Description

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

The invention relates to a paint, a coating film, a back sheet of a solar battery module, and a solar battery module. More specifically, it is a preferred coating 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 formed by a surface layer, a sealing material layer for sealing the solar cell unit, and a back sheet. As the sealing material for forming the sealing material layer, a copolymer of ethylene and vinyl acetate (hereinafter also referred to as EVA) can be usually used.

In the backing plate, mechanical strength, weather resistance and waterproof are required. Various characteristics such as moisture resistance and electrical insulation. The general backing plate is configured to be a multi-layer structure, for example, by the side of the sealing material layer of the solar cell unit, sequentially by the weathering layer/electrical insulation layer/waterproof. The moisture barrier layer/the inner layer located on the inner side of the solar cell.

Generally in the weathering layer and the inner layer, it is weather resistant and waterproof. A film of polyvinyl fluoride can be used for the reason of excellent moisture resistance and electrical insulation, and a PET film can be used for the substrate sheet. Also, the backplane is required to be highly waterproof. In the case of the moisture-proof effect, a PET film obtained by vapor-depositing a metal compound such as cerium oxide or a metal layer such as an aluminum foil may be provided on the surface of the base sheet.

The thickness of the back sheet is usually 20 to 500 μm in order to satisfy the required characteristics, durability, and light shielding properties. However, in recent years, it is required to back The board is lighter and thinner.

Therefore, it is proposed to form the same layer using a resin coating instead of the resin sheet. For example, the use of an epoxy resin coating as a resin coating is discussed (for example, Patent Document 1 is incorporated by reference). However, the epoxy resin coating is insufficient in terms of weather resistance of the cured coating film, and has not been put into practical use.

Further, it is proposed to apply a two-layer structure of a metal substrate (water-impermeable sheet) to a PVdF-based coating material in which a specific amount of tetraalkoxynonane or a partial hydrolyzate thereof is blended in PVdF having no functional group. A plate (for example, Patent Document 2 is incorporated by reference). This PVdF-based coating material does not have a functional group due to PVdF, and is also inferior in adhesion to EVA of the sealing material alone. In this regard, in Patent Document 2, a specific amount of tetraalkoxynonane or a partial hydrolyzate thereof is blended, and the tetraalkoxynonane or a partial hydrolyzate thereof is aligned at the interface with EVA to improve.

Further, 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 side of a water-impermeable sheet is proposed (for example, Patent Document 3 is incorporated by reference). As the fluoropolymer containing a curable functional group, a curable tetrafluoroethylene (TFE) copolymer (ZEFFLE GK570) is disclosed. Patent Document 3 describes 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, and the film can be thinned as compared with the conventional sheet. The weight reduction or adhesion to the water-impermeable sheet can be improved by introducing a functional group into the fluoropolymer without adding tetraalkoxy decane or the like.

Further, it is proposed to form a repeating unit having a fluoroolefin (a) on one side or both sides of a base sheet, and based on containing a crosslinkable group monomer (b) a repeating unit, and an alkyl group-containing monomer which is bonded to a polymerizable unsaturated group by an ether bond or an ester bond based on a linear or branched alkyl group having 2 to 20 carbon atoms which does not contain a carbon atom of 4 ( c) A back sheet for a solar cell module of a cured coating layer of a coating material of a fluoropolymer (A) of a repeating unit (for example, Patent Document 4 is incorporated by reference). In Patent Document 4, it is described that the flexibility of the cured coating film layer and the adhesion to the substrate are particularly excellent, and it is possible to obtain solar energy which is free from cracks, cuts, whitening, and peeling, and which is lightweight and excellent in productivity. The purpose of the back panel for battery modules.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 7-176775

[Patent Document 2] JP-A-2004-214342

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

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

As described above, various coatings for forming a hard coat layer which can be suitably used in the back sheet of a solar cell module are discussed, and there is room for discussion in order to realize various required characteristics at a higher level.

For example, in the coating material, not only the properties of the obtained coating film but also the rationality or stability in the step of forming the coating film are required. Among them, the period of use indicating the usable time of the paint is improved by the degree of freedom of the step Point 1 is an important indicator. The longer the life of the paint, the more time it takes to apply it. It is also necessary to temporarily store or transfer the paint after preparation of the paint, and to ensure the fluidity of the paint during operation. We look forward to the development of coatings that will improve the use period (extended) regardless of the field.

The present invention is directed to the above-mentioned situation, to provide a coating material having a markedly improved service life (available time), a coating film obtained from the coating material, and a back sheet and a solar battery module of the solar battery module having the coating film. Target person.

The inventors of the present invention have made various discussions on coatings having improved service life in the past, and found that in coatings containing a fluoropolymer containing a curable functional group, the use of the coating can be remarkably improved by appropriately selecting the kind of the hardener. the term. That is, if the hardener is found to be a blocked isocyanate based on hexamethylene diisocyanate, the hardener and the fluoropolymer containing the curable functional group become less reactive in the coating under the use environment, and the use of the coating The term is considerably longer than that of the conventional fluoropolymer containing a curable functional group. Next, it was found that the coating film obtained by such a coating was extremely useful for coating on the back sheet of the solar cell module, and was invented by the present inventors.

That is, the present invention is a coating material characterized by a fluoropolymer containing a curable functional group and a blocked isocyanate containing a hexamethylene diisocyanate.

The present invention is also a coating film characterized by the above-mentioned coating material.

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

The present invention is also a solar cell module characterized by a coating film comprising a water-impermeable sheet, the coating material formed on at least one surface 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 is a fluoropolymer containing a curable functional group.

The fluoropolymer containing a curable functional group may, for example, be a polymer in which a fluoropolymer is introduced into a curable functional group. Further, the fluoropolymer may contain a resin having a refinement of a melting point, an elastomeric polymer exhibiting rubber elasticity, and a thermoplastic elastomer in between.

The functional group which imparts curability to the fluoropolymer may, for example, be 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, or a propylene group. The base, the decyl group, the Silaates group, the isocyanate group and the like can be suitably selected in accordance with the ease of production or the hardening of the polymer. Among them, at least one selected from the group consisting of a hydroxyl group, a carboxyl group, a group represented by a -COOCO- group, a cyano group, an amine group, and a decyl group from the viewpoint of good curing reactivity is preferred, a hydroxyl group, a carboxyl group, At least one selected from the group consisting of an amine group and a decyl group is preferred, and at least one selected from the group consisting of a hydroxyl group and a carboxyl group from the viewpoint of easy availability of the polymer or good reactivity is preferable. The base of 1 is better. Such hardening functional groups, usually by reacting a fluorine-containing monomer with a hardening-containing functional group The monomer is copolymerized and introduced into the fluoropolymer.

The monomer having a curable functional group may, for example, be a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amine group-containing monomer, or an anthrone-based vinyl monomer, and one type or two or more types may be used.

The fluoropolymer containing a curable functional group is contained in a polymerization unit based on a fluorine-containing monomer, and a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amine group-containing monomer, and an anthrone-based vinyl monomer. The polymerization unit of at least one type of the hardenable functional group-containing monomer selected in the group is preferred. Further, the curable functional group-containing fluoropolymer contains at least one curable functional group selected from the group consisting of a fluoromonomer-based polymerization unit and a hydroxyl group-containing monomer and a carboxyl group-containing monomer. The polymerization unit of the monomer is preferred.

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

The fluorine-containing monomer, that is, a monomer which forms a fluorine-containing polymer into which the curable functional group is introduced, may, for example, be tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, ethylene fluoride or fluorovinyl ether, and may be used. One or two or more of these.

Among them, at least one selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride is preferred, and at least one selected from the group consisting of tetrafluoroethylene and chlorotrifluoroethylene is preferred.

Specific examples of the hardening functional group-containing monomer or the fluoropolymer into which the curable functional group is introduced will be described later.

The coating of the present invention further contains a hexamethylene diisocyanate (HDI) block isocyanate (hereinafter also referred to simply as blocked isocyanate). The blocked isocyanate acts as a hardener in the coating of the present invention. By using the above-mentioned block isocyanate as a hardener, the paint of the present invention is made to have a sufficient use period (available time).

In the case of the above-mentioned blocked isocyanate, it is preferred that the polyisocyanate compound (hereinafter, simply referred to as a polyisocyanate compound) derived from hexamethylene diisocyanate is reacted with a blocking agent.

The polyisocyanate compound may, for example, be an isocyanurate structure obtained by addition-polymerization of a hexamethyl-diisocyanate and a trivalent or higher aliphatic polyol, and a hexamethylene diisocyanate. (Urea structure), and diurea formed by hexamethylene diisocyanate.

The above-mentioned adducts may, for example, have the following general formula (1):

The structure represented by (wherein, R ¹ represents an aliphatic hydrocarbon group having 3 to 20 carbon atoms, and k is an integer of 3 to 20) is preferable.

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

The above k is a number corresponding to the valence of the trivalent or higher aliphatic polyol. The above k is preferably an integer of 3 to 10, more preferably an integer of 3 to 6.

The isocyanurate structure has one or two or more chemical formulas (2) in the molecule: The isocyanurate ring represented.

The isocyanurate structure may, for example, be a trimer obtained by a trimerization reaction of the above isocyanate, a pentamer obtained by a pentamerization reaction, or a heptameric obtained by a hemerization reaction. Body and so on.

Among them, the following chemical formula (3): The trimer represented is preferred.

The above diurea has the following chemical formula (4): The compound of the structure shown can be obtained by trimerating the hexamethylene diisocyanate under the conditions different from the case of obtaining the above isocyanurate structure.

As the above blocking agent, a compound having an active hydrogen is preferably used. The compound having an active hydrogen is preferably at least one selected from the group consisting of, for example, an alcohol, an anthracene, an indoleamine, an active methylene compound, and a pyrazole compound.

In this manner, the blocked isocyanate is obtained by reacting a polyisocyanate compound derived from hexamethylene diisocyanate with a blocking agent, wherein the blocking agent is an alcohol, an anthracene, an indoleamine, or an active stretcher. At least one selected from the group consisting of a base compound and a pyrazole compound is 1 of the preferred embodiment of the present invention.

Specific examples of the above-mentioned blocked isocyanate will be described later.

Further, the coating material of the present invention may further contain other components in addition to the above-mentioned curable functional group-containing fluoropolymer and the above-mentioned blocked isocyanate. These other components may be used alone or in combination of two or more.

Hereinafter, the coating material of the present invention will be described in more detail by way of specific examples.

<Fluoropolymer containing a curable functional group>

The monomer having a curable functional group may be exemplified below, but is not limited thereto. Further, one type or two or more types may be used.

(1-1) Hydroxyl-containing monomer:

The hydroxyl group-containing monomer may, for example, be 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether or 4-hydroxybutyl group. Vinyl ether, 4-hydroxy-2-methylbutyl vinyl ether, 5-hydroxyl Hydroxy-containing vinyl ethers such as pentyl vinyl ether and 6-hydroxyhexyl vinyl ether; hydroxyl groups such as 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, and glycerol monoallyl ether Allyl ethers and the like. Among these, a hydroxyvinyl ether is preferable, and 4-hydroxybutyl vinyl ether and 2-hydroxyethyl vinyl ether are particularly preferable in terms of polymerization reactivity and curability of a functional group.

The other hydroxyl group-containing monomer may, for example, be a hydroxyalkyl ester of a (meth) acrylate such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

(1-2) Carboxyl group-containing monomer:

The carboxyl group-containing monomer may, for example, be a general formula (5): (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; and n is 0 or 1) represents an unsaturated monocarboxylic acid or an unsaturated dicarboxylic acid. An unsaturated carboxylic acid such as an acid, a monoester or an acid anhydride thereof; or a general formula (6): (wherein R ⁶ and R ⁷ are the same or different straight or cyclic alkyl groups which are saturated or unsaturated; n is 0 or 1; m is 0 or 1) Body and so on.

Specific examples of the carboxyl group-containing monomer include acrylic acid and nail Acrylic acid, ethylene acetic acid, crotonic acid, cinnamic acid, 3-allyloxypropionic acid, 3-(2-allyloxyethoxycarbonyl)propionic acid, itaconic acid, itaconic acid monoester, horse Acid, maleic acid monoester, maleic anhydride, fumaric acid, fumaric acid monoester, vinyl phthalate, pyromellitic acid, and the like. Among them, crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, and 3-allyloxypropionic acid having low polymerizability alone are polymerizable alone. It is low and difficult to be a single polymer.

Specific examples of the carboxyl group-containing vinyl ether monomer represented by the above general formula (6) include, for example, 3-(2-allyloxyethoxycarbonyl)propionic acid and 3-(2-allyloxybutoxylate). One or two or more kinds of carbonylcarbonyl), 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 is excellent in stability or polymerization reactivity of the monomer.

(1-3) Amino group-containing monomer:

The amine group-containing monomer may, for example, be an amino vinyl ether represented by CH ₂ =CH-O-(CH ₂ ) _x -NH ₂ (x=0 to 10); CH ₂ =CH-O-CO(CH) ₂ ) allylamine represented by _x -NH ₂ (x = 1 to 10); others such as aminomethylstyrene, vinylamine, acrylamide, ethyleneacetamide, ethylenecarbendamide, and the like.

(1-4) Anthrone-based vinyl monomer:

The anthrone-based vinyl monomer may, for example, be 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 (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 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 trichloromethane or a partial hydrolyzate of such vinyl hydrides; trimethoxy decyl ethyl vinyl ether, triethoxy decyl ethyl vinyl ether, trimethoxy decyl butyl Vinyl ethers such as vinyl ether, methyl dimethoxy sulfonyl ethyl vinyl ether, trimethoxy decyl propyl vinyl ether, and triethoxy decyl propyl vinyl ether.

The fluoropolymer to which the curable functional group is introduced is exemplified as follows, in view of the polymerization unit constituting the polymer.

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

Specific examples include a copolymer of tetrafluoroethylene (TFE) alone or a copolymer of TFE and hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE), and the like, and Copolymers of other monomers which are copolymerized, and the like.

The other monomer which can be copolymerized may, for example, be vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutylate, vinyl pivalate, vinyl hexate, vinyl versatate or vinyl laurate. Ethyl esters, vinyl stearate, vinyl cyclohexyl carboxylate, vinyl benzoate, vinyl p-t-butyl benzoate, etc.; vinyl vinyl ether, ethyl vinyl ether, An alkyl vinyl ether such as butyl vinyl ether or cyclohexyl vinyl ether; a non-fluorinated olefin such as ethylene, propylene, n-butene or isobutylene; vinylidene fluoride (VdF) or chlorotrifluoroethylene (CTFE) ), a fluorine-based monomer such as vinyl fluoride (VF) or fluorovinyl ether, but is not limited thereto.

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

Specific examples of the perfluoroolefin-based polymer having a curable functional group include a copolymer of TFE/isobutylene/hydroxybutyl vinyl ether/other monomer, and a TFE/vinyl vinyl carbonate/hydroxybutyl vinyl group. a copolymer of an ether/other monomer, a copolymer of TFE/VdF/hydroxybutyl vinyl ether/other monomer, or the like, a copolymer of TFE/isobutylene/hydroxybutyl vinyl ether/other monomer, A copolymer of TFE/vinyl versatate/hydroxybutyl vinyl ether/other monomer or the like is preferred.

For the TFE-based coating composition for a coating, a ZEFFLE (registered trademark) GK series manufactured by Daikin Industries Co., Ltd., and the like can be exemplified.

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

Specific examples thereof include a copolymer of CTFE/hydroxybutyl vinyl ether/other monomer, and the like.

As a curable polymer composition for coatings of the CTFE system, LUMIFLON (registered trademark) manufactured by Asahi Glass Co., Ltd., FLUONATE (registered trademark) manufactured by DIC Co., Ltd., and CEFRAL COAT (manufactured by Central Glass Co., Ltd.) can be exemplified. Registered trademark), ZAFLON (registered trademark) of East Asia Synthetic Co., Ltd., etc.

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

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

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

Specific examples include, for example, CF ₃ CF ₂ (CF ₂ CF ₂ ) _n CH ₂ CH ₂ OCOCH=CH ₂ (n = a mixture of 3 and 4)/2-hydroxyethyl methacrylate / stearin Acrylate copolymer and the like.

The fluoroalkyl group-containing polymer may, for example, be Unidyne (registered trademark) manufactured by Daikin Industries Co., Ltd., or FTONE (registered trademark), or Zonyl (registered trademark) manufactured by Du Pont Co., Ltd., or the like.

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

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

In the coating material of the present invention, the content of the curable functional group-containing fluoropolymer is preferably from 20 to 95% by mass based on 100% by mass of the total amount of nonvolatiles in the coating material. More preferably 40 to 95% by mass.

<Block isocyanate>

When the polyisocyanate compound for the above-mentioned blocked isocyanate is an adduct of a hexamethylidene diisocyanate and a trivalent or higher aliphatic polyol, specific examples of the trivalent or higher aliphatic polyol include glycerin. , trimethylolpropane (TMP), 1,2,6-hexanetriol, trimethylolethane, 2,4-dihydroxy-3-hydroxymethylpentane, 1,1,1-parameter a trivalent alcohol such as (dihydroxymethyl)propane or 2,2-bis(hydroxymethyl)butanol-3; a tetravalent alcohol such as pentaerythritol or diglycerin; and 5 such as arabinol, ribitol or xylitol. A valent alcohol (pentaerythritol); a hexite or the like of sorbitol, mannitol, galactitol, and garlic alcohol. Among them, trimethylolpropane and pentaerythritol are preferred.

The above-mentioned adduct can be obtained by addition polymerization of a hexamethylene diisocyanate and an aliphatic polyol having a trivalent or higher value as described above.

Specific examples of the compound having an active hydrogen reaction with the above polyisocyanate compound include alcohols such as methanol, ethanol, n-propanol, isopropanol, and methoxypropanol; acetone oxime and 2-butyl Ketone oxime, cyclohexanone oxime Anthraquinones; oxime amines such as ε-caprolactam; active methyl group compounds such as methyl acetate, methyl malonate; 3-methylpyrazole, 3,5- One or two or more kinds of these may be used as the pyrazole compound such as dimethylpyrazole or 3,5-diethylpyrazole.

Among them, an active methyl group compound, an anthracene group, and an active methyl group compound are more preferable.

In the present invention, for example, Duranate (registered trademark) K6000 (made by Asahi Kasei Chemicals Co., Ltd., HDI active methyl group block isocyanate), Duranate TPA-B80E (made by Asahi Kasei Chemicals Co., Ltd.), Duranate MF-B60X (made by Asahi Kasei Chemicals Co., Ltd.), Duranate 17B-60PX (made by Asahi Kasei Chemicals Co., Ltd.), Coronate (registered trademark) 2507 (manufactured by Japan Polyurethane Co., Ltd.), Coronate 2513 (Japanese Polyurethane) Co., Ltd., Coronate 2515 (manufactured by Japan Polyurethane Co., Ltd.), Sumijuir (registered trademark) BL-3175 (manufactured by Sumitomo Bayer Co., Ltd.), Luxate HC1170 (manufactured by Oli. Chemicals Co., Ltd.), Luxate HC2170 (manufactured by Oli. Chemicals Co., Ltd.) and the like.

The content of the blocked isocyanate is 0.1 to 5 equivalents, preferably 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 curable functional group-containing fluoropolymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, fluorescent X-ray analysis, and neutralization titration depending on the type of the monomer.

In the present specification, the content of the curable functional group-containing fluoropolymer and the blocked isocyanate is based on the mass of the non-volatile matter of each solvent or the like.

The coating material of the present invention can be prepared by a usual method in the form of a solvent-based paint, an aqueous paint, a powder paint or the like. Among them, the form of the solvent-based paint is preferable in terms of the ease of film formation, the degree of hardenability, and the degree of dryness.

The solvent of the solvent-based coating material is preferably an organic solvent, and examples thereof include esters of ethyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, cellosolve acetate, and propylene glycol methyl ether acetate. a ketone such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone; a cyclic ether such as tetrahydrofuran or dioxane; N,N-dimethylformamide, N,N - anthranes such as dimethylacetamide; aromatic hydrocarbons such as xylene, toluene, and petroleum-soluble petroleum spirit; glycol ethers such as propylene glycol methyl ether and ethyl cellosolve; carbitol Diethylene glycol esters such as acid esters; n-pentane, n-hexane, n-heptane, n-octane, n-decane, n-decane, n-undecane, n-ten An aliphatic hydrocarbon such as dioxane or mineral oil; a mixed solvent of these or the like.

Among them, esters are preferred, and butyl acetate is more preferred.

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

In the coating of the present invention, various additives can be blended according to the characteristics required. Examples of the additive include a hardening accelerator, a hardening retarder, a pigment, a pigment dispersing agent, an antifoaming agent, a flat agent, and ultraviolet absorption. Agent, light stabilizer, tackifier, adhesion improver, matting agent, etc.

Examples of the curing accelerator include an organotin compound, an acidic phosphate ester, a reactant of an acidic phosphate ester and an amine, a saturated or unsaturated polycarboxylic acid or an anhydride thereof, an organic titanate compound, an amine compound, and an octyl acid. Lead and so on.

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

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

Specific examples of the pigment include inorganic pigments such as titanium oxide of a white pigment, calcium carbonate, or a black pigment, and a composite metal such as a Cu-Cr-Mn alloy; a phthalocyanine-based or quinophthalone-based or An organic pigment such as an azo system, etc., but not limited thereto.

The amount of the pigment added is preferably 0.1 to 200 parts by weight, preferably 0.1 to 160 parts by weight, per 100 parts by weight of the fluoropolymer containing the curable functional group.

The coating of the present invention preferably contains a UV absorber. The solar cell is used for the deterioration of the back sheet due to ultraviolet rays due to the use of the ultraviolet light during the long period of time. When the 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.

For the ultraviolet absorber, any of an organic system and an inorganic system can be used. UV absorber. In the organic system, for example, a UV absorber such as a salicylate type, a benzotriazole type, a benzophenone type or a cyanoacrylate type, or the like, and a filler type such as zinc oxide or cerium oxide in the inorganic system. An inorganic ultraviolet absorber or the like is preferred.

The ultraviolet absorber may be used singly or in combination of two or more kinds. The amount of the ultraviolet absorber is preferably 0.1 to 15% by mass based on 100% by mass of 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 if the amount is too large, 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 material of the present invention to a suitable substrate and curing it according to the application. The formation of the cured coating film of the substrate is carried out by applying the coating of the present invention to the substrate in accordance with the coating form.

The coating may be carried out in a temperature range of the usual conditions of the coating form, and may be cured and dried. In the case of a solvent-based coating, 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 material of the present invention is applied to the back sheet of a solar cell module, as a water-impermeable sheet, a material which is required to avoid high-temperature treatment like a Si-evaporated PET sheet can be used without any problem. After hardening and drying, it can be cured and maintained at 20~300 °C for 1 minute to 3 days.

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

The formation of the undercoat layer is carried out by a conventional method using a conventional primer for coating. For the primer coating, for example, epoxy resin, amine base An acid ester resin, an acrylic resin, an anthrone resin, a polyester resin, etc. are representative examples.

The film thickness of the cured coating film is preferably 5 μm or more, and is preferable from the viewpoint of good concealability, weather resistance, chemical resistance, and moisture resistance. It is preferably 7 μm or more, and more preferably 10 μm or more. When the upper limit is too thick, the weight reduction effect is not obtained, and it is preferably about 1000 μm and more preferably 100 μm. In terms of film thickness, it is particularly preferably 10 to 40 μm.

Compared with the conventional fluoropolymer coating containing a curable functional group, the coating material of the present invention is used as an interior material or building material for building materials, interior materials, automobiles, airplanes, ships, and electric trains. The paint for external use of the house can be directly coated on the coating of metal, concrete, plastic, etc., or under the coating of the primer, rust-proof paint, epoxy paint, acrylic paint, polyester resin paint, etc. It is also useful to apply a back sheet of a solar cell module which is suitable for use in a conventional fluoropolymer coating containing a curable functional group.

When the coating material of the present invention is used in the coating of a back sheet of a solar cell module, the coating film is formed on one side or both sides of a substrate such as a water-impermeable sheet.

The back sheet of the solar cell module having the water-impermeable sheet and the coating film formed by the coating material formed on at least one side of the water-impermeable sheet is also the first aspect of the invention.

The water-impermeable sheet is a layer which is designed to prevent moisture from permeating in a sealing material or a solar battery cell, and can be used as a material which does not substantially permeate water. However, in terms of weight, price, flexibility, etc., PET is widely used. Sheet, Si A PET sheet, a metal foil such as aluminum or stainless steel, or the like is vapor-deposited. Among them, PET flakes are commonly used. The thickness is usually about 50 to 250 μm. Among them, Si vapor-deposited PET sheets are commonly used in the case where moisture resistance is necessary. The thickness is usually about 10 to 20 μm.

Moreover, in order to improve the adhesiveness with the above-mentioned coating film, the conventional surface treatment can also be performed in the water-impermeable sheet. The surface treatment may, for example, be a corona discharge treatment, a plasma discharge treatment, a chemical conversion treatment, a metal foil, or a blast treatment.

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 surface of the water-impermeable sheet or on both surfaces.

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.

A preferred configuration of the solar cell module described above can be exemplified in Figures 1-3.

In the first structure shown in Fig. 1, the solar battery cell 1 is sealed by the sealing material layer 2, which is sandwiched by the surface layer 3 and the backing plate 4. The back sheet 4 is composed of a hard coat film 6 obtained by the water-impermeable sheet 5 and the paint 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 made of ethylene/vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), fluorenone resin, epoxy tree. It is composed of fat, acrylic resin, and the like.

A glass plate can be usually used for the surface layer 3, 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 the cured coating film 6 is formed on both surfaces of the water-impermeable sheet 5.

This second structure has the advantages 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.

In the back sheet of the three-layer structure, the hardened coating film obtained from the coating material of the present invention may be formed on one side of the water-impermeable sheet, and the hardening coating of the fluorine-containing polymer coating not containing the curable functional group may be formed on the other side. A back sheet of a three-layer structure formed of a coating film (a flaky sheet or a coating film) of a coating film, a fluoropolymer sheet, a polyester sheet or a polyester coating.

The third structure shown in Fig. 3 is such that the hard coating film 6 obtained from the coating material of the present invention is formed on the side of the sealing material layer 2 of the water-impermeable sheet 5, and another coating film 7 is formed on the side opposite 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 containing no curable functional group, or 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 conventional surface treatment can be performed on the coating film. The surface treatment may, for example, be a corona discharge treatment, a plasma discharge treatment, a chemical conversion treatment, a spray treatment or the like.

The cured coating film of the fluoropolymer coating material containing no curable functional group, for example, in PVdF described in JP-A-2004-214342 a hardened coating film of a coating with a tetraalkoxydecane or a partial hydrolyzate thereof, a cured coating film of a VdF/TFE/CTFE copolymer and a mixed coating containing an alkoxydecane unit acrylic resin, and a VdF/TFE/HFP copolymer and A cured coating film of a mixed coating containing a hydroxy acrylic resin, a cured coating film of a coating of an amine decane coupling agent in a VdF/HFP copolymer, and the like. The film thickness is usually from 5 to 300 μm from the viewpoint of good concealability, weather resistance, chemical resistance, and moisture resistance. It is preferably 10 to 100 μm, more preferably 10 to 50 μm. In this case, an undercoat layer or the like may also be provided.

The fluoropolymer sheet may, for example, be a PVdF sheet or a PVF sheet, a PCTFE sheet, a TFE/HFP/ethylene copolymer sheet, a TFE/HFP copolymer (FEP) sheet, a TFE/PAVE copolymer (PFA) sheet, or ethylene. Fluoropolymer sheet used in the current backsheet, such as /TFE copolymer (ETFE) sheet, ethylene/CTFE copolymer (ECTFE) sheet. The film thickness is usually from 5 to 300 μm from the viewpoint of good weather resistance. It is preferably 10 to 100 μm, more preferably 10 to 50 μm.

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

In the above-mentioned polyester coating, for example, a saturated polyester resin such as a polyvalent carboxylic acid or a polyhydric alcohol may be used, and an unsaturated polyester resin such as fumaric acid or the like may be used. Roll coating, curtain coating A coating method such as cloth, spray coating, die casting, or the like is formed. The film thickness is preferably at a point where the concealability, weather resistance, chemical resistance, and moisture resistance at 5 to 300 μm are good. It is preferably 10 to 100 μm, more preferably 10 to 50 μm. In this case, an undercoat layer or the like may also be provided.

The coating material of the present invention is composed of the above-described composition, and is significantly improved in service life as compared with the conventional fluoropolymer coating containing a curable functional group.

Then, the coating film obtained by such a coating is also extremely useful for coating as a back sheet of a solar cell module.

[Best Mode for Carrying Out the Invention]

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

Modulation example 1

A curable TFE-based copolymer (ZEFFLEGK 570, manufactured by Daikin Industries Co., Ltd., solid content: 65 mass%, hydroxyl group: 60 mgKOH/g, solvent: butyl acetate), 223.2 parts by mass, and titanium oxide as a white pigment (Du Pont) 250 parts by mass of the company-made Ti-Pure R960 and 126.8 parts by mass of butyl acetate were mixed and prepared under stirring, and then placed in 780 parts by mass of glass beads having a diameter of 1.2 mm, and dispersed in a pigment disperser at 1500 rpm for 1 hour. Thereafter, the glass beads were filtered through a #80 mesh sieve, and a solution of the curable TFE-based copolymer (ZEFFLEGK570) was added in a solution of 269.2 parts by mass. White paint.

In this white paint, 100 parts by mass of a curing agent (Duranate K6000, manufactured by Asahi Kasei Chemicals Co., Ltd., HDI active methyl ester block isocyanate) 20.8 parts by mass (relative to the curable functional group 1 in the curable TFE copolymer) Equivalent to 1.0 equivalents, the coating 1 was prepared.

Example 1

With respect to the coating material 1 obtained in Preparation Example 1, the lifespan was measured by the method shown below. The results are shown in Table 1.

(Period of use)

It is carried out in accordance with JIS K5600-2-6. The curable coating material prepared in each of the preparation examples was placed in a container made of polypropylene having a volume of 100 ml, and sealed, and then stored at 25° C., and then the viscosity was measured in a timely manner, and the time until the viscosity reached twice the initial period was used.

Comparative example 1

As a curing agent, Coonate HX (manufactured by Japanese Polyurethane Co., Ltd., isocyanurate structure of hexamethylene diisocyanate, NCO content: 21.1%) was used in an amount of 14.8 parts by mass (relative to the curable TFE copolymerization). Comparative Comparative Coating Material 1 was prepared in the same manner as in Preparation Example 1 except that the amount of the curable functional group in the product was equivalent to 1.0 equivalent, and the use period was examined in the same manner as in Example 1. The results are shown in Table 1.

As a result of Example 1 and Comparative Example 1, the coating material of Example 1 using a blocked isocyanate of hexamethylene diisocyanate as a curing agent was used as compared with the coating material of Comparative Example 1 using a conventional curing agent. The period is greatly extended. Therefore, it has been confirmed that there is a technical significance in the constitution of the present invention.

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 (6)

A coating comprising a fluoropolymer containing a curable functional group and a blocked isocyanate based on hexamethylene diisocyanate, wherein the fluoropolymer containing a curable functional group contains a polymerization based on a fluoromonomer And a polymerization unit of at least one of the hardenable functional group-containing monomers selected from the group consisting of a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amine group-containing monomer, and an anthranone-based vinyl monomer; The fluorine-containing monomer is at least one selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, and vinylidene fluoride, and the blocked isocyanate is a polyisocyanate compound derived from hexamethylene diisocyanate. The blocker is obtained by a reaction of a segmentation agent, and the blocker is at least one selected from the group consisting of alcohols, anthraquinones, indoleamines, active methylene compounds, and pyrazole compounds. The paint according to claim 1, wherein the paint further contains a pigment. The coating according to claim 1 or 2, further comprising a UV absorber. A coating film obtained by the coating of claim 1, 2 or 3. A back sheet of a solar cell module, characterized by having a water-impermeable sheet and a coating film formed of the coating material of claim 1, 2 or 3 formed on at least one side of the water-impermeable sheet. A solar cell module characterized by having a water-impermeable sheet, a coating film formed of the coating material of claim 1, 2 or 3 formed on at least one side of the water-impermeable sheet, and on the coating film A layer of sealing material formed.