JP5710897B2 - Reflective sheet having a reflective coating of a curable resin composition - Google Patents

Description

  The present invention relates to a reflective sheet having a cured product of a curable resin composition as a reflective film, and particularly to a reflective sheet that can be used as a back sheet of a solar cell module.

Carbon dioxide increases and global warming due to the generated during fossil energy sources combustion, NO _X, measures for environmental destruction such as air pollution due to the release of SO _X has become an urgent task. Therefore, in recent years, solar cells that can directly obtain electricity from sunlight have attracted attention as a new energy source having no environmental load. A solar cell is a combination of a plurality of photovoltaic elements, and has a structure in which several to several tens of photovoltaic elements are wired in series and in parallel. Moreover, since a solar cell is installed in a natural environment for a long period of time, it is used as a solar cell module packaged with a cover material in order to protect the photovoltaic element.

  Specifically, the solar cell module is composed of an upper transparent material made of glass, transparent plastic, and the like, and a sealing layer made of a thermoplastic resin such as an ethylene vinyl acetate copolymer, in order from the side on which the sunlight hits. A plurality of photovoltaic cells in which photovoltaic elements are wired in series and in parallel, a sealing layer (a layer similar to the sealing layer), and a solar battery backsheet are laminated.

  The back sheet of the solar cell is installed as a protective member on the back surface side, and generally, a material excellent in impact resistance is used. In addition, the back sheet is required to have a white color tone having high reflectivity in order to effectively use the incident light to the solar cell module and increase the power conversion efficiency. On the other hand, since the solar cell module is installed in the natural environment for a long time as described above, the solar cell backsheet has good adhesion to the sealing layer and has various properties such as weather resistance and moisture resistance. There is a demand for excellence. In view of this, a solar battery back sheet having an adhesive coating layer made of a polyacrylic acid resin colored with a white pigment mainly composed of titanium oxide is proposed on the innermost surface to be bonded to the sealing layer constituting the solar battery module. (Patent Document 1).

  However, in the above conventional solar cell backsheet, the solar cell module is exposed to a harsh natural environment, so that the light reflectivity gradually deteriorates due to the influence of solar radiation, solar heat, moisture, etc. over a long period of time. There was a problem of going.

  On the other hand, when using a photocurable resin composition as a white paint for a solar battery backsheet, discoloration may occur when the coating is heated and cured, resulting in a decrease in light reflectance. It was. Therefore, as a photo-curable resin composition for suppressing discoloration and reflectivity decrease due to ultraviolet rays or heat, it is obtained from (A) an alicyclic skeleton epoxy resin and has at least two ethylenically unsaturated bonds in one molecule. Contains an active energy ray curable resin, (B) a thiol compound, (C) a photopolymerization initiator, (D) a diluent, (E) a rutile titanium oxide, and (F) an epoxy thermosetting compound. A photosensitive resin composition is known (Patent Document 2).

  However, the photosensitive resin composition of Patent Document 2 still has a problem that the surface of the coating film changes to yellow and the reflectance decreases. In addition, the solar cell back sheet is required to have low warpage from the viewpoint of improving power conversion efficiency by being in close contact with the back surface of the solar cell module, and more flexible from the viewpoint of preventing damage during transportation and installation work. From the point of long-term installation in the natural environment, it is also required to have flame retardancy.

JP 2010-109240 A JP2008-211036

  In view of the above circumstances, an object of the present invention is to provide a reflective sheet having a reflective film having excellent properties such as weather resistance, heat resistance and light resistance, and having flexibility, low warpage, and flame retardancy. Objective.

  A first aspect of the present invention is a reflective sheet having a reflective coating formed of a curable resin composition, wherein the curable resin composition is (A-1) general formula (I)

(Wherein R ¹ represents a hydrogen atom or a methyl group) and a general formula (II)

(Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, and t-butyl. A group, an adamantyl group or a trifluoromethyl group, and m is an integer of 0 or 1-3) and / or the general formula (III)

(Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, and t-butyl. A group, an adamantyl group or a trifluoromethyl group, A ¹ represents a C 2-10 alkylene group or a C 3-10 hydroxyalkylene group containing a linear or cyclic skeleton, and m is 0 or 1-3. An integer, p is an integer of 1 to 5), or a copolymer resin obtained by reacting the compound represented by (A-2) general formula (I)

(Wherein R ¹ represents a hydrogen atom or a methyl group) and a general formula (II)

(Wherein R ¹ R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, t A butyl group, an adamantyl group or a trifluoromethyl group, and m is 0 or an integer of 1 to 3) and / or the general formula (III)

(Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, and t-butyl. A group, an adamantyl group or a trifluoromethyl group, A ¹ represents a C 2-10 alkylene group or a C 3-10 hydroxyalkylene group containing a linear or cyclic skeleton, and m is 0 or 1-3. An integer, p is an integer of 1 to 5), and a copolymer obtained by adding a compound having an oxirane ring and an ethylenically unsaturated bond to a part of the carboxyl group of the copolymer obtained by reacting the compound represented by A reflective sheet comprising a polymer resin, (B) a curing agent, (C) a diluent, and (D) an inorganic white pigment.

  A cured product of the curable resin composition described above is used for the reflective film of the reflective sheet. The copolymer resin (A-1) blended in the curable resin composition is composed of the compound represented by the general formula (I), the compound represented by the general formula (II), and / Further, it is a copolymer with a compound represented by the above general formula (III), and is a carboxyl group-containing copolymer resin having an aromatic ring. Further, the copolymer resin (A-2) blended in the curable resin composition is obtained by adding a compound having an oxirane ring and an ethylenically unsaturated bond to the copolymer (A-1). And a carboxyl group-containing copolymer resin having an aromatic ring.

  In a second aspect of the present invention, the compound having an oxirane ring and an ethylenically unsaturated bond is represented by the general formula (IV):

(Wherein R ¹ represents a hydrogen atom or a methyl group, A ² represents an alkylene group having 2 to 10 carbon atoms, and q is 0 or an integer of 1 to 5). This is a characteristic reflection sheet.

  According to a third aspect of the present invention, the (A-1) copolymer resin and the (A-2) copolymer resin have 5 to 40% by mass of an aromatic hydrocarbon skeleton. It is. That is, (A-1) copolymer resin and (A-2) copolymer resin each contain 5 to 40% by mass of an aromatic hydrocarbon skeleton. 4th aspect of this invention is an acid value of (A-1) copolymer resin, and the acid value of (A-2) copolymer resin is 30-150 mgKOH / g, It is a reflection sheet characterized by the above-mentioned. .

  In a fifth aspect of the present invention, the (B) curing agent contains at least one selected from the group consisting of a compound having two or more epoxy groups in one molecule, melamine, and a melamine derivative. Reflective sheet, sixth aspect of the present invention is the reflective sheet, wherein the diluent (C) contains a compound having one or more ethylenically unsaturated groups in one molecule. In the reflective sheet according to the present invention, the diluent (C) is a compound having two or more (meth) acrylic groups and having a (meth) acrylic equivalent of 200 g / eq or more, the present invention The eighth aspect of the present invention is that the (D) inorganic white pigment is a rutile type titanium oxide, and the ninth aspect of the present invention further includes (E) a photopolymerization initiator. A reflecting sheet, characterized in that the tenth aspect of the present invention Further includes (F) a reflective sheet comprising a phosphorus-based flame retardant, and the eleventh aspect of the present invention is a reflective sheet further comprising (G) a metal hydroxide. is there.

  A twelfth aspect of the present invention is a solar cell module including the reflection sheet.

  According to the first and second aspects of the present invention, by using (meth) acrylic acid as a constituent of a copolymer and specifying the carboxyl group of the copolymer resin as a structure derived from (meth) acrylic acid, Since it is possible to suppress a decrease in the reflectance of the reflective coating over time and light, a reflective sheet having a reflective coating excellent in heat resistance, light resistance and weather resistance can be obtained. Further, as shown in the general formula (II) and the general formula (III), a compound having no hydrogen atom at the side chain α-position of the aromatic hydrocarbon skeleton is a constituent element of the copolymer resin after polymerization. That is, a compound having no hydrogen atom at the α-position of the side chain relative to the aromatic hydrocarbon skeleton or a compound in which a hydrogen atom at the α-position relative to the aromatic hydrocarbon skeleton is present in the main chain Therefore, discoloration of the reflective film can be suppressed.

  According to the 3rd aspect of this invention, since (A-1) copolymer resin and (A-2) copolymer resin have 5-40 mass% aromatic-hydrocarbon frame | skeleton, it is heat resistant. A reflective sheet having a reflective film excellent in flame retardancy can be obtained. In addition, (C) having compatibility with diluents, etc., it is excellent in alkali developability when forming a pattern of a reflective film, and also excellent in flexibility from good photocurability and thermosetting. A reflective sheet having a reflective coating can be obtained. Therefore, it is possible to prevent the reflection sheet from being damaged during transportation and installation work.

  Moreover, in this invention, since the reflective sheet which has low curvature property can be obtained, when a reflective sheet is used as a back sheet | seat of a solar cell, for example, adhesiveness with a solar cell module is ensured.

  Next, the curable resin composition used for the reflective film of the reflective sheet of the present invention will be described. The curable resin composition used for forming the reflective film of the reflective sheet is (A-1) a compound represented by the above general formula (I), a compound represented by the above general formula (II) and / or the above general formula. A copolymer resin obtained by reacting a compound represented by the formula (III), or (A-2) a compound represented by the above general formula (I) and a compound represented by the above general formula (II). And / or a copolymer resin obtained by adding a compound having an oxirane ring and an ethylenically unsaturated bond to a part of the carboxyl group of a copolymer obtained by reacting the compound represented by the general formula (III), It contains (B) a curing agent, (C) a diluent, and (D) an inorganic white pigment.

(A-1), (A-2): The copolymer resin of the copolymer resin (A-1) is represented by the acrylic acid or methacrylic acid represented by the general formula (I) and the general formula (II). And an ethylenically unsaturated monomer having an aromatic ring and / or (meth) acrylate having an aromatic ring represented by the general formula (III). The copolymer resin (A-2) is a copolymer of the copolymer (A-1) obtained by copolymerizing the general formula (I) with the general formula (II) and / or the general formula (III). It is obtained by adding a compound having an oxirane ring and an ethylenically unsaturated bond to a part of the carboxyl group.

  Examples of the ethylenically unsaturated monomer having an aromatic ring represented by the general formula (II) include styrene, α-methylstyrene, p-methoxystyrene, mt-butoxystyrene, pt-butoxystyrene, and p- (1 -Ethoxyethoxy) styrene, p-fluorostyrene and the like. These compounds may be used alone or in combination of two or more.

  Examples of the (meth) acrylate having an aromatic ring represented by the general formula (III) include phenoxy polyethylene glycol (meth) such as phenoxyethyl (meth) acrylate and 2- (2-phenoxyethoxy) ethyl (meth) acrylate. 4-, such as phenoxypolypropylene glycol (meth) acrylate such as acrylate, phenoxypropyl (meth) acrylate and 2-phenoxypropyl (meth) acrylate, phenylglycidyl ether (meth) acrylate, 4-α-cumylphenoxyethyl (meth) acrylate, etc. α-cumylphenoxypolyethylene glycol (meth) acrylate and 2-phenylphenoxypolyethylene glycol (meth) acrylate such as 2-phenylphenoxyethyl (meth) acrylate Can be mentioned. These compounds may be used alone or in combination of two or more.

  In addition, in order to obtain the copolymer resin of (A-1) and (A-2), it is represented by the ethylenically unsaturated monomer having an aromatic ring represented by the general formula (II) or the general formula (III). Any one of (meth) acrylates having an aromatic ring may be used, or both may be mixed and used.

  The compound having an oxirane ring and an ethylenically unsaturated bond is not particularly limited as long as it is a compound having an oxirane ring and an ethylenically unsaturated bond, and examples thereof include compounds represented by the above general formula (IV), More specifically, glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether, hydroxyalkyl (meth) acrylate glycidyl ether, β-methylglycidyl (meth) acrylate, (3,4-epoxycyclohexyl) methyl Examples thereof include epoxy cyclohexyl derivatives of (meth) acrylic acid such as (meth) acrylate, alicyclic epoxy derivatives of (meth) acrylate, and the like. These compounds may be used alone or in combination of two or more.

  In addition, if necessary, an ethylenically unsaturated monomer having an aromatic ring represented by the general formula (II), a (meth) acrylate having an aromatic ring represented by the general formula (III), and an aromatic ring also having a carboxyl group In addition, an ethylenically unsaturated monomer that does not have the above may be added to be copolymerized with acrylic acid or methacrylic acid represented by formula (I). Examples of ethylenically unsaturated monomers having neither an aromatic ring nor a carboxyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl acrylate, and n-butyl (meth). Acrylate, i-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, di Cyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate and 2-ethyl-2-adamantyl ( Meta) Acu Alkyl (meth) acrylates having a straight chain, branched or alicyclic skeleton such as rate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl Hydroxy mono (meth) acrylates such as (meth) acrylate, 4-hydroxybutyl (meth) acrylate, cyclohexanedimethanol mono (meth) acrylate and nonanediol mono (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, cyclic trimethylol Cyclic ether skeleton-containing (meth) acrylates such as propane formal (meth) acrylate and alkoxylated tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate cap Lactone adducts and hydroxymono (meth) acrylate / caprolactone adducts such as 2-hydroxypropyl (meth) acrylate / caprolactone adducts, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polypropylene glycol mono (meta) ) Acrylate, poly (ethylene glycol / propylene glycol) mono (meth) acrylate, poly (ethylene glycol / tetramethylene glycol) mono (meth) acrylate and poly (propylene glycol / tetramethylene glycol) mono (meth) acrylate Glycol-modified hydroxy mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, methoxypolypropylene Alkyl-terminated polyalkylene glycol mono (meth) acrylates such as glycol mono (meth) acrylate and ethoxypolyethylene glycol mono (meth) acrylate, 2,2,2-trifluoromethyl (meth) acrylate, 2- (perfluorobutyl) ethyl Fluorine-containing (meth) acrylates such as (meth) acrylate, 3- (perfluorobutyl) -2-hydroxypropyl (meth) acrylate and 2- (perfluorohexyl) ethyl (meth) acrylate, N-cyclohexylmaleimide and N- Examples include (meth) acrylate-containing (meth) acrylates such as (meth) acryloyloxyethyl hexahydrophthalimide, and (meth) acryl silicone compounds such as mono (meth) acrylates having a dimethylsiloxane skeleton. It can be.

  About each content of the aromatic hydrocarbon frame | skeleton of above-mentioned (A-1) copolymer resin and (A-2) copolymer resin, the lower limit is flame retardance and compatibility with (C) diluent etc. From this point, 5 mass% is preferable, and 10 mass% is particularly preferable. Moreover, the upper limit is preferably 40% by mass, particularly preferably 30% by mass, from the viewpoint of the flexibility of the cured coating film, that is, the reflective film.

  The (A-1) copolymer resin and the (A-2) copolymer resin can be synthesized by a known solution polymerization method. The solvent used is not particularly limited as long as it is inert to radical polymerization. Examples thereof include ethylene glycol monoalkyl ether acetates such as ethyl acetate, isopropyl acetate, cellosolve acetate and butyl cellosolve acetate; diethylene glycol monoalkyl ether acetates such as diethylene glycol monomethyl ether acetate, carbitol acetate and butyl carbitol acetate; propylene glycol Acetic esters such as monoalkyl ether acetates and dipropylene glycol monoalkyl ether acetates; Diethylene glycol dialkyl ethers, diethylene glycol dialkyl ethers such as methyl carbitol, ethyl carbitol, and butyl carbitol; Triethylene glycol dialkyl ethers; Propylene glycol dialkyl ether Diether ethers such as 1,4-dioxane and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; hydrocarbons such as benzene, toluene, xylene, octane and decane; petroleum Examples include petroleum solvents such as ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha; lactic acid esters such as methyl lactate, ethyl lactate, and butyl lactate; dimethylformamide, N-methylpyrrolidone, and the like. These solvents may be used alone or in combination of two or more. The usage-amount of a solvent is 30-1000 mass parts with respect to 100 mass parts of copolymer resins, Preferably it is 50-800 mass parts.

  The radical polymerization initiator used in the solution polymerization method is not particularly limited, and for example, an organic peroxide or an azo compound can be used. Specific examples include benzoyl peroxide, dicumyl peroxide, diisopropyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, t-hexyl peroxybenzoate, t-butylperoxy-2-ethylhexa Noate, t-hexylperoxy-2-ethylhexanoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-bis ( t-butylperoxy) hexyl-3,3-isopropyl hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, dicumyl hydroperoxide, acetyl peroxide, bis (4-t-butylcyclohexyl) peroxy Dicarbonate, diisopropyl par Xidicarbonate, isobutyl peroxide, 3,3,5-trimethylhexanoyl peroxide, lauryl peroxide, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (T-Hexylperoxy) 3,3,5-trimethylcyclohexane, azobisisobutyronitrile, azobiscarbonamide and the like can be used. A radical polymerization initiator having an appropriate half-life is appropriately selected according to the polymerization temperature. The usage-amount of a radical polymerization initiator is 0.5-20 mass parts with respect to a total of 100 mass parts of a radically polymerizable unsaturated compound, Preferably it is 1-10 mass parts.

  In the polymerization method, the unsaturated monomer and the radical polymerization initiator may be added dropwise to a heated solvent, followed by stirring. The unsaturated monomer and the radical polymerization initiator are dissolved in the solvent, and the temperature is increased while stirring. May be performed. Moreover, you may add an unsaturated monomer dropwise while adding a radical polymerization initiator in a solvent and heating up.

  By subjecting a part of the carboxyl group in the copolymer resin (A-1) obtained by the above polymerization method to an addition reaction with a compound having an oxirane ring and an ethylenically unsaturated bond, the copolymer (A-2) can be reacted. A polymerized resin can be obtained. About the addition amount of the compound which has an oxirane ring and an ethylenically unsaturated bond with respect to 1 equivalent of carboxyl groups in the copolymer resin of (A-1), the lower limit is 0.1 equivalent from the point which ensures sufficient photosensitivity. And preferably 0.2 equivalents. In addition, the upper limit is 0.8 equivalents, preferably 0.6 equivalents, from the viewpoint of preventing the amount of carboxyl groups from becoming too small when the pattern of the reflective film is formed, resulting in insufficient developability. It is.

  The catalyst used for the reaction between the carboxyl group in the copolymer resin (A-1) and the compound having an oxirane ring and an ethylenically unsaturated bond is, for example, triphenylphosphine, lithium naphthenate, zirconium naphthenate. , Chromium naphthenate, chromium acetylacetonate, chromium chloride and the like. Moreover, methoxyhydroquinone etc. can be mentioned as a polymerization inhibitor. The reaction can be carried out by a known method, for example, a compound having an oxirane ring and an ethylenically unsaturated bond after setting the copolymer resin (A-1) in the solvent obtained by the polymerization reaction to a predetermined temperature. , The catalyst and the polymerization inhibitor are mixed and stirred. At this time, the usage-amount of a catalyst is 0.01-1 mass% with respect to the sum total of the compound which has (A-1) copolymer resin, an oxirane ring, and an ethylenically unsaturated bond. The usage-amount of a polymerization inhibitor is 0.01-1 mass% with respect to the sum total of the compound which has (A-1) copolymer resin, an oxirane ring, and an ethylenically unsaturated bond. Moreover, reaction temperature is 60-150 degreeC, and reaction time is 3 to 60 hours.

  (A-1) About the weight average molecular weight of copolymer resin, the lower limit is 3000 from the point of the toughness of a reflecting film which is a cured coating film, and the touch-drying property, Preferably it is 5000. On the other hand, the upper limit is 200000, preferably 50000, from the viewpoint of compatibility with (C) diluent and the like and alkali developability. Moreover, (A-2) About the weight average molecular weight of copolymer resin, the lower limit is 3000 from the point of the toughness of a reflecting film which is a cured coating film, and finger-drying property, Preferably it is 5000. On the other hand, the upper limit is 200000, preferably 50000, from the viewpoint of compatibility with (C) diluent and the like and alkali developability.

  The acid values of the obtained (A-1) copolymer resin and (A-2) copolymer resin are preferably in the range of 30 to 150 mgKOH / g, respectively. This is because when the acid value is less than 30 mg KOH / g, the curability with the (B) curing agent component is lowered, and when it exceeds 150 mg KOH / g, the weather resistance of the reflective film is inferior.

(B) Curing agent The curing agent is for increasing the crosslink density of the cured coating film to obtain a sufficient reflective coating, and examples thereof include an epoxy resin. Examples of the epoxy resin include bisphenol A type epoxy resin, novolak type epoxy resin (phenol novolak type epoxy resin, o-cresol novolak type epoxy resin, p-tert-butylphenol novolak type, etc.), bisphenol F and bisphenol S with epichlorohydrin. Bisphenol F type, bisphenol S type epoxy resin, bisphenol E type epoxy resin, 2,5-di-tert-butylhydroquinone type epoxy resin, biphenyl type epoxy resin, cyclohexene oxide group, tricyclodecane oxide obtained by reaction Hydrogenated epoxy resins such as cycloaliphatic epoxy resins having thiol groups, cyclopentene oxide groups, nuclear hydrogenated bisphenol A type epoxy resins, nuclear hydrogenated biphenyl type epoxy resins, tris 2,3-epoxypropyl) isocyanurate, triglycidyltris (2-hydroxyethyl) isocyanurate and the like triglycidyl isocyanurate having a diazine ring, dicyclopentadiene type epoxy resin, adamantane type epoxy resin, diglycidyl phthalic anhydride ester And ester type epoxy resins such as diglycidyl anhydride of hexahydrophthalic anhydride, melamine, methylated methylol melamine, butylated methylol melamine, imidazole, dicyandiamide and the like. These compounds may be used alone or in combination of two or more. The usage-amount of a hardening | curing agent is 10-100 mass parts with respect to 100 mass parts of copolymer resins from the point which obtains a sufficient coating film after hardening, and 20-50 mass parts is preferable.

(C) Diluent The diluent is, for example, a photopolymerizable monomer, and is used to obtain a reflective coating having sufficient acid resistance, heat resistance, alkali resistance, etc., by sufficiently photocuring the curable resin. Examples of the photopolymerizable monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Dipentaerythritol hexaacrylate, bisphenol A type EO modified di (meth) acrylate, bisphenol A type PO modified di (meth) acrylate, caprolactone modified dipentaerythritol hexaacrylate, EO modified dipentaerythritol hexaacrylate, for example (meth) acrylic group And a urethane-based acrylic compound obtained by reacting a compound having at least one hydroxy group with a compound having at least one isocyanate group. The usage-amount of a diluent is 2.0-150 mass parts with respect to 100 mass parts of copolymer resins, and 10-80 mass parts is preferable. In the case of a diluent having two or more (meth) acryl groups, the (meth) acryl equivalent is preferably 200 g / eq or more, particularly preferably 300 g / eg or more from the viewpoint of flexibility and low warpage. In addition, the (meth) acryl equivalent in this specification means the molecular weight per (meth) acryloyl group.

(D) Inorganic white pigment The inorganic white pigment is for whitening the cured coating film, and examples thereof include anatase type titanium oxide and rutile type titanium oxide. Anatase-type titanium oxide has a higher whiteness than rutile-type titanium oxide, but has photocatalytic activity and may cause discoloration of the resin in the curable resin composition. On the other hand, rutile titanium oxide is preferable in that it has almost no photocatalytic activity and can prevent discoloration of the reflective film. The average particle size of the rutile-type titanium oxide particles is not particularly limited, but is usually 0.01 to 1 μm. Further, the surface treating agent for rutile type titanium oxide particles is not particularly limited. Examples of rutile titanium oxide include “TR-600”, “TR-700”, “TR-750”, “TR-840” manufactured by Fuji Titanium Industry Co., Ltd., and “R-550” manufactured by Ishihara Sangyo Co., Ltd. ”,“ R-580 ”,“ R-630 ”,“ R-820 ”,“ CR-50 ”,“ CR-60 ”,“ CR-90 ”,“ CR-93 ”, manufactured by Titanium Industry Co., Ltd. “KR-270”, “KR-310”, “KR-380”, “JR-1000” manufactured by Teika Co., Ltd., and the like can be used. The usage-amount of a rutile type titanium oxide is 30-800 mass parts with respect to 100 mass parts of copolymer resins, Preferably it is 50-500 mass parts.

  In the curable resin composition used for forming the reflective film of the reflective sheet of the present invention, the following components can be blended as required in addition to the above components.

(E) Photopolymerization initiator The photopolymerization initiator is not particularly limited as long as it is generally used. For example, oxime initiator, benzoin, acetophenone, 2-hydroxy-2-methyl-1-phenyl Propan-1-one, 1-hydroxycyclohexyl phenyl ketone, benzophenone, and the like. The usage-amount of a photoinitiator is 5-20 mass parts with respect to 100 mass parts of copolymer resins, and 8-15 mass parts is preferable.

(F) Phosphorus-based flame retardant Phosphorus-based flame retardant is for imparting flame retardancy to the curable resin composition, for example, tris (chloroethyl) phosphate, tris (2,3-dichloropropyl) Phosphate, tris (2-chloropropyl) phosphate, tris (2,3-bromopropyl) phosphate, tris (bromochloropropyl) phosphate, 2,3-dibromopropyl-2,3-chloropropyl phosphate, tris (tribromophenyl) ) Halogen-containing phosphates such as phosphate, tris (dibromophenyl) phosphate, tris (tribromoneopentyl) phosphate; trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, etc. Non-halogen aliphatic phosphate esters of: triphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, tricresyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, tris (isopropylphenyl) phosphate, isopropylphenyl diphenyl phosphate , Non-halogen aromatic phosphates such as diisopropylphenylphenyl phosphate, tris (trimethylphenyl) phosphate, tris (t-butylphenyl) phosphate, hydroxyphenyldiphenyl phosphate, octyldiphenyl phosphate; aluminum trisdiethylphosphinate, trismethylethylphosphine Aluminum oxide, aluminum trisdiphenylphosphinate Zinc, bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanyl bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, bisdiphenylphosphine Metal salts of phosphinic acid such as titanyl acid, titanium tetrakisdiphenylphosphinate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter HCA), addition reaction product of HCA and acrylate , HCA and epoxy resin addition reaction products, HCA and hydroquinone addition reaction products such as HCA-modified compounds, diphenylvinylphosphine oxide, triphenylphosphine oxide, trialkyl Examples thereof include phosphine oxide compounds such as phosphine oxide and tris (hydroxyalkyl) phosphine oxide. Of these, non-halogen phosphates, metal salts of phosphinic acid, HCA-modified compounds, and phosphine oxide compounds are preferred from the viewpoint of reducing environmental burden. In small amounts, not only flame retardancy but also bleed out resistance The metal salt of phosphinic acid is particularly preferable from the viewpoint of excellent properties and discoloration resistance. The amount of the phosphorus-based flame retardant used is 3 to 20 parts by mass with respect to 100 parts by mass of the copolymer resin, from the viewpoint of reliably suppressing a decrease in the mechanical strength of the reflective film while ensuring sufficient flame retardancy. 4-15 mass parts is preferable.

  A metal hydroxide is mix | blended as a flame retardant adjuvant, for example, aluminum hydroxide etc. can be mentioned. The usage-amount is 1-100 mass parts with respect to 100 mass parts of copolymer resins.

  In the present invention, various additional components such as an antifoaming agent, a dispersant, an extender pigment, an inorganic ion catcher, an organic solvent, and the like can be appropriately blended as necessary. A well-known thing can be used for an antifoamer, for example, a silicone type, a hydrocarbon type, an acrylic type etc. can be mentioned. Examples of the dispersant include silane-based, titanate-based, and alumina-based coupling agents. The extender is for increasing the physical strength of the coated reflective film, and examples thereof include silica, barium sulfate, alumina, aluminum hydroxide, talc, and mica. Examples of inorganic ion catchers include zirconium phosphate compounds.

  The organic solvent is for adjusting the viscosity and drying property of the curable resin composition, for example, ketones such as methyl ethyl ketone and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methanol, isopropanol, and cyclohexanol. Alcohols such as cyclohexane and methylcyclohexane, petroleum solvents such as petroleum ether and petroleum naphtha, cellosolves such as cellosolve and butylcellosolve, carbitols such as carbitol and butylcarbitol, acetic acid Examples thereof include acetates such as ethyl, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, and butyl carbitol acetate.

  The method for producing the curable resin composition used in the above-described reflection sheet of the present invention is not limited to a specific method. It can be produced by mixing and dispersing with a roll.

  Next, an example of a method for producing the reflective sheet of the present invention by applying the above-described curable resin composition to the surface of the sheet-like base film will be described. When the curable resin composition obtained as described above is thermally cured to form a reflective film, for example, after the surface of the sheet-like base film is treated with an acid and washed, the cured product is applied to the washed surface. The conductive resin composition is applied to a desired thickness, for example, 5 to 100 μm, using a screen printing method, a spray coating method, or the like. Next, preliminary drying is performed in a hot air furnace or a far-infrared furnace, and the solvent is volatilized from the curable resin composition to make the surface of the coating film tack-free. In the preliminary drying, heating is performed at a temperature of about 60 to 80 ° C. for about 15 to 60 minutes. Next, post-curing is performed by heating for 10 to 80 minutes in a dryer such as a hot-air oven or a far-infrared furnace at 130 to 170 ° C., for example, to thermally cure the coating film on the surface of the base film, and to have a reflective coating Manufacture sheets.

  When the curable resin composition obtained as described above is photocured to form a reflective film, for example, the surface of the sheet-like base film is treated with an acid and washed, and then the curable resin is applied to the washed surface. The composition is applied to a desired thickness, for example, 5 to 100 μm, using a screen printing method, a spray coating method, or the like. Next, in order to volatilize the solvent in the curable resin composition, preliminary drying is performed by heating at a temperature of about 60 to 80 ° C. for about 15 to 60 minutes. Thereafter, the applied curable resin composition is photocured by irradiation with ultraviolet rays. At this time, in the case of forming a predetermined pattern of the reflective film on the reflective sheet, a negative film having a predetermined pattern portion made translucent is brought into close contact with the applied curable resin composition, and ultraviolet rays are irradiated thereon. Then, the non-exposed area corresponding to the predetermined pattern is removed with a dilute alkaline aqueous solution to develop the reflective film having the predetermined pattern. As a developing method, a spray method, a shower method, or the like is used. As a dilute alkali aqueous solution used, a 0.5 to 5% sodium carbonate aqueous solution is generally used, but other alkalis can also be used. Then, a post-cure is performed for 20 to 80 minutes with a hot air circulating dryer or the like at 130 to 170 ° C. to produce a reflective sheet having a target reflective film formed on the sheet-like base film.

  The material of the sheet-like base film is not particularly limited. For example, polyimide, polyethylene terephthalate (PET), polyvinyl fluoride (PVF), fluorinated ethylene / propylene copolymer (FEP), polytetrafluoroethylene (PTFE), aramid , Polyamide / imide, epoxy, polyetherimide, polysulfone, polyethylene naphthalate (PEN), liquid crystal polymer (LCP), and the like.

  When manufacturing a reflective sheet for a solar battery back sheet, for example, a polyethylene terephthalate film having a thickness of 40 μm is used as the base film. Further, the curable resin composition is applied to the surface of the polyethylene terephthalate film so that the film thickness after curing is 20 to 23 μm, for example. Furthermore, it is preferable that the coating part of the curable resin composition is performed on the entire surface or almost the entire surface of the base film surface region facing the back surface of the solar cell module.

  Next, an example of how to use the reflective sheet of the present invention will be described. For example, the reflective sheet of the present invention can be used as a solar battery back sheet by being arranged on the back side of the solar cell module, that is, on the surface opposite to the surface that receives solar radiation. When the reflective sheet of the present invention is used as a solar battery back sheet, sunlight transmitted through the solar cell module without being received by the power generation element of the solar cell module is reflected by the reflective sheet and again from the back side of the solar cell module. Since it returns to the inside of the solar cell module, the power generation efficiency of the solar cell module is improved. In addition, the installation method of the reflective sheet to a solar cell module back surface includes the method of sticking directly on a solar cell module back surface using an adhesive agent or an adhesive tape, for example.

  Next, examples of the present invention will be described. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.

(A-1) (A-2) Synthesis of carboxyl group-containing copolymer resin having aromatic ring Synthesis Example 1
Into a 500 mL four-necked flask equipped with a stirrer, a thermometer, and a reflux tube, 110 g of dipropylene glycol monomethyl ether (hereinafter referred to as DPM) was added, heated to 120 ° C. in a nitrogen atmosphere, and then 17.2 g (0 .2 mol), phenoxyethyl methacrylate (SR-340 manufactured by Sartomer, hereinafter referred to as PEMA) 92.8 g (0.45 mol), dimethyl 2,2′-azobis (2-methylpropionate) (V- 601 (hereinafter referred to as DMAMP) and a mixed solution of 4.6 g of DPM and 10 g of DPM over about 1 hour, and then stirred at 120 ° C. for 3 hours to produce a DPM solution containing about 49% by mass of the copolymer resin of Synthesis Example 1. Thus, a copolymer resin of Synthesis Example 1 was obtained. The weight average molecular weight of the carboxyl group-containing copolymer resin having an aromatic ring was about 25000 (polystyrene conversion), and the solid content acid value was 98 mgKOH / g.

Synthesis example 2
A 500 mL four-necked flask equipped with a stirrer, a thermometer, and a reflux tube was charged with 125 g of dipropylene glycol monomethyl ether (hereinafter DPM), heated to 120 ° C. in a nitrogen atmosphere, and then 34.4 g of methacrylic acid (0. 4 mol), 82.5 g (0.4 mol) of PEMA, 5.5 g of DMAMP, and 10 g of DPM were added dropwise over about 1 hour, followed by stirring at 120 ° C. for 3 hours to obtain a copolymer having a carboxyl group.

  Next, after lowering the temperature in the flask to 100 ° C., a mixture of air and nitrogen (air volume to nitrogen volume ratio of 1 to 2) was passed through the flask at 200 mL / min while glycidyl methacrylate (Japan) Add 21.3 g (0.15 mol) of an oil and fat blender GH (hereinafter GMA), 0.3 g of triphenylphosphine (hereinafter TPP) as a reaction catalyst, 0.1 g of methoxyhydroquinone (hereinafter MEHQ) as a polymerization inhibitor, and add 100 ° C. The reaction is continued for 5 hours at 115 ° C. until the acid value finishes decreasing to produce a DPM solution containing about 52% by mass of the copolymer resin of Synthesis Example 2, and the copolymer resin of Synthesis Example 2 is obtained. It was. The weight average molecular weight was about 18000 (polystyrene conversion), and the solid content acid value was 97 mgKOH / g.

Synthesis example 3
82.5 g (0.4 mol) of PEMA in Synthesis Example 2 was converted to 74.2 g (0.36 mol), and 21.3 g (0.15 mol) of GMA was 4-hydroxybutyl acrylate glycidyl ether (4-HBAGE, Nippon Kasei Chemical Co., Ltd., hereinafter referred to as 4- HBAGE) A DPM solution containing about 52% by mass of the copolymer resin of Synthesis Example 3 was produced in the same manner as in Synthesis Example 2 except that the amount was changed to 30.0 g (0.15 mol). Obtained. The weight average molecular weight was about 16000 (polystyrene conversion), and the solid content acid value was 97 mgKOH / g.

Synthesis example 4
125 g DPM of Synthesis Example 2 to 160 g, 34.4 g (0.4 mol) of methacrylic acid to 56.8 g (0.66 mol), 82.5 g (0.4 mol) of PEMA to 47.4 g (0.23 mol), The copolymer resin of Synthesis Example 4 was prepared in the same manner as Synthesis Example 2 except that 5.5 g of DMAMP was changed to 6.5 g, and further 21.3 g (0.15 mol) of GMA was changed to 70.1 g (0.35 mol) of 4-HBAGE. A DPM solution containing about 52% by mass was produced, and a copolymer resin of Synthesis Example 4 was obtained. The weight average molecular weight was about 19000 (polystyrene conversion), and the solid content acid value was 96 mgKOH / g.

Synthesis example 5
Synthetic Example 2 except that 82.5 g (0.4 mol) of PEMA in Synthetic Example 2 was changed to 85.1 g (0.34 mol) of 2 (2-phenoxyethoxy) ethyl methacrylate (Nippon Bremer PAE-100, hereinafter referred to as 2 PEEMA). In the same manner as above, a DPM solution containing about 52% by mass of the copolymer resin of Synthesis Example 5 was produced, and the copolymer resin of Synthesis Example 5 was obtained. The weight average molecular weight was about 18000 (polystyrene conversion), and the solid content acid value was 96 mgKOH / g.

Synthesis Example 6
A DPM solution containing about 52% by mass of the copolymer resin of Synthesis Example 6 in the same manner as Synthesis Example 2 except that 82.5 g (0.4 mol) of PEMA of Synthesis Example 2 was changed to 75.1 g (0.3 mol) of 2PEEMA. To obtain a copolymer resin of Synthesis Example 6. The weight average molecular weight was about 20000 (polystyrene conversion), and the solid content acid value was 97 mgKOH / g.

Synthesis example 7
125 g DPM of Synthesis Example 2 to 105 g, 34.4 g (0.4 mol) of methacrylic acid to 25.8 g (0.3 mol), 82.5 g (0.4 mol) of PEMA to 42.7 g (0.4 mol) of styrene and normal Synthesis example except that 15.6 g (0.1 mol) of butyl methacrylate (Mitsubishi Rayon acrylate ester BMA, hereinafter referred to as nBMA) and GMA 21.3 g (0.15 mol) were changed to 4-HBAGE 22.0 g (0.11 mol) In the same manner as in Example 2, a DPM solution containing about 47% by mass of the copolymer resin of Synthesis Example 7 was produced to obtain the copolymer resin of Synthesis Example 7. The weight average molecular weight was about 14,000 (polystyrene conversion), and the solid content acid value was 95 mgKOH / g.

Synthesis Example 8
125 g DPM of Synthesis Example 2 to 110 g, 34.4 g (0.4 mol) methacrylic acid to 25.2 g (0.35 mol) acrylic acid, 82.5 g (0.4 mol) PEMA to 59.8 g (0.29 mol) A DPM solution containing about 48% by mass of the copolymer resin of Synthesis Example 8 was produced in the same manner as Synthesis Example 2 except that 5.5 g of DMAMP was changed to 4 g, and the copolymer resin of Synthesis Example 8 was obtained. The weight average molecular weight was about 16000 (polystyrene conversion), and the solid content acid value was 101 mgKOH / g.

Synthesis Example 9
34.4 g (0.4 mol) of methacrylic acid of Synthesis Example 2 was added to 23.8 g (0.33 mol) of acrylic acid, 82.5 g (0.4 mol) of PEMA was added to 57.6 g (0.23 mol) of 2 PEEMA, and 5.5 g of DMAMP was added. A DPM solution containing about 48% by mass of the copolymer resin of Synthesis Example 9 was produced in the same manner as in Synthesis Example 2 except that the amount was changed to 4.0 g, and a copolymer resin of Synthesis Example 9 was obtained. The weight average molecular weight was about 15000 (polystyrene conversion), and the solid content acid value was 94 mgKOH / g.

  Table 1 below shows the raw material ratio (mol), aromatic hydrocarbon skeleton ratio (mass%), and acid value (mgKOH / g) of the resins according to Synthesis Examples 1 to 9.

Comparative Synthesis Example 1
Into a 500 mL four-necked flask equipped with a stirrer, a thermometer, and a reflux tube, 80 g of propylene glycol diacetate (hereinafter referred to as PGDA) was added, heated to 90 ° C. in a nitrogen atmosphere, and then 28.4 g (0.2 mol) of GMA. 2-hydroxyethyl methacrylate caprolactone adduct (average 1 mol addition, Placel Cell FM1D manufactured by Daicel Chemical Industries) 49.9 g (0.2 mol), DMAMP 1 g, mercaptopropionic acid-2-ethylhexyl (manufactured by Sakai Chemical Industry, EHMP) 1 g and PGDA After 80 g of the mixed solution was dropped over about 1 hour, the mixture was stirred at 90 ° C. for 8 hours to obtain a copolymer having an epoxy group.

Next, 72.02 g (0.21 mol) of acrylic acid and 0.5 g of TPP as a reaction catalyst were passed through the flask while aerated with a mixed gas of air and nitrogen (air volume to nitrogen volume ratio of 1 to 2) at 200 mL / min. Add 0.2g of MEHQ as a polymerization inhibitor, react at 100 ° C for 5 hours, and continue the reaction at 115 ° C until the acid value has finished decreasing, adding the epoxy group of the copolymer and the carboxyl group of acrylic acid. Went. After the acid value became 2 or less, the temperature in the flask was lowered to 90 ° C., and 16.0 g (0.16 mol) of succinic anhydride was added and reacted for 8 hours or longer to open the ring of acid anhydride. An addition reaction was performed. A solution of the copolymer resin of Comparative Synthesis Example 1 having no aromatic hydrocarbon skeleton was obtained with the point when the acid anhydride peak disappeared by IR as the end point of the reaction. This resin solution had a solid content of about 40% by mass, a weight average molecular weight of about 12000 (in terms of polystyrene), and a solid content acid value of 78 mgKOH / g.

Comparative Synthesis Example 2
In a 500 mL four-necked flask equipped with a stirrer, thermometer, and reflux tube, 105 g of DPM was charged and heated to 120 ° C. under a nitrogen atmosphere. Then, 43.0 g (0.5 mol) of methacrylic acid, 0.15 mol), a mixed solution of DMAMP 4.5 g and DPM 10 g was added dropwise over about 1 hour, followed by stirring at 120 ° C. for 3 hours to obtain a copolymer having a carboxyl group.

  Next, after the temperature in the flask was lowered to 100 ° C., 14.2 g of GMA (0. 2 g) was introduced while a gas mixture of air and nitrogen (air volume to nitrogen volume ratio of 1 to 2) was passed through the flask at 200 mL / min. 1 mol) and m, p-cresyl glycidyl ether (Sakamoto Yakuhin m, p-CGE) 32.8 g (0.2 mol), reaction catalyst as triphenylphosphine (TPP) 0.3 g, polymerization inhibitor as methoxyhydroquinone (Hereafter MEHQ) 0.1 g was added, reacted at 100 ° C. for 5 hours, and continued at 115 ° C. until the acid value decreased, and the aromatic hydrocarbon having a hydrogen atom at the α-position of the carboxyl group and side chain A DPM solution containing about 48% by mass of a copolymer resin having a skeleton and a methacryl group was produced, and a copolymer resin of Comparative Synthesis Example 2 was obtained. The weight average molecular weight was about 15000 (polystyrene conversion), and the solid content acid value was 96 mgKOH / g.

Comparative Synthesis Example 3
Comparative Production Example 2 except that GMA 14.2 g (0.1 mol) and m, p-cresyl glycidyl ether 32.8 g (0.2 mol) were replaced with GMA 42.6 g (0.3 mol). Similarly, a DPM solution containing about 49% by mass of a copolymer resin having a carboxyl group and a methacryl group but not having an aromatic hydrocarbon skeleton was produced, and a copolymer resin of Comparative Synthesis Example 3 was obtained. The weight average molecular weight was about 15000 (polystyrene conversion), and the solid content acid value was 100 mgKOH / g.

Examples 1-23, Comparative Examples 1-9
Each component shown in the following Tables 2, 3, and 4 was blended at the blending ratios shown in the following Tables 2, 3, and 4, and after premixing with a stirrer, mixed and dispersed at room temperature using three rolls, Curable resin compositions used in Examples 1 to 23 and Comparative Examples 1 to 9 were prepared. And the prepared curable resin composition was applied as follows and the test piece was created. The compounding amounts shown in the following Tables 2, 3, and 4 represent parts by mass.

In Table 2,
Epicoat 828: Japan Epoxy Resin Co., Ltd. bisphenol A type epoxy resin,
DPHA: Nippon Kayaku Co., Ltd. dipentaerythritol hexaacrylate,
DPM: Kyowa Hakko Kogyo Co., Ltd. dipropylene glycol monomethyl ether,
Rutile type titanium oxide: “CR-80” manufactured by Ishihara Sangyo Co., Ltd.
KS-66: Silicon oil manufactured by Shin-Etsu Silicone Co., Ltd.

In Table 3,
YX-8000: Nuclear hydrogenated bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.
TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide,
BAPO: Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide.

In Table 4,
ACA-Z250: resin solution manufactured by Daicel Chemical Industries, Ltd. (having an alicyclic skeleton, no aromatic hydrocarbon skeleton, having a carboxyl group and an acrylic group),
Epicoat 1004F: Bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.
YDC-1312: Ditertiary butyl hydroquinone modified epoxy resin manufactured by Toto Kasei Co., Ltd.
BP4EA: EO-modified bisphenol A acrylate (EO = 4) manufactured by Kyoeisha Chemical,
AH-600: Bifunctional urethane-modified epoxy acrylate manufactured by Kyoeisha Chemical,
EBECRYL 3708: Daicel Cytec Co., Ltd. bifunctional epoxy acrylate,
UF-8001G: Bifunctional urethane acrylate made by Kyoeisha Chemical,
SPEEDCURE TPO: Made by Nippon Siebel Hegner,
IRGACURE 819: manufactured by Ciba Specialty Chemicals.

Test piece preparation process 1 (Examples 1-2, Comparative Examples 1-3)
It is a test piece preparation process for evaluating the reflectance and hardness of the heat-cured coating film. Regarding the hardness, a curable resin composition was applied to the surface of a sheet-like polyethylene terephthalate film having a thickness of 40 μm by a screen printing method, and then preliminarily dried by heating at 70 ° C. for 20 minutes in a BOX furnace. After the preliminary drying, a post-cure was performed at 150 ° C. for 60 minutes in a BOX furnace to form a cured coating film, and a reflective sheet test piece was prepared. The thickness of the cured coating film after post-cure was 20 to 23 μm. As for the reflectance, in order to eliminate the influence of deterioration of polyethylene terephthalate itself due to the environmental standing, which is an accelerated test, it is the same as the evaluation of hardness described above on a glass plate (1.2 mm thickness) instead of a sheet-like polyethylene terephthalate film. A cured coating film was formed in the above process to prepare a test piece of a reflective sheet.

Test piece preparation step 2 (Examples 3 to 12, Comparative Examples 4 to 6)
It is a test piece preparation process for evaluating the reflectance and hardness of the photocured coating film. Regarding the hardness, a curable resin composition was applied to the surface of a sheet-like polyethylene terephthalate film having a thickness of 40 μm by screen printing, and then pre-dried at 80 ° C. for 20 minutes in a BOX furnace. After pre-drying, the coating film was exposed to 500 mJ / cm ² with an exposure device (OMW HMW-680GW) and then post-cured at 150 ° C. for 60 minutes in a BOX furnace to be cured on the surface of the polyethylene terephthalate film. A film was formed to prepare a test piece of a reflective sheet. The thickness of the cured coating film after post-cure was 20 to 23 μm. As for the reflectance, in order to eliminate the influence of deterioration of polyethylene terephthalate itself due to the environmental standing, which is an accelerated test, it is the same as the evaluation of hardness described above on a glass plate (1.2 mm thickness) instead of a sheet-like polyethylene terephthalate film. A cured coating film was formed in the above process to prepare a test piece of a reflective sheet.

Test piece preparation step 3 (Examples 13 to 23, Comparative Examples 7 to 9)
This is a test piece preparation step for evaluating the reflectance, flexibility, warpage, and flame retardancy of a photocured coating film. For hardness, flexibility, warpage, and flame retardancy, a curable resin composition is applied by screen printing to the surface of a 40 µm thick sheet of polyethylene terephthalate film that has been surface-treated with dilute sulfuric acid (3%). Thereafter, preliminary drying was performed at 80 ° C. for 20 minutes in a BOX furnace. After pre-drying, the coating film was exposed to 500 mJ / cm ² with an exposure device (OMW HMW-680GW) and then post-cured at 150 ° C. for 60 minutes in a BOX furnace to be cured on the surface of the polyethylene terephthalate film. A film was formed to prepare a test piece of a reflective sheet. The thickness of the cured coating film after post-cure was 20 to 23 μm. Regarding the reflectance, in order to remove the influence of deterioration of polyethylene terephthalate itself due to the environmental standing as an accelerated test, evaluation of the above-mentioned flexibility, etc. on a glass plate (1.2 mm thickness) instead of a sheet-like polyethylene terephthalate film A cured coating film was formed by the same process as that described above to prepare a reflective sheet test piece.

Evaluation (1) Reflectance (%)
Initial: With respect to the test piece after the post cure, the reflectance at 450 nm was measured with a spectrophotometer U-3410 (manufactured by Hitachi, Ltd .: φ60 mm integrating sphere).
After heating: heat resistance is evaluated for the reflectance of the reflective sheet. After heating the test piece at 170 ° C. for 100 hours, the spectrophotometer U-3410 (manufactured by Hitachi, Ltd .: φ60 mm integrating sphere) is used. The reflectance of the test piece at 450 nm was measured.
After irradiation: Light resistance is evaluated for the reflectance of the reflection sheet. After UV irradiation (2 minutes) at 50 J / cm ² , the spectrophotometer U-3410 (manufactured by Hitachi, Ltd .: φ60 mm integrating sphere) The reflectance of the test piece at 450 nm was measured.
After humidification and heating: The weather resistance is evaluated for the reflectance of the reflective sheet. After leaving the test piece to stand at 85 ° C. and 85% RH for 1000 hours, a spectrophotometer U-3410 (manufactured by Hitachi, Ltd.) : Φ60 mm integrating sphere), the reflectance of the test piece at 450 nm was measured.
(2) Hardness Press the B to 9H pencil sharpened so that the tip of the core is flat against the cured coating film at an angle of about 45 °, and record the hardness of the pencil so that the coating film does not peel off. did.
(3) Flexibility About the coating after exposure, the flexibility of the coating was evaluated by visual observation and optical microscope observation of × 200 by a cylindrical mandrel method. ○: No abnormality at a diameter of 2 mm or less, Δ : No abnormality at a diameter of 4 mm, but abnormalities such as cracks and peeling when the diameter was 2 mm or less, and x: Anomalies such as cracks and peeling when the diameter was 4 mm or more.
(4) Warpage After cutting the test piece into 2cm x 2.5cm, place the test piece gently on the horizontal table so that the top is concave, and make sure that no external force is applied. The vertical distance between the corner and the table was measured to a unit of 1 mm with a straight scale, and the maximum value was taken as the amount of warpage. About the measurement result, (circle): The amount of curvature of less than 5 mm, (triangle | delta): The amount of curvature of 5-8 mm, and x: The amount of curvature exceeding 8 mm evaluated.
(5) Flame retardancy The test piece was subjected to a vertical combustion test based on the UL94 standard. Evaluation was expressed as VTM-0 to combustion based on the UL94 standard.

  The measurement results of Examples 1 to 23 and Comparative Examples 1 to 9 are shown in Tables 5, 6, and 7 below.

  When the reflective film of the reflective sheet is formed by thermosetting the curable resin composition, the reflective film is heated by using methacrylic acid as a raw material of the copolymer from Examples 1 and 2 and Comparative Examples 1 and 2. Thereafter, a decrease in reflectance after UV irradiation and after humidification and heating could be suppressed. Further, from Examples 1 and 2 and Comparative Example 3, after polymerization, by using the general formula (II) and the general formula (III) having no hydrogen atom at the side chain α-position of the aromatic hydrocarbon skeleton, It was possible to suppress a decrease in reflectance after heating the reflective coating, after UV irradiation, and after humidification and heating. Furthermore, in Examples 1 and 2, the hardness was 4H or more, and the hardness of the coating film was excellent. On the other hand, by adding m, p-cresyl glycidyl ether, methacrylic acid was used as a raw material for the copolymer in Comparative Example 3 containing an aromatic hydrocarbon having a hydrogen atom at the side chain α-position after polymerization. However, the reflectance of the reflective coating decreased after heating, after irradiation, and after humidification and heating.

  When the curable resin composition is photocured to form a reflective coating of the reflective sheet, the reflective coating is obtained by using (meth) acrylic acid as a raw material of the copolymer from Examples 3 to 12 and Comparative Examples 4 and 5. It was possible to suppress a decrease in reflectance after heating, after UV irradiation and after humidification and heating. Further, from Examples 3 to 12 and Comparative Example 6, by using the general formula (II) and the general formula (III) having no hydrogen atom at the side chain α-position of the aromatic hydrocarbon skeleton after polymerization, It was possible to suppress a decrease in reflectance after heating the reflective coating, after UV irradiation, and after humidification and heating. Furthermore, in Examples 3 to 12, all had a hardness of 4H or more and were excellent in the hardness of the coating film. On the other hand, by adding m, p-cresyl glycidyl ether, methacrylic acid was used as a raw material for the copolymer in Comparative Example 6 containing an aromatic hydrocarbon having a hydrogen atom at the side chain α-position after polymerization. However, the reflectance of the reflective coating decreased after heating, after irradiation, and after humidification and heating.

  When a curable resin composition, which is a curable resin composition further blended with a phosphorus-based flame retardant and a metal hydroxide, was photocured to form a reflective film of a reflective sheet, Examples 13 to 23 and Comparative Examples From the comparison between 8, 9 and Comparative Example 7, it is possible to suppress a decrease in reflectance after heating the reflective coating, after UV irradiation, and after humidification and heating by using (meth) acrylic acid as a raw material for the copolymer. did it. In Examples 13 to 23, all of flexibility, low warpage, and flame retardancy were excellent. On the other hand, since Comparative Examples 7 and 8 did not contain an aromatic hydrocarbon skeleton, the compatibility with a diluent or the like was inferior, the flexibility decreased, and no flame retardancy was observed. From Examples 13 to 23 and Comparative Example 9, by using (meth) acrylic acid as a raw material for the copolymer, it was possible to suppress a decrease in each reflectance without containing an aromatic hydrocarbon skeleton, Since it has an alicyclic skeleton without containing an aromatic hydrocarbon skeleton, the compatibility with a diluent or the like is inferior, the flexibility is lowered, and no flame retardancy is observed. Further, in Comparative Examples 7 and 9, the warpage was large and the warpage was inferior.

  The present invention provides a reflective sheet having a reflection film excellent in flexibility, low warpage, and flame retardancy after ultraviolet irradiation, after heating and after humidification and heating, and thus particularly excellent in light resistance. It is highly useful in the field of solar cell module backsheets where heat resistance, weather resistance and ease of handling are required.

Claims (2)

A reflective sheet for a solar cell module having a reflective film formed of a curable resin composition,
The curable resin composition is
(A-1) General formula (I)

(Wherein R ¹ represents a hydrogen atom or a methyl group),
Formula (III)

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, and t-butyl. Group, an adamantyl group or a trifluoromethyl group, A ¹ represents a C 2-10 alkylene group or a C 3-10 hydroxyalkylene group containing a linear or cyclic skeleton, and m is 0 or 1-3. An integer, p is an integer of 1 to 5), and a copolymer resin obtained by reacting the compound represented by
Or (A-2) general formula (I)

(Wherein R ¹ represents a hydrogen atom or a methyl group),
Formula (II)

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, and t-butyl. A group, an adamantyl group or a trifluoromethyl group, and m is an integer of 0 or 1-3) and / or the general formula (III)

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a phenyl group, an α-cumyl group, an alkoxy group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms in an alkyl group, and t-butyl. Group, an adamantyl group or a trifluoromethyl group, A ¹ represents a C 2-10 alkylene group or a C 3-10 hydroxyalkylene group containing a linear or cyclic skeleton, and m is 0 or 1-3. An integer, p is an integer of 1 to 5), and a copolymer obtained by adding a compound having an oxirane ring and an ethylenically unsaturated bond to a part of the carboxyl group of the copolymer obtained by reacting the compound represented by Polymerization resin,
(B) curing agent,
A reflective sheet for a solar cell module, comprising (C) a diluent and (D) an inorganic white pigment. The compound having an oxirane ring and an ethylenically unsaturated bond has the general formula (IV)

(Wherein R ¹ represents a hydrogen atom or a methyl group, A ² represents an alkylene group having 2 to 10 carbon atoms, and q is 0 or an integer of 1 to 5). The reflective sheet for solar cell modules according to claim 1, characterized in that: