JP2019114793A - Primer and solar cell backside protective sheet - Google Patents

Abstract

To provide a primer which enables the formation of a primer layer having blackness, superior in the stability of storing a coating liquid and achieving the good adhesion with a base material after an endurance test, and a solar cell backside protective sheet.SOLUTION: A primer comprises: a resin; a hardening agent; and a coloring agent. In 100 mass% of nonvolatile components of the primer, 10-40 mass% of the coloring agent is included. The coloring agent includes 40-80 mass% of a quinacridone-based purple pigment A, 10-40 mass% of a phthalocyanine-based blue pigment B, and a total of 10-40 mass% of a yellow pigment selected from a group consisting of an isoindolinone-based yellow pigment C and an isoindolin-based yellow pigment E to 100 mass% thereof.SELECTED DRAWING: None

Description

The present invention relates to a primer used to form a primer layer such as a solar cell back surface protection sheet.

  The embodiment in which a plurality of solar cell modules used as a clean energy source is, for example, a laminate of a surface protection sheet / surface sealing material / solar cell element / back surface sealing material / back surface protection sheet Is common. A back surface protection sheet may form a primer layer in the surface in order to improve adhesiveness with a back surface sealing material.

  A solar cell may be installed on the roof of a house, and in many cases, the appearance as viewed from the light receiving surface side of the back surface protection sheet is colored black, with an emphasis on the appearance. Therefore, Patent Document 1 and Patent Document 2 disclose a back surface protection sheet colored in black with carbon black. However, since carbon black absorbs light, the back surface protection sheet tends to have a high temperature, and as a result, the entire solar cell module has a high temperature, which causes a problem of a decrease in power generation efficiency.

Moreover, although the wavelength range which a solar cell element absorbs is 300-800 nm of an amorphous silicon solar cell element generally, and a crystalline silicon solar cell element is 400-1200 nm, the light which the solar cell element can not absorb and permeate | transmits Is reflected by the reflective layer of the back surface protection sheet, the reflected light is again incident on the solar cell element, and the photoelectric conversion efficiency is improved.

Then, as a back surface protection sheet provided with a layer colored black without carbon black and a reflection layer which reflects light of a wide wavelength, in patent document 3, copper phthalocyanine, quinacridone is used as a coloring agent to polyolefin film of a substrate. The back surface protection sheet which knead | mixed in red and benz imidazolone yellow is disclosed.
Further, Patent Document 4 discloses a back surface protection sheet using a primer containing a red pigment, a blue pigment, and a yellow pigment as colorants.

JP, 2009-249421, A JP, 2010-138300, A International Publication 2013/183658 International Publication 2013/105522

However, the back surface sealing sheet of patent document 3 knead | mixed the coloring agent in the base material, and it was not able to thin the thickness of the whole back surface sealing sheet. Then, when a coloring agent was mix | blended with a primer, there existed a problem to which the adhesiveness of a primer layer and a base material falls after an endurance test. In addition, there is a problem that the storage stability (solution stability) of the primer is poor because the colorants are incompatible with each other, and a so-called color separation phenomenon occurs.
Moreover, the back surface protection sheet of patent document 4 had the problem to which the adhesiveness of a primer layer and a base material falls after an endurance test.

  The present invention aims to provide a primer capable of forming a primer layer having a blackness, excellent storage stability of a coating liquid, and good adhesion to a substrate after a durability test, and a solar cell back surface protection sheet. I assume.

The primer of the present invention comprises a resin, a curing agent, and a colorant,
10 to 40% by mass of the colorant in 100% by mass of the nonvolatile matter of the primer,
40 to 80% by mass of quinacridone purple pigment A, 10 to 40% by mass of phthalocyanine blue pigment B in 100% by mass of the coloring agent, and isoindolinone yellow pigment C and isoindoline yellow pigment E It contains 10 to 40% by mass in total of a yellow pigment selected from the group.

  According to the present invention described above, a primer having a blackness, excellent storage stability of a coating solution, and capable of forming a primer layer having good adhesion to a substrate after a durability test, and a solar cell back surface protection sheet Can provide

Hereinafter, the present invention will be described in detail. Needless to say, other embodiments are also included in the scope of the present invention as long as they conform to the spirit of the present invention. Moreover, the numerical range specified using "-" in this specification shall include the numerical value described before and after "-" as a range of a lower limit and an upper limit. Also, in the present specification, "film" and "sheet" are not distinguished by thickness. In other words, the "sheet" in the present specification includes a thin film-like one, and the "film" in the present specification also includes a thick sheet-like one.
Further, in the present specification, “(meth) acrylic copolymer” includes “acrylic copolymer”, “methacrylic copolymer”, and “acrylic-methacrylic copolymer”. “(Meth) acryloyl” is meant to include “acryloyl” and “methacryloyl”, and “(meth) acrylic” is meant to include “acrylic” and “methacrylic”. The degree of blackness is not black that is the same as that of carbon black in the appearance of the primer layer, but it is black that can be visually recognized black. Solar cells are also called solar power.

The primer of the present invention contains 10 to 40% by mass of the coloring agent in 100% by mass of the nonvolatile matter of the primer,
40 to 80% by mass of quinacridone purple pigment A, 10 to 40% by mass of phthalocyanine blue pigment B in 100% by mass of the coloring agent, and isoindolinone yellow pigment C and isoindoline yellow pigment E It contains 10 to 40% by mass in total of a yellow pigment selected from the group.
The primer of the present specification is coated on a substrate to form a primer layer. The primer layer improves the adhesion between the substrate and the other layers. The primer of the present specification has a suitable black appearance, and is preferably used for forming a light reflective film and a primer sheet for the back surface of a solar cell comprising the primer layer (hereinafter referred to as a back surface protective sheet) .

  A primer forms a primer layer as mentioned above, and is laminated | stacked so that a back surface sealing material may be contacted at the thermocompression bonding process at the time of producing a solar cell module. This primer layer blackens the appearance of the back surface protection sheet and bonds the back surface protection sheet and the back surface sealing material.

  The primer contains a resin, a curing agent, and a colorant as essential components.

<Resin>
Examples of the resin used for the primer include polyester resins, urethane resins and acrylic resins.

  The polyester-based resin is, for example, a polyester polyurethane obtained by adding a carboxylic acid component and a hydroxyl component to a polyester resin obtained by reacting (esterification reaction, transesterification) with a carboxylic acid component and further reacting an isocyanate compound with a polyester resin having a hydroxyl group. The resin includes polyester polyurethane polyurea resin obtained by reacting a diamine component.

  Examples of the carboxylic acid component include benzoic acid, p-tert-butylbenzoic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, adipic acid, azelaic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, anhydrous Maleic acid, fumaric acid, itaconic acid, tetrachlorophthalic anhydride, 1,4-cyclohexanedicarboxylic acid, trimellitic acid anhydride, methylcyclohexen tricarboxylic acid anhydride, pyromellitic anhydride, ε-caprolactone, fatty acids and the like can be mentioned.

  Examples of the hydroxyl group component include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, 3-methylpentanediol, 1,4. -Diols such as cyclohexanedimethanol; Trifunctional or higher functional polyols such as glycerin, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, and dipentaerythritol.

The urethane resin is, for example, a resin in which a hydroxyl group component and an isocyanate compound are reacted according to a conventional method.
Examples of the hydroxyl group component include polyethylene glycol, polypropylene glycol, polyether polyols added with ethylene oxide and propylene oxide, and polymer polyols such as acrylic polyols and polybutadiene polyols.
Examples of the isocyanate compound include trimethylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), methylene bis (4,1-phenylene) = diisocyanate (MDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI) And diisocyanates such as xylylene diisocyanate (XDI), trimethylolpropane adducts of these diisocyanates, isocyanurates which are trimers of these diisocyanates, biuret conjugates of these diisocyanates, polymeric diisocyanates and the like.

An acrylic resin is a copolymer which synthesize | combined the monomer suitably selected from a (meth) acrylic-acid alkylester, a reactive functional group containing monomer, and another monomer according to a conventional method.
(Meth) acrylic acid alkyl ester is, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-hexyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, Butyl methacrylate, n-hexyl methacrylate, lauryl methacrylate and the like can be mentioned.
The reactive functional group-containing monomer is, for example, 4-hydroxybutyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate, hydroxypropyl methacrylate, acrylamide, methacrylamide, acrylonitrile, Methacrylonitrile, N-methylol acrylamide, glycidyl methacrylate and the like can be mentioned.
Other monomers include, for example, benzyl acrylate, methoxyethyl acrylate, tetrahydrofurfuryl acrylate and the like.

  It is preferable that these resins contain reactive functional groups such as hydroxyl groups and carboxylic acid groups in order to crosslink with the curing agent. Among these resins, acrylic trees having excellent long-term weather resistance outdoors are preferable.

  The resins may be used alone or in combination of two or more.

  10,000-1,000,000 are preferable, as for the weight average molecular weight (Mw) of resin, 20,000-750,000 are more preferable, 30,000-500,000 are more preferable. When the weight average molecular weight of the resin is 1,000,000 or less, the adhesion between the primer layer and the substrate is further improved. When the weight average molecular weight is 10,000 or more, the durability of the primer layer is further improved. In addition, a weight average molecular weight is a value of polystyrene conversion by gel permeation chromatography (GPC) of resin. For example, the temperature of a column (Showa Denko KF-805L, KF-803L, and KF-802) is 40 ° C., tetrahydrofuran is used as an eluent, the flow rate is 0.2 ml / min, detection is RI, The sample concentration was 0.02%, and polystyrene was used as a standard sample. The weight average molecular weight of the present invention is the value measured by the above method.

  -20-100 degreeC is preferable, as for the glass transition temperature (Tg) of resin, 0-90 degreeC is more preferable, and 20-80 degreeC is further more preferable. The adhesiveness to a base material improves more that the glass transition temperature of resin is 100 degrees C or less. When the Tg is -20 ° C or higher, the tackiness of the surface of the primer layer is reduced, and blocking hardly occurs. In addition, glass transition temperature shows the thing of the glass transition temperature measured by differential scanning calorimetry (DSC) about resin which dried resin and was made into 100% of the non volatile matter. For example, the glass transition temperature is set by setting an aluminum pan containing a weighed sample of about 10 mg of the sample and an aluminum pan not containing the sample in a DSC and using it in a nitrogen stream using liquid nitrogen -100 Quench to ° C., then ramp to 200 ° C. at 20 ° C./min and plot the DSC curve. A straight line extending the baseline on the low temperature side of this DSC curve (the DSC curve portion in the temperature range where no transition and reaction occur in the specimen) to the high temperature side, and the slope of the curve of the step change portion of the glass transition is maximized From the point of intersection with the tangent drawn at such a point, the extrapolated glass transition start temperature (Tig) can be determined, and this can be determined as the glass transition temperature. The glass transition temperature of the present invention is the value measured by the above method.

  The resin preferably contains 30% by mass or more and less than 90% by mass in 100% by mass of the nonvolatile content of the primer, and more preferably 60% by mass or more and less than 90% by mass.

<Hardening agent>
The curing agent is not particularly limited as long as it is a compound that improves the durability of the entire solar cell module by crosslinking. A hardening agent can be suitably selected according to the kind of functional group of resin. For example, when the resin has a hydroxyl group, for example, a polyisocyanate compound can be used as a curing agent. When the resin has a carboxylic acid group, for example, an epoxy compound can be used as a curing agent.

  Examples of polyisocyanate compounds include aromatic polyisocyanates, linear or cyclic aliphatic polyisocyanates, and araliphatic polyisocyanates. The aromatic polyisocyanate is, for example, 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6- Tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanatobenzene, dianisidine diisocyanate, 4,4'-diphenylether diisocyanate, 4,4 ', 4 "-Triphenylmethane triisocyanate etc. is mentioned.

Examples of chain aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and the like. Examples include dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate and the like.
Alicyclic polyisocyanates are, for example, 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI), 1,3-cyclopentadiisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, methyl 2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,4-bis (isocyanatomethyl) cyclohexane and the like.
The aromatic aliphatic polyisocyanate is, for example, ω, ω′-diisocyanate-1, 3-dimethylbenzene, ω, ω′-diisocyanate-1, 4-dimethylbenzene, ω, ω′-diisocyanate-1, 4-diethylbenzene, 1, 4- tetramethyl xylylene diisocyanate, 1, 3- tetramethyl xylylene diisocyanate, etc. are mentioned.

  In addition to the above-mentioned polyisocyanate, an adduct of the above-mentioned polyisocyanate and a polyol compound such as trimethylolpropane or the like, a buret or isocyanurate of the above-mentioned polyisocyanate, furthermore, the above-mentioned polyisocyanate and known polyether polyol, polyester polyol, acrylic polyol And adducts with polybutadienepolyol, polyisoprenepolyol, and the like.

  Among these polyisocyanate compounds, low yellowing type aliphatic or alicyclic polyisocyanates with less discoloration are preferable, and from the viewpoint of moist heat resistance, isocyanurate is preferable. More specifically, isocyanurate of hexamethylene diisocyanate (HDI) and isocyanurate of 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI) are preferable. The polyisocyanate compound of the present specification is preferably a blocked polyisocyanate compound from the viewpoint of improving the adhesion to a substrate.

Examples of epoxy compounds include glycidyl ether compounds and glycidyl ester compounds.
Examples of glycidyl ether compounds include bisphenol epoxy resins, novolac epoxy resins, biphenol epoxy resins, bixylenol epoxy resins, trihydroxyphenylmethane epoxy resins, tetraphenylolethane epoxy resins, and the like. Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, brominated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin and the like. The novolac epoxy resin includes, for example, phenol novolac epoxy resin, cresol novolac epoxy resin, brominated phenol novolac epoxy resin, naphthalene skeleton-containing phenol novolac epoxy resin, dicyclopentadiene skeleton-containing phenol novolac epoxy resin, etc. Be Examples of glycidyl ester compounds include terephthalic acid diglycidyl ester and the like.

  The curing agents may be used alone or in combination of two or more.

  The curing agent is preferably contained in an amount of about 1 to 20% by mass in 100% by mass of the nonvolatile content of the primer, and more preferably 3 to 10 parts by mass.

<Colorant>
Herein, the colorant uses three colorants to replace the carbon black to obtain a black color tone. The colorant contains, as essential components, a quinacridone purple pigment A, a phthalocyanine blue pigment B, and an isoindolinone yellow pigment C and / or an isoindoline yellow pigment E as yellow pigments. When the primer of the present specification contains quinacridone purple pigment A, the dispersibility of the entire coloring agent is improved, color separation does not easily occur after long-term storage of the primer (coating solution), and storage stability of the primer is improved. In addition, when the isoindolinone yellow pigment C and / or the isoindoline yellow pigment E is contained, it is possible to suppress the decrease in the adhesion between the primer layer and the substrate after the endurance test, which is surprising. Although the factor is not clear, the isoindole skeleton contained in these pigments contributes to adhesion by strengthening the intermolecular force between the surrounding pigment, resin, and base material, and phthalocyanine blue pigment B It is speculated that the affinity with the aromatic ring skeleton site of quinacridone purple pigment A is enhanced by strengthening the intermolecular force to further enhance the adhesion.

  The quinacridone purple pigment A is a purple pigment having a quinacridone skeleton, and examples thereof include Pigment Violet 19. Here, the purple pigment referred to here is C.I. I. It is a pigment classified into Pigment Violet.

  The phthalocyanine-based blue pigment B is a pigment having a phthalocyanine skeleton, and for example, Pigment Blue 15, Pigment Blue 15: 1, Pigment Blue 15: 2, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 15: 6. , Pigment Blue 16, Pigment Blue 17: 1, Pigment Blue 75, and Pigment Blue 79. Among them, Pigment Blue 15, Pigment Blue 15: 1, Pigment Blue 15: 2, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 75 are preferable in view of weatherability and color tone.

  The isoindolinone-based yellow pigment C is a yellow pigment having an isoindolinone skeleton, and examples thereof include Pigment Yellow 109, Pigment Yellow 110, and Pigment Yellow 173. The term "yellow pigment" as used herein refers to C.I. I. Pigment Yellow classified as Pigment Yellow.

  The isoindoline-based yellow pigment E is a yellow pigment having an isoindoline skeleton, and examples thereof include Pigment Yellow 139 and Pigment Yellow 185. The term "yellow pigment" as used herein refers to C.I. I. Pigment Yellow classified as Pigment Yellow. Among these, Pigment Yellow 139 is particularly preferable in terms of color tone.

  The primer contains 10 to 40% by mass, and more preferably 15 to 35% by mass, of the colorant in 100% by mass of the non volatile matter. By setting the content of the coloring agent to 40% by mass or less, the adhesion to the substrate is further improved, and by setting the content to 10% by mass or more, the blackness of the appearance is further improved.

  The colorant comprises 40 to 80% by weight of quinacridone purple pigment A, 10 to 40% by weight of phthalocyanine blue pigment B in 100% by weight, and isoindolinone yellow pigment C as a yellow pigment and / or isoindoline The yellow pigment E is contained in a total amount of 10 to 40 parts by mass. By containing a coloring agent in this proportion, an appropriate blackness can be obtained, the storage stability of the primer can be improved, and a primer layer having good adhesion to the substrate after the durability test can be obtained.

  The content of the isoindolinone yellow pigment C or the isoindoline yellow pigment E is preferably larger than that of the phthalocyanine blue pigment B. By setting it as such a compounding ratio, the improvement effect of the adhesiveness with respect to a base material can be heightened more.

  The primer can contain other colorants as long as the problem can be solved. The blackness and the like can be adjusted by blending other colorants. Other colorants are, for example, combinations of quinacridone purple pigments A, phthalocyanine blue pigments B, isoindolinone yellow pigments C and isoindoline yellow pigments E, as long as they are combinations. Other pigments include, for example, insoluble azo pigments, condensed azo pigments, anthraquinone pigments, perylene pigments, dioxazine pigments, and dyes. 10 mass% or less is preferable in 100 mass% of coloring agents, and, as for content of another coloring agent, 5 mass% or less is more preferable.

The colorant is preferably subjected to dispersion treatment simultaneously with, or together with, other materials (resin, curing agent) to produce a dispersion. This further improves the dispersion stability of the colorant in the primer. Moreover, a dispersing agent can be used for dispersion | distribution other than another material.
The dispersant includes, for example, a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, a high molecular weight unsaturated acid ester, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic surfactant, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate, polyoxyethylene Nonyl phenyl ether, stearyl amine acetate, etc. are mentioned.
Dispersion processing uses beads (grind media) such as glass beads or zirconia beads, and dispersion is performed using the energy of collision or shear between beads, and cavitation due to shear force or pressure change of stirring. A known dispersing device such as a so-called medialess dispersing machine, which disperses using cavitation due to ultrasonic vibration, can be used.

The primer of the present specification can further contain fine particles (organic particles, inorganic particles). The inclusion of the particles can reduce the tack on the surface of the primer layer.
Further, the fine particles may contain impurities to such an extent that their properties are not impaired. Further, the shape of the fine particles may, for example, be powdery, granular, granular, tabular, fibrous, dendritic or the like.

  Organic particles include, for example, polymer particles such as acrylic resin, polystyrene resin, nylon (registered trademark) resin, melamine resin, guanamine resin, phenol resin, urea resin, silicon resin, etc., or cellulose powder, nitrocellulose powder, wood powder , Waste paper flour, rice husk flour, starch and the like.

  The polymer particles can be synthesized by publicly known polymerization methods such as, for example, emulsion polymerization, suspension polymerization, dispersion polymerization, soap-free polymerization, seed polymerization, and microsuspension polymerization.

  The organic particles are preferably particles having a melting point or softening point of 150 ° C. or higher. When the melting point or the softening point is 150 ° C. or more, it is difficult to be softened by heat at the time of drying the solvent, and the blocking resistance is hardly deteriorated.

  Examples of the inorganic particles include oxides, hydroxides, sulfates, carbonates and silicates of metals such as magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony and titanium. The inorganic particles may be, for example, silica gel, aluminum oxide, calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate, zinc oxide, lead oxide, diatomaceous earth, zeolite, aluminosilicate, in terms of specific compounds. , Talc, white carbon, mica, glass fiber, glass powder, glass beads, clay, wollastonite, iron oxide, antimony oxide, titanium oxide, lithopon, pumice powder, aluminum sulfate, zirconium silicate, barium carbonate, dolomite, molybdenum disulfide And inorganic particles containing iron sand, carbon black and the like.

  Among the fine particles, inorganic particles are preferable because adhesion to a substrate is further improved, and talc, hydrotalcite, mica and kaolin are more preferable.

  The fine particles may be used alone or in combination of two or more.

  The fine particles are preferably contained in an amount of about 1 to 10% by mass in 100% by mass of the nonvolatile matter of the primer.

  The primer contains a solvent. Examples of the solvent include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether and diethylene glycol methyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; tetrahydrofuran, dioxane, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether Ethers; hydrocarbons such as hexane, heptane and octane; aromatics such as benzene, toluene, xylene and cumene; esters such as ethyl acetate and butyl acetate; and the like.

  The solvents may be used alone or in combination of two or more.

  The solvent preferably has a boiling point of 50 ° C to 200 ° C. If the boiling point is in an appropriate range, it is easy to simultaneously achieve the drying property during coating and the surface smoothness of the primer layer.

  The primer of the present specification is, for example, a filler, a thixotropy-imparting agent, an anti-aging agent, an antioxidant, an antistatic agent, a flame retardant, a thermal conductivity improver, a plasticizer, as long as the problems can be solved. It may contain an anti-sagging agent, an antifouling agent, an antiseptic agent, a bactericidal agent, an antifoaming agent, a leveling agent, a thickener, a silane coupling agent and the like.

<Solar cell back surface protection sheet>
The solar cell back surface protection sheet herein comprises a light reflective film and a primer layer. The light reflective film reflects light passing through the primer layer with light that the solar cell module receives and the solar cell element can not use. The reflected light passes through the primer layer and enters the solar cell element, thereby receiving light from the back side in addition to the front side, and the power generation efficiency of the solar cell element is improved.
The primer layer is stacked and crimped so as to be in contact with the back surface sealing material in a heat and pressure bonding process for producing a solar cell module using a surface protection sheet, a surface sealing material, a solar cell element, and a back surface sealing material. It closely adheres to the backside sealing material.

  It is preferable that a light reflective film can reflect the light of the wavelength of 400-1200 nm which a solar cell element can use for electric power generation. For light reflection, for example, it is necessary to blend titanium dioxide having a predetermined average particle diameter, but it is difficult to reflect all of the wavelength region with one type. Therefore, it is preferable to blend two or more types of titanium dioxide having different average particle sizes. In addition, it is preferable that the light reflecting film has a multilayer structure in which one of the two types of titanium dioxide is divided into a first light reflecting film and the other into a second light reflecting film. Alternatively, the film may be foamed instead of, or in combination with, the formulation of titanium dioxide to produce and use a foamed film having a light reflecting function.

  The titanium dioxide is preferably contained in an amount of 5 to 40% by mass in 100% by mass of the light reflective film.

  The base material of the light reflective film is, for example, a polyester resin film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc .; an olefin film such as polyethylene, polypropylene, polycyclopentadiene etc .; polyvinyl fluoride, polyvinylidene fluoride film, poly A fluorine-based film such as a tetrafluoroethylene film, an ethylene-tetrafluoroethylene copolymer film, etc .; an acrylic film; a cellulose-based film such as a triacetyl cellulose film. Among these, a polyester resin film is preferable from the viewpoint of film rigidity and cost, and a polyethylene terephthalate film is more preferable.

  As the substrate, a single layer or a laminate of two or more layers can be used. In addition, the substrate may be configured to include an inorganic layer formed by vapor deposition or sputtering of a metal oxide or a nonmetallic inorganic oxide.

  The thickness of the substrate is preferably 25 to 300 μm.

  The primer layer is preferably used by coating the primer of the present invention on a light reflective film and drying.

  Coating includes, for example, coating devices such as comma coating, gravure coating, reverse coating, roll coating, lip coating, spray coating and the like. Drying includes, for example, hot air drying, an infrared heater, and the like. The drying temperature is usually 80 to 200 ° C.

  The thickness of the primer layer is preferably 0.1 to 30 μm.

  The application of the primer may be performed on another substrate instead of the light reflective film, and the substrate may be bonded to the light reflective film via an adhesive.

  The solar cell back surface protection sheet of the present specification is, for example, a solar cell formed from a crystalline silicon solar cell element, a compound semiconductor typified by copper indium selenide, an element provided with an electrode on a photoelectric conversion layer such as amorphous silicon, It can be used to protect battery modules.

  As a back surface sealing material which comprises a solar cell module, EVA, an olefin film, etc. are mentioned, In order to crosslink the ultraviolet absorber for improving a weather resistance, a light stabilizer, and sealing material itself with these fillers, it is excessive An oxide or the like may be included.

  Next, the durability test of the solar cell and the back surface protection sheet will be described. Although a back surface protection sheet is laminated | stacked with another member and comprises a solar cell module, since a solar cell is used outdoors for several years-several decades, the outstanding durability is requested | required. Although various durability tests are conducted to evaluate this durability, it is required that the back surface protective sheet also does not deteriorate in this durability test.

  As an example of a durability test, a moist heat resistance test which is exposed to an atmosphere of a specific temperature and a relative humidity, a light irradiation test which irradiates ultraviolet light or simulated sunlight, or a high temperature after being exposed to a low temperature Temperature cycle test, etc. which are exposed for a fixed time, and these are repeated alternately.

  Examples of the moisture resistance test include a dump heat test in which the solar cell is exposed to an atmosphere having a temperature of 85 ° C. and a relative humidity of 85%, and a pressure cooker test in which the solar cell is exposed to an atmosphere having a temperature of 105 to 121 ° C. and a relative humidity of 100%.

  Generally, each of the above-mentioned durability tests is often carried out alone, but the outdoor environment in which the solar cell module is used is a combination of temperature, humidity, light and temperature cycle, so the heat and humidity resistance is After performing the test, a temperature cycle test may be performed, and a combined test may be performed to repeat it. Rather than each durability test being conducted alone, the combined test is a more severe test because deterioration due to heat, water vapor, light, shrinkage of the material, etc. occurs in a combined manner. Become. A solar cell, a back surface protection sheet, and members used for these are required to maintain performance even after such an endurance test.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by the following examples. In the examples, “parts” indicates parts by mass, and “%” indicates mass%.
Moreover, the glass transition temperature and the hydroxyl value were measured as described below. Moreover, the compounding quantity in a table | surface is a mass part.

<Measurement of glass transition temperature (Tg)>
The measurement of the glass transition temperature was determined by the differential scanning calorimetry (DSC) method described above.
In addition, the sample for Tg measurement used what heated and dried the resin solution to measure at 150 degreeC for about 15 minutes.

<Measurement of hydroxyl value (OHV)>
Approximately 1 g of a sample is accurately weighed into a stoppered Erlenmeyer flask, and 100 ml of a mixed solution of toluene / ethanol (volume ratio: toluene / ethanol = 2/1) is dissolved. Furthermore, exactly 5 ml of an acetylating agent (a solution in which 25 g of acetic anhydride was dissolved in pyridine to make a volume of 100 ml) was added and stirred for about 1 hour. To this, add phenolphthalein test solution as an indicator and hold for 30 seconds. It is then titrated with 0.5 N alcoholic potassium hydroxide solution until the solution is pinkish.
The hydroxyl value was determined by the following formula. The hydroxyl value is a numerical value of the dry state of the resin (unit: mg KOH / g).
Hydroxyl value (mg KOH / g)
= [{(B-a) x F x 28.05} / S] / (non-volatile content concentration / 100) + D
However, S: amount of sample collected (g)
a: Consumption of 0.5 N alcoholic potassium hydroxide solution (ml)
b: Consumption of empty 0.5N alcoholic potassium hydroxide solution (ml)
F: Titer of 0.5 N alcoholic potassium hydroxide solution D: Acid value (mg KOH / g)

<(Meth) acrylic resin R1 solution>
50 parts of toluene and 50 parts of methyl ethyl ketone were charged into a four-necked flask equipped with a condenser, a stirrer, a thermometer, and a nitrogen introducing pipe, and the temperature was raised to 100 ° C. under a nitrogen atmosphere while stirring. Next, a monomer mixed solution containing 10 parts of methyl methacrylate, 15 parts of cyclohexyl methacrylate, 71 parts of n-butyl methacrylate, 2 parts of glycidyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, and 0.25 parts of azobisisobutyronitrile is added dropwise. Was added dropwise over 2 hours. Subsequently, the polymerization reaction was carried out while adding 0.25 parts of azobisisobutyronitrile in three portions over 3 hours, and the reaction was further carried out for 1 hour. Thereafter, 0.03 parts of hydroquinone, 0.8 parts of dimethylbenzylamine and 1 part of acrylic acid were added, and the mixture was heated and stirred at 100 ° C. for 15 hours. The sample was sampled to confirm that the acid value was 2 or less, and the reaction was completed. Next, cooling is performed, and the (meth) acrylic resin R1 having an acryloyl group in a side chain having a weight average molecular weight of 84,000, a hydroxyl value of 17.0 (mg KOH / g), a Tg of 36 ° C. and a nonvolatile content of 50%. A solution was obtained.

<(Meth) acrylic resin R2 solution>
50 parts of toluene and 50 parts of methyl ethyl ketone were charged into a four-necked flask equipped with a condenser, a stirrer, a thermometer, and a nitrogen introducing pipe, and the temperature was raised to 100 ° C. under a nitrogen atmosphere while stirring. Next, a monomer mixed solution containing 98 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate and 0.5 parts of azobisisobutyronitrile was added dropwise over 2 hours using a dropping funnel. Subsequently, a polymerization reaction was carried out while adding 0.25 parts of azobisisobutyronitrile in three portions over 3 hours, and the reaction was further carried out for 1 hour. After completion of the reaction, the reaction solution was cooled to obtain a (meth) acrylic resin R2 solution having a weight average molecular weight of 38,000, a hydroxyl value of 8.2 (mg KOH / g), a Tg of 19 ° C. and a nonvolatile content of 50%.

<(Meth) acrylic resin R3 solution>
50 parts of toluene and 50 parts of methyl ethyl ketone were charged into a four-necked flask equipped with a condenser, a stirrer, a thermometer, and a nitrogen introducing pipe, and the temperature was raised to 100 ° C. under a nitrogen atmosphere while stirring. Next, a monomer mixture containing 5 parts of methyl methacrylate, 10 parts of cyclohexyl methacrylate, 65 parts of n-butyl methacrylate, 15 parts of t-butyl methacrylate, 5 parts of 2-hydroxyethyl methacrylate, and 0.25 parts of azobisisobutyronitrile It dripped over 2 hours using the dropping funnel. Subsequently, a polymerization reaction was carried out while adding 0.25 parts of azobisisobutyronitrile in three portions over 3 hours, and the reaction was further carried out for 1 hour. After completion of the reaction, the reaction solution was cooled to obtain a (meth) acrylic resin R3 solution having a weight average molecular weight of 81,000, a hydroxyl value of 22.2 (mg KOH / g), a Tg of 51 ° C. and a nonvolatile content of 50%.

<(Meth) acrylic resin R4 solution>
50 parts of toluene and 50 parts of methyl ethyl ketone were charged into a four-necked flask equipped with a condenser, a stirrer, a thermometer, and a nitrogen introducing pipe, and the temperature was raised to 100 ° C. under a nitrogen atmosphere while stirring. Next, a monomer mixed solution containing 40 parts of methyl methacrylate, 56 parts of n-butyl methacrylate, 4 parts of 2-hydroxyethyl methacrylate and 1.0 part of azobisisobutyronitrile was added dropwise over 2 hours using a dropping funnel. Subsequently, a polymerization reaction was carried out while adding 0.25 parts of azobisisobutyronitrile in three portions over 3 hours, and the reaction was further carried out for 1 hour. After completion of the reaction, the reaction solution was cooled to obtain a (meth) acrylic resin R4 solution having a weight average molecular weight of 19,000, a hydroxyl value of 16.3 (mg KOH / g), a Tg of 62 ° C. and a nonvolatile content of 50%.

Table 1 shows a list of weight average molecular weights, OH numbers and Tg (° C.) of (meth) acrylic resins R1 to R4.

In addition, the abbreviated notation in Table 1 shows the following.
MMA: methyl methacrylate CHMA: cyclohexyl methacrylate HEMA: 2-hydroxyethyl methacrylate GMA: glycidyl methacrylate n-BMA: n-butyl methacrylate t-BMA: t-butyl methacrylate

<Polyester resin P1 solution>
31 parts of terephthalic acid, 31 parts of isophthalic acid, 5 parts of adipic acid, 24 parts of ethylene glycol in a polymerization tank of a polymerization reaction apparatus equipped with a polymerization tank, a stirrer, a thermometer, a water separator, a reflux condenser, and a nitrogen introducing pipe. 9 parts of neopentyl glycol was charged into a polymerization tank, and the mixture was heated to 160 to 240 ° C. with stirring under a nitrogen stream to carry out a transesterification reaction. Then, the pressure in the polymerization vessel was gradually reduced to 1 to 2 Torr, and when the viscosity reached a predetermined viscosity, the reaction under reduced pressure was stopped, and the weight average molecular weight was 67,000, and the hydroxyl value was 7.8 (mg KOH / g), A polyester polyol having a Tg of 25 ° C. was obtained and diluted with ethyl acetate to obtain a polyester resin P1 solution having a nonvolatile content of 40%.

<Isocyanate curing agent N1 solution>
A 75% non-volatile solution of isocyanurate of hexamethylene diisocyanate blocked with 3,5-dimethylpyrazole was used as the isocyanate curing agent N1 solution.

<Primer solutions 1 to 17>, <primer solutions 101 to 110>,
Resin, curing agent, coloring agent, dibutyltin dilaurate are blended so as to obtain the nonvolatile content ratio shown in Table 2 and Table 3, and the coloring agent is uniformly dispersed by dispersing the beads using glass beads and diluting with methyl ethyl ketone The primers 1 to 17 and 101 to 110 having a nonvolatile content of 40% were prepared.

Example 1
Using the obtained primer solution 1, a primer layer is formed on the polyester film by the method described later, and the peel strength between the primer layer and the vinyl acetate-ethylene copolymer film (hereinafter EVA film) and the composite durability test The peel strength was evaluated. Moreover, evaluation of the blackness degree of the external appearance of the polyester film in which the primer layer was formed was performed.

<Peeling strength (after initial and combined durability test)>
The initial peel strength and the peel strength after the composite durability test were determined according to the following procedure, and evaluated according to the following criteria.
The obtained primer solution 1 was applied to a corona-treated surface of a 188 μm-thick white polyester film by a gravure coater, and the solvent was dried at 100 ° C. for 1 minute to form a primer layer having an application amount of 5 g / square meter. Over the primer layer, EVA film (Ultra Pearl PV-45 FR00S, Sanvik Co., Ltd.) and a white sheet glass plate are stacked, and the laminate is heated to 140 ° C. on the hot plate of a module laminator PVL0505S (Nisshinbo Mechatronics, Inc.) It was placed with the white glass plate at the bottom, evacuated to about 1 Torr, and left for 5 minutes. Next, while maintaining the temperature at 140 ° C., the sample was pressed at atmospheric pressure and left for 15 minutes to prepare a measurement sample.
Next, the polyester film surface of the measurement sample was cut with a cutter to a width of 15 mm to reach a white sheet glass plate, and the initial peel strength between the primer layer and the EVA film was measured.
Separately, a pressure cooker test was conducted for 24 hours by exposing the measurement sample to an atmosphere with a temperature of 121 ° C. and a relative humidity of 100% using an advanced accelerated life test apparatus (EMD-211MD) manufactured by ESPEC. Thereafter, the measurement sample was exposed to an environment at a temperature of −40 ° C. for 30 minutes, and then exposed to an environment at a temperature of 85 ° C. for 30 minutes. Thereafter, the temperature cycle test was repeated 200 cycles of exposure to the environment at a temperature of -40 ° C for 30 minutes and alternating exposure to the low temperature and the high temperature environment for 30 minutes. Counting that the composite durability test was conducted once by performing 24 hours of this pressure cooker test and 200 cycles of the temperature cycle test, the primer layer and the EVA film after performing the composite durability test once, twice and three times The peel strength of was measured in the same manner as described above.
For the measurement, a 180 degree peel test was performed at a load speed of 100 mm / min using a tensile tester. The obtained measured values were evaluated as follows.
S: 50 N / 15 mm or more Excellent A: 40 N / 15 mm or more and less than 50 N / 15 mm Good B: 30 N / 15 mm or more and less than 40 N / 15 mm Practical range C: 30 N / 15 mm or less Practically not possible The evaluation of the peel strength after the evaluation judged that the adhesion to the substrate after the durability test was good as B or more.

<Evaluation of reflectance (initial and after leaving the coating solution at 50 ° C for 2 months)
The obtained primer solution 1 was applied to a corona-treated surface of a 188 μm-thick white polyester film by a gravure coater, and the solvent was dried at 100 ° C. for 1 minute to form a primer layer having an application amount of 5 g / square meter. The reflectance of the obtained film is measured from the primer layer side using a UV-visible spectrophotometer V-570 manufactured by JASCO Corporation, the reflectance in the range of 380 nm to 780 nm is measured at 2 nm intervals, and the average reflectance is I asked.
Separately, after the primer solution 1 thus obtained was left to stand in a thermostat at 50 ° C. for 2 months, a primer layer was formed in the same manner, coated on a corona-treated surface of a white polyester film, and the average reflectance was determined.
A: Average reflectance less than 15% Good B: Average reflectance 15% or more and less than 30% Practical range C: Average reflectance 30% or more Not practical

<Blackness visual evaluation of appearance>
The coating film was visually observed about the sample by which determination was A in the above-mentioned <reflectance evaluation>, and blackness was evaluated by the following four steps. In addition, about Example 3 grade | etc., Although it says that it is inferior to following A, it has shown black.
EX: Very good blackness S: Good blackness AA: Very good blackness A: There is blackness

[Examples 2 to 17], [Comparative Examples 101 to 110]
The primer solutions 2 to 17 and 101 to 110 were evaluated in the same manner as in Example 1 to obtain Examples 2 to 17 and Comparative Examples 101 to 110, respectively. The results are shown in Tables 2 and 3. In addition, it is exfoliating between the primer layer and the polyester film layer, and the sample in which all became the C evaluation by peeling strength falling after a composite durability test is peeling, and the adhesiveness to a base material is falling. I understood.

  The examples using the primer of the present invention are found to be excellent in reflectance and initial peel strength, peel strength after a composite durability test, storage stability, and blackness in appearance.

  In Comparative Example 101, the content of quinacridone purple pigment A in 100% by mass of the colorant in the primer layer is less than 40%, and the adhesion to the substrate after the durability test is inferior, and Comparative Example 102 is quinacridone purple Since the content of the pigment A exceeds 80%, the adhesion to the substrate after the durability test is inferior.

  In Comparative Example 103, since the content of phthalocyanine blue pigment B is less than 10%, the adhesion to the substrate after the durability test is inferior, and in Comparative Example 104, the content of phthalocyanine blue pigment B exceeds 40%. Therefore, the adhesion to the substrate after the durability test is poor.

  Since the content of the isoindolinone yellow pigment C is less than 10% in Comparative Example 105, the adhesion to the substrate after the durability test is inferior, and the content of the isoindolinone yellow pigment C in Comparative Example 106 is low. Since it exceeds 40%, the adhesion to the substrate after the durability test is inferior.

  In Comparative Example 107, since the content of the colorant in the primer layer was less than 10%, the degree of blackness of the appearance was low, and the adhesion to the substrate after the durability test was also reduced. In Comparative Example 108, the content of the colorant in the primer layer was greater than 40%, and the adhesion to the substrate was reduced after the durability test.

  In Comparative Example 109, the adhesion to the substrate was reduced after the durability test. Moreover, the blackness of the coating film created after leaving a coating liquid to stand for two months at 50 degreeC worsens, and it is inferior to the storage stability of a coating liquid.

  In Comparative Example 110, carbon black is used as a colorant for the primer layer, so the blackness of the appearance is excellent, but the adhesion to the substrate after the durability test is inferior.

Claims (6)

A primer used to form a light reflective film, and a primer layer for a solar cell back surface protection sheet comprising the primer layer,
Contains resin, hardener, and colorant,
10 to 40% by mass of the colorant in 100% by mass of the nonvolatile matter of the primer,
In 100% by mass of the colorant,
40 to 80% by mass of quinacridone purple pigment A,
10 to 40% by mass of a phthalocyanine-based blue pigment B, and 10 to 40% by mass in total of a yellow pigment selected from the group consisting of an isoindolinone-based yellow pigment C and an isoindoline-based yellow pigment E
Primer.   The primer according to claim 1, comprising a total of more yellow pigments selected from the group consisting of isoindolinone yellow pigments C and isoindoline yellow pigments E than phthalocyanine blue pigments B in total. What is claimed is: 1. A sheet for protecting a back surface of a solar cell comprising a light reflective film and a primer layer, wherein
The primer layer contains a resin, a curing agent, and a colorant,
10 to 40% by mass of the colorant in the primer layer,
In 100% by mass of the colorant,
40 to 80% by mass of quinacridone purple pigment A,
10 to 40% by mass of phthalocyanine blue pigment B, and 10 to 40 parts by mass in total of yellow pigment selected from the group consisting of isoindolinone yellow pigment C and isoindoline yellow pigment E
Solar cell back surface protection sheet.   The solar cell back surface protection sheet according to claim 3, wherein the primer layer is located on one surface.   The sheet | seat for solar cell back surface protection of Claim 3 or 4 in which a primer layer is located other than a surface.   A solar cell comprising a surface protection member, a surface side sealing agent, a power generation cell, a back surface side sealing agent, and a back surface protection member formed of the solar cell back surface protection sheet according to any one of claims 3 to 5. module.