JP6090157B2 - Easy-adhesive back surface protection sheet and solar cell module using the same - Google Patents

Description

  The present invention relates to an easily-adhesive back surface protective sheet excellent in adhesiveness and blocking resistance with an ethylene-vinyl acetate copolymer (EVA) and a polyethylene-based resin used as a sealing material in a solar cell module, and It is related with the solar cell module provided with the back surface protection sheet.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. In general, a solar cell module constituting a solar cell has a structure in which each member of a transparent front substrate, a front surface side sealing material, a solar cell element, a back surface side sealing material, and a back surface protection sheet is laminated in order from the light receiving surface side. And has a function of generating electric power when sunlight enters the solar cell element.

  The back surface protection sheet has a role of preventing moisture (water vapor) from entering the back surface side sealing material. Therefore, high adhesion is provided between the laminated back surface protection sheet and the back surface side sealing material. It is required that the adhesive part and the bonded part have high durability.

  As a sealing material used for a solar cell module, ethylene-vinyl acetate copolymer resin (EVA) is most commonly used from the viewpoints of workability, workability, manufacturing cost, etc. Yes. In addition, solar cell module sealing materials using polyethylene-based resins such as linear low density polyethylene (LLDPE) instead of EVA resins are increasingly used.

  As a method for integrating the members including the back surface protective sheet in the manufacturing process of the solar cell module, a method of integrating by vacuum heat laminating can be mentioned. Upon integration by such a method, in order to improve the adhesion between the back surface protective sheet and the sealing material, a fluoropolymer, particularly a fluoropolymer (4) containing a tetrafluoroethylene-based curable functional group is provided on one surface. Back surface protective sheet (refer to Patent Document 1) whose adhesion is improved by forming a coating film (primer layer) with a fluororesin), or a mixture of an acrylic resin, a silane coupling agent, and a polyisocyanate curing agent Although the back surface protection sheet (refer patent document 2) which improved adhesiveness by forming the coating film which consists of these is disclosed, all of these presuppose the use of EVA as a sealing material, such as LLDPE It did not have sufficient adhesiveness to the sealing material made of polyethylene resin.

  On the other hand, the primer layer in the back surface protective sheet is exposed on the outermost surface as a product before lamination as a solar cell module. For this reason, blocking resistance which is not required in a normal adhesive layer is required, but in this respect, not only when using polyethylene-based resin as a sealing material, but also when using EVA, high adhesiveness is required. However, the present situation is that there is no backsheet having preferable blocking resistance.

JP 2010-45376 JP 2006-320991 A

  This invention is made | formed in view of the above situations, and has the high adhesiveness between sealing materials, The back surface side sealing material for solar cell modules which consists of EVA and a polyethylene-type resin, To provide an easily adhesive back surface protection sheet for solar cell modules that can withstand use in harsh environments over a long period of time and has excellent blocking resistance. Objective.

  As a result of intensive studies to solve the above problems, the present inventors have found that a crosslinkable resin in which a crosslinkable main resin is cross-linked with a polyisocyanate compound on one surface of a back protective sheet, and an organometallic coordination compound By providing an easy-adhesion layer (primer layer) containing, the adhesiveness between the back surface protective sheet and the sealing material can be increased, and between the sealing material made of EVA and polyethylene resin It has been found that the backside protective sheet can be remarkably enhanced in adhesion and can be further improved in blocking resistance, and the present invention has been completed. Specifically, the present invention provides the following.

(1) An easy-adhesion layer is formed on one side of a back surface protection sheet for a solar cell module composed of one or a plurality of layers. The easy-adhesion layer is composed of a) a crosslinkable main resin and b) a polyisocyanate compound. A cross-linked cross-linked resin, and c) an organometallic coordination compound , wherein an NCO / OH ratio, which is a ratio of the b) NCO value of the polyisocyanate compound and the a) OH value of the cross-linkable main resin, The easily adhesive back surface protection sheet which is 0.3 or more and 10.0 or less .

  (2) The content of the organometallic coordination compound is 0.1% by mass or more and 7% by mass or less based on the total amount of the a) crosslinkable main resin and the b) polyisocyanate compound. The easy-adhesive back surface protective sheet described in the above).

( 3 ) The easy-adhesion layer does not contain a color pigment, and the NCO / OH ratio, which is the ratio of the bco) NCO value of the polyisocyanate compound and the a) OH value of the crosslinkable main resin, is 0.00. The easily adhesive back surface protection sheet according to (1) or (2) , which is 3 or more and 5.0 or less.

( 4 ) The easy-adhesion layer contains a color pigment, and an NCO / OH ratio, which is a ratio of b) the NCO value of the polyisocyanate compound and a) the OH value of the crosslinkable main resin, is 0.5. The easily adhesive back surface protection sheet according to (1) or (2) , which is 10.0 or more and 10.0 or less.

( 5 ) The easy adhesion layer according to any one of (1) to ( 3 ), wherein the easy adhesion layer contains no color pigment and contains an inorganic filler other than the color pigment. Back protection sheet.

( 6 ) The easily adhesive back surface protection sheet as described in ( 5 ) which contains the said inorganic filler 1.0 mass% or more and 35.0 mass% or less with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound.

( 7 ) The easily adhesive back surface protective sheet according to ( 5 ) or ( 6 ), wherein the inorganic filler is hydrophobic silica.

( 8 ) The easy-adhesive back surface protective sheet according to any one of (1) to ( 7 ), wherein the easy-adhesion layer further contains d) a silane coupling agent.

( 9 ) The d) silane coupling agent is contained in an amount of 0.1% by mass to 10% by mass with respect to the total amount of the a) crosslinkable main component resin and the b) polyisocyanate compound, ( 8 ) The easily adhesive back surface protection sheet as described in 1.

( 10 ) The easily adhesive back surface protective sheet according to any one of ( 8 ) and ( 9 ), wherein the cross-linked resin is a urethane resin, and the easy adhesive layer is formed on a polypropylene resin substrate of the back surface protective sheet. .

( 11 ) The easy-adhesiveness according to any one of ( 8 ) and ( 9 ), wherein the a) crosslinkable main component resin is a crosslinkable substituent-containing acrylic resin, and the glass transition point thereof is 25 ° C or higher and 70 ° C or lower. Back protection sheet.

( 12 ) Further, d) the easy-adhesion layer containing a silane coupling agent is formed on a hydrolysis-resistant polyethylene terephthalate resin substrate, and b) the NCO value of the polyisocyanate compound and the a) cross-linking. The NCO / OH ratio, which is the ratio of the OH value of the main resin, is 1.2. The easy-adhesive back surface protection sheet according to (8), which is 2.5 or more.

( 13 ) In the solar cell module in which the easily adhesive back surface protective sheet according to any one of (1) to ( 12 ), the sealing material, and the solar cell element are integrated at least, the easy adhesive layer is The solar cell module in which the said easily-adhesive back surface protection sheet and the said sealing material containing ethylene-vinyl acetate copolymer resin (EVA) are integrated.

( 14 ) In the solar cell module in which the easily adhesive back surface protective sheet according to any one of ( 8 ) to ( 12 ), the sealing material, and the solar cell element are integrated at least, the easy adhesive layer is The solar cell module by which the said easily-adhesive back surface protection sheet and the said sealing material containing polyethylene-type resin are integrated.

( 15 ) Silane copolymer obtained by copolymerizing the encapsulant as a comonomer with a low density polyethylene having a density of at least 0.900 g / cm ³ and / or a linear low density polyethylene and an ethylenically unsaturated silane compound. ( 14 ) The solar cell module according to ( 14 ), which is a sealing material containing a polyethylene-based resin comprising a coalescence.

  According to the present invention, the back surface protection for solar cell modules that exhibits extremely high adhesiveness and is also excellent in blocking resistance, particularly with the back surface side sealing material for solar cell modules made of EVA or polyethylene resin. A sheet and a solar cell module using such a back surface protection sheet are provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention.

  A specific embodiment of the present invention will be described. This embodiment is an easily adhesive back surface protective sheet having an easy adhesive layer and a solar cell module in which the easily adhesive back surface protective sheet is used. The feature of the present invention is that the easy-adhesive back surface protective sheet has an extremely high adhesiveness especially with the sealing material made of EVA or polyethylene resin constituting the solar cell module, through the easy-adhesive layer. Furthermore, it is also excellent in blocking resistance.

<Easily adhesive back protection sheet>
The easily adhesive back surface protection sheet which is this embodiment is demonstrated. The easily adhesive back surface protection sheet of this embodiment consists of a back surface protection sheet base material layer and the easy adhesion layer formed in the surface of the single side | surface side of this back surface protection sheet base material layer.

[Configuration of easy-adhesion layer]
The easy adhesion layer is a so-called primer layer, and is formed as a cross-linked resin of a polyisocyanate compound on at least one outermost surface of the back surface protection sheet. This easy-adhesion layer comprises a coating liquid comprising a mixture containing a) a crosslinkable main resin (hereinafter also simply referred to as “main resin”), b) a polyisocyanate compound, and c) an organometallic coordination compound. The film is applied to the surface of the film, and a film is formed from the applied coating liquid.

  The coating liquid contains a main resin, a curing agent containing a polyisocyanate compound, and an organometallic coordination compound, and optionally contains a solvent and other various additives. Other additives that can be optionally added to make the easily adhesive back surface protective sheet of the present invention more preferable include inorganic fillers and d) silane coupling agents. Here, the main resin is cross-linked and polymerized by reacting with the polyisocyanate compound. About a main ingredient and a hardening | curing agent, it is preferable that they are a 2 liquid type which mixes these just before use. The polyisocyanate compound is a compound containing a plurality of isocyanate groups in one molecule.

[A) Crosslinkable main resin
As what can be used as the crosslinkable main resin, for example, a crosslinkable substituent-containing acrylic resin, or a polyol compound, a crosslinkable substituent-containing urethane resin, a crosslinkable substitution-containing fluororesin, a crosslinkable substituent-containing vinyl resin, Examples thereof include crosslinkable substituent-containing olefin resins. In the case where the cross-linked resin is a cross-linked acrylic resin, for example, the main resin is a cross-linkable substituent-containing acrylic resin, and the cross-linked acrylic resin is obtained by reacting this with a polyisocyanate compound. When the cross-linked resin is a cross-linked urethane resin, for example, the main resin is a polyol, and a cross-linked urethane resin is obtained by a reaction between this and a polyisocyanate compound (conceptually including a urethane prepolymer terminated with an isocyanate group). In the following description of the present specification, the resin compound before being cured by being crosslinked with a polyisocyanate compound is referred to as “crosslinkable main resin (or simply main resin)”, and is a resin contained in the easy-adhesion layer, that is, cured. Thus, it is distinguished from the resin having the easy-adhesion layer formed. Hereinafter, each constituent material will be described.

[Crosslinkable substituent-containing acrylic resin]
A crosslinkable substituent-containing acrylic resin (hereinafter also simply referred to as “acrylic resin”) as an example of the main resin will be described. The acrylic resin used as the main resin has a plurality of crosslinkable substituents for reacting with the polyisocyanate compound, and is cured by reacting with the polyisocyanate compound to form a firm film. Here, examples of the crosslinkable substituent include a hydroxyl group, an amino group, and a carboxyl group. The main resin is selected from a solvent-soluble resin or a resin dispersible in a solvent. From the viewpoint of availability and crosslinking reactivity, the crosslinkable substituent is preferably a hydroxyl group. A preferred hydroxyl value range is from 5 to 100.

  As the acrylic resin, one or two or more kinds of acrylic acid compound and a monomer having a crosslinkable substituent, one or two or more kinds of acrylic acid compound and a monomer having a crosslinkable substituent, Those obtained by copolymerizing one or more ethylenic monomers are used. Here, in addition to the above monomer, a monomer having a substituent for imparting light resistance to the acrylic resin may be used as a monomer used for obtaining the acrylic resin.

  Such acrylic resins include (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxy-3-phenoxypropyl, ethylene glycol mono (meth) ) (Meth) acrylic compounds having hydroxyl groups such as acrylate and propylene glycol mono (meth) acrylate, and (meth) acrylic acid or alkyl groups as methyl, ethyl, n-propyl, i-propyl, n- Examples include those obtained by copolymerizing an alkyl (meth) acrylate monomer having a butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, or the like. Further, as a monomer used for copolymerization, (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide (alkyl groups include methyl group, ethyl group, n -Propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group and the like), N-alkoxy (meth) acrylamide, N, N-di Alkoxy (meth) acrylamide (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), amide group-containing monomers such as N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide, Contains glycidyl groups such as glycidyl (meth) acrylate and allyl glycidyl ether Monomer, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itaconic acid monoester, (meth) acrylonitrile, chloride Various compounds having an ethylenically unsaturated bond such as vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene may be used. Among these, a copolymer of methyl (meth) acrylate and 2-ethylhexyl acrylate, a copolymer of at least methyl (meth) acrylate, 2-ethylhexyl acrylate, and a hydroxyl group-containing (meth) acrylate is preferably used. Is done. Moreover, 1000-300,000 is mentioned as a preferable mass mean molecular weight of such resin.

  Conventionally, in a primer application using an acrylic resin, from the viewpoint of blocking resistance, the glass transition point (Tg) of the acrylic resin is preferably 50 ° C. or higher, and if the Tg is less than 50 ° C., there is adhesiveness. Since blocking resistance fell, it was not preferable. However, when a silane coupling agent and an organometallic coordination compound are used in combination for forming an easy adhesion layer, an acrylic resin having a lower Tg, for example, Tg of less than 50 ° C., is used for forming the easy adhesion layer. Even if it is a case where is used as main ingredient resin, a preferable back surface protection sheet provided with sufficient blocking resistance can be manufactured. In the present invention, the Tg of the acrylic resin is preferably 25 ° C. or higher and 70 ° C. or lower, and more preferably 30 ° C. or higher and 70 ° C. or lower. When Tg is less than 25 ° C., even if a silane coupling agent and an organometallic coordination compound are used in combination, the blocking resistance is lowered, which is not preferable. On the other hand, when Tg exceeds 70 ° C., the adhesiveness is lowered, which is not preferable.

[Crosslinked urethane resin]
The main resin when the crosslinked resin is a crosslinked urethane resin will be described. In this case, the main resin has a plurality of hydroxyl groups for reacting with the polyisocyanate compound, and reacts with the polyisocyanate compound to be cross-linked to be cured to form a strong film. The main resin is selected from a solvent-soluble resin or a resin dispersible in a solvent. A conventional polyol compound can be used as the main resin. For example, polyether type polyol, polyester type polyol, polycarbonate type polyol, etc. are mentioned, and it is used individually or in multiple types. Of these, polycarbonate polyols are preferably used, and polycarbonate polyols that are liquid at room temperature are particularly preferred. Since it has an active hydrogen group as a reactive group in the urethane bond, it can be crosslinked with a lower hydroxyl value compared to other resins. A preferred hydroxyl value range is from 0 to 50.

  Furthermore, polyamines, polyamine alkylene oxide adducts, amide group-containing polyols, polycarboxylic acids, and the like may be contained within a range not departing from the spirit of the present invention. Examples of the polyamine include alicyclic polyamines such as ethylenediamine, toaminomethyl) cyclohexane, 4,4′-, 2,4′- or 2,2′-dicyclohexylmethanediamine, isophoronediamine, norbornanediamine, m- or p-xylyl. Range amines, araliphatic polyamines such as 1,3- or 1,4-tetramethylxylylenediamine, 2,4- or 2,6-tolylenediamine, 4,4'-, 2,4'- or 2 An aromatic polyamine such as 2,2'-diaminodiphenylmethane can be exemplified. Examples of the amide group-containing polyol include hydroxyalkylamides. Examples of the polycarboxylic acid include isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylene dicarboxylic acid, trimellitic acid, pyromellitic acid and other aromatic polycarboxylic acids, 1,3-cyclohexanedicarboxylic acid, 1 Aliphatic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and aliphatic polycarboxylic acids such as malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid.

  Here, particularly when a polypropylene resin is used as the base material of the back surface protective sheet, sufficient adhesiveness cannot be obtained if the cross-linked resin forming the easy-adhesion layer is a cross-linked acrylic resin. However, high adhesiveness can be obtained by using a crosslinked urethane resin. Thereby, the adhesiveness between the back surface protection sheet which uses a polypropylene resin as a base material, and a back surface side sealing material layer can be provided to an easily bonding layer.

[B] Polyisocyanate compound]
Next, the polyisocyanate compound will be described. A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. As described above, the polyisocyanate compound crosslinks and cures (high molecular weight) the main resin to form a resin contained in the easy adhesion layer. At this time, a polyisocyanate compound becomes a part of resin contained in an easily bonding layer with main ingredient resin. Examples of the polyisocyanate compound include aliphatic, alicyclic, aromatic, and aromatic-aliphatic compounds. The easy-adhesion layer is exposed to the external environment for a long period of time. From the viewpoint of suppressing the accompanying coloring, an aliphatic or alicyclic polyisocyanate compound is preferably used.

  Specific examples of the polyisocyanate compound include aliphatic isocyanates having 3 to 12 carbon atoms such as hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, and lysine diisocyanate; 1,4-cyclohexane diisocyanate, isophorone diisocyanate ( Alicyclic diisocyanates having 5 to 18 carbon atoms such as IPDI); modified products of these diisocyanates (burettes, isocyanurate modified products, etc.). These can be used alone or in combination of two or more. Further, when the crosslinked resin is a crosslinked urethane resin, it may be a urethane prepolymer having an isocyanate group at the terminal.

[C) Organometallic coordination compound]
Next, the organometallic coordination compound will be described. The organometallic coordination compound is also called a chelating agent and is presumed to contribute to curing as a crosslinking agent. In addition, the blocking resistance of the easy adhesion layer can be improved. Further, the adhesive strength is remarkably improved by using it together with a silane coupling agent.

  Examples of organometallic coordination compounds include titanium acetylacetonate, titanium octyl glycolate, titanium triethanolamate, tetra-n-butyl titanate, aluminum acetylacetonate, aluminum bisethylacetoacetate monoacetylacetonate, aluminum isopropylate. Examples thereof include rate monosecondary butyrate, aluminum alkyl acetoacetate diisopropylate, aluminum trisacetylacetonate, zirconium acetylacetonate, and acetylacetone zirconium butyrate. Among these, aluminum trisacetylacetonate can be preferably used from the viewpoint of blocking resistance and adhesiveness with a sealing material.

  Here, an easily bonding layer is located in the surface of the outermost layer of the solar cell module in the side which contact | connects the back surface side sealing material layer of a back surface protection sheet base material layer. The easily adhesive back surface protective sheet is also a product that is distributed independently before being integrated as a solar cell module. Therefore, for smooth distribution and storage, it is preferable that the easy-adhesive layer has blocking resistance when completed as an easy-adhesive back surface protective sheet after crosslinking. Thus, it has not been known in the past that the addition of an organometallic coordination compound is effective in improving blocking resistance, which is an essential requirement unique to an easy-adhesion layer that serves as a primer, and this is also a feature of the present invention. is there.

[Inorganic filler]
In this invention, an inorganic filler can be added as needed. In the present invention, the inorganic filler is not particularly limited, and examples thereof include silica, alumina, zirconium oxide, zinc oxide, antimony trioxide, antimony pentoxide, magnesium oxide, titanium oxide, iron oxide, cobalt oxide, and chromium oxide. And metal oxides such as talc, and metal fine particles such as aluminum, gold, silver, nickel and iron. The average particle size is preferably about 0.1 to 10 μm. You may use these individually or in combination of 2 or more types. In consideration of conditions such as low expansion, high purity being easily obtained, and relatively low cost, silica can be preferably used. Such an inorganic filler mainly contributes to the improvement of the blocking resistance of the easy adhesion layer.

  Among the above inorganic fillers, a filler having a hydrophobic surface is preferable, and an inorganic filler treated with an organosilicon compound is particularly preferable. In particular, by selecting hydrophobic silica, it is possible to further improve the adhesiveness of the easy-adhesion layer as compared with the case of using other inorganic fillers at the same time as improving the blocking resistance. Hydrophobic silica is generally made hydrophobic by bonding a treating agent to silica, which is hydrophilic, and has low hygroscopicity and excellent dispersibility. In the present specification, “hydrophobic silica” refers to silica having a hydrophobic surface and containing an organosilicon compound as a treating agent.

  In particular, when hydrolysis-resistant polyethylene terephthalate (HR-PET) is used as the base material of the back surface protection sheet, it has been difficult to impart sufficient adhesiveness to the back surface protection sheet while the weather resistance has been increased. However, even in such a case, by adding an appropriate amount of hydrophobic silica to the coating liquid that forms the easy-adhesion layer, high adhesion to a sealing material sheet made of EVA or polyethylene-based resin can be imparted. Can do. Therefore, it can be set as the solar cell module which was extremely excellent in a weather resistance and durability as what made HR-PET the base material of a back surface protection sheet, and arrange | positioned such a back surface protection sheet in the outermost layer.

  Here, “hydrolysis-resistant polyethylene terephthalate (HR-PET)” in the present specification is to improve the heat resistance and hydrolysis resistance by greatly reducing the content of low-molecular impurities (oligomers). It is a biaxially stretched polyester film, and refers to polyethylene terephthalate (PET) having a carboxy end group amount of 15 equivalent / ton or less and an oligomer amount of 0.4 mass% or less.

[D) Silane coupling agent
Next, the silane coupling agent will be described. The easy-adhesion layer is required to have high adhesion to the back side sealing material, but in addition to the main resin, curing agent, and organometallic coordination compound, a silane coupling agent may be used in combination. Thereby, the adhesiveness of an easily-adhesive back surface protection sheet and a sealing material can further be improved, and especially the adhesiveness with the sealing material which consists of a polyethylene-type resin can be improved notably. In addition, the blocking resistance of the easy adhesion layer can be improved.

  Examples of the silane coupling agent include amino silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-phenylaminofuropyltrimethoxysilane; ureido systems such as ureidopropyltriethoxysilane. Silane coupling agents; vinyl silane coupling agents such as vinylethoxysilane, vinylmethoxysilane, vinyltris (β-methoxyethoxy) silane; methacrylates such as 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropylmethyldimethoxysilane -Based silane coupling agents; epoxy-based silane coupling agents such as 3-glycidoxypropyltriethoxysilane; and isocyanate-based silane cups such as 3-isocyanatopropyltriethoxysilane Mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane and 6-mercaptohexatrimethoxysilane; methyl / phenyl such as methyl group and phenyl group-containing methoxysilane oligomer Silane coupling agent; polymer type silane coupling agent such as polyethoxydimethylsiloxane and polyethoxydimethylsiloxane; cationic type such as N- (N-benzyl-β-aminoethyl) -3-aminopropyltrimethoxysilane hydrochloride A silane coupling agent etc. are mentioned. Moreover, the alkoxy oligomer which oligomerized the silane coupling agent can also be used. Among these, an isocyanate silane coupling agent, an epoxy silane coupling agent, a mercapto silane coupling agent, and a methyl / phenyl silane coupling agent can be preferably used.

[Other additives]
Other additives are added as necessary to impart weather resistance, light resistance, heat resistance, moisture resistance, flame retardancy, and the like to the easily adhesive layer. Further, the additive is added as necessary to improve the stability, coating property, drying property, blocking resistance and the like of the coating solution.

  In addition, various color pigments are often added mainly from the viewpoint of enhancing the design of the solar cell module. In particular, titanium oxide, calcium carbonate, barium sulfate, which are white pigments, carbon black, which is a black pigment, titanium black, Cu—Mn complex oxide, Cu—Cr—Mn complex oxide, etc. are usually blended. .

[Back protection sheet base material layer]
Next, the back surface protection sheet base material layer which comprises an easily-adhesive back surface protection sheet is demonstrated. A back surface protection sheet base material layer turns into an easily adhesive back surface protection sheet by forming the above-mentioned easy adhesion layer in the surface.

  As the back protective sheet base material layer, a resin sheet obtained by molding a resin into a sheet shape is used. Examples of such resin sheets include polyethylene resins, polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, polyvinyl chloride resins, fluorine Resins, poly (meth) acrylic resins, polycarbonate resins, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polyamide resins such as various nylons, polyimide resins, polyamideimide resins, polyaryls Various resin sheets such as phthalate resin, silicone resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyurethane resin, acetal resin, cellulose resin, etc. It is possible to use. Among these resin sheets, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polycarbonate resin, and polyethylene naphthalate are particularly preferably used. Among them, for example, a biaxially stretched polyethylene terephthalate or a biaxially stretched polypropylene resin film or sheet is particularly preferable.

  In the easily adhesive back surface protective sheet of the present invention, as described above, hydrolysis-resistant polyethylene terephthalate (HR-PET), which is extremely excellent in heat resistance and hydrolysis resistance, is also used as the back surface protection sheet base material layer. can do. In this case, as described above, it is preferable to add hydrophobic silica to the coating solution.

  In this specification, the term “resin sheet” is used as the name of a product obtained by processing these resins into a sheet shape, but this term is used as a concept including a resin film. These may be a single layer or a laminate composed of a plurality of layers laminated with a conventionally known adhesive or the like.

  A light shielding layer can be provided as a layer disposed on the outermost side or the entire outer side in the solar cell module among the surfaces of the back surface protective sheet base material layer. By providing this light-shielding layer, it becomes possible to use a resin sheet having somewhat low light resistance as a substrate from the viewpoint of cost. Examples of such a sheet include aluminum foil, aluminum vapor deposition film, polyethylene terephthalate resin colored in black or white, polypropylene resin, polyethylene resin, and the like.

  Moreover, you may provide the weathering layer which consists of a fluorine film etc. in the outermost layer of a back surface protection sheet. As a specific example, a weather resistant layer is provided by dry laminating a white fluorine film or a white polyester film on the surface opposite to the surface of the base layer provided with the easy-adhesion layer using a urethane-based adhesive. be able to.

  What is necessary is just to determine suitably the thickness of a back surface protection sheet base material layer in consideration of the thickness requested | required of an easily-adhesive back surface protection sheet. As an example, the thickness of the back surface protective sheet base material layer may be 10 to 500 μm, but is not particularly limited.

[Coating solution adjustment]

  The content of the main resin in the coating liquid is preferably 10 to 60% by mass. When the resin content in the coating liquid is 10% by mass or more, the color pigment contained in the coating liquid can be favorably dispersed. Further, when the content of the resin in the coating liquid is 60% by mass or less, the coating property of the coating liquid is improved.

  It is preferable that the usage-amount of a polyisocyanate compound is 0.5-75 mass parts with respect to 100 mass parts of main ingredient resin. When the amount of the polyisocyanate compound used is 0.5 parts by mass or more with respect to 100 parts by mass of the main resin, good curability can be imparted to the coating film formed from the coating liquid. A softness | flexibility can be provided to a coating film by being 75 mass parts or less with respect to a mass part.

  In particular, when a colored pigment is not added in an uncolored system, the amount of the isocyanate compound used is more preferably 1 to 30 parts by mass with respect to 100 parts by mass of the main resin. On the other hand, when a colored pigment is added, it is preferable to increase the amount used in consideration of the isocyanate group consumed in the reaction with other than the main resin due to the reaction with the reactive group on the surface of the colored pigment and the adsorbed moisture. It is preferable that the usage-amount of this isocyanate compound is 1-75 mass parts with respect to 100 mass parts of main ingredient resin.

  The amount of the polyisocyanate compound used is preferably such that the NCO / OH ratio (ratio of NCO number of the curing agent / OH number of the main resin) is from 0.3 to 10. By setting the NCO / OH ratio in the above range, good curability and flexibility can be imparted to the coating film formed from the coating solution in a well-balanced manner, and adhesion, heat resistance and durability, and further, blocking resistance. Can be obtained.

  In particular, when a colored pigment is not added in an uncolored system, the NCO / OH ratio is preferably set to an amount of 0.3 to 5.0, more preferably 0.5 to 2.5. preferable. In particular, when using HR-PET which is extremely excellent in hydrolysis resistance as a base material for the back surface protection sheet but is likely to have insufficient adhesion to other members, the NCO / OH ratio is 1.2 or more and 2.5. By setting it as the following range, the adhesiveness of an easily-adhesive back surface protection sheet can fully be improved. Therefore, a very preferable solar cell module can be formed using such an easily adhesive back surface protective sheet.

  On the other hand, when a color pigment is added to the coating liquid, the amount is preferably such that the NCO / OH ratio is 0.5 or more and 10.0 or less.

  When a solution containing a polyisocyanate compound is used as a curing agent to form a two-component coating liquid, a known organic solvent is appropriately selected and used as the curing agent. Such a solvent will be described later.

  The content of the organometallic coordination compound is preferably 0.1% by mass or more and 7% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less based on the total amount of the main resin and the polyisocyanate compound. is there. When the content of the organometallic coordination compound is less than 0.1% by mass, blocking resistance preferable as a back surface protective sheet for a solar cell module cannot be obtained. Further, even if the content of the organometallic coordination compound exceeds 7% by mass, there is no further improvement in blocking resistance and adhesion, which is not preferable.

  When an inorganic filler is added, its content needs to be set as appropriate depending on the type of filler and the intended use. When the inorganic filler is a filler other than a color pigment, the main resin and the polyisocyanate compound are used. 1.0 to 35.0 mass% is preferable, and more preferably 3.0 to 15.0 mass% with respect to the total amount. For example, when adding hydrophobic silica for the purpose of improving blocking resistance, it is preferable to add the content so that the content is 3.0 or more and 15.0% by mass or less. However, when the inorganic filler to be added is a color pigment, it is not limited to the above range, and even a coating liquid to which a color pigment in an amount exceeding the above range is added can be preferably used.

  Specifically, for example, when a coloring pigment such as titanium oxide is added for the purpose of obtaining a coloring effect in combination with an improvement in blocking property, the content of such a coloring pigment is 0. It is preferably in the range of 1 to 450.0% by mass, and those colored pigments can be preferably used while adjusting the addition amount as appropriate within such a range.

  When the silane coupling agent is added, the content thereof is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, with respect to the total amount of the main resin and the polyisocyanate compound. More preferably, it is 1.0 or more and 8 mass% or less. In particular, when a coloring pigment is added, the amount used may be increased in consideration of the alkoxy group consumed by the reaction with the other than the main resin by the reaction with the surface of the coloring pigment. When the content of the silane coupling agent is less than 0.1% by mass, the adhesiveness required as a back surface protective sheet for solar cell modules is not exhibited. Further, even if the content of the silane coupling agent exceeds 10% by mass, there is no further improvement in adhesion and the coating film becomes brittle, which is not preferable. In addition, it is preferable that ratio of content of an organometallic coordination compound and a silane coupling agent is 25: 75-75: 25.

  Next, the solvent used for the coating liquid will be described. A solvent is added in order to provide the coating liquid with the applicability | paintability with respect to a back surface protection sheet base material layer. After the coating liquid is applied to the back surface protective sheet base material layer, the solvent contained in the applied coating liquid is volatilized, and an easy-adhesion layer is formed on the surface of the back surface protective sheet base material layer by the subsequent curing reaction. .

  The solvent is not particularly limited as long as it can dissolve or disperse components such as the main resin and the polyisocyanate compound and does not react with the polyisocyanate compound contained in the coating liquid. Examples of such solvents include water-insoluble solvents such as toluene, xylene, butyl acetate, and ethyl acetate, and water-soluble solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. A solvent is suitably selected according to the resin component used for a coating liquid, and is used individually or in combination of 2 or more types. Further, in order to adjust the drying speed during coating, a high boiling point solvent such as tripropylene glycol dimethyl ether may be added.

  The coating liquid is prepared by mixing a main resin, a solvent, and necessary additives. Of the components contained in the coating liquid, the silane coupling agent, organometallic coordination compound, and polyisocyanate compound, as already mentioned, in order to avoid reacting with the main resin component during storage, Is preferably used as an additive or curing agent which is a separate solution. In this case, the main agent, the additive, and the curing agent are mixed immediately before use to form a coating liquid.

  What is necessary is just to set the viscosity of a coating liquid suitably according to the coating method of a coating liquid. An example of the viscosity of the coating solution is preferably 10 to 100 cPs, more preferably 50 to 80 cPs. The viscosity of the coating solution may be adjusted by adjusting the amount of solvent added to the coating solution.

[Formation of easy adhesion layer]
Next, a method for forming the easy-adhesion layer by applying the coating liquid on the surface of the back surface protective sheet base material layer will be described. The easy-adhesion layer is formed by applying the coating liquid on the surface of the back protective sheet base material layer to form a coating film, evaporating the solvent contained in the coating film, and then evaporating the main resin and the polymer contained in the coating film. It is formed by cross-linking reaction with an isocyanate compound and curing.

  As a method of applying the coating liquid to the surface of the back surface protective sheet substrate, a conventionally known method can be used without any particular limitation. Examples of such a coating method include a printing method, a coating method using a gravure coater, a roll coating method, a spray coating method, a dip coating method, a solid coating method, and a brush coating method.

  As a method for evaporating the organic solvent contained in the coating film, a conventionally known method can be used without particular limitation. Examples of such an evaporation method include a heating method, a reduced pressure drying method, a hot air drying method, and a natural drying method, but are not particularly limited. The conditions for evaporating the solvent contained in the coating film may be appropriately set according to the solvent used, but the heating time and heating temperature are 15 seconds to 5 minutes when using a gear oven. It is preferably in the range of ~ 200 ° C, more preferably in the range of 70 to 120 ° C for 30 seconds to 2 minutes. By heating in this way, preferable blocking resistance and adhesiveness are exhibited.

  Furthermore, the heating temperature is generally performed at a high temperature of about 120 ° C., but by appropriately selecting the Tg of the crosslinkable main resin used, for example, the drying is performed at a low temperature of about 90 ° C. Processing may be performed. More specifically, a crosslinkable main component resin having a Tg of about 50 ° C. can be preferably used when such a low temperature drying treatment is performed. By selecting a main resin having a Tg of about 50 ° C., the balance between blocking resistance and adhesion can be optimized even when a drying process is performed at a low temperature. By doing in this way, the shrinkage | contraction and deformation | transformation of a resin sheet accompanying a heating operation at high temperature can be reduced, and it can contribute to the improvement of the quality and productivity of a back surface protection sheet. The coating film obtained by evaporating the solvent is subjected to curing for sufficiently carrying out the crosslinking reaction. Curing conditions may be set as appropriate according to the types of the main resin and polyisocyanate compound used. Examples of the curing conditions include leaving at 40 to 60 ° C. for 3 to 7 days.

  When the solvent is removed by evaporation from the coating film, the base resin, the polyisocyanate compound and the additive added to the coating solution remain on the surface of the substrate to form a film. This film is cured to form an easy adhesion layer. The thickness of the easy-adhesion layer is not particularly limited, and may be determined as appropriate according to the conditions to which the easy-adhesive back surface protective sheet is applied. As a thickness of an easily bonding layer, 0.1-30 micrometers is preferable and 0.5-5 micrometers is more preferable. When the thickness of the easy-adhesion layer is 0.1 μm or more, sufficient adhesion can be imparted. If the thickness of an easily bonding layer is 30 micrometers or less, workability with favorable blocking resistance can be provided and cost can also be suppressed.

<Solar cell module>
Next, an example of the solar cell module of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. In the solar cell module 1 of the present invention, the transparent front substrate 2, the front side sealing material layer 3, the solar cell element 4, the back side sealing material layer 5, and the back surface protection sheet 6 are sequentially formed from the incident light receiving surface side. Are stacked. The solar cell module 1 of the present invention uses the above-mentioned easily adhesive back surface protection sheet for the back surface side sealing material layer 5.

  In the solar cell module 1, for example, the transparent front substrate 2, the front-side sealing material layer 3, the solar cell element 4, the back-side sealing material layer 5, and the back protection sheet 6 are sequentially stacked. It can be manufactured by integration by vacuum suction or the like, and then thermocompression-molding the above-mentioned member as an integral molded body by a molding method such as a lamination method.

  Further, the solar cell module 1 is formed on the front side sealing material layer 3 on each of the front side and the back side of the solar cell element 4 by a molding method usually used in ordinary thermoplastic resins, for example, T-die extrusion molding. And the back surface side sealing material layer 5 are melt-laminated to sandwich the solar cell element 4 with the front surface side sealing material layer 3 and the back surface side sealing material layer 5, and then the transparent front substrate 2 and the back surface protection sheet 6. They may be manufactured by a method of sequentially laminating them and then integrating them by vacuum suction or the like and heat-pressing them.

  In the present invention, an easy-adhesion layer is formed on the bonding surface side with the back surface side sealing material layer 5 in the above back surface protection sheet 6, thereby improving the adhesion with the back surface side sealing material. In particular, the adhesion between the sealing material made of EVA or polyethylene resin is significantly improved. Moreover, since this easily adhesive back surface protection sheet is excellent in blocking resistance, it is excellent also in the handling property as a back surface protection sheet before modularization.

  In the solar cell module of the present invention, a sealing material containing EVA resin can be preferably used as the sealing material. By using such a sealing material, adhesion between the sealing material and a member such as a transparent front substrate or a solar cell element can be obtained.

Moreover, in the solar cell module of this invention, the sealing material containing a polyethylene-type resin can be used as a sealing material. The polyethylene resin is not particularly limited as long as the main component is polyethylene, but is preferably low density polyethylene (LDPE), more preferably linear low density polyethylene (LLDPE), and particularly preferably metallocene linear low density polyethylene. is there. Linear low density polyethylene is a copolymer of ethylene and α-olefin. The density of the polyethylene resin used in the present invention is preferably 0.900 g / cm ³ or less, and more preferably in the range of 0.870 to 0.890 g / cm ³ . If it is this range, favorable transparency and heat resistance can be provided, maintaining sheet workability. Further, the melt mass flow rate (MFR) of the polyethylene resin needs to be 1.0 g / 10 min or more and 40 g / 10 min or less at 190 ° C., and preferably 2 g / 10 min or more and 40 g / 10 min or less. . When the MFR is in the above range, the processability during film formation is excellent.

  The polyethylene resin in the present invention includes not only ordinary polyethylene obtained by polymerizing ethylene, but also a resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin, ethylenic resin, etc. Resins obtained by copolymerizing a plurality of different compounds having an unsaturated bond, modified resins obtained by grafting different chemical species to these resins, and the like are included. Especially, the polyethylene-type resin containing the silane copolymer formed by copolymerizing at least (alpha) -olefin and an ethylenically unsaturated silane compound as a comonomer can be used preferably. By using such a resin, adhesion between a sealing material and a member such as a transparent front substrate or a solar cell element can be obtained. Examples of the silane copolymer include those described in JP-A-2003-46105.

  The polyethylene resin composition contains a small amount of a polymerization initiator such as t-butylperoxy 2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. Specifically, it is 0.02 or more and less than 0.5% by mass. Thereby, heat resistance can be imparted without the film forming property being reduced due to the generation of gel during molding, and the transparency being lowered.

  Hereinafter, the present invention will be described more specifically with reference to examples, comparative examples, and reference examples. However, the present invention is not limited to the following examples.

<Manufacture of backside protection sheet>
The coating liquid which forms an easily bonding layer in the easily adhesive back surface protection sheet of each Example, a comparative example, and a reference example was prepared using the following primer materials and solvents.
(Crosslinking main resin)
Crosslinkable main resin 1 (crosslinkable substituent-containing acrylic resin: expressed as “acryl 1” in the table below): Tg 41 ° C., acid value 5.9, hydroxyl value 19, weight average molecular weight 25000.
Crosslinkable main resin 2 (crosslinkable substituent-containing acrylic resin: expressed as “acryl 2” in the following table): Tg 50 ° C., acid value 3.5, hydroxyl value 19, weight average molecular weight 28000.
Crosslinkable main resin 3 (crosslinkable substituent-containing polycarbonate skeleton urethane resin: expressed as “urethane” in the table below): Tg of about 30 ° C., hydroxyl value of 20, number average molecular weight of 15000.
(Polyisocyanate compound)
Polyisocyanate compound 1 (denoted as “crosslinking agent 1” in the following table): (Product name “Coronate HX”, manufactured by Nippon Polyurethane Industry Co., Ltd.)
Polyisocyanate compound 2 (denoted as “crosslinking agent 2” in the table below): (Product name “Duranate TSE100” manufactured by Asahi Kasei Chemicals Corporation)
For the polyisocyanate compounds 1 and 2, the mass ratio with respect to 100 parts by mass of the main resin is the ratio expressed in mass% in the table below, and the NCO / OH ratio is the value expressed in the table below. It mix | blended so that it might become.
(Organic metal coordination compound)
Organometallic coordination compound 1 (aluminum trisacetylacetonate: described as “chelating agent 1” in the table below): (product name “aluminum chelate A (W)”, manufactured by Kawaken Fine Chemical Co., Ltd.)
Organometallic coordination compound 2 (aluminum alkyl acetoacetate / diisopropylate: described as “chelating agent 2” in the table below): (Product name: “Aluminum chelate M: manufactured by Kawaken Fine Chemical Co., Ltd.”)
About the organometallic coordination compounds 1-2, all mix | blended so that the mass ratio with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound might turn into the ratio represented by the mass% in the following table | surface.
(Silane coupling agent)
Silane coupling agent 1 (3-isocyanatopropyltriethoxysilane: written as “Isocyan” in the table below): (Product name “KBE-9007”, manufactured by Shin-Etsu Silicone Co., Ltd.).
Silane coupling agent 2 (mercapto group-containing methoxy / ethoxysilane oligomer: expressed as “mercapto” in the table below): (“product name X-41-1805”, manufactured by Shin-Etsu Silicone Co., Ltd.).
Silane coupling agent 3 (epoxy group-containing methoxy / ethoxysilane oligomer: described as “epoxy” in the table below): (“product name X-41-1053”, manufactured by Shin-Etsu Silicone Co., Ltd.).
Silane coupling agent 4 (methyl and phenyl group-containing methoxysilane oligomer: described as “methyl / phenyl” in the table below): (Product name “X-40-9227”, manufactured by Shin-Etsu Silicone Co., Ltd.)
Silane coupling agent 5: A mixture of the silane coupling agent 2 and the silane coupling agent 3 in a ratio of 1: 1.
About silane coupling agent 1-5, all mix | blended so that the mass ratio with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound might turn into the ratio represented by the mass% in the following table | surface. In Examples 1 to 6 and Comparative Examples 1 to 3 shown in Tables 1 and 2, no silane coupling agent was added.
(Color pigment)
Pigment 1 (carbon black: indicated as “CB” in the table below): (Product name “Special Black 4”, manufactured by Evonik Degussa Japan Co., Ltd.)
Pigment 2 (titanium oxide: expressed as “TiO ₂ ” in the table below): (Product name “Tai Pure R-105”, manufactured by DuPont)
About the pigments 1-2, it mix | blended so that the mass ratio with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound might turn into the ratio represented by the mass% in the following table | surface.
(Inorganic filler)
Inorganic filler 1 (3 μsilica: described as “3 μSi” in the table below): (Product name “Silicia 320”, manufactured by Fuji Silysia Ltd.)
Inorganic filler 2 (hydrophobic silica: described as “hydrophobic Si” in the table below): (product name “Silo Hovic 100”, manufactured by Fuji Silysia Ltd.)
About the inorganic fillers 1-2, it mix | blended so that the mass ratio with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound might turn into the ratio represented by the mass% in the following table | surface.
(solvent)
Mixture of toluene: methyl ethyl ketone = 1: 1

  For each Example, Comparative Example, and Reference Example, the above-mentioned primer material was prepared by blending as described in the following table, and each solvent was added to each Example, Comparative Example, and Reference Example. The coating liquid was adjusted at a solid content concentration of 60% by mass.

(Base material)
PET
A sheet of biaxially stretched polyethylene terephthalate (PET) having a thickness of 188 μm (denoted as “PET” in the table below),
CPP
Alternatively, a sheet obtained by dry laminating a biaxially stretched polyethylene terephthalate (PET) having a thickness of 188 μm and an unstretched polypropylene resin (CPP) having a thickness of 60 μm using a urethane-based adhesive (“CPP” in the table below) Notation),
HR-PET
Hydrolysis-resistant PET (product name “DX10A”, manufactured by Sichuan East Materials Group Co., Ltd.) (denoted as “HR-PET” in the table below)
Are used as the base material of the back surface protection sheet, and the coating liquids adjusted as described above are applied to the surface of the base material of these three kinds of back surface protection sheets (on the CPP side for the back surface protection sheet base material (CPP)). After coating with a bar coater and drying the applied coating solution at a drying treatment temperature of 120 ° C. for 2 minutes, curing was carried out at 40 ° C. for 7 days to form an easy-adhesion layer. Examples, Comparative Examples, and It was set as the back surface protection sheet of the reference example. About the coating amount of each coating liquid, it was as having described with g / m < ² > in the following table | surface. However, in Examples 7 to 12, 23 to 25, and Reference Examples 4 to 5, the drying treatment temperature was 90 ° C. and the drying time was 30 seconds.

<Manufacture of samples for evaluation of adhesiveness and durability>
About each back surface protection sheet of the produced Examples, Comparative Examples, and Reference Examples, the following sealing material sheets 1 to 5 are used for the production of solar cell modules under the following lamination conditions on the surface coated with the coating liquid. The sample was laminated using a vacuum laminator and used as a sample for evaluating adhesiveness and durable adhesiveness.
(Encapsulant sheet)
Encapsulant sheet 1 (EVA (vinyl acetate content 28%, product name “EVAFLEX / EV250 grade”, manufactured by Mitsui DuPont Polychemical)) 100 parts by mass, cross-linking agent (“Lupersol 101”) 1.5 parts by mass, Cross-linking aid (“TAIC”) 0.5 part by mass, antioxidant (“NAUGARD-P”) 0.2 part by mass, UV absorber (“Tinuvin 7709”) 0.1 part by mass and “Cyasorb UV-531” 0.3 wt. Part) was formed to a thickness of 400 μm by the T-die method at a film forming temperature of 90 ° C.): In the table below, expressed as “EVA1”.
Encapsulant sheet 2 (EVA (vinyl acetate content 33%, product name “EVAFLEX / V523 grade”, manufactured by Mitsui DuPont Polychemical))) 100 parts by mass, cross-linking agent (“Lupersol 101”) 1.5 parts by mass, Cross-linking aid (“TAIC”) 0.5 part by mass, antioxidant (“NAUGARD-P”) 0.2 part by mass, UV absorber (“Tinvin 7709” 0.1 part by mass and “Cyasorb UV-531” 0 3 parts by mass) was formed to a thickness of 400 μm by the T-die method at a film forming temperature of 90 ° C.): In the table below, expressed as “EVA2”.
Sealing material sheet 3 (EVA high-speed crosslinking type, thickness 500 μm (product name “S-11”, manufactured by Bridgestone)): Indicated in the table below as “EVA3”.
Sealing material sheet 4 (20 parts by mass of the following silane-modified transparent resin, 5 parts by mass of a weather-resistant masterbatch, and 80 parts by mass of a metallocene linear low-density polyethylene having a density of 0.905 g / cm 3 as an additive polyethylene) The film was formed to a thickness of 400 μm by the T-die method at a film formation temperature of 230 ° C.): Indicated in the table below as “LL1”.
Silane-modified transparent resin: Density is 0.898 g / cm ³ , vinyl is used for 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a melt mass flow rate of 2 g / 10 min at 190 ° C. A silane-modified transparent resin obtained by mixing 2 parts by mass of trimethoxysilane and 0.1 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200 ° C.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and 5 parts by mass of hindered amine light stabilizer with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene with a density of 0.920 g / cm3 Part and 0.5 parts by mass of a phosphorous heat stabilizer are mixed, melted, processed, and pelletized.
Encapsulant sheet 5 (20 parts by mass of the following silane-modified transparent resin, 5 parts by mass of a weather-resistant masterbatch, and 80 parts by mass of a metallocene linear low-density polyethylene having a density of 0.905 g / cm 3 as addition polyethylene) And LLDPE resin having a weak crosslinkability formed by a T-die method at a film formation temperature of 210 ° C. and having a thickness of 400 μm): Indicated in the table below as “LL2”.
Silane modified transparent resin: vinyl trimethoxy with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. 2 parts by mass of silane and 0.1 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed, melted and kneaded at 200 ° C., density 0.884 g / cm ³ , 190 ° C. Silane-modified transparent resin having an MFR of 1.8 g / 10 min.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and hindered amine light stabilizer 5 with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ A master batch in which parts by mass and 0.5 parts by mass of a phosphorous heat stabilizer are mixed, melted, processed, and pelletized.
Polymerization initiator compound resin: t-amyl-peroxy-2-ethylhexyl carbonate with respect to 100 parts by mass of M-LLDPE pellets with a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. Resin impregnated with 1 part by mass and compounded with compound pellets.
(Lamination condition)
EVA 1-3: Lamination was performed under fast cure conditions (denoted as “FC” in the table below) or standard cure conditions (denoted as “SC” in the table below). Under fast cure conditions, pressure bonding is performed with a vacuum laminator at a pressure of 100 kPa at 150 ° C. for 15 minutes. Under standard cure conditions, pressure bonding was performed at 150 ° C. for 15 minutes with a vacuum laminator at a pressure of 100 kPa, and then left at 150 ° C. for 30 minutes in a high temperature layer.
LL1-2: Pressure bonding with a vacuum laminator at a pressure of 100 kPa at 150 ° C. for 15 minutes.

<Test Example 1>
(Evaluation of adhesiveness, durable adhesiveness, and blocking resistance)
The adhesiveness, durable adhesiveness and blocking resistance of the samples for evaluation of adhesiveness and durable adhesiveness using the samples of Examples and Comparative Examples were evaluated. Evaluation was performed based on the numerical value measured by the following method.
[Adhesion test]
For each sample for evaluation, the peel strength (N) was measured for the initial value and the value after carrying out each durability test with a 180-degree peel having a width of 15 mm. For the measurement, a peeling test apparatus (manufactured by “A & D Co., Ltd., product name“ TENSILON RTA-1150-H ”) is used, and peeling condition is 50 mm / min at 23 ° C. at 23 ° C. Measurement was performed, and an average value of three measurements was adopted.
[Evaluation criteria]
A: 50 N / 15 mm or more B: 26 N / 15 mm or more, less than 50 N / 15 mm C: 16 N / 15 mm or more, less than 26 N / 15 mm D: Less than 16 N / 15 mm [Dump Heat (DH) Test]
In accordance with JIS C8917, each sample was subjected to a durability test for 1000 hours under the conditions of a test chamber temperature of 85 ° C. and a humidity of 85%. The adhesion test was performed on each sample after the test to evaluate the adhesion durability.

[Evaluation test for blocking resistance]
Each coating liquid having the composition described in the table is applied to the surface of each back surface protective sheet substrate described in the table with a bar coater, and the coated coating liquid is dried at 110 ° C. for 2 minutes to form a substrate. An easy-adhesion layer was formed on the surface. And what laminated | superposed the following films 1 and 2 generally used widely as the outermost layer of a back surface protection sheet on the surface of the easily bonding layer immediately after drying was used as the sample for blocking resistance evaluation.
Film 1: white fluorine film having a thickness of 25 μm: (product name Aflex 25PW, manufactured by Asahi Glass Co., Ltd.): The uneven surface was superimposed on the easy-adhesion layer.
Film 2: White polyester film having a thickness of 50 μm: (Product name VW, manufactured by Teijin DuPont Films Ltd.)
The above-mentioned sample for evaluating blocking resistance was allowed to stand for 72 hours using a blocking tester (load 3 kg / cm ² , 40 ° C.). Then, the anti-blocking test was evaluated by the method of evaluating the blocking state by peeling off the overlapped portion of the evaluation sample removed from the tester. In addition, when the difference was recognized in the evaluation result by the case where the laminated | stacked film is the film 1 and the case where it is the film 2, the lower evaluation result inferior to blocking property was made into the evaluation result of each sample.
[Evaluation criteria]
A: Sheets peel off naturally without transfer of the easy-adhesion layer B: No transfer of easy-adhesion layer, but there is adhesion between sheets, but there is no response C: At the time of peeling between substrates without transfer of the easy-adhesion layer There is a slight adhesion response D: There is a transition of the easy-adhesion layer and / or there is an adhesion response when the substrates are separated from each other

  From Tables 1 and 2, easy-adhesive back surface protection comprising a crosslinkable main resin made of a crosslinkable substituent-containing acrylic resin or the like, a crosslinkable resin crosslinked with a polyisocyanate compound, and an organometallic coordination compound. The sheet has excellent adhesion to EVA sealing material and LLDPE sealing material and good blocking resistance, and particularly contains an organometallic coordination compound, so that the blocking resistance is remarkably improved. It is understood that

<Test Example 2>
(Evaluation on NCO / OH ratio optimization and adhesion improvement)
About the sample of an Example, a comparative example, and a reference example, the improvement effect of the adhesiveness which concerns on optimization of NCO / OH ratio, durable adhesiveness, and blocking resistance was evaluated. Evaluation was performed based on the same evaluation criteria based on numerical values measured by the same method as in Test Example 1 above.

  From Tables 3-6, the main resin which consists of a crosslinkable substituent containing acrylic resin contains the crosslinking resin bridge | crosslinked with the polyisocyanate compound, the silane coupling agent, and the organometallic coordination compound, The easy adhesion It is understood that the conductive back surface protective sheet has good adhesion to the EVA sealing material and the LLDPE sealing material, and also has good blocking resistance. As for the silane coupling agent, in addition to the isocyanate-based silane coupling agent, epoxy-based silane coupling agent, and mercapto-based silane coupling agent that have been widely used as adhesion improvers, methyl / phenyl-based silane coupling agents have been used. It is understood that a ring agent can also be preferably used, and that a methyl / phenyl silane coupling agent can be particularly preferably used for an EVA sealing material.

  From Tables 1 to 4, regarding the amount of polyisocyanate compound used, when no pigment is added in an uncolored system, the NCO / OH ratio (ratio of NCO value of curing agent / OH value of main resin) is 0.3. Preferably, the amount is 5.0 or less, more preferably 0.5 or more and 2.5 or less, and if the NCO / OH ratio is in the above range, good adhesiveness, heat resistance and durability. It turns out that the easily-adhesive back surface protection sheet which has the property and blocking resistance can be obtained.

  From Tables 1-2 and 5-6, the amount of polyisocyanate compound used is preferably such that when a color pigment is added, the NCO / OH ratio is from 0.5 to 10.0. It can be seen that when the / OH ratio is in the above range, an easy-adhesive back surface protective sheet having good adhesion, heat resistance, durability, and blocking resistance can be obtained.

<Test Example 3>
(Other combinations of crosslinkable resin and back protection sheet substrate)
With respect to the samples of Examples 22 to 23 and Reference Example 3 in which the easy adhesion layer was formed on the polypropylene resin substrate of the back surface protection sheet, the effect of improving adhesiveness, durable adhesiveness and blocking resistance was evaluated. Evaluation was performed based on the same evaluation criteria based on numerical values measured by the same method as in Test Example 1 above.

  Moreover, about the sample of Examples 25-27 and Reference Examples 4-5 in which the easily bonding layer is formed on the hydrolysis-resistant PET (HR-PET) resin base material of the back surface protective sheet, The effect of improving blocking resistance was evaluated. Evaluation was performed based on the same evaluation criteria based on numerical values measured by the same method as in Test Example 1 above. In Reference Examples 4 and 5 in Tables 9 and 10, the primer compositions were the same as those in Examples 9 and 10 in Tables 3 and 4, respectively, and only the base resin was HR-PET. Are different.

  From Tables 7 to 8, the cross-linking resin is a urethane cross-linking resin, and an easy-adhesion layer containing an organometallic coordination compound is formed on the polypropylene resin substrate of the back protective sheet. It is understood that the adhesive back surface protective sheet has good adhesion to the EVA sealing material and the LLDPE sealing material, and also has good blocking resistance.

  From Tables 9 to 10, when the easy-adhesion layer is an easily-adhesive back-side protective sheet formed on a hydrolysis-resistant PET (HR-PET) resin substrate of the back-side protective sheet, hydrophobic silica is added as a filler. By doing, it is understood that it has favorable adhesiveness with respect to EVA sealing material and LLDPE sealing material, and can provide favorable blocking resistance. In addition, it is understood that the amount of the polyisocyanate compound used in that case is preferably such that the NCO / OH ratio is 1.2 or more and 2.5 or less.

  As for the glass transition point (Tg) of the main resin, it is understood that even a resin having a low Tg of 50 ° C. or lower, which has been conventionally regarded as a general lower limit temperature, can be preferably used.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front side sealing material layer 4 Solar cell element 5 Back side sealing material layer 6 Back surface protection sheet

Claims (15)

An easy-adhesion layer is formed on one side of the back surface protection sheet for solar cell modules composed of one or more layers,
The easy-adhesion layer contains: a) a crosslinkable main component resin, b) a crosslinked resin crosslinked with a polyisocyanate compound, and c) an organometallic coordination compound,
The easily adhesive back surface protection sheet whose NCO / OH ratio which is ratio of the NCO value of said b) polyisocyanate compound and OH number of said a) crosslinkable main ingredient resin is 0.3 or more and 10.0 or less. With respect to the total amount of said a) crosslinkable main ingredient resin and said b) polyisocyanate compound,
The easy-adhesive back surface protective sheet according to claim 1, comprising 0.1 to 7% by mass of the organometallic coordination compound. The easy-adhesion layer does not contain a coloring pigment,
The easy adhesion property according to claim 1 or 2, wherein an NCO / OH ratio, which is a ratio between the bco NCO value of the polyisocyanate compound and the a) OH value of the crosslinkable main resin, is 0.3 or more and 5.0 or less. Back protection sheet. The easy-adhesion layer contains a color pigment,
The easy adhesion property according to claim 1 or 2, wherein an NCO / OH ratio, which is a ratio of the bCO NCO value of the polyisocyanate compound and the OH value of the a) crosslinkable main resin, is from 0.5 to 10.0. Back protection sheet.   The easy-adhesive back surface protective sheet according to any one of claims 1 to 3, wherein the easy-adhesion layer contains no color pigment and contains an inorganic filler other than the color pigment.   The easily adhesive back surface protection sheet of Claim 5 which contains the said inorganic filler 1.0 or more and 35.0 mass% or less.   The easily adhesive back surface protective sheet according to claim 5 or 6, wherein the inorganic filler is hydrophobic silica.   The easy-adhesive back surface protective sheet according to any one of claims 1 to 7, wherein the easy-adhesion layer further contains d) a silane coupling agent. With respect to the total amount of said a) crosslinkable main ingredient resin and said b) polyisocyanate compound,
The easily adhesive back surface protective sheet according to claim 8, wherein the d) silane coupling agent is contained in an amount of 0.1 to 10% by mass.   The easily adhesive back surface protective sheet according to claim 8 or 9, wherein the cross-linked resin is a urethane resin, and the easy adhesive layer is formed on a polypropylene resin substrate of the back surface protective sheet.   The easily adhesive back surface protection sheet according to claim 8 or 9, wherein the a) crosslinkable main component resin is a crosslinkable substituent-containing acrylic resin, and the glass transition point thereof is 25 ° C or higher and 70 ° C or lower. And d) the easy-adhesion layer containing a silane coupling agent is formed on a hydrolysis-resistant polyethylene terephthalate resin substrate,
The NCO / OH ratio, which is the ratio of the b) NCO value of the polyisocyanate compound and the a) OH value of the crosslinkable main resin, is 1.2. The easily adhesive back surface protective sheet according to claim 8 , which is 2.5 or more and 9 or less. In the solar cell module in which the easy-adhesive back surface protective sheet according to any one of claims 1 to 12, the sealing material, and the solar cell element are integrated at least.
The solar cell module in which the easy-adhesive back surface protective sheet and the sealing material containing an ethylene-vinyl acetate copolymer resin are integrated via the easy-adhesive layer. In the solar cell module in which the easy-adhesive back surface protective sheet according to any one of claims 8 to 12, the sealing material, and the solar cell element are integrated at least.
The solar cell module in which the easy-adhesive back surface protective sheet and the sealing material containing polyethylene resin are integrated via the easy-adhesive layer. The sealing material includes a low-density polyethylene having a density of at least 0.900 g / cm ³ and / or a silane copolymer obtained by copolymerizing a linear low-density polyethylene and an ethylenically unsaturated silane compound as a comonomer. The solar cell module according to claim 14, which is a sealing material containing a polyethylene-based resin.

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