JP5899754B2 - Easy-adhesive layer composition and easy-adhesive back surface protective sheet using the same - Google Patents

Description

  The present invention provides an easily adhesive layer composition capable of stably forming an easily adhesive layer having excellent adhesiveness and blocking resistance with a solar cell module sealing material in a back surface protective sheet for a solar cell module. The present invention also relates to an easy-adhesive back surface protective sheet for solar cell modules in which an easy-adhesion layer is formed.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Generally, 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, 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 battery cell.

  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. However, EVA resin has a tendency to gradually decompose with long-term use, and deteriorates inside the solar cell module to decrease its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. For this reason, 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. During integration by such a method, an easy-adhesion layer made of a mixture of an acrylic resin, a silane coupling agent, and a polyisocyanate curing agent is formed in order to enhance the adhesion between the back surface protection sheet and the sealing material. The back surface protection sheet (refer patent document 1) which improved adhesiveness by doing is disclosed.

JP 2006-320991 A

  However, the back surface protection sheet disclosed in Patent Document 1 is based on the premise that EVA is used as a sealing material, and has a sufficient adhesiveness to a sealing material made of polyethylene resin such as LLDPE. Was not yet present.

  Moreover, an easily bonding layer is exposed to the outermost surface as a product before lamination | stacking. For this reason, blocking resistance which is not required in a normal adhesive layer is required. However, the present situation is that there is no backside protective sheet having both high adhesion and blocking resistance.

  In addition, the silane coupling agent as an industrial product is distributed in a sealed canned state, opened at the start of use, and then continuously used for several months. . Isocyanate-based silane coupling agent widely used as an additive for the purpose of improving the adhesiveness of the easy-adhesion layer is a few months from the start of use after the can is opened to the end of use. It is known that the degree of manifestation of the above effects varies. Although this is considered to be due to the change of the coupling agent with time, it has been a factor that hinders the stability of quality maintenance at the manufacturing site of the back surface protection sheet for solar cell modules.

  This invention is made | formed in view of the above situations, and has high adhesiveness between sealing materials, Especially between back surface side sealing materials for solar cell modules which consist of a polyethylene-type resin. With an extremely high adhesiveness, it can withstand long-term use in harsh environments and has excellent anti-blocking properties for solar cell modules. The purpose is to provide a stable and reliable service.

  As a result of intensive studies to solve the above problems, the present inventors have determined that an easy-adhesion layer composition, which is a material for forming an easy-adhesion layer on the back protective sheet, is obtained by using a polyisocyanate compound as the crosslinkable main resin. Containing a crosslinked resin, a silane coupling agent, and an organometallic coordination compound, and for the silane coupling agent contained in the easy-adhesion layer composition, a mercapto-based silane coupling It has high adhesion and blocking resistance to sealing materials including polyethylene-based sealing materials by limiting to agents, epoxy-based silane coupling agents, or a mixture of these two silane coupling agents. It has been found that an easily adhesive back surface protective sheet can be stably provided with high quality, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) An easy-adhesion layer composition for forming an easy-adhesion layer on the surface of a back surface protective sheet for a solar cell module, wherein a) a crosslinkable main component resin is crosslinked with b) a polyisocyanate compound. And c) a silane coupling agent; and d) an organometallic coordination compound, wherein the c) silane coupling agent is c1) a mercapto group-containing silane coupling agent and / or c2) an epoxy group. The easy-adhesion layer composition which is a containing silane coupling agent.

  (2) The easy adhesion layer composition according to (1), wherein the c) silane coupling agent is a mixture of c1) a mercapto group-containing silane coupling agent and c2) an epoxy group-containing silane coupling agent.

  (3) The easy-adhesion layer according to (1) or (2), wherein the a) crosslinkable main component resin is a crosslinkable substituent-containing acrylic resin, and its glass transition point (Tg) is 25 ° C. or higher and 70 ° C. or lower. Composition.

  (4) The above-mentioned c) 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, and d) The easily bonding layer composition in any one of (1) to (3) containing 0.1 to 7 mass% of organometallic coordination compounds.

  (5) A back surface protective sheet for a solar cell module in which an easy adhesion layer is formed on one surface, wherein the easy adhesion layer is the easy adhesion layer composition according to any one of (1) to (4) An easily-adhesive back surface protective sheet in which a coating solution containing a film is formed on one surface of the back surface protective sheet for solar cell module.

  (6) A coating liquid application step of applying a coating liquid containing the easy-adhesion layer composition according to any one of (1) to (4) to one surface of a resin substrate, and the applied coating liquid And a film forming step of forming an easy-adhesion layer by forming a film.

  (7) In the solar cell module in which the easy-adhesive back surface protective sheet according to (5), the sealing material, and the solar cell element are integrated at least, the easy-adhesive layer is interposed through the easy-adhesive layer. The solar cell module with which the back surface protection sheet and the said sealing material containing polyethylene-type resin are integrated.

(8) The sealing material is copolymerized using at least a low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less and / or a linear low density polyethylene (LLDPE) and an ethylenically unsaturated silane compound as a comonomer. (7) The solar cell module according to (7), which is a sealing material containing a polyethylene resin containing a silane copolymer.

  According to the present invention, by forming an easy-adhesion layer using an easy-adhesion layer composition having a specific composition, it has high adhesion and blocking resistance to a sealing material including a polyethylene-based sealing material. An easily adhesive back surface protection sheet can be provided stably and with high quality.

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. The present embodiment includes an easy-adhesion layer composition for forming an easy-adhesion layer on a back-surface protection sheet for solar cells, an easy-adhesion back-surface protection sheet formed with the easy-adhesion layer, a method for producing the same, and easy adhesion It is a solar cell module using a conductive back protective sheet.

<Easily adhesive layer composition>
First, the easy-adhesion layer composition according to the present invention will be described. The easy-adhesion layer composition of this embodiment is used for forming an easy-adhesion layer on the surface of the back surface protective sheet substrate layer, and is preferably bonded to the easy-adhesion layer as a back surface protection sheet for solar cell modules. Property and blocking resistance can be imparted.

[Composition of easy adhesion layer composition]
The easy-adhesion layer composition includes a) a crosslinkable main resin (hereinafter also simply referred to as main resin), b) a polyisocyanate compound, c) a silane coupling agent, and d) an organometallic coordination compound. Further, c) the silane coupling agent is either c1) a mercapto group-containing silane coupling agent, or c2) an epoxy group-containing silane coupling agent, or a composition of these two silane coupling agents. It is a thing.

[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. Further, 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 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, easily cured. Distinguish from resin with adhesive layer. Hereinafter, each constituent material will be described.

[Crosslinkable substituent-containing acrylic resin]
A crosslinkable substituent-containing acrylic resin (hereinafter also simply referred to as an 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 weather 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, 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, Various compounds having an ethylenically unsaturated bond such as vinylidene chloride, 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 the application of an easy-adhesion layer 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., the adhesiveness is increased. However, this is not preferable because the blocking resistance is lowered. However, in the easy-adhesion layer composition of the present invention in which a silane coupling agent and an organometallic coordination compound are used in combination, 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 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 has a plurality of hydroxyl groups for reacting with the polyisocyanate compound, and is cured by reacting with the polyisocyanate compound to form a firm 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 ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, ethanolamine, propanolamine and other aliphatic polyamines, 1,3- or 1,4-bis (aminomethyl) cyclohexane, Alicyclic polyamines such as 4,4′-, 2,4′- or 2,2′-dicyclohexylmethanediamine, isophoronediamine, norbornanediamine, m- or p-xylylenediamine, 1,3- or 1,4 -Aromatic polyamines such as tetramethylxylylenediamine, aromatic polyamines such as 2,4- or 2,6-tolylenediamine, 4,4'-, 2,4'- or 2,2'-diaminodiphenylmethane Can be illustrated. 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 back surface protective sheet base material layer, 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 layer, 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) Silane coupling agent]
Next, the silane coupling agent will be described. In the easy-adhesion layer composition of the present invention, a silane coupling agent added to the easy-adhesion layer composition in order to give preferable adhesion and blocking resistance to the easy-adhesion layer is c1) a mercapto group-containing silane coupling agent. (Hereinafter also referred to as a mercapto-based silane coupling agent) or c2) It is characterized in that it is limited to an epoxy group-containing silane coupling agent (hereinafter also referred to as an epoxy-based silane coupling agent). By limiting the types of silane coupling agents to these two types, agents that have been problematic when using isocyanate-based silane coupling agents that have been widely used as additives for forming an easy-adhesion layer in the past It is possible to eliminate variations in the improvement effect such as adhesiveness due to the change with time.

  Although it is conventionally known that a silane coupling agent can improve the adhesion between substrates generally made of a resin or the like, by limiting the type of silane coupling agent as described above, It has not been known in the past that variations in the improvement effect such as adhesiveness due to the change can be suppressed, and the point of limiting the type of the silane coupling agent to a specific type capable of exhibiting such an effect is the present invention. It is a feature.

[C1) Mercapto group-containing silane coupling agent]
The mercapto-based silane coupling agent is represented by the general formula [R1-Si (OR2) ³ ] (R1 represents a mercaptoalkyl group and R2 represents an alkyl group, respectively). Examples include mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 6-mercaptohexatrimethoxysilane. The mercapto-based silane coupling agent is not particularly limited, and a known silane coupling agent can be suitably used. For example, “KBM802” and “KBM803” (both manufactured by Shin-Etsu Silicone Co., Ltd.) are available and can be easily obtained from the market.

[C2) Epoxy group-containing silane coupling agent]
The epoxy-based silane coupling agent, the general formula ^{[R3-Si-R4 (3} -m) R5 m] (m represents an integer of 1 to 3, R3 represents an epoxy group, R4 represents an alkyl group, R5 represents an alkoxy group), and examples include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl. And methyldiethoxysilane. These may be used alone or in combination of two or more. In addition, an epoxy-type silane coupling agent is not specifically limited, A well-known silane coupling agent can be used suitably. For example, there are “KBM303”, “KBM402”, “KBM403”, “KBE402”, and “KBE403” (all manufactured by “Shin-Etsu Silicone Co., Ltd.”), which are easily available from the market.

  About the silane coupling agent to be added to the easy-adhesion layer composition of the present invention, even if any of the mercapto-based silane coupling agent and the epoxy-based silane coupling agent is added, And blocking resistance can be improved simultaneously. In order to achieve these objects, any silane coupling agent can be suitably used. However, when a mercapto silane coupling agent is used, the improvement in blocking resistance is particularly remarkable, and an epoxy silane When a coupling agent is used, the improvement of the adhesiveness with respect to EVA and a polyethylene-type sealing material is especially remarkable.

  In the easy-adhesion layer composition of the present invention, the silane coupling agent to be added is more preferably a mixture of two silane coupling agents, a mercapto-based silane coupling agent and an epoxy-based silane coupling agent. It can be set as an easily bonding layer composition. By limiting the kind of the silane coupling agent added to the easy-adhesion layer composition to such a mixture, an extremely easy-adhesion layer can be formed with respect to both adhesiveness and blocking resistance.

[D) 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 particular, when used in combination with the silane coupling agent, the adhesive strength is remarkably improved. In addition, the anti-blocking property of the easy-adhesion layer can be improved.

  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 triacetylacetonate can be preferably used from the point of antiblocking property 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. Moreover, an easily-adhesive back surface protection sheet is also a product which distribute | circulates independently, before integrating 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 that the combined use of an organometallic coordination compound and a silane coupling agent is effective for improving blocking resistance, which is an essential requirement unique to an easy-adhesion layer as a primer, This is also a feature of the present invention.

[Other additives]
Other additives for imparting weather resistance, light resistance, heat resistance, moisture resistance, flame resistance, etc. to the easy adhesion layer are added to the easy adhesion layer composition as necessary. In addition, the easy-adhesion layer composition is usually added to a sulfur agent as a coating liquid and used to form a product adhesive layer, but other additives are used for the stability of the coating liquid containing the easy-adhesion layer composition, the coating liquid. In order to improve workability, drying property, blocking resistance, etc., it is added as necessary.

  Examples of other additives include a dispersant, an antifoaming agent, a light stabilizer, an ultraviolet absorber, a heat stabilizer, and an antioxidant. These can use a well-known thing without a restriction | limiting in particular, According to the performance calculated | required by a coating liquid and an easily bonding layer, it selects suitably.

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

<Easily adhesive back protection sheet>
The easily adhesive back surface protection sheet will be described. The easy-adhesive back surface protective sheet of the present embodiment includes a back surface protective sheet base material layer and a back surface protection for a solar cell module formed including an easy adhesive layer formed on the surface of the back surface protective sheet base material layer. It is a sheet.

[Back protection sheet base material layer]
The back surface protective sheet base material layer constituting the easy adhesive back surface protective sheet becomes an easily adhesive back surface protective sheet by forming an easy adhesive layer on the surface thereof with the easy adhesive layer composition described above.

  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 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 weatherproof layer which consists of a fluorine film etc. in the outermost layer of an easily-adhesive back surface protection sheet. As a specific example, a white fluorine film, a white polyester film, or the like is weather-resistant by dry-laminating the surface of the back surface protective sheet base material layer on the side opposite to the surface provided with the easy-adhesion layer using a urethane-based adhesive. A layer can be provided.

  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.

[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 easy adhesion back surface protective sheet. This easy-adhesion layer is formed by applying a coating liquid containing the easy-adhesion layer composition described above to the surface of the back surface protective sheet base material layer, and forming a film from the applied coating liquid.

  A coating liquid contains the easily bonding layer composition of this invention, and contains a solvent and other various additives as needed. 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.

<Manufacturing method of easily adhesive back surface protection sheet>
[Formation of coating solution and easy adhesion layer]
The easy-adhesion layer is formed by drying the solvent from the coating liquid applied on the above-mentioned back surface protective sheet base material layer and crosslinking the main resin contained in the coating liquid with the polyisocyanate compound. The coating liquid contains an organic solvent for dissolving or dispersing the main resin.

  The content of the main resin in the coating liquid is preferably 10 to 60% by mass. When the content of the resin in the coating liquid is 10% by mass or more, the pigment contained in the coating liquid can be favorably dispersed. Moreover, the applicability | paintability of a coating liquid becomes favorable because content of resin in a coating liquid is 60 mass% or less.

  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 pigment is added, the amount used may be increased 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 pigment surface or adsorbed moisture. Moreover, the quantity from which NCO / OH ratio (ratio of NCO number of hardening | curing agent / OH number of main ingredient resin) will be 0.1-10 is preferable. When the pigment is passed through for coloring, the amount of the isocyanate compound used is preferably 1 to 75 parts by mass with respect to 100 parts by mass of the main resin, and the NCO / OH ratio in that case (the NCO of the curing agent) The ratio of the valence / OH ratio of the main resin to 0.1 to 10 is preferable. When almost no pigment is added in an uncolored system, the amount of the isocyanate compound used is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the main resin. In such a case, an amount in which the NCO / OH ratio (ratio of NCO value of the curing agent / OH value of the main resin) is 0.1 to 5 is preferable. When the NCO / OH ratio exceeds the above amount, side reaction products due to the reaction between the remaining isocyanate groups and the moisture in the air increase, and the adhesiveness, heat resistance and durability decrease, but the NCO / OH ratio is If it is in the range, it is preferable because good adhesion, heat resistance and durability can be obtained. In addition, when using the solution containing a polyisocyanate compound as a hardening | curing agent and making it a 2 liquid type coating liquid, a well-known organic solvent is suitably selected and used for a hardening | curing agent. Such a solvent will be described later.

  The content of the silane coupling agent is preferably from 0.1% by weight to 10% by weight, more preferably from 0.5% by weight to 8% by weight, based on the total amount of the main resin and the polyisocyanate compound. Preferably they are 1.0 mass% or more and 8 mass% or less. In particular, when a pigment is added, the amount used may be increased by taking into account the alkoxy groups consumed by the reaction with other than the main resin due to the reaction with the pigment surface. 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. Moreover, even if content of a silane coupling agent exceeds 10 mass%, since there is no further improvement of adhesiveness and a coating film becomes brittle, it is not preferable.

  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. 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, a high boiling point solvent such as tripropylene glycol dimethyl ether may be added to adjust the drying rate during coating.

  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.

  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 for applying the coating liquid to the surface of the back surface protective sheet base material layer, 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 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 ° C to 120 ° C for 30 seconds to 2 minutes. By heating in this way, preferable blocking resistance and adhesiveness are exhibited. 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 back surface protective sheet base material layer 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.

  In the production of the back surface protection sheet having an easy adhesion layer by a conventional general method, it was not possible to prevent the quality variation due to the aging of the silane coupling agent, but the easy adhesion layer composition of the present invention was not used. According to the manufacturing method used, it is possible to stably manufacture a high-quality easily-adhesive back surface protective sheet while suppressing such quality variations.

<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 protective sheet as the back surface protective sheet 6.

  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 a normal thermoplastic resin, 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. And especially the adhesiveness between the back surface side sealing materials which consist of a polyethylene-type resin improves notably. For this reason, not only EVA but polyethylene resin can be suitably used as the back surface side sealing material. That is, the easy-adhesive back surface protective sheet of the present invention is particularly preferable for a back surface sealing material made of polyethylene resin, and is characterized in that it has both adhesion to a back surface sealing material made of polyethylene resin and weather resistance. is there. 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.

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. 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.

  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 mass% or more and less than 0.5 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.

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

The coating liquid which forms an easily bonding layer in the easily adhesive back surface protection sheet of each Example and a comparative example was prepared using the following easily bonding layer composition and a solvent.
Crosslinkable main resin (acrylic polyol resin): Tg 40 ° C., acid value 6, hydroxyl value 19, weight average molecular weight 17000.
Polyisocyanate compound (HDI curing agent): (Product name FG700, manufactured by DNP Fine Chemical Co., Ltd.): Formulated so that the mass ratio to 100 parts by mass of the main resin is 29.5 mass% and the NCO / OH ratio is 4.4. did.
Organometallic coordination compound (aluminum trisacetylacetonate): (Product name: Aluminum chelate A (W), manufactured by Kawaken Fine Chemical Co., Ltd.): The mass ratio to the total amount of the crosslinkable main resin and the polyisocyanate compound is 3.1 mass. It mix | blended so that it might become%.
Silane coupling agent 1 (indicated as “mercapto” in Table 1): 3-mercaptopropyltrimethoxysilane (product name KBM803, manufactured by Shin-Etsu Silicone Co., Ltd.).
Silane coupling agent 2 (indicated as “epoxy” in Table 1): 3-glycidoxypropyltriethoxysilane (product name KBE-403, manufactured by Shin-Etsu Silicone Co., Ltd.).
Silane coupling agent 3 (indicated as “Isocyan” in Table 1): 3-isocyanatopropyltriethoxysilane (product name KBE-9007, manufactured by Shin-Etsu Silicone Co., Ltd.).
: About the silane coupling agents 1-3, it was set as the mixing | blending as shown in Table 1, and the total addition amount is 4.6 mass% in the mass ratio with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound. It mix | blended so that it might become.
Solvent: Toluene: Methyl ethyl ketone = 1: 1 mixture

About said silane coupling agent 1-3, in order to verify the presence or absence of the dispersion | variation in the adhesive improvement effect by a time-dependent change, about each silane coupling agent, the state in which the elapsed time after opening differs as follows (table | surface) 1 were written as A to C). The silane coupling agent was opened from the state sealed in the Ito can and started to be used. Thereafter, the silane coupling agent which had been closed again and stored for a certain period was opened again and used. Note that the closed canister was not completely sealed, and the storage conditions were a temperature of 25 ° C. to 30 ° C. and a humidity of 50% Rh to 70% Rh.
A: Used for the first time after opening B: After opening, stored for 1 month C: After opening, stored for 3 months

  The easy-adhesion layer composition was prepared for each of the Examples and Comparative Examples in the formulation shown in Table 1, and the coating solution was added to each Example and Comparative Example by adding the solvent. The partial concentration was adjusted to 35% by mass.

A sheet made of biaxially stretched polyethylene terephthalate (PET) having a thickness of 188 μm was used as a back protective sheet base material layer. Each coating liquid prepared as described above was applied to the surface of the back surface protective sheet base material layer with a bar coater, and the coated coating liquid was dried at 120 ° C. for 2 minutes, and then at 50 ° C. for 3 days. Curing was performed to form an easy-adhesion layer, and samples of Examples 1 to 3 and Comparative Example were used. The coating amount of each coating solution was 1 g / m ² .

About each sample of produced Examples 1-3 and a comparative example, the following sealing material sheet was used for 15 minutes at 150 degreeC on the surface which coated the said coating liquid, and the vacuum laminator for manufacture of a solar cell module was used. And laminated to prepare a sample for evaluation of adhesiveness and durable adhesiveness.
Sealing material sheet: a resin blended so that the mass ratio of the following silane-modified transparent resin, weatherproof masterbatch, and polymerization initiator compound resin is 20: 5: 80 so that the extrusion temperature is 210 ° C. and the thickness becomes 200 μm. An LLDPE resin having a weak crosslinkability formed into a film.
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 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) are mixed, melted and kneaded at 200 ° C., density 0.884 g / cm ³ , MFR at 190 ° C. A silane-modified transparent resin having a weight 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.

<Evaluation of adhesiveness>
About the samples for Examples 1 to 3 and comparative examples using the samples of Comparative Examples, the initial adhesiveness and the durable adhesiveness (hydrolysis resistance) were evaluated. Evaluation was performed based on the numerical value measured by the following method.
(Initial adhesion test: Peel test)
About each sample for evaluation, peeling strength (N) measured the initial value about adhesiveness, and the value after each endurance test by 180-degree peel of 15 mm width. For the measurement, using a peeling test apparatus (manufactured by “A & D Co., Ltd., trade name“ TENSILON RTG-1210 ”), measurement is performed at 25 ° C. under a peeling condition of 50 mm / min at 180 ° peel. The average value of four measurements was adopted. The results are shown in Table 1.
[Evaluation criteria]
○: 40 N / 15 mm or more Δ: 16 N / 15 mm or more, less than 40 N / 15 mm ×: less than 16 N / 15 mm (adhesion durability test: 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%. Each sample after the test was subjected to a peel test similar to the initial adhesion test. The results are shown in Table 1.
○: 40 N / 15 mm or more Δ: 16 N / 15 mm or more, less than 40 N / 15 mm ×: less than 16 N / 15 mm

<Evaluation of blocking resistance>
Each coating solution having the composition shown in Table 1 is applied to the surface of a 50 μm thick biaxially oriented polyethylene terephthalate (PET) film with a bar coater, and the applied coating solution is dried at 120 ° C. for 2 minutes. An easy-adhesion layer was formed on the substrate surface. And what was cured at 50 degreeC for 3 days in the state which piled up and contacted the same PET film on the surface of the easily bonding layer immediately after drying was made into the sample for blocking resistance evaluation.
The blocking resistance test was evaluated by the method of evaluating the blocking state by peeling off the overlapped portion of the blocking resistance evaluation sample.
[Evaluation criteria]
○: Sheets peel off spontaneously without transfer of the easy-adhesion layer. Δ: There is a slight adhesion when peeling between substrates without transfer of the easy-adhesion layer. X: Transfer of the easy-adhesion layer and / or Adhesive response when peeling between substrates

  In Examples 1 to 3, the initial adhesiveness does not vary with time, but the Comparative Example shows variation. As a result, the easy-adhesive layer composition of the present invention has a good adhesiveness to the sealing material and stably has a good anti-adhesive back surface protection while suppressing variations due to changes over time. It turns out that it is preferable when manufacturing a sheet | seat. It can also be seen that a more preferable easily-adhesive back surface protective sheet can be obtained by using a mercapto silane coupling agent and an epoxy silane coupling agent in combination as in Example 3.

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 (6)

An easy-adhesion layer composition for forming an easy-adhesion layer on the surface of the back surface protection sheet for solar cell modules,
a) a crosslinkable main agent resin, b) a crosslinked resin crosslinked with a polyisocyanate compound, and
c) a silane coupling agent;
d) an organometallic coordination compound,
The c) silane coupling agent is a mixture of c1) a mercapto group-containing silane coupling agent and c2) an epoxy group-containing silane coupling agent ,
The a) easy-adhesion layer composition in which the crosslinkable main resin is a crosslinkable substituent-containing acrylic resin, and the glass transition point (Tg) thereof is 25 ° C. or higher and lower than 50 ° C. The total content of the a) crosslinkable main resin and the b) polyisocyanate compound contains the c) silane coupling agent in an amount of 0.1% by mass to 10% by mass,
The easy-adhesion layer composition according to claim 1 , wherein the composition contains d) an organometallic coordination compound in an amount of 0.1% by mass to 7% by mass. It is a back surface protection sheet for solar cell module in which an easy adhesion layer is formed on one surface,
The easily adhesive layer is an easily adhesive back surface protective sheet in which a coating liquid containing the easily adhesive layer composition according to claim 1 or 2 is formed on one surface of the back surface protective sheet for solar cell modules. . A coating liquid application step of applying a coating liquid containing the easy-adhesion layer composition according to claim 1 or 2 to one surface of a resin substrate;
And a film forming step of forming an easy-adhesion layer by forming a film of the coating liquid. In the solar cell module in which the easy-adhesive back surface protective sheet according to claim 3 , 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 is formed by copolymerizing at least a low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less and / or a linear low density polyethylene (LLDPE) and an ethylenically unsaturated silane compound as a comonomer. The solar cell module according to claim 5 , wherein the solar cell module is a sealing material containing a polyethylene resin containing a silane copolymer.

Images