JP5868628B2 - Back protection sheet - Google Patents

Description

The present invention is a novel back surface protection sheet for a photovoltaic power generation module, and relates to a photovoltaic power generation module using this sheet member. More specifically, it is a novel back surface protection sheet that is excellent in various properties such as mechanical strength, heat resistance, weather resistance, moisture resistance, and antifouling properties and contributes to module reliability and manufacturability.

Solar power generation, so-called solar cells, have attracted attention due to the prevention of global warming, the demand for sustainable energy, and increased awareness of environmental issues, and so far, various types of solar power generation modules have been proposed. Yes. In general, the above solar power generation module, for example, taking a single crystal or polycrystalline silicon power generation element as an example, a protective tempered glass, a surface sealing material layer, a solar power generation element, a back surface sealing material layer, And it is manufactured using the lamination method etc. which are laminated | stacked in order of a back surface protection sheet layer etc., and heat-press-bonded in a vacuum.

The back surface protective sheet is provided with an outermost protective layer, that is, a fluorine resin layer excellent in weather resistance and stain resistance, an aluminum layer or a barrier resin layer which is a gas barrier layer inside if necessary, and further a mechanical strength inside, A complex multilayer structure consisting of a support layer (mainly made of stretched PET resin) for imparting heat resistance, and a low-density polyethylene layer, which is an adhesive layer for guaranteeing adhesion to the EVA sealing material inside Have taken. These backside protective sheets having a multilayer structure are mainly manufactured by a plurality of dry lamination processes using urethane-based adhesives, and the reduction of manufacturing costs and raw material costs is one of the issues for the popularization of photovoltaic power generation devices. It has become one. In other words, there is a new simpler sheet configuration that excels in various properties such as mechanical strength, heat resistance, weather resistance, moisture resistance, and antifouling properties, and can further reduce module reliability, ease of manufacture, and manufacturing costs. It has been demanded.
Various studies have been made to solve the above-described problems. For example, a polyolefin resin composition layer (Patent Document 1), a polystyrene resin composition layer (Patent Document 2), and a polyphenylene ether resin composition layer (Patent Document 1). Backside protective sheets including literature 3) have been studied.

JP2007-306006, JP2010-2226045 JP 2010-109348 JP 2010-245380

An object of the present invention is to provide a back surface protection sheet that is excellent in various properties such as mechanical strength, heat resistance, weather resistance, moisture resistance, and antifouling property, and can be easily manufactured and reduced in production cost as compared with a conventional back surface protection sheet.

The back surface protective sheet of the present invention is a back surface protective sheet composed of at least a protective layer made of a fluorine-based resin and a support layer made of a cross-copolymer resin.

The back surface protective sheet of the present invention is a back surface protective sheet composed of at least a protective layer made of a fluorine-based resin and a support layer made of a cross-copolymer resin. This back surface protection sheet is excellent in various properties such as mechanical strength, heat resistance, weather resistance, moisture resistance and antifouling properties, and has the possibility of further reducing the production cost due to its simple structure and easy production method.

The back surface protective sheet of the present invention is a back surface protective sheet composed of at least a protective layer made of a fluorine-based resin and a support layer made of a cross-copolymer resin. This back surface protection sheet is excellent in various properties such as mechanical strength, heat resistance, weather resistance, moisture resistance and antifouling properties, and has the possibility of further reducing the production cost due to its simple structure and easy production method. The sheet in the present invention includes the concept of a film, and the thickness thereof is not particularly limited, and generally ranges from 10 μm to 3 mm.

Hereinafter, the back surface protective sheet of the present invention will be specifically described. The back surface protection sheet is generally an outermost layer A: a protective layer, B: a gas barrier layer that barriers water vapor or the like that is optionally provided, C: a support layer that retains mechanical strength, D: an optional sealing material, and It is the multilayer sheet comprised from the contact bonding layer for ensuring adhesiveness of this. Here, as the protective layer A, a sheet made of a fluororesin having excellent weather resistance and stain resistance is used. As the fluororesin used in the protective layer, a copolymer mainly composed of polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF) is used. Such a copolymer refers to a resin in which a unit derived from a vinyl fluoride monomer (VF) or a vinylidene fluoride monomer (VDF) accounts for 70% by mass or more, preferably 80% by mass or more of the entire resin. As comonomer, VDF is mainly composed of VF, VF is composed mainly of VDF, and other common comonomer is trifluoroethylene, chlorotrifluoroethylene (CTFE), 1,2-difluoroethylene, tetrafluoroethylene (TFE). , Hexafluoropropene (HFP), 3,3,3-trifluoropropene and / or 2-trifluoromethyl-3,3,3-trifluoro-1-propene copolymer. In this specification, it describes as PVF type resin and PVDF type resin, respectively. Furthermore, PVDF resin is PVDF 10% by mass or more and 100% by mass or less, preferably 50% by mass or more and 100% by mass or less, methacrylic acid ester resin such as polymethyl methacrylate, 0% by mass or more and 90% by mass or less, preferably It is a resin composition which consists of 0 mass% or more and 50 mass% or less. The thickness of the protective layer is generally in the range of 5 μm to 50 μm.
The protective layer can contain a suitable pigment such as a white pigment such as titanium oxide up to 50% by mass. Furthermore, this protective layer can contain known anti-aging agents, antioxidants, light stabilizers, ultraviolet absorbers and the like that can be usually added to the back surface protective sheet.
Furthermore, it is also possible to use a coating film formed by applying a fluororesin-based paint as the protective layer of the back protective sheet used in the present invention. In this case as well, necessary amounts of known pigments, anti-aging agents, antioxidants, light stabilizers, ultraviolet absorbers and the like can be included.

Conventionally, B: gas barrier layer for preventing permeation of water vapor or the like may be provided as a second layer inside the protective layer. For this gas barrier layer, a barrier resin obtained by coating an aluminum foil or a PET resin with a thin film (deposited film) made of an inorganic oxide is used. However, when an excessive water vapor barrier property is not required, such as when using a crystalline silicon cell, the gas barrier layer may be omitted from the viewpoint of cost. Therefore, although the second layer serves as a support layer in a certain form of the present invention, the support layer generally has a thickness of 40 μm to 200 μm, and conventionally, polyester resins such as PET and PEN are generally used. In the case of a PET resin, it is effective to use a stretched sheet for imparting heat resistance, and multilayering by coextrusion is difficult. Further, when a polyester resin is used as the support layer, there is a drawback that the adhesiveness with the fluorine resin used for the protective layer or the EVA resin of the sealing material is poor. Therefore, dry lamination using a urethane-based adhesive is performed for bonding with a fluororesin. In some cases, an LDPE or LLDPE layer for bonding with a sealing material made of EVA resin is provided.

In the present invention, C: a resin mainly composed of a cross copolymer (hereinafter referred to as a cross copolymer resin) is used as a support layer. The support layer generally has a thickness of 40 μm to 400 μm, preferably 40 to 200 μm. When using this cross-copolymer-based resin as a support layer, first of all, its mechanical strength, elastic modulus, elongation, and breaking strength are excellent, and its value is optimized depending on the type of crystal silicon type device, thin film type device, etc. The point which can be adjusted is mentioned. In addition, the resin has a basic property that can contribute to the durability of the module because the resin has high electrical insulation properties, such as high dielectric breakdown voltage and volume resistivity, low water vapor permeability, and the like. Furthermore, by blending an appropriate heat-resistant thermoplastic resin with the present cross-copolymer, sufficient heat resistance can be imparted while maintaining the above properties.
Conventionally, a stretched PET resin is used for the support layer. The stretched PET resin is characterized by its high mechanical strength and heat resistance, and is widely used in this application. However, it is difficult to answer the cost reduction demands in this field, such as that it takes time for biaxial stretching and the like, and that the coextrusion method cannot be adopted in the production of multilayer films.

The cross copolymer used in the present invention is a copolymer obtained by anionic polymerization in the presence of an olefin-aromatic vinyl compound-aromatic polyene copolymer and aromatic vinyl compound monomer obtained by coordination polymerization. A olefin-aromatic vinyl compound-aromatic polyene copolymer chain (may be described as a main chain) and an aromatic vinyl compound polymer chain (may be described as a side chain). It is a copolymer. The present cross-copolymer and its production method are described in WO2000-37517, USP6559234, or WO2007-139116, and the content of units derived from an aromatic vinyl compound and an olefin monomer is 70% of the total copolymer mass. %, Preferably 90% by mass or more, and most preferably 99% by mass or more. In the cross-copolymer used in the present invention, the content of units derived from aromatic polyene is preferably less than 5% by mass of the copolymer mass, 0.01% by mass or more, and more preferably less than 1% by mass. It is at least mass%.

Examples of the aromatic vinyl compound include styrene and various substituted styrenes such as p-methylstyrene, m-methylstyrene, o-methylstyrene, ot-butylstyrene, mt-butylstyrene, and pt-butylstyrene. , P-chlorostyrene, o-chlorostyrene and the like. Industrially, styrene, p-methylstyrene, p-chlorostyrene, particularly preferably styrene is used.
Examples of the olefin include ethylene and an α-olefin having 3 to 20 carbon atoms, that is, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. In the present invention, cyclic olefins are also included in the category of olefins, and examples of the cyclic olefins include vinylcyclohexane, cyclopentene, and norbornene. Preferably, ethylene or a mixture of ethylene and an α-olefin, that is, propylene, 1-butene, 1-hexene, or 1-octene is used, and more preferably, ethylene is used.
Here, the aromatic polyene is a monomer having a carbon number of 10 or more and 30 or less, having a plurality of double bonds (vinyl group) and one or a plurality of aromatic groups and capable of coordination polymerization. An aromatic polyene in which one of (vinyl group) is used for coordination polymerization and a double bond left in a polymerized state can be anionically polymerized. Preferably, any one or a mixture of two or more of orthodivinylbenzene, paradivinylbenzene and metadivinylbenzene is preferably used. Further, among the cross copolymers, a cross copolymer having an ethylene-styrene-divinylbenzene copolymer as the main chain and a polystyrene chain as the side chain is most preferably used.

For example, WO 2007-139116, JP-A 2009-120792, and JP-A 2010-150442 describe the composition, production method, total light transmittance, and A hardness of the cross-copolymer satisfying this condition. Therefore, those skilled in the art can easily manufacture by performing a few trials with reference to these. Specifically, when the aromatic vinyl compound is styrene and the olefin is ethylene, a cross-copolymer that satisfies this condition can be achieved by satisfying the following conditions. For example, the ethylene-styrene-divinylbenzene copolymer used for the production of the cross-copolymer has a styrene content of 5 mol% to 40 mol%, a divinylbenzene content of 0.01 mol% to 3 mol%, and finally The mass proportion of the present ethylene-styrene-divinylbenzene copolymer in the obtained cross-copolymer is 40% by mass or more and 90% by mass or less.
In solar cells, electrical insulation is important to ensure long-term reliability. This cross copolymer itself can exhibit a volume resistivity of 1 × 10 ¹⁶ Ω · cm or more and a dielectric breakdown voltage of 20 kV / 1 mm or more. Since this is higher than the conventional PET resin, it is suitable as a material for the support layer. Further, prevention of water vapor penetration is important for preventing electrical troubles such as corrosion and insulation failure. This cross-copolymer is suitable because it exhibits a low water vapor transmission rate, specifically a low water vapor transmission rate of 5 g / m ² · day (as a 1 mm thick film) or less. The water vapor transmission rate was determined under the conditions of 40 ° C. and 90% humidity according to the JISZ0208 cup method.

When used as a support layer, heat resistance is also important. During use, the solar cell is required to have a maximum environmental temperature of about + 50 ° C., that is, about 120 ° C. Further, during vacuum lamination during production, it is exposed to heating conditions of several tens of minutes at a maximum of 150 to 160 ° C. Under these conditions, the support layer needs to keep the sealing material and the protective layer mechanically without causing creep deformation or melt flow, and to maintain a uniform thickness to ensure insulation.

The cross-copolymer-based resin used for the support layer is a resin composition composed of a cross-copolymer and at least one thermoplastic resin and containing 40% by mass or more of the cross-copolymer. Examples of such a resin composition include a resin composition comprising a thermoplastic resin having a heat resistance of 150 ° C. or higher, such as polypropylene (PP), polyethersulfone (PES), or polyphenylene sulfide (PPS), and a cross copolymer. . Here, the heat resistance means that at least one of the crystal melting point or the glass transition temperature is 150 ° C. or higher. Particularly suitable is a resin composition comprising a polyphenylene ether resin and a cross copolymer described in WO2009 / 128444. The cross-copolymer is well compatible with the PPE resin, and the resin composition maintains the high electrical insulation properties (volume resistivity, dielectric breakdown voltage) of the cross-copolymer itself and maintains a low water vapor transmission rate. However, rigidity (initial elastic modulus in the tensile test) and heat resistance are improved, and it is suitable as a support layer for the back surface protection sheet. Moreover, the point which has the flame retardance derived from PPE-type resin is also preferable.

The polyphenylene ether resin (hereinafter referred to as PPE resin) used in the present invention is a resin substantially composed of a polyphenylene ether unit. If necessary, an aromatic vinyl compound polymer is added to the resin mass. Up to 80% by weight, preferably up to 50% by weight.
This polyphenylene ether resin can be obtained, for example, from SABIC Innovative Plastics under the product name Noryl, from Asahi Kasei Chemicals under the product name Zylon, and from Mitsubishi Engineering Plastics under the product name Iupiace. Examples of polyphenylene ether resins include poly (2,6-dimethyl-1,4-phenylene) ether, poly (2-methyl-6-n-butyl-1,4-phenylene) ether, poly (2-ethyl) -6-n-propyl-1,4-phenylene) ether, poly (2-methyl-6-ethyl-1,4-phenylene) ether, poly (2,6-diethyl-1,4-phenylene) ether, poly ( 2,6-di-n-propyl-1,4-phenylene) ether, poly (2-methyl-6-hydroxyethyl-1,4-phenylene) ether, poly (2-methyl-6-chloroethyl-1,4) -Phenylene) ether poly (2-ethyl-6-isopropyl-1,4-phenylene) ether, poly (2-methyl-6-chloroethyl-1,4-phenylene) ether unit, etc. Copolymers of polymers or their units composed of repeating structure alone like. The polyphenylene ether copolymer is a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol, a copolymer of o-cresol, or 2,3,6-trimethylphenol and o-cresol. A polyphenylene ether copolymer mainly composed of a polyphenylene ether structure. Further, various phenylene ether units, for example, phenylene ether units having an aminomethyl group or an N-phenylaminomethyl group may be copolymerized as a partial structure thereof up to 20% by weight.

The molecular weight of the polyphenylene ether-based resin used in the present invention is not particularly limited, but the weight average molecular weight in terms of standard polystyrene by gel permeation chromatography (GPC) measurement is 2,000 to 300,000. In view of the above, the preferable range is about 5,000 to 100,000.
Examples of the aromatic vinyl compound-based polymer contained in the polyphenylene ether-based resin include homopolymers of aromatic vinyl compounds such as styrene, α-methylstyrene, paramethylstyrene, and copolymers thereof. Examples of the monomer copolymerizable with the aromatic vinyl compound include butadiene, isoprene, other conjugated dienes, acrylic acid, methacrylic acid, amide derivatives and ester derivatives thereof, acrylonitrile, maleic anhydride and derivatives thereof. The polystyrene equivalent weight average molecular weight of the aromatic vinyl compound polymer is in the range of 30,000 to 500,000. Also, so-called high impact polystyrene (HIPS) in which these resins are reinforced with rubber such as polybutadiene may be used. The aromatic vinyl compound-based polymer can be contained up to 80% by mass with respect to the total mass of the polyphenylene ether-based resin used in the present invention.

The initial elastic modulus of the cross-copolymer-based resin used as the support layer of the back surface protection sheet is generally 20 MPa to 5 GPa, preferably 50 MPa to 2 GPa, particularly preferably 100 MPa to 1 GPa, and the elongation at break is preferably Is 10% or more and 300% or less, and the breaking strength is preferably 10 MPa or more and 100 MPa or less. Further, the storage elastic modulus of the resin at 120 ° C. is 1 × 10 ⁶ Pa or more, preferably 1 × 10 ⁷ Pa or more, and the storage elastic modulus of the resin at 160 ° C. is 1 × 10 ⁵ Pa or more, preferably 1 × 10 ⁶ Pa. It must be Pa or higher. This storage elastic modulus can be easily obtained using a known viscoelasticity measuring apparatus. In order to satisfy the heat resistance as described above, preferably the cross-copolymer is 40 to 80% by mass, more preferably 50 to 80% by mass, and the PPE resin is 60 to 20% by mass, and more preferably 50 to 20%. % By mass.

Furthermore, the volume resistivity of the cross-copolymer resin used for the support layer of the back surface protection sheet can be 1 × 10 ¹⁶ Ω · cm or more, and the dielectric breakdown voltage can be 40 kV / 1 mm or more. Further, prevention of water vapor penetration is important for preventing electrical troubles such as corrosion and insulation failure. Since the present cross-copolymer-based resin exhibits a low water vapor transmission rate, specifically a low water vapor transmission rate of 5 g / m ² · day (per 1 mm thick film) or less, it is suitable as a sealing material. The water vapor transmission rate was determined under the conditions of 40 ° C. and 90% humidity according to the JISZ0208 cup method.
The MFR value (200 ° C., weight 98N) of the cross-copolymer as the raw material resin is not particularly specified, but is generally 0.1 g / 10 min to 300 g / 10 min, substantially in a non-crosslinked state In consideration of the above heat resistance, the amount is 0.1 g / 10 min or more and 100 g / 10 min or less. The MFR, melt viscosity, and tension of the resin composition composed of the cross-copolymer and the PPE resin are advantageous in that they can be arbitrarily adjusted by the blending composition and the raw material resin. For example, from the resin of the protective layer and the resin of the support layer When the multilayer sheet to be manufactured is to be produced by an economically advantageous coextrusion method, those skilled in the art can adjust the MFR, melt viscosity, and tension of both to an appropriate range that is relatively close.

In the support layer of the back surface protection sheet of the present invention, a light stabilizer composed of an ultraviolet absorber that converts light energy into harmless heat energy and a hindered amine light stabilizer that captures radicals generated by photooxidation is blended. To do. Examples of the ultraviolet absorber include benzotriazole, triazine, benzophenone, benzoate, oxalic anilide, and malonic ester. The mass ratio of the ultraviolet absorber and the hindered amine light stabilizer is in the range of 1: 100 to 100: 1, and the total mass of the ultraviolet absorber and the hindered amine light stabilizer is the light-proofing agent mass. It is the range of 0.05-5 mass parts with respect to 100 mass parts of mass. The above light-proofing agents can be obtained, for example, as ADEKA STAB LA series from ADEKA Corporation or as Sumisorb series from Sumika Chemtex Co., Ltd.
Further, a white pigment can be added to the support layer of the back surface protection sheet of the present invention in order to efficiently reflect or scatter incident light and make it usable again. As such a white pigment, only one kind of metal oxides such as titanium oxide, zinc oxide, silicon oxide, and aluminum oxide; inorganic compounds such as calcium carbonate and barium sulfate may be used alone, or two kinds may be used. The above may be used in combination. In the present invention, among these, titanium oxide, zinc oxide, and calcium carbonate can be preferably used, and more preferably, titanium oxide exhibiting sufficient light reflectivity and scattering properties can be used with a small addition amount.

In recent years, hot spots have attracted attention as one of the factors that promote the deterioration of photovoltaic power generation devices. A hot spot is a phenomenon in which the resistance of a cell increases due to an increase in the resistance of the wiring or due to the deterioration of the cell, which consumes the power of other cells and partially generates heat. It is supposed to lead to final damage. For example, it is considered that by providing the back surface sealing material with heat dissipation, it is possible to diffuse and dissipate heat generated by the initial deterioration and prevent further deterioration. (DKK published patent citation) For this purpose, the back surface sealing material can be filled with a heat-conductive inorganic filler known in the art. Examples of such a thermally conductive filler include alumina, boron nitride, titanium oxide, and aluminum nitride. The filling amount is about 30 to 80% by mass with respect to the amount of the resin composition material, and the thermal conductivity is about 0.1 to 5 W / m · K.
In order to use the resin of the present invention or a sheet thereof as a sealing material for thermoplastic photovoltaic power generation devices, the following “anti-aging agent” can be added as necessary for the purpose of improving the properties as a sealing material. .
An anti-aging agent can be added to the cross-copolymer resin used for the support layer. Examples include hindered phenol antioxidants, phosphorus heat stabilizers, lactone heat stabilizers, vitamin E heat stabilizers, sulfur heat stabilizers, and the like. The usage-amount is 3 parts weight or less with respect to 100 mass parts of resin compositions.
For the support layer of the back surface protection sheet, other additives that are used in ordinary resins, such as antistatic agents, colorants, lubricants, foaming agents, are used as long as they do not impair the purpose of the present invention. In addition, flame retardants, flame retardant aids and the like may be added.

A well-known method can be used for adhesion | attachment and multilayering of the support layer and protective layer of a back surface protection sheet of this invention. Examples of such a method include a dry lamination method, an extrusion laminating method, and a co-extrusion method, and an appropriate adhesive layer made of a resin or an adhesive is used in order to impart adhesiveness.
Examples of the adhesive layer (adhesive) used in the dry laminating method and extrusion laminating method include polyvinyl acetate adhesives, polyacrylate adhesives, reactive (meth) acrylic adhesives, and cyanoacrylates. Adhesives, ethylene copolymer adhesives consisting of copolymers of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, methacrylic acid, etc., polyester adhesives, polyamide adhesives, polyimide adhesives Adhesion of amino resin adhesives made of urea resin or melamine resin, phenolic resin adhesives, epoxy adhesives, polyurethane adhesives, rubber adhesives made of chloroprene rubber, styrene-butadiene rubber, etc. Agents can be used. The composition system of the above-mentioned adhesive may be any composition form such as an aqueous type, a solution type, an emulsion type, and a dispersion type, and the property is any of film / sheet form, powder form, solid form, etc. Further, the bonding mechanism may be any of a chemical reaction type, a solvent volatilization type, a heat melting type, and a hot pressure type. Thus, the adhesive can be applied by, for example, a roll coating method, a gravure roll coating method, a kiss coating method, a coating method such as others, a printing method, or the like. -10 g / m @ 2 (dry state) is desirable.

Adhesive layers (adhesive resins) used in the coextrusion method include terpene and rosin hot melt resins, maleic anhydride modified polyolefin resins, (meth) acrylate modified polyolefin resins, modified hydrogenated petroleum Resin or the like is used. Such resins are sold under the product name Admer from Mitsui Chemicals, Inc. or as the product name Modiper from NOF Corporation. In addition, when PVDF-based resin is used as the fluororesin, a resin having improved adhesion with other resins by copolymerization or modification can be used. In such a case, the adhesive layer is omitted, and coextrusion is performed. Multiple layers are also possible. Examples of such an adhesion-improved PVDF resin include JP-T 2010-500440, JP-A-2005-15793, JP-A-2005-162330, EP0214880B1, JP-A-2008-239998, JP-A-2002-338713. The resin described in each of the above publications can be exemplified. Moreover, it can be purchased from Arkema as Kynar (registered trademark) ADX120.

As another adhesion method, a novel adhesion method in which a silane coupling agent is kneaded into a resin or applied to a resin sheet is disclosed herein. In the present invention, a known coupling agent can be used. Examples of such a coupling agent include a silane coupling agent, a titanate coupling agent, and an isocyanate coupling agent. Preferably, a silane coupling agent is used. Such silane coupling agents can be obtained from Shin-Etsu Chemical Co., Ltd., Dow Corning Co., and Evonik. A silane coupling agent is a silane compound having a functional group and a hydrolytic condensable group in the molecule. Examples of the functional group include vinyl groups such as vinyl, methacryloxy, acryloxy, and styryl, amino groups, epoxy groups, mercapto groups, sulfide groups, isocyanate groups, and halogens. Considering high adhesiveness with glass, the functional group is preferably a vinyl group, an amino group or an epoxy group, more preferably an amino group or an epoxy group, and most preferably an amino group. One or more of these functional groups may be present in the molecule. These coupling agents can be used alone or in combination of two or more.

Examples of the silane coupling agent having a vinyl group as a functional group include vinyltrimethoxysilane and vinyltriethoxysilane. An example of the silane coupling agent having a styryl group as a functional group is p-styryltrimethoxysilane. An example of a silane coupling agent having an acryloxy group as a functional group is 3-acryloxypropyltrimethoxysilane. Examples of the silane coupling agent having a methacryloxy group as a functional group include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacryloxypropylmethyldiethoxysilane. Can be illustrated. As the silane coupling agent having an epoxy group as a functional group, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4) -Epoxycyclohexyl) ethyltrimethoxysilane. Examples of the silane coupling agent having an amino group as a functional group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and N-2. -(Aminoethyl) -3-aminopropylethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldiethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N -2- (aminoethyl) -3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, bis (3-trimethoxysilylpropyl) amine, bis (3-triethoxysilylpropyl) amine, N- (n-butyl) -3-aminopropyltrimethoxysilane It can be exemplified.
The above is an example having a methoxy group or an ethoxy group as a hydrolytic condensable group, but a triisopropoxy group or an acetoxy group can also be used.
Although there is no restriction | limiting in particular in the usage-amount of a silane coupling agent, When adding to resin by kneading | mixing etc., generally it is used in 0.05 mass%-10 mass% with respect to resin. When applied, it is generally used in the range of 0.1 g / m2 to 20 g / m2.
A novel adhesion method of the cross-copolymer resin sheet of the support layer and the fluororesin sheet of the protective layer, characterized in that a coupling agent is added or applied, and further irradiated with energy rays as necessary. Street.

When adding and kneading the coupling agent to the cross-copolymer-based resin and / or the fluororesin, a known method for adding the additive to the resin can be used as the method. Industrially, for example, a twin screw extruder, a Banbury mixer, a roll molding machine, or the like can be used. Thereafter, it can be formed into a sheet by a known molding method such as inflation molding, extrusion molding, T-die molding, calender molding, roll molding, press molding or the like.
When a coupling agent is applied to a sheet made of a cross-copolymer-based resin and / or a fluororesin, any known method can be used as the application method. Examples of the application method include known methods such as gravure coating, roll coating, dip coating, and spraying. In this case, the coupling agent may be used after diluted in an appropriate solvent or may be used without dilution.
Thereafter, these sheets can be irradiated with energy rays as necessary. By irradiating the energy beam, the interlayer adhesive force can be expected to increase and stabilize. The energy rays are irradiated to the resin sheet on which the coupling agent is added and kneaded or applied.
When a coupling agent is added and kneaded to the cross-copolymer resin and / or fluororesin, the adhesion between the cross-copolymer resin sheet of the support layer and the fluororesin sheet of the protective layer can be determined by coextrusion or a coupling agent. It is preferable to carry out by an extrusion laminating method by extrusion of a resin added and kneaded, and particularly economically most preferred to carry out by a coextrusion method. When a coupling agent is applied to the cross-copolymer resin and / or the fluororesin, the adhesion between the cross-copolymer resin sheet of the support layer and the fluororesin sheet of the protective layer may be thermal lamination or a coupling agent. Extrusion lamination to the coated resin sheet is preferable, and thermal lamination is particularly preferable.

Examples of energy rays used in the present invention include electron beams, gamma rays, X rays, ultraviolet rays, neutron rays, α rays, infrared rays, and visible rays. These energy rays can be irradiated using a known apparatus. In the present invention, an electron beam is preferably used. The acceleration voltage of the electron beam is generally in the range of 10 keV to 5000 keV, and the irradiation dose is generally in the range of 1 kGy to 500 kGy.
This acceleration voltage is appropriately controlled according to the thickness of the sheet. In the present invention, when the purpose is to provide adhesion by strengthening the interaction between the resin near the surface and the coupling agent by electron beam treatment, the acceleration voltage of the electron beam is preferably lower, preferably 10 keV to 250 keV, More preferably, it is 10 keV-150 keV. The term “reinforcement of interaction” as used herein refers to enhancement of chemical or physical interaction that leads to adhesion enhancement, such as grafting, cross-linking, chemical reaction, molecular chain entanglement between resins and coupling agents in the vicinity of the surface. Irradiation of energy rays is performed in the same way when adding a coupling agent to a resin or when applying it to a sheet. However, when the purpose is to strengthen the interaction only in the vicinity of the resin, the efficiency of using the coupling agent From the viewpoint of the height, it is preferable to apply a coupling agent. In the case of application of a coupling agent, the energy beam is applied to the application surface.

In the present invention, a crosslinking aid can be further added or applied as necessary. Crosslinking aids that can be used are known crosslinking aids such as triallyl isocyanurate, triallyl cyanurate, N, N′-phenylenebismaleimide, ethylene glycol di (meth) acrylate, propanediol di (meth) acrylate, Examples include butanediol di (meth) acrylate, hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, and trimethylolpropane tri (meth) acrylate. These crosslinking aids may be used alone or in combination of two or more. When the crosslinking aid is blended, the content thereof is not particularly limited, but it is usually preferably in the range of 0.01 to 5% by mass with respect to the total mass.

A cross-copolymer-based resin, particularly a compound comprising a cross-copolymer and a polyphenylene ether-based resin, which is a support layer of the back protective sheet of the present invention, exhibits good adhesion to an EVA sealing material. That is, in the vacuum laminating (EVA cross-linking) step in the manufacturing process of the solar cell, it is easily bonded to the EVA sealing material, so that the manufacturing of the solar cell is facilitated and the reliability can be improved. Since the stretched PET resin widely used for the support layer does not have sufficient adhesiveness with the EVA sealing material, it is necessary to further provide an adhesive layer such as LDPE on the stretched PET resin. Can provide a back surface protection sheet having a simpler structure.

The back surface protection sheet of the present invention obtained by the sheet configuration and the manufacturing method shown above has high electrical insulation and water vapor barrier properties in addition to a simple layer configuration and ease of manufacture. In addition, the dielectric breakdown voltage in the vertical direction (from the back surface protective layer to the sealing material layer) of this sheet can be 20 kV or more, preferably 25 kV or more per actual sheet thickness. The water vapor transmission rate in the longitudinal direction (from the back surface protective layer to the sealing material layer) of the present sheet is specifically a low water vapor transmission rate of 10 g / m ² · day or less (per actual sheet thickness). Therefore, it is preferable because water vapor can be prevented from entering from the back surface of the photovoltaic power generation module. The water vapor transmission rate was determined under the conditions of 40 ° C. and 90% humidity according to the JISZ0208 cup method.

EXAMPLES Hereinafter, although an Example demonstrates this invention, these Examples do not limit this invention.
<Raw resin>
The raw material resins used in Examples and Comparative Examples are as follows.
The following cross copolymers were produced by the production methods described in WO2000 / 37517 or WO2007 / 139116, and the following compositions were similarly determined by the methods described in these publications. These cross copolymers are obtained by conducting anionic polymerization in the presence of an ethylene-styrene-divinylbenzene copolymer obtained by coordination polymerization and a styrene monomer, and an ethylene-styrene-divinylbenzene copolymer chain and polystyrene. A copolymer having a chain. Hereinafter, in order to define a cross copolymer, the styrene content, divinylbenzene content, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) of the ethylene-styrene-divinylbenzene copolymer used, the cross copolymer The ethylene-styrene-divinylbenzene copolymer content, polystyrene chain molecular weight (Mw), and molecular weight distribution (Mw / Mn) are shown. The total styrene content is a total content of the styrene contents contained in the ethylene-styrene-divinylbenzene copolymer chain and the polystyrene chain contained in the cross copolymer.

<Cross copolymer A>
Ethylene-styrene-divinylbenzene copolymer styrene content 25 mol%, divinylbenzene content 0.035 mol%, Mw = 90000, Mw / Mn = 2.3
Content of ethylene-styrene-divinylbenzene copolymer of 67% by mass,
Polystyrene chain Mw = 44000, Mw / Mn = 1.2
Total styrene content 70% by mass
<Cross copolymer B>
Ethylene-styrene-divinylbenzene copolymer having a styrene content of 26 mol%, a divinylbenzene content of 0.035 mol%, Mw = 14000, Mw / Mn = 2.3
80% by mass of ethylene-styrene-divinylbenzene copolymer,
Polystyrene chain Mw = 23000, Mw / Mn = 1.2
Total styrene content 65% by mass
<Cross copolymer C>
Ethylene-styrene-divinylbenzene copolymer styrene content 16 mol%, divinylbenzene content 0.045 mol%, Mw = 90000, Mw / Mn = 2.3
80% by mass of ethylene-styrene-divinylbenzene copolymer,
Polystyrene chain Mw = 26000, Mw / Mn = 1.2
Total styrene content 53% by mass

<Cross copolymer / PPE compound 1>
80 parts by mass of the above cross-copolymer A, 20 parts by mass of PPE resin (PX-100L, manufactured by Mitsubishi Engineering Plastics), antioxidant Irganox 1076, 0.2 parts by mass, UV absorber, light stabilizer, LA36, Each 0.3 parts by mass of LA77Y was obtained by kneading at 250 ° C. for 10 minutes with a 250 ml Banbury kneader (labor plast mill).
<Cross copolymer / PPE compound 2>
80 parts by mass of the above-mentioned cross-copolymer B, 20 parts by mass of PPE resin (PX-100L, manufactured by Mitsubishi Engineering Plastics), antioxidant Irganox 1076, 0.2 parts by mass, UV absorber, light stabilizer, LA36, Each 0.3 parts by mass of LA77Y was obtained by kneading at 250 ° C. for 10 minutes with a 250 ml Banbury kneader (labor plast mill).
<Cross copolymer / PPE compound 3>
50 parts by mass of the above cross-copolymer B, 50 parts by mass of PPE resin (PX-100F, manufactured by Mitsubishi Engineering Plastics), antioxidant Irganox 1076, 0.2 parts by mass, UV absorber, light stabilizer, LA36, Each 0.3 parts by mass of LA77Y was obtained by kneading at 250 ° C. for 10 minutes with a 250 ml Banbury kneader.
<Cross copolymer / PPE compound 4>
70 parts by mass of the above cross-copolymer C, 30 parts by mass of PPE resin (PX-100F, manufactured by Mitsubishi Engineering Plastics), antioxidant Irganox 1076, 0.2 parts by mass, UV absorber, light stabilizer, LA36, Each 0.3 parts by mass of LA77Y was obtained by kneading at 250 ° C. for 10 minutes with a 250 ml Banbury kneader.

<PVDF resin sheet>
DX film manufactured by Denki Kagaku Kogyo Co., Ltd .: PVDF (Akema Kyner 740) 80% by mass, polymethyl methacrylate resin (HBS000 manufactured by Mitsubishi Rayon Co., Ltd.) 20% by mass, and thickness 20 μm were used.

<Additives>
As the light stabilizer, LA36 (ultraviolet absorber) and LA77Y (light stabilizer) were both manufactured by ADEKA Corporation.
As an antioxidant, Irganox 1076 manufactured by Ciba Japan Co., Ltd. was used.

<Adhesive, adhesive resin>
Urethane-based adhesive A two-component curable urethane-based adhesive for laminating containing a benzophenone ultraviolet absorber (2.0% by weight) was used.

<Kneading>
Using a Banbury kneader (labor plast mill), a total of about 250 g of the cross-copolymer, PPE resin, and additives was kneaded at 250 ° C., 100 rpm for 10 minutes to prepare a resin composition.

<Create sheet>
The sample sheet of the cross-copolymer and compound 1 was molded under the conditions of a temperature of 200 ° C., a time of 3 minutes, and a pressure of 50 kg / cm 2 by a hot press method. The sample sheets of the cross copolymer compounds 2 and 3 were molded under the conditions of a temperature of 250 ° C., a time of 3 minutes, and a pressure of 50 kg / cm 2.

<Tensile test>
In accordance with JIS K-6251, the obtained film was cut into No. 2 1/2 type test piece shape, and the initial tensile elastic modulus was used at a tensile speed of 500 mm / min using a Shimadzu AGS-100D type tensile tester. The elongation at break and the strength at break were measured.

<A hardness>
The hardness was determined as a type A durometer hardness according to the JIS K-7215 plastic durometer hardness test method. This hardness is an instantaneous value.

<Multilayer sheet creation: Heat lamination>
For the cross copolymer / PPE compound, a press sheet having a width of 100 mm, a length of 200 mm, and a thickness of 0.2 mm was used. The heating lamination was performed by passing through a metal roll at 150 ° C., a rubber roll at 130 ° C., and a roll pressure of 0.3 MPa at 0.5 m / min. When a hot melt resin is used as the adhesive layer, a hot melt resin sheet with a thickness of 20 μm is sandwiched between a support layer and a protective layer sheet with a resin sheet with a thickness of 30 μm between the support layer and the protective layer sheet. It carried out on condition of this.
<Multi-layer sheet creation: urethane adhesive used>
On the other hand, when a urethane adhesive is used, a two-component curing type urethane adhesive is used, and this is coated by gravure roll coating so as to be 5 g / m @ 2 (dry state) on one sheet. did. The other sheet was faced and passed through the 50 ° C. roll for dry lamination. Thereafter, aging was performed at 50 ° C. for 5 days.

<Measurement of interlayer adhesion>
The multilayer sheet was cut into strips having a width of 15 mm and a length of 150 mm, and measurement was performed using a Shimadzu AGS-100D type tensile tester with a T-type peeling method and a tensile rate of 100 mm / min. A peel strength of 8 N / 15 mm or more was determined to pass the interlayer adhesion (circle mark in the table).

<Water vapor transmission rate>
The water vapor transmission rate was measured up to 100 hours under the conditions of 40 ° C. and 90% humidity according to the JISZ0208 cup method using a 0.5 mm thick sheet for the cross copolymer / PPE compound and the multilayer sheet as it was. .

<Volume resistivity>
The cross copolymer / PPE compound was a 0.5 mm thick sheet, and the multilayer sheet was measured as it was at room temperature (23 ° C.) according to JIS K6911.

<Dielectric breakdown voltage>
The cross copolymer / PPE compound was a 0.5 mm thick sheet, and the multilayer sheet was measured as it was at room temperature (23 ° C.) according to JIS C2110.

<Light resistance test>
Using a 0.5 mm thick sheet closely attached to a 3.2 mm thick tempered glass, it was carried out under the conditions of fade meter (light source carbon lamp clamp JIS D0205), no shower, black panel temperature 83 ° C., 1000 hours. . Light was irradiated from the glass surface.
The sample after the test was cut into strips, and a tensile test was performed at a tensile speed of 500 mm / min using an AGS-100D type tensile tester manufactured by Shimadzu Corporation in accordance with JIS K-6251. When the change in strength at break and elongation at break was 20% or less compared to before the weather resistance test, the test was accepted.

<Example 1>
A 0.2 mm-thick support layer sheet obtained by using the cross copolymer / PPE compound 1 and a PVDF resin sheet as a protective layer were bonded with a urethane adhesive. It was kept at 50 ° C. for 5 days to stabilize the urethane adhesive layer and obtain a back protective sheet. When the interlayer adhesion force at the interface between the support layer and the protective layer was measured, the protective layer sheet was destroyed with a peel strength of about 10 N / 15 mm or more.

<Example 2>
In the same manner as in Example 1, except that the support layer sheet and the PVDF resin sheet as the protective layer were adhered to each other using a hot melt resin sheet. That is, a hot melt resin sheet having a thickness of 20 μm was sandwiched between the support layer sheet and the PVDF resin sheet, and multilayered by the above heating lamination to obtain a back protective sheet. When the interlayer adhesion force at the interface between the support layer and the protective layer was measured, the protective layer sheet was destroyed with a peel strength of about 10 N / 15 mm or more.

<Examples 3, 4, and 5>
A support layer sheet having a thickness of 0.30 mm obtained using the cross copolymer / PPE compounds 2, 3, and 4 and a PVDF resin sheet as a protective layer were laminated and bonded with a urethane adhesive. It was kept at 50 ° C. for 5 days to stabilize the urethane adhesive layer and obtain a back protective sheet. When the interlayer adhesion force at the interface between the support layer and the protective layer was measured, the protective layer sheet was destroyed with a peel strength of about 10 N / 15 mm or more.

<Example 6>
A silane coupling agent was applied to a 0.30 mm thick support layer sheet obtained using the cross copolymer / PPE compound 2 as follows.
A silane coupling agent (1146 manufactured by Evonik) was dissolved in cyclohexane at a concentration of 25% by mass to prepare a coating solution. The cyclohexane solution was applied to the above sheet with an opening thickness of 4.6 microns using a bar coater. Then, it was dried overnight in a draft.
This sheet and a PVDF resin sheet (corona-treated) as a protective layer were adhered by the above heating lamination to obtain a back protective sheet. When the interlayer adhesion force at the interface between the support layer and the protective layer was measured, the protective layer sheet was destroyed with a peel strength of about 10 N / 15 mm or more.

<Example 7>
A silane coupling agent was applied to a 0.30 mm thick support layer sheet obtained using the cross copolymer / PPE compound 2 as follows.
A silane coupling agent: 3-aminopropyltriethoxysilane (Shin-Etsu Chemical KBE-903) was dissolved at a concentration of 2% by mass with respect to cyclohexane to prepare a coating solution. The cyclohexane solution was applied to the above sheet with an opening thickness of 45.7 microns using a bar coater. Then, it was dried overnight in a draft.
The surface of the obtained sheet on which the coupling agent was applied was irradiated once with an electron beam of 50 kGy at an acceleration voltage of 125 kV. Several days after the irradiation, the sheet and the PVDF resin sheet (corona-treated) as a protective layer were adhered by the above heating lamination to obtain a back protective sheet. When the interlayer adhesion force at the interface between the support layer and the protective layer was measured, the protective layer sheet was destroyed with a peel strength of about 10 N / 15 mm or more.

<Example 8>
A 0.30 mm thick support layer sheet obtained by using the cross copolymer / PPE compound 2 and a PVDF resin sheet as a protective layer are bonded to a resin film (Nippon Corporation Modiper A4100, thickness 30 μm). Were bonded together by the above heating lamination. When the interlayer adhesion force at the interface between the support layer and the protective layer was measured, the protective layer sheet was destroyed with a peel strength of about 10 N / 15 mm or more.

<Comparative Example 1>
Various measurements were performed using a back sheet having a three-layer structure of PVF (20 microns) / PET (250 microns) / PVF (20 microns).

Table 1 shows the basic physical properties of the cross-copolymer and cross-copolymer / PPE compound used in the above examples. Storage elastic modulus, electrical insulation, and water vapor permeability obtained using a 0.5 mm thick sheet The results are shown in Table 2. Tables 3 and 4 show the interlayer adhesion, volume resistivity, dielectric breakdown voltage, and water vapor transmission rate of the back surface protective sheet and the comparative example back surface protective sheet obtained in each example.

<Example 9>
A 0.3 mm-thick support layer sheet obtained by using the cross-copolymer / PPE compound 2 and an EVA sealing material sheet (thickness 0.4 mm) were superposed and 0.1 MPa in a vacuum laminator manufactured by NPC. Then, a vacuum laminating process was performed at 150 ° C. for 30 minutes to crosslink the sealing material layer. Thereafter, when the interlayer adhesive force at the interface between the support layer and the sealing material layer was measured, it was confirmed that the peel strength was about 20 N / 15 mm or more.

It can be seen that the back surface protective sheet of this example exhibits a relatively simple structure, but also exhibits excellent mechanical properties and heat resistance as well as high insulation properties (volume resistivity, dielectric breakdown voltage). Moreover, the adhesiveness with the EVA sealing material is also good.

Claims (7)

A back surface protective sheet for a solar cell power generation module , in which at least a protective layer made of a fluorine-based resin and a support layer made of a cross-copolymer-based resin are bonded via an adhesive. The back surface protection sheet for solar cell power generation modules according to claim 1, wherein the adhesive is selected from a two-component urethane adhesive, a terpene hot melt adhesive, and a silane coupling agent. The back protective sheet for a photovoltaic power generation module according to claim 1 or 2 , wherein the cross copolymer used for the cross copolymer resin is composed of an aromatic vinyl compound and an olefin monomer. Cross copolymer resin is composed of the cross-copolymer and at least one or more thermoplastic resins, claim 1-3, characterized in that they are composed of a resin composition comprising a cross-copolymer 40 wt% or more The back surface protection sheet for solar power generation modules as described in any one of these . 4. Photovoltaic module according to wherein the thermoplastic resin is a polyphenylene ether resin - the back protective sheet for a Le. The back protective sheet for a photovoltaic power generation module according to any one of claims 1 to 5, wherein the fluororesin is a polyvinylidene fluoride (PVDF) resin. A solar power generation module comprising the back surface protection sheet for a solar power generation module according to any one of claims 1 to 6 as a constituent element.