JP5783599B2 - Sealing material integrated back protection sheet - Google Patents

Description

The present invention is a sheet member in which a back surface sealing material for a solar power generation module and a back surface protection sheet are integrated, and relates to a solar cell module using this sheet member. More specifically, the sheet member is excellent in various properties such as strength, weather resistance, heat resistance, water 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. In such a multi-layer lamination process, it takes time to align each member sheet and to deaerate the layers, and there is a demand for further simplification of the sheet configuration.

The front and back surface sealing material layers that insulate and protect photovoltaic power generation elements and electrical wiring are made of a relatively soft resin, and are currently mainly made of an ethylene-vinyl acetate copolymer (EVA resin). Is used. This encapsulant protects thin and fragile elements and electrical wiring from thermal expansion, vibration and deformation, and electrically insulates them due to its softness. The surface sealing material is also required to be transparent. In an ethylene copolymer having excellent weather resistance, transparency and softness are achieved by copolymerization of a comonomer, however, the melting point is lowered and heat resistance becomes insufficient. For this reason, in the production of a photovoltaic module, the resin is crosslinked with a crosslinking material such as a peroxide contained in the sealing material after the element is thermally sealed. In this way,
Fluidity is required at the time of sheet molding, and it is necessary to suppress cross-linking at the initial stage of sealing in order to maintain fillability, and conversely, it is necessary to ensure cross-linking when sealing is completed. It is narrow and sometimes gives rise to molding problems, poor crosslinking during sealing, and poor adhesion. Further, in the sealing material using the present crosslinked EVA resin, it has been pointed out as one of the causes of cost increase that the crosslinking process takes time and effort. Furthermore, problems in securing reliability due to metal corrosion due to insufficient electrical insulation (volume resistivity and dielectric breakdown voltage) of EVA resin itself and generation of acetic acid due to hydrolysis have been pointed out.

The back surface protective sheet itself is also provided with an outermost protective layer, that is, a fluorine-based resin layer or a PET resin layer excellent in weather resistance and stain resistance, and an aluminum layer or a barrier resin layer which is a gas barrier layer inside if necessary, Further, a support layer (mainly made of stretched PET resin) for imparting mechanical strength and heat resistance to the inner side, and further, a low density polyethylene which is an adhesive layer for guaranteeing adhesion to the EVA sealing material on the inner side It has a complex multilayer structure called layers. 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, a new simpler sheet that has excellent properties such as strength, weather resistance, heat resistance, water resistance, moisture proofing, and antifouling properties, and that can further reduce module reliability, manufacturability, and manufacturing costs. Configuration is required.
Various studies have been made in order to solve the above-described problems. For example, there is provided a sealing material-integrated back surface protection sheet having a function of a back surface sealing material made of an α-olefin copolymer and a back surface protection sheet. It is being considered.
(Patent Document 1)

JP 2004-214641 A

An object of the present invention is to provide a sealing material-integrated back surface protection sheet that solves the problems of a conventional method for producing a photovoltaic module and solves the problems of a conventional sealing material and a back surface protection sheet.

The present invention provides a sealing material-integrated back surface protection sheet in which a back surface sealing material composed of an aromatic vinyl compound-olefin copolymer and a back surface protection sheet are integrated. This sealing material-integrated back protective sheet has excellent properties such as softness of the sealing material layer, overall strength, weather resistance, heat resistance, electrical insulation, water vapor barrier properties, and chemical stability, and its simplicity There is a possibility that the structure and the easy manufacturing method, the reliability and ease of manufacturing of the module, and the manufacturing cost can be further reduced.

The present invention relates to a back surface sealing material (hereinafter sometimes simply referred to as a sealing material) composed of an aromatic vinyl compound-olefin copolymer, and a back surface integrated sheet integrated with a back surface protection sheet. It is a protective sheet. This backside protection sheet with integrated sealing material has a simpler layer structure and a thermoplastic process that does not require cross-linking, and backside protection for sealing material that has excellent electrical insulation and chemical stability, and has excellent softness and strength. It is a sealing material-integrated back surface protection sheet integrated with a sheet, and is excellent in economy and reliability, and is therefore suitable for a photovoltaic power generation module.

The present invention is a sealing material-integrated back surface protection sheet in which a back surface sealing material composed of an aromatic vinyl compound-olefin copolymer and a back surface protection sheet are integrated. This backside protective sheet with integrated sealing material integrates a thermoplastic process that does not require a simpler layer structure and cross-linking, and a sealing material that is excellent in electrical insulation and chemical stability with excellent softness and strength. It is the sealing material integrated back surface protection sheet. 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 sealing material will be described in detail. A back surface sealing material is a sealing material located in the back side of a photovoltaic power generation element seeing from the incident surface of sunlight. In the case of a single crystal or polycrystalline silicon type element (cell), the element is generally sandwiched between a front surface sealing material and a back surface sealing material and sealed. In the case of an amorphous silicon-based or compound-based thin film element, the cell is in close contact with the glass surface, and only the back surface sealing material is used. The thickness is generally in the range of 50 μm to 1 mm. In the case of a single crystal or polycrystalline silicon type device, the thickness is often in the range of 200 μm to 600 μm, and in the case of a thin film type device, the thickness is in the range of 50 μm to 400 μm.
The aromatic vinyl compound-olefin copolymer used for the back surface sealing material in the present invention is a copolymer obtained by copolymerizing each monomer of an aromatic vinyl compound and an olefin, and is derived from these monomers. A copolymer in which the content of the unit is 70% by mass or more, preferably 90% by mass or more, and most preferably 95% by mass or more of the entire copolymer mass. The manufacturing method of this copolymer is arbitrary.

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.

As the aromatic vinyl compound-olefin copolymer, a copolymer of ethylene and styrene is preferable. Examples of the aromatic vinyl compound-olefin copolymer used in the present invention include copolymers described in EP0416815A2, JP3659760, EP872492B1.

More preferably, a cross-copolymer is used as the aromatic vinyl compound-olefin copolymer. A cross-copolymer 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. -Aromatic vinyl compound-A copolymer having an aromatic polyene copolymer chain (may be described as a main chain) and an aromatic vinyl compound polymer chain (sometimes described as a side chain). . 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 95% 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%. 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.

When used as a sealing material, considerable heat resistance is required to stably hold the photovoltaic power generation element and wiring under conditions such as exposure to direct sunlight in summer. When the sealing material is used and sealing is performed using thermoplasticity without substantially crosslinking the resin, the storage elastic modulus of the resin at 120 ° C. is 1 × 10 ⁴ Pa or more, preferably 1 × 10. ^It needs to be ⁵ Pa or more. This storage elastic modulus can be easily obtained using a known viscoelasticity measuring apparatus. The above cross-copolymer can satisfy this condition without performing a crosslinking treatment and can be suitably used in the present invention.
Electrical insulation is important in ensuring 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 40 kV / mm or more. This is very high as compared with the conventional crosslinked EVA sealing material, and is suitable as a sealing material. Further, prevention of water vapor penetration is important for preventing electrical troubles such as corrosion and insulation failure. The encapsulant made of the present cross copolymer is suitable as an encapsulant 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. It is. 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 sealing material, the MFR value (200 ° C., weight 98N) of the raw material resin is not particularly specified, but generally 0.1 g / 10 min to 300 g / 10 min, substantially non-crosslinked Considering the heat resistance in the state, it is 0.1 g / 10 min or more and 100 g / 10 min or less. If it is lower than this, voids due to poor filling are likely to occur at the time of sealing, and if it is higher than this, there is a concern about insufficient heat resistance, that is, a creep phenomenon of solar cells or wiring in the environment. This MFR value can be easily estimated by those skilled in the art from known literature of the resin used, and can also be adjusted by adding a small amount of oil or plasticizer.

A known coupling material can be added or applied to the sealing material for the purpose of improving the adhesiveness with a photovoltaic power generation member (particularly glass). Examples of such a coupling agent include a silane coupling agent, a titanate coupling material, and an isocyanate coupling agent. Preferably, a silane coupling agent is used. Such a silane coupling agent can be obtained from Shin-Etsu Chemical Co., Ltd. or Dow Corning. 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. In view of adhesion to 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. These 1 type (s) or 2 or more types can also be used.

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.

Further, the sealing material is blended with a light-resistant agent 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. 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 back surface sealing material 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. Moreover, the back surface sealing material of this invention may be comprised from the multilayer sheet containing the sealing material layer containing the said white pigment.

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. For this purpose, the back surface sealing material can be filled with a known thermally conductive inorganic filler. 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 a thermoplastic photovoltaic power generator, the following “plasticizer” and “anti-aging agent” are used as necessary for the purpose of improving the properties as a sealing material. Can be added.

<Plasticizer>
The resin of the present invention or the sheet thereof can be blended with any known plasticizer conventionally used for vinyl chloride and other resins. Preferably used plasticizers are oils or oxygen-containing or nitrogen-containing plasticizers, preferably paraffinic oils, naphthenic oils, ester plasticizers, epoxy plasticizers, ether plasticizers, or amides. It is a plasticizer selected from plasticizers.

These plasticizers are relatively good in compatibility and hardly bled, and have a large plasticizing effect that can be evaluated by the degree to which the glass transition temperature is lowered, and can be suitably used.

The compounding amount of the plasticizer is 1 part by mass or more and 20 parts by mass or less, preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the resin of the present invention or the sheet thereof. If the amount is less than 1 part by mass, the above effect is insufficient. If the amount is more than 20 parts by mass, it may cause bleeding, excessive softening, and excessive stickiness. Moreover, the fluidity | liquidity of a sealing material can be improved by mix | blending a plasticizer. In particular, when the MFR value of the resin used is low, it is possible to adjust the MFR value to be suitable as a sealing material by adding a plasticizer within the above range.

<Anti-aging agent>
Suitable anti-aging agents include, for example, 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.

<Crosslinking>
In consideration of simplification of the sealing process and recyclability of the solar power generation device, it is preferable that the sealing material of the present invention is not substantially crosslinked even after sealing. The degree of crosslinking can be evaluated by the gel content. In the evaluation of the gel content with respect to the whole sheet, it is generally 50% or less, particularly preferably 30% or less. The gel content is determined according to ASTM D-2765-84. However, when higher heat resistance to the sheet itself is required or after sealing, further crosslinking treatment can be performed. The crosslinking treatment is generally performed by adding a crosslinking agent and a crosslinking aid to the thermoplastic sealing material, forming a film or sheet under the condition of a crosslinking temperature or lower, and crosslinking under a predetermined crosslinking condition after sealing the solar battery cell. I do. The thermoplasticity of the thermoplastic sealing material of the present invention is important in the process of sealing solar cells by melting and flowing in the sealing process. Subsequent crosslinking conditions are arbitrarily determined by the crosslinking material and crosslinking aid used. The cross-linking materials and cross-linking aids that can be used for the thermoplastic sealing material are those commonly used for ethylene resins, styrene resins, and styrene-ethylene copolymers, and are well known. Preferred crosslinking materials, crosslinking aids, and crosslinking conditions are described in, for example, JP-T-10-505621 (WO96 / 077681), JP-A-08-139347, and JP-A-2000-18381. The sealing material of the present invention subjected to such crosslinking treatment loses the merit of using recyclability, but releases high corrosive substances such as high water vapor barrier property (low water vapor permeability), high volume resistivity, and acetic acid. This is advantageous in terms of improving the reliability of the solar cell.

In order to manufacture the sealing material sheet, a known molding method such as extrusion molding, T-die molding, calendar molding, roll molding, inflation molding or the like can be employed.
Examples of the solar cell using the encapsulant include crystalline silicon type, amorphous silicon type, compound type, and organic type solar cells. High water vapor barrier properties (low water vapor permeability), high volume resistivity, and corrosion of acetic acid, etc., even in the case where solar cells adhere to the surface glass, such as thin film solar cells, and the sealing material does not require transparency The point that the active substance is not liberated is advantageous in terms of improving the reliability of the solar cell.
In addition to the resin of the present invention or a sheet comprising the resin, other additives that are used in ordinary resins, for example, heat stabilizers, antioxidants, and the like, as long as the purpose of the present invention is not impaired. An antistatic agent, a filler, a colorant, a lubricant, an antifogging agent, a foaming agent, a flame retardant, a flame retardant aid and the like may be added.

Hereinafter, the back surface protective sheet of the sealing material-integrated back surface protective sheet of the present invention will be specifically described. The back surface protective sheet used here is generally a protective layer that is the outermost layer, a gas barrier layer that barriers water vapor or the like provided as necessary, a support layer that retains mechanical strength, and a sealing material that is provided as necessary. It is the multilayer sheet comprised from the contact bonding layer for ensuring adhesiveness of this.
Here, as the protective layer, 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, a 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, in the present invention, since the sealing material layer made of the cross copolymer has a high water vapor barrier property as described above, the gas barrier layer can be omitted, and the layer structure can be simplified.

Therefore, in a certain form of the present invention, the second layer is a support layer, but this support layer is generally 40 μm to 400 μm in thickness, preferably 40 μm to 200 μm, and is a polyester resin such as PET or PEN. Is generally used, and can also be used in the present invention based on known materials. In the case of a PET resin, a stretched sheet is used in order to impart heat resistance, but it is expensive and it is difficult to make a multilayer by coextrusion. 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 fluorine-based resin. In some cases, an LDPE or LLDPE layer for bonding with a sealing material made of EVA resin is provided.

In the present invention, a resin mainly composed of a cross copolymer (hereinafter referred to as a cross copolymer resin) is preferably used as the support layer. When this cross-copolymer-based resin is used as a support layer, it is easy to adhere to the cross-copolymer that is a sealing material layer, and there is a great merit in that the adhesive layer can be omitted. Specifically, the support layer and the sealing material layer can be directly multilayered by a coextrusion method (multilayer extrusion method), an extrusion lamination method, or a thermal lamination method. When the flexibility required for the encapsulant and the rigidity required for the support layer are different, the respective physical properties are independently adjusted appropriately and used, but in the case of a thin film type element, the encapsulant may be harder, The support layer may be integrated with the support layer so as to have rigidity. In general, dry lamination using a urethane-based adhesive is employed for bonding the support layer made of the present cross-copolymer-based resin and the fluorine-based resin, but a hot-melt-based adhesive resin can also be used. Details of this bonding method will be described later.

As mentioned above, the preferable specific example of the sealing material integrated back surface protection sheet which is this invention is as follows.
Since both the configuration examples 1 and 2 can omit the gas barrier layer and the adhesive layer with the sealing material, the configuration can be simplified and the manufacturing cost can be reduced. In the configuration example 1, an adhesive layer between the support layer and the sealing layer is unnecessary, which is advantageous. In the configuration example 2, the support layer and the sealing material layer are integrated, which is further advantageous.
Structure example 1 Protective layer: Fluorine resin / support layer: Cross copolymer resin / back side sealing material: Cross copolymer structure example 2 Protective layer: Fluorine resin / support layer / sealing material: Cross copolymer resin In the present invention, the fluororesin of the protective layer can be eliminated, and the cross-copolymer resin of the support layer can be used as the outermost protective layer.
Configuration Example 3 Protective Layer / Support Layer: Cross Copolymer Resin / Back Sealing Material: Cross Copolymer Further, in Configuration Example 1, the support layer and the back surface sealing material are multilayered, and in Configuration Example 3, the protective layer / support layer It is possible to employ a coextrusion method that is economically advantageous for multilayering the backside sealing material.
In addition, in the multi-layering of the protective layer and the support layer in Structural Example 1 and in the multi-layering of the protective layer and the supporting layer / sealing material in Structural Example 2, an economically advantageous coextrusion method can be employed depending on the bonding method used. Therefore, it is advantageous and preferable.

The cross-copolymer-based resin used for the support layer includes the same cross-copolymer as that used for the sealing material layer, and the cross-copolymer is at least 20% by mass, preferably 50% by mass or more. It is the concept which also includes the resin composition to contain. Particularly suitable as such a resin composition is a composition with a polyphenylene ether (PPE) resin described in WO2009 / 128444. The resin composition of the cross-copolymer and PPE maintains the high electrical insulation properties (volume resistivity, dielectric breakdown voltage) of the cross-copolymer itself, and maintains the low water vapor transmission rate while maintaining rigidity (tensile test). The initial elastic modulus) and heat resistance are improved, and it is suitable as a support layer for the back protective sheet. Moreover, the point which has the flame retardance derived from PPE resin is also preferable. The initial elastic modulus of the cross-copolymer used as the support layer of the back surface protection sheet is preferably 50 MPa to 2 GPa, particularly preferably 100 MPa to 1 GPa, and the elongation at break is preferably 10% to 300%. 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. needs to be 1 × 10 ⁶ Pa or more, preferably 1 × 10 ⁷ Pa or more. This storage elastic modulus can be easily obtained using a known viscoelasticity measuring apparatus. Further, the volume resistivity of the cross-copolymer 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 / 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 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 same white pigment as described in the description of the sealing material can be added to the support layer of the back surface protection sheet for the purpose of reflecting and scattering incident light. The support layer of the back surface protective sheet may contain the above light-proofing agent, and other additives that are used in ordinary resins, for example, heat, as long as the object of the present invention is not impaired. Stabilizers, antioxidants, antistatic agents, fillers, colorants, lubricants, antifogging agents, foaming agents, flame retardants, flame retardant aids and the like may be added.

Arbitrary or a well-known method can be used for multilayering of a back surface sealing material and a back surface protection sheet. Examples of such a method include a dry lamination method, an extrusion laminating method, and a coextrusion method. In order to impart adhesiveness, an appropriate adhesive layer made of a resin or an adhesive may be used as necessary.
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.

As the adhesive layer (adhesive resin) used in the coextrusion method, a terpene-based or rosin-based hot melt resin, a maleic anhydride-modified polyolefin resin, a modified hydrogenated petroleum resin, or the like is used. In addition, when PVDF resin is used as the fluorine-based resin, it is possible to use a resin whose adhesion to other resins is improved by copolymerization or modification. In such a case, the adhesive layer is omitted, and coextrusion is performed. It is also possible to increase the number of layers. 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.

The sealing material-integrated back protective sheet of the present invention obtained by the sheet configuration and the manufacturing method described above has high electrical insulation and water vapor barrier properties in addition to a simple layer configuration and ease of manufacture. It has the weather resistance, heat resistance, and softness of the sealing material layer necessary for a photovoltaic power generation module. Specifically, the volume resistivity of the sealing material layer used inside the sheet is 1 × 10 ¹⁶ Ω · cm or more. The volume resistivity in the longitudinal direction (from the back surface protective layer to the sealing material layer) of this sheet is also 1 × 10 ¹⁶ Ω · cm or more. Further, the dielectric breakdown voltage in the longitudinal direction (from the back surface protective layer to the sealing material layer) of the present sheet can be 40 kV / mm or more. 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 1>
Ethylene-styrene-divinylbenzene copolymer styrene content 15 mol%, divinylbenzene content 0.040 mol%, Mw = 70000, Mw / Mn = 2.2,
Content of ethylene-styrene-divinylbenzene copolymer of 67% by mass,
Polystyrene chain Mw = 35000, Mw / Mn = 1.2
Total styrene content 60% by mass
<Cross copolymer 2>
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
70% by mass of total styrene content,
<Cross copolymer 3>
Styrene content of ethylene-styrene-divinylbenzene copolymer: 24 mol%, divinylbenzene content: 0.030 mol%, Mw = 15000, Mw / Mn = 2.2
Content of ethylene-styrene-divinylbenzene copolymer of 77% by mass,
Polystyrene chain Mw = 26000, Mw / Mn = 1.2
<Cross copolymer / PPE compound>
The cross copolymer 2 was obtained by kneading 80 parts by mass and 20 parts by mass of PPE resin (PX-100L, manufactured by Mitsubishi Engineering Plastics) in a 250 ml Banbury kneader at 250 ° C. for 10 minutes.

<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.
Terpene hot melt resin Hirodine 7589R film manufactured by Yasuhara Chemical Co., Ltd., having a thickness of 30 microns was used.

<Kneading>
Using a Banbury kneader (labor plast mill), a total of about 250 g of the cross copolymer and the additive was kneaded at 180 ° C., 100 rpm for 5 minutes to prepare a resin composition.
In the case of the cross copolymer and PPE, kneading was performed at 250 ° C., 100 rpm for 10 minutes.

<Create sheet>
The sample sheet of the cross copolymer and its compound was molded by a hot press method (temperature 200 ° C., time 3 minutes, pressure 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.

<Multi-layer sheet creation>
As the cross copolymer, a press sheet having a width of 100 mm, a length of 200 mm, and a thickness of 0.4 mm was used. 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 carried out 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 using a hot melt resin as the adhesive layer, a hot melt resin sheet having a thickness of 20 microns was used, and the same conditions were 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 is determined according to the JISZ0208 cup method using a sheet of 0.5 mm thickness for the cross copolymer and its compound, and using the multilayer sheet as it is (thickness of about 0.5 to 0.8 mm). , Measured at 40 ° C. and 90% humidity for up to 100 hours. From the relationship between the actual thickness (unit: mm, L) of the sheet and the actually measured value (Po), the water vapor transmission rate (Pn) per 1 mm thickness was determined using the following equation.
Pn = Po × L

<Volume resistivity>
The cross-copolymer and its compound were 0.5 mm thick sheets, and the multilayer sheet was measured at room temperature (23 ° C.) according to JIS K6911 with the actual thickness of the obtained sheet.

<Dielectric breakdown voltage>
The cross-copolymer and its compound were 0.5 mm thick sheets, and the multilayer sheet was measured at room temperature (23 ° C.) according to JISC2110 with the actual thickness of the obtained sheet. The dielectric breakdown voltage per 1 mm thickness was obtained on the assumption that it was proportional to the thickness.

<Light resistance test>
Using a 0.5 mm thick film adhered to a tempered glass having a thickness of 3.2 mm, a fade meter (light source carbon arc clamp JIS D0205), no shower, black panel temperature of 83 ° C., 1000 hours, was carried out. . 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>
Using the cross-copolymer 1, 0.2 parts by mass of the antioxidant Irganox 1076 and UV absorbers and light stabilizers as light-resistant agents, 0.3 parts by mass of LA36 and LA77Y, respectively, were kneaded with a Banbury kneader. A 0.4 mm thick sheet was obtained by hot pressing.
Cross copolymer 2, 80 parts by mass, 20 parts by mass of PPE resin, 0.2 part by mass of antioxidant, 0.3 parts by mass of UV absorber as light-resistant agent and 0.3 part by mass of light stabilizer each in a Banbury kneader To obtain a cross copolymer / PPE compound. A 0.2 mm thick sheet was obtained by hot pressing.
The cross copolymer sheet as the sealing material and the cross copolymer / PPE compound sheet as the support layer were multilayered by heating lamination to obtain a sealing material / support layer multilayer sheet. This multilayer sheet and the PVDF resin sheet as the protective layer were bonded with a urethane adhesive. The urethane adhesive layer was stabilized at 50 ° C. for 5 days to obtain a sealing material-integrated back protective sheet.

<Example 2>
In the same manner as in Example 1, except that the cross copolymer 2 was used instead of the cross copolymer 1 of the sealing material, and the resulting PVDF resin sheet as the sealing material / support layer multilayer sheet and protective layer was used. Adhesion was performed using a hot melt resin sheet. That is, a hot melt resin sheet was sandwiched between the encapsulant / support layer multilayer sheet and the PVDF resin sheet, and multilayered by heating lamination to obtain an encapsulant-integrated back protective sheet.

<Example 3>
Adhesion of the PVDF resin sheet as a protective layer was performed in the same manner as in Example 1 using the cross-copolymer sheet obtained in the same manner as in Example 1 as the sealing material, and the supporting material was omitted. A body-shaped back protection sheet was obtained.

<Example 4>
A cross copolymer / PPE compound, which is a support layer and a protective layer, was prepared as follows. Cross copolymer 2, 80 parts by mass and 20 parts by mass of PPE resin, 0.2 parts by mass of antioxidant, 0.5 parts by mass of UV absorber as light-resistant agent, 0.5 parts by mass of light stabilizer, and 10 parts by mass of titanium oxide white pigment Was kneaded in a Banbury kneader under the above conditions to obtain a cross copolymer / PPE compound. A 0.2 mm thick sheet was obtained by hot pressing. Each sheet of the present cross-copolymer / PPE compound and the cross-copolymer 1 as a sealing material was multilayered by heating lamination to obtain a sealing material-integrated back protective sheet.

<Comparative Example 1>
EVA sealing material and PVF (20 micron) / PET (250 micron) / PVF (20 micron) three-layer back sheet are pressure-bonded at a pressure of 0.1 MPa at 150 ° C. for 30 minutes, and the sealing material integrated back protection sheet Got.

Table 1 shows the basic physical properties of the cross copolymer and cross copolymer / PPE compound used in the above examples, and Table 2 shows the storage elastic modulus, electrical insulation, water vapor transmission rate, and weather resistance test results.
Table 3 shows the interlayer adhesion, volume resistivity, dielectric breakdown voltage, and water vapor transmission rate of the sealing material-integrated back surface protection sheet obtained in each example and comparative example.
The sealing material-integrated back protective sheet of the present example has a simpler structure, but exhibits superior insulating properties (volume resistivity, dielectric breakdown voltage) and superior water vapor barrier properties as compared with the comparative example. I understand.

Claims (7)

The back surface sealing material composed of an aromatic vinyl compound-olefin copolymer, and the back surface protection sheet including a support layer composed of a resin composition composed of a cross copolymer and a PPE resin. Sealing material integrated back surface protection sheet for photovoltaic module. The sealing material-integrated back protective sheet for solar power generation module according to claim 1, wherein the aromatic vinyl compound is styrene. The sealing material-integrated back protective sheet for solar power generation modules according to claim 1 or 2, wherein the olefin is ethylene. The sealing material-integrated back protective sheet for solar power generation modules according to claim 1, wherein the aromatic vinyl compound-olefin copolymer is a cross-copolymer mainly composed of styrene and ethylene. 2. The back protection sheet integrated with a sealing material for solar power generation module according to claim 1, wherein the back protection sheet includes a protection layer made of a fluororesin. The sealing material-integrated back protective sheet for a solar power generation module according to claim 5, wherein the fluororesin comprises a polyvinylidene fluoride (PVDF) resin. The photovoltaic power generation module which contains the sealing material integrated back surface protection sheet for photovoltaic power generation modules as described in any one of Claims 1-6 as a component.