JP6609968B2 - Back surface protection sheet for modules for solar cells - Google Patents

Description

  The present invention relates to a back surface protection sheet for a solar cell module. More specifically, the present invention relates to a multilayer back surface protective sheet in which an aluminum foil is laminated as an intermediate layer.

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

  Among these components, the back surface protection sheet is required to have high weather resistance and to have high moisture resistance and gas barrier properties in order to protect the solar cell element from moisture, oxygen, and the like. From such a viewpoint, conventionally, a back surface protection sheet in which a metal foil such as an aluminum foil is laminated on a base material having weather resistance has been disclosed as a back surface protection sheet. (See Patent Document 1)

  Moreover, the back surface protection sheet for solar cell modules using the adhesive agent containing the resin containing the molecular chain derived from polyester diol as an adhesive layer is disclosed (refer patent document 2). By using an adhesive containing a resin containing a molecular chain derived from a polyester diol, the adhesiveness of the adhesive layer and the weather resistance of the back protective sheet on which the adhesive layer is laminated can be improved. .

JP 2002-134770 A JP 2012-079902 A

  By the way, a solar cell module is manufactured by laminating | stacking a back surface protection sheet, a sealing material sheet | seat, a solar cell element, etc., and carrying out heat lamination. In that case, when the back surface protection sheet which laminated | stacked metal foils, such as aluminum foil, was used as a back surface protection sheet, there existed a problem that a wrinkle generate | occur | produced in the back surface protection sheet at the time of thermal lamination.

  When wrinkles are generated in the back surface protective sheet, a gap is generated between the back surface protective sheet and the sealing material sheet laminated on the back surface protective sheet, and water vapor easily enters the solar cell module. When water vapor enters the solar cell module, the wiring corrodes and the electrical resistance increases. Therefore, the power generation efficiency as a solar cell module falls and performance is reduced.

  For this reason, there has been a strong demand for the development of a back surface protection sheet that can suppress the generation of wrinkles during thermal lamination even when a back surface protection sheet laminated with aluminum foil is used.

  The inventors of the present invention focused on the fact that the aluminum foil used for the back surface protection sheet has a smaller volumetric variation rate due to heat than the resin. And as a result of intensive studies to solve the above problems, the present inventors have found that the adhesive layer melts below the temperature of the thermal laminate, thereby increasing the rate of fluctuation of the volume of the adhesive layer during thermal lamination. It was discovered that wrinkles are more likely to occur on the back protective sheet during thermal lamination due to the relationship between the aluminum foil having a small volume expansion and contraction and the adhesive layer having a large volume expansion and contraction.

  In addition to suppressing the generation of wrinkles, the present inventor has a back surface protection sheet having a multilayer structure in order to make the back surface protection sheet satisfying heat dissipation, weather resistance, and insulation, and the thickness of each resin sheet layer of the back surface protection sheet. Tried to optimize. As a result, the present inventors use a predetermined adhesive for the adhesive layer, and solve the wrinkle generation problem if it is a back surface protection sheet that optimizes the thickness of each resin sheet layer of the back surface protection sheet, It has been found that the sheet is a back surface protection sheet satisfying heat dissipation, weather resistance, and insulation, and the present invention has been completed. More specifically, the present invention provides the following.

(1) A back surface protection sheet for a solar cell module including a configuration in which an aluminum foil layer is laminated between an adhesive layer between a first resin sheet layer and a second resin sheet layer, the first resin The film thickness of the sheet layer is 45 μm or more and 85 μm or less, the film thickness of the second resin sheet layer is 35 μm or more and 85 μm or less, and the adhesive layer is 110 ° C. or more and 150 ° C. or less measured by the following DMA evaluation method. The back surface protection sheet characterized by the minimum value of the loss elastic modulus in the range of more than 100Pa.
DMA evaluation method: Measurement frequency: 1 Hz, temperature increase rate from −20 ° C. at a temperature increase rate of 3 ° C./min, and loss elastic modulus of 110 ° C. to 150 ° C. is measured.

  (2) The adhesive layer includes a polyurethane resin and a polycarbonate diol resin, and the polyurethane resin is 1,6 hexanediol with respect to 100 parts by mass of the aliphatic polycarbonate diol having a number average molecular weight of 1000 to 2000. The back surface protective sheet according to (1), which is a polyurethane diol having a number average molecular weight of 7000 to 13000 obtained by reacting 5 parts by mass or more and 15 parts by mass or less with isophorone diisocyanate.

  (3) The back surface protective sheet according to (1) or (2), wherein the first resin sheet layer and the second resin sheet layer are polyethylene terephthalate.

  (4) A solar cell module in which the back surface protective sheet according to any one of (1) to (3) is disposed in the outermost layer.

  According to the present invention, an adhesive layer having a minimum loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower as measured by the DMA evaluation method and optimized for the film thickness of the resin sheet of the back surface protective sheet; By doing so, it is possible to obtain an excellent back surface protection sheet capable of suppressing the generation of wrinkles even when the back surface protection sheet is thermally laminated.

It is a schematic diagram of the cross section which shows an example of the laminated constitution of the solar cell module of this invention. It is a schematic diagram of the cross section which shows an example of the layer structure of the back surface protection sheet for solar cell modules of this invention. It is a measurement result of the TMA test of TD direction MD direction of Example 1 and Comparative Example 7.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. can do.

<Basic configuration of solar cell module>
First, the structure of the solar cell module in which the back surface protection sheet for solar cell modules is used is demonstrated. FIG. 1 is a schematic cross-sectional view illustrating an example of the layer structure of a solar cell module 1 that is an embodiment of the invention. As shown in FIG. 1, the solar cell module 1 includes a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6, which are sequentially stacked from the light receiving surface side. It becomes the composition. Since the back surface protection sheet 6 which is embodiment of this invention is arrange | positioned in the outermost layer in the solar cell module 1 in this way, it is essential to provide a high weather resistance and barrier property.

  The transparent front substrate 2 is generally a glass substrate as long as it maintains the weather resistance, impact resistance, and durability of the solar cell module 1 and transmits sunlight with high transmittance. The sealing material layer composed of the front sealing material layer 3 and the back sealing material layer 5 is disposed in the solar cell module 1 in order to fix the position of the solar cell element 4 and alleviate external impact. It is a layer made of a resin base material. As the resin base material for forming the sealing material layer, polyolefin resins such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), and polyethylene can be used. Among them, EVA having a certain durability and the like, excellent in workability, and available at a relatively low cost has been widely used. However, in recent years, the problem of deterioration of water vapor barrier property, which is a defect of EVA, is solved. For this reason, polyolefin resins such as resins obtained by subjecting low-density polyethylene to a crosslinking treatment are also often used.

<Back protection sheet>
The back surface protection sheet 6 which is an example of the back surface protection sheet for solar cell modules of this embodiment is demonstrated using FIG.

  As shown in FIG. 2, the back surface protection sheet 6 includes a first resin sheet 61 that forms one outermost layer, an aluminum foil 62, and a second resin sheet 63 that forms the outermost layer opposite to the first resin sheet 61. The first resin sheet 61 and the aluminum foil 62 are in contact with each other via an adhesive layer (first adhesive layer 64a), and the aluminum foil 62 and the second resin sheet 63 are adhesive layers. It is in close contact via the (second adhesive layer 64b). By laminating the aluminum foil, a back protective sheet having gas barrier properties such as high water vapor barrier properties can be obtained. In this specification, the term “resin sheet” is used as the name of the resin processed into a sheet shape, but this term is used as a concept including a resin film.

  Here, the first resin sheet 61 is a resin sheet that is assumed to be a layer that is laminated in a mode of being in direct contact with the back sealing material layer 5 when integrated as the solar cell module 1 shown in FIG. is there. On the other hand, the second resin sheet 63 is a resin sheet that is supposed to be a layer disposed on the outermost layer side of the solar cell module 1. Therefore, at the time of integration as a solar cell module, the back surface protection sheet 6 is preferably laminated so that the second resin sheet 63 is disposed in the outermost layer. However, since the distinction between the first resin sheet 61 and the second resin sheet 63 in the back surface protection sheet 6 is simply a relative concept that defines one surface and the other surface, a book that will be described in detail below. As long as the structural requirements of the invention are satisfied, it is not essential in the present invention that the two resin sheets disposed in both outermost layers are resin sheets having different physical properties.

  The first adhesive layer 64a and the second adhesive layer 64b in the back surface protective sheet 6 have a minimum value of loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower measured by the following DMA evaluation method of more than 100 Pa. It is characterized by. The adhesive that forms such an adhesive layer will be described below.

  DMA evaluation method: Measurement frequency: 1 Hz, temperature increase rate from −20 ° C. at a temperature increase rate of 3 ° C./min, and loss elastic modulus of 110 ° C. to 150 ° C. is measured.

[adhesive]
The adhesive for forming the first adhesive layer 64a and the second adhesive layer 64b has a minimum value of loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower as measured by the DMA evaluation method of more than 100 Pa. Here, the DMA test is a test in which dynamic viscoelasticity is measured by a dynamic viscoelasticity measuring device, and the viscosity and elastic modulus of the layer are measured by periodically applying minute deformation to the adhesive layer. This is an evaluation method. In the present invention, the loss elastic modulus of the adhesive layer is measured by a DMA test. Specifically, the loss elastic modulus at each temperature is measured by raising the temperature from −20 ° C. at a measurement frequency of 1 Hz and a temperature raising rate of 3 ° C./min. And when the minimum value of the loss elastic modulus in the range of 110 ° C. or more and 150 ° C. or less is more than 100 Pa, the shape of the adhesive layer can be maintained without melting. When the minimum value of the loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower is 100 Pa or lower, the adhesive layer melts in the range of 110 ° C. or higher and 150 ° C. or lower. Can not be suppressed. By laminating the adhesive layer in which the minimum value of the loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower is over 100 Pa, the rate of fluctuation of the volume of the adhesive layer in the thermal lamination can be reduced. Therefore, generation | occurrence | production of the wrinkle of a back surface protection sheet can be suppressed.

  Examples of the adhesive that can form such an adhesive layer include an adhesive containing a main resin, a curing agent, and a solvent, and if necessary, other various additives. Examples of other additives include adhesion aids and the like. The adhesive is preferably a two-component type in which the main resin and the curing agent are mixed immediately before use. When forming the adhesive layer, the main resin reacts with the curing agent to be cross-linked and have a high molecular weight. Below, an example of the adhesive agent which can form the adhesive bond layer of this invention is demonstrated. The adhesive that can form the adhesive layer of the present invention is not limited to the following adhesives.

[Main resin]
As the main component of the adhesive, for example, one containing a mixture of polyurethane diol (A) and aliphatic polycarbonate diol (B) can be used. The polyurethane diol (A) and the aliphatic polycarbonate diol (B) constituting the main agent are both polyols having a hydroxyl group, and react with a curing agent having an isocyanate group to constitute an adhesive layer. Adhesiveness and weather resistance of the adhesive layer can be improved by using a mixture in which a predetermined amount of a specific polyurethane diol (A) and an aliphatic polycarbonate diol (B) is blended as the main agent.

  The main component polyurethane diol (A) is a polyurethane having a urethane structure as its repeating unit and having hydroxyl groups at both ends. The number average molecular weight of the polyurethane diol (A) is preferably 7000 or more and 13000 or less. When it is 7000 or more, it is preferable because the reactivity with the curing agent is good, and when it is 13000 or less, dissolution in a solvent is improved, which is preferable.

  The hydroxyl value of the polyurethane diol (A) is preferably in the range of 10 mgKOH / g to 50 mgKOH / g. When the hydroxyl value of the polyurethane diol (A) is 10 mg KOH / g or more, most of the added curing agent component reacts with the hydroxyl group contained in the main component, and preferably 50 mg KOH / g or less. This is preferable because the reaction proceeds more.

  The polyurethane diol (A) is a main component of the adhesive, and is improved by adding aliphatic polycarbonate diol (C), 1,6 hexanediol (D) and isophorone diisocyanate (E) in order to improve adhesion and weather resistance. It can be obtained by reaction. Hereinafter, the aliphatic polycarbonate diol (C), 1,6 hexanediol (D), and isophorone diisocyanate (E), which are components of the polyurethane diol (A), will be described.

  The aliphatic polycarbonate diol (C) is a constituent component of the polyurethane diol (A) that can react with the following isophorone diisocyanate (E). The aliphatic polycarbonate diol (C) has a carbonate structure as a repeating unit and has hydroxyl groups at both ends. The hydroxyl groups at both ends can be cured with an isocyanate group.

  The aliphatic polycarbonate diol (C) can be produced by a method of producing using alkylene carbonate and diol as raw materials, a method of producing using dialkyl carbonate or diaryl carbonate and diol, and the like. The aliphatic polycarbonate diol (C) can be produced by appropriately selecting the above production method according to the performance required for the main component.

  Examples of the alkylene carbonate that can be used for the production of the aliphatic polycarbonate diol (C) include ethylene carbonate, trimethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, and 1,2-pentylene. Examples include ren carbonate. Examples of the dialkyl carbonate include dimethyl carbonate, diethyl carbonate, and dipropyl carbonate. Examples of the diaryl carbonate include diphenyl carbonate.

  Diols having no side chain such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, Diols having side chains such as 2-methyl-1,8-octanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, and cyclic diols such as 1,3-cyclohexanediol and 1,4-cyclohexanediol Can be mentioned. One type of diol may be used, or a copolymerized polycarbonate diol using two or more types of diol as raw materials may be used.

  The number average molecular weight of the aliphatic polycarbonate diol (C) is preferably 1000 to 2000. When it is 1000 or more, it is preferable because a curing reaction with diisocyanate easily occurs, and when it is 2000 or less, solubility in a solvent as an adhesive component is improved. In the production of the polycarbonate diol (C), the reactivity of the monomer is high and the molecular weight is easily increased. Therefore, in order to obtain a polycarbonate diol having a predetermined number average molecular weight, it is necessary to control the reaction rate and the like.

  Commercially available aliphatic polycarbonate diol (C) can also be used. In order to obtain an adhesive having excellent durability, weather resistance, heat resistance, and hydrolysis resistance, for example, an aliphatic polycarbonate diol having a number average molecular weight of 1000 (manufactured by Asahi Kasei Chemicals, trade name “Duranol T5651”), number average molecular weight 2000 aliphatic polycarbonate diol (manufactured by Asahi Kasei Chemicals Corporation, trade name “Duranol T5662” can be preferably used.

  1,6 hexanediol (D) is an aliphatic diol and can react with the following isophorone diisocyanate (E) to form a polyurethane diol (A). 1,6 hexanediol (D) is liquid at room temperature and can be dissolved in a solvent as an adhesive component.

  Isophorone diisocyanate (E) is a component of the polyurethane diol (A) and is an alicyclic polyisocyanate. Isophorone diisocyanate (E) reacts with the hydroxyl groups of the aliphatic polycarbonate diol (C) and 1,6 hexanediol (D) to form a polyurethane diol (A) as a main component.

  The polyurethane diol, which is the main component, is reacted by dissolving the aliphatic polycarbonate diol (C), 1,6 hexanediol (D) and isophorone diisocyanate (E) described above in a solvent, mixing and heating to reflux. A solution of (A) can be obtained. In the above reaction, the hydroxyl groups at both ends of each of the aliphatic polycarbonate diol (C) and 1,6 hexanediol (D) react with the isocyanate group of isophorone diisocyanate (E) to form a urethane bond and cure. To do.

  The blending amount of 1,6 hexanediol (D) in the reaction system for producing the main component polyurethane diol (A) is 5 to 15 parts by mass with respect to 100 parts by mass of the aliphatic polycarbonate diol (C). The amount is preferably 2 parts by mass or more and 8 parts by mass or less. When the amount of 1,6 hexanediol (D) is 5 parts by mass or more, a durable adhesive component can be obtained, and when it is 15 parts by mass or less, the solubility in a solvent is improved. Therefore, it is preferable.

  In addition, as a solvent that can be used when the aliphatic polycarbonate diol (C), 1,6 hexanediol (D), and isophorone diisocyanate (E) are reacted, these compounds can be dissolved, The solvent is not particularly limited as long as it does not react with the solvent, and examples thereof include carboxylic acid ester solvents such as ethyl acetate from the viewpoints of compatibility and processability during lamination.

  The aliphatic polycarbonate diol (B), which is the main component, reacts with the curing agent component having an isocyanate group. As the aliphatic polycarbonate diol (B), the same aliphatic polycarbonate diol (C) as used in the production of the polyurethane diol (A) can be used.

  The main component is a mixture of the polyurethane diol (A) and the aliphatic polycarbonate diol (B) described above. The mass ratio of the polyurethane diol (A) and the aliphatic polycarbonate diol (B) in the mixture is preferably 10 to 20 parts by mass of the aliphatic polycarbonate diol (B) with respect to 100 parts by mass of the polyurethane diol (A). . When the amount of the aliphatic polycarbonate diol (B) is 10 parts by mass or more, an appropriate adhesion can be obtained, and when it is 20 parts by mass or less, a reaction with the curing agent easily occurs.

  In addition to the main component polyurethane diol (A) and aliphatic polycarbonate diol (B), the main agent includes a tackifier, a stabilizer, a filler, a plasticizer, and a softening point improver as necessary. Further, a catalyst or the like can be mixed as an additive. Examples of tackifiers include rosin resins and terpene resins. Examples of the stabilizer include an antioxidant and an ultraviolet ray inhibitor. Examples of the filler include inorganic fillers.

[Curing agent]
As the curing agent for the adhesive, for example, an adhesive mainly containing a polyisocyanate compound can be used. The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, and the isocyanate group reacts with a hydroxyl group in the polyurethane diol compound as the main agent to crosslink the polyurethane diol compound. Such a polyisocyanate compound is not particularly limited as long as it can crosslink the main polyurethane diol compound. For example, polyurethane diisocyanate, hexamethylene diisocyanate (hereinafter, “HDI”), Examples include hexamethylene diisocyanate-based bifunctional polyurethane diisocyanate (G), isocyanurate-modified isophorone diisocyanate (F) (hereinafter, “nurate-modified IPDI”), and the like. Among these polyisocyanate compounds, a mixture of HDI and nurate-modified IPDI is preferable from the viewpoint of improving the reactivity with respect to hydroxyl groups. When the curing agent is a mixture of HDI and nurate-modified IPDI, it is preferable to use HDI and nurate-modified IPDI in the range of 70:30 to 50:50 (mass ratio).

[solvent]
It is preferable to add a solvent component to the main agent and the curing agent, which are the adhesive components, in order to obtain good coating properties and handling suitability. Examples of such a solvent component include, but are not limited to, carboxylic acid esters such as ethyl acetate, methyl acetate, and methyl propionate. As described above, the adhesive is configured as a two-component agent consisting of a main agent and a curing agent, but the solvent component used in the main agent and the solvent component used in the curing agent are each independently selected and may be the same. May be different.

[Additives such as silane coupling agents]
In addition to the main agent, curing agent and solvent, the laminating adhesive component can contain silane coupling agents, tackifiers, stabilizers, fillers, plasticizers, softening point improvers, catalysts, etc. as necessary. Can be mixed. Examples of the silane coupling agent include silane monomers such as methyltrimethoxysilane and methyltriethoxysilane, vinylsilanes such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-methacryloxypropylethoxysilane, and 3-methacryloxypropylmethoxy. Mention may be made of epoxysilanes such as methacrylic silanes such as silane, 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Examples of tackifiers include rosin resins and terpene resins. Examples of the stabilizer include an antioxidant and an ultraviolet ray inhibitor. Examples of the filler include inorganic fillers.

  In addition, it is preferable that the addition amount of the said silane coupling agent is 1 to 3 mass% silane coupling agent with respect to a total of 100 mass parts of the adhesive main agent and a hardening | curing agent, Addition of a silane coupling agent When the amount is 1% by mass or more, the adhesion is good, and when it is 3% by mass or less, the durability is excellent.

[Combination of main agent and curing agent]
The adhesive component is mainly composed of a main agent and a curing agent, but the mixing ratio of the main agent and the curing agent is such that the ratio of (isocyanate group derived from polyisocyanate compound) / (hydroxyl group derived from polyurethane diol compound) is 1. It is preferably in the range of 0.0 to 3.5, and more preferably in the range of 1.2 to 3.0. It is preferable that the blending ratio of the polyurethane diol compound as the main component and the polyisocyanate compound as the curing agent component is in the above range because an adhesive capable of firmly bonding the respective substrates can be obtained.

(Formation of adhesive layer)
In this embodiment, a two-component type adhesive composed of a main agent and a curing agent is applied to the surface of the base material to be joined, and then the solvent component evaporates from the applied adhesive to adhere to the surface of the base material. An agent layer can be formed. This adhesive film is cured in a state of being bonded to the surface of the substrate to be bonded, and becomes an adhesive layer. Although the method in particular of apply | coating an adhesive agent on the surface of a base material is not restrict | limited, The gravure coater method, the roll coater method, the brushing method etc. can be mentioned. The coating amount is desirably 2.0 g / m ² or more and 10.0 g / m ² or less (dry state).

  The thickness of the adhesive layer is preferably 2.0 μm or more and 10.0 μm or less, and more preferably 3.0 μm or more and 7.0 μm or less. By adjusting the thickness of the adhesive layer to 2.0 μm or more and 10.0 μm or less, adhesion between layers, durability, and printability can be improved.

  Inside the adhesive layer, the hydroxyl group component contained in the polyurethane diol, which is the main component of the adhesive, reacts with the isocyanate group contained in the polyisocyanate, which is the curing agent component, to cause a curing reaction to form a urethane bond. To do. By this reaction, the main agent component is cross-linked by the curing agent component and becomes high molecular weight. When the polyurethane diol which is the main component is sufficiently crosslinked, the adhesive film is cured and becomes an adhesive layer.

  The adhesive contains polyurethane diol (A) and polycarbonate diol (B) as the main resin. Therefore, the adhesive layer formed by the adhesive contains a polycarbonate resin and a polyurethane resin. By including the polycarbonate resin and the polyurethane resin in the adhesive layer, the adhesiveness of the adhesive layer and the weather resistance of the back protective sheet on which the adhesive layer is laminated can be improved.

  The adhesive layer used in this embodiment is characterized in that the minimum value of the loss elastic modulus in the range of 110 ° C. to 150 ° C. measured by the DMA evaluation method is more than 100 Pa. Thermal lamination is usually performed at a temperature of about 110 ° C. to 150 ° C. Therefore, when the minimum value of loss elastic modulus in the range of 110 ° C. to 150 ° C. is 100 Pa or less, the volume of the adhesive layer during lamination is The rate of change increases. Therefore, the rate of fluctuation of the volume of the adhesive layer can be reduced by making the adhesive layer the minimum value of the loss elastic modulus in the range of 110 ° C. to 150 ° C. exceeding 100 Pa. Therefore, wrinkles can be prevented from occurring if the back protective sheet is formed by laminating an adhesive layer having a minimum loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower.

  As an adhesive layer in which the minimum value of the loss elastic modulus in the range of 110 ° C. or more and 150 ° C. or less is 100 Pa or less, for example, polyurethane produced by heating and refluxing polycarbonate diol (B) and polyester diol as urethane resin An adhesive layer containing a resin, or an adhesive layer containing a resin incorporating a molecular chain derived from an aromatic ether (for example, made of Mitak Chemical's Takelac (main agent component) and Takenate (curing agent component) And an adhesive layer formed by an adhesive). It is considered that the resin of the adhesive layer is easily melted by incorporating a molecular chain derived from polyester diol or aromatic ether into a part of the resin of the adhesive layer. Therefore, it is preferable that the resin contained in the adhesive layer used in this embodiment does not contain a molecular chain derived from polyester diol or aromatic ether.

<Aluminum foil>
The back surface protection sheet of this embodiment includes a configuration in which aluminum foil is laminated. By laminating the aluminum foil, a back protective sheet having a gas barrier property such as a high water vapor barrier property can be obtained.

  The film thickness of the aluminum foil 62 is 60 μm or less, and preferably 15 μm or more and 55 μm or less. By setting the film thickness of the aluminum foil to 15 μm or more, it is possible to prevent the occurrence of pinholes and to provide a back protective sheet with high gas barrier properties. At the same time, generation of wrinkles during thermal lamination can be suppressed. By setting the film thickness of the aluminum foil to 60 μm or less, it is possible to obtain a back surface protection sheet that is low in cost, highly suitable for processing, and has a reduced weight.

  In order to secure the adhesive force between the first resin sheet 61 and the second resin sheet 63 and the aluminum foil 62, the aluminum foil 62 is preferably subjected to an activated surface treatment. This treatment can be performed by a known method such as an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, an electrolytic acid cleaning method, or an acid activation method.

<First resin sheet>
When the back surface protection sheet 6 is used for the solar cell module 1, the first resin sheet 61 becomes a surface in contact with the back surface sealing material sheet 5 in the solar cell module 1. Therefore, it is preferable to use the 1st resin sheet 61 which was excellent in adhesiveness between the back sealing material sheets 5 in addition to electrical insulation.

  As such a resin sheet, a resin sheet such as a fluorine resin, a polyolefin resin, a polycarbonate resin, a poly (meth) acrylic resin, or a polyester resin can be used. Among these, it is preferable to use a polyethylene terephthalate resin. Polyethylene terephthalate resin has a high melting point of about 260 degrees. Therefore, generation | occurrence | production of the wrinkle of a resin sheet can be suppressed. Moreover, from the viewpoint of placing importance on the adhesiveness, for example, the main component is a modified polyphenylene ether having a particularly high adhesiveness with the back sealing material sheet 5 by adopting a layer configuration capable of blocking ultraviolet rays by other layers. The resin sheet to be used can also be used suitably.

  The film thickness of the first resin sheet layer is preferably 45 μm or more and 85 μm or less, and preferably 50 μm or more and 70 μm or less. By setting the film thickness of the first resin sheet layer to 45 μm or more, generation of wrinkles of the back surface protection sheet during thermal lamination can be suppressed. Moreover, the insulation property of the back surface protection sheet can be secured. By setting the film thickness of the first resin sheet layer to 85 μm or less, the heat dissipation of the solar cell module can be improved, and the decrease in conversion efficiency of the solar cell due to the generation of heat can be prevented.

<Second resin sheet>
When the back surface protection sheet 6 is used for the solar cell module 1, the second resin sheet 63 becomes a surface located on the surface on the back surface side of the solar cell module 1. Therefore, it is preferable to use the second resin sheet 63 having excellent weather resistance, heat resistance, light resistance, and the like.

  Such resin sheets include PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ester copolymer), PTFE (polytetrafluoroethylene), ETFE (tetrafluoroethylene / ethylene copolymer). Polymer), fluorine resins such as PVDF (polyvinylidene fluoride), cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, 1,5-cyclooctadiene, etc. Cyclic polyethylene, polypropylene, polystyrene, ethylene / propylene copolymer, ethylene / styrene copolymer, propylene / styrene copolymer, poly 1,4-cyclopentadiene, poly 1,5-hexadiene, etc. as monomers Reolefin resin, polycarbonate resin using alkylene carbonate and diol as raw materials, poly (meth) acrylic resin such as polymethyl methacrylate, polyacrylate, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PTT (polytrimethyl methacrylate) A resin sheet such as a polyester-based resin such as methylene terephthalate) is preferably exemplified. Moreover, you may use what contains a white pigment in these resin. Here, in this embodiment, since the 2nd resin sheet 63 is arrange | positioned in the outermost layer in the solar cell module 1, high weather resistance, barrier property, and hydrolysis resistance are calculated | required. Among these points of view, it is particularly preferable to use a hydrolysis-resistant polyethylene terephthalate resin. Examples of the hydrolysis-resistant polyethylene terephthalate include Shine Beam (hydrolysis-resistant polyester film) manufactured by Toyobo Co., Ltd.

  The film thickness of the second resin sheet layer is preferably 25 μm or more and 85 μm or less, and preferably 35 μm or more and 55 μm or less. By setting the film thickness of the second resin sheet layer to 25 μm or more, generation of wrinkles of the back surface protection sheet during thermal lamination can be suppressed. Moreover, the weather resistance of the back surface protection sheet can be secured. By setting the film thickness of the second resin sheet layer to 85 μm or less, the heat dissipation of the solar cell module can be improved, and a decrease in the conversion efficiency of the solar cell due to the generation of heat can be prevented.

<Production method of back surface protection sheet>
The back surface protection sheet can be manufactured, for example, by laminating and adhering a resin sheet as an outer layer of the back surface protection sheet 6 and an aluminum foil 62 as an intermediate layer by dry lamination. A conventionally known method can be used as the dry laminating method used here.

[Others]
In addition, the back surface protection sheet of this embodiment may adhere | attach a heat dissipation sheet, for the purpose of improving heat dissipation more, for example. Such a back surface protection sheet with a heat dissipation sheet is also within the scope of the present invention.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example etc.

  In order to evaluate the ease of occurrence of wrinkles, heat dissipation, weather resistance, and insulation of the back surface protection sheet for solar cells according to this embodiment, an adhesive was produced by the following method, and the adhesive was used. The used back surface protection sheet sample was prepared.

<Adhesive 1>
[Manufacture of main agent]
1. Production of polyurethane diol 100 parts by mass of an aliphatic polycarbonate diol having a number average molecular weight of 1000 (trade name “Duranol T5651” (hereinafter referred to as “PDC1000”) manufactured by Asahi Kasei Chemicals Co., Ltd.) in a flask equipped with a stirrer under a nitrogen atmosphere. 1,6-hexanediol (5 parts by mass), isophorone diisocyanate (27.5 parts by mass), and ethyl acetate (132.5 parts by mass) are added, and absorption of 2270 cm ⁻¹ isocyanate disappears in the infrared absorption spectrum. The mixture was heated to reflux until a 50% solution of polyurethane diol A-1 was obtained. The obtained resin had a hydroxyl value of 14 mg KOH / g and a number average molecular weight of about 8,000.

2. Production of Aliphatic Polycarbonate Diol An aliphatic polycarbonate diol was prepared as the aliphatic polycarbonate diol as the main component. The aliphatic polycarbonate diol is an aliphatic polycarbonate diol having a number average molecular weight of 1000 (manufactured by Asahi Kasei Chemicals Corporation, trade name “Duranol T5651”).

3. Preparation of Main Agent A main agent was prepared using polyurethane diol and aliphatic polycarbonate diol, which are the main component components produced above. The main agent was prepared by blending 15 parts by mass of aliphatic polycarbonate diol with 100 parts by mass of polyurethane diol.

[Manufacture of curing agent]
A curing agent was produced as a curing agent constituting the adhesive. In addition, as a material for the curing agent, isophorone diisocyanate nurate and hexamethylene diisocyanate bifunctional polyurethane diisocyanate ("Duranate D101" manufactured by Asahi Kasei Chemicals Corporation) were used. The blending ratio (mass) of isophorone diisocyanate nurate: hexamethylene diisocyanate bifunctional polyurethane diisocyanate was 40:60. In addition, although the said mixture ratio (mass) is a solid mass ratio which does not contain a solvent, it prepared to 50% of solid content in manufacture.

[Combination of main agent and curing agent]
An adhesive was produced using the main agent and curing agent produced above. In addition, the main agent and the curing agent were blended by dissolving the main agent and the curing agent in a solvent to make each 50 mass% (ethyl acetate solution). The main agent and the curing agent were adjusted at a mass ratio of 18: 3.7.

<Adhesive 2>
[Main agent]
1. Production of polyester diol In a nitrogen atmosphere, a flask equipped with a stirrer and a nitrogen introduction tube was charged with ethylene glycol (32.3 parts by mass), 2,2-dimethyl-1,3-propanediol (270.8 parts by mass), 1 , 6-hexanediol (122.9 parts by mass), adipic acid (228.1 parts by mass), isophthalic acid (664 parts by mass), bubbled with nitrogen at 180 ° C. to 220 ° C., and an acid value of 2 mgKOH / to 50 g, ethyl acetate (860 parts by mass) was added to obtain a 50% solution of polyester diol H. The obtained resin had a hydroxyl value of 32 mgKOH / g and a number average molecular weight of about 3500.

2. Production of polyurethane diol 100 parts by mass of an aliphatic polycarbonate diol having a number average molecular weight of 1000 (manufactured by Asahi Kasei Chemicals Co., Ltd., trade names “Duranol T5651” and below, abbreviated as “PDC1000”) in a flask equipped with a stirrer under a nitrogen atmosphere, Polyesterdiol H (50 parts by mass), 1,6-hexanediol (2 parts by mass), isophorone diisocyanate (23.8 parts by mass), ethyl acetate (175.8 parts by mass) were added, and the infrared absorption spectrum was 2270 cm. ^The mixture was heated to reflux until absorption of the isocyanate of ^-1 disappeared to obtain a 50% solution of polyurethane diol. The obtained resin had a hydroxyl value of 14 mg KOH / g and a number average molecular weight of about 8,000.

3. Preparation of Main Agent 100 parts by mass of the above polyurethane diol and 15 parts by mass of aliphatic polycarbonate diol (PDC1000) were mixed to prepare a main agent.

[Manufacture of curing agent]
The adhesive 1 was produced in the same manner as the curing agent.

[Combination of main agent and curing agent]
An adhesive was produced using the main agent and curing agent produced above. In addition, the main agent and the curing agent were blended by dissolving the main agent and the curing agent in a solvent to make each 50 mass% (ethyl acetate solution). The main agent and the curing agent were adjusted at a mass ratio of 18: 3.4.

<Adhesive 3>
As the adhesive 3, a two-pack type adhesive manufactured by Mitsui Chemicals (main agent: Takelac (A-969V) curing agent: Takenate (A-5) aromatic ether adhesive) was used to produce an adhesive. In addition, the main agent and the curing agent were blended by dissolving the main agent and the curing agent in a solvent to make each 50 mass% (ethyl acetate solution). The main agent and the curing agent were adjusted at a mass ratio of 3: 1.

[Create sample]
Polyethylene terephthalate film (Lumirror S10 manufactured by Toray Industries, Inc.) as the resin film constituting the first resin sheet layer, “Nippaku #” (manufactured by Nihon Foil Co., Ltd.) as the aluminum foil constituting the aluminum foil layer, and the second resin sheet layer A polyethylene terephthalate film (Lumirror S10 manufactured by Toray Industries, Inc.) was used as the resin film to be constructed. As an adhesive which forms a 1st adhesive bond layer and a 2nd adhesive bond layer, using any one of the adhesive agents 1-the adhesive agent 3, respectively, application amount 2.0-10.0 g / m < ² > (dry state) ) To form an adhesive layer, and the above-described film members are first resin sheet layer / first adhesive layer / aluminum foil layer / second adhesive layer / second resin sheet by a conventionally known dry laminating method. It laminated | stacked so that it might become a layer, and the sample of the back surface protection sheet of an Example and a comparative example was obtained.

(Wrinkle generation test)
A pseudo module was created using the samples of the back surface protective sheets of Examples , Comparative Examples, and Reference Examples . The pseudo module is made of glass as a transparent front substrate, ethylene-vinyl acetate alcohol copolymer resin (EVA) 450 μm as a sealing material layer , and samples according to Examples , Comparative Examples, and Reference Examples as a back protection sheet. The front substrate / front sealing material layer / back surface sealing material layer / back surface protection sheet were laminated in this order, and were prepared by vacuum lamination, and the presence or absence of wrinkles was confirmed. In addition, the back surface protection sheet was laminated | stacked in the aspect as described also in the paragraph [0022], ie, the aspect in which the 1st resin sheet directly contacts with the back surface sealing material layer. (Vacuum lamination conditions: temperature 150 ° C., vacuum time 5 minutes, press time 9 minutes) The results are shown in Table 1, Table 2 and Table 5 below as “wrinkles”.

[Evaluation criteria]
A: Wrinkles did not occur.
◯: Although unevenness was observed on the sheet surface, no wrinkles were generated.
X: Wrinkles occurred.

(Heat dissipation test)
A pseudo module was created using the samples of the back surface protective sheets of Examples , Comparative Examples, and Reference Examples . About the pseudo module, glass as a transparent front substrate, ethylene-vinyl acetate alcohol copolymer resin (EVA) 450 μm as a sealing material layer , and samples according to Examples , Comparative Examples, and Reference Examples as a back protection sheet are transparent. The front substrate / front sealing material layer / cell / back surface sealing material layer / back surface protective sheet were laminated in this order, and were prepared by vacuum lamination. At this time, a thermocouple was inserted between the cell and the back sealing material layer to create a pseudo module capable of measuring the cell temperature. (Vacuum laminating conditions: temperature 150 ° C., vacuum time 5 minutes, press time 9 minutes), this pseudo module was placed at a south facing angle of 45 ° for 24 hours, and the cell temperature was measured. The maximum temperature of Example 1 was 43.6 ° C. The maximum temperatures of other examples , comparative examples, and reference examples were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1 below as “heat dissipation”.

[Evaluation criteria]
It is a value compared with the maximum temperature (43.6 ° C.) of Example 1.
◎: -0.2 ° C or higher ○: -0.2 ° C or higher + 0.2 ° C or lower △: + 0.2 ° C or higher + 0.5 ° C or lower ×: + 0.5 ° C or higher

(Weather resistance test)
About the back surface protection sheet of an Example , a comparative example, and a reference example , the MW (metal weather) test as demonstrated in detail below was done, and the durable adhesiveness after a weather resistance test was evaluated.

About the back surface protection sheet of an Example , a comparative example, and a reference example , a MW (metal weather) test is performed on condition of the following, About each back surface protection sheet after the same test, the adhesiveness test according to ASTM D3359 and JIS5400 is performed. The durability was evaluated based on the following evaluation criteria, and the results are shown in Table 1 below as “weather resistance”.

Metal halide lamp type testing machine JTM G 01 2000 Japan Testing Machine Industry Association Standard JTM STANDARD Metalhalide Lamp type appratus
Device name: Daipla Metal Weather (Daipla Wintes Co., Ltd.)
Model: KU-R5CI-A
Light source lamp: MW-60W
Filter: KF-1 (irradiation range 295 nm to 780 nm)
Illuminance: 60 ± 5 mW / cm2 (Ushio Electric Co., Ltd. illuminance meter used)
Test conditions: Lite (irradiation) 63 ° C. 50% RH 20 hours, Dew (condensation) 30 ° C. 98% RH 4 hours, Rest (rest): 30 ° C., 98% RH, 0.01 hour, 10 s shower before and after Dew 250 hours test conducted as one cycle.
In the shower, pure water having a conductivity of 2 μS / cm or less was used at 25 ° C.

[Evaluation criteria]
A: Coating film peeling rate 10%
○: Coating film peeling rate of 10% or more and less than 30% Δ: Coating film peeling rate of 30% or more and less than 50% ×: Coating film peeling rate of less than 50%

(Insulation test)
Insulating properties were evaluated for the back surface protective sheets of Examples , Comparative Examples, and Reference Examples . The test about insulation was performed by measuring the partial discharge voltage of each sample for evaluation according to IEC61730. As a measuring instrument, a partial discharge voltage measuring device (KPD-2050 manufactured by Kikusui Co., Ltd.) was used. The measurement was performed in oil, the partial discharge voltage was measured, and the system voltage was estimated from there. The results are shown in Table 1 below as “insulating”.

[Evaluation criteria]
◎: Resistance value 1000Ω or more ○: Resistance value 610Ω or more and less than 1000Ω △: Resistance value 600Ω or more and less than 610Ω ×: Resistance value less than 600Ω

（実施例、比較例、及び参考例のサンプルはいずれもアルミ箔層厚み：２０μｍ、第一接着剤層厚み：３μｍ、第二接着剤層厚み：３μｍである。また、接着剤はいずれのサンプルも接着剤１を用いた。）

(All of the samples of Examples , Comparative Examples, and Reference Examples are aluminum foil layer thickness: 20 μm, first adhesive layer thickness: 3 μm, second adhesive layer thickness: 3 μm. In addition, the adhesive is any sample. Also used adhesive 1.)

  From Table 1, the film thickness of the first resin sheet layer is 45 μm or more and 85 μm or less, and the back surface protection sheet in which the film thickness of the second resin sheet layer is 35 μm or more and 70 μm or less is “wrinkle”, “heat dissipation”, “ It turns out that it is a back surface protection sheet excellent in "weather resistance" and "insulation".

（実施例１、５、６及び比較例６のサンプルはいずれも第一樹脂シート厚み：５０μｍ、第二樹脂シート厚み：５０μｍ、第一接着剤層厚み：３μｍ、第二接着剤層厚み：３μｍである。また、接着剤はいずれのサンプルも接着剤１を用いた。）

(All of the samples of Examples 1, 5, 6 and Comparative Example 6 have a first resin sheet thickness: 50 μm, a second resin sheet thickness: 50 μm, a first adhesive layer thickness: 3 μm, and a second adhesive layer thickness: 3 μm. In addition, the adhesive used the adhesive 1 in any sample.)

  From Table 2, it can be seen that the back surface protective sheet having a film thickness of the aluminum foil layer of 20 μm or more and 60 μm or less is an excellent back surface protection sheet by “wrinkles”.

（実施例１、実施例７〜１２のサンプルはいずれも第一樹脂シート厚み：５０μｍ、第二樹脂シート厚み：５０μｍ、アルミ箔層厚み：２０μｍである。また、接着剤はいずれのサンプルも接着剤１を用いた。）

(The samples of Example 1 and Examples 7 to 12 all have a first resin sheet thickness of 50 μm, a second resin sheet thickness of 50 μm, and an aluminum foil layer thickness of 20 μm. Also, the adhesive is bonded to any sample. Agent 1 was used.)

(Printability test)
The adhesive 1 was evaluated for printability. Evaluation was performed by applying an adhesive to a polyethylene terephthalate film (T60 manufactured by Toray Industries Inc.) with a thickness of 50 μm so that the thickness of the adhesive layer is as shown in Table 4. “Drying time” until “no longer” or “no tackiness” was measured, and the measured time was evaluated by the following evaluation criteria. The evaluation results are shown in Table 4 below as “printability”.

[Evaluation criteria]
○: Drying time 20 seconds or more Δ: Drying time 20 seconds or more and less than 30 seconds X: Drying time less than 30 seconds

  From Table 3 and Table 4, if the adhesive layer film thickness is 2.0 μm or more and 10.0 μm or less, wrinkles do not occur and a back protective sheet having printability can be obtained. Moreover, it turns out that it can be set as the back surface protection sheet excellent in printability by setting it as 3.0 micrometers or more and 7.0 micrometers or less.

(Loss elastic modulus evaluation)
The dynamic viscoelasticity of the adhesive layer of the back surface protection sheet of Example 1, Comparative Example 7 and Comparative Example 8 was measured. Specifically, the loss elastic modulus was measured by raising the temperature from −20 ° C. at a measurement frequency of 1 Hz and a heating rate of 3 ° C./min. The loss elastic modulus of the adhesive layer was evaluated under the following evaluation criteria.
[Evaluation criteria]
A: The minimum value of the loss elastic modulus at 110 ° C. or more and 150 ° C. or less was more than 100 Pa.
X: The minimum value of the loss elastic modulus at 110 ° C. or more and 150 ° C. or less was 100 Pa or less.

  In the adhesive layer of Example 1, the minimum value of the loss elastic modulus was over 100 Pa even in the range of 110 ° C. or higher and 150 ° C. or lower, and no melting of the adhesive layer was observed. In the adhesive layers of Comparative Examples 7 and 8, the minimum loss modulus was 100 Pa or less even in the range of 110 ° C. or higher and 150 ° C. or lower, and it was confirmed that the adhesive layer was melted. From the above, it was confirmed that the back surface protective sheet of Example 1 had a minimum value of loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower measured by the DMA evaluation method of more than 100 Pa.

（実施例１、比較例７及び比較例８のサンプルはいずれも第一樹脂シート厚み：５０μｍ、第二樹脂シート厚み：５０μｍ、アルミ箔層厚み：２０μｍ、第一接着剤層厚み：３．０μｍ、第二接着剤層厚み：３．０μｍである。）

(All the samples of Example 1, Comparative Example 7 and Comparative Example 8 are the first resin sheet thickness: 50 μm, the second resin sheet thickness: 50 μm, the aluminum foil layer thickness: 20 μm, the first adhesive layer thickness: 3.0 μm. The second adhesive layer thickness is 3.0 μm.)

(TMA test)
The linear expansion coefficient of the back surface protection sheet of Example 1 and Comparative Example 7 was measured in both the TD direction and the MD direction by thermomechanical analysis (TMA). The measurement results are shown in FIG. In FIG. 3, as a result of the TMA test, the expansion rate of the back surface protection sheet sample before the TMA test was set to 0% (indicated as “test start” in FIG. 3), and the temperature was increased from room temperature to 200 ° C. and from 200 ° C. to room temperature. The relationship between the temperature when the temperature is lowered until the expansion rate of the sample is shown. In addition, “end of test” shown in FIG. 3 shows the expansion coefficient of the sample when the back surface protection sheet sample is heated to 200 ° C. and then cooled to room temperature.
Measurement temperature: room temperature → 200 ° C. → room temperature heating rate: 10 ° C./min. Temperature decreasing rate: 10 ° C./min.
Initial load: 6g
Sample size: 5mm x 20mm

  From FIG. 3, compared with Comparative Example 7, Example 1 has a smaller volume shrinkage particularly when the temperature is lowered from 200 ° C. to room temperature (denoted as the end of the test in FIG. 3). Also from this, the back surface protective sheet of Example 1 having the adhesive layer having the minimum loss elastic modulus in the range of 110 ° C. or higher and 150 ° C. or lower suppresses generation of wrinkles during thermal lamination. It can be seen that this is an excellent back surface protection sheet.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back sealing material layer 6 Back surface protection sheet 61 First resin sheet 62 Aluminum foil 63 Second resin sheet 64a First adhesive layer 64b Second Adhesive layer

Claims (3)

When integrated as a solar cell module, the first resin sheet layer that is assumed to be a layer that is laminated in a form that comes into direct contact with the back sealing material layer and the layer disposed on the outermost layer side of the solar cell module It is a back surface protection sheet for a solar cell module including a configuration in which an aluminum foil layer is laminated via an adhesive layer between second resin sheet layers that are supposed to be,
The film thickness of the first resin sheet layer is 45 μm or more and 85 μm or less,
The film thickness of the second resin sheet layer is 35 μm or more and 85 μm or less,
The film thickness of the aluminum foil layer is 15 μm or more and 60 μm or less,
The adhesive layer includes a polyurethane resin and a polycarbonate diol resin, and the polyurethane resin is 5 parts by mass of 1,6 hexanediol with respect to 100 parts by mass of an aliphatic polycarbonate diol having a number average molecular weight of 1000 to 2000. A polyurethane diol having a number average molecular weight of 7000 to 13000 obtained by reacting 15 parts by mass or less with isophorone diisocyanate, and having a loss in the range of 110 ° C. to 150 ° C. measured by the following DMA evaluation method The minimum value of the elastic modulus is over 100 Pa,
Back protection sheet.
DMA evaluation method: Measurement frequency: 1 Hz, temperature increase rate from −20 ° C. at a temperature increase rate of 3 ° C./min, and loss elastic modulus of 110 ° C. to 150 ° C. is measured.   The back protective sheet according to claim 1, wherein the first resin sheet layer and the second resin sheet layer are polyethylene terephthalate. The back surface protection sheet according to claim 1 or 2 is arranged in the outermost layer,
The back surface protective sheet is laminated such that the first resin sheet layer is in direct contact with the back surface sealing material layer, and the second resin sheet layer is disposed on the outermost layer side of the solar cell module. ,
Solar cell module.

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