JP2013251427A - Film for solar cell module back-surface sealing sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing sheet for a solar cell excellent in adhesive strength against filling, storage stability, productivity and also environmental resistance, and a solar cell module using the same.SOLUTION: A film for a solar cell module back-surface sealing sheet having a resin layer containing an acrylic polymer and at least one kind of block isocyanate compounds on a single-side of a base film is characterized in that when the peak intensity of 1440 cmto 1470 cmin the absorption spectrum of a surface of the resin layer at 25°C as obtained by the attenuated total reflection method (ATR method) is defined as Pa and the peak intensity of 1550 cmto 1570 cmis defined as Pb, the ratio value of Pb to Pa (Pb/Pa) is 0.01 to 0.1.

Description

  The present invention relates to a film for a solar cell module back surface sealing sheet that can withstand use in a harsh outdoor environment for a long period of time and a film for a solar cell module back surface sealing sheet excellent in environmental resistance and a solar cell module using the same. .

  In recent years, the depletion of fossil fuels such as oil and coal has been threatened, and development to secure alternative energy obtained from these fossil fuels is urgently required. For this reason, various methods such as nuclear power generation, hydroelectric power generation, wind power generation, and solar power generation have been studied and are actually used.

  Solar power generation, which can directly convert solar energy into electrical energy, is being put into practical use as a new semi-permanent and non-polluting energy source. It is very promising as a remarkable and clean energy source.

  A solar cell used for photovoltaic power generation constitutes the heart of a photovoltaic power generation system that directly converts sunlight energy into electrical energy, and is made of a semiconductor represented by silicon or the like. As its structure, solar cell elements are wired in series and in parallel, and various packaging is performed to protect the elements over a long period of about 20 years, and they are unitized. The unit incorporated in this package is called a solar cell module, and generally has a structure in which the surface exposed to sunlight is covered with glass, the gap is filled with a filler made of thermoplastic resin, and the back surface is protected with a sealing sheet. Yes. As a filler made of a thermoplastic resin, ethylene-vinyl acetate copolymer resin (hereinafter referred to as EVA resin) is often used because of its high transparency and excellent moisture resistance. On the other hand, the backside sealing sheet has mechanical strength, weather resistance, heat resistance, water resistance, chemical resistance, light reflectivity, water vapor barrier properties, thermal adhesiveness with fillers typified by EVA resin, and design properties. Characteristics such as adhesive strength with the outermost terminal box mounting silicone resin are required.

  As a film for the backside sealing sheet used conventionally, a white polyvinyl fluoride film (DuPont Co., Ltd., trade name: “Tedlar” (registered trademark)) can be exemplified, and a polyester film is sandwiched between the films. A back surface sealing material having a laminated structure is widely used in the application. Moreover, the structure which laminated | stacked the polyester-type film excellent in the weather resistance and gas barrier property can also be illustrated (patent document 1). In general, the adhesion between a polyester film typified by polyethylene terephthalate resin and the ethylene-vinyl acetate copolymer resin most widely used as a sealing resin is not so high. Therefore, in order to improve the adhesion with the ethylene-vinyl acetate copolymer filler layer as a measure for improving the adhesive strength, a thermal adhesive layer (hot melt adhesive layer) of styrene / olefin copolymer resin is provided. There have been proposed those provided with an easy-adhesion coating layer containing acrylic resin or epoxy resin as constituents (Patent Documents 2 and 3).

JP 2002-026354 A (paragraphs [0008] to [0010]) Japanese Unexamined Patent Publication No. 2003-060218 (paragraphs [0008] to [0010]) JP 2006-320991 A (paragraphs [0021] to [0024])

  However, in order to obtain a good adhesive strength with a hot-melt thermal adhesive layer, a thickness of about 3 μm is required. Therefore, since sufficient drying is required, the coating speed cannot be increased. In addition, since the surface of the resin layer formed of a hot-melt resin is relatively sticky, there is a problem that the coated film roll is pseudo-adhered (blocked) between the layers in summer. In addition, when an easy-adhesion coat layer comprising acrylic resin or epoxy resin as a constituent component was provided, even if the initial adhesion to the filler layer was good, it was exposed to environmental stress such as heat, humidity, and ultraviolet rays. In some cases, the interfacial adhesive force between the easy-adhesion coat layer and the filler layer is reduced, and in extreme cases, peeling may occur between the layers. Furthermore, since the solar cell module back surface sealing sheet is exposed to light transmitted between the silicon cells, the solar cell module back surface sealing sheet may be lightly deteriorated, resulting in problems such as yellowing.

  In the solar cell module back surface sealing sheet having a configuration in which the polyester film is sandwiched between the polyvinyl fluoride films, since the adhesive strength and the weather resistance with the sealing material layer are excellent, there is no such problem, but it is expensive. Therefore, in recent years, the solar cell module and the solar cell module constituent members that have been remarkably advanced are also obstacles.

  An object of the present invention is to provide sufficient adhesive strength with an ethylene-vinyl acetate copolymer-based filler layer required as a film for a solar cell module backside sealing sheet in view of the above-described problems of the prior art, and preservation of a film roll. It is to provide a film for a solar cell module back surface sealing sheet excellent in stability, productivity, and weather resistance against light irradiation from the light receiving surface side of the solar cell module.

In order to solve this problem, the present invention employs the following configuration. That is, a film for solar cell module backside sealing sheet having a resin layer containing an acrylic polymer and at least one type of blocked isocyanate compound on one side of a base film,
Peak intensity of ^{1440cm -1 ~1470cm} -1 of the absorption spectrum of the surface of the resin layer at 25 ° C. obtained by attenuated total reflection method (ATR method) as the ^Pa, and Pb the peak intensity of 1550cm ^-1 ~1570cm -1 The film for solar cell module backside sealing sheets, wherein the value of the ratio of Pb to Pa (Pb / Pa) is 0.01 to 0.1.

  Moreover, it is the manufacturing method of the solar cell module characterized by adhere | attaching the surface of the said resin layer side of the said film for solar cell module backside sealing sheets, and the layer of a solar cell module cell filler.

  According to the present invention, the back surface of a solar cell module having an easy-adhesive resin layer excellent in adhesive strength against fillers, storage stability, productivity and weather resistance that can withstand use in harsh outdoor environments over a long period of time. A film for a sealing sheet is obtained.

  Moreover, if the film for solar cell module back surface sealing sheets of this invention is used, the solar cell module excellent in the adhesive force with a filler layer and a weather resistance will be obtained.

[Film for solar cell module back side sealing sheet]
The film for solar cell module backside sealing sheet of the present invention is a film for solar cell module backside sealing sheet having a resin layer containing an acrylic polymer and at least one type of blocked isocyanate compound on one side of a base film. ,
Peak intensity of ^{1440cm -1 ~1470cm} -1 of the absorption spectrum of the surface of the resin layer at 25 ° C. obtained by attenuated total reflection method (ATR method) as the ^Pa, and Pb the peak intensity of 1550cm ^-1 ~1570cm -1 The ratio of Pb to Pa (Pb / Pa) is 0.01 to 0.1. Peak of ^{1440cm -1 ~1470cm} -1 of the absorption spectrum of the surface of the resin layer at 25 ° C. obtained by ATR method is peak attributed to C-H deformation vibration of the acrylic polymer. ^The peak of 1550cm ^-1 ~1570cm -1 is assigned to a peak derived from the protection (blocking) groups of the block isocyanate compound. That is, the amount of the blocked isocyanate compound relative to the acrylic polymer is represented by the ratio of the peak intensity Pb to the peak intensity Pa, and the peak intensity ratio Pb / Pa corresponds to the amount ratio of the blocked isocyanate compound to the acrylic polymer. Value. The peak intensity ratio Pb / Pa has been found to be a preferable range in order for the range of 0.01 to 0.1 to exhibit good adhesive strength with the sealing material. When Pb / Pa is smaller than 0.01, the adhesive force is insufficient because there is little formation of a crosslinked structure with the sealing material layer due to the blocked isocyanate compound. On the other hand, when Pb / Pa is greater than 0.1, the resin layer becomes a hard film because many cross-linking reactions due to the blocked isocyanate compound occur with the acrylic polymer, and the toughness and adhesion to the base material are increased. Power is reduced.

[Base film]
Various resin films can be used as the base film used in the film for solar cell module backside sealing sheet of the present invention. Specific examples include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), resin films such as polycarbonate, polymethyl methacrylate, polyacrylate, polypropylene, and polyethylene, and resin films obtained by mixing these resins. . Among them, a polyester resin film is preferable because it is excellent in strength, dimensional stability, and thermal stability, and a polyester resin film such as PET or PEN is particularly preferable because it is inexpensive. The polyester resin may be a copolymer. Examples of the copolymer component include diol components such as propylene glycol, diethylene glycol, neopentyl glycol, and cyclohexanedimethanol, isophthalic acid, adipic acid, azelaic acid, and sebacic acid. And the dicarboxylic acid component of the ester-forming derivative thereof.

  It is preferable that the base film used for the film for solar cell module backside sealing sheets of this invention is a resin film excellent in hydrolysis resistance, ie, a hydrolysis resistance film. This is because of the following points: When used as a solar cell module, it is used in an environment that is directly exposed to the outside air, and in this connection, long-term durability of the adhesive force with the filler layer It is important to maintain the interlayer adhesive force between the acrylic resin layer and the base film because it is necessary to maintain the adhesive strength. Because. Usually, a polyester resin film is formed using a so-called polymer obtained by condensation polymerization of monomers as a raw material, and contains about 1.5 to 2% by mass of an oligomer positioned between the monomer and the polymer. A typical oligomer is a cyclic trimer, and a film containing a large amount of it causes a decrease in mechanical strength, cracks due to the progress of hydrolysis due to rainwater, material destruction, etc. in long-term exposure such as outdoors. . On the other hand, a hydrolysis resistant film is a polyester resin film formed from a polyester resin having a cyclic trimer content of 1.0% by mass or less obtained by polymerization by a solid phase polymerization method. In addition, by forming a film using such raw materials, it is possible to suppress hydrolysis under high temperature and high humidity, and a film having excellent heat resistance and weather resistance can be obtained. The measurement of the cyclic trimer content can be obtained, for example, by measuring by liquid chromatography using a solution obtained by dissolving 100 mg of a polymer in 2 ml of orthochlorophenol, and is usually contained with respect to the mass of the polyester resin. It is displayed as a percentage (mass%).

  In addition, the resin film constituting the film for the back surface sealing sheet of the solar cell module may include, for example, an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, a filler, and a coloring, as necessary. Resin films and the like in which additives such as pigments are added within a range not impairing the effects of the present invention can also be used. Specifically, a pigment is kneaded into a polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), a resin such as polycarbonate, polymethyl methacrylate, polyacrylate, polypropylene, or polyethylene, or a resin obtained by mixing these resins. The film which made the resin raw material into a film is mentioned. Examples of the color pigment include a white pigment for the purpose of whitening and a black pigment for the purpose of blackening.

Since the film for solar cell module backside sealing sheet of the present invention is used by adhering to the cell filler layer, when the solar cell module is viewed from the light receiving surface side, the appearance from the gap between the solar cell and the solar cell. Is seen. Therefore, it may be required to be a white film from the viewpoint of light reflectivity, or may be required to be a black film from the viewpoint of design. In response to these requirements, there are a design in which a colored film is a base film and a design in which an acrylic resin layer is colored.
The white film is used for the purpose of assisting energy conversion in the semiconductor element by reflecting the light incident on the back sheet, and is preferably arranged in a layer close to the cell. A white film preferably used as a base film is used for reflecting sunlight to improve power generation efficiency. The white film is preferably a film having a reflectance of a wavelength λ = 550 nm of 30% or more, more preferably a film having a reflectance of 40% or more, further preferably a film having a reflectance of 50% or more. is there.
The black film is used because, when a solar cell module is formed, the appearance from the light receiving surface side is harmonized with the color tone of the silicon cells and the black color tone of the gaps between the silicon cells, resulting in a beautiful panel appearance.
Among colored films containing a color pigment, a polyester resin film is preferable because of its excellent strength, dimensional stability, and thermal stability, and a polyethylene terephthalate film such as PET or PEN is particularly preferable because of its low cost. The polyester resin constituting the polyester resin film is composed of polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, polyethylene naphthalate in which 80 mol% or more of the structural unit is ethylene naphthalate, Although represented by a polylactic acid film or the like in which 80 mol% or more of the unit is polylactic acid, it is not particularly limited. The polyester resin may be a copolymer. Examples of the copolymer component include diol components such as propylene glycol, diethylene glycol, neopentyl glycol, and cyclohexane dimethanol, isophthalic acid, adipic acid, azelaic acid, and sebacin. The dicarboxylic acid component of an acid and its ester-forming derivative can be used.

  As the white pigment, titanium oxide or zinc oxide can be used, and a white resin film having a whiteness of 80% or more and an opacity of 80% or more is obtained by kneading.

As the black pigment, various colored pigments such as inorganic pigments and organic pigments can be used, but carbon black is preferred from the viewpoints of versatility, price, color development performance, and ultraviolet resistance. The number average particle size of carbon black is preferably 0.01 to 0.5 μm from the viewpoint of color development and dispersibility.
In addition, for the colored resin film, for example, additives such as an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, and a filler do not impair the effects of the present invention. A resin film or the like added within the range can also be used.

  The thickness of the base film used for the solar cell module backside sealing sheet film of the present invention is not particularly limited, but the withstand voltage characteristics of the sealing sheet required when used as a solar cell module, Considering the cost and the like, the range of 10 to 250 μm is preferable.

Moreover, it is also preferable to use a water vapor barrier film in which at least one layer of a metal thin film or an inorganic oxide is formed by a vapor deposition method or the like for the purpose of imparting a water vapor barrier property. The “water vapor barrier film” in the present invention is a film having a water vapor transmission rate of 5 g / (m ² · day) or less measured by the B method described in JIS K 7129 (2000 edition). As a water vapor barrier film, at least one surface of a metal thin film or inorganic oxide is formed by vapor deposition on at least one surface of a polyester resin film such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) or an olefin film such as polypropylene. Although the film which provided the layer of the thing is mentioned, since it is requested | required that electrical insulation is high as a base film used for the film for solar cell module backside sealing sheets, of the metal thin film which is an electroconductive layer A water vapor barrier film having an inorganic oxide layer rather than a layer is preferred. Since the gas barrier property of the water vapor barrier film provided with an inorganic oxide layer by vapor deposition or the like is affected by the thermal dimensional stability of the polyester resin film as the base film, the polyester resin film is biaxial. A stretched film is preferred.

  The thickness of the film that serves as the base for providing the metal thin film and the inorganic oxide layer when using the water vapor barrier film as the base film is because of stability and cost when forming the inorganic oxide layer, Preferably it is the range of 10-125 micrometers, More preferably, it is the range of 10-50 micrometers, Most preferably, about 10-30 micrometers is practical. In the present invention, examples of inorganic oxides preferably used when using a base film having an inorganic oxide layer include metal oxides and metal nitride oxides. The inorganic oxide layer can be formed by vapor deposition, sputtering, ion plating, plasma vapor deposition (CVD), or the like. However, in view of productivity, the vacuum deposition method is the best at present. As the heating means of the vacuum deposition apparatus by the vacuum deposition method, an electron beam heating method, a resistance heating method and an induction heating method are preferable. Examples of the metal oxide composing the inorganic oxide layer include aluminum oxide, magnesium oxide, titanium oxide, tin oxide, indium oxide alloy, and silicon oxide. Silicon and the like can be exemplified. In particular, inorganic oxides such as aluminum oxide, silicon oxide, silicon oxynitride, and mixtures thereof are preferably used from the viewpoint of water vapor barrier properties and production efficiency.

  The thickness of the inorganic oxide layer is appropriately selected depending on the inorganic oxide to be used. In general, the thickness is preferably in the range of 2 to 300 nm, more preferably in the range of 3 to 100 nm, and still more preferably. Is in the range of 5 to 50 nm. When the thickness exceeds 300 nm, the formation speed of the inorganic oxide layer is reduced, so that productivity may be reduced. In particular, when the inorganic oxide layer is a metal oxide layer, its flexibility ( Flexibility is reduced, and the metal oxide layer is cracked or pinholed by external force such as bending or pulling after the formation of the metal oxide layer (in the post-processing step, etc.), and the water vapor barrier property is impaired. There is. On the other hand, when the thickness is less than 2 nm, it is difficult to obtain a uniform film. Further, the thickness may not be sufficient, and the water vapor blocking function may not be sufficiently exhibited.

  Furthermore, the resin film may be subjected to surface treatment such as discharge treatment such as corona discharge or plasma discharge, or acid treatment, if necessary.

[Resin layer]
In the present invention, the resin layer disposed on one side of the base film contains (1) an acrylic polymer and (2) at least one type of blocked isocyanate compound. Such a resin layer needs to be bonded to a filler layer typified by an ethylene-vinyl acetate copolymer resin (EVA) sheet or the like in a thermocompression process when forming a solar cell module, and the bonding strength thereof is extended over a long period. It must be maintained even in environments exposed outdoors. Therefore, the resin constituting the resin layer is preferably a resin designed in consideration of weather resistance. In particular, it is long-term to select a resin having resistance that does not cause a photodegradation reaction with respect to light that passes through the cells and reaches the filler layer and the sealing sheet among rays incident from the front surface of the solar cell module. In order to maintain stable adhesion performance over a long period of time. Therefore, in the present invention, the above-described problems have been solved by using, as a binder resin, an acrylic polymer that is relatively excellent in weather resistance as compared with polyester resins, olefin resins, urethane resins, and the like. In addition, the acrylic polymer has an advantage that it is easy to improve adhesion with the base film and improve dispersibility (compatibility) with other polymers by optimizing selection, combination and blending ratio of monomers.

  The acrylic polymer used in the resin layer in the present invention refers to a polymer containing at least one acrylic monomer in its repeating structure, and may be a copolymer polymer composed of a plurality of monomers. An acrylic monomer means acrylic acid and its ester, and methacrylic acid and its ester. As acrylic acid ester and methacrylic acid ester, methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, Examples include isobutyl methacrylate, t-butyl acrylate, t-butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate. Among these, methyl methacrylate and methyl acrylate are particularly preferable from the viewpoints of versatility, cost, and light stability.

Examples of copolymerizable monomers other than acrylic monomers include unsaturated carboxylic acids such as maleic acid, itaconic acid, crotonic acid and fumaric acid, unsaturated hydrocarbons such as butadiene and ethylene, and vinyl esters such as vinyl acetate. It is done. The resin layer used in the present invention can introduce a crosslinked structure by introducing a reactive functional group and a crosslinking agent capable of reacting with the reactive functional group for the following two reasons. is there.
(I) The solar cell module back surface sealing sheet using the film for solar cell module back surface sealing sheet of the present invention improves the heat resistance of the resin layer because it is exposed to high temperature treatment in the solar cell module manufacturing process. For.
(Ii) To suppress embrittlement of the resin layer due to blending of color pigments and the like, and improve the toughness and strength of the resin layer.

  Examples of the reactive functional group introduced for this purpose include a hydroxyl group, a carboxyl group, an amino group, a glycidyl group, a silyl group, a silanate group, an isocyanate group, and the like. Is appropriately selected in accordance with the reaction mode for forming. Among them, a hydroxyl group, a cyano group, and a silyl group are preferable from the viewpoint of good reactivity, and a hydroxyl group is particularly preferable from the viewpoint of easy availability of the resin and good reactivity. These reactive functional groups are usually introduced into the acrylic polymer by copolymerizing a monomer containing the reactive functional group.

Among acrylic polymers into which a reactive functional group has been introduced, an acrylic polymer containing a hydroxyl group as a reactive functional group is referred to as an acrylic polyol resin. The polymerization monomer of the acrylic polyol resin will be described. Examples of monomers for introducing hydroxyl groups into the acrylic resin include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, Hydroxyl group-containing acrylic monomers such as 2-hydroxyvinyl ether, polyethylene glycol methacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2- Methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hy Hydroxyl-containing vinyl ethers such as loxy-2-methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether and 6-hydroxyhexyl vinyl ether, and hydroxyl-containing allyl ethers such as 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether and glycerol monoallyl ether And the like. These monomers for introducing a hydroxyl group can be selected singly or in combination of two or more.

Next, a crosslinking agent for a resin layer that can be used for the purpose of forming a crosslinked structure by bonding with a reactive functional group introduced into the resin layer and suppressing the heat resistance and embrittlement of the coating film will be described.
In addition to improving the heat resistance, toughness, and strength of the resin layer due to the formation of the above-described crosslinked structure, the crosslinking agent can also have an effect of improving the adhesive force between the base film and the resin layer.

  In the present invention, since an acrylic polymer containing a hydroxyl group is particularly preferably used, it is preferable to use a crosslinking agent capable of reacting with the hydroxyl group, and a polyisocyanate resin is used as a crosslinking agent to generate a urethane bond. It is preferable to form a crosslinked structure. Examples of the polyisocyanate resin used as the crosslinking agent include aromatic polyisocyanate resins, araliphatic polyisocyanate resins, alicyclic polyisocyanate resins, and aliphatic polyisocyanate resins. Each is a resin made from the following diisocyanate compound.

  Examples of the diisocyanate used as a raw material for the aromatic polyisocyanate resin include m- or p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), 4,4′-, 2,4. Examples include '-or 2,2'-diphenylmethane diisocyanate (MDI), 2,4- or 2,6-tolylene diisocyanate (TDI), and 4,4'-diphenyl ether diisocyanate.

  Examples of the diisocyanate used as a raw material for the aromatic aliphatic polyisocyanate resin include 1,3- or 1,4-xylylene diisocyanate (XDI) and 1,3- or 1,4-tetramethylxylylene diisocyanate (TMXDI). Etc. are exemplified.

  Examples of the diisocyanate used as a raw material for the alicyclic polyisocyanate resin include 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate; IPDI). 4,4'-, 2,4'- or 2,2'-dicyclohexylmethane diisocyanate (hydrogenated MDI), methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, and 1,3- Examples thereof include 1,4-bis (isocyanatomethyl) cyclohexane (hydrogenated XDI).

  Examples of the diisocyanate used as a raw material for the aliphatic polyisocyanate resin include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-, 2,3- Examples thereof include 1,3-butylene diisocyanate and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate.

  As a raw material for the polyisocyanate resin, a combination of a plurality of these diisocyanates can be used, and a modified product such as a burette modified product or a nurate modified product can also be used. Among them, as a raw material for polyisocyanate resins, resins containing an aromatic ring having a light absorption band in the ultraviolet region in the resin skeleton tend to yellow with ultraviolet irradiation, so alicyclic polyisocyanates and aliphatic polyisocyanates. It is preferable to use a crosslinking agent mainly composed of isocyanate.

  Moreover, in order to form a crosslinked structure between the polyisocyanate resin and the acrylic polymer having a reactive functional group, a curing step of applying heat is usually required when forming the resin layer. Although the curing conditions differ depending on the combination of the type of acrylic polymer and the type of polyisocyanate compound, for example, curing at 50 ° C. for 3 days can be exemplified. In this curing process, the cross-linking reaction proceeds between the polyisocyanate compound and reactive functional groups such as hydroxyl groups contained in the acrylic polymer, and urethane bonds are formed, improving the strength and toughness of the resin layer. To do.

[Block isocyanate compounds]
The resin layer in the present invention contains an acrylic polymer and at least one type of blocked isocyanate compound.
The blocked isocyanate compound is obtained by blocking the isocyanate group of the isocyanate compound with a blocking agent, and the crosslinking (protection) group is eliminated by heating, and an isocyanate group is generated, so that a crosslinking reaction proceeds. Therefore, below the temperature necessary for elimination of the blocking group, no reactivity is exhibited and the characteristics of the resin layer are stable (good storage stability).

  Examples of the blocking agent used in the blocked isocyanate compound include ε-caprolactam, phenol, cresol, oxime, alcohol and the like, but the present invention is not limited to these. Among the blocked isocyanate compounds, a non-yellowing blocked isocyanate compound that does not have an isocyanate group directly bonded to an aromatic ring is preferable from the viewpoint of preventing yellowing of the resin layer.

  Examples of the blocked isocyanate compound include aromatic blocked isocyanate compounds, araliphatic blocked isocyanate compounds, alicyclic blocked isocyanate compounds, and aliphatic blocked isocyanate compounds, and the following diisocyanate compounds are used as raw materials. Resin.

  Examples of the diisocyanate used as a raw material for the aromatic block isocyanate compound include m- or p-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), 4,4′-, 2,4. Examples include '-or 2,2'-diphenylmethane diisocyanate (MDI), 2,4- or 2,6-tolylene diisocyanate (TDI), and 4,4'-diphenyl ether diisocyanate.

  Examples of the diisocyanate used as a raw material for the araliphatic blocked isocyanate compound include 1,3- or 1,4-xylylene diisocyanate (XDI) and 1,3- or 1,4-tetramethylxylylene diisocyanate (TMXDI). Etc. are exemplified.

  Examples of the diisocyanate used as a raw material for the alicyclic blocked isocyanate compound include 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate; IPDI). 4,4'-, 2,4'- or 2,2'-dicyclohexylmethane diisocyanate (hydrogenated MDI), methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, and 1,3- Examples thereof include 1,4-bis (isocyanatomethyl) cyclohexane (hydrogenated XDI).

  Examples of the diisocyanate used as a raw material for the aliphatic blocked isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-, 2,3- Examples thereof include 1,3-butylene diisocyanate and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate.

  As a raw material for the blocked isocyanate compound, these diisocyanates may be used in combination, or may be used as a modified body such as a burette modified body or a nurate modified body. Among them, as a raw material for the blocked isocyanate compound, a resin containing an aromatic ring having a light absorption band in the ultraviolet region in the resin skeleton is easily yellowed with ultraviolet irradiation. Therefore, an alicyclic blocked isocyanate compound and an aliphatic group are used. It is preferable to use one having a blocked isocyanate compound as a main component.

The film for the solar cell module backside sealing sheet of the present invention is a vacuum because the heat necessary for detachment of the block group is applied in the step of bonding with the filler layer typified by the EVA resin sheet in the vacuum laminating step. During the laminating process, elimination of blocking groups, generation of isocyanate groups, and cross-linking reaction with components contained in the filler layer cause strong and stable adhesion after actual durability exposure after the initial durability test Power. Vacuum lamination refers to a method in which the object to be bonded is sealed with a film or the like, and the pressure inside the sealed body is reduced by pressure by atmospheric pressure, and if the required pressure is obtained, it is not necessarily sealed. It does not indicate that the inside is in a vacuum state.
The block isocyanate compound used in the present invention preferably has a dissociation temperature of the blocking group of about 80 ° C to 150 ° C. When the dissociation temperature is less than 80 ° C., the block group is dissociated in the heating and drying steps when forming the resin layer, and an isocyanate group is generated, so that the curing reaction proceeds, which is a typical EVA resin sheet. The cross-linking reaction may not occur between the filler layer to be formed. On the other hand, when the dissociation temperature of the block group exceeds 150 ° C., the dissociation of the block group does not proceed sufficiently in the vacuum laminating process, so that the cross-linking reaction with the filler layer does not occur and sufficient adhesion is not exhibited. There is a case.

  As shown by the adhesive force development mechanism, the block isocyanate compound is selected based on the block temperature at the heating temperature and the heating time in the vacuum laminating process in which the solar cell module backside sealing sheet film of the present invention is bonded to the filler layer. Is selected from the viewpoint of desorbing at a ratio of a certain amount or more and forming an isocyanate group, and that the isocyanate group undergoes a crosslinking reaction in the same step as the component in the filler layer.

  Moreover, it is preferable to mix | blend an appropriate quantity with respect to the compounding quantity of the block isocyanate compound mix | blended with an acrylic resin layer according to the number of the reactive functional groups in an acrylic polymer structure. Specifically, when the reactive functional group contained in the repeating structure of the acrylic polymer is a hydroxyl group, the blending amount is preferably such that there are 0.1 to 5 blocked isocyanate groups per hydroxyl group. . When the number is less than 0.1, the crosslinking density becomes insufficient, and the durability of the adhesion force is not sufficiently exhibited. On the other hand, when the number is more than 5, many unreacted isocyanate groups remain and react with water vapor in the atmosphere or water vapor in a moist heat test atmosphere, so that the coating film becomes hard and adheres to the base film. In some cases, the adhesion with the filler layer is insufficient.

In the heating step, the reaction in which the blocking group is eliminated and the isocyanate group is generated can be observed by analyzing the surface of the resin layer by the attenuated total reflection method (ATR method). Specifically, measurement at 25 ° C. and measurement after heating at 150 ° C. for 30 minutes, peak intensity (Pah) of internal reference peak (1440 cm ^{−1 to} 1470 cm ⁻¹ ) and peak attributed to blocking group By calculating the relative ratio with the peak intensity (Pbh) of (1550 cm ^{−1 to} 1570 cm ⁻¹ ), how much is the elimination reaction of the blocking group in the heating step (the intensity of the peak corresponding to the protecting group decreases) It is possible to identify whether it has progressed. The block group elimination ratio calculated by the following formula (1) is preferably 0.01 to 0.8, and more preferably 0.1 to 0.7.
(Pbh / Pah) / (Pb / Pa) (1) Formula When the blocking group elimination ratio (Pbh / Pah) / (Pb / Pa) is smaller than 0.01, it is attributed to the blocked isocyanate compound. Adhesive strength is insufficient because there is little formation of a crosslinked structure with the sealing material layer. On the other hand, when (Pbh / Pah) / (Pb / Pa) is greater than 0.8, the amount of isocyanate groups generated from the blocked isocyanate compound becomes excessive, and isocyanate groups that do not lead to a crosslinking reaction tend to remain. In that case, the remaining isocyanate groups react with water vapor in the atmosphere or in a moist heat test environment to cure the coating film. Therefore, the resin layer becomes a hard film, and the toughness and the adhesive force with the substrate are reduced. That is, both the adhesive strength to the filler layer and the durability of the adhesive strength are inferior.

[Coloring pigments]
The inorganic pigment used in the present invention is used for the purpose of cutting ultraviolet rays. At the same time, when viewed from the surface on the innermost layer side of the solar cell module, that is, the front surface of the solar cell module, there is also an object of toning the color tone of the appearance of the back surface sealing sheet that can be seen between the cells. Currently, the outer appearance of the solar cell module backside sealing sheet is mainly white or black, and these pigments themselves absorb and / or reflect light of a specific wavelength, so that the effect of protecting the base sheet is obtained. It is done. In addition, there is an effect that a design pattern such as an electric wiring pattern in the solar cell module can be hidden.

  As the white pigment, titanium oxide having ultraviolet resistance is preferable. From the viewpoint of color development, the number average particle diameter is preferably from 0.1 to 1.0 μm, and more preferably from 0.2 to 0.5 μm from the viewpoint of dispersibility with respect to the acrylic polymer and the blocked isocyanate compound and cost.

  As the black pigment, various colored pigments such as inorganic pigments and organic pigments can be used, but carbon black is preferred from the viewpoints of versatility, price, color development performance, and ultraviolet resistance. The number average particle size of the carbon black is preferably 0.01 to 0.5 μm from the viewpoint of color development, and more preferably 0.02 to 0.1 μm from the viewpoint of dispersibility and cost with respect to the acrylic polymer and the blocked isocyanate compound. .

  What is necessary is just to adjust suitably about the compounding quantity of a color pigment according to the design of the color tone to make it color. However, if the amount of pigment blended is too small, it will not be possible to obtain a color appearance with excellent design, the UV blocking performance will be insufficient, and conversely, if the amount blended is too large, the cost will be high. In some cases, the hardness of the resin layer is greatly improved, the adhesive strength to the filler is easily lowered (adhesive strength failure), and the pigment bleeds out to the surface of the coating film.

  For the above reason, the blending amount of the color pigment is preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass with respect to 100 parts by mass of the resin layer.

  [Other Additives] Further, the resin layer according to the present invention has a heat stabilizer, an antioxidant, a reinforcing agent, a deterioration preventing agent, a weathering agent, a flame retardant, a plasticizer, a release agent, as long as the properties are not impaired. Agents, lubricants, crosslinking aids, pigment dispersants, antifoaming agents, leveling agents, UV absorbers, light stabilizers, thickeners, adhesion improvers, matting agents and the like may be added.

  Examples of heat stabilizers, antioxidants and deterioration inhibitors that can be used include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and mixtures thereof.

Examples of reinforcing agents that can be used include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, and oxidation. Examples include zinc, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate whisker, boron nitride, graphite, glass fiber, and carbon fiber.
As the crosslinking aid that can be used, conventionally known tin-based, other metal-based, organic acid-based, and amino-based crosslinking aids can be used.

  Examples of the ultraviolet absorber that can be used include salicylic acid-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ultraviolet absorbers. Specifically, for example, salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy -5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, benzotriazole 2- (2'-hydroxy-5) '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6 (2H benzotriazol-2-yl) phenol], cyanoacryl Ethyl-2-cyano-3,3′-diphenyl acrylate), others, and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) ) Oxy] -phenol and the like, modified products, polymers, derivatives and the like thereof.

  Examples of the light stabilizer that can be used include hindered amine light stabilizers. Specifically, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, methyl (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis [2,2,6] decanoic acid , 6-Tetramethyl-1-octyloxy] -4-piperidinyl] ester and the like, modified products, polymers and derivatives thereof.

[Thickness of resin layer]
As for the thickness of the resin layer in this invention, 0.1-10 micrometers is preferable, More preferably, it is 0.5-5 micrometers. When this resin layer is formed by a coating method, if the thickness of the resin layer is less than 0.1 μm, a phenomenon such as repellency or film breakage tends to occur during coating, and it is difficult to form a uniform coating film. In some cases, the adhesive force between the film and the base film and / or the filler layer may be reduced, and accordingly, the weather resistance may not be sufficiently developed. On the other hand, if the thickness of the resin layer exceeds 10 μm, high weather resistance can be obtained, but there are restrictions on the coating method when forming the resin layer, and the coating film adheres to the transport roll and the coating film accompanying it. It may become easy to cause peeling.

  Examples of the solvent of the coating liquid for forming the resin layer in the present invention by a coating method include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, methanol, Ethanol and water can be exemplified, and the properties of the coating liquid may be either an emulsion type or a dissolution type.

  The method for forming the resin layer on the substrate film in the present invention is not particularly limited, and a known coating technique can be used. As the coating method, various methods can be applied. For example, a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, or a combination of these methods can be used. it can. Among these, the gravure roll coating method is preferable in that the stability of the coating layer forming composition can be increased.

[Solar cell module back side sealing sheet]
The film for solar cell module back surface sealing sheet obtained by the present invention may be used alone as a solar cell module back surface sealing sheet, or another resin film may be laminated to form a solar cell module back surface sealing sheet. In the latter case, a known dry laminating method can be used as a method of laminating another resin film and processing it into a sheet shape. Bonding of resin films using the dry laminating method is based on polyether polyurethane resins, polyester polyurethane resins, polyester resins, polyepoxy resins, etc., and polyisocyanate resins containing isocyanate groups are used as crosslinking agents. The known adhesive for dry lamination can be used. The adhesive layer formed using these adhesives does not cause delamination or the like due to deterioration of the adhesive strength due to long-term outdoor use, and it leads to a decrease in light reflectance. It is preferable that it does not change. Moreover, as thickness of an adhesive bond layer, Preferably it is the range of 1-5 micrometers. If it is less than 1 μm, it may be difficult to obtain sufficient adhesive strength. On the other hand, if it exceeds 5 μm, the coating speed of the adhesive does not increase, the aging performed for the purpose of developing the adhesive force (promoting the crosslinking reaction between the main agent and the crosslinking agent), and further the adhesive. Production will take longer due to increased usage.
Further, depending on the configuration of the solar cell module back surface sealing sheet, it is also conceivable that UV light reaches the adhesive layer and induces photodegradation of the resin. From such a viewpoint, the resin used for forming the adhesive layer is preferably one that does not contain an aromatic ring or has an aliphatic skeleton or an alicyclic skeleton that has a low content.

  Next, it describes about the solar cell module back surface sealing sheet using the film for solar cell module back surface sealing sheets of this invention. The solar cell module back surface sealing sheet is required to have various characteristics represented by water vapor barrier properties, light reflectivity, long-term moisture and light resistance, adhesion to cell fillers, electrical insulation, and the like. At present, in order to satisfy these required characteristics, various sheet designs (laminate designs) that combine processing techniques such as various functional films, vapor deposition, and wet coating are made in accordance with the concept of functional division.

  Also in the present invention, the film for backside sealing sheet of the solar cell module of the present invention includes a film having hydrolysis resistance, a white film, a film having inorganic oxide deposition, and a weatherproof / ultraviolet blocking resin layer on the outer layer side. By laminating a film selected from the group consisting of films having the above and / or forming a weather resistant / ultraviolet blocking resin layer, a solar cell module backside sealing sheet satisfying various required characteristics can be obtained. Especially, it is preferable to laminate | stack the film which has a weather resistance and a ultraviolet-ray blocking layer on the surface on the opposite side to the surface which provided the resin layer of the film for solar cell module backside sealing sheets. At this time, it is preferable to use a film having hydrolysis resistance as the base film.

[Weather-resistant / UV-blocking resin layer]
The weather-resistant / ultraviolet-blocking resin layer in the film having a weather-resistant / ultraviolet-blocking resin layer on the outer layer side preferably used by being laminated on the film for solar cell module backside sealing sheet of the present invention of the present invention, or the present invention The weather resistant / ultraviolet blocking resin layer preferably formed and used for the film for solar cell module backside sealing sheet of the invention is a layer containing an ultraviolet absorber. As the resin forming the layer containing the ultraviolet absorber, fluorine-containing resin, acrylic resin, polyester resin, polyolefin resin, polyamide resin, or the like can be used. Specifically, the fluorine-containing resin includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer resin (ETFE), ethylene-chlorotrifluoroethylene. Copolymer resin (ECTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), etc. As acrylic resins, polymethyl methacrylate, polyacrylate, acrylic polyol resins crosslinked with various crosslinking materials, etc. Polyester resins include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) polybutylene terephthalate (PBT). Polyolefin resins include polypropylene and polyethylene. Ethylene - vinyl acetate (EVA), and cyclic olefin resins, a polyamide resin, nylon 6, nylon 6,6, nylon 11, and nylon 12 can be exemplified.

[UV absorbers used in weathering and UV blocking resin layers]
Next, examples of the ultraviolet absorber used in the weather resistant / ultraviolet blocking resin layer include inorganic ultraviolet absorbers and organic ultraviolet absorbers. Examples of inorganic ultraviolet absorbers include titanium oxide and zinc oxide that can also be used as white pigments, and carbon black that can also be used as black pigments. Examples of organic ultraviolet absorbers include salicylic acid and benzophenone. Examples thereof include UV absorbers such as benzotriazole and cyanoacrylate. Specific examples of the organic ultraviolet absorber include salicylic acid-based pt-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone-based 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2 -Hydroxy-4-methoxy-5-sulfobenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, 2- (benzotriazole-based 2- ( 2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetra Methylbutyl) -6- (2Hbenzotriazol-2-yl) phenol], Anoacrylate-based ethyl-2-cyano-3,3′-diphenyl acrylate), others, and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) ) Oxy] -phenol and the like, modified products, polymers, derivatives and the like thereof. The solar cell module which is the application of the present invention is used outdoors for 20 years, sometimes longer than that, and as an ultraviolet absorber to be used, an inorganic ultraviolet absorber is more durable from the viewpoint of durability. preferable.

[Light stabilizers used in weathering and ultraviolet blocking resin layers]
Examples of the light stabilizer used in the weather resistant / ultraviolet blocking resin layer include hindered amine-based light stabilizers. Specifically, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, methyl (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis [2,2,6] decanoic acid , 6-Tetramethyl-1-octyloxy] -4-piperidinyl] ester and the like, modified products, polymers and derivatives thereof.

  In the present invention, among the above, it is preferable to use an acrylic polyol-based resin obtained by copolymerizing an ultraviolet absorber and a light stabilizer on the weatherproof / ultraviolet blocking resin layer. In addition, it is more preferable to mix the acrylic polyol-based resin copolymerized with the ultraviolet absorber and the light stabilizer and the inorganic ultraviolet absorber to form a weather resistant / ultraviolet blocking resin layer because the ultraviolet blocking performance is further improved. .

[Other additives that can be used in weather-resistant / UV-blocking resin layers]
In addition, the weather resistant / ultraviolet blocking resin layer may contain additives such as an antistatic agent, a stabilizer, an antioxidant, a reinforcing agent, a plasticizer, a lubricant, a filler, a color pigment, etc. It can add within the range which does not impair the effect of invention. For example, heat stabilizers, antioxidants, and deterioration inhibitors include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, or mixtures thereof.

  Examples of the reinforcing agent include clay, talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, zinc oxide, Zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate whisker, boron nitride, graphite, glass fiber, carbon fiber and the like can be mentioned.

[Method for producing weatherable / ultraviolet blocking resin layer]
The method of laminating the weather resistant / ultraviolet blocking resin layer is not particularly limited, but the melt extrusion method or the coating method of applying a liquid paint to be the weather resistant / ultraviolet blocking resin layer and crosslinking by heat, light, electron beam, etc. Further, there can be exemplified a laminating method in which a film that becomes a weather resistant / ultraviolet ray blocking resin layer and an adhesive are used for bonding.

  Various methods can be applied as a coating method in the case of forming by a coating method, such as a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, or a combination thereof. Can be used. Among these, the gravure roll coating method is a preferable method for increasing the stability of the coating layer forming composition. Examples of the solvent for the coating liquid include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, methanol, ethanol and water. The properties of the liquid may be either an emulsion type or a dissolution type.

  In addition, a known dry laminating method can be used for a laminating method in which an adhesive is used to bond a film that becomes a weather resistant / ultraviolet blocking resin layer. Bonding of resin films using the dry laminating method is a known adhesive for dry laminating using polyether polyurethane, polyester polyurethane, polyester, polyepoxy resin, etc. as the main agent and blocked isocyanate compound as a crosslinking agent. An agent can be used. For the adhesive layer formed using these adhesives, use an adhesive layer that does not cause delamination due to deterioration in outdoor use over a long period of time, leading to a decrease in light reflectance. It is preferable to use one that does not cause yellowing. Moreover, it is preferable that it is the range of 1-10 micrometers as thickness of an adhesive bond layer. If it is less than 1 μm, it may be difficult to obtain sufficient adhesive strength. On the other hand, if it exceeds 10 μm, the speed of adhesive coating does not increase, the aging performed for the purpose of developing adhesive force (promoting the cross-linking reaction between the main agent and the cross-linking agent) requires a long time, and further the use of the adhesive Production will take longer due to the increase in quantity.

[Solar cell module]
When using the solar cell module encapsulating sheet comprising the film for solar cell module back encapsulating sheet or the film for solar cell module back encapsulating sheet of the present invention prepared as described above for a solar cell module, the back surface of the solar cell module The surface of the resin layer of the film for sealing sheets is adhered to the layer of the solar cell module cell filler and incorporated in the solar cell module.

  Examples of the filler used in the solar cell module include EVA (ethylene-vinyl acetate copolymer resin), polyvinyl butyral, silicone resin, polyurethane, and modified polyolefin, but the present invention is limited to these. is not. Among these, EVA is preferable from the viewpoint of weather resistance, flame retardancy, and member cost.

  Moreover, it is preferable that a solar cell module cell filler contains a polyisocyanate compound.

  Moreover, the film for solar cell module backside sealing sheet of this invention is not restrict | limited by the kind (Crystal silicon, thin film silicon, a compound type thin film, an organic type thin film, etc.) of an electric power generation layer, Any type of The solar cell module can be preferably used.

  In this example, “part” means “part by mass” unless otherwise specified.

<Evaluation method of characteristics>
The characteristics evaluation method used in this example is as follows.

(1) Mass per unit area of resin layer After forming a resin layer on a base film, it cut out to the area of 0.05 m < ² >, and made the mass of the test piece mass (1). Next, the resin layer was dissolved and removed from the test piece in n-butyl acetate, and the mass of the test piece was measured again to obtain mass (2). Subsequently, the mass per unit area was calculated based on the following formula. This measurement was performed on three test pieces, and the average value was calculated.
Application amount [g / m ² ] = {(mass (1)) − (mass (2))} / 0.05.

(2) Adhesive strength of resin layer / base film The adhesive strength between the resin layer and the base film of the produced solar cell module backside sealing sheet film is the same as the method described in JIS K 5400 (1990 edition). Based on this, a cross-cut test was conducted and the following characteristics were classified.
○: Residue of 100 mass resin layer / 100 mass Δ: Residual of 81-99 mass resin layer / 100 mass x: Residual resin layer of 80 mass or less / 100 mass.

(3) Adhesive strength with filler layer (3-1) Initial adhesive strength Based on JIS K 6854-2 (1999 edition), the adhesive strength with the EVA sheet used as the filler was measured. The tested pseudo solar cell module sample is obtained by stacking an EVA sheet on the film resin layer surface for the solar cell module backside sealing sheet, and further overlaying a 0.3 mm thick semi-tempered glass on the surface, using a commercially available vacuum laminator. After pressure reduction, what was pressed for 15 minutes with a load of 1 atm under 142 ° C. heating conditions was used. As the EVA sheet, a 450 μm thick sheet (Fast cure type) manufactured by Sanvik Co., Ltd. was used. The width of the test piece of the adhesive strength test was 10 mm, and each of the two test pieces was measured once, and the average value of the two measured values was taken as the value of the adhesive strength. It was judged that the adhesive strength was 20 N / 10 mm or more at a level where there was no practical problem.

(3-1) Adhesive strength after heat-and-moisture resistance test The pseudo solar cell module was subjected to a wet heat treatment for 2000 hours in an environment of 85 ° C. and 85% RH using a constant temperature and humidity oven manufactured by Espec. Thereafter, the same measurement as in (3-1) was performed.

(4) Blocking resistance test Ten test pieces were cut out in a size of 5 cm square from the film for the back surface sealing sheet of the solar cell module, overlapped so that the surfaces on the side of the resin layer did not face each other, and 5 kgf using an ink blocking tester. The sample was left in an environment of 40 ° C. for 1 week under a load of / cm ² . Thereafter, the sample was removed from the ink blocking tester, and the presence or absence of adhesion between the test pieces was confirmed. At this time, it was determined that no blocking occurred when none of the ten test pieces showed sticking.
(5) Evaluation of blocking group elimination ratio by ATR method The absorption spectrum of the surface of the resin layer obtained by the attenuated total reflection method (ATR method) was measured according to the following apparatus and conditions.
Device name: FTS-55A (FT-IR manufactured by Bio-Rad Digilab)
Measurement conditions Light source: Special ceramics Detector: DTGS
Purge: Nitrogen gas resolution "4cm ^-1
Integration count: 128 Measurement method: Attenuated total reflection (ATR) method ATR crystal: Diamond Incident angle: 45 °
Measurement temperature: 25 ° C. (measurement result 1), after heating at 150 ° C. for 30 minutes (measurement result 2)
Temperature rising rate: 10 ° C / min
(Preparation of paints 1-5 for resin layer formation)
Each material was weighed and mixed at the blending ratio shown in Table 1, and the coating materials 1 to 5 for forming a resin layer were obtained by stirring at room temperature for 10 minutes using a magnetic stirrer.
Acrylic polymer-containing paint (i): Coating agent “PRC-004” (solid content concentration: 30% by mass) manufactured by Toyo Ink SC Holdings Co., Ltd. containing an acrylic copolymer and a blocked isocyanate compound.
Acrylic polymer-containing paint (ii): A coating agent “PRC-205KA” (solid content concentration: 40 mass%) manufactured by Toyo Ink SC Holdings Co., Ltd. containing an acrylic copolymer, a blocked isocyanate compound, and an inorganic black pigment.
Acrylic polymer-containing paint (iii): Coating agent “PRC-205KB” (solid content concentration: 40% by mass) manufactured by Toyo Ink SC Holdings Co., Ltd. containing an acrylic copolymer.
Acrylic polymer-containing paint (iv): A coating agent “PRC-102WA” (solid content concentration: 40 mass%) manufactured by Toyo Ink SC Holdings Co., Ltd., containing an acrylic copolymer, a blocked isocyanate compound, and an inorganic black pigment.
Acrylic polymer-containing paint (v): Paint composition obtained by removing the block isocyanate compound from the acrylic polymer-containing paint 1 (solid content concentration: 30% by mass)
Acrylic polymer-containing paint (vi): “HALS HYBRIT” UVG-13 (manufactured by Nippon Shokubai Co., Ltd.) containing an acrylic copolymer resin having a resin skeleton in which a main chain is crosslinked with a light stabilizer and an ultraviolet absorber. Solid content concentration 40 mass%).
Crosslinking agent 1: Coating agent “PRC-205C” (solid content concentration 50 mass%) manufactured by Toyo Ink SC Holdings Co., Ltd. containing blocked isocyanate compound A
Crosslinking agent 2: Coating agent “PRC-102WB” (solid content concentration: 50 mass%) manufactured by Toyo Ink SC Holdings Co., Ltd. containing blocked isocyanate compound B

Example 1
A black polyethylene terephthalate film “Lumirror” (registered trademark) X30 (50 μm) manufactured by Toray Industries, Inc. was prepared as a base film. The resin layer-forming coating material 1 is applied to one surface of this base film using a wire bar, dried at 100 ° C. for 60 seconds, and the resin layer so that the coating amount after drying is 1.0 g / m ^2. Was provided. Thus, the film 1 for solar cell module back surface sealing sheets was manufactured.

(Example 2)
The film 2 for solar cell module backside sealing sheets was manufactured like the method of Example 1 except having provided the resin layer so that the coating amount after drying might be 3.0 g / m < ² >.

(Example 3)
A white, weather-resistant polyethylene terephthalate film “Lumirror” (registered trademark) MX11 (75 μm) manufactured by Toray Industries, Inc. was used as the base film, and the surface on which the resin layer was formed was subjected to corona treatment. A resin layer is provided on the corona-treated surface of the base film using the resin layer forming coating 1 so that the coating amount after drying is 3.0 g / m ^{2 in} the same manner as in Example 1. It was. Thus, the film 3 for solar cell module back surface sealing sheets was manufactured.

Example 4
Example 2 except that a polyethylene terephthalate film “Lumirror” (registered trademark) S10 (250 μm) manufactured by Toray Industries, Inc. was used as the base film, and the resin layer forming paint 2 was used instead of the resin layer forming paint 1 The film 4 for solar cell module backside sealing sheets was manufactured like the method of description.

(Example 5)
A resin layer is formed using a hydrolysis-resistant polyethylene terephthalate film “Lumirror” (registered trademark) X10S (250 μm) having a cyclic trimer content of 1 (mass% or less) manufactured by Toray Industries, Inc. as a base film. The surface to be subjected to corona treatment was applied to the corona-treated surface of this base film using the resin layer forming coating material 3 in the same manner as described in Example 1, and the coating amount after drying was 3.0 g / The resin layer was provided so that it might become m ^2. Thus, the film 5 for solar cell module back surface sealing sheets was manufactured.

(Comparative Example 1)
Without forming an easy-adhesive resin layer, “Lumirror” (registered trademark) X30 (manufactured by Toray Industries, Inc., 50 μm) was used as the film 6 for a solar cell module back surface sealing sheet.

(Comparative Example 2)
Without forming an easy-adhesive resin layer, “Lumirror” (registered trademark) MX11 (manufactured by Toray Industries, Inc., 75 μm) was used as the solar cell module back surface sealing sheet film 7.

(Comparative Example 3)
Without forming an easy-adhesive resin layer, “Lumirror” (registered trademark) S10 (manufactured by Toray Industries, Inc., 250 μm) was used as the film 8 for solar cell module back surface sealing sheet.

(Comparative Example 4)
Without forming an easy-adhesive resin layer, “Lumirror” (registered trademark) X10S (manufactured by Toray Industries, Inc., 250 μm) was used as the film 9 for the back surface sealing sheet of the solar cell module.

(Comparative Example 5)
A solar cell module back surface sealing sheet film 10 was produced in the same manner as in Example 2 except that the easy-adhesive resin layer-forming coating material 4 was used instead of the resin layer-forming coating material 1.

(Comparative Example 6)
A solar cell module backside sealing sheet film 11 was produced in the same manner as in Example 2 except that the easy-adhesive resin layer-forming coating material 5 was used instead of the resin layer-forming coating material 1.

  The solar cell sealing sheet of the present invention is excellent in adhesive strength to filler, storage stability, productivity and environmental resistance, and is preferably used in a solar cell module. Therefore, the solar cell sealing sheet of the present invention A sheet and a solar cell module using the sheet are useful.

Claims (6)

A solar cell module back surface sealing sheet film having a resin layer containing an acrylic polymer and at least one type of blocked isocyanate compound on one side of a base film,
Peak intensity of ^{1440cm -1 ~1470cm} -1 of the absorption spectrum of the surface of the resin layer at 25 ° C. obtained by attenuated total reflection method (ATR method) as the ^Pa, and Pb the peak intensity of 1550cm ^-1 ~1570cm -1 The film for solar cell module backside sealing sheets, wherein the value of the ratio of Pb to Pa (Pb / Pa) is 0.01 to 0.1. The peak intensity of ^{1440cm -1 ~1470cm} -1 of the absorption spectrum of the surface of the resin layer obtained by the attenuated total reflection method (ATR method) After heating for 30 minutes at 0.99 ° C. and ^Pah, the 1550cm ^-1 ~1570cm -1 The film for solar cell module backside sealing sheet according to claim 1, wherein {(Pbh / Pah) / (Pb / Pa)} is in the range of 0.01 to 0.8 when the peak intensity is Pbh.   The film for solar cell module backside sealing sheet according to claim 1, wherein the base film is a polyester film.   The base film is a polyethylene terephthalate film. The film for solar cell module backside sealing sheet according to any one of claims 1 to 3.   A solar cell module manufacturing method comprising: adhering a surface of the resin layer of the film for backside sealing sheet of a solar cell module according to any one of claims 1 to 4 and a layer of a solar cell module cell filler. Method.   The method for manufacturing a solar cell module according to claim 5, wherein the solar cell module cell filler contains a polyisocyanate compound.