JP2011222575A - Sheet for sealing backside of solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet for sealing backside of a solar battery having excellent adhesion to sealing materials, storage stability, productivity, and weather resistance, and to provide a solar battery module using the sheet.SOLUTION: A sheet for sealing backside of a solar battery includes a base film, at least one surface of which is provided with an easily-adhesive resin layer containing fluorine resin and inorganic pigment. A solar battery module is made by bonding the easily-adhesive resin layer of the sheet for sealing backside of the solar battery to a silicon cell filler layer surface of the solar battery module.

Description

  TECHNICAL FIELD The present invention relates to a solar cell back surface sealing sheet excellent in adhesion to sealing material and environmental resistance that can withstand use in a severe outdoor environment for a long period of time, and a solar cell module using the solar cell back surface sealing sheet.

  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 back side sealing sheet has mechanical strength, weather resistance, heat resistance, water resistance, chemical resistance, light reflectivity, water vapor barrier property, thermal adhesiveness with fillers typified by EVA resin, and design properties. Not only are properties such as adhesion to the outermost terminal box mounting silicone resin required, but also exposure to ultraviolet light requires excellent light resistance.

  As a film for the backside sealing material used conventionally, a white polyvinyl fluoride film (DuPont Co., Ltd., trade name: Tedlar (registered trademark)) can be exemplified, and a laminated structure in which a polyester film is sandwiched between the films. The back surface sealing material is widely used in such applications. 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. Has been proposed (Patent Document 2).

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

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. Moreover, since the surface of the coating film formed with a hot-melt resin is relatively highly tacky, there is also a problem that the coated film roll is pseudo-adhered (blocked) between the layers in summer. Furthermore, since the back surface sealing sheet is exposed to light transmitted between the silicon cells, the back surface sealing sheet may be deteriorated by light, resulting in problems such as yellowing.
In the backside sealing sheet having a configuration in which the polyester film is sandwiched between the polyvinyl fluoride films, since the adhesive strength with the sealing material layer and the light resistance are excellent, there is no such problem, but it is expensive. It is also an obstacle in terms of reducing the price of solar cell modules.
The object of the present invention is to provide a sufficient adhesive strength with an ethylene-vinyl acetate copolymer-based filler layer required as a solar cell back surface sealing sheet in view of the above-mentioned problems of the prior art, storage stability of a film roll, It is to provide a solar cell back surface sealing sheet excellent in 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, the solar cell back surface sealing sheet of the present invention is
(1)
A solar cell back surface sealing sheet using a base film in which an easily adhesive resin layer containing a fluorine resin and an inorganic pigment is formed on at least one surface;
(2)
The easily adhesive resin layer contains at least one polyisocyanate resin selected from the group consisting of aliphatic polyisocyanate resins, alicyclic polyisocyanate resins, and araliphatic polyisocyanate resins, and the fluororesin is tetrafluoroethylene. The solar cell backside sealing sheet according to (1), which is a copolymer resin that contains a hydroxyl group-containing monomer as a cross-linking point between a hydroxyl group and an isocyanate group in a repeating structure,
(3)
The solar cell backside sealing sheet according to (1), having at least one weatherproof / ultraviolet blocking resin layer containing an ultraviolet absorber on the side opposite to the easily adhesive resin layer,
(4)
The solar cell back surface sealing sheet according to (1), wherein the inorganic pigment is composed of titanium oxide and carbon black,
(5)
The ratio A / B of the hydroxyl group equivalent (A) in the fluororesin and the isocyanate group equivalent (B) in the polyisocyanate resin in the easy-adhesive resin layer is a blend ratio of 10/1 to 10/7 (1 ) Solar cell back surface sealing sheet,
(6)
(1) to (5) a solar cell module formed by adhering the easily adhesive resin layer of the solar cell backside sealing sheet and the silicon cell filler layer surface of the solar cell module,
It is.

  Moreover, the solar cell module of this invention adhere | attaches the easily adhesive resin layer of the solar cell backside sealing sheet | seat of this invention, and the silicon cell filler layer surface of a solar cell module.

  According to the present invention, a solar cell back surface sealing having an easy-adhesive resin layer excellent in adhesion to sealing material, storage stability, productivity and weather resistance that can withstand use in a severe outdoor environment for a long period of time. A stop sheet is obtained.

  Moreover, if the solar cell back surface sealing material sheet | seat 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.

[Solar cell backside sealing sheet]
The solar cell back surface sealing sheet of the present invention is a non-light-receiving surface side sealing material layer in a solar cell module structure, in which a base film having an easily adhesive resin layer containing a fluorine resin and an inorganic pigment is formed on at least one surface. By arranging it on the surface on the side in contact with the sealant, it is possible to obtain better sealing material adhesion, storage stability, productivity and weather resistance than before.

[Base film]
In the solar cell back surface sealing sheet of the present invention, various resin films can be used as the base material when forming the easily adhesive resin layer disposed on the surface in contact with the non-light-receiving surface side sealing material layer. . Specific examples include polyester resin 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. It is done. Among them, a polyester resin film is preferable because it is excellent in strength, dimensional stability, and thermal stability, and a polyethylene terephthalate 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 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.

  The solar cell backside sealing sheet of the present invention is preferably a resin film excellent in hydrolysis resistance as a base film, that is, a hydrolysis resistance film, from the viewpoint of being used in an environment exposed directly to the outside air. 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 with a high content of it causes a decrease in mechanical strength, cracks, breakage of materials, etc. due to the progress of hydrolysis due to rainwater, etc. in long-term exposure such as outdoors. . On the other hand, in a hydrolysis resistant film, a polyester resin film is formed from a polyester resin having a cyclic trimer content obtained by polymerization by a solid phase polymerization method of 1.0% by mass or less. Thus, 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 cyclic trimer content is measured by, for example, measuring the content (% by weight) relative to the resin weight by measuring by liquid chromatography using a solution in which 100 mg of a polymer is dissolved in 2 ml of orthochlorophenol. Is required.

  In addition, the resin film constituting the solar cell back surface sealing material sheet may include, for example, an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, a filler, a coloring pigment, and the like as necessary. It is also possible to use a resin film or the like in which the above additives are added within a range not impairing the effects of the present invention.

  Specifically, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), resin films such as polycarbonate, polymethyl methacrylate, polyacrylate, polypropylene, and polyethylene, and a white pigment on a resin film obtained by mixing these resins A film obtained by forming a resin raw material into which knead has been kneaded. 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. Among them, a polyester resin film is preferable because it is excellent in strength, dimensional stability, and thermal stability, and a polyethylene terephthalate film such as PET or PEN is particularly preferable because it is inexpensive. 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.
In addition, the white resin film may be added with additives such as an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, and a filler, as necessary, without impairing the effects of the present invention. A resin film or the like added within the range can also be used.

  The thickness of the resin film for the solar cell backside sealing material is not particularly limited, but is preferably in the range of 25 to 250 μm in view of the withstand voltage characteristics and cost of the sealing sheet.

The base film may be a water vapor barrier film in which at least one inorganic oxide layer is formed by vapor deposition for the purpose of imparting water vapor barrier properties. The “water vapor barrier film” in the present invention is a resin film having a water vapor transmission rate of 5 g / (m ² · day) or less measured by the method B described in JIS K7129 (2000 version). As the water vapor barrier resin film, at least one metal thin film layer or the like is formed 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 by vapor deposition or the like. Although the film which provided the inorganic oxide layer is mentioned, since it is requested | required that electrical insulation is high as a back surface sealing material for solar cells, it is not a metal thin film layer which is an electroconductive layer, but an inorganic oxide layer Is preferred. Among the base films, polyester resin films are preferable because of excellent strength, dimensional stability, and thermal stability, and polyethylene terephthalate films such as PET and PEN are particularly preferable because they are inexpensive. The polyester-based resin constituting the polyester-based resin film is represented by 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, and the like. However, 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. The gas barrier property of a film provided with an inorganic oxide layer by vapor deposition or the like is caused by at least the thermal dimensional stability of a polyester resin film as a base material. Therefore, a polyester resin film is a film stretched in a biaxial direction. Preferably there is.

  The thickness of the resin film is preferably in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, particularly preferably for reasons such as stability and cost when forming the inorganic oxide layer. About 10 to 30 μm is practical.

  As an inorganic oxide which comprises the inorganic oxide layer formed in this invention, a metal oxide, a metal nitride oxide, etc. can be illustrated. 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 constituting the inorganic oxide layer include aluminum oxide, magnesium oxide, titanium oxide, tin oxide, indium oxide alloy, and silicon oxide. The metal nitride oxide includes silicon oxynitride. Etc. can be illustrated. 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 film thickness of the inorganic oxide layer is appropriately selected depending on the type and configuration of the inorganic substance used, but generally it is preferably in the range of 2 to 300 nm, more preferably in the range of 3 to 100 nm, Preferably it is the range of 5-50 nm. When the film thickness exceeds 300 nm, especially in the case of a metal oxide layer, the flexibility (flexibility) decreases, and the thin film is cracked by an external force such as bending or pulling after film formation (in a post-processing step or the like). May cause pinholes and the like, and water vapor barrier properties may be significantly impaired. Moreover, since the formation speed of an inorganic layer falls, productivity may be reduced remarkably. On the other hand, when the film thickness is less than 2 nm, it is difficult to obtain a uniform film, and the film 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.

[Easily adhesive resin layer]
The easy-adhesion resin layer laminated on the base film in the present invention is composed of (1) a fluorine-based resin and (2) an inorganic pigment. The easy-adhesive resin layer needs to be in close contact with a sealing material layer typified by an ethylene-vinyl acetate copolymer resin (EVA) sheet in the thermocompression bonding process when forming a solar cell module, It needs to be maintained even in an environment where it is exposed outdoors for a long time. Therefore, the resin forming the easy-adhesion layer is preferably a resin having weather resistance. In particular, it is possible to select a resin exhibiting resistance that does not cause a photodegradation reaction with respect to light that passes through the cells and reaches the sealing material layer and the back surface sealing material layer among light rays incident from the front surface of the solar cell module. In order to maintain stable adhesion performance over a long period of time, it is necessary. In general, as a technique for improving the light resistance of a resin layer, an organic ultraviolet absorber or an inorganic ultraviolet absorber alone or a mixture of a plurality of types is mixed with a binder resin, and radicals excited by light are lost. A light stabilizer (HALS) is used in combination for the purpose of increasing the light stability by the mechanism to be activated. However, in a resin layer formed by post-adding a UV absorber or light stabilizer to a binder resin, the UV absorber or light stabilizer is removed from the coating film in a high-temperature humidified environment or with UV light reception. Bleeding out to the surface not only changes wettability, adhesion of the coating surface, etc., but also tends to cause problems such as loss of the UV light cutting performance that was initially expressed. On the other hand, in this invention, compared with polyester resin, an olefin resin, an acrylic resin, etc., the solution of said subject was aimed at by using as a binder resin the fluorine resin which is extremely excellent in light resistance. Moreover, since a fluorine resin is excellent also in a flame retardance, it also has the effect of improving the flame retardance of the film for solar cell backside sealing sheets. In addition, the solar cell backside sealing sheet using the film for solar cell backside sealing sheet of the present invention is improved in adhesion with the base film, and the coating film because it is exposed to high temperature treatment in the solar cell module manufacturing process. For the purpose of improving the heat resistance of the resin, a resin in which a curable functional group is introduced into the fluororesin so that an appropriate crosslinked structure can be introduced is preferable.

  Examples of the functional group that imparts curability to the fluororesin 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, as appropriate depending on the ease of resin production and the curing system. Selected. Among these, a hydroxyl group, a cyano group, and a silyl group are preferable from the viewpoint of good curing reactivity, and a hydroxyl group is particularly preferable from the viewpoint of easy availability of the resin and good reactivity. These curable functional groups are usually introduced into the fluororesin by copolymerizing a curable functional group-containing monomer.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2-methyl. Examples include hydroxyl group-containing vinyl ethers such as butyl vinyl ether, 5-hydroxypentyl vinyl ether, and 6-hydroxyhexyl vinyl ether, and hydroxyl group-containing allyl ethers such as 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, and glycerol monoallyl ether. . Among these, hydroxyl group-containing vinyl ethers, particularly 4-hydroxybutyl vinyl ether and 2-hydroxyethyl vinyl ether are preferred in that they are excellent in polymerization reactivity and functional group curability. Examples of other hydroxyl group-containing monomers include hydroxyalkyl esters of (meth) acrylic acid such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.

  Examples of the fluorine-based resin into which the curable functional group is introduced include a perfluoroolefin-based resin mainly composed of a perfluoroolefin unit from the viewpoint of the structural unit. Specific examples include a homopolymer of tetrafluoroethylene (TFE), a copolymer of TFE and hexafluoropropylene (HFP), perfluoro (alkyl vinyl ether) (PAVE), and the like, and further copolymerizable therewith. Examples thereof include copolymers with other monomers.

  Examples of other copolymerizable monomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, and cyclohexyl carboxylic acid. Carboxylic acid vinyl esters such as vinyl, vinyl benzoate, para-t-butyl vinyl benzoate, alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, ethylene, propylene, n-butene, isobutene, etc. Examples include fluorine-based olefins, fluorine-based monomers such as vinylidene fluoride (VdF), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), and fluorovinyl ether. It is not limited only thereto.

  Of these, TFE resins mainly composed of TFE are preferable in terms of excellent pigment dispersibility, weather resistance, copolymerization, and chemical resistance.

  Specific examples of the curable functional group-containing perfluoroolefin resin include a TFE / isobutylene / hydroxybutyl vinyl ether / other monomer copolymer, TFE / vinyl versatate / hydroxybutyl vinyl ether / other monomer, and the like. Copolymer, TFE / VdF / hydroxybutyl vinyl ether / copolymer of other monomers, etc., especially TFE / isobutylene / hydroxybutyl vinyl ether / copolymer of other monomers, TFE / versaic acid Vinyl / hydroxybutyl vinyl ether / copolymers of other monomers are preferred. Examples of the TFE-based curable resin paint include the Zaffle GK series manufactured by Daikin Industries, Ltd.

  As for the thickness of the resin layer in this invention, 0.2-10 micrometers is preferable, More preferably, it is 1-5 micrometers. When this resin layer is formed by a coating method, if the thickness of the resin layer is less than 0.2 μm, a phenomenon such as repellency or film breakage tends to occur during coating, and it is difficult to form a uniform coating film. Adhesive strength to the film and the sealing material layer, and above all, weather resistance may not be sufficiently exhibited. On the other hand, when the thickness of the resin layer exceeds 10 μm, the weather resistance is sufficiently developed, but the coating method is restricted, the production cost becomes high, the coating film adheres to the transport roll, and the coating film peels off accompanying it. There is a concern that it is likely to occur.

  Examples of the solvent of the coating liquid for forming the resin layer in the present invention by the coating method include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, methanol, Examples include ethanol and water, 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 base film 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 a preferable method for increasing the stability of the coating layer forming composition.

[Coloring pigments]
The inorganic pigment used in the present invention is used for the purpose of ultraviolet protection. At the same time, when viewed from the innermost layer of the back surface sealing sheet, 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, white and black are mainly used for the appearance of solar cell backside sealing sheets, 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 size 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 fluororesin 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 diameter of 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 with respect to the fluororesin and cost.

  The blending amount of the color pigment may be appropriately adjusted according to the design of the color tone to be developed. 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. There are concerns that the hardness of the resin layer is greatly improved, that the adhesion to the sealing material is likely to be lowered (adhesion failure), and that the pigment bleeds out to the surface of the coating film.

  For the above reason, the blending amount of the color pigment is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass with respect to 100 parts by mass of the resin layer.

[Crosslinking agent]
Further, as described above, a crosslinking agent having a functional group capable of reacting with the hydroxyl group of the fluororesin may be blended for the purpose of improving the characteristics of the resin layer. When a crosslinking agent is used in combination, the effect of improving the adhesion between the base film and the resin layer or improving the heat resistance of the resin layer accompanying the introduction of a crosslinked structure can be obtained. In particular, when the solar cell back surface sealing material is designed so that the resin layer in the present invention is located in the innermost layer, in the solar cell module manufacturing process, specifically in the glass laminating process (cell filling process), The resin layer is exposed to heat treatment at a high temperature of about 150 ° C. at the maximum, and in the case of a long period of time, it is particularly heat resistant so that the resin layer (coating film) does not show melting or flow in that environment. Required. In the present invention, since a hydroxyl group-containing fluororesin is used, it is possible to use a crosslinking agent capable of reacting with the hydroxyl group. Among them, a polyisocyanate resin is used as a curing agent to generate a urethane bond (crosslinked structure). Encouraging prescriptions are preferred. Examples of the polyisocyanate resin used as the cross-linking agent include aromatic polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Each of the following diisocyanate compounds is used as a raw material. Resin.

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

  Examples of the diisocyanate used as a raw material for the alicyclic polyisocyanate 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-or Examples include 1,4-bis (isocyanatomethyl) cyclohexane (hydrogenated XDI).

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

  As a raw material of polyisocyanate, these diisocyanates can be used in combination, or can be used as a modified body such as a burette modified body or a nurate modified body. Among them, as a polyisocyanate raw material, a resin containing an aromatic ring having a light absorption band in the ultraviolet region in the resin skeleton easily yellows upon irradiation with ultraviolet rays. Therefore, an alicyclic polyisocyanate and an aliphatic polyisocyanate. It is preferable to use a curing agent containing as a main component. Further, a nurate-modified product of hexamethylene diisocyanate is preferable from the viewpoint of easy progress of a crosslinking reaction with a hydroxyl group-containing fluororesin, a degree of crosslinking, heat resistance, ultraviolet resistance and the like.

[Other additives]
Further, the coating liquid containing the fluororesin according to the present invention includes a heat stabilizer, an antioxidant, a strengthening agent, a deterioration preventing agent, a weathering agent, a flame retardant, a plasticizer, a mold release, as long as the characteristics 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, 2- (2'-hydroxy-5) of benzotriazole series '-Methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H benzotriazol-2-yl) phenol], a cyanoacrylate-based ester Ru-2-cyano-3,3′-diphenyl acrylate), as others, and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy]- Examples thereof include phenol and the like, modified products, polymers, and derivatives 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) decanedioate , 6-tetramethyl-1-octyloxy] -4-piperidinyl] ester and the like, modified products, polymers and derivatives thereof.

[Combination of fluororesin and curing agent]
In the present invention, it is preferable to use a hydroxyl group-containing fluororesin that forms a bond with a crosslinking agent as the fluororesin that forms the easily adhesive resin layer. As described above, it is preferable to use an aliphatic or alicyclic polyisocyanate compound as the crosslinking agent. Usually, when a hydroxyl group-containing resin is crosslinked with a polyisocyanate compound to form a curable resin layer, an equivalent calculation is performed so that the number of hydroxyl groups is equal to the number of isocyanate groups, and the blending ratio is calculated. By doing so, the heat resistance, water resistance / solvent resistance, moist heat resistance and the like of the film cured through the crosslinking reaction are exhibited. However, as a result of diligent study in the present invention, the easy-adhesive resin layer having excellent adhesion to the sealing material layer by blending the polyisocyanate compound blended as a cross-linking agent rather than blending derived by equivalent calculation. Has been found to be possible to form. That is, it is a technique for improving the adhesion with the encapsulant layer by actively leaving uncrosslinked hydroxyl groups in the cured coating film. Usually, a polyisocyanate compound that undergoes a crosslinking reaction by a thermal load is blended as a kind of crosslinking agent in a sealing material layer (sheet) mainly composed of EVA resin. Therefore. When an uncrosslinked hydroxyl group remains in the easily adhesive resin layer formed on the outermost surface of the back surface sealing sheet, the polyisocyanate compound in the sealing material layer and the polyisocyanate compound at the time of thermocompression bonding with the sealing material layer The urethane bond formation reaction proceeds between them, a covalent bond can be formed between the sealing material layer and the back surface sealing sheet layer, and the interfacial adhesion is greatly improved. In accordance with this principle, the hydroxyl equivalent (A) in the fluororesin and the easy-adhesive resin are improved from the viewpoint of improving the adhesion of the easy-adhesive resin layer to the sealing material layer and not impairing the workability and blocking resistance. The ratio (A / B) of the isocyanate group equivalent (B) in the polyisocyanate resin in the layer is preferably a blending ratio of 10 to 10/7, and a particularly preferred range is a blending ratio of 5 to 10/6. . When the blending ratio is less than 10, the amount of unreacted hydroxyl groups increases so that the tackiness of the coating surface increases, which may easily cause blocking, and the hydrophilicity derived from hydroxyl groups is strong. This may cause problems such as insufficient water resistance and moisture and heat resistance of the coating film. On the other hand, when the crosslinking agent content is greater than 10/7, the number of unreacted hydroxyl groups in the easy-adhesive resin layer is reduced, and the crosslinking reaction with the crosslinking agent contained in the sealing material layer is reduced. Since the adhesive force between a sealing material layer and a back surface sealing sheet layer becomes inadequate, it is not preferable.

[Solar cell backside sealant]
A solar cell back surface sealing material can be obtained by laminating the solar cell back surface sealing sheet obtained by the present invention and another resin film. As a method of laminating, a known dry laminating method can be used. For bonding using the dry laminating method, a known adhesive for dry laminating using a polyether polyurethane, polyester polyurethane, polyester or polyepoxy resin as a main agent and a polyisocyanate resin as a curing agent is used. Can be used. However, the adhesive layer formed using these adhesives does not cause delamination due to deterioration of the adhesive strength after long-term outdoor use, and yellowing that leads to a decrease in light reflectance. It is necessary not to produce such. 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 curing agent), and further using the adhesive This is not preferable because the production cost increases due to an increase in the amount.

  As a material used for forming the adhesive layer, a known dry laminating adhesive can be used. In general, adhesives for dry laminating are prepared by diluting two resins, a main agent and a crosslinking agent, with a diluent solvent. However, the crosslinking agent is highly reactive with active hydroxyl groups, its reaction rate and initial adhesion. The prescription using an isocyanate group-containing polymer with a fast onset is preferred. In addition to these advantages, it is possible to form an adhesive resin layer that has high adhesive strength with the base film, and also has excellent constant temperature stability and long-term durability. Examples of the main resin used in combination with this isocyanate group-containing polymer include polyether resins, polyester resins, polyol resins, and other urethane resins and epoxy resins, depending on the detailed required characteristics and suitability for processing conditions. Can be appropriately selected and used. Further, depending on the configuration of the solar cell back surface sealing material, it is also conceivable that UV light reaches the above adhesive layer and induces photodegradation of the resin. From such a viewpoint, the resin used for forming the adhesive layer is preferably an aliphatic resin or an alicyclic resin that does not contain an aromatic ring or has a low content.

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

  In the present invention, the back surface sealing sheet for solar cells of the present invention includes a film having hydrolysis resistance, a white film, a film having an inorganic oxide vapor deposition, an outer layer side weather resistance / ultraviolet blocking resin layer (film, resin coating layer). Or the like) may be stacked to form a protective sheet for sealing the back surface of a solar cell that satisfies various required characteristics. Preferably, a weather resistant / ultraviolet blocking layer is laminated on the surface opposite to the easily adhesive resin layer of the base film of the back surface sealing sheet for solar cell. In particular, a film having hydrolysis resistance is used as a base film, and a hydrolysis resistance / weather resistance film in which a weather resistance / ultraviolet ray blocking resin layer is formed is laminated on the base film or the easy adhesion of the present invention. A design in which a weather resistant / ultraviolet blocking resin layer is directly laminated on the opposite surface of the base film on which the resin layer is formed is preferable.

[Weather-resistant / UV-blocking resin layer]
As the weather resistant / ultraviolet blocking resin layer, another resin layer containing an ultraviolet absorber is laminated. As the resin for forming the other resin 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 resins (ECTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resins (PFA), etc. As acrylic resins, polymethyl methacrylate, polyacrylate, acrylic resins obtained by crosslinking acrylic polyol resins using various crosslinking agents, 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.

  Next, as the ultraviolet absorber blended in these resins, an inorganic ultraviolet absorber or an organic ultraviolet absorber is used. 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, benzotriazole 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], shea Acrylate-based ethyl-2-cyano-3,3′-diphenylacrylate), as others, and 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) Examples thereof include oxy] -phenol and the like, modified products thereof, polymers and derivatives 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 stabilizer used in resin layer]
Similarly, examples of the light stabilizer preferably used for the 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) decanedioate , 6-tetramethyl-1-octyloxy] -4-piperidinyl] ester and the like, modified products, polymers and derivatives thereof.

  In the present invention, among the above descriptions, it is preferable to use an acrylic polyol resin in which a resin layer is copolymerized with an ultraviolet absorber and a light stabilizer. Further, it is more preferable to mix an acrylic polyol-based resin copolymerized with an ultraviolet absorber and a light stabilizer and an inorganic ultraviolet absorber to form a resin layer because the ultraviolet blocking performance is further improved.

[Other additives that can be used in the resin layer]
In addition, the weather resistance / ultraviolet blocking resin layer may contain additives such as antistatic agents, stabilizers, antioxidants, reinforcing agents, plasticizers, lubricants, fillers, coloring pigments, and the like as necessary. , And can be added within a range not impairing the effects of the present 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.

[Production method of resin layer]
Specific examples of other resin layers containing an ultraviolet absorber include the following films and coating layers. Examples of the film include a polyvinyl fluoride film, a polyvinylidene fluoride film, a polyethylene terephthalate film, a polyethylene film, and an ethylene-vinyl acetate film containing titanium oxide or carbon black. Examples thereof include a coating layer formed using a tetrafluoroethylene copolymer resin-containing paint containing titanium oxide or carbon black, and a paint containing an acrylic polyol resin and a polyisocyanate resin.

  Among them, as means for achieving both the manufacturing cost and the UV resistance of the back surface sealing sheet for solar cell modules, a tetrafluoroethylene copolymer resin-containing paint containing titanium oxide or carbon black, an acrylic polyol resin and a polyisocyanate resin are used. A coating layer formed by using a paint containing is preferable as the other resin layer.

  The method for laminating the above weather-resistant / ultraviolet-blocking resin layer is not particularly limited, but a melt-extrusion laminating method or a liquid paint containing other resins and additives is applied and cured by heat, light, electron beam or the like. Examples thereof include a coating method and a laminating method in which a film containing other resin or additive and an adhesive are used for bonding.

  For example, in the case of forming by a coating method, examples of the solvent for the coating solution include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, methanol, ethanol and Water and the like can be exemplified, and the property of the coating liquid may be either an emulsion type or a dissolution type.

  The method for forming the weather resistant / ultraviolet blocking resin layer on the base film 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 a preferable method for increasing the stability of the coating layer forming composition.

  In addition, a known dry laminating method can be used for a laminating method in which an adhesive is used to attach a film containing other resin or additive. For the lamination of resin films using the dry laminating method, polyether polyurethanes, polyester polyurethanes, polyesters, polyepoxy resins, etc. are the main ingredients, and known for dry laminates using polyisocyanate resins as curing agents. An adhesive can be used. However, the adhesive layer formed using these adhesives does not cause delamination due to deterioration of the adhesive strength after long-term outdoor use, and yellowing that leads to a decrease in light reflectance. It is necessary not to produce such. Moreover, as thickness of an adhesive bond layer, Preferably it is the range of 1-10 micrometers. 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 the adhesive force (promoting the crosslinking reaction between the main agent and the curing agent), and the use of the adhesive This is not preferable because the production cost increases due to an increase in the amount.

  As a material used for forming the adhesive layer according to the present invention, a known dry laminating adhesive can be used. In general, adhesives for dry laminating are prepared by diluting two resins, a main agent and a crosslinking agent, with a diluent solvent. However, the crosslinking agent is highly reactive with active hydroxyl groups, its reaction rate and initial adhesion. The prescription using an isocyanate group-containing polymer with a fast onset is preferred. In addition to these advantages, it is possible to form an adhesive resin layer that has high adhesive strength with the base film, and also has excellent constant temperature stability and long-term durability. Examples of the main resin used in combination with this isocyanate group-containing polymer include polyether resins, polyester resins, polyol resins, and other urethane resins and epoxy resins, depending on the detailed required characteristics and suitability for processing conditions. Can be appropriately selected and used. Further, depending on the configuration of the solar cell back surface sealing material, it is also conceivable that UV light reaches the above adhesive layer and induces photodegradation of the resin. From such a viewpoint, the resin used for forming the adhesive layer is preferably an aliphatic resin or an alicyclic resin that does not contain an aromatic ring or has a low content.

[Solar cell module]
When using the solar cell backside sealing sheet created as described above for a solar cell module, the easily adhesive resin layer of the solar cell backside sealing sheet is adhered to the silicon cell filler layer surface of the solar cell module, Install in the solar cell module.

  Next, an Example is given and the back surface sealing sheet for solar cells of this invention is demonstrated concretely. In the examples, “parts” means “parts by mass” unless otherwise specified.

<Evaluation method of characteristics>
The characteristic evaluation method used in the present invention is as follows.

(1) Measurement of coating amount The coating amount of the easy-adhesive resin layer was cut into an area of 500 cm ² after forming the coat layer, and the mass of the test piece was defined as mass (1). Next, the resin layer was dissolved in n-butyl acetate from the test piece, peeled off, and the mass of the test piece was measured again to obtain mass (2). Subsequently, the coating amount per unit area was calculated based on the following formula. This coating amount measurement was performed on three test pieces, and the average value was taken as the coating amount.
Application amount [g / m ² ] = {(mass (1)) − (mass (2))} × 20.

(2) Adhesive strength evaluation between base film / easy-adhesive resin layer About the adhesive force (coating film adhesive force) between the base film and the coating layer (resin layer) of the produced backside sealing sheet for solar cell, A cross-cut test was performed based on the method described in JIS K 5400 (1990 edition), and the following characteristics were classified.
○: 100 square coating film remaining / in 100 square Δ: 81-99 square coating film remaining / in 100 square ×: 80 mass or less coating residual / 100 square in.

(3) Measurement of adhesion strength with sealing material layer Based on JIS K 6854, the adhesive force with an EVA sheet was measured. The tested pseudo solar cell module sample is obtained by stacking an EVA sheet on the surface of the easily adhesive resin layer of the produced solar cell backside sealing sheet, and further superimposing a 0.3 mm thick semi-tempered glass thereon, and using a commercially available glass laminator. Then, after evacuation, press-treated for 15 minutes with a load of 29.4 N / cm ² at 135 ° C. was used. As the EVA sheet, a 500 μm thick sheet 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 40 N / 10 mm or more at a level where there was no practical problem.

(4) Ultraviolet resistance evaluation Using an I-super UV tester SUV-W151 manufactured by Iwasaki Electric Co., Ltd. in a 60 ° C. × 50% RH atmosphere at an ultraviolet intensity of 100 mW / cm ² for 144 hours from the glass surface side to the pseudo solar cell module. Or the ultraviolet irradiation was performed from the outer-layer surface (back surface sealing sheet) side. Thereafter, the color system b value was measured.

(5) Evaluation of Moisture and Heat Resistance Using a constant temperature and humidity oven manufactured by Espec, the pseudo solar cell module was subjected to a wet heat treatment for 2000 hours in an environment of 85 ° C. and 85% RH. Then, the adhesion strength measurement between a sealing material layer and a back surface sealing sheet was implemented for the purpose of the heat-and-moisture resistance evaluation of the characteristic.

(6) Blocking resistance test Ten test pieces having a size of 5 cm square were cut out from the solar cell back surface sealing sheet and overlapped in a direction in which the adhesive resin layer faces did not face each other (that is, adhesive resin layer / substrate film // adhesion). Resin layer / base polyester film) and an ink blocking tester, and a load of 5 kgf / cm 2 was applied and left in an environment of 40 ° C. for 1 week. 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.
(Adjustment of paints 1-5 for easy adhesion resin layer formation)
A coating agent “Zeffle” GK570 white (solid content concentration: 65 mass%) manufactured by Daikin Industries, Ltd. containing a hydroxyl group-containing tetrafluoroethylene copolymer resin and titanium oxide blended as an inorganic pigment is a nurate hexamethylene diisocyanate resin. A ratio of the number of hydroxyl groups in the hydroxyl group-containing tetrafluoroethylene copolymer resin to the number of isocyanate groups in the polyisocyanate resin is 1/100 for a certain Sumika Bayer-made Desmodule (registered trademark) N3300 (solid content concentration: 100% by mass). The pre-calculated diluent: n-butyl acetate was weighed in an amount of 15% by mass (resin solid content concentration). Easy-adhesive resin layer forming coating 1 having a solid content concentration of 30% by mass (resin solid content concentration) by stirring for 1 minute Got.

  Moreover, it prepared similarly by the compounding ratio shown in Table 1, and obtained the coating materials 2-5 for easily-adhesive resin layer formation.

(Adjustment of paint 1 for forming a weather-resistant coat layer)
Hals hybrid polymer (registered trademark) BK1 (solid content concentration), a coating agent manufactured by Nippon Shokubai Co., Ltd., characterized in that an ultraviolet absorber and a light stabilizer (HALS) are cross-linked to an acrylic polyol resin : 40% by mass), the color pigment and the solvent having the composition shown in Table 2 were mixed together and dispersed using a bead mill. Thereafter, a plasticizer having the composition shown in Table 2 was added to obtain a main coating material for forming a weather-resistant / ultraviolet blocking resin layer having a solid content concentration of 51% by mass.

  Next, Sum module Bayer's Desmodule (registered trademark) N3300 (solid content concentration: 100% by mass), which is a nurate-type hexamethylene diisocyanate resin, is added to the resin layer forming paint obtained by the above-described method. The pre-calculated diluent: n-propyl acetate was blended in such an amount that the mass ratio was 100/4, and the coating composition had a solid content concentration of 20% by mass (resin solid content concentration). Was measured and stirred for 15 minutes to obtain a light-resistant coating layer forming coating material 1 having a solid content concentration of 20% by mass (resin solid content concentration).

The following products were used as the color pigments and plasticizers used in the above adjustment.
White pigment: Titanium oxide particles JR-709 manufactured by Takeka
Plasticizer: DIC's polyester plasticizer Polysizer W-220EL
(Adjustment of adhesive for dry lamination)
Dry laminating agent having heat and moisture resistance manufactured by DIC Corporation, mainly composed of a resin containing a hydroxyl group in the structure as a reaction site with a curing agent, 36 parts of Dick Dry (registered trademark) TAF-300, hexamethylene as a curing agent 3 parts of TAF hardener AH-3 manufactured by DIC Corporation and 30 parts by weight of ethyl acetate, the main component of which is a diisocyanate resin, and stirred for 15 minutes, the solid content concentration is 30% by weight. Got. After laminating the film by the dry laminating method using the present adhesive, aging is performed as described in Examples and Comparative Examples, whereby a hydroxyl group and an isocyanate group undergo a crosslinking reaction to form a urethane bond.

(Example 1)
A hydrolysis-resistant polyethylene terephthalate film Lumirror (registered trademark) X10S (125 μm) having a cyclic trimer content of 1% by weight or less manufactured by Toray Industries, Inc. was prepared as a base film. One side of this base film is subjected to corona treatment, and further, an easy-adhesive resin layer-forming coating material 1 is applied using a wire bar, dried at 150 ° C. for 30 seconds, and the coating amount after drying is 1.0 g. An easily adhesive resin layer was provided so as to be / m ² . Thus, the solar cell back surface sealing sheet 1 was manufactured.

(Example 2)
A solar cell back surface sealing sheet 2 was produced in the same manner as in Example 1 except that an easy-adhesive resin layer was provided so that the coating amount after drying was 3.0 g / m ² .

(Example 3)
A solar cell backside sealing sheet 3 was produced in the same manner as in Example 2 except that the easy-adhesive resin layer-forming paint 2 was used instead of the easy-adhesive resin layer-forming paint 1.

Example 4
A solar cell back surface sealing sheet 4 was produced in the same manner as in Example 2 except that the easy-adhesive resin layer-forming coating material 3 was used instead of the easy-adhesive resin layer-forming coating material 1.

(Example 5)
The surface opposite to the easily adhesive resin layer of the solar cell backside sealing sheet 4 produced by the method described in Example 4 is subjected to corona treatment, and further a weather resistant coat layer forming coating 1 is formed using a wire bar. It was coated and dried at 150 ° C. for 30 seconds, and a weather-resistant coating layer was provided so that the coating amount after drying was 3.0 g / m ² . Thus, the solar cell back surface sealing sheet 5 was manufactured.

(Example 6)
An easy-adhesive resin layer was formed by the same method as described in Example 3 using Lumirror (registered trademark) E20F (50 μm), which is a white polyethylene terephthalate film manufactured by Toray Industries, Inc. In addition, a hydrolysis-resistant polyethylene terephthalate film Lumirror (registered trademark) X10S (125 μm) having a cyclic trimer content of 1% by weight or less manufactured by Toray Industries, Inc. was prepared as a base film. One side of this base film is subjected to corona treatment, and further applied with a weather-resistant coating layer forming coating 1 using a wire bar, dried at 150 ° C. for 30 seconds, and the coating amount after drying is 3.0 g / A weather-resistant coat layer was provided so as to be m ² . Next, apply the dry laminating adhesive to the surface of the white film on which the easy-adhesive resin layer has been formed on the side opposite to the surface on which the easy-adhesive resin layer has been formed using a wire bar, and dry at 80 ° C. for 45 seconds. Then, a dry laminate adhesive layer was formed so that the coating amount after drying was 5.0 g / m 2. Next, the surface opposite to the surface on which the weather-resistant coat layer is formed of the film prepared with the weather-resistant coat layer formed as described above is bonded to the adhesive layer surface, dry-laminated, and the solar cell back surface sealing sheet 6 is manufactured. did.

(Comparative Example 1)
Without forming an easily adhesive resin layer, Lumirror (registered trademark) X10S (manufactured by Toray Industries, Inc., 125 μm) is used as a solar cell back surface sealing sheet 7 as a comparative example.

(Comparative Example 2)
A solar cell back surface sealing sheet 8 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 easy-adhesive resin layer-forming coating material 1.

(Comparative Example 3)
A solar cell back surface sealing sheet 9 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 easy-adhesive resin layer-forming coating material 1.

(Comparison between Examples 1 to 5 and Comparative Example 1)
Since the solar cell back surface sealing sheet 7 obtained in Comparative Example 1 was not formed with an easy-adhesive resin layer, the adhesion with the EVA sheet used as the sealing material was very weak at 5 N / 10 mm. In addition, with the ultraviolet irradiation test from the glass surface side of the pseudo module, the polyethylene terephthalate film was photodegraded by the ultraviolet light transmitted through the glass and the sealing material layer, and yellowed. On the other hand, in the case of the solar cell backside sealing sheets 1 to 6 obtained in Examples 1 to 6, the easy-adhesive resin layer of the present invention causes a crosslinking reaction with the sealing material by heating in the vacuum laminating step, and firmly adheres to it. In either case, the adhesive strength was 40 N / 10 mm or more. In addition, even when an ultraviolet irradiation test is performed from the glass surface side of the pseudo module, the fluorine-based copolymer resin itself that forms the easy-adhesion resin layer has weather resistance, and is an oxidation pigment blended as an inorganic pigment. Since titanium absorbs ultraviolet rays, ultraviolet light does not reach the polyethylene terephthalate film layer, which is the base film, and as a result, the photodegradation reaction is suppressed, and thus changes such as yellowing were not observed.

(Comparison between Examples 1-5 and Comparative Example 2)
The solar cell backside sealing sheet 8 obtained in Comparative Example 2 is formed with an easily adhesive resin layer in which the hydroxyl group equivalent (A) in the fluorine-based copolymer resin and the isocyanate group equivalent (B) of the polyisocyanate resin are blended equally. Since the easy-adhesive resin layer was formed using the coating material 4, the cross-linking reaction did not occur with the sealing material layer, and the adhesion with the sealing material was as weak as 10 N / 10 mm. Furthermore, since a decrease in adhesion force is also seen in the wet heat resistance test, when exposed outdoors for a long period of time, in the extreme case, the situation where the back surface sealing sheet peels off from the sealing material layer is not preferable. . On the other hand, in the case of the solar cell backside sealing sheets 1 to 6 obtained in Examples 1 to 6, in order to cause a crosslinking reaction with the sealing material layer, the initial adhesion to the sealing material is 40 N / 10 mm. In addition to the above, it is considered that the decrease in adhesion due to the heat and humidity resistance test is small, and even when used outdoors for a long period of time, it is considered that good adhesion is maintained.

(Comparison between Examples 1 to 6 and Comparative Example 3)
In the solar cell back surface sealing sheet 9 obtained in Comparative Example 3, the hydroxyl group equivalent (A) in the fluorine-based copolymer resin and the isocyanate group equivalent (B) in the polyisocyanate resin are blended in a ratio of A / 0.1B. Since the easy-adhesive resin layer is formed using the easy-adhesive resin layer-forming coating material 5, a large amount of hydroxyl groups remain in the easy-adhesive resin layer without causing a crosslinking reaction with polyisocyanate. . Therefore, the adhesiveness of the coating film surface is high, sticking was seen between the base film and the easily adhesive resin layer in the blocking resistance test, and it was suggested that it is difficult to produce stably. In addition, the hydrophilicity of the coating film is relatively high due to the large number of residual hydroxyl groups, the wet heat resistance of the sealing material adhesion force is also inferior, and a decrease in adhesion force is seen with the wet heat test, so long-term When exposed to the outdoors, in an extreme case, a situation where the back surface sealing sheet peels off from the sealing material layer is not preferable. On the other hand, in the case of the solar cell backside sealing sheets 1 to 6 obtained in Examples 1 to 6, in order to cause a crosslinking reaction with the sealing material layer, the initial adhesion to the sealing material is 40 N / 10 mm. In addition to the above, it is considered that the decrease in adhesion due to the heat and humidity resistance test is small, and even when used outdoors for a long period of time, it is considered that good adhesion is maintained.

  The solar cell back surface sealing sheet of the present invention is excellent in adhesion to sealing material, storage stability, productivity and weather resistance, and is preferably used in a solar cell module. A stop sheet and a solar cell module using the same are useful.

Claims (6)

  The solar cell back surface sealing sheet using the base film in which the easily-adhesive resin layer containing a fluorine resin and an inorganic pigment was formed in the at least single side | surface.   The easily adhesive resin layer contains at least one polyisocyanate resin selected from the group consisting of aliphatic polyisocyanate resins, alicyclic polyisocyanate resins, and araliphatic polyisocyanate resins, and the fluororesin is tetrafluoro. The solar cell backside sealing sheet according to claim 1, wherein the solar cell backside sealing sheet is a copolymer resin containing a hydroxyl group-containing monomer as a crosslinking point between ethylene and an isocyanate group in a repeating structure.   The solar cell back surface sealing sheet of Claim 1 which has at least 1 layer of the weather-proof and ultraviolet-blocking resin layer containing a ultraviolet absorber on the opposite side to an easily-adhesive resin layer.   The solar cell backside sealing sheet according to claim 1, wherein the inorganic pigment comprises titanium oxide or carbon black.   The ratio A / B of the hydroxyl group equivalent (A) in the fluororesin and the isocyanate group equivalent (B) in the polyisocyanate resin in the easy-adhesive resin layer is a blend ratio of 10/1 to 10/7. The solar cell back surface sealing sheet of 1.   The solar cell module formed by adhere | attaching the easily adhesive resin layer of the solar cell backside sealing sheet of Claims 1-5, and the silicon cell filler layer surface of a solar cell module.