JP5692706B2 - Film for solar cell backside sealing sheet - Google Patents

Description

  The present invention relates to a film for solar cell backside sealing sheet having light resistance and moisture and heat resistance that can withstand use in a harsh outdoor environment for a long period of time. Moreover, this invention relates to the solar cell backside sealing sheet and solar cell module using the film for solar cell backside sealing sheets of this invention.

  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 has been urgently needed. For this reason, various methods such as nuclear power generation, hydroelectric power generation, wind power generation, and solar power generation have been studied and actually used. Solar power generation, which directly converts solar energy into electrical energy, has been put into practical use as a new semi-permanent and pollution-free new energy source. Photovoltaic power generation is remarkably improved in price / performance ratio when actually used, and is highly expected as a clean energy source.

  A solar cell used for photovoltaic power generation constitutes the heart of a photovoltaic power generation system that directly converts solar energy into electrical energy. Solar cells are made of semiconductors such as silicon. The solar cells are unitized by wiring various solar cell elements in series and in parallel and applying various packaging to protect the elements over a long period of about 20 years. The unit incorporated in this package is called a solar cell module. The solar cell module has a configuration in which a surface that is exposed to sunlight is covered with glass, a gap is filled with a filler made of a thermoplastic resin, and a back surface is protected with a sealing sheet. As this filler, 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, electrical insulation, water vapor barrier properties, and thermal adhesiveness with fillers typified by EVA resin. Further, characteristics such as design properties and adhesion to the outermost terminal box mounting silicone resin are required. In addition to these, the back surface sealing sheet is required to have excellent light resistance because it is exposed to ultraviolet rays.

  As a film for backside sealing sheets conventionally used, a white polyvinyl fluoride film (DuPont Co., Ltd., trade name: Tedlar (registered trademark)) can be exemplified. A backside sealing sheet having a laminated structure in which a polyester film is sandwiched with a polyvinyl fluoride film is widely used in solar cell applications. In addition, a light-resistant film in which an acrylic resin coating film containing an ultraviolet absorber and a light stabilizer is formed on one side or both sides of a polyester film has been proposed and put into practical use (Patent Document 1). In addition, a specification in which an ultraviolet absorber or a light stabilizer is kneaded into a polyester film has been proposed and put into practical use (Patent Document 2). A white film formed by kneading a white pigment such as titanium oxide in a layer such as a polyester film has also been put into practical use (Patent Document 3). This white film is known to have light resistance from the viewpoint that the change in the film appearance accompanying ultraviolet exposure is small.

JP 2005-015557 A JP 2009-188105 A Japanese Patent Laid-Open No. 11-291432

  However, the polyvinyl fluoride film is a film excellent in weather resistance, but has a low mechanical strength, and is softened by heat of a hot press at 140 to 150 ° C. applied at the time of manufacturing a solar cell module. The protrusion of the element electrode portion may penetrate the filler layer. Furthermore, since it is expensive, it also becomes an obstacle in terms of reducing the cost of the solar cell module. Moreover, in order to make it a colored film represented by white etc. and to improve the design property of a back surface sealing sheet, it is necessary to combine with a comparatively expensive colored film.

  Moreover, the polyester film of patent document 1 and patent document 2 may bleed out to a coating film or the film surface in a high temperature humidification environment or with ultraviolet light reception. For this reason, not only the wettability and the surface adhesion force change, but also the light resistance that was initially expressed is likely to be lost.

  Further, the white film of Patent Document 3 has a certain degree of UV resistance in that the change in film appearance accompanying UV exposure is small due to the light absorption ability of the pigment component, but the main material resin is not light-resistant. For this reason, for example, film properties represented by breaking strength and elongation are gradually lowered with ultraviolet irradiation. In addition, in recent years, development related to prolonging the life of solar cell modules itself has been actively carried out, and in addition, the number of solar cell modules installed in a slanting manner on the ground surface is increasing mainly in Europe. In such a case, it is exposed to ultraviolet rays reflected from the ground surface for a long time. Therefore, when a layer having stable light resistance over a long period of time is not formed on the outer layer surface of the back surface sealing sheet, the sealing sheet turns yellow, and not only the beauty of the film appearance is impaired, but also the extreme In such a case, cracks and the like are generated in the sealing sheet, and there is a concern that various characteristics required for the sheet such as electrical insulation and water vapor barrier properties may be impaired.

  In order to solve such a problem, the present invention employs the following configuration. That is, in the film for solar cell backside sealing sheet of the present invention, a resin layer containing a fluororesin, a color pigment, and melamine cyanurate is laminated on at least one side of the base film.

  Moreover, the solar cell back surface sealing sheet of this invention contains the film for solar cell back surface sealing sheets of this invention.

  Moreover, the solar cell module of this invention contains the solar cell backside sealing sheet and cell filler layer of this invention, and the solar cell backside sealing sheet and cell filler layer are adhere | attached.

  According to this invention, the film for solar cell backside sealing sheets excellent in light resistance and heat-and-moisture resistance, and a solar cell backside sealing sheet using the same are obtained. Moreover, according to the preferable aspect of this invention, the film for solar cell backside sealing sheets which are further excellent in a flame retardance and have little blocking and choking, and a solar cell backside sealing sheet using the same are obtained. Moreover, if the solar cell back surface sealing sheet of this invention is used, the solar cell module excellent in durability will be obtained.

  The film for solar cell backside sealing sheet of the present invention has a light resistance superior to that of the prior art by laminating a resin layer containing a fluororesin, a color pigment and melamine cyanurate on at least one surface of the base film. Moisture and heat resistance can be obtained.

[Base film]
Various resin films can be used as the base film for the film for solar cell backside sealing sheet. 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 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 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. Furthermore, polyphenylene sulfide (PPS) having high hydrolysis resistance, heat resistance and flame retardancy can also be used. Moreover, it is also possible to use the fluorine-type film represented by the polyvinyl fluoride conventionally used as a film for sheet | seats for back surface sealing.

  Since the film for solar cell backside sealing sheet is excellent in light resistance, it should be suitably used for the outermost layer that is directly exposed to the outside air (humidity, temperature) or reflected from the ground surface in the solar cell backside sealing sheet configuration. Can do. From the viewpoint of using the outermost layer that is directly exposed to the outside air, the base film is preferably a resin film having excellent hydrolysis resistance. Usually, a polyester resin film is formed from a so-called polymer obtained by condensation polymerization of monomers, 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, by forming a polyester resin film 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 as a raw material, under high temperature and high humidity It is possible to suppress the hydrolysis of the film, 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 mass) relative to the resin mass by measuring by liquid chromatography using a solution obtained by dissolving 100 mg of a polymer in 2 ml of orthochlorophenol. Is required.

  In the base film, if necessary, additives such as an antistatic agent, an ultraviolet absorber, a stabilizer, an antioxidant, a plasticizer, a lubricant, a filler, and a coloring pigment are added in a range that does not impair the effects of the present invention. Can be added within.

  The thickness of the base film is not particularly limited, but is preferably in the range of 1 to 250 μm in consideration of the withstand voltage characteristics and cost of the sealing sheet. The lower limit of the thickness is more preferably 25 μm or more.

For the base film, a water vapor barrier film in which at least one inorganic oxide layer is formed by vapor deposition or the like may be used 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). 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. It is about 10-30 micrometers.

  The base film is preferably stretched in the biaxial direction so that the thermal dimensional stability is good. Moreover, you may perform surface treatments, such as discharge treatments, such as corona discharge and plasma discharge, or acid treatment, to a base film as needed.

[Resin layer]
The resin layer laminated | stacked on the base film in this invention contains (1) fluororesin, (2) a coloring pigment, and (3) melamine cyanurate. 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 later adding a UV absorber or a light stabilizer to the binder resin, the UV absorber or light stabilizer is applied from the inside of the coating film in a high-temperature humidified environment or with UV light reception. May bleed out to the membrane surface. For this reason, not only the wettability and the adhesion of the coating film surface change, but also the problem that the ultraviolet ray cutting performance that was initially expressed is lost is likely to occur. On the other hand, in the present invention, a fluororesin that is extremely excellent in light resistance is used as a binder resin as compared with a polyester resin, an olefin resin, an acrylic resin, and the like. Therefore, it is not necessary to add an ultraviolet absorber or a light stabilizer to the binder resin later, and the above problems do not occur. 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. Further, in order to improve the adhesion to the base film or to improve the heat resistance of the resin layer, a fluororesin having a curable functional group introduced is preferable so that an appropriate cross-linked structure can be introduced into the resin layer. Since the solar cell backside sealing sheet using the solar cell backside sealing sheet film is exposed to high temperature treatment in the solar cell module manufacturing process, the resin layer is required to have heat resistance.

  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.

  The thickness of the resin layer is preferably 0.2 to 20 μm. The lower limit of the thickness of the resin layer is more preferably 5 μm or more, and particularly preferably 8 μm or more. The upper limit of the thickness of the resin layer is more preferably 15 μm or less, and particularly preferably 10 μm or less. When the 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 becomes difficult to form a uniform coating film. Therefore, the adhesion strength to the substrate film, and above all, light resistance may not be sufficiently exhibited. On the other hand, when the thickness of the resin layer exceeds 20 μm, the light 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 by the coating method include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dimethylformamide, dimethylacetamide, methanol, ethanol and water. Etc. can be illustrated. 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. Various methods can be applied as the coating method, and a roll coating method, a dip coating method, a bar coating method, a die coating method, a gravure roll coating method, and the like, or a combination of these methods can be used. Among them, the gravure roll coating method is a preferable method because it increases the stability of the resin layer.

[Coloring pigments]
The color pigment used in the present invention is used for the purposes of (1) coloring the resin layer, (2) maintaining the color tone (not fading), (3) cutting ultraviolet rays and / or visible light, and (4) improving flame retardancy. It is done. As the back surface sealing sheet for solar cells, a white sheet is mainly used from the viewpoint of light reflectivity and design, but in recent years, the design is superior to the sheet in which the gap between the power generation elements looks white. For this reason, the demand for black sheets is increasing. Further, since these pigments themselves also absorb and / or reflect light having a specific wavelength, the effect of protecting the substrate film from ultraviolet rays and / or visible light can be obtained by coloring. 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 coloring pigment, various coloring pigments such as inorganic pigments and organic pigments can be used. Regarding white or black currently in practical use, titanium oxide is preferred as the white pigment and carbon black is preferred as the black pigment from the viewpoints of versatility, price, color development performance, and UV resistance. In particular, from the viewpoint of color development, the number average particle diameter of titanium oxide is preferably 0.1 to 1.0 μm. From the viewpoint of dispersibility with respect to the fluororesin and cost, it is more preferably 0.2 to 0.5 μm. Similarly, for carbon black, the number average particle diameter is preferably 0.01 to 0.5 μm. From the viewpoint of dispersibility and cost, it is more preferably 0.02 to 0.1 μm.

  The content of the color pigment may be appropriately adjusted according to the design of the color tone to be developed. However, when the content of the color pigment is too small, a color appearance with excellent design properties cannot be obtained, the ultraviolet and / or visible light cutting performance is poor, or the base film when exposed to the outdoors for a long time. Degradation and yellowing may occur. Moreover, since the amount of resin increases, blocking may occur. On the contrary, if the content of the color pigment is too much, the cost becomes high, or the adhesion strength between the base material and the silicone resin for terminal box adhesion due to the significant improvement in the hardness of the resin layer is likely to occur. There is a concern that choking occurs on the surface of the resin layer. Moreover, since the amount of resin decreases, the adhesive force between the resin layer and the substrate film may be reduced. In this invention, the coloring pigment is used also for the purpose of improving the flame retardance of the film for solar cell backside sealing sheets, and flame retardance is provided by increasing content to some extent.

  For the above reason, the content of the color pigment is preferably 30 to 80% by mass with respect to the entire resin layer. The lower limit of the content is more preferably 50% by mass or more, and particularly preferably 65% by mass or more. The upper limit of the content is more preferably 75% by mass or less, and particularly preferably 70% by mass or less.

[Melamine cyanurate]
The melamine cyanurate used in the present invention is used for the purpose of (1) improving the blocking resistance of the resin layer and (2) improving the flame retardancy. Melamine cyanurate is a non-halogen flame retardant and is also used as a lubricant. In the present invention, by adding melamine cyanurate to the fluororesin, not only the flame retardancy of the resin layer is improved, but also there is an effect of reducing blocking that occurs when the fluororesin is used. As a mechanism for reducing blocking by including melamine cyanurate in the fluororesin, it is estimated as follows. When the resin layer is applied to the base film and dried by heating, the melamine cyanurate is phase-separated from the fluororesin having a low polarity in the resin layer, and the low molecular weight melamine cyanurate moves to the opposite side of the base film. Moving. As a result, since a large amount of melamine cyanurate is contained on the surface of the resin layer, it is considered that blocking is reduced.

  As for content of a melamine cyanurate, 1-30 mass% is preferable with respect to the whole resin layer. The lower limit of the content is more preferably 3% by mass or more, and particularly preferably 5% by mass or more. The upper limit of the content is preferably 20% by mass or less, and particularly preferably 10% by mass or less. If the content is less than 1% by mass, sufficient effects of melamine cyanurate may not be obtained. If the content exceeds 30% by mass, the cost may increase, the melamine cyanurate may bleed out to the surface of the coating film, and the solvent resistance required for the resin layer may decrease.

[Crosslinking agent]
Further, as described above, a crosslinking agent having a functional group capable of reacting with the functional group of the fluororesin may be blended for the purpose of improving the characteristics of the resin layer.
When a cross-linking agent is used in combination, the effect of improving the adhesion between the base film and the resin layer, or improving the solvent resistance and heat resistance of the resin layer accompanying the introduction of the cross-linked structure can be obtained. In particular, when the solar cell back surface sealing sheet is designed so that the resin layer in the present invention is located in the outermost layer, in the solar cell module manufacturing process, specifically in the glass laminating process (cell filling process), Since the resin layer is exposed to a heat treatment of 30 minutes or longer at a high temperature of about 150 ° C. at the maximum, heat resistance is particularly required. Moreover, in the manufacturing process of a solar cell module, since there is a wiping operation with ethanol or other organic solvent as a cleaning operation after the module is assembled, solvent resistance is required. From the viewpoint of improving the adhesion, solvent resistance, and heat resistance, it is preferable to add a crosslinking agent.

  As described above, a hydroxyl group is preferable as the functional group to be introduced into the fluororesin, and therefore a crosslinking agent capable of reacting with the hydroxyl group is preferably used. As such a crosslinking agent, a prescription that uses a polyisocyanate resin as a curing agent and promotes the formation of a urethane bond (crosslinked structure) is preferable. 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. These may be used alone or in combination of two or more.

  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) 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 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 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 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. 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 / or an aliphatic polyisocyanate is used as a curing agent. It is preferable. Furthermore, it is preferable to use an alicyclic polyisocyanate in which the resin layer is further cured from the viewpoint of solvent resistance. Further, a nurate-modified product of hexamethylene diisocyanate is preferable from the viewpoint of easy progress of a crosslinking reaction with a fluororesin, a degree of crosslinking, heat resistance, ultraviolet resistance, and the like.

[Other additives]
Furthermore, in the resin layer containing a fluorine-based resin, as long as the characteristics are not impaired, a thermal stabilizer, an antioxidant, a reinforcing agent, a deterioration preventing agent, a weathering agent, a flame retardant, a plasticizer, a release agent, a lubricant, A crosslinking aid, pigment dispersant, antifoaming agent, leveling agent, ultraviolet absorber, light stabilizer, thickener, adhesion improver, delustering agent, 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.

[Adhesive layer]
A solar cell back surface sealing sheet is obtained by laminating a film for solar cell back surface sealing sheet and another resin film. A known dry laminating method can be used as a method of laminating films and processing into a sheet. 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 1-5 micrometers. If the thickness is less than 1 μm, sufficient adhesive strength may not be obtained. 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 strength (promoting the crosslinking reaction between the main agent and the curing agent), and the use of the adhesive Production costs may increase due to increased volume.

  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 cross-linking agent, with a diluting solvent. However, the cross-linking 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 high-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 sheet, it is also conceivable that ultraviolet rays reach the above adhesive layer and induce 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 backside sealing sheet]
The solar cell back surface sealing sheet using the film for solar cell back surface sealing sheet is demonstrated. The solar cell 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 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.

  The film for solar cell backside sealing sheet of the present invention is different from the substrate film among the film having hydrolysis resistance, the white film, the film having inorganic oxide deposition, and the film having thermal adhesiveness with EVA. By laminating one or more films, a solar cell back surface sealing sheet satisfying various required characteristics can be obtained. In particular, the portion of the solar cell backside sealing sheet that becomes the outer side when incorporated in the solar cell module is a hydrolysis-resistant film as a base film, and this base film is used for a solar cell backside sealing sheet. The form which laminates | stacks a film is preferable. By disposing a film having hydrolysis resistance, layers (adhesive layer, film layer, etc.) located on the inner layer side from the film are protected from hydrolysis. In addition, since a resin layer having ultraviolet ray and / or visible light cutting performance and flame retardancy is located on the outermost layer side, the layer inside the resin layer is protected from ultraviolet rays and / or visible light, and further spreads in the event of a fire. Can be reduced.

  Meanwhile, one or more of a white film, a film having an inorganic oxide vapor deposition, and a film having thermal adhesiveness with EVA are laminated on the surface opposite to the surface on which the resin layer of the base film is laminated. Is preferred. When a white film is laminated, light reflectivity is imparted, when a film having an inorganic oxide vapor deposition layer is laminated, water vapor barrier property is imparted, and when a film having thermal adhesiveness with EVA is laminated Is provided with adhesion to the cell filler layer. Examples of the film having thermal adhesiveness with EVA include olefinic films such as EVA film and polyethylene film. Moreover, the film laminated | stacked on the film for solar cell backside sealing sheets of this invention does not necessarily need to be one sheet, According to the characteristic to give, combine each member film suitably and design a solar cell backside sealing sheet. It ’s fine.

  In addition, in the configuration of the solar cell backside sealing sheet, a vapor deposition layer, a sputter layer, a wet coating layer, etc. for the purpose of imparting functionality are formed on any layer as long as it is a portion other than the resin layer in the present invention. May be.

  The following method is mentioned as an example of the manufacturing method of the film for solar cell backside sealing sheets. As a base film, for example, a hydrolysis-resistant polyethylene terephthalate film Lumirror (registered trademark) X10S manufactured by Toray Industries, Inc. is prepared. And the coating agent which mixed the main ingredient which disperse | distributed and prepared the fluorine-type resin, the color pigment, and the melamine cyanurate using the bead mill machine, the nurate-type hexamethylene diisocyanate resin which is a crosslinking agent, and a solvent is prepared. The film for solar cell backside sealing sheets can be obtained by coating this coating material on a base film using a gravure roll coating method. Further, the solar cell backside sealing sheet is a white film, a film having an inorganic oxide vapor deposition layer on the surface opposite to the side where the resin layer of the film for solar cell backside sealing sheet is laminated, and the heat of EVA. It can be obtained by laminating at least one film selected from the group consisting of adhesive films using a dry laminating method.

  When using the solar cell backside sealing sheet of the present invention for a solar cell module, the solar cell backside sealing sheet and the cell filler layer are made so that the resin layer of the solar cell backside sealing sheet faces the outside of the solar cell module. And are assembled into a solar cell module.

  Next, an Example is given and the film for solar cell backside sealing sheets of this invention and a solar cell backside sealing sheet using the same are demonstrated concretely.

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

(1) Measurement of application amount of resin layer After the resin layer was formed, the film for solar cell backside sealing sheet was cut into an area of 500 cm ² , and the mass of the test piece was defined as mass (1) [g]. Next, the resin layer was dissolved in methyl ethyl ketone and peeled off from the test piece, and the mass of the test piece was measured again to obtain mass (2) [g]. Subsequently, the coating amount of the resin layer 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) Solvent resistance evaluation of resin layer The sample was immersed in ethanol for 5 minutes and then rubbed 50 times using a Kimwipe. Then, the state of the coating film was observed and classified as follows.
A: There is no change in the state of the coating film before treatment.
B: Peeling of a base material and a coating film is seen.

(3) Evaluation of UV protection performance (spectral spectrum measurement)
Based on JIS K 7105 (2006 edition), the spectrum was measured. As a measuring device, an ultraviolet-visible near-infrared spectrophotometer UV-3150 manufactured by Shimadzu Corporation was used. The ultraviolet cut performance of the film for solar cell backside sealing sheet was evaluated by measuring the light transmittance at a wavelength of 360 nm.

(4) Adhesive strength evaluation between base film / resin layer JIS K 5400 (1990 edition) for the adhesive force (coating strength) between the base film and the resin layer of the produced solar cell backside sealing sheet film The crosscut test was carried out based on the method described in (1). The results were classified as follows:
AA: 100 square coating film remaining / in 100 square A: 81-99 square coating film remaining / 100 square in B: 80 square or less coating residual / in 100 square.

(5) Ultraviolet resistance evaluation Ultraviolet irradiation (ultraviolet irradiation accumulated amount 384 kWh / m ² ) was performed for 240 hours at an ultraviolet intensity of 160 mW / cm ² in an atmosphere of 60 ° C. × 50% RH. The test apparatus used was an Isuper UV tester SUV-W151 manufactured by Iwasaki Electric Co., Ltd. The color system b value before and after the ultraviolet irradiation was measured, and the Δb value was determined by the following formula.
Δb = (b value after ultraviolet irradiation) − (b value before ultraviolet irradiation)
In addition, for “(3) Evaluation of UV cut performance” and “(4) Evaluation of adhesion strength between base film / resin layer”, UV irradiation was performed in the same manner for the purpose of evaluating UV resistance of those characteristics. Before and after evaluation.

(6) Evaluation of wet heat resistance A film for solar cell backside sealing sheet was subjected to a heat treatment of 48 hours in an environment of 120 ° C. and 100% RH. The test apparatus used was a pressure cooker TPS-211 manufactured by Espec. After that, "(3) Evaluation of UV-cutting performance" and "(4) Evaluation of adhesion strength between base film / resin layer" of the film for solar cell backside sealing sheet were carried out for the purpose of evaluating the heat and moisture resistance of those properties. did.

(7) Flame Retardancy Evaluation Based on the UL94 standard (2010 edition) horizontal flammability HB test, tests were conducted and classified into the following categories.
A: HB test passed B: HB test failed.

(8) Evaluation of blocking resistance Ten films each having a resin layer formed thereon were cut into 5 cm square. These were overlapped so that the resin layer surface of the film and the base film surface of the other film overlapped. Then, aging was performed for 3 days in a 40 ° C. environment under a load of 5 kg / cm ^{2 using} an ink blocking tester DG-BT manufactured by DG Engineering Co., Ltd. Thereafter, the degree of adhesion between the resin layer and the base film was evaluated and classified as follows.
A: The resin layer and the base film are not attached. B: The resin layer and the base film are attached.

(9) Chalking resistance evaluation The film on which the resin layer was formed was aged for 3 days in an environment of 40 ° C. The surface of the resin layer after aging was observed and classified as follows.
A: Choking is not generated on the surface of the resin layer. B: Choking is generated on the surface of the resin layer.

(10) Measurement of adhesive strength with filler (EVA adhesion)
The EVA sheet was stacked on the inner layer side (the surface opposite to the surface on which the resin layer of the base film was laminated) of the solar cell back surface sealing sheet, and a 3 mm thick semi-tempered glass was further stacked thereon. Next, a vacuum was drawn using a commercially available glass laminator, and press treatment was performed for 15 minutes under a heating condition of 135 ° C. under a load of 3 kgf / cm ² to produce a pseudo solar cell module sample. As the EVA sheet, a 500 μm thick sheet manufactured by Sanvik Co., Ltd. was used.
Using this pseudo solar cell module sample, the adhesive force with the EVA sheet was measured based on JIS K 6854-2 (1999 edition). The width of the test piece for the adhesive strength test was 10 mm, and each of the two test pieces was measured once. The average value of the two measured values was used as the adhesive strength value. Judging that the adhesive strength is 100 N / 50 mm or more is a practically acceptable level.

(11) Light reflectance A pseudo solar cell module sample was prepared in the same manner as in the above item (10). Light was incident from the glass side of the pseudo solar cell module sample, and the light reflectance was measured on the inner layer side (the surface opposite to the surface on which the resin layer of the base film was laminated) of the back surface sealing sheet. As a measured value of reflectance, the reflectance at a wavelength of 600 nm was used as a representative. As a measuring device, a spectrophotometer MPC-3100 manufactured by Shimadzu Corporation was used.

(12) Measurement of water vapor transmission rate Water vapor transmission rate was measured based on the method B (infrared sensor method) described in JIS K7129 (2000 version) under conditions of a temperature of 40 ° C and a humidity of 90% RH. The measuring device used was Permatran (registered trademark) W3 / 31, a water vapor transmission rate measuring device manufactured by MOCON, USA. Each of the two test pieces was measured once, and the average value of the two measured values was used as the water vapor transmission rate.

(Preparation of resin layer forming paint 1)
As the fluorine-based resin, Zaffle (registered trademark) GK570 (solid content concentration: 65% by mass), which is a coating agent for a hydroxyl group-containing TFE-based resin, manufactured by Daikin Industries, Ltd. was prepared. A fluororesin, a color pigment, melamine cyanurate, and a solvent were mixed together at the blending amounts shown in Table 1, and dispersed using a bead mill, to obtain a main coating material having a solid content concentration of 50% by mass. The following products were used as the color pigments.
-White pigment: Titanium oxide particles JR-709 manufactured by Takeka
Black pigment: Carbon black particles Special black 4A manufactured by Degussa
Desmodur (registered trademark) N3300 (solid content concentration: 100% by mass) manufactured by Sumika Bayer Co., Ltd., which is a nurate type hexamethylene diisocyanate resin, was added to the main material paint. It mix | blended so that it might become mass ratio. Further, a diluent: n-propyl acetate was added so as to obtain a coating material having a solid content concentration of 40% by mass (resin solid content concentration) and stirred for 15 minutes. Thus, a resin layer forming coating material 1 having a solid content concentration of 40% by mass (resin solid content concentration) was obtained.

(Preparation of resin layer forming coating 2)
Except for the blending amounts shown in Table 1 such that the content of the color pigment with respect to the resin solid content is 80% by mass and the content of melamine cyanurate is 1% by mass, it is the same as the preparation of the resin layer-forming coating material 1 The coating material 2 for resin layer formation was obtained by the method.

(Preparation of paint 3 for resin layer formation)
Except for the blending amounts shown in Table 1 so that the content of the color pigment with respect to the resin solid content is 30% by mass and the content of melamine cyanurate is 30% by mass, the same as the preparation of the resin layer forming paint 1 The coating material 3 for resin layer formation was obtained by the method.

(Preparation of paint 4 for resin layer formation)
Except for the blending amounts shown in Table 1 so that the content of the color pigment with respect to the resin solid content is 85% by mass and the content of melamine cyanurate is 1% by mass, the same as the preparation of the paint 1 for resin layer formation The coating material 4 for resin layer formation was obtained by the method.

(Preparation of resin layer forming coating 5)
Except for the blending amounts shown in Table 1 such that the content of the color pigment with respect to the resin solid content is 20% by mass and the content of melamine cyanurate is 30% by mass, the same as the preparation of the resin layer forming coating material 1 The coating material 5 for resin layer formation was obtained by the method.

(Preparation of paint 6 for resin layer formation)
Except for the blending amounts shown in Table 1 so that the content of the color pigment with respect to the resin solid content is 30% by mass and the content of melamine cyanurate is 40% by mass, the same as the preparation of the resin layer forming coating material 1 The coating material 6 for resin layer formation was obtained by the method.

(Preparation of paint 7 for resin layer formation)
The preparation of the resin layer-forming coating material 1 except that the blending amount shown in Table 1 is such that the content of the color pigment with respect to the resin solid content is 80% by mass and the content of melamine cyanurate is 0.5% by mass. Resin layer forming paint 7 was obtained in the same manner.

(Preparation of paint 8 for resin layer formation)
Resin layer-forming coating material, except for using DeSmodur (registered trademark) N3200 (solid content concentration: 100% by mass) manufactured by Sumika Bayer, which is a burette type hexamethylene diisocyanate resin, instead of the nurate type hexamethylene diisocyanate resin. A resin layer forming coating 8 was obtained in the same manner as in the preparation of 1.

(Preparation of resin layer forming paint 9)
Instead of using Zaffle (registered trademark) GK570 (solid content concentration: 65% by mass), which is a coating agent for a hydroxyl group-containing TFE resin, manufactured by Daikin Industries, Ltd., methyl methacrylic acid and 2-hydroxyethyl methacrylate are used as raw materials. The resin layer is formed in the same manner as the preparation of the resin layer-forming coating material 1 except that a resin (solid content concentration: 40% by mass) in which an ultraviolet absorber and a light stabilizer (HALS) are added to the acrylic resin to be used is used. A paint 9 was obtained.

(Preparation of paint 10 for resin layer formation)
A resin layer-forming coating material 10 was obtained in the same manner as in the preparation of the resin layer-forming coating material 1 except that the coloring pigments were not blended and the amounts shown in Table 1 were used.

(Preparation of paint 11 for resin layer formation)
Resin layer-forming coating material 11 was obtained in the same manner as in the preparation of resin layer-forming coating material 1 except that melamine cyanurate was not blended and the blending amount shown in Table 1 was used.

(Preparation of adhesive for dry lamination)
16 parts by mass of Dick Dry (registered trademark) LX-903 manufactured by DIC Corporation, 2 parts by mass of KL-75 manufactured by Dainippon Ink & Chemicals, Inc. as a curing agent, and 29.5 masses of ethyl acetate A portion was weighed and stirred for 15 minutes. Thus, an adhesive for dry lamination having a solid content concentration of 20% by mass was obtained.

(Preparation of paint for adhesive layer formation)
Takenate (registered trademark) A, which is an aromatic polyisocyanate resin made by Mitsui Chemicals Polyurethane Co., Ltd., 12 parts by mass of dry laminating agent Takelac (registered trademark) A-310 (polyester polyurethane resin) 1 part by weight of -3 and 212 parts by weight of ethyl acetate were weighed and stirred for 15 minutes. Thus, an adhesive layer-forming coating material having a solid content concentration of 3% by mass was obtained.

(Preparation of thermal adhesive resin layer coating)
20 parts by weight of Aquatex (registered trademark) MC-3800, an aqueous emulsion paint containing EVA terpolymer resin manufactured by Chuo Rika Kogyo Co., Ltd., 10.8 parts by weight of isopropyl alcohol, and 22.6 parts of water A part by weight was weighed and stirred for 15 minutes. Thus, a heat-adhesive resin layer-forming coating material having a solid content concentration of 15% by mass was obtained.

Example 1
A hydrolysis-resistant polyethylene terephthalate film Lumirror (registered trademark) X10S (125 μm) having a cyclic trimer content of 1% by mass or less was prepared as a base film. On one surface of the base film, the resin layer-forming paint 1 was applied using a wire bar, dried at 150 ° C. for 60 seconds, and a resin layer having a coating amount of 15.0 g / m ² after drying was provided. . Thus, the film 1 for solar cell backside sealing sheets was manufactured.

(Example 2)
A solar cell backside sealing sheet film 2 was produced in the same manner as in Example 1 except that the resin layer forming paint 2 was applied instead of the resin layer forming paint 1.

(Example 3)
A solar cell backside sealing sheet film 3 was produced in the same manner as described in Example 1 except that the resin layer forming paint 3 was applied instead of the resin layer forming paint 1.

Example 4
A solar cell backside sealing sheet film 4 was produced in the same manner as in Example 1 except that the resin layer forming paint 4 was applied instead of the resin layer forming paint 1.

(Example 5)
A solar cell backside sealing sheet film 5 was produced in the same manner as described in Example 1, except that the resin layer forming paint 5 was applied instead of the resin layer forming paint 1.

(Example 6)
A solar cell backside sealing sheet film 6 was produced in the same manner as described in Example 1, except that the resin layer forming paint 6 was applied instead of the resin layer forming paint 1.

(Example 7)
A solar cell backside sealing sheet film 7 was produced in the same manner as in Example 1 except that the resin layer forming paint 7 was applied instead of the resin layer forming paint 1.

(Example 8)
A solar cell backside sealing sheet film 8 was produced in the same manner as described in Example 1, except that the resin layer forming paint 8 was applied instead of the resin layer forming paint 1.

(Comparative Example 1)
A solar cell backside sealing sheet film 9 was produced in the same manner as in Example 1 except that the resin layer forming paint 9 was applied instead of the resin layer forming paint 1.

(Comparative Example 2)
A solar cell backside sealing sheet film 10 was produced in the same manner as in Example 1 except that the resin layer forming paint 10 was applied instead of the resin layer forming paint 1.

(Comparative Example 3)
A solar cell backside sealing sheet film 11 was produced in the same manner as in Example 1 except that the resin layer forming paint 11 was applied instead of the resin layer forming paint 1.

(Comparative Example 4)
Lumirror (registered trademark) X10S (manufactured by Toray Industries, Inc., 125 μm) was used as the solar cell back surface sealing sheet film 12 without forming a resin layer.

  Using the films for solar cell backside sealing sheets of Examples 1 to 8 and Comparative Examples 1 to 4 obtained above, the characteristics were evaluated by the above evaluation method. The results are shown in Tables 2 and 3.

(Evaluation of Examples 1-8)
Films 1-8 for solar cell backside sealing sheets of Examples 1-8 are all UV resistant (Δb value), coating adhesion after wet heat test and after UV irradiation, after wet heat test and after UV irradiation. The UV-cutting performance was excellent.

(Evaluation of Examples 1 to 3)
Especially the films 1-3 for solar cell backside sealing sheets of Examples 1-3 are the range whose content of the color pigment in a resin layer is 30-80 mass%, and content of melamine cyanurate is 1-30 mass%. It was excellent in flame retardancy, blocking resistance, choking resistance and solvent resistance. In addition, the tendency for the coating-film adhesive force after a moist-heat test to fall by the reduction | decrease of the resin amount or hardening of a coating film was seen, so that content of a color pigment approached 80 mass%. In addition, as the content of the coloring pigment approached 30% by mass, an increase in the Δb value of the base film due to a decrease in the UV cut performance, that is, a tendency that the b value of the base film after UV irradiation increased was observed. .

(Evaluation of Examples 4 and 5)
The film for solar cell backside sealing sheet 4 of Example 4 contained 85% by mass of the color pigment in the resin layer, and since the amount of the color pigment was large, choking was observed on the surface of the resin layer. Moreover, since the amount of the resin component in the resin layer was small, the adhesion of the coating film after the wet heat test was slightly reduced.
Since the film 5 for solar cell backside sealing sheet | seats of Example 5 has few coloring pigments in a resin layer as 20 mass%, the flame retardance worsened compared with Examples 1-3. Moreover, since the amount of the resin component in the resin layer was as large as 50% by mass, blocking occurred.

(Evaluation of Examples 6 and 7)
Since the film 6 for solar cell backside sealing sheets of Example 6 contains 40 mass% of melamine cyanurate in a resin layer and there is much quantity of melamine cyanurate, solvent resistance is bad compared with Examples 1-3. became.
Since the film 7 for solar cell backside sealing sheets of Example 7 had few melamine cyanurates in a resin layer as 0.5 mass%, blocking generate | occur | produced. Moreover, since the amount of the resin component in the resin layer was small, the adhesion of the coating film after the wet heat test was slightly reduced.

(Evaluation of Example 8)
The film 8 for solar cell backside sealing sheet of Example 8 has changed the hexamethylene diisocyanate resin which is a hardening | curing agent from a nurate type to a burette type, and since the coating film is inadequately cured, solvent resistance is bad. became.

(Evaluation of Comparative Example 1)
The film 9 for a solar cell backside sealing sheet of Comparative Example 1 uses an acrylic resin to which an ultraviolet absorber and a light stabilizer (HALS) are added as a resin layer instead of a fluorine-based resin. For this reason, as ultraviolet rays were irradiated, ultraviolet absorbers and light stabilizers bleed out from the resin layer to the surface of the resin layer, so that the ultraviolet cut performance was reduced and the Δb value of the base film was increased. Moreover, the flame retardance was also inferior.

(Evaluation of Comparative Example 2)
The film 10 for solar cell backside sealing sheets of the comparative example 2 does not contain a color pigment in the resin layer. Therefore, the ultraviolet cut performance was poor, the Δb value of the base film increased after the ultraviolet irradiation, and yellowing occurred. Moreover, since it does not contain a coloring pigment, the flame retardancy was also inferior. Furthermore, since the amount of the resin component in the resin layer was large, blocking occurred.

(Evaluation of Comparative Example 3)
The solar cell backside sealing sheet film 11 of Comparative Example 3 does not contain melamine cyanurate in the resin layer. Therefore, blocking occurred. Moreover, the coating-film adhesive force after a wet heat test also fell a little.

(Evaluation of Comparative Example 4)
The film 12 for solar cell backside sealing sheet of Comparative Example 4 (Lumirror (registered trademark) X10S film itself in which no resin layer is formed) does not have an ultraviolet cut performance, and a colored pigment layer capable of adjusting the color tone of the film is also formed. Not. Therefore, with the irradiation of ultraviolet rays, the Δb value of the base film increased and yellowing occurred. Therefore, when used for the outermost layer of the solar cell backside sealing sheet, in extreme cases, the film is cracked, pinholes, etc., and the functions required for the sealing sheet, such as electrical insulation and water vapor barrier properties In addition to being lost, there is a concern that the operation of the solar cell module may be adversely affected. Moreover, since the resin layer containing a color pigment was not formed, the flame retardance was also inferior.

Example 9
A white polyethylene terephthalate film Lumirror (registered trademark) E20F (50 μm) manufactured by Toray Industries, Inc. was prepared as a light reflective film. As a water vapor barrier film, an aluminum oxide vapor-deposited polyethylene terephthalate film manufactured by Toray Film Processing Co., Ltd. Barrier Rocks (registered trademark) 1031HGTS (12 μm) on the surface opposite to the aluminum oxide vapor-deposited layer, a coating for forming an adhesive layer and heat bonding A film was prepared by sequentially coating the coating material for forming the conductive resin layer using a two-head tandem direct gravure coater under the following conditions.
・ Adhesive layer coating conditions: Aiming at dry film thickness of 0.2μm, drying oven set temperature 120 ° C
-Thermal adhesive resin layer coating conditions: Aiming for dry film thickness of 1.0 μm, drying oven set temperature 100 ° C.
・ Coating speed: 100m / min
Aging: After application and winding, aging at 40 ° C. for 2 days.

  The adhesive for dry lamination was applied with a wire bar on the surface of the base film opposite to the resin layer of the film for solar cell backside sealing sheet 1 of Example 1, and dried at 80 ° C. for 45 seconds to 3.5 μm. The adhesive layer was formed. Next, a light reflective film was bonded to the adhesive layer using a hand roller. Further, an adhesive for dry lamination was applied with a wire bar on the light reflective film surface opposite to the resin layer of the laminate film, and dried at 80 ° C. for 45 seconds to form a 3.5 μm adhesive layer. . Then, the aluminum oxide vapor deposition layer surface of the water vapor | steam barrier film was bonded together to this adhesive bond layer using the hand roller. Thus, the sheet | seat which consists of three films produced was aged in the oven heated at 40 degreeC for 3 days, and the solar cell back surface sealing sheet 1 was obtained.

(Example 10)
A solar cell was produced in the same manner as in Example 9 except that a white polyethylene film (150 μm) manufactured by Toray Film Processing Co., Ltd., which has excellent adhesion to the EVA sheet, was used instead of E20F and the water vapor barrier film. The back surface sealing sheet 2 was obtained.

(Comparative Example 5)
The solar cell backside sealing sheet 3 is the same as the method described in Example 9, except that the solar cell backside sealing sheet film 10 of Comparative Example 2 is used instead of the solar cell backside sealing sheet film 1. Got.

(Comparative Example 6)
The solar cell backside sealing sheet 4 is the same as the method described in Example 9, except that the solar cell backside sealing sheet film 12 of Comparative Example 4 is used instead of the solar cell backside sealing sheet film 1. Got.

(Evaluation of Examples 9 and 10)
The solar cell backside sealing sheets 1 and 2 of Examples 9 and 10 are both reduced in adhesion between the base film and the resin layer due to ultraviolet irradiation to the resin layer side located on the outer layer side in the solar cell module configuration. Was not seen. The yellowing of the resin layer and the base film was very small. Moreover, it was excellent also in the adhesive force with the filler (EVA resin) which is the characteristic requested | required of the solar cell backside sealing sheet. Furthermore, the encapsulating sheet 1 including the water vapor barrier film in the constitution was excellent in water vapor barrier properties.

(Evaluation of Comparative Example 5)
Since the solar cell backside sealing sheet 3 of Comparative Example 5 does not contain a color pigment in the outermost resin layer, the effect of hiding the wiring pattern on the inner surface of the module cannot be obtained, and the appearance of the sealing sheet accompanying ultraviolet irradiation is obtained. Change in color tone (increase in Δb value) was observed. Therefore, if it is exposed to ultraviolet rays for a long time, it is expected to cause resin deterioration of the base film.

(Evaluation of Comparative Example 6)
As for the solar cell backside sealing sheet 4 of the comparative example 6, the resin layer is not formed in the outermost layer. That is, since the resin layer for cutting off ultraviolet rays is not formed, the ultraviolet ray resistance is not at all. Therefore, it cannot be used for the application of a solar cell module that assumes an installation form that may be exposed to reflected ultraviolet rays from the ground surface such as a field installation type.

  The film for solar cell backside sealing sheet of this invention is excellent in light resistance and heat-and-moisture resistance, and can be used suitably for a solar cell backside sealing sheet. Furthermore, the film for solar cell back surface sealing sheet of the preferable aspect of this invention is excellent also in a flame retardance, and can be used suitably for a solar cell back surface sealing sheet. These solar cell back surface sealing sheets can be used suitably for a solar cell module.

Claims (6)

  The film for solar cell backside sealing sheets by which the resin layer containing a fluorine-type resin, a color pigment, and a melamine cyanurate was laminated | stacked on the at least single side | surface of the base film.   The film for solar cell backside sealing sheets of Claim 1 in which the said resin layer contains 30-80 mass% of color pigments, and 1-30 mass% of melamine cyanurates with respect to this whole resin layer.   The resin layer includes at least one polyisocyanate resin selected from the group consisting of an aromatic polyisocyanate resin, an araliphatic polyisocyanate resin, an alicyclic polyisocyanate resin, and an aliphatic polyisocyanate resin. The film for solar cell backside sealing sheets of Claim 1 or 2.   The solar cell backside sealing sheet containing the film for solar cell backside sealing sheets in any one of Claims 1-3.   A white film, a film having an inorganic oxide vapor-deposited layer, and an ethylene-vinyl acetate copolymer on the surface opposite to the side on which the resin layer of the film for solar cell backside sealing sheet according to claim 1 is laminated. A solar cell back surface sealing sheet in which at least one film selected from the group consisting of films having thermal adhesiveness with a polymer is laminated.   A solar cell module comprising the solar cell backside sealing sheet and the cell filler layer according to claim 4 or 5, wherein the solar cell backside sealing sheet and the cell filler layer are adhered.