TW201511310A - Rearside protective sheet for solar cell module - Google Patents

Abstract

Provided is a rearside protective sheet for a solar cell module having excellent adhesion to an ethylene/vinyl acetate copolymer resin sheet, which is a filler sheet, even when said sheet is exposed to high-temperature, high-humidity environments or to changes in temperature between high and low temperatures. A rearside protective sheet for a solar cell module in which a polyolefin resin film and a plastic film are layered, wherein the rearside protective sheet for a solar cell module is characterized in that the polyolefin resin film comprises at least two layers, a layer (A) and a layer (B); the layer (A) comprising a polyethylene resin (a) and a polypropylene resin (b), and the layer (B), which is on the plastic-film side, comprising a polypropylene resin, and the melting point of the polypropylene resin (b) being 145 DEG C or lower.

Description

Back protection sheet for solar cell module

The present invention relates to a back protective sheet for a solar cell module, and more particularly to a filler sheet inside a solar cell module even after exposure to a high temperature-high humidity environment or a temperature change between a high temperature and a low temperature. The back of the solar cell module is still excellent with a back protective sheet.

In recent years, solar power generation as a green energy source has been attracting attention due to an increase in awareness of environmental issues, and solar cell modules composed of various forms have been developed and proposed. In general, a solar cell module is formed by sequentially laminating a surface protective sheet or a filler sheet such as an ethylene-vinyl acetate copolymer resin by using a photovoltaic element such as a crystalline germanium solar cell element or an amorphous germanium solar cell element. The solar cell element, the filler sheet, and the back surface protective sheet layer are produced by vacuum suction and thermocompression bonding. The back surface protective sheet constituting the solar cell module is generally made of a lightweight plastic material having excellent electrical properties and strength. The polyolefin resin film is gradually used in consideration of light weight, moisture resistance, and high withstand voltage characteristics. In order to use a polyolefin-based resin film for a member of a back surface protective sheet for a solar cell module, it is necessary to solve the problem specific to the polyolefin-based resin film. Therefore, various proposals have been made. For example, in Patent Documents 1 and 2, a specific polyolefin resin film and a double are disclosed. A back protective sheet for a solar cell module in which a shaft-extending polyethylene terephthalate film is laminated.

The back protection sheet for the solar cell module can be The solar cell module is mechanically protected, and has a function of preventing the infiltration of water vapor or the deterioration of ultraviolet rays. In order to make the back protective sheet exhibit its function for a long period of time, it is required to be firmly adhered to the filler sheet. Therefore, the certification authority will perform a high-temperature and high-humidity test (85 °C 85% RH) and a dew condensation test (85 °C 85% RH and -40 °C) for the solar cell module as a long-term reliability test. In order to cope with these tests, solar cell module manufacturers pay attention to the adhesion strength of the filler sheet after the long-term reliability test.

In the inventions described in Patent Documents 3, 4, and 5, the purpose of the invention is to improve the adhesion between the filler sheet and the back sheet, but the adhesion after exposure to a high-temperature-high humidity environment is not sufficient.

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open Publication No. 2011-51124

Patent Document 2 Japanese Patent Laid-Open Publication No. 2013-201155

Patent Document 3 Japanese Patent Laid-Open Publication No. 2006-152013

Patent Document 4 Japanese Patent Laid-Open Publication No. 2003-060218

Patent Document 5 International Publication No. 2012/043248

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an ethylene-vinyl acetate copolymer resin sheet with a filler sheet even when exposed to a high temperature-high humidity environment and a temperature change between a high temperature and a low temperature. A back protective sheet for solar cell modules that is still excellent in adhesion.

The present invention is a back surface protective sheet for a solar cell module, which is a back surface protective sheet for a solar cell module in which a polyolefin resin film and a plastic film are laminated, wherein the polyolefin resin film contains at least A. Two or more layers of the layer/B layer, the layer A includes (a) a polyethylene resin and (b) a polypropylene resin, and the B layer on the plastic film side contains a polypropylene resin, and (b) a polypropylene resin. The melting point is in the range of 145 ° C or less.

The present invention can provide a back surface protective sheet for a solar cell module, which is an ethylene-vinyl acetate copolymer resin (hereinafter referred to as a filler sheet) even when exposed to a high temperature-high humidity environment or a high temperature-low temperature temperature change. There will be a case where the film is abbreviated as EVA. The adhesion of the sheet is still excellent.

The invention is described in detail below.

The present invention relates to a back protective sheet for a solar cell module, which is a solar system in which a polyolefin resin film and a plastic film are laminated. The back surface protective sheet for a battery module, characterized in that the polyolefin-based resin film contains at least two or more polyolefin-based resin films of the A layer/B layer, and the A layer contains (a) a polyethylene resin. And (b) a polypropylene resin, the B layer on the plastic film side contains a polypropylene resin, and (b) the polypropylene resin has a melting point of 145 ° C or less.

The polyolefin-based resin film of the present invention is a polyolefin-based resin film comprising at least two layers of A layer/B layer. That is, the A layer/B layer, or the A layer/B layer/C layer is a representative example, and the two layer configuration of the A layer/B layer is necessary, and it is necessary to further increase the number of layers to four or more layers as necessary. The main purpose of the layer A of the polyolefin-based resin film is to secure adhesion to the filler sheet, and the main purpose of the layer B is to ensure heat resistance.

In the present invention, the (a) polyethylene-based resin of the A layer of the polyolefin-based resin film preferably has a melting point of from 100 to 130 °C. When the melting point is set to 100 ° C or more, the thickness of the back surface protective sheet is not easily reduced when the pressure-sensitive adhesive sheet is thermocompression bonded, and it is easy to ensure the withstand voltage characteristics. When it is 130 ° C or less, the effect of improving the adhesion strength of the filler sheet is excellent.

In the present invention, the (a) polyethylene-based resin used in the layer A of the polyolefin-based resin film may, for example, be a high-pressure method low-density polyethylene, a linear low-density polyethylene, a high-density polyethylene, or the like. Mixed resin. Among them, linear low density polyethylene is preferred.

The linear low-density polyethylene (hereinafter referred to as LLDPE for short) means a copolymer of ethylene and an α-olefin, and a copolymer of an α-olefin having 4 to 20 carbon atoms, preferably 4 to 8 carbon atoms is used. More preferably, specific examples thereof include 1-butene, 1-pentene, 4-methyl-1-pentene, and 1-hexene. a copolymer of an ene, 1-heptene, 1-octene, 1-decene, 1-decene or the like. These α-olefins may be used singly or in combination, and from the viewpoint of polymerization productivity, especially 1-butene, 1-hexene, 1-octene and the like are preferably used.

In the present invention, the (b) polypropylene resin of the A layer of the polyolefin resin film has a melting point of 145 ° C or less. When the temperature exceeds 145 ° C, the adhesion to the filler sheet is insufficient, and in particular, the adhesion of the temperature change between high temperature to high humidity and high temperature to low temperature is remarkable. Further, the melting point of the (b) polypropylene resin of the layer A is preferably in the range of 120 to 140 °C. When the melting point is set to 120 ° C or higher, the heat resistance of the layer A is sufficient, and when the back surface protective sheet and the filler sheet are thermocompression bonded, the thickness of the back surface protective sheet is less likely to be partially lowered, and the withstand voltage characteristics are easily secured. Further, by setting the melting point to 140 ° C or lower, the adhesion strength to the filler sheet can be made stronger.

In the present invention, the (b) polypropylene-based resin of the A layer of the polyolefin-based resin film is selected from the group consisting of an ethylene-propylene random copolymer, an ethylene-propylene-butene random copolymer, and an ethylene-propylene block copolymer. At least one or more resins are preferred, and an ethylene-propylene random copolymer or an ethylene-propylene-butene random copolymer having a low melting point is more preferable.

In the present invention, the A layer of the polyolefin resin film has a weight composition ratio (a)/(b) of the (a) polyethylene resin to the (b) polypropylene resin in the range of 0.2 to 0.6. Preferably, it is preferably in the range of 0.30 to 0.55. By setting (a)/(b) below 0.6, the adhesion strength to the EVA sheet becomes stronger. In the present invention, the B layer is composed of a polypropylene resin, and when (a)/(b) is 0.6 or less, the ratio of the polypropylene resin in the A layer is increased, and it is easy to sufficiently ensure the adhesion to the B layer. the Sex. In the case where the layer A is only a polyethylene resin, the layer A and the layer B are easily peeled off. On the other hand, when (a)/(b) is set to 0.2 or more and the ratio of the polyethylene-based resin is set to a predetermined value or more, the polyethylene-based resin is slightly dispersed in the polypropylene-based resin, and is in the layer A. Concavities and convexities are formed on the surface, so that the lubricity of the films is easily improved.

When the above (a)/(b) is in the range of 0.2 to 0.6, it is easy to suppress the high temperature and high humidity test at 1000 ° C for 8 hours at 85 ° C and 8 hours after treatment at 85 ° C and 85% RH for 40 hours. The cycle of treatment for 30 minutes at ° C was carried out for 20 cycles, and the adhesion strength to the filler sheet was lowered after the condensation freeze test for 20 cycles.

Further, by setting (a)/(b) in the range of 0.2 to 0.6, the initial adhesion strength of the A layer side and the thermocompression bonded EVA sheet is 60 N/cm or more, and 120 ° C 100% RH condition 48 After the hour, and the adhesion strength after 96 hours at 120 ° C and 100% RH is 40 N/cm or more, it is preferable. By setting the initial adhesion strength to 60 N/cm or more, it is easy to ensure sufficient resistance to various mechanical stresses during the construction of the solar cell module by using 120 ° C under 100% RH for 48 hours, and 120 °C The adhesion strength after 96 hours under 100% RH conditions is set at 40 N/cm or more, which can suppress the problems caused by peeling of the solar cell module during long-term use.

In the present invention, the A layer of the polyolefin resin film has a weight composition ratio (a)/(b) of the (a) polyethylene resin to the (b) polypropylene resin in the range of 0.30 to 0.55. For better. If (a)/(b) is in this range, it is easy to suppress after 1000 hours of high temperature and high humidity test at 85 ° C 85% RH, and at -40 ° C after 20 hours at 85 ° C 85% RH. The 30-minute cycle was carried out for 20 cycles of the condensation freeze test, and the adhesion strength to the filler sheet was lowered. In the present invention, the surface average roughness Ra of the layer A is from 0.10 to 0.30 μm, which is preferable because it can satisfy the workability of the film during processing. Further, in order to improve the handleability and lubricity of the film, in the layer A of the present invention, 0.1 to 10% by weight of inorganic or organic particles having an average particle diameter of 1 to 5 μm may be added to the resin component of the layer A. Further, a lubricant of 0.1 to 10% by weight of an organic compound may be added to the resin component of the layer A. Examples of the lubricant of the organic compound include decylamine stearate, calcium stearate, and the like.

In the present invention, the B layer of the polyolefin-based resin film contains a polypropylene-based resin composition, and particularly has a higher melting point and a melting point of 140 than the polypropylene-based resin composition used in the layer A from the viewpoint of heat resistance. The isotactic polypropylene and ethylene-propylene block copolymer of ~170 ° C are suitable for use. The B layer may be mixed with a polyethylene resin, and from the viewpoint of heat resistance, the content is preferably less than 30% by weight based on the entire B layer resin component.

In the back surface protective sheet for a solar cell module of the present invention, the coloring agent is added to the B layer and/or the plastic film of the polyolefin resin film to provide concealability, and the back protective sheet for the solar cell module can be held. The concealment is better.

Further, as described above, a coloring agent, particularly a whitening agent, may be added to the layer B of the polyolefin-based resin film of the present invention. From the viewpoint of weather resistance, the whitening agent is preferably inorganic fine particles such as calcium carbonate, cerium oxide, aluminum oxide, magnesium hydroxide, zinc oxide, talc, kaolin, titanium oxide or barium sulfate, of which titanium oxide is used. The particles are optimal, and as the crystal form, rutile type, anatase type, brookite type, etc. are known, but The rutile type is preferred from the viewpoints of excellent whiteness, weather resistance, and light reflectivity.

When a whitening agent is used for the layer B, the polyolefin resin film is designed to have a three-layer structure of the A layer/B layer/C layer, and the layer B containing the whitening agent is sandwiched between the A layer and the C layer. It is possible to prevent the resin decomposition product containing a large amount of whitening agent from adhering to the metal nozzle at the time of manufacture, and it is possible to avoid the problem of step contamination and film damage caused by the decomposition of the decomposition product.

In the present invention, in the case where the polyolefin resin film is laminated with the C layer, the C layer is preferably a polypropylene resin composition. The C layer and the B layer contain a polypropylene resin in an amount of at least one selected from the group consisting of a homopolypropylene, an ethylene-propylene random copolymer, an ethylene-propylene-butene random copolymer, and an ethylene-propylene block copolymer. The resin or a mixed resin of the resin and the polyethylene resin is preferred. In particular, from the viewpoint of heat resistance first, lubricity, film workability, scratch resistance, and bending resistance, block copolymers are preferred, and heat resistance plus lubricity or film is added. From the viewpoints of workability, scratch resistance, and bending resistance, the melting point is preferably in the range of 140 to 170 °C. When the melting point is set to 140 ° C or higher, the heat resistance is excellent. When the back surface protective sheet for a solar cell module is thermocompression bonded to the EVA sheet, the thickness of the back surface protective sheet for the solar cell module is not partially due to temperature and pressure. It is preferable because it has low resistance and can maintain voltage withstand characteristics.

Further, the polyethylene resin may be mixed in the layer C. However, from the viewpoint of heat resistance, the content is preferably 30% by weight based on the total of the resin component of the C layer.

The polyolefin-based resin film of the present invention is preferably added with a well-known antioxidant from the viewpoint of preventing discoloration of each layer and maintaining strength. The oxidizing agent is known to have a phenol type, an aromatic amine type, a thioether type, a phosphorus type, etc., and it is preferable to use two or more types in combination in order to improve the effect by mixing in a small amount. For example, a phenol type and a phosphorus type are preferably used in combination, and a phosphorus-phenol type antioxidant is mentioned.

Examples of the other additives include a photosensitizer, an ultraviolet absorber, and a heat stabilizer. The light stabilizer can be used to prevent photo-oxidation of the active species which initiate photodegradation in the resin. Specifically, one type or a combination of two or more types selected from the group consisting of a hindered amine compound, a hindered piperidine compound, and the like can be used. Among them, a hindered amine compound is preferably used.

The above ultraviolet absorbing agent may be one which is capable of absorbing harmful ultraviolet rays in sunlight and converting it into harmless thermal energy in the molecule, and preventing active species which are initiated by photodegradation in the resin from being excited. Specifically, a benzophenone-based, benzotriazole-based, salicylic acid-based, acrylonitrile-based, metal-salt-based, hindered amine-based, and ultrafine titanium oxide (particle size: 0.01 μm~) can be used. At least one or more of the group of ultraviolet absorbers such as inorganic particles, such as 0.06 μm) or ultrafine zinc oxide (particle diameter: 0.01 μm to 0.04 μm).

Further, examples of the above thermal stabilizer include ginseng (2,4-di-tertiary butylphenyl) phosphite and bis[2,4-bis(1,1-dimethylethyl)-6-methyl. Phenyl]ethyl ester phosphorous acid, ruthenium (2,4-di-tert-butylphenyl) [1,1-biphenyl]-4,4'-diyl bisphosphonite, and bis ( Phosphorus thermal stabilizer such as 2,4-di-tertiary butylphenyl neopentaerythritol diphosphite, 8-hydroxy-5,7-di- A lactone-based thermal stabilizer such as a reaction product of a tertiary butyl-furan-2-one and o-xylene. In addition, one type or two or more types can be used. Among them, it is more preferable to use a phosphorus-based heat stabilizer and a lactone-based heat stabilizer.

Further, the polyolefin-based resin film in the present invention may contain a flame retardant as necessary. The flame retardant is not particularly limited, and a well-known technique such as an organic flame retardant or an inorganic flame retardant can be applied. Examples of the organic flame retardant include those having one or more chlorine atoms or bromine atoms in the molecule, and examples thereof include chlorinated paraffin, chlorinated polyethylene, hexachloromethylenetetrahydrofurfuric acid, and perchloroacetic acid. a monomer or polymerization having an aromatic ring such as cyclodecane, tetradecylic acid anhydride or the like, or bis(2,3-dibromopropyl)isocyanurate and having no halogen atom directly bonded to the aromatic ring. , 1,1,2,2-tetrabromoethane, 1,4-dibromobutane, 1,3-dibromobutane, 1,5-dibromopentane, α-bromobutyric acid ethyl ester, 1 A substance having no aromatic ring such as 2,5,6,9,10-hexabromocyclodecane.

Further, examples of the inorganic flame retardant include a hydroxide inorganic salt such as aluminum hydroxide or magnesium hydroxide, a phosphorus oxide such as ammonium phosphate or zinc phosphate, red phosphorus, antimony trioxide or expanded graphite.

The blending amount of the organic flame retardant and the inorganic flame retardant alone or in a mixture is preferably in the range of 5 to 30% by weight based on the resin of each layer. When the amount of addition is less than 5% by weight, there is no effect of addition, and if it exceeds 30% by weight, the dispersibility is deteriorated and the coloring due to the flame retardant occurs. The polyolefin-based resin film for the back surface protective sheet for a solar cell module of the present invention is preferably composed of an A layer/B layer or an A layer/B layer/C layer, and the layering ratio thereof is not particularly limited, but When the polyolefin resin film is 100%, the thickness ratio of the A layer is 5 to 20%, the B layer is 95 to 60%, and the C layer is 0 to 20%.

When the polyolefin-based resin film of the present invention is used as a back surface protective sheet for a solar cell module, a plastic film is laminated on the side opposite to the A layer to ensure mechanical strength and long-term durability required for the back surface protective sheet. Therefore, it is preferred that the polyolefin-based resin film of the present invention is subjected to surface modification treatment on the side opposite to the layer A. The surface modification treatment in the present invention includes corona discharge treatment in the air, corona discharge treatment in a nitrogen atmosphere, plasma treatment, etc., but it is not used for the subsequent treatment with the plastic film. Subject to such restrictions.

In the present invention, it is preferred that the surface of the layer A is not subjected to upgrading treatment. When the surface layer is subjected to the surface modification treatment together with the layer A and the side opposite to the layer A, the film is easily bonded to each other during the production of the film and the slitting step, and the problem of cracking, peeling and charging is likely to occur. Bad problems. Even if the lubricity of the films deteriorates, the problems such as workability such as lamination or coating are impaired.

As described above, in the present invention, the formation ratio of the unevenness on the surface of the layer A is proportional to the weight composition ratio of the (a) polyethylene resin to the (b) polypropylene resin of the layer A (a)/(b). And the method of determining the processability of the polyolefin-based resin film for the back surface protective sheet for a solar cell module of the present invention is generally a method of determining the processability of the surface treatment of the solar cell module of the present invention. It is a friction test in accordance with ASTM D1894-11e1 and using a slip tester. When the dynamic friction coefficient of the A surface and the B surface (A layer/B layer 2 layer component) or the A surface and the C surface (A layer/B layer/C layer 3 layer component) is less than 1.1, the lubricity is excellent, and during processing, It is preferable that problems such as adhesion or Knocking do not occur.

The plastic film in the present invention may be a single layer or a multilayer film in which a plurality of films are laminated.

The plastic film in the present invention is a polyester film of polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene naphthalate (hereinafter referred to as PEN), or the like, and a polyolefin such as polyethylene or polypropylene. Film; polystyrene film; polyamide film; polyvinyl chloride film; polycarbonate film; polyacrylonitrile film; polyimine film; fluorine resin film. From the viewpoint of mechanical strength, heat resistance, and economy, a PET film is suitably used among them, and a hydrolysis-resistant PET film is preferable from the viewpoint of maintaining long-term characteristics. Similarly, a PEN film is preferred because of the high hydrolysis resistance.

Further, from the viewpoint of weather resistance, the plastic film of the present invention is preferably a fluorine-based resin film, and a film of a laminated polyester film and a fluorine-based resin film is also suitably used.

In the present invention, the hydrolysis-resistant PET film suitable for use in a plastic film maintains the tensile elongation after storage for 10 hours under high-pressure steam at 140 ° C at 60% or more of the initial tensile elongation.

By using a hydrolysis-resistant PET film as a plastic film constituting a back surface protective sheet for a solar cell module, the weather resistance of the back surface protective sheet for a solar cell module can be greatly improved, and it is useful as a solar cell module for more than 10 years. The performance guarantee is better.

As a hydrolysis-resistant PET film, a PET film is commercially available, and when it is determined according to JIS C2151 (1996), the elongation at break of the film is compared with that before the steam treatment under high-pressure steam at 140 ° C, and the elongation is 50%. 2 times that of a film that does not have hydrolysis resistance In particular, "Lumirror" (registered trademark) X10S manufactured by Toray Industries, Inc. is suitably used as the plastic film in the present invention.

The PEN film suitable for the plastic film of the present invention is a resin obtained by polymerizing a dicarboxylic acid component with 2,6-naphthalene dicarboxylic acid, and a diol component by ethylene glycol and polymerizing by a known method. A film that is biaxially stretched.

The thickness of these hydrolysis-resistant PET film or PEN film is preferably 38 to 300 μm, and the strength (rigidity), withstand voltage of the film, the cost of the back surface protective sheet for a solar cell module, and the manufacture of the solar cell module. In terms of processing suitability, it is preferably 50 to 250 μm.

The fluorine-based resin film suitable for the plastic film of the present invention is obtained by melting a fluorine-based resin, extruding it into a sheet shape from a metal nozzle, and cooling and solidifying it on a rotary cooling drum to produce a fluorine-based target. Resin film.

Examples of the fluorine-based resin include polyvinyl fluoride, polyfluorinated ethylene, tetrafluoroethylene-hexafluoropropylene-vinylidene copolymer, tetrafluoroethylene-propylene copolymer, and tetrafluoroethylene-hexafluoropropylene-propylene copolymer. Ethylene-tetrafluoroethylene copolymer (ETFE), hexafluoropropylene-tetrafluoroethylene copolymer (FEP), perfluoro(alkyl vinyl ether)-tetrafluoroethylene copolymer, polychlorotrifluoroethylene resin, and the like. Among these fluororesins, in particular, polyvinyl fluoride, ethylene-tetrafluoroethylene copolymer (ETFE), hexafluoropropylene-tetrafluoroethylene copolymer (FEP) from the viewpoint of melt extrusion formability of the film to be formed A perfluoro(alkyl vinyl ether)-tetrafluoroethylene copolymer or a polychlorotrifluoroethylene polymer is preferred.

The fluorine-based resin film suitable for the plastic film of the present invention, by corona discharge treatment, plasma treatment, flame treatment, chemistry The surface is subjected to an activation treatment such as treatment to enhance the adhesion strength after lamination.

The plastic film of the present invention is also suitably formed by laminating the above-mentioned polyester film and a fluorine-based resin film.

In the present invention, in order to have long-term weather resistance of the back surface protective sheet for a solar cell module, it is preferable to laminate an ultraviolet absorbing layer on the side opposite to the side on which the plastic film and the polyolefin resin film are laminated. In this case, it is suitable. The resin composition containing a UV absorber in a binder resin such as an acrylic resin or a resin obtained by copolymerizing an acrylic resin or the like with an ultraviolet absorber and a light stabilizer is exemplified, but a plastic film is used. From the viewpoint of the adhesion of the substrate or the weather resistance of the ultraviolet absorbing layer itself, it is preferred to include a resin obtained by copolymerizing an acrylic resin or the like with an ultraviolet absorber and a light stabilizer.

The ultraviolet absorber which is copolymerized with the acrylic resin may, for example, be an ultraviolet absorber such as a salicylic acid, a benzophenone, a benzotriazole or a cyanoacrylate.

Further, similarly to the light stabilizer of the acrylic resin copolymerization, a light stabilizer such as a hindered amine system can be mentioned.

It is preferable to add a white pigment to the ultraviolet absorbing layer, and it is preferable to improve the weather resistance of the resin of the ultraviolet absorbing layer. From the viewpoint of versatility, price, color development property, and ultraviolet ray resistance, the white pigment is titanium oxide. It is better.

The thickness of the ultraviolet absorbing layer is preferably 0.2 to 5 μm, more preferably 1 to 4 μm, and particularly preferably 1 to 3 μm. By setting the thickness of the ultraviolet absorbing layer to 0.2 μm or more, cracking or filming does not occur at the time of coating. By breaking these phenomena, it is easy to form a uniform coating film, and it is sufficient to sufficiently exhibit the adhesion to the plastic film, particularly the polyethylene terephthalate film, and the most important ultraviolet shielding performance. On the other hand, when the thickness of the ultraviolet absorbing layer is 5 μm or less, the ultraviolet shielding performance can be sufficiently exhibited, and if it is thicker than this value, the coating method is limited, and there is a concern that the production cost becomes high. In the present invention, the adhesive used for bonding the plastic film and the polyolefin-based resin film is not particularly limited, but an isocyanate cross-linking type adhesive is generally used. Among them, in order to produce a back surface protective sheet for a solar cell module which is excellent in weather resistance and which is subsequently reduced in strength, it is preferred to use an adhesive having excellent hydrolysis resistance.

The solvent used for the above-mentioned adhesive is preferably a solvent having no active hydrogen such as an ester, a ketone, an aliphatic or an aromatic. Examples of the esters include ethyl acetate, propyl acetate, and butyl acetate. Examples of the ketones include methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of the aliphatic group include n-heptane, n-hexane, and cyclohexane. Examples of the aromatic group include toluene and xylene. From the viewpoint of solubility and coating suitability, ethyl acetate, propyl acetate, and methyl ethyl ketone are particularly preferred among these.

Further, the thickness of the layer composed of the adhesive is preferably 0.1 to 10 μm, and more preferably 2 to 6 μm from the viewpoint of cost surface and adhesion. The specific manufacturing method of the back surface protective sheet for a solar cell module of the present invention can be carried out by using a gravure-roll coating method, a reverse coating method, an anastomosis coating method, another coating method, or a dry laminate in which an adhesive is applied by a printing method or the like. For example, a film of an olefin-based resin film is deposited as a plastic film, for example, a PET film. At this point, the PET film can also respond It is necessary to perform surface treatment for improving adhesion by corona treatment, plasma treatment, or the like. The PET film may be coated with an adhesive by a gravure-roll coating method, a reverse coating method, an anastomosis coating method, another coating method, or a brush method on the side opposite to the surface on which the adhesive is applied in advance, thereby forming an ultraviolet ray absorption. Floor. Next, the adhesive-coated surface of the PET film was bonded to the opposite side of the layer A of the polyolefin-based resin film.

The adhesion strength between the plastic film and the polyolefin resin film is preferably 2 N/15 mm or more. When the adhesion strength between the films is 2 N/15 mm or more, the interlayer strength of the laminated film can be sufficiently obtained, and interlayer peeling due to the test or the promotion of the solar cell module is less likely to occur, and 6 N/15 mm or more is preferable.

[Examples]

The invention will now be described in detail by way of examples. Further, each characteristic was measured and evaluated by the following method.

(1) The solar cell module for evaluating the EVA adhesion strength is a solar cell module in the direction in which the A-side of the polyolefin-based resin film for the solar cell module back protective sheet faces the EVA sheet 2 in this order. Group back protective sheet/EVA sheet 2 (manufactured by FirstEVA Co., Ltd., F806 thickness: 450 μm) / EVA sheet 1 (manufactured by FirstEVA Co., Ltd., F806 thickness: 450 μm) / glass sheet laminate, solar cell module laminator manufactured by NPC Co., Ltd. After (LM-50X50-S), heating and pressure bonding were performed under conditions of a vacuum time of 5.5 minutes, a control time of 1 minute, a rolling time of 11.5 minutes, and a temperature of 148 °C. After crimping, it was cooled to room temperature to prepare a solar cell module for evaluation. The adhesion strength (initial) of the transverse direction in the longitudinal direction of the polyolefin resin film was measured. By the sun The back side protective sheet/EVA sheet layer was peeled off at a width of 10 mm on the back side protective sheet side of the battery module, and Tensilon PTM-50 manufactured by Orientec Co., Ltd. was used at room temperature, and the peeling angle was 180°, and the peeling speed was 100 mm/min. Peel off and measure the adhesion strength.

(2) EVA adhesion strength after high temperature and high humidity test

The solar cell module for evaluation was stored in a high-temperature and high-humidity environment at 85° C. and 85% RH for 1,000 hours, and then stored at 120° C. and 100% RH for 48 hours or stored for 96 hours, and then peeled off in the same manner as described above. The EVA adhesion strength was measured.

(3) EVA adhesion strength after condensation freeze test

The solar cell module for evaluation was subjected to a dew condensation freezing treatment in which a cycle of treatment at 85 ° C, 85% RH for 20 hours, and a treatment at -40 ° C for 30 minutes was carried out for 20 cycles, and then peeling was performed in the same manner as above, and EVA was measured. Adhesion strength.

(4) Determination of melting point

The melting point of the resin to be used was measured by a differential scanning calorimeter (DSC-60, manufactured by Shimadzu Corporation) at a rate of 10 ° C/min, and the highest peak temperature of the melting peak when heated from 20 ° C to 300 ° C was defined as the melting point.

(5) Processability assessment

In the polyolefin-based resin film of the present invention, the A surface and the B surface (A layer/B layer 2 layer constituent product), or the A surface and the C surface (A layer/B layer/C layer 3 layer constituent product), etc. The coefficient of dynamic friction of one surface and the other surface of the polyolefin-based resin film was measured in accordance with ASTM D1894-11e1 using a slip tester. The following determination was made based on the result of the friction coefficient, and "△" or more was judged as pass according to the following criteria.

○: Dynamic friction coefficient is less than 0.9

△: The dynamic friction coefficient is 0.9 or more and less than 1.1.

×: The dynamic friction coefficient is 1.1 or more.

(Example 1)

A polyolefin-based resin film composed of three layers of the A layer/B layer/C layer, and the resin used for the A layer is an ethylene-propylene-butene random copolymer which is (b) a polypropylene resin ( a linear low-density polyethylene (melting point of 128 ° C, an ethylene content of 7% by weight, a butene content of 3% by weight, abbreviated as r-EPBC) of 72% by weight, and a linear low-density polyethylene of (a) a polyethylene resin (melting point: 127 ° C, A resin obtained by mixing an ethylene-1-butene copolymer, which is simply referred to as LLDPE (C4) 28% by weight. The weight composition ratio of (a)/(b) was 0.39. The resin used in the layer B is an ethylene-propylene random copolymer (melting point 147 ° C, ethylene content 4% by weight, abbreviated as r-EPC (1)) 80% by weight with respect to the polypropylene resin, and mixing r- EPC (1) 40% by weight and rutile-type titanium oxide having a surface treatment of an inorganic oxide having one or more of ruthenium, aluminum, zinc and the like as a main component and having an average particle diameter of 200 nm 60% by weight of the company FTR-700) A resin obtained by melt-kneading at 240 ° C in a twin-screw extruder and then granulating the titanium oxide masterbatch (abbreviated as titanium oxide MB) by 20% by weight. The amount of titanium oxide added to the whitening agent was 12% by weight. The resin used in the layer C is an ethylene-propylene block copolymer (melting point: 160 ° C, ethylene content: 7% by weight, abbreviated as b-PP) of 100% by weight of a polypropylene resin. The respective resins of the layers A, B, and C prepared in this manner were supplied to a uniaxial melt extruder, respectively, and melted at 260 ° C, and guided to the A layer / B layer / C layer type. The multi-channel type T mold is extruded to a casting drum maintained at 30 ° C, and is cooled and solidified by blowing cold air of 25 ° C from the non-roller surface side, thereby obtaining a thickness ratio of each layer to layer A/B layer/C layer. A polyolefin-based resin film having a thickness of 150 μm of 20%/70%/10%. The C layer side of the polyolefin resin film was 23 W in the atmosphere. The electric energy of min/m ² was subjected to corona discharge treatment so that the wetting tension of the surface of the layer C became 40 mN/m, and was wound.

A coating agent "Hulls-hybrid" polymer (registered trademark) BK1 (solid content concentration: 40) obtained by crosslinking a UV absorber and a light stabilizer (HALS) manufactured by Nippon Shokubai Co., Ltd. and an acrylic polyol resin. The weight %, acrylic resin) was mixed with a whitening agent, a plasticizer, and a solvent, and it was disperse|distributed by the bead mill, and the base-coating agent for resin layer formation of the solid-

Next, in the main-agent paint for forming a resin layer obtained by the above method, an amount of the ratio of the weight ratio of the main-agent paint to 33/8 is calculated in advance to blend the isocyanurate type (Nurate) type six. "Desmodur" (registered trademark) N3300 (solid content concentration: 100% by weight) manufactured by Bayeine Ammonium Co., Ltd., a methylene diisocyanate resin, and then measured in advance to make it a solid component The diluent of the coating material having a concentration of 20% by weight (resin solid content concentration): n-propyl acetate was stirred for 15 minutes to obtain a coating material for forming an ultraviolet absorbing layer having a solid content concentration of 20% by weight (resin solid content concentration).

Further, the whitening agent used for the above adjustment was titanium oxide particles (JR-709 manufactured by Tayca Co., Ltd.), and the plasticizer was an epoxy plasticizer ("Epocizer" W-121) manufactured by DIC Corporation.

A hydrolysis-resistant biaxially stretched PET film ("Lumirror" (registered trademark) X10S (125 μm) manufactured by Toray Industries, Inc.) was prepared as a plastic film. On the one side of the film, the coating material for forming an ultraviolet absorbing layer was applied by a dry laminator (a dry laminator OG/DL-130TA-AF with monochromatic printing manufactured by Okazaki Machinery Co., Ltd.), and dried at 150 ° C. In the second, the solid content coating thickness was set to 1 μm to provide an ultraviolet absorbing layer.

Next, an isocyanate cross-linking adhesive (LX-903/KL-manufactured by Dainippon Ink and Chemicals Co., Ltd.) was applied to one surface and the opposite surface of the ultraviolet absorbing layer of the above-mentioned "Lumirror" X10S by the dry laminator. 75 = 8 / 1), the solid content was applied to a thickness of 4 μm, and dried, and laminated on the C layer side of the polyolefin-based resin film at a nip of 60 N/cm.

The laminated film was aged at a temperature of 40 ° C for 72 hours to promote the hardening reaction of the adhesive layer, and the back protective sheet for a solar cell module was produced by the present invention. The results of the evaluation are disclosed in Table 1.

After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Example 2)

The thickness of the olefin-based resin film of the first embodiment was changed to 200 μm in the same manner as in the first embodiment, and the water-resistant biaxially stretched PET film was used as the plastic film (the thickness of the layer A/B layer/C layer) was changed to 200 μm. A back surface protective sheet for a solar cell module was produced in the same manner as in Example 1 except that the thickness of the "Lumirror" X10S) manufactured by Toray Industries, Inc. was 75 μm. The results of the evaluation are disclosed in Table 1.

After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Example 3)

The same procedure as in Example 1 was carried out except that the ultraviolet absorbing layer described in Example 1 was replaced with the MX11 (75 μm) of the "Lumirror" hydrolysis-resistant white PET film manufactured by Toray Industries, Inc. Method A back protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 1.

After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Example 4)

In the polyolefin-based resin film of the first embodiment, the resin used in the layer A is a copolymer of ethylene-propylene (melting point: 135 ° C, ethylene content: 6% by weight, and simply referred to as r-EPC (2). )) A solar energy produced in the same manner as in Example 1 except that the resin composition of 23% by weight of LLDPE (C4) was mixed in an amount of 23% by weight, and the weight composition ratio of (a)/(b) was set to 0.30. Back protection sheet for battery modules. The results of the evaluation are disclosed in Table 1.

After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Example 5)

In the polyolefin-based resin film of the first embodiment, the resin used in the layer A is a resin obtained by mixing 35 wt% of LLDPE (C4) with respect to 65 wt% of r-EPC (2), and (a) In the same manner as in Example 1, except that the weight composition ratio of (b) was set to 0.54. Back protection sheet for solar cell modules. The results of the evaluation are disclosed in Table 1.

After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Example 6)

In the polyolefin-based resin film of the first embodiment, the resin used for the layer A is a resin obtained by mixing 20% by weight of LLDPE (C4) with respect to 80% by weight of r-EPBC, and (a)/(b) A back surface protective sheet for a solar cell module was produced in the same manner as in Example 1 except that the weight ratio was 0.25. The results of the evaluation are disclosed in Table 1. After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Example 7)

In the polyolefin-based resin film of the first embodiment, the resin used in the layer A is a resin obtained by mixing 40% by weight of LLDPE (C4) with respect to 60% by weight of r-EPBC, and (a)/(b) A back surface protective sheet for a solar cell module was produced in the same manner as in Example 1 except that the weight ratio was 0.67. The results of the evaluation are disclosed in Table 1. After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was 40 N/cm or more.

(Comparative Example 1)

In the polyolefin-based resin film of the first embodiment, the resin used in the layer A is an ethylene-propylene random copolymer (melting point: 147 ° C, ethylene content: 4% by weight), which is abbreviated as a substitute for r-EPBC. a tree of r-EPC (1)) 72% by weight mixed with LLDPE (C4) 28% by weight A back surface protective sheet for a solar cell module was produced in the same manner as in Example 1 except that the weight composition ratio of (a)/(b) was changed to 0.39. The results of the evaluation are disclosed in Table 1. In the initial stage, the EVA adhesion strength was 40 N/cm or more. However, after the high temperature and high humidity test, after the condensation freeze test, the EVA adhesion strength was less than 40 N/cm, which was not sufficient.

(Comparative Example 2)

In the polyolefin-based resin film of the first embodiment, the resin used in the layer A is mixed with 70% by weight of the homopolypropylene (melting point: 160 ° C, abbreviated as h-PP) instead of r-EPBC. In the same manner as in Example 1, except that the resin composition of the linear low-density polyethylene (LLDPE (C4)) was 30% by weight, and the weight composition ratio of (a)/(b) was 0.43. A back protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 1.

The EVA adhesion strength was 40 N/cm or more at the initial stage. However, after the high temperature and high humidity test and the condensation freeze test, it was not sufficient to be less than 40 N/cm.

(Comparative Example 3)

In Comparative Example 1, the resin used in the layer A was a resin obtained by mixing 35 wt% of LLDPE (C4) with respect to 65 wt% of r-EPC (1), and the weight composition ratio of (a)/(b) was used. A back surface protective sheet for a solar cell module was produced in the same manner as in Comparative Example 1, except that the amount was 0.54. The results of the evaluation are disclosed in Table 1.

The EVA adhesion strength was 40 N/cm or more at the initial stage. However, after the high temperature and high humidity test and the condensation freeze test, it was not sufficient to be less than 40 N/cm.

(Comparative Example 4)

In the same manner as in Example 1, except that the resin used in the layer A was 100% by weight of LLDPE (C4), the resin used for the solar cell module was produced in the same manner as in Example 1. Back protection sheet. The results of the evaluation are disclosed in Table 1.

After the initial stage, high temperature and high humidity test, and dew condensation test, the EVA adhesion strength was less than 40 N/cm and was insufficient.

(Example 8)

The resin used for the layer A was a resin obtained by mixing 25% by weight of LLDPE (C4) with respect to 75 wt% of r-EPBC (melting point: 128 ° C). The weight composition ratio of (a)/(b) was 0.33. The resin used for the layer B was a resin obtained by mixing 80% by weight of titanium oxide MB with 80% by weight of r-EPC (1). The amount of titanium oxide added to the whitening agent was 12% by weight.

Each resin of each of the A layer and the B layer prepared in this manner was supplied to a uniaxial melt extruder, and melted at 260 ° C, respectively, and guided to a multi-channel type T of the A layer/B layer type. The mold was extruded to a casting drum maintained at 30 ° C, and cold air of 25 ° C was blown from the non-roller surface side to be solidified by cooling, and the thickness ratio of each layer was obtained as A layer / B layer = 20% / 80% and the thickness was A 150 μm polyolefin resin film.

For the B-layer side of this polyolefin-based resin film, it is 23 W in the atmosphere. The electric energy of min/m ² was subjected to corona discharge treatment so that the wetting tension of the surface of the layer B became 40 mN/m, and was wound.

A hydrolysis-resistant biaxially stretched PET film ("Lumirror" (registered trademark) X10S (125 μm) manufactured by Toray Industries, Inc.) was prepared as a plastic film.

The above-mentioned "Lumirror" X10S coated isocyanate cross-linking adhesive (Daily Ink Chemical Industry Co., Ltd.) by a dry laminator (Okasaki Machinery Co., Ltd., a monochrome laminator OG/DL-130TA-AF) Co., Ltd., LX-903/KL-75=8/1), a solid component coating thickness of 5 μm, and drying, and a layering of the B-layer side of the polyolefin-based resin film at a clamping pressure of 60 N/cm. .

The laminated film was aged at a temperature of 40 ° C for 72 hours to promote the hardening reaction of the adhesive layer, and a back protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was 60 N/cm or more at the initial stage, and was 40 N/cm or more after 48 hours of the moist heat resistance test.

(Example 9)

The resin used for the layer A was a resin obtained by mixing 20% by weight of HDPE with respect to 80% by weight of r-EPBC. The weight composition ratio of (a)/(b) is 0.25. The resin used for the layer B was a resin obtained by mixing 20% by weight of titanium oxide MB with 80% by weight of h-PP. The amount of titanium oxide added to the whitening agent was 12% by weight.

Each resin of each of the A layer and the B layer prepared in this manner was supplied to a uniaxial melt extruder, and melted at 260 ° C, respectively, and guided to a multi-channel type T mold of the A layer/B layer type. Extrusion to a casting drum maintained at 30 ° C, blowing cold air of 25 ° C from the non-roller side to cool and solidify, and obtaining a thickness ratio of each layer of A layer / B layer = 10% / 90% 150 μm A back surface protective sheet for a solar cell module was produced in the same manner as in Example 8 except that the polyolefin resin film was used. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was 60 N/cm or more at the initial stage, and was 40 N/cm or more after 48 hours of the moist heat resistance test.

(Embodiment 10)

The resin used for the layer A was a resin obtained by mixing 20% by weight of LLDPE (C6) with respect to 80% by weight of r-EPBC. The weight composition ratio of (a)/(b) is 0.25. The resin used for the layer B was a resin obtained by mixing 80% by weight of titanium oxide MB with 80% by weight of r-EPC (1). The amount of titanium oxide added to the whitening agent was 12% by weight.

Each resin of each of the A layer and the B layer prepared in this manner was supplied to a uniaxial melt extruder, and melted at 260 ° C, respectively, and guided to an A layer / B layer multi-flow type T mold, and extruded. It was discharged to a casting drum maintained at 30 ° C, and cold air of 25 ° C was blown from the non-roller surface side to be solidified by cooling, thereby obtaining a polymer having a thickness ratio of each layer of layer A/B layer=20%/80% and thickness of 150 μm. An olefin resin film.

For both sides of this polyolefin-based resin film, it is 23 W in the atmosphere. The electric energy of min/m ² was subjected to a corona discharge treatment, and the wetting tension of the surface of the layer A and the layer B was 40 mN/m, and wound, and the same manner as in the example 8 was carried out. A back protective sheet for the solar cell module. The results of the evaluation are disclosed in Table 2.

In the polyolefin-based resin film, since both surfaces of the A layer and the B layer are subjected to surface modification treatment, although the lubricity of the films is slightly inferior, it is still usable, and there is no back protective sheet for a solar cell module. problem.

(Example 11)

The resin used for the layer A was a resin obtained by mixing 10 wt% of LLDPE (C4) and 15 wt% of HDPE with respect to 75 wt% of r-EPBC. At this time, the weight composition ratio of (a)/(b) was 0.33. The resin used for the layer B was a resin obtained by mixing 80% by weight of titanium oxide MB with 80% by weight of r-EPC (1). The amount of titanium oxide added to the whitening agent was 12% by weight. The resin used for the layer C was 100% by weight of b-PP.

Each of the layers A, B, and C prepared in this manner was supplied to a uniaxial melt extruder, and melted at 260 ° C, respectively, and guided to the A layer / B layer / C layer type. The flow path type T mold was extruded to a casting drum maintained at 30 ° C, and cold air of 25 ° C was blown from the non-roller surface side, and cooled and solidified, thereby obtaining a thickness ratio of each layer to A layer / B layer / C layer. = 20% / 70% / 10% of a polyolefin resin film having a thickness of 150 μm. A back protective sheet for a solar cell module was produced in the same manner as in Example 8. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was 60 N/cm or more at the initial stage, and was 40 N/cm or more after 48 hours of the moist heat resistance test.

(Embodiment 12)

The resin used for the layer A was a resin obtained by mixing 35 wt% of LLDPE (C4) with respect to r-EPC (2) (melting point: 135 ° C). The weight composition ratio of (a)/(b) was 0.54. The resin used for the layer B was a resin obtained by mixing 80% by weight of titanium oxide MB with 80% by weight of r-EPC (1). The amount of titanium oxide added to the whitening agent was 12% by weight. The resin used for the layer C was 100% by weight of b-PP.

Each of the resins of the layers A, B, and C prepared in this manner was supplied to a uniaxial melt extruder, and melted at 260 ° C, respectively, and guided to the A layer / B layer / C layer type. The multi-flow type T-die was extruded to a casting drum maintained at 30 ° C, and cold air of 25 ° C was blown from the non-roller surface side to be cooled and solidified, and the thickness ratio of each layer was A layer / B layer / C layer. = 20% / 70% / 10% of a polyolefin resin film having a thickness of 150 μm. The C layer side of this polyolefin-based resin film is 23 W in the atmosphere. The electric energy of min/m ² was subjected to corona discharge treatment so that the wetting tension of the surface of the layer C became 40 mN/m, and was wound. A back protective sheet for a solar cell module was produced in the same manner as in Example 8. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was 60 N/cm or more at the initial stage, and was 40 N/cm or more after 48 hours of the moist heat resistance test.

(Example 13)

In the example 12, the resin used for the layer A of the polyolefin resin film is a resin obtained by mixing 40% by weight of LLDPE (C4) with respect to 60% by weight of r-EPC (2), and (a) / (b) A weight ratio of 0.67) polyolefin resin-based film. A back protective sheet for a solar cell module was produced in the same manner as in Example 8. The results of the evaluation are disclosed in Table 2.

Although the adhesion strength between the protective sheet and the EVA sheet was less than 60 N/cm at the initial stage, the heat resistance test was 40 N/cm or more after 48 hours.

(Example 14)

In the example 12, the resin used for the layer A of the polyolefin resin film is a resin obtained by mixing 10% by weight of LLDPE (C4) with 90% by weight of r-EPC (2), and (a) / (b) A polyolefin resin film having a weight composition ratio of 0.11), and a back surface protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was 60 N/cm or more at the initial stage, and was 40 N/cm or more after 48 hours of the moist heat resistance test. Since the ratio of the polyethylene-based resin of the A layer is low, although the lubricity is slightly inferior, it is still in a practical grade.

(Example 15)

In the example 12, the resin used for the layer A of the polyolefin resin film was prepared by mixing 50% by weight of LLDPE (C4) with 50% by weight of r-EPC (2), and (a) / (b) The weight composition ratio of 1.0) The polyolefin resin film was used to produce a back surface protective sheet for a solar cell module. The results of the evaluation are disclosed in Table 1.

Although the adhesion strength between the protective sheet and the EVA sheet was less than 60 N/cm at the initial stage, it was 40 N/cm or more after 48 hours of the moist heat resistance test. However, the heat and humidity resistance test was lower than 40 N/cm after 96 hours.

(Comparative Example 5)

In the example 12, the resin used for the layer A of the polyolefin-based resin film was 100% by weight of LLDPE (C4) to prepare a polyolefin-based resin film, and a back surface protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was less than 60 N/cm at the initial stage and less than 40 N/cm after 48 hours of the heat and humidity resistance test, which was not sufficient. Although the EVA sheet and the A layer are closely adhered to each other, the adhesion strength between the A layer and the B layer is insufficient, so that the desired adhesion strength is not exhibited.

(Comparative Example 6)

In the eighth embodiment, the resin used for the layer A of the polyolefin-based resin film was made of r-EPBC 100% by weight to prepare a polyolefin-based resin. The film and the back protective sheet for the solar cell module are produced. The results of the evaluation are disclosed in Table 2.

The polyolefin-based resin film has a high coefficient of dynamic friction and is observed to be adhered when the roll is formed. When used as a back protective sheet for a solar cell module, there is no problem in adhesion strength to the EVA sheet, but there is a problem in workability. .

(Comparative Example 7)

In the example 12, the resin used for the layer A of the polyolefin resin film is a resin obtained by mixing 30% by weight of LLDPE (C4) and 70% by weight of h-PP (melting point: 160 ° C) ((a)/( b) The weight composition ratio of 0.43) was prepared to produce a polyolefin resin film, and a back surface protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was less than 60 N/cm at the initial stage, and was not sufficient at 40 N/cm after the heat and humidity resistance test.

(Comparative Example 8)

In Example 12, the resin used for the layer A of the polyolefin-based resin film was 35 wt% of LLDPE (C4) and 65 wt% of r-EPC (2) (melting point 147 ° C) ((a)/(b). A weight ratio of 0.54) was used to prepare a polyolefin resin film, and a back surface protective sheet for a solar cell module was produced. The results of the evaluation are disclosed in Table 2.

The adhesion strength between the protective sheet and the EVA sheet was less than 60 N/cm at the initial stage, and was not sufficient at 40 N/cm after the heat and humidity resistance test.

Claims (8)

A back surface protective sheet for a solar cell module, which is a back surface protective sheet for a solar cell module in which a polyolefin resin film and a plastic film are laminated, wherein the polyolefin resin film contains at least an A layer/B. The two layers of the layer include (a) a polyethylene resin and (b) a polypropylene resin, and the B layer on the plastic film side contains a polypropylene resin, and (b) the polypropylene resin has a melting point of 145. The range below °C. The back protective sheet for a solar cell module according to claim 1, wherein the weight composition ratio (a)/(b) of the (a) polyethylene resin to the (b) polypropylene resin of the layer A is 0.2 to 0.6. range. The back protective sheet for a solar cell module according to claim 1, wherein the weight composition ratio (a)/(b) of the (a) polyethylene resin to the (b) polypropylene resin of the layer A is between 0.30 and 0.55. range. The back protective sheet for a solar cell module according to any one of claims 1 to 3, wherein the adhesion strength of the A layer side of the polyolefin resin film to the thermocompression bonded ethylene-vinyl acetate copolymer resin sheet, It is 40 N/cm or more after 1000 hours at 85 ° C under 85% RH. The back protective sheet for a solar cell module according to any one of claims 1 to 3, wherein the adhesion strength of the A layer side of the polyolefin resin film to the thermocompression bonded ethylene-vinyl acetate copolymer resin sheet, It was 40 N/cm or more after the dew condensation freezing test of alternating 20 cycles at 85 ° C 85% RH and -40 ° C. The back protective sheet for a solar cell module according to any one of claims 1 to 3, wherein the adhesion strength of the A layer side of the polyolefin resin film to the thermocompression bonded ethylene-vinyl acetate copolymer resin sheet, It was 40 N/cm or more after 48 hours at 120 ° C under 100% RH. The back protective sheet for a solar cell module according to any one of claims 1 to 3, wherein the adhesion strength of the A layer side of the polyolefin resin film to the thermocompression bonded ethylene-vinyl acetate copolymer resin sheet, The initial stage was 60 N/cm or more, and it was 40 N/cm or more after 96 hours at 120 ° C and 100% RH. The back protective sheet for a solar cell module according to any one of claims 1 to 7, wherein the surface of the layer A of the polyolefin-based resin film is not modified.