JP2011165908A - Back sheet for solar cell, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a back sheet for solar cell that is inexpensive and is superior in steam barrier property and adhesion with EVA which is a sealing material. <P>SOLUTION: The back sheet for solar cell has a modified clay film a1, adhesive film b1, and PET film c1 laminated thereon, wherein the modified clay film a1 contains a modified clay obtained by reacting a clay with a silylation agent and either of polyamide and polyimide as an additive, and at least 90 mol% of exchangeable ion of the modified clay is lithium ion. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In recent years, from the viewpoints of effective use of resources and prevention of environmental pollution, attention has been focused on solar cells that directly convert sunlight into electrical energy, and further research is ongoing.

  There are various types of solar cells. Typical examples include amorphous silicon solar cells, crystalline silicon solar cells, and dye-sensitized solar cells.

  A silicon-based solar cell is generally composed of a surface protection material, a silicon power generation element, a back surface sealing material, a back sheet (back surface protection sheet), and the like.

  Amorphous silicon solar cells have the advantage that the amount of silicon used is small, but they are easily affected by humidity. Therefore, there is a problem that the output is reduced due to the ingress of water vapor under high humidity. In order to solve this problem, a back sheet excellent in moisture resistance has been developed.

  In addition to providing moisture resistance to the backsheet and protecting the contents such as silicon power generation elements and lead wires, weather resistance, heat resistance, water resistance, insulation, corrosion resistance, and backside sealing Adhesiveness with an ethylene-vinyl acetate copolymer (EVA) usually used as a material is required.

  As such a back sheet, for example, a back sheet having a three-layer structure of polyvinyl fluoride (PVF) / aluminum foil / polyvinyl fluoride (PVF) is known and used for many years (Patent Document 1). The aluminum foil is extremely excellent in water vapor barrier properties, and the polyvinyl fluoride (PVF) film is excellent in weather resistance and insulation properties. However, polyvinyl fluoride (PVF) is poor in adhesiveness with the ethylene-vinyl acetate copolymer (EVA) used as the back surface sealing material, and the polyvinyl fluoride (PVF) is expensive. There was a problem that it was difficult to price. In addition, an adhesive is used for bonding each film, which requires processing such as coating, which has been one of the causes of cost increase.

  A back sheet in which a polyethylene terephthalate (PET) film / a resin film on which a metal oxide is deposited / a polyethylene terephthalate (PET) film is laminated has been proposed (Patent Document 2). However, the PET film has a problem of poor adhesiveness with an ethylene-vinyl acetate copolymer (EVA) used as a back surface sealing material. In order to improve the adhesion to EVA, attempts have been made to apply a primer to the backsheet in advance, but this is one of the factors that increase the cost of the backsheet.

  A modified clay film (film) using a modified clay as a main component and a resin or the like as an additive has been developed and applied to a back sheet (Patent Document 3). However, there was room for improvement in heat resistance and water vapor barrier properties. Moreover, adhesiveness with EVA which is a sealing material is not sufficient, and there is room for improvement. Furthermore, adhesiveness with resin films, such as PET, was not enough, and the adhesive agent was required for the laminated film formation.

  A back sheet using a maleic anhydride-modified polyolefin resin as an adhesive layer has been proposed (Patent Document 4). Although it has excellent adhesion to polyolefin resins such as polypropylene, there is room for improvement in adhesion to EVA and aluminum foil.

  On the other hand, an epoxy-modified polyolefin resin composition is known as a composition having excellent adhesiveness (Patent Document 5). However, since the water vapor barrier property of the maleic anhydride-modified polyolefin resin composition (Patent Document 4) is low and the water vapor barrier property is expected to be reduced by the introduction of a polar group, the back sheet requires high moisture resistance. The application to this has not been studied so far. Furthermore, the epoxy-modified polyolefin-based resin composition is highly difficult to apply and use like an adhesive, and it has been predicted that the productivity of the backsheet is reduced and the cost is increased.

JP 2008-235882 A Japanese Patent Laid-Open No. 2002-100788 JP 2007-277078 A JP 2008-270685 A JP 2009-24136 A

  That is, the problem to be solved by the present invention is to provide a solar cell backsheet that is inexpensive, has a water vapor barrier property, and has excellent adhesion to EVA as a sealing material.

  The inventors of the present invention have a back sheet containing a modified clay film and an adhesive film, which has excellent water vapor barrier properties and adhesion to EVA as a sealing material, and further reduces the productivity of the back sheet without reducing the productivity. The production method which can be performed was found and the present invention was completed. Furthermore, the present inventors have found that an epoxy-modified polyolefin resin film, which is an adhesive film, adheres well to a modified clay film and can solve the adhesiveness with EVA, which has been a problem in the modified clay film.

  The present invention has the following configuration.

  The present invention is a solar cell backsheet in which (A) a modified clay film and (B) an adhesive film are laminated, wherein (A) the modified clay film is obtained by reacting a clay with a silylating agent. And at least 90 mol% of the exchangeable ions of the modified clay is lithium ions, which contains either polyamide or polyimide as an additive.

As a preferred embodiment, (A) the modified clay film has a water vapor permeability (40 ° C., 90% RH) of 0.000001 to 0.2 g / (m ² · day). Related to backsheet.

  In a preferred embodiment, the present invention relates to a solar cell backsheet, wherein the weight of the silylating agent of the modified clay is 1 to 30% by weight based on the total weight of the clay and the silylating agent.

  A preferred embodiment relates to a back sheet for a solar cell, wherein the weight of the additive of the modified clay film (A) is 5 to 20% by weight based on the total weight of the modified clay and the additive.

  In a preferred embodiment, the clay used in the modified clay is at least one selected from the group consisting of mica, vermiculite, montmorillonite, beidellite, saponite, hectorite, stevensite, magadiite, isralite, kanemite, illite, and sericite. The present invention relates to a solar cell backsheet characterized by being a kind of clay.

As a preferred embodiment, (A) the modified clay film has flexibility and mechanical strength that can be used as a self-supporting film, can be used without a crack at a bending radius of 3 mm, and can be used against oxygen gas. The present invention relates to a solar cell backsheet characterized by having a permeability coefficient of less than 4.0 × 10 ⁻¹⁵ cm ² s ⁻¹ cmHg ⁻¹ .

  As a preferred embodiment, (A) the modified clay film has a thickness of 3 to 100 μm, which relates to a solar cell backsheet.

  A preferred embodiment relates to a solar cell backsheet characterized in that, in (A) thermogravimetric measurement of the modified clay film, the 5% weight loss temperature is 300 ° C to 760 ° C.

  As a preferred embodiment, (B) the adhesive film is a modified polyolefin resin, acrylic resin, urethane resin, polyester resin, silicone resin, polyisobutylene resin, ethylene-vinyl alcohol copolymer (EVOH). It is related with the solar cell backsheet characterized by being at least 1 sort (s) chosen from the group which consists of ethylene-vinyl acetate copolymer (EVA).

  As a preferred embodiment, the present invention relates to a solar cell backsheet, wherein the modified polyolefin resin is an epoxy-modified polyolefin resin.

  As a preferred embodiment, an epoxy-modified polyolefin resin is obtained by melt-kneading an epoxy group-containing vinyl monomer and an aromatic vinyl monomer in the presence of a radical polymerization initiator with respect to a polyolefin resin. It is related with the solar cell backsheet characterized by these.

  As a preferred embodiment, the present invention further relates to a solar cell backsheet characterized by further containing (C) a weather resistant film.

  As a preferred embodiment, (C) the weather resistant film is made of at least one resin selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyethylene fluoride, polyethylene difluoride, polymethyl methacrylate, and acrylic resin. It is related with the solar cell backsheet characterized by the above-mentioned.

  Furthermore, this invention relates to the solar cell module using the said solar cell backsheet.

  Since the back sheet of the present invention comprises a modified clay film and an adhesive film, a solar cell back sheet excellent in water vapor barrier properties and adhesiveness with EVA as a sealing material can be provided. Furthermore, since it is not necessary to use a primer, it has the advantage of being inexpensive.

It is a figure of the back seat concerning Example 3 of the present invention.

  The present invention is described in detail below.

  The solar cell backsheet of the present invention is a solar cell backsheet in which (A) a modified clay film and (B) an adhesive film are laminated, and (A) the modified clay film is a silylating agent on clay. And a modified clay containing any one of polyamide and polyimide as an additive, and at least 90 mol% of the exchangeable ions of the modified clay are lithium ions.

  The (A) modified clay film of the present invention will be described in detail below.

  The clay used for the modified clay is at least one selected from the group consisting of mica, vermiculite, montmorillonite, beidellite, saponite, hectorite, stevensite, magadiite, isralite, kanemite, illite, and sericite. preferable. Natural products, synthetic products, and mixtures thereof can be used.

  The modified clay is preferably a reaction product of the clay and the silylating agent. Examples of silylating agents include methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, and octadecyltrimethoxysilane. Is done.

  Some silylating agents have reactive functional groups such as epoxy groups, acrylic groups, amino groups, and halogen groups. Silylated clays prepared using such silylating agents have reactive ends. Have. In this case, a chemical reaction such as an addition reaction, a condensation reaction, or a polymerization reaction is performed during the film formation or after the film formation to generate a new chemical reaction, and the light transmittance, gas barrier property, water vapor barrier property, or mechanical It is possible to improve the mechanical strength. In particular, when the silylated clay has an epoxy group, it is possible to form a covalent bond between the clays by an epoxy reaction during or after the film formation.

  The weight of the silylating agent is preferably 1 to 30% by weight based on the total weight of clay and silylating agent.

  Examples of the method for introducing the silylating agent into the clay include a method of mixing clay and about 2% by weight of the silylating agent with respect to the clay, and milling with a ball mill for 1 hour.

  In the modified clay, the interlayer ions are preferably lithiated. By lithiation, the interlayer lithium moves into the clay octahedral layer, and the ionic component between the layers decreases, thereby improving the water resistance. This improvement in water resistance is conspicuous when the lithium ion is 90 mol% or more of the ionic substances between the layers, and is preferably 90 mol% or more. When such a modified clay is used, a modified clay film having excellent water vapor barrier properties can be obtained.

  As a lithiation method, denatured clay is added to an aqueous lithium nitrate solution, shaken, mixed and dispersed, solid-liquid separated, washed with a water / ethanol mixed solvent, removed unnecessary salt, and then heat-treated. There is a way. The heat treatment is usually performed after film formation, and the temperature condition is usually preferably 230 ° C. or higher, more preferably 300 ° C. or higher, and most preferably 350 ° C. or higher. Exceeding 800 ° C. is not preferable because clay deteriorates. If the temperature is too low, heat treatment for a long time is required, which is not preferable. The heat treatment time is within 20 minutes to 24 hours.

  As a method for measuring the lithium ion concentration, there is a method in which sodium ions and lithium ions are quantified by elemental analysis such as atomic absorption analysis, and mol% of lithium ions is calculated.

  Additives include general-purpose resins such as polyamide, polyimide, polyamic acid (polyamic acid), polycarbonate, polyether ether ketone (PEEK), polyphenylene ether (PPE), polyethylene, polypropylene, polyvinyl chloride, polystyrene, ABS resin, and PET. Thermosetting resins such as phenol resin, melamine resin, urea resin, epoxy resin, polyurethane, and unsaturated polyester are known, but polyamide or polyimide is used in the present invention from the viewpoint of improving water vapor barrier properties. The

  As a mixing method of the modified clay and the additive, the modified clay is dispersed in an organic solvent and then the additive is added, the modified clay is dispersed in a solution containing the additive, and the modified clay and the additive are separately dispersed. And a method of mixing them. Among these, a method of adding an additive after dispersing the modified clay in an organic solvent and a method of mixing the modified clay and the additive separately and mixing them are preferable in terms of ease of dispersion.

  A method of adding the additive after dispersing the modified clay in an organic solvent will be described below. First, denatured clay is added to an organic solvent to prepare a dilute and uniform denatured clay dispersion. The modified clay concentration is preferably 0.3 to 15% by weight, and more preferably 1 to 10% by weight. If the modified clay concentration is too low, drying takes time, which is not preferable. If the concentration is too high, the denatured clay will not be dispersed well, and lumps are likely to occur, a uniform film cannot be formed, and cracking due to shrinkage, surface roughness, non-uniform film thickness, etc. will occur during drying. Moreover, it is preferable that the viscosity of the dispersion liquid before film forming is 1-30 Pa.s, and it is more preferable that it is 1-20 Pa.s.

  Next, an additive is added to the modified clay dispersion to prepare a uniform dispersion. Modified clays and additives are well dispersed in certain organic solvents. In addition, since the modified clay and the additive have an affinity for each other, when both are mixed in a solution, they easily interact and complex.

  The weight ratio of the additive to the total solid (the total amount of the modified clay and the additive) is preferably 1 to 30% by weight, and more preferably 5 to 20% by weight. If the proportion of the additive is too low, the modified clay film does not exhibit flexibility and mechanical strength, which is not preferable. When the ratio of the additive is too high, the heat resistance of the modified clay film is lowered, which is not preferable.

  The organic solvent to be used is preferably one in which the modified clay is dispersed and the additive is dissolved, and examples thereof include ethanol, ether, dimethylformamide, dimethylacetamide, tetrahydrofuran, acetone, and toluene.

  Examples of the dispersion method include a method using a stirrer equipped with a stirring blade, a shaker stirrer, a homogenizer, and the like. In order to reduce small lumps, it is preferable to use a homogenizer at the final stage of dispersion. The presence of lumps in the dispersion is not preferable because it leads to surface roughness of the moisture-proof film and uneven composition.

  If necessary, it is preferable to degas the dispersion. When the deaeration process is not performed, pores derived from bubbles may be generated. As a method of deaeration treatment, there are methods such as vacuum drawing, heat treatment, and centrifugal treatment, and a method including vacuum drawing is preferable.

  Next, after applying the dispersion to the surface of the support with a certain thickness, the solvent is evaporated, and the remainder is formed into a film. As the support, those made of polytetrafluoroethylene, polypropylene, or brass are preferable in terms of peelability. The support surface is preferably flat. If it is not flat, the surface roughness of the support is transferred, which is not preferable.

  Furthermore, it is preferable to carry out a drying treatment. It is preferable to dry by heating evaporation method, centrifugation, filtration, vacuum drying, freeze vacuum drying, or a combination of these methods. In the case of the heat evaporation method, the temperature is preferably from room temperature to 90 ° C, and preferably from 30 to 60 ° C. The drying time is preferably about 10 minutes to 24 hours. If the temperature is too low, the drying time becomes longer, which is not preferable. If the temperature is too high, convection of the dispersion occurs, the film thickness becomes non-uniform, and the degree of orientation of the modified clay decreases, which is not preferable.

  In the (A) modified clay film of the present invention, the modified clay particles need to be highly oriented. High orientation means that unit structure layers (thickness of 1 to 1.5 nm) of modified clay particles are stacked with the direction of the layer surface being the same, and high periodicity is given in a direction perpendicular to the layer surface. Defined as a thing. In order to obtain such a high degree of orientation, a thin and uniform dispersion containing modified clay and additives is applied to a support, the dispersion medium is slowly evaporated, and the modified clay particles are densely laminated. It is important to form the film. As suitable conditions for this film formation, the concentration of the modified clay in the dispersion is preferably 0.3 to 15 wt%, more preferably 1 to 10 wt%. Moreover, as drying conditions by a heating evaporation method, it is preferable that it is room temperature to 90 degreeC, and it is preferable that it is 30-60 degreeC.

(A) The water vapor permeability (40 ° C., 90% RH) of the modified clay film is preferably 0.000001 to 0.2 g / (m ² · day). A high moisture permeability is not preferable because moisture penetration into the cell cannot be suppressed and deterioration is caused. As a method for measuring the water vapor transmission rate (40 ° C., 90% RH), there is a method described in JIS K 7129.

(A) The modified clay film has flexibility and mechanical strength that can be used as a self-supporting film, can be used without bending with a bending radius of 3 mm, and has a permeability coefficient of 4.0 for oxygen gas. It is preferable that it is less than x10 <^-15> cm < ² > s < ^-1 > cmHg < ^-1 . (A) The thickness of the modified clay film is preferably 3 to 100 μm, and more preferably 3 to 80 μm. Furthermore, it is preferable that no visual damage is observed in the film shape after being immersed in superheated water at 150 ° C. for 1 hour. Furthermore, in thermogravimetry, the 5% weight loss temperature is preferably 300 ° C to 760 ° C.

  (B) Examples of adhesive films include modified polyolefin resins, acrylic resins, urethane resins, polyester resins, silicone resins, polyisobutylene resins, ethylene-vinyl alcohol copolymers (EVOH), and ethylene-vinyl acetate. A copolymer (EVA) etc. are illustrated. Among these, (A) From the viewpoint of adhesiveness with the modified clay film and adhesiveness with EVA as a sealing material, it is preferably a modified polyolefin resin, and particularly preferably an epoxy-modified polyolefin resin. . Since the epoxy-modified polyolefin resin has an epoxy group, it is particularly excellent in adhesiveness with the (A) modified clay film.

  The epoxy-modified polyolefin resin is not particularly limited as long as it is modified with a compound containing an epoxy group, and examples thereof include glycidyl methacrylate-modified polyolefin.

  The epoxy-modified polyolefin resin is an epoxy-modified polyolefin resin obtained by melt-kneading an epoxy group-containing vinyl monomer and an aromatic vinyl monomer in the presence of a radical polymerization initiator with respect to a polyolefin resin. It is preferable.

  Examples of the polyolefin resin include polyethylene, polypropylene, poly-1-butene, polyisobutylene, polymethylpentene, propylene-ethylene copolymer, ethylene-propylene-diene copolymer, ethylene / butene-1 copolymer, Examples thereof include an ethylene / octene copolymer and a copolymer of cyclopentadiene and ethylene and / or propylene. Among these, polyethylene, polypropylene, and propylene-ethylene copolymer are preferable because they can be easily modified.

  Examples of the epoxy group-containing vinyl monomer include glycidyl methacrylate (GMA), glycidyl acrylate, monoglycidyl maleate, diglycidyl maleate, allyl glycidyl ether, and methacryl glycidyl ether. Among these, glycidyl methacrylate is preferable in that it is inexpensive. Said epoxy group containing vinyl monomer can be used individually or in mixture of 2 or more types.

  The addition amount of the epoxy group-containing vinyl monomer is preferably 0.1 to 50 parts by weight, and more preferably 1 to 30 parts by weight with respect to 100 parts by weight of the polyolefin resin. If the amount added is too small, the adhesiveness is not sufficiently exhibited, which is not preferable. If the addition amount is too large, the heat resistance of the resulting epoxy-modified polyolefin resin composition is lowered, or the melt flow rate (MFR) is too low to make a film, which is not preferable.

  Examples of the aromatic vinyl monomer include styrene, p-methylstyrene, α-methylstyrene p-chlorostyrene, p-hydroxystyrene, divinylbenzene, diisopropenylbenzene and the like. Among these, styrene is preferable in that it is inexpensive. Said aromatic vinyl monomer can be used individually or in mixture of 2 or more types.

  The addition amount of the aromatic vinyl monomer is preferably 0.1 to 50 parts by weight, and more preferably 1 to 30 parts by weight with respect to 100 parts by weight of the polyolefin resin. If the amount added is too small, the graft ratio of the epoxy group-containing vinyl monomer to the polyolefin resin tends to be inferior, which is not preferable. If the amount added is too large, the grafting efficiency of the epoxy group-containing vinyl monomer reaches the saturation range, so it is preferable to set the upper limit to 50 parts by weight.

  Examples of radical initiators include ketone peroxides such as methyl ethyl ketone peroxide and methyl acetoacetate peroxide, 1,1-bis (t-butylperoxy) cyclohexane, and 2,2-bis (t-butylperoxy) butane. Hydroperoxides such as peroxyketal, diisopropylbenzene hydroperoxide, cumene hydroperoxide, dicumyl peroxide, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide Peroxydicarbonates such as dialkyl peroxides, di (3-methyl-3-methoxybutyl) peroxydicarbonate, di-2-methoxybutylperoxydicarbonate, and t-hexylperoxybenzoe DOO, t- butyl peroxybenzoate, and the like peroxyesters such.

  Said radical initiator can be used individually or in mixture of 2 or more types.

  The addition amount of the radical polymerization initiator is preferably 0.01 to 10 parts by weight and more preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. Less than 0.01 parts by weight is not preferable because the modification reaction does not proceed sufficiently. If the amount exceeds 10 parts by weight, the fluidity and mechanical properties of the resulting epoxy-modified polyolefin resin are lowered, which is not preferable.

  A thermoplastic resin, an elastomer, a tackifier (tackifier), a plasticizer, a process oil, or the like may be added to the epoxy-modified polyolefin resin as necessary.

  Further, if necessary, an antioxidant, an ultraviolet absorber, a chain transfer agent, a nucleating agent, a lubricant, a filler, a pigment, a flame retardant, an antistatic agent, and the like may be added.

  About the addition method at the time of melt-kneading, it is preferable to melt-knead by adding an epoxy group-containing vinyl monomer and an aromatic vinyl monomer to a mixture obtained by melt-kneading a polyolefin resin and a radical polymerization initiator. In this case, the production | generation of the low molecular weight body which does not contribute to a graft can be suppressed.

  The processing temperature at the time of melt kneading is preferably 130 to 300 ° C. In the case of 130 ° C. to 300 ° C., the polyolefin resin is sufficiently melted and hardly thermally decomposed.

  Further, the kneading time, that is, the time after mixing the radical polymerization initiator is preferably usually 30 seconds to 60 minutes.

  For melt kneading, an extruder, a Banbury mixer, a kneader, a mill, a heating roll, or the like can be used. From the viewpoint of productivity, it is preferable to use a single-screw or twin-screw extruder. Moreover, in order to improve the miscibility and dispersibility of various raw materials, you may use together the said melt-kneading apparatus.

  Since the epoxy-modified polyolefin-based resin forms a multiphase structure in which a phase composed of an epoxy group-containing vinyl monomer and an aromatic vinyl monomer is finely dispersed in a phase composed of a polyolefin-based resin, (A) a modified clay film Especially excellent in adhesion.

  (B) Although the manufacturing method of an adhesive film is not specifically limited, For example, various extrusion molding machines, calendar molding machines, inflation molding machines, roll molding machines, or hot press molding machines are used for adhesive resins. Can be formed into a film using

  (B) The thickness of the adhesive film is preferably 10 to 500 μm, and more preferably 50 to 200 μm. If it is thinner than 10 μm, sufficient insulation cannot be obtained, and if it is too thick, it is not preferable in terms of cost.

  Furthermore, in the present invention, it is preferable to laminate (C) a weather resistant film. (C) Examples of weather resistant films include polyethylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polycarbonate, polymethyl methacrylate, an acrylic resin composition comprising an acrylic graft copolymer and a methacrylic polymer. And a film made of at least one resin selected from a product, polyimide, polyethylene fluoride, and polyethylene difluoride. Among these, a film made of at least one resin selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyethylene fluoride, polyethylene difluoride, polymethyl methacrylate, and acrylic resin is preferable. Since the back sheet is directly exposed to the outdoors, weather resistance (UV light, moisture resistance, heat resistance, salt damage resistance, etc.) is required. By using these weather resistant films, weather resistance is imparted to the back sheet. can do.

  Specific examples of the back sheet for solar cell of the present invention include (A) modified clay film / (B) adhesive film, (C) weather resistant film / (B) adhesive film / (A) modified clay, for example. Film / (B) adhesive film.

  The manufacturing method of the solar cell backsheet of this invention can use a well-known method, and can bond together by well-known methods, such as dry lamination, wet lamination, non-solvent lamination, extrusion lamination.

  The backsheet of the present invention can be suitably used for any solar cell, but can be particularly suitably used for an amorphous silicon solar cell, a crystalline silicon solar cell, a hybrid solar cell, or the like. Examples of the location of the solar cell include the roof, the rooftops of buildings, factories, schools, public facilities, etc., wall surfaces, coasts, and desert areas.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by these Examples.

Production Example 1 Production Method of Modified Clay Film A1 Natural purified bentonite, Kunipia F (manufactured by Kunimine Industries Co., Ltd.) was dried in an oven set at a temperature of 110 ° C. or higher. 300 g of the bentonite was placed in a ball mill pod together with alumina balls. Furthermore, after adding 6 g of a silylating agent having an amino group at the terminal, Silaace S330 (manufactured by Chisso Corporation), the inside of the pod was replaced with nitrogen gas, and ball milling was performed for 1 hour to obtain a modified clay.

  24 g of the modified clay was added to 400 ml of a 0.5 N aqueous lithium nitrate solution, and mixed and dispersed by shaking. The dispersion ions were shaken and dispersed until the lithium ions reached 95% (confirmed by atomic absorption analysis), and the interlayer ions of the clay were exchanged with lithium ions. Solid-liquid separation was performed by centrifugation, and the resulting solid was washed with a mixed solvent of 280 g of distilled water and 120 g of ethanol to remove excess salt. This washing operation was repeated twice or more. The obtained product was sufficiently dried in an oven and then crushed to obtain a lithium exchanged modified clay.

  10 g of the lithium-exchanged denatured clay was put in a container, 20 ml of pure water was added, and the mixture was allowed to stand for about 10 minutes and allowed to adjust to pure water. Then, it lightly kneaded with a stainless steel spatula. The mixing process was performed with a mixer at 2000 rpm for 10 minutes. Furthermore, 20 ml of pure water was added and kneaded so that pure water was spread throughout, and kneaded until the whole was united. The mixing process was performed with a mixer at 2000 rpm for 10 minutes. Furthermore, 50 ml of pure water was added and well kneaded with a stainless steel spatula. If there was a big lump (gel lump), it was crushed as much as possible. A clay pregel was obtained by mixing with a mixer at 2000 rpm for 10 minutes.

  The pregel was dispersed in dimethylacetamide using a homogenizer, ULTRA TURRAX T50 (manufactured by IKA). In a suitable container, 35 times equivalent amount (350 g) of dimethylacetamide to clay was added, and the clay pregel was added while stirring with a homogenizer. Stir at 7000 rpm for 30 minutes. After the homogenizer treatment, 120 g of the dispersion was dispensed into another container. 4.76 g of polyimide varnish and U-varnish A (manufactured by Ube Industries, Ltd.) were added. Defoaming was performed with a mixer at 2000 rpm for 10 minutes and in a defoaming mode at 2200 rpm for 10 minutes. At this time, the viscosity was 1.4 Pa · s (manufactured by Toki Sangyo Co., Ltd., TVB-22L). Thereafter, the paste was poured into a polytetrafluoroethylene sheet, and the paste was stretched with a casting knife so as to have a uniform thickness. The thickness of the paste was 1 mm.

  Next, the paste was dried in a forced convection oven at a temperature of 60 ° C. for 24 hours, peeled from the polytetrafluoroethylene sheet, and heat-treated in a heating furnace. In this heat treatment, the temperature was raised to 150 ° C. at a rate of 100 ° C./hour, and then held at 150 ° C. for 2 hours. Next, the temperature was raised to 230 ° C. at a rate of 100 ° C./hour, and then maintained at 230 ° C. for 24 hours. By this heat treatment, a modified clay film having a thickness of 20 μm was obtained.

The water vapor permeability (40 ° C., 90% RH) of the obtained modified clay film was 0.03 g / (m ² · day). As a result of measuring the flexibility using a mandrel type bending tester, defects such as cracks did not occur even when the modified clay film was bent to a diameter of 2 mm. As a result of thermal analysis, the 5% weight loss temperature was 500 ° C. The heating rate was 10 ° C./min, and it was carried out under a normal air flow atmosphere.

(Production Example 2) Production method of epoxy-modified polyolefin resin film B1 Propylene-ethylene copolymer (Versify 3401, MFR8, manufactured by Dow Chemical) 100 parts by weight, 1,3-di (t-butylperoxyisopropyl) benzene (Nippon Yushi Co., Ltd .: Perbutyl P, 1 minute half life 175 ° C.) Supply 0.5 parts by weight to a twin screw extruder (TEX30: L / D = 28, manufactured by Nippon Steel) After melt-kneading, 5 parts by weight of glycidyl methacrylate and 5 parts by weight of styrene were then added from the middle of the cylinder and melt-kneaded to obtain pellets made of an epoxy-modified polyolefin resin. The MFR after denaturation was 6. The obtained resin was supplied to a T die to obtain a film having a thickness of 100 μm.

Production Example 3 Production Method of Epoxy-Modified Polyolefin Resin Film B2 Homopolypropylene (S119, MFR60, Prime Polymer Co., Ltd.) 100 parts by weight, 1,3-di (t-butylperoxyisopropyl) benzene (Nippon Yushi) Co., Ltd .: Perbutyl P, half-life of 175 ° C for 1 minute) 0.5 parts by weight was supplied to a twin screw extruder (TEX30: L / D = 28, manufactured by Nippon Steel) and melt kneaded. Thereafter, 5 parts by weight of glycidyl methacrylate and 5 parts by weight of styrene were added from the middle of the cylinder and melt-kneaded to obtain pellets made of an epoxy-modified polyolefin resin composition. The MFR after denaturation was 88. The obtained resin composition was supplied to a T die to obtain a film having a thickness of 100 μm.

Example 1
In a state where the modified clay film A1 and the epoxy-modified polyolefin resin film B1 were overlapped, heat pressing was performed to obtain a laminated film. In order to examine the adhesiveness to EVA, the laminated film and EVA (thickness 0.4 mm) were hot-pressed in a state where the epoxy-modified polyolefin resin film B1 and EVA were in contact with each other to obtain a laminated film. . The hot press conditions were 170 ° C. or 200 ° C., pressure 5 MPa, press time 3 minutes (no pressure 1 minute, pressurization 2 minutes).

(Example 2)
A laminated film was obtained in the same manner as in Example 1 except that the epoxy-modified polyolefin resin film B1 was replaced with the epoxy-modified polyolefin resin film B2.

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1 except that the epoxy-modified polyolefin resin film B1 was replaced with a 100 μm-thick propylene-ethylene copolymer (Versify 3401, MFR = 8, manufactured by Dow Chemical) film.

(Comparative Example 2)
A laminated film was obtained in the same manner as in Example 1 except that the epoxy-modified polyolefin resin film B1 was replaced with a 100 μm thick homopolypropylene (S119, MFR60, manufactured by Prime Polymer Co., Ltd.) film.

(1) Adhesive evaluation method The edge part of the laminated film obtained by said method was grasped by hand, and it was investigated whether it could peel off by hand. ○ It does not peel off by hand. × Easy to peel off by hand.

  Examples 1 and 2 use an epoxy-modified polyolefin resin film as the adhesive film, and are excellent in adhesion to the modified clay film and EVA. On the other hand, Comparative Examples 1 and 2 use a polyolefin-based resin instead of the adhesive film, and have insufficient adhesion to the modified clay film and EVA.

(Production Example 3) Production Method of Back Sheet BS1 PET film (Lumirror S10, thickness 75 μm, manufactured by Toray Industries, Inc.), epoxy-modified polyolefin resin film B1, modified clay film A1, and epoxy-modified polyolefin resin film B1 are stacked. Then, a 6-inch roll heated to 170 ° C. (test mixing roll 191-TM, manufactured by Yasuda Seiki Seisakusho Co., Ltd.) was used for lamination to obtain a back sheet.

(Example 3)
In advance, the EVA sheet having a thickness of 0.4 mm and the back sheet BS1 are stacked on the back surface of the 5 inch size amorphous silicon solar cells connected by wiring, and after vacuum lamination molding at 170 ° C. for 7 minutes, in an oven at 150 ° C., A solar cell module (5 inches) was produced by heating for 120 minutes.

(Comparative Example 3)
A solar cell module (5 inches) was produced in the same manner as in Example 3 except that the back sheet BS1 was changed to the modified clay film A1.

(2) Evaluation method of module appearance The module appearance after molding was visually determined. Bubbles: No, Yes, cracks: No, No, Coloring: No, No

(3) Evaluation method of adhesiveness (vs. EVA) Adhesiveness with EVA was simply evaluated. ○ Cannot be easily peeled off by hand, × Can be easily peeled off by hand.

(4) Evaluation method of Pmax (maximum output) Pmax was measured using a two-lamp solar simulator.

  Example 3 is a back sheet containing a modified clay film, an adhesive film, and a weather resistant film. An epoxy-modified polyolefin resin film was used as the adhesive film, and the adhesiveness with EVA was good. The module appearance and Pmax (initial value) were good.

a1. Modified clay film b1. Epoxy-modified polyolefin resin film c1. PET film

Claims (14)

(A) A solar cell backsheet obtained by laminating a modified clay film and (B) an adhesive film, wherein (A) the modified clay film is obtained by reacting a clay with a silylating agent, and an additive As a back sheet for a solar cell, comprising at least 90 mol% of exchangeable ions of a modified clay containing either one of polyamide or polyimide. ^2. The solar cell according to claim 1, wherein the modified clay film has a water vapor permeability (40 ° C., 90% RH) of 0.000001 to 0.2 g / (m ² · day). Back sheet. The backsheet for a solar cell according to claim 1 or 2, wherein the weight of the silylating agent of the modified clay is 1 to 30% by weight based on the total weight of the clay and the silylating agent. (A) The weight of the additive of the modified clay film is 5 to 20% by weight based on the total weight of the modified clay and the additive, The sun according to any one of claims 1 to 3 Battery backsheet. The clay used for the modified clay is at least one clay selected from the group consisting of mica, vermiculite, montmorillonite, beidellite, saponite, hectorite, stevensite, magadiite, isralite, kanemite, illite, and sericite. The solar cell backsheet according to any one of claims 1 to 4, wherein: (A) The modified clay film has flexibility and mechanical strength that can be used as a self-supporting film, can be used without bending with a bending radius of 3 mm, and has a permeability coefficient of 4.0 for oxygen gas. × 10 ^-15 cm ² s ^-1 backsheet for a solar cell according to any one of claims 1 to 5, characterized in that cmHg less than ^-1. (A) The thickness of a modified clay film is 3-100 micrometers, The solar cell backsheet of any one of Claims 1-6 characterized by the above-mentioned. (A) In the thermogravimetric measurement of the modified clay film, the 5% weight loss temperature is 300 ° C to 760 ° C, The solar cell backsheet according to any one of claims 1 to 7. (B) Adhesive film is modified polyolefin resin, acrylic resin, urethane resin, polyester resin, silicone resin, polyisobutylene resin, ethylene-vinyl alcohol copolymer (EVOH), ethylene-vinyl acetate co It is at least 1 sort (s) chosen from the group which consists of a polymer (EVA), The solar cell backsheet in any one of Claims 1-8 characterized by the above-mentioned. The solar cell backsheet according to any one of claims 1 to 9, wherein the modified polyolefin resin is an epoxy-modified polyolefin resin. The epoxy-modified polyolefin resin is obtained by melting and kneading an epoxy group-containing vinyl monomer and an aromatic vinyl monomer in the presence of a radical polymerization initiator with respect to a polyolefin resin. 10. The solar cell backsheet according to 10. The solar cell backsheet according to claim 1, further comprising (C) a weather resistant film. (C) The weather resistant film is a film made of at least one resin selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyethylene fluoride, polyethylene difluoride, polymethyl methacrylate, and acrylic resin. The solar cell backsheet according to claim 12, which is characterized by: The solar cell module using the solar cell backsheet of any one of Claims 1-13.

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