JP6364882B2 - Solar cell module sealing material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solar cell module sealing material and a method for manufacturing the same.

  As a sealing material for a solar cell module, a configuration using EVA (ethylene-vinyl acetate copolymer) as a base resin and containing a crosslinking agent and a crosslinking aid is known. In this case, the above composition is generally heated at a low temperature of 50 ° C. to 90 ° C. because if the crosslinking reaction proceeds during extrusion molding, the load during molding becomes excessive and the productivity decreases or becomes impossible to mold. Extruded to form uncrosslinked. Then, usually, after forming, an annealing treatment for stress relaxation is performed, and then crosslinking is performed by a modularization process by vacuum heating lamination or a subsequent heating process.

  On the other hand, a polyethylene resin-based sealing material is also known in order to solve the problem of reduced water vapor barrier properties, which is a drawback of EVA.

In Patent Document 1, a resin composition containing a polyethylene resin having a density of 0.900 g / cm ³ or less and a polymerization initiator contained in the composition by 0.02% by mass or more and less than 0.5% by mass is melted. A method for producing a solar cell module encapsulant to be molded is disclosed, and by forming a small amount of a crosslinking agent at a high temperature, a so-called weak crosslink is formed at the time of film formation, resulting in a cross-linked process. No cross-linking treatment is required.

Patent Document 2 discloses an uncrosslinked sealing material sheet by melt-molding a sealing material composition containing low density polyethylene having a density of 0.900 g / cm ³ or less, a crosslinking agent, and a crosslinking aid. A method for producing a sealing material for a solar cell module, comprising: a sheet forming step; and a crosslinking step of crosslinking the uncrosslinked sealing material sheet so that the gel fraction is 2% or more and 80% or less. As disclosed in Patent Document 1, a crosslinked sealing material that does not require a crosslinking treatment in a subsequent modularization process is obtained.

  Patent Document 3 discloses a sealing material for a solar cell module, which has a multilayer configuration of an intermediate layer and both outermost layers sandwiching the intermediate layer, and have different MFRs.

WO2011 / 152314 International Publication Pamphlet JP 2012-248605 A JP 2008-117925 A

  The weakly cross-linked sealing material of Patent Document 1 has both film-forming properties and heat resistance when used as a solar cell module, but there is a demand for further improvement in heat resistance.

  The crosslinked sealing material of Patent Document 2 can improve heat resistance by a subsequent crosslinking step. However, as a sealing material excellent in cell crack prevention and uneven follow-up in the laminating process at the time of modularization, especially in the outermost layer of the sealing material that becomes the laminating surface, it has flexibility during the laminating process, After lamination, there is a conflicting requirement to have heat resistance at a temperature 30 degrees or more higher than the melting point of the base material resin, and further improvement has been required.

  When the method of Patent Document 3 is applied to a material system using polyethylene as a main raw material (not including vinyl acetate), the outer layer is highly fluidized, so the film forming property is limited due to the problem of adhesive strength to the cooling roll. There's a problem.

  In the multilayer structure, the inventors of the present invention form a weak crosslink using a small amount of the second cross-linking agent in the intermediate layer at the time of film formation, and the outermost layer does not contain a small amount or substantially no cross-linking agent. The film is formed in the configuration, and then the surface is coated and impregnated with the first crosslinking agent, so that the film forming property in the film forming step, the above flexibility in the modularization step, and the sufficient crosslinking in the subsequent modularization step. The inventors have found that the heat resistance can be improved with the treatment, and the present invention has been completed. More specifically, the present invention provides the following.

(1) A multilayer solar cell module seal comprising 90% by mass or more of a polyethylene resin having a density of 0.900 g / cm ³ or less, and comprising at least an intermediate layer and an outermost layer disposed on both sides of the intermediate layer. Stopping material,
The solar cell module sealing material is:
The MFR at 190 ° C. and a load of 2.16 kg measured according to JIS K7210 of the intermediate layer is 1.5 g / 10 min or less,
The intermediate layer substantially does not contain a first cross-linking agent having a half-life temperature of 130 ° C. or higher and lower than 170 ° C. for 1 minute,
MFR at 190 ° C. and a load of 2.16 kg measured according to JIS K7210 of the outermost layer is 0.2 g / 10 min or more and 10 g / 10 min or less,
The outermost layer contains the first crosslinking agent,
In all layers of the solar cell module encapsulant, the first cross-linking agent is contained in an amount of 0.1% by mass to 0.3% by mass,
The encapsulant after crosslinking when the encapsulant for solar cell module is heated at 130 ° C. for 15 minutes and cured at 150 ° C. for 20 minutes,
The MFR at 190 ° C. and a load of 2.16 kg measured according to JIS K7210 of the intermediate layer is 1.5 g / 10 min or less,
A solar cell characterized in that the MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS K7210 of the outermost layer is 0.4 g / 10 min or less and substantially does not contain the first cross-linking agent. Module sealant.

  (2) The sealing material for solar cell modules according to (1), wherein the gel fraction of all layers of the sealing material for solar cell modules before crosslinking is 0% or more and less than 1%.

  (3) The sealing material for solar cell modules according to (1) or (2), wherein the gel fraction of all layers of the post-crosslinking sealing material is 1% or more and 40% or less.

  According to the solar cell module sealing material of the present invention, the film-forming property in the film-forming process, the unevenness followability due to the flexibility in the modularization process, and the heat resistance improvement due to sufficient crosslinking treatment in the subsequent modularization process Side by side becomes possible.

It is sectional drawing which shows an example of the laminated constitution about the solar cell module using the sealing material of this invention.

The present invention contains a multilayer resin for solar cell modules, comprising a polyethylene resin having a density of 0.900 g / cm ³ or less of 90% by mass or more, comprising an intermediate layer and outermost layers disposed on both sides of the intermediate layer. Stopping material,
The solar cell module encapsulant has an MFR of 1.5 g / 10 min or less at 190 ° C. and a load of 2.16 kg measured according to JIS K7210 of the intermediate layer. Not contained in. The MFR of the outermost layer is 0.2 g / 10 min or more and 10 g / 10 min or less, and the first cross-linking agent having a half-life temperature of 1 minute existing in the outermost layer of 130 ° C. or more and less than 170 ° C. is a mass ratio in all layers. It contains 0.1% by mass or more and 0.3% by mass or less. The encapsulant after crosslinking when heated at 130 ° C. for 15 minutes and cured at 150 ° C. for 20 minutes has an MFR of the intermediate layer of 1.5 g / 10 min or less, and the MFR of the outermost layer is 0.4 g / 10 min or less, and substantially does not contain the first cross-linking agent. First, an example of the manufacturing method of the solar cell module sealing material of the present invention will be described, and then the solar cell module sealing material of the present invention will be described.

<Manufacturing method>
An example of the manufacturing method of the sealing material for solar cell modules of this invention is (A) 90 mass% or more of polyethylene resin with a density of 0.900 g / cm ³ or less, and 0.02 mass% or more in the composition 0 An intermediate layer resin composition containing a second crosslinking agent containing less than 5 mass% and having a half-life temperature of 1 minute to 160 ° C. to 200 ° C., and a polyethylene resin having a density of 0.900 g / cm ³ or less. A step of obtaining a multilayer substrate sheet by melt-molding an outermost resin composition containing at least mass% and containing substantially no cross-linking agent at a temperature equal to or higher than the 1-minute half-life temperature of the second cross-linking agent; (B) on both surfaces of the substrate sheet, the first crosslinking agent 0.25 g / ^{m 2} or more 3.0 g / ^{m 2} or less of coating weight of less than 170 ° C. one-minute half-life temperature 130 ° C. or higher, i.e. in both total 0.5 g / ^{m 2} or more 6.0 g / ^{m 2} or less of the coating A step of applying an amount consists. Hereinafter, the respective steps will be described in order.

<(A) The process of obtaining a base material sheet>
<Interlayer resin composition>
An intermediate layer resin composition for producing an intermediate layer of a multilayer substrate sheet has 90% or more of a polyethylene resin having a density of 0.900 g / cm ³ or less and a second crosslinking agent as essential components. contains.

[Polyethylene resin]
As the base resin, low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less, preferably linear low density polyethylene (LLDPE) is used in the present invention. The linear low density polyethylene is a copolymer of ethylene and α-olefin, and in the present invention, the density is 0.900 g / cm ³ or less, preferably 0.870 to 0.890 g / cm ³ . is there. If it is this range, favorable transparency and heat resistance can be provided, maintaining sheet workability.

  In the present invention, it is preferable to use a metallocene linear low density polyethylene. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform distribution of comonomer. For this reason, molecular weight distribution is narrow and it is possible to make it the above ultra-low density. In addition, since the crystallinity distribution is narrow and the crystal sizes are uniform, not only a large crystal size does not exist, but also the crystallinity itself is low due to the low density. For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, even if the sealing material for solar cell modules of the present invention is disposed between the transparent front substrate and the solar cell element, the power generation efficiency is hardly lowered.

  As the α-olefin of the linear low density polyethylene, an α-olefin having no branch is preferably used. Among these, 1-hexene and 1-heptene which are α-olefins having 6 to 8 carbon atoms are preferable. Or 1-octene is particularly preferably used. When the α-olefin has 6 to 8 carbon atoms, the solar cell module sealing material can be provided with good flexibility and good strength. As a result, the adhesiveness between the solar cell module sealing material and the base material is increased, and moisture can be prevented from entering between the solar cell module sealing material and the base material.

  The melt mass flow rate (MFR) of the polyethylene resin is preferably 1.0 g / 10 min or more and 40 g / 10 min or less at 190 ° C. and a load of 2.16 kg, and more preferably 2 g / 10 min or more and 40 g / 10 min or less. preferable. When the MFR is in the above range, the processability during film formation is excellent.

Unless otherwise specified, MFR in the present specification is a value obtained by the following method.
MFR (g / 10 min): Measured according to JIS K7210. Specifically, the synthetic resin was heated and pressurized at 190 ° C. in a cylindrical container heated by a heater, and the amount of resin extruded per 10 minutes from an opening (nozzle) provided at the bottom of the container was measured. . The test machine used was an extrusion plastometer, and the extrusion load was 2.16 kg.
In addition, about the sealing material sheet which is a multilayer film, it measured by the said process with the multilayer state by which all the layers were laminated | stacked integrally, and the obtained measured value was made into the MFR value of the said multilayer sealing material sheet. .

  The “polyethylene resin” in this specification is obtained by polymerizing not only ordinary polyethylene obtained by polymerizing ethylene but also a compound having an ethylenically unsaturated bond such as α-olefin. Resins, resins obtained by copolymerizing a plurality of different compounds having an ethylenically unsaturated bond, modified resins obtained by grafting different chemical species to these resins, and the like are included.

  Among these, a silane copolymer obtained by copolymerizing at least an α-olefin and an ethylenically unsaturated silane compound as a comonomer can be preferably used. By using such a resin, adhesiveness between a member such as a transparent front substrate or a solar cell element and a solar cell module sealing material can be obtained.

  The silane copolymer is described in, for example, JP-A-2003-46105. By using the copolymer as a component of the solar cell module sealing material composition, it is excellent in strength, durability, etc., and weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance In addition, it has excellent other characteristics, and has extremely excellent heat-sealability without being affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. A solar cell module suitable for the above can be manufactured.

  The silane copolymer is a copolymer obtained by copolymerizing at least an α-olefin and an ethylenically unsaturated silane compound as a comonomer and, if necessary, further using another unsaturated monomer as a comonomer. The modified product or condensate is also included.

Specifically, for example, one or more of α-olefins, one or more of ethylenically unsaturated silane compounds, and, if necessary, one or more of other unsaturated monomers. the door, using the desired reaction vessels, for example, a pressure 500~4000kg / cm ^2-position, preferably, 1000~4000kg / cm ^2-position, a temperature 100 to 400 ° C.-position, preferably, 150 to 350 ° C.-position conditions In the presence of a radical first cross-linking agent and, if necessary, a chain transfer agent, random copolymerization is carried out simultaneously or stepwise, and if necessary, a random copolymer produced by the copolymerization is further produced. The constituent silane compound portion can be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof.

  Examples of the copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof include, for example, one or more α-olefins and, if necessary, other unsaturated monomers. One or more compounds are polymerized simultaneously or stepwise in the presence of a radical first crosslinker and, if necessary, a chain transfer agent, using the desired reaction vessel, as described above, One or more ethylenically unsaturated silane compounds are graft copolymerized with the polyolefin polymer produced by the polymerization, and further, if necessary, a graft copolymer produced by the copolymer is produced. A component of the constituent silane compound may be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof. Kill.

  Examples of the α-olefin include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 1-heptene, 1-octene, One or more selected from 1-nonene and 1-decene can be used.

  Examples of the ethylenically unsaturated silane compound include vinyl trimethoxy silane, vinyl triethoxy silane, vinyl tripropoxy silane, vinyl triisopropoxy silane, vinyl tributoxy silane, vinyl tripentyloxy silane, vinyl triphenoxy silane, vinyl tri One or more selected from benzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be used.

  As the other unsaturated monomer, for example, one or more selected from acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, and vinyl alcohol can be used. Note that vinyl acetate is not included as an unsaturated monomer.

  Examples of radical polymerization initiators include organic peroxides such as lauroyl peroxide, dipropionyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, and t-butyl peroxyisobutyrate. Products, molecular oxygen, azo compounds such as azobisisobutyronitrile azoisobutylvaleronitrile, and the like can be used.

  Examples of the chain transfer agent include paraffinic hydrocarbons such as methane, ethane, propane, butane and pentane, α-olefins such as propylene, 1-butene and 1-hexene, and aldehydes such as formaldehyde, acetaldehyde and n-butyraldehyde. Further, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, aromatic hydrocarbons, chlorinated hydrocarbons, and the like can be used.

  Examples of the method of modifying or condensing the silane compound portion constituting the random copolymer, or the method of modifying or condensing the silane compound portion constituting the graft copolymer include, for example, tin, zinc, iron, lead, Using α-olefin and ethylenically unsaturated silane using metal carboxylate such as cobalt, organometallic compound such as titanate and chelate, organic base, inorganic acid, silanol condensation catalyst such as organic acid, etc. Modification of copolymer of α-olefin and ethylenically unsaturated silane compound by performing dehydration condensation reaction between silanols of the silane compound part constituting the random copolymer or graft copolymer with the compound The method of manufacturing a condensate is mentioned.

  As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used. However, the silane copolymer is more preferably a graft copolymer. A graft copolymer obtained by polymerizing polyethylene for polymerization as a main chain and an ethylenically unsaturated silane compound as a side chain is more preferable. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, the adhesion of the solar cell module sealing material to other members in the solar cell module can be improved.

  As content of the ethylenically unsaturated silane compound at the time of comprising the copolymer of an alpha olefin and an ethylenically unsaturated silane compound, it is 0.001-15 mass% with respect to the total copolymer mass, for example. Preferably about 0.01 to 5% by weight, particularly preferably about 0.05 to 2% by weight. In the present invention, when the content of the ethylenically unsaturated silane compound constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. When it becomes excessive, it tends to be inferior in tensile elongation and heat-fusibility.

The content of the polyethylene resin having a density of 0.900 g / cm ³ or less contained in the intermediate layer resin composition may be 90% by mass or more and 99.9% or more in the sealing material composition. It is preferable. Within that range, other resins may be included. Examples of other resins include other polyethylene resins exceeding 0.900 g / cm ³ , for example. These may be used, for example, as an additive resin, and can be used for masterbatching other components described later.

[Second cross-linking agent]
In the intermediate layer, the content of the cross-linking agent relative to the composition is different from that in the case of the general cross-linking treatment, unlike the case of performing the general cross-linking treatment of the conventionally known sealing material composition for solar cell modules. The second cross-linking agent is used so that the content in a specific range is small. Content of the 2nd crosslinking agent is 0.02 mass% or more and less than 0.5 mass% in the sealing material composition for solar cell modules, Preferably an upper limit is 0.2 mass% or less, More preferably, it is. It is 0.1 mass% or less. If it is less than this range, weak crosslinking of the polyethylene resin does not proceed, heat resistance is insufficient, and transparency is also lowered. Moreover, when it exceeds this range, gel formation will generate | occur | produce during shaping | molding and film forming property will fall.

  The second crosslinking agent has a 1 minute half-life temperature of 160 ° C. or more and 200 ° C. or less. If the half-life temperature for 1 minute is less than 160 ° C., it is not preferable because it is difficult to advance the crosslinking reaction after sufficiently dispersing the second crosslinking agent during molding. If it exceeds 200 ° C., the film forming temperature is required to exceed 230 ° C., which is unsuitable because the base polyethylene-based resin is deteriorated by oxidation or the silane-modified resin is crosslinked.

  As a specific example of the second crosslinking agent, for example, a known radical crosslinking agent can be used. Examples of the radical crosslinking agent include hydroperoxides such as diisopropylbenzene hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; di-t-butyl peroxide, t-butyl cumi Dialkyl such as ruperoxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3 Peroxides; diacyl peroxides such as bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dichlorobenzoyl peroxide; t -Butyl peroxyacetate, t-butyl t-ethyl Hexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2,5-dimethyl-2 Peroxyesters such as 5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate; methyl ethyl ketone peroxide Ketone peroxides such as cyclohexanone peroxide; peroxycarbonates such as t-amyl-peroxy-2-ethylhexyl carbonate and t-butylperoxy 2-ethylhexyl carbonate; organic peroxides such as azobis Sobuchironitoriru, azobis (2,4-dimethylvaleronitrile) azo compounds such as, can be mentioned dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst.

  Of the above, t-butylperoxy 2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and the like can be preferably used. These have a high amount of active oxygen as high as 5% or more, and the 1-minute half-life temperature of the second crosslinking agent is 160 to 200 ° C. and are consumed at the time of molding, so that polyethylene can be efficiently crosslinked.

[Crosslinking aid]
In the intermediate layer resin composition, it is preferable that substantially no crosslinking aid is used. Here, the crosslinking assistant is, for example, a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer, and specifically, triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fuma. Polyallyl compounds such as rate and diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6 -Poly (meth) acryloxy compounds such as hexanediol diacrylate and 1,9-nonanediol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycol Epoxy compounds such as 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, trimethylolpropane polyglycidyl ether and the like containing two or more diyl ethers and epoxy groups Can be mentioned.

  Note that the fact that substantially no crosslinking aid is used means that an amount that does not exhibit a crosslinking effect is within the scope of the present invention even if it is contained in an impurity, and the amount is, for example, in the composition. Is less than 0.01% by mass.

[Other ingredients]
The intermediate layer resin composition may further contain other components. For example, a weather resistance masterbatch for imparting weather resistance to a solar cell module sealing material produced from the solar cell module sealing material composition of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, Components such as heat stabilizers are exemplified. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001 to 5 mass% in the solar cell module encapsulant composition. By including these additives, it is possible to impart a long-term stable mechanical strength, an effect of preventing yellowing, cracking, and the like to the encapsulant composition for solar cell modules.

  A weatherproof masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and adding this to a sealing material composition. Thereby, favorable weather resistance can be provided to the sealing material for solar cell modules. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. The resin used in the weatherproof masterbatch may be a linear low density polyethylene used in the present invention, or other resins described above.

  These light stabilizers, ultraviolet absorbers, heat stabilizers and antioxidants can be used alone or in combination of two or more.

  Furthermore, as other components used in the intermediate layer resin composition, in addition to the above, an adhesion improver such as a silane coupling agent, a nucleating agent, a dispersing agent, a leveling agent, a plasticizer, an antifoaming agent, a flame retardant, etc. Can be mentioned.

<Outermost layer resin composition>
In the outermost resin composition, the base resin contains 90% by mass or more of the same polyethylene-based resin as described above, and the cross-linking agent is 0.01% by mass or less and substantially contains no cross-linking agent. And MFR in 190 degreeC and load 2.16kg measured based on JISK7210 is 0.2 g / 10min or more and 10 g / 10min or less.

<Base material sheet>

  The substrate sheet is obtained by subjecting the above composition to multilayer molding processing by a conventionally known method, and only the intermediate layer is subjected to the above-described weak crosslinking treatment during molding. It is a film. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  As a structure of a base material sheet, it is multilayered by the intermediate | middle layer whose MFR is as low as 1.5 g / 10min or less, and both outermost layers whose MFR is 0.2 g / 10min or more and 10 g / 10min or less. The thickness of the outermost layer is 30 μm or more and 120 μm or less, and the ratio of the thickness of the intermediate layer to the outermost layer other than the outermost layer is as follows: outermost layer: intermediate layer: outermost layer = 1: 3: A range of 1-1: 8: 1 is preferred. By doing in this way, while maintaining the preferable heat resistance as a sealing material, the preferable molding characteristic in an outermost layer can be provided, and also manufacturing cost can be suppressed low.

  The base sheet is formed into a sheet by a multilayer molding method that is usually used in ordinary thermoplastic resins, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. As an example, a method of forming by co-extrusion using two or more melt-kneading extruders can be mentioned. However, in any method, in order to promote the weak crosslinking reaction of the intermediate layer during molding, the molding temperature is preferably the melting point of the polyethylene resin + 50 ° C. or more. Specifically, a high temperature of 150 to 250 ° C. is preferable, and a range of 190 to 230 ° C. is more preferable. As described above, in the present invention, since the addition of the second crosslinking agent is small, the MFR of the intermediate layer is reduced to 1.5 g / 10 min or less, but the degree of the reduction is small. For this reason, weak crosslinking can be advanced during melt molding. And even if it is a small amount of the second crosslinking agent and there is substantially no crosslinking aid, the weak crosslinking of the polyethylene resin proceeds. In addition, since this shaping | molding temperature is more than the 1 minute half life temperature of a 2nd crosslinking agent, a 2nd crosslinking agent hardly remains after shaping | molding. For this reason, the weak crosslinking ends at this molding stage.

The intermediate layer thus weakly crosslinked is characterized in that, from the standpoint of physical properties, i) while maintaining a low density, ii) improved heat resistance but sufficient film forming properties. . Regarding i), the density of the encapsulant for solar cell modules of the present invention does not increase at about 0.900 g / cm ³ or less, which is almost equal to the density of the low-density polyethylene resin that is the main raw material, and before and after melt molding The density difference of the resin composition is within 0.05 g / cm ³ . For this reason, transparency is maintained.

  On the other hand, ii) the heat resistance is such that the MFR is preferably 0.1 g / 10 min or more and less than 1.5 g / 10 min, and preferably the MFR difference of the resin composition before and after melt molding is 1.0 g / 10 min or more and 10.0 g. Since it is / 10 min or less, the heat resistance is improved while being within the range of MFR that can be molded. This is the effect of the weak crosslinking treatment in the present invention. Usually, there is a positive correlation between the MFR and the density of the resin. In the present invention, the MFR can be reduced within the range of the moldable MFR without changing the density of the intermediate layer. .

In addition, the result of the weak crosslinking process of said intermediate | middle layer can also be understood from the gel fraction. The gel fraction of the solar cell module sealing material of the present invention is 25% or less, preferably 10% or less, and more preferably 1% or less including zero. From this, the technical idea of imparting flame retardancy by crosslinking treatment so as to have a gel fraction of 30% or more as in the above-mentioned Patent Document 2 and the weak crosslinking treatment of the present invention are fundamental. Is different. In addition, the gel fraction here is a value obtained by the following method.
Gel fraction (%): After crosslinking, 1 g of the sealing material is weighed and placed in an 80 mesh wire mesh bag. Next, a sample with the wire mesh is put into a Soxhlet extractor, and xylene is refluxed at the boiling point. After 10 hours of continuous extraction, the sample was taken out together with the wire mesh, weighed after drying, and compared with the mass before and after extraction to measure the mass% of the remaining insoluble matter, which was taken as the gel fraction. In addition, about the gel fraction of the sealing material sheet | seat which is a multilayer film, the said process is performed with the multilayer state in which all the layers were laminated | stacked, and the obtained measured value is the said multilayer sealing material sheet. The gel fraction was used.

  Further, as another aspect, the weak crosslinking treatment of the intermediate layer can be confirmed from the viewpoint of molecular weight. The weight average molecular weight in terms of polystyrene of the encapsulant for solar cell module of the present invention is 120,000 to 300,000, and the ratio of the weight average molecular weight of the encapsulant after weak crosslinking of the intermediate layer / polyethylene resin before crosslinking Is in the range of 1.5 to 3.0. From this, it can be understood that although it is a macromolecule, a dense cross-linked structure is not formed, and a weak cross-link of the intermediate layer is formed. In addition, the weight average molecular weight in this invention melt | dissolves so that it may become 6 wt% of xylene, a viscosity is measured, and the weight average molecular weight is calculated | required from conversion with the polystyrene sample from the viscosity. As for the molecular weight of the encapsulant sheet, which is a multilayer film, the above-mentioned treatment was carried out with all the layers being laminated, and the obtained measurement value was determined based on the gel content of the multilayer encapsulant sheet. Rate.

<(B) The process of apply | coating a 1st crosslinking agent>
Next, a first cross-linking agent having a half-life temperature of 130 ° C. or more and less than 170 ° C. for 1 minute on at least one surface of the above-described base sheet, the first cross-linking agent, respectively 0.25 g / ^{m 2} or more 3.0 g / ^{m 2} or less of coating weight of but less than 130 ° C. or higher 170 ° C., i.e. in both total 0.5 g / ^{m 2} or more 6.0 g / ^{m 2} It apply | coats with the following application quantities, and the sealing material for solar cell modules of this invention is obtained. The gel fraction at this time is the same value as that of the substrate sheet.

  The first cross-linking agent has a 1 minute half-life temperature of 130 ° C. or higher and lower than 170 ° C. If it is in this temperature range, since a crosslinking agent reacts at the temperature at the time of lamination in a modularization process, heat resistance improves.

The coating amount of the first crosslinking agent is 0.25 g / m ² or more and 3.0 g / m ² or less on the surface of each outermost layer. If it is less than 0.25 g / m ² , the heat resistance is insufficient, and if it exceeds 3.0 g / m ² , the flexibility is lowered.

  As content of the 1st crosslinking agent in the sealing material for solar cell modules, 0.1 to 0.3 mass% is preferable. If it is less than 0.1% by mass, the heat resistance is insufficient, and if it exceeds 0.3% by mass, it takes time for coating impregnation, and the productivity is significantly reduced.

  Application of the first crosslinking agent is not particularly limited as long as it is dissolved in a solvent such as toluene and applied by a conventionally known application method. By applying the first cross-linking agent, the first cross-linking agent is impregnated from the surface of the outermost layer into the inside, but does not reach the already weakly cross-linked intermediate layer, and the first cross-linking agent is not reached in the intermediate layer. Is 0.01% or less, and a sealing material having a multilayer structure substantially not contained is obtained. As a result, in the subsequent laminating step, the first cross-linking agent is present only in the outermost layer, and as a result, in the initial stage before cross-linking, it has flexibility and excellent conformability (molding suitability). Then, sufficient heat resistance can be obtained by the subsequent crosslinking reaction of the first cross-linking agent in the outermost layer, and both heat resistance and flexibility can be achieved.

  The sealing material for solar cell module of the present invention thus obtained has an MFR of 1.5 g / 10 min or less at 190 ° C. and a load of 2.16 kg measured according to JIS K7210 of the intermediate layer, and is the outermost layer. MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS K7210 is 0.2 g / 10 min or more and 10 g / 10 min or less. The gel fraction of all layers at this time is 0% or more and less than 1%.

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer structure of a solar cell module using the sealing material of the present invention. In the solar cell module 1 of the present invention, a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 are sequentially laminated from the incident light receiving surface side. ing. The solar cell module 1 of the present invention uses the above-described sealing material for at least one of the front sealing material layer 3 and the back sealing material layer 5.

[Method for manufacturing solar cell module]
The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integral molded body by a molding method such as a vacuum laminating method.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4, and the back surface protective sheet 6 that are members other than the front sealing material layer 3 and the back sealing material layer 5 are made of conventionally known materials. It can be used without particular limitation. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. In addition, the sealing material of this invention is applicable not only to a single crystal type but to all other solar cell modules.

  Here, in the sealing material of the present invention, the crosslinking treatment of only the outermost layer proceeds by the first crosslinking agent that is unevenly distributed in the outermost layer in the modularization step or the separate crosslinking treatment step. The conditions in the laminating process are, for example, a temperature of 130 to 180 ° C. and a time of 10 to 120 minutes. Thereby, for example, when the encapsulant for solar cell module is heated at 130 ° C. for 15 minutes and cured at 150 ° C. for 20 minutes, the intermediate layer is measured at 190 ° C. according to JIS K7210 at a load of 2.16 kg. The MFR is 1.5 g / 10 min or less, and the MFR of the outermost layer is 0.4 g / 10 min or less.

  In the present invention, since the weak cross-linking of the intermediate layer by the second cross-linking agent is completed at the time of film formation, the second cross-linking agent does not change the MFR of the intermediate layer before and after the laminating step. On the other hand, the first cross-linking agent of the outermost layer is coated and impregnated and is unevenly distributed only in the outermost layer before the laminating step. For this reason, the MFR of the outermost layer greatly decreases after the laminating process, and the cross-linking agent is consumed and disappears after the laminating process. Thereby, both flexibility and heat resistance can be achieved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.

[Example 1]
<Raw material of polyethylene resin>
The following raw materials were used.
Base resin (I): Metallocene linear low density polyethylene (M-LLDPE1) pellets having a density of 0.880 g / cm ³ and an MFR at 190 ° C. of 3.5 g / 10 min were used.
Base resin (II): Metallocene linear low density polyethylene (M-LLDPE1) pellets having a density of 0.880 g / cm ³ and an MFR at 190 ° C. of 30 g / 10 min were used.
Silane-modified transparent resin: 2 parts by mass of vinyltrimethoxysilane with respect to 98 parts by mass of M-LLDPE2 having a density of 0.881 g / cm ³ and MFR at 190 ° C. of 2 g / 10 minutes, and a radical generator Was mixed with 0.1 part by mass of dicumyl peroxide, and melted and kneaded at 200 ° C. to obtain a silane-modified transparent resin.
Crosslinking agent masterbatch: 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi Co., Ltd.) as a second crosslinking agent with respect to 100 parts by mass of M-LLDPE1 pellets The master batch was obtained by impregnating 0.5 parts by mass of Ruperox 101, 1 minute half-life temperature of 181 ° C.).
Weatherproof masterbatch: 3.8 parts by mass of benzophenone UV absorber and 5 parts by mass of hindered amine light stabilizer with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ Part and 0.5 parts by mass of a phosphorous heat stabilizer were mixed, melted, processed, and pelletized to obtain a master batch.

<(A) Production of base sheet>
79 parts by mass of the base resin (I), 5 parts by mass of the silane-modified transparent resin, 7 parts by mass of the cross-linking agent masterbatch, and 9 parts by mass of the weatherproof masterbatch are used as an intermediate layer composition, and 86 parts by mass of the base resin (I) and silane 5 parts by mass of a modified transparent resin, 4 parts by weight of a crosslinking agent masterbatch, and 9 parts by mass of a weatherproof masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of this sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 0.4 g / 10 min for the outermost layer and 0.3 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was zero.

<(B) Application of first cross-linking agent>
Next, t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi Co., Ltd., trade name Luperox TBEC, 1 minute half-life temperature is 166 on both surfaces of the base sheet as a first cross-linking agent. ° C) was dissolved in toluene, and the coating amount of the first cross-linking agent was 2.0 g / m ² (4.0 g / m ^{2 on} both sides, 0.11% by mass in all layers of the sealing material) on both surfaces. ) And dried by applying a bar coater to obtain a solar cell module sealing material of Example 1.

<Evaluation of post-crosslinking encapsulant>
Thereafter, the above-mentioned sealing material is heated at 130 ° C. for 15 minutes and cured at 150 ° C. for 20 minutes, and the post-crosslinking sealing material has an MFR of 0.0 g / 10 min (not measurable) in the outermost layer, and an intermediate layer And 0.1 g / 10 min. The gel fraction of the post-crosslinking encapsulant was 4%.

[Example 2]
79 parts by mass of the base resin (I), 5 parts by mass of the silane-modified transparent resin, 4 parts by mass of the cross-linking agent masterbatch, and 9 parts by mass of the weathering masterbatch are used as an intermediate layer composition, and 86 parts by mass of the base resin (I) 5 parts by mass of the modified transparent resin, 9 parts by mass of the crosslinking agent masterbatch, and 9 parts by mass of the weathering masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of the sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 0.2 g / 10 min for the outermost layer and 0.5 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was zero.

Except that the coating amount of the first cross-linking agent was 2.0 g / m ² (4.0 g / m ^{2 on} both sides, 0.11% by mass in all layers of the sealing material), it was the same as in Example 1. The sealing material for solar cell modules and the post-crosslinking sealing material of Example 2 were obtained. The gel fraction of the post-crosslinking encapsulant was 3%.

[Example 3]
79 parts by mass of the base resin (I), 5 parts by mass of the silane-modified transparent resin, 4 parts by mass of the cross-linking agent masterbatch, and 9 parts by mass of the weathering masterbatch are used as an intermediate layer composition, and 86 parts by mass of the base resin (II) and silane 5 parts by weight of the modified transparent resin, 5 parts by weight of the cross-linking agent masterbatch, and 9 parts by weight of the weathering masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of this sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 10.0 g / 10 min for the outermost layer and 0.5 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was zero.

Example similar to Example 1 except that the coating amount of the first cross-linking agent was 7.5 g / m ² (15 g / m ^{2 on} both sides, 0.3% by mass in all layers of the sealing material). 3 solar cell module sealing material and post-crosslinking sealing material were obtained. The gel fraction of the post-crosslinking encapsulant was 5%.

[Example 4]
79 parts by mass of base resin (I), 5 parts by mass of a silane-modified transparent resin, 2 parts by mass of a crosslinking agent masterbatch, and 9 parts by mass of a weatherproof masterbatch are used as an intermediate layer composition, and 86 parts by mass of base resin (I) and silane 5 parts by mass of the modified transparent resin, 9 parts by mass of the crosslinking agent masterbatch, and 9 parts by mass of the weathering masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of this sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 0.2 g / 10 min for the outermost layer and 1.5 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was zero.

Except that the coating amount of the first cross-linking agent was 2.0 g / m ² (4.0 g / m ^{2 on} both sides, 0.11% by mass in all layers of the sealing material), it was the same as in Example 1. A solar cell module sealing material and a post-crosslinking sealing material of Example 4 were obtained. The gel fraction of the post-crosslinking encapsulant was 2%.

[Example 5]
79 parts by mass of the base resin (I), 5 parts by mass of the silane-modified transparent resin, 2 parts by mass of the cross-linking agent masterbatch, and 9 parts by mass of the weather-resistant masterbatch are used as an intermediate layer composition, and 86 parts by mass of the base resin (II) 5 parts by weight of the modified transparent resin, 5 parts by weight of the cross-linking agent masterbatch, and 9 parts by weight of the weathering masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of this sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 10.0 g / 10 min for the outermost layer and 1.5 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was zero.

Example similar to Example 1 except that the coating amount of the first cross-linking agent was 7.5 g / m ² (15 g / m ^{2 on} both sides, 0.3% by mass in all layers of the sealing material). 5 solar cell module sealing material and post-crosslinking sealing material were obtained. The gel fraction of the post-crosslinking encapsulant was 4%.

[Example 6]
A sealing material was formed in the same manner as in Example 1, and the coating amount of the first crosslinking agent was 7.5 g / m ² (15 g / m ^{2 on} both sides, 0.3% by mass in all layers of the sealing material). The solar cell module encapsulant and the post-crosslinking encapsulant of Comparative Example 4 were obtained in the same manner as in Example 1 except that. The gel fraction of the post-crosslinking encapsulant was 17%.

[Comparative Example 1]
79 parts by mass of the base resin (I), 5 parts by mass of the silane-modified transparent resin, 7 parts by mass of the cross-linking agent masterbatch, and 9 parts by mass of the weatherproof masterbatch are used as an intermediate layer composition, and 86 parts by mass of the base resin (I) and silane 5 parts by mass of the modified transparent resin, 10 parts by weight of the cross-linking agent masterbatch, and 9 parts by mass of the weathering masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of the sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 0.1 g / 10 min for the outermost layer and 0.3 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was 6%. Since the MFR of the resin to be molded is low, the load on the molding machine is very high and continuous production is difficult.

Except that the coating amount of the first cross-linking agent was 2.0 g / m ² (4.0 g / m ^{2 on} both sides, 0.11% by mass in all layers of the sealing material), it was the same as in Example 1. The solar cell module sealing material and the post-crosslinking sealing material of Comparative Example 1 were obtained. The gel fraction of the post-crosslinking encapsulant was 11%.

[Comparative Example 2]
79 parts by mass of base resin (I), 5 parts by mass of a silane-modified transparent resin, 7 parts by mass of a crosslinking agent masterbatch, and 9 parts by mass of a weatherproof masterbatch are used as an intermediate layer composition, and 86 parts by mass of base resin (II), silane 5 parts by mass of a modified transparent resin, 3 parts by weight of a crosslinking agent masterbatch, and 9 parts by mass of a weatherproof masterbatch are used as the outermost layer composition, and the outermost layer: intermediate layer: outermost layer = 1: 5: 1 A substrate sheet having a thickness of 600 μm was manufactured by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a layer φ30 mm extruder and a film molding machine having a T die having a width of 200 mm. The density of the sealing material sheet was 0.880 g / cm ³ , and the MFR at 190 ° C. was 20.0 g / 10 min for the outermost layer and 0.3 g / 10 min for the intermediate layer. The gel fraction of this solar cell module sealing material was zero. Since the MFR of the resin to be molded is high, defects such as sticking to the cooling roll occur and continuous production is difficult.

Comparative Example as in Example 1 except that the coating amount of the first cross-linking agent was 7.5 g / m ² (15 g / m ^{2 on} both sides, 0.3% by mass in all layers of the sealing material). 2 solar cell module sealing material and post-crosslinking sealing material were obtained. The gel fraction of the post-crosslinking encapsulant was 4%.

[Comparative Example 3]
A sealing material was formed in the same manner as in Example 1, and a sealing material without Comparative Example 3 was used as a sealing material of Comparative Example 3.

[Comparative Example 4]
A sealing material was formed in the same manner as in Example 1, and the coating amount of the first cross-linking agent was 10 g / m ² (20 g / m ^{2 on} both sides, 0.4% by mass in all layers of the sealing material). did. It was difficult to impregnate the sealing material with the entire amount of the applied crosslinking agent, and a desired sealing material could not be obtained.

  Table 1 summarizes the MFR of the outermost layer and the intermediate layer and the evaluation results for the solar cell module sealing material and the post-crosslinking sealing material of Examples and Comparative Examples.

  The film-forming property allows the resin extruded from the T-die to be affixed to the cooling roll as a single unit, without dripping due to poor sticking to the cooling roll or peeling off due to excessive sticking to the cooling roll, so that it can be wound up well Was evaluated as ◯, the sign of the above-mentioned problem was seen but rewoundable was Δ, and the unrollable was evaluated as x.

  Cell cracking was performed by laminating a solar battery laminate in which glass, a sealing material, a solar battery cell, a sealing material, and a back sheet were laminated in this order at 130 ° C. for 15 minutes and at a pressure of 100 kPa, and further cured at 150 ° C. for 20 minutes. Measure the solar cell sample with an EL emission tester, ○ if there is no crack on the entire cell surface, △ if there is a crack but overall light emission can be confirmed, × if there is a crack and where you can not confirm the light emission × As evaluated.

  In the thermal cycle, a sample prepared in the same configuration as the above-described cell crack evaluation is put into an oven whose temperature changes in the following predetermined cycle, and the sample is put into the oven. The deviation and cracking of the lines were evaluated. The cell or lead wire misalignment is less than 0.5 mm and there is no change in EL emission, the cell or lead wire misalignment is 0.5 mm or more and less than 1 mm and the EL emission does not change Δ, A cell or lead wire misalignment of 1 mm or more or a portion where no light emission occurred in EL light emission was evaluated as x. The cycle condition of the oven is to reciprocate between −20 ° C. and 90 ° C., the time required to change the temperature in the previous period is 5 hours, the time for maintaining the temperature is 1 hour, and starts from −20 ° C. to 90 ° C. The process of returning to −20 ° C. via one cycle was defined as one cycle.

  From the results of Table 1, the solar cell module encapsulant of the present invention has heat resistance and excellent cell crack prevention and unevenness followability in the lamination process when modularized, as compared with the comparative example. Can understand.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back sealing material layer 6 Back surface protection sheet

Claims (1)

A method for producing a multilayer solar cell module encapsulant comprising at least an intermediate layer and an outermost layer disposed on both sides of the intermediate layer ,
90% by mass or more of polyethylene resin having a density of 0.900 g / cm ³ or less, and a 1-minute half-life temperature of 160 to 200 ° C. contained in the composition by 0.02 to 0.5% by mass An intermediate layer resin composition containing a second cross-linking agent and having a 1 minute half-life temperature of 130 ° C. or higher and lower than 170 ° C. , and a polyethylene-based resin having a density of 0.900 g / cm ³ or lower. the outermost layer resin composition containing substantially no cross-linking agent comprises at least 90 wt% of the resin, and melt-molding by the second one-minute half-life temperature or more crosslinking agents, in the intermediate layer the lightly crosslinked through the rows Ukoto, 190 ° C., as measured in accordance with JIS K7210 of the intermediate layer, MFR at load of 2.16kg is not more than 0.1 g / 10min or more 1.5 g / 10min, full-thickness Gel fraction is 0% or more Less than 1%, obtaining a multilayer substrate sheet,
On both surfaces of the base sheet obtained in the step of obtaining said substrate sheet, said first crosslinking agent 0.25 g / ^{m 2} or more 3.0 g / ^{m 2} or less of coating weight, 0 in both total. a step of applying at 5 g / ^{m 2} or more 6.0 g / ^{m 2} or less of the coating amount, consisting method for producing an encapsulating material for a solar cell module.

Images