JP6248669B2 - Sealant sheet for solar cell module - Google Patents

Description

  The present invention relates to a sealing material sheet for a solar cell module.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, various types of solar cell modules have been developed. In general, a solar cell module has a configuration in which a transparent front substrate, a solar cell element, and a back surface protection sheet are laminated via a sealing material sheet.

  As a sealing material sheet filled in the solar cell module and used to protect the solar cell element from external impacts and prevent moisture from entering the solar cell module, ethylene-vinyl acetate copolymer Combined resins (EVA) have been used as the most common. However, EVA resin has a tendency to gradually decompose with long-term use, and deteriorates inside the solar cell module to decrease its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. As a solution to this problem, a sealing material sheet for a solar cell module using a polyethylene resin instead of EVA resin has been proposed (see Patent Document 1).

  As a polyethylene-based sealing material sheet, for example, a sealing material made of a modified ethylene-based resin containing alkoxysilane as a copolymerization component is also known. Moreover, the sealing material sheet | seat which mix | blended a crosslinking agent with such modified ethylene resin, and was bridge | crosslinked by the modularization process or the subsequent heating process is known (refer patent document 2). Such a polyethylene-based sealing material sheet can be preferably used as a sealing material sheet for a solar cell module as having a weather resistance and durability equivalent to or higher than those of an EVA resin sealing material.

  On the other hand, the sealing material sheet for a solar cell module is also required to have high adhesion with other members stacked vertically in the solar cell module. In particular, as an urgent issue, in a module equipped with a back contact type solar cell element that has been increasing in demand in recent years, the sealing material sheet between the sealing material sheet and the metal wiring portion of the current collecting sheet There is a strong demand for improved metal adhesion. The current collector sheet has a structure in which many portions on the resin base material are covered with a metal foil such as a copper foil. In the solar cell module, the metal sheet of the encapsulant sheet is adhered to the structure. Improvement is an essential issue.

  As a means for improving the metal adhesion of the encapsulant sheet, first, a means for improving the wettability by increasing the fluidity of the material resin can be considered. However, fluidity and heat resistance are in a trade-off relationship, and it is extremely difficult to obtain a sealing material sheet having sufficiently high metal adhesion only by adjusting fluidity while maintaining necessary heat resistance. .

  As another means for improving the metal adhesion of the encapsulant sheet, there has also been proposed an encapsulant sheet in which a specific adhesion component is added as a metal adhesion component to improve adhesion by chemical bonding (patent) Reference 3).

Japanese Patent Laid-Open No. 2002-235048 International Publication 2011/152314 JP 2012-195661 A

  As described above, in polyethylene-based encapsulant sheets, heat resistance and metal adhesion required as sheets for solar cell module applications are generally in a trade-off relationship, and both physical properties are compatible at a high level. It was extremely difficult to do.

  According to the sealing material sheet of Patent Document 3, it is possible to improve the metal adhesion, but the composition is extruded when the binding reaction of the metal adhesion component proceeds also during the extrusion molding of the sealing material composition. There was a problem that productivity may be reduced due to close contact with the screw.

  While maintaining the high heat resistance desired for a solar cell module sealing material sheet, at the same time, it has excellent metal adhesion, and also has good productivity, and the solar cell module sealing material sheet Was demanded.

  The present invention has been made in view of the above situation, and an object thereof is a polyethylene-based sealing material sheet excellent in a water vapor barrier, and has a high level of heat resistance and metal adhesion. It is an object to provide a sealing material sheet for use under good productivity.

  As a result of intensive studies, the inventors of the present invention have made a sealing material sheet for a solar cell module into a multilayer structure composed of an intermediate layer and an outermost layer serving as an adhesion surface with a metal portion, and the thickness of each layer. It has been found that the above problems can be solved by optimizing the combination of the torque value of each layer within a unique range, and the present invention has been completed. More specifically, the present invention provides the following.

(1) Density 0.870 g / cm ³ or more 0.940 g / cm ³ or less and the intermediate layer to the polyethylene resin as a base resin of a density 0.870 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin And a multilayer sealing material sheet having a total thickness of 300 μm or more and 1000 μm or less, wherein the intermediate layer has a thickness with respect to the total thickness. The ratio is 0.6 or more and 0.94 or less, the torque value under the following measurement conditions is 0.11 N · m or more, and the outermost layer is the total thickness of the thickness of each individual outermost layer The sealing material sheet for solar cell modules whose thickness ratio with respect to thickness is the range of 0.03 or more and 0.2 or less, and the said torque value is less than 0.11 N * m.
[Torque value measurement conditions]
The torque value is measured in accordance with JIS K6300-2 using a curast meter at a temperature of 150 ° C. and a torsional frequency of 100 ± 6 times / minute.

  (2) The encapsulant sheet according to (1), wherein the intermediate layer has a thickness of 180 μm or more and the outermost layer has a thickness of 140 μm or less.

  (3) The encapsulant sheet according to (1) or (2), wherein the polyethylene resin is a metallocene linear low-density polyethylene.

  (4) The encapsulant sheet according to any one of (1) to (3), wherein the polyethylene resin contains a copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer. .

(5) (1) to (4) be any sealing material sheet manufacturing method according to the, the base resin density 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin an intermediate layer formed by the intermediate layer composition is melt-molded to the outermost layer composition and a density 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin base resin by melting A sheet forming step of forming an uncrosslinked multilayer sheet by laminating the outermost layer, and a crosslinking step of performing a crosslinking treatment by irradiation of ionizing radiation on the uncrosslinked multilayer sheet, The content of the crosslinking agent in the product is 0% by mass or more and less than 0.5% by mass, and the content of the crosslinking agent in the outermost layer composition is 0% by mass or more and less than 0.02% by mass. A manufacturing method of a certain sealing material sheet.

  (6) The manufacturing method of the sealing material sheet as described in (5) whose content of the crosslinking agent in the said composition for intermediate | middle layers is 0.02 mass% or more and less than 0.5 mass%.

(7) (1) to (4) be any sealing material sheet manufacturing method according to the, the base resin density 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin an intermediate layer formed by the intermediate layer composition is melt-molded to the outermost layer composition and a density 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin base resin by melting The outermost layer is laminated to form a preliminary multilayer sheet, and the content of the crosslinking agent in the intermediate layer composition is 0.02% by mass or more and less than 0.5% by mass. And the manufacturing method of the sealing material sheet whose content of the crosslinking agent in the said composition for outermost layers is 0 to less than 0.02 mass%.

  (8) A solar cell module comprising the encapsulant sheet according to any one of (1) to (4) and a solar cell element, wherein the outermost layer of the encapsulant sheet is the solar cell module. The solar cell module arrange | positioned so that the metal part of the other member which comprises may be faced.

  (9) The solar cell element is a back contact type solar cell element, and further includes a current collecting sheet in which a metal wiring portion is formed on a surface of a resin base material, and the outermost layer of the encapsulant sheet is the collector layer. The solar cell module according to (8), which is disposed so as to face a metal wiring portion of the electric sheet.

  According to the present invention, a polyethylene-based encapsulant sheet having excellent water vapor barrier properties and the like, and a solar cell module encapsulant sheet having both high heat resistance and metal adhesion at a high level, has good productivity. Can be offered under.

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the sealing material sheet of this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module which laminated | stacked the sealing material sheet of this invention, and the back contact type solar cell element.

  Hereinafter, first, the encapsulant composition for producing the encapsulant sheet for the solar cell module of the present invention will be described, and thereafter, the encapsulant sheet for the solar cell module of the present invention and the present invention. The detail is demonstrated in order of a solar cell module.

<Encapsulant composition>
As the sealing material composition of the present invention, a resin composition based on a polyethylene resin is used. In the production of the encapsulant sheet of the present invention, it is preferable to use an optimum composition for each layer in order to form the intermediate layer of the multi-layer encapsulant sheet or the outermost layers. Specifically, the range in which the torque value of each layer of the encapsulant sheet after forming the encapsulant composition for each layer can be adjusted to a different optimum torque value range unique to the present invention for each layer. Therefore, a sealing material composition for each layer may be selected as appropriate. Specifically, the optimum torque value unique to the present invention is, as described above, for the torque value of each layer of the sealing material sheet, the torque value of the intermediate layer is 0.11 N · m or more, and the torque value of the outermost layer is , Less than 0.11 N · m.

  As a means for optimizing the torque value of the encapsulant sheet within the above range, adjustment means at the composition stage from selection of the encapsulant composition to melt extrusion, and crosslinking after sheet molding And adjustment means at the processing stage. As a preferred specific example of the former, a method described in Patent Document 2, that is, a method of adjusting a torque value to a desired range by weak crosslinking treatment by adding an appropriate amount of a crosslinking agent to a sealing material composition. Can be mentioned. Further, as a preferred specific example of the latter, there is a method described in JP2013-115212A, that is, a method of adjusting a torque value to a desired range by crosslinking treatment with ionizing radiation after molding a sealing material sheet. be able to. Details of these torque value adjustment methods will be described later.

[Composition for intermediate layer]
The intermediate layer composition is a sealing material composition used for forming an intermediate layer of the sealing material sheet of the present invention, which is a multilayer sealing material sheet. In the present specification, the multilayer encapsulant sheet is an outermost layer that is a layer formed on the outermost surface side of at least one of the encapsulant sheets, and an intermediate layer that is a layer other than the outermost layer. It means a sealing material sheet having a multi-layer structure of two or more layers. The intermediate layer refers to a layer other than the outermost layer, and may have a single layer structure, or the intermediate layer itself may have a multilayer structure including a plurality of layers.

  As the polyethylene resin used as the base resin of the intermediate layer composition, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene linear low density polyethylene (M-LLDPE) is preferably used. it can. Among these, LLDPE, which is a copolymer of ethylene and α-olefin, can provide the encapsulant sheet with good flexibility while maintaining sheet processability.

The density of the polyethylene resin used as the base resin of the intermediate layer composition is 0.870 or more and 0.940 g / cm ³ or less, preferably 0.870 or more and 0.930 g / cm ³ or less. The density of the base resin of the intermediate layer composition is preferably the same as that of the outermost layer composition or higher than that of the outermost layer composition.

  The polyethylene resin used as the base resin of the intermediate layer composition is an MFR value measured at 190 ° C. and a load of 2.16 kg (according to “ “MFR” refers to this value.) Is preferably in the range of 0.5 g / 10 min to 30.0 g / 10 min, and preferably 1.0 g / 10 min to 15.0 g / 10 min. Is more preferable.

  The torque value of each layer of the encapsulant sheet can be optimized by adjusting the combination of the MFR and the degree of progress of the crosslinking reaction, for example. Specifically, the crosslinking reaction may be a reaction with a crosslinking agent or a crosslinking reaction with ultraviolet rays or ionizing radiation. In addition, by using a resin having a lower MFR than the base resin of the outermost layer composition within the MFR range preferable for film formation as the base resin of the intermediate layer composition, for example, each layer has the same strength. When the crosslinking treatment by ionizing radiation is performed, the torque value of each layer can be adjusted to the respective optimum ranges described above. Alternatively, it is possible to optimize the torque value for each layer by providing a gradient in the amount of the crosslinking agent or crosslinking aid added to each layer.

  Thus, the torque value of the encapsulant sheet is not uniquely determined by any one of the physical properties of the encapsulant composition and the treatment conditions during the crosslinking treatment, and the production equipment for carrying out the production, etc. It is possible to adjust the above-mentioned various physical properties and various conditions in any combination according to the realistic conditions. Therefore, if the final torque value is adjusted to the above range specified in the present application by adjusting such arbitrary physical properties and conditions, MFR of the sealing material composition at the composition stage, or other additions Various physical properties such as the content of the agent, crosslinking conditions and the like are not necessarily within the above ranges, but are within the scope of the present invention. In addition, the torque value of the intermediate layer of the encapsulant sheet can be set to 0.11 N · m or more by such various adjusting means, thereby providing sufficient heat resistance to the encapsulant sheet. Can be granted.

  The content of the base resin contained in the intermediate layer composition is preferably 10 parts by mass or more and 99 parts by mass or less, more preferably 50 parts by mass or more, with respect to 100 parts by mass in total of all resin components in the composition. It is 99 mass parts or less, More preferably, it is 90 mass parts or more and 99 mass parts or less. Other resins may be contained within the above composition range. In the present specification, the term “all resin components” includes the other resins described above.

[Outermost layer composition]
The outermost layer composition is a sealing material composition used for forming the outermost layer of the sealing material sheet of the present invention, which is a multilayer sealing material sheet. The definition of the outermost layer in the present specification is as described above.

  The polyethylene resin used as the base resin of the outermost layer composition is the same as the base resin of the intermediate layer composition, such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or metallocene linear low density. Polyethylene (M-LLDPE) can be preferably used as appropriate. Among these, M-LLDPE, which is synthesized using a metallocene catalyst that is a single-site catalyst, has few side chain branches and a uniform comonomer distribution, and therefore has a narrow molecular weight distribution, as detailed below. It is easy to make this ultra-low density, and preferable flexibility can be imparted to the outermost layer of the encapsulant sheet. As a result, adhesion between the solar cell module and the other member laminated with the sealing material sheet can be enhanced.

The density of the polyethylene resin used as the base resin of the composition for the outermost layer is 0.870 or more and 0.940 g / cm ³ or less, preferably 0.870 or more and 0.930 g / cm ³ or less. The density of the base resin of the outermost layer composition is preferably the same as that of the intermediate layer composition or lower than that of the intermediate layer composition.

  In addition, the polyethylene resin used as the base resin of the outermost layer composition is 190 ° C. and a load of 2 measured according to JIS7210 from the viewpoint of maintaining good film forming properties, like the base resin of the intermediate layer composition. The MFR value at .16 kg is preferably in the range of 0.5 g / 10 min to 30.0 g / 10 min, and more preferably 1.0 g / 10 min to 15.0 g / 10 min.

  Selection of the composition and processing conditions for setting the torque value for the outermost layer of the encapsulant sheet to less than 0.11 N · m is the same as in the case of the intermediate layer, and the combination of MFR and the degree of progress of the crosslinking reaction It is possible to optimize by adjusting. As such, the torque value of the outermost layer of the encapsulant sheet can be less than 0.11 N · m, and thus the fluidity during lamination and the solar cell element required as a sheet It is possible to impart sufficient molding characteristics to the sealing material while maintaining the protective performance.

  Content of the said base resin contained in the composition for outermost layers is the same amount ratio as the case of the above-mentioned composition for intermediate | middle layers. And in the said composition range, other resin may be included similarly.

(Silane-modified polyethylene resin)
In each of the sealing material compositions for the intermediate layer and the outermost layer, a silane-modified polyethylene resin can be appropriately contained. However, in order to efficiently improve the adhesion between the encapsulant sheet and the other member, it is particularly preferable to add the same resin to the outermost layer that becomes the adhesion surface with the other member. The silane-modified polyethylene resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain to linear low-density polyethylene (LLDPE) or the like as a main chain. Such a graft copolymer has a high degree of freedom of silanol groups that contribute to adhesion. Thereby, the adhesiveness to the other member of a sealing material sheet can be improved.

  The silane-modified polyethylene resin can be produced, for example, by the method described in JP-A-2003-46105. By using the resin as a component of the sealing material composition of the solar cell module, strength and durability can be obtained. In addition, it has excellent weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics, and is also affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. Therefore, it is possible to manufacture solar cell modules having extremely excellent heat-fusibility, stably and at low cost, and suitable for various applications.

  Examples of ethylenically unsaturated silane compounds to be graft polymerized with LLDPE etc. include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltri One or more selected from phenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be used. .

  The graft amount, which is the content of the ethylenically unsaturated silane compound, is, for example, 0.001 to 15 parts by mass, preferably 0.01 to 100 parts by mass with respect to a total of 100 parts by mass of all resin components in the sealing material composition. What is necessary is just to adjust suitably so that it may become 5 mass parts, Especially preferably, it is 0.05-2 mass parts. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and heat-fusibility tend to be inferior.

(Crosslinking agent)
Each of the encapsulant compositions for the intermediate layer and the outermost layer can contain a crosslinking agent as appropriate. A well-known thing can be used for a crosslinking agent, It does not specifically limit, For example, a well-known radical polymerization initiator can be used. Examples of radical polymerization initiators include hydroperoxides such as diisopropylbenzene hydroperoxide and 2,5-dimethyl-2,5-di (hydroperoxy) hexane; di-t-butyl peroxide, t-butyl Cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3, etc. Dialkyl 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 pero Ci-2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2 , 5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate Oxyesters; organic peroxides such as methyl peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide, or azo compounds such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile), dibutyltin Diacetate, dibutyltin dilaurate It can be mentioned dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst.

  When the crosslinking agent is contained in the encapsulant composition, the content thereof may be appropriately adjusted according to the method for producing the encapsulant sheet. Note that the optimum range of the content of the crosslinking agent varies depending on the selection of the means for optimizing the torque value in the production of the sealing material sheet.

  For example, when manufacturing a sealing material sheet by the method described in JP2013-115212A, that is, a method of adjusting a torque value to a desired range by crosslinking treatment with ionizing radiation after molding of the sealing material sheet. The addition of a crosslinking agent is not essential, and the content in the encapsulant composition is preferably 0% by mass or more and less than 0.5% by mass with respect to the total resin components of the encapsulant composition. Is a range of 0.02 mass% or more and 0.5 mass% or less. By adding 0.02% by mass or more of a crosslinking agent, a preferable heat resistance can be imparted to the polyethylene resin used in the sealing material sheet of the present invention, and at the same time, the torque value can be adjusted to a desired range.

  On the other hand, for example, as described in Patent Document 2, sealing is performed during the molding by a manufacturing method that imparts heat resistance by advancing a very weak crosslinking reaction (weak crosslinking) that does not exert an excessive burden on the extrusion apparatus. When manufacturing a material sheet, the sealing material sheet of the present invention is added by adding 0.02 mass% or more and less than 0.5 mass% of a crosslinking agent to the total resin component of the sealing material composition. A preferable heat resistance can be imparted to the polyethylene resin used in the above process, and at the same time, the torque value can be adjusted to a desired range. On the other hand, when the addition amount of the crosslinking agent exceeds 0.5% by mass, a gel is generated during molding and the film forming property is lowered, and the transparency is also lowered.

(Crosslinking aid)
In the present invention, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group can be used as a crosslinking aid. More preferably, the cross-linking aid is one in which the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. By adding such a crosslinking aid, the crystallinity of the low density polyethylene can be reduced, and a crosslinked encapsulant sheet excellent in low temperature flexibility can be obtained.

  However, in the case of adjusting the torque by the weak crosslinking reaction, it is preferable not to use a crosslinking aid. In addition, this is not the case when a trace amount that does not show a crosslinking effect is contained. Specifically, the trace amount that does not show the crosslinking effect is less than 0.01% by mass in the composition.

  When the crosslinking aid is used, specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), triaryl Methylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol Poly (meth) acryloxy compounds such as diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycidyl ether and epoxy group Containing two or more 1,6-hexanediol diglycidyl ether, and 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, an epoxy-based compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among these, tricyclodecane dimethanol diacrylate, which has a particularly high effect of improving adhesion to the glass surface, has good compatibility with low density polyethylene, and can be expected to improve heat resistance, can be particularly preferably used. The content of the crosslinking aid is preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0.05 parts by mass with respect to 100 parts by mass in total of all resin components of the sealing material composition. It is the range below 2.0 parts by mass.

(Adhesion improver)
In each of the encapsulant compositions for the intermediate layer and the outermost layer, the adhesion durability with other base materials can be further enhanced by appropriately adding an adhesion improver. As the adhesion improver, a known silane coupling agent can be used. The silane coupling agent is not particularly limited. For example, vinyl-based silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyldiethoxy. A methacryloxy-based silane coupling agent such as silane or 3-methacryloxypropyltriethoxysilane can be preferably used. In addition, these can also be used individually or in mixture of 2 or more types.

  When adding a silane coupling agent as an adhesion improver, the content is 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass in total of all resin components of the sealing material composition. Yes, and the upper limit is preferably 5.0 parts by mass or less. When the content of the silane coupling agent is in the above range, and the polyolefin resin constituting the encapsulant composition contains an appropriate amount of the ethylenically unsaturated silane compound, the adhesion is more preferable. And improve.

  However, even within the above range, the addition of the adhesion improver may adversely affect the physical properties of the encapsulant sheet. Specifically, this is a case where a so-called bleed out occurs in which the silane coupling agent is agglomerated and solidified with time to be pulverized on the surface of the sealing material sheet. Also, depending on the film forming conditions, the reaction resulting from the addition of the silane coupling agent may proceed excessively during film formation, and the sealing material composition may adhere closely to the unloading screw of the extruder, reducing productivity. There is also a case.

  The sealing material sheet of the present invention does not necessarily require the addition of an adhesion improver, and ensures the necessary adhesion by optimizing the combination of thickness and torque value for each layer. Therefore, it is not necessary to add an excessive adhesion improver until the above risk of productivity reduction or the like is taken. Even when the adhesion improver is not added or added in a smaller amount than usual, sufficient adhesion to other members, particularly excellent metal adhesion, can be exhibited.

(Radical absorbent)
In each encapsulant composition for the intermediate layer and the outermost layer, the degree of cross-linking is further refined by using the above-mentioned cross-linking auxiliary agent that serves as a radical polymerization initiator and the radical absorbent that quenches it. Can be adjusted. Examples of such radical absorbents include hindered phenol-based antioxidants, hindered amine-based weather resistance stabilization, and the like. A hindered phenol-based radical absorbent having a high radical absorbing ability near the crosslinking temperature is preferred. The amount of the radical absorbent used is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2.0% by mass with respect to the total resin components of the encapsulant composition. The range is as follows.

(Other ingredients)
Each sealing material composition for intermediate layer and outermost layer may further contain other components. For example, a weather-resistant masterbatch for imparting weather resistance to a sealing material sheet produced using the combination set of the sealing material composition of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, and heat stability Ingredients such as agents are exemplified. These contents vary depending on the particle shape, density, and the like, but may be in the range of 0.001% by mass to 5% by mass with respect to the total resin components of the respective sealing material compositions. preferable. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant sheet.

  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. Thus, good weather resistance can be imparted to the encapsulant sheet. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. As resin used for a weatherproof masterbatch, the polyethylene-type resin used as a base resin for this invention may be sufficient, and said other resin may be sufficient.

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

<Sealing material sheet>
The sealing material sheet of the present invention is a multilayer sealing material constituted by a plurality of layers including an intermediate layer and either one of the intermediate layers, preferably the outermost layer disposed on the outermost surface of both. . And the sealing material sheet of the present invention pays attention to the total thickness of the sealing material sheet, the thickness ratio of the intermediate layer and the thickness of each single outermost layer to the total thickness, and the torque value of each layer. And can only be obtained by optimizing their combinations. In the present specification, the “thickness of each single outermost layer” means the thickness of one single layer out of the total of the two outermost layers arranged on both outermost surfaces. When the outer layer is formed only on one side of the intermediate layer, it means the thickness of the single outermost layer formed on the one side. Hereinafter, as a preferred embodiment of the present invention, referring to FIG. 1, a sealing material sheet 1 having a three-layer structure including two single-layer outermost layers in total above and below a single-layered intermediate layer. Will be described. However, the present invention is not limited to this embodiment.

[Torque value measurement conditions]
Here, the torque value in this specification refers to a value measured in accordance with JIS K6300-2 using a curast meter at a temperature of 150 ° C. and a torsional frequency of 100 ± 6 times / minute. . In the sealing material sheet of the present invention, this torque value is optimized in different ranges in the intermediate layer and the outermost layer.

  The sealing material sheet 1 has an intermediate layer 11, and the outermost layer 12 is disposed on both surfaces of the intermediate layer 11. However, for example, a sealing material having a two-layer structure in which the outermost layer is disposed only on one side of the intermediate layer, or a sealing in which the intermediate layer has a multilayer structure and other functional layers are disposed in the intermediate layer Even a material sheet is within the scope of the present invention as long as it is an encapsulant sheet having an intermediate layer and an outermost layer having the structural requirements of the present invention and having other structural requirements of the present invention.

  The intermediate layer 11 is a layer constituting a main part as a substrate layer in the encapsulant sheet 1. The intermediate layer 11 can impart sufficient heat resistance to the encapsulant sheet 1 by forming the torque value to be 0.11 N · m or more by adjusting the degree of crosslinking or the like. . Thereby, durability of the solar cell module using the sealing material sheet 1 can be improved.

  The outermost layer 12 is a layer that is disposed on the outermost surface of the sealing material sheet in the sealing material sheet 1 and constitutes a subordinate portion as a surface material. The outermost layer 12 can give sufficient flexibility to the encapsulant sheet 1 by forming the torque value to be less than 0.11 N · m by adjusting the degree of crosslinking or the like. . Thereby, the molding characteristic and base material adhesiveness at the time of the integration process as a solar cell module, especially metal adhesiveness can be improved significantly.

  As described above, the torque values of the intermediate layer 11 and the outermost layer 12 of the encapsulant sheet 1 are adjusted by adjusting the content and type of the crosslinking agent and the crosslinking aid in the encapsulant composition and the film forming conditions. Alternatively, it can be arbitrarily adjusted to a desired value by adjusting the crosslinking conditions in the subsequent steps.

  The total thickness of the sealing material sheet 1 including the intermediate layer 11 and both outermost layers 12 is preferably 300 μm or more and 1000 μm or less, and more preferably 350 μm or more and 800 μm or less. When the thickness is less than 300 μm, it is difficult to sufficiently reduce the impact on the solar cell element. On the other hand, even if the thickness exceeds 1000 μm, the effect of reducing the impact cannot be obtained. In addition, the encapsulant sheet of the present invention has a thickness reduced to about 400 μm because the outer layer has flexibility and the inner layer has heat resistance to suppress flow out and film thickness change during the lamination process. Even in this case, it is possible to provide sufficiently preferable molding properties, heat resistance, and solar cell element protection performance.

  The intermediate layer 11 may have a thickness ratio with respect to the total thickness of 0.6 to 0.94, and preferably the thickness ratio is 0.6 to 0.86. Further, the absolute value of the intermediate layer 11 may be 180 μm or more, and preferably 240 μm or more.

  The outermost layer 12 may have a thickness ratio of the thickness of each single outermost layer to the total thickness of 0.03 or more and 0.2 or less, and preferably the same thickness ratio is 0.07 or more and 0. .2 or less. Further, the thickness of the outermost layer 12 may be 140 μm or less, and preferably 100 μm or less, as the absolute value of each individual outermost layer.

  By setting the thickness ratio of the intermediate layer 11 having a relatively large torque value and the outermost layer 12 having a relatively small torque value within the above range, both the heat resistance and the metal adhesion of the encapsulant sheet 1 are good. Can be kept in range. Moreover, the heat resistance of the sealing material sheet | seat 1 can be fully hold | maintained in the preferable range by making each thickness of the intermediate | middle layer 11 and the outermost layer 12 into the said range.

  The encapsulant sheet 1 is a multilayer sheet in which resin sheets having different torque values are laminated at a specific thickness ratio. Moreover, since the base resin of the sealing material composition used is a low-density polyethylene-based resin, it is naturally excellent in transparency and water vapor barrier properties. Furthermore, the encapsulant sheet 1 has excellent heat resistance and metal adhesion at a high level while using such a low-density polyethylene-based resin.

<Manufacturing method of sealing material sheet (first embodiment)>
The first embodiment of the method for producing the encapsulant sheet 1 focuses on the torque value of each layer of the multilayer sheet, selects an encapsulant composition for each of the intermediate layer 11 and the outermost layer 12, and further, This is a method of optimizing the torque value of each layer of the encapsulant sheet within a predetermined range by appropriately controlling the degree of progress of the degree of crosslinking by irradiation with ionizing radiation after melt formation.

  Further, the second embodiment of the method for producing a sealing material sheet of the present invention allows the weak crosslinking to proceed during film formation, and the torque value of each layer of the sealing material sheet is controlled by controlling the degree of progress of the crosslinking. How to optimize. In the second embodiment, unlike the first embodiment, a separate cross-linking treatment after film formation is unnecessary. However, there is no need for a separate cross-linking step after film formation, and the amount of cross-linking agent added to advance weak cross-linking during film formation and the range of film formation temperature conditions are different. The embodiment is a process similar to the first embodiment. Hereinafter, first, the manufacturing method of the 1st embodiment of the manufacturing method of the sealing material sheet of this invention is demonstrated.

[Sheet making process]
The melt molding of each composition for the intermediate layer and the outermost layer is performed by molding methods usually used in ordinary thermoplastic resins, that is, by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. Done. As an example of the forming method as the multilayer sheet, a method of forming by co-extrusion using two or more types of melt-kneading extruders can be given.

  The lower limit of the molding temperature during molding may be any temperature that exceeds the melting point of the encapsulant composition. The upper limit of the molding temperature is, when a crosslinking agent is used, the temperature at which crosslinking does not start during film formation, that is, the gel fraction of the encapsulant composition, according to the 1 minute half-life temperature of the crosslinking agent. Any temperature that can be maintained at 0% may be used.

  Here, in the manufacturing method (first embodiment) of the encapsulant sheet of the present invention, the crosslinking agent is not essential in the encapsulant composition, and even when a crosslinking agent is added, The content is less than 0.5% by mass. For this reason, under a normal low density polyethylene resin molding temperature, for example, a heating condition of about 120 ° C., the gel fraction does not change, and the crosslinking that substantially affects the physical properties of the resin does not proceed. According to the production method of the present invention that maintains the gel fraction of the encapsulant composition during film formation at 0%, the load on the extruder and the like during film formation is reduced, and the productivity of the encapsulant sheet is increased. It is possible.

[Crosslinking process]
A cross-linking step of performing a cross-linking process by ionizing radiation on the uncross-linked encapsulant sheet after the sheet forming step is integrated with the other members after the completion of the sheet forming step. Performed before the start of the solar cell module integration step. By this crosslinking treatment, a sealing material sheet having a gel fraction of 2% to 80% is obtained. The cross-linking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line.

  Regarding the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited. Unlike the conventional method, the method for producing a sealing material sheet of the present invention basically optimizes the degree of crosslinking by limiting the physical properties on the composition side, without fine adjustment of irradiation conditions. This is because it is a method. As a rough standard of specific irradiation amount, it may be appropriately set so that the gel fraction of the intermediate layer after the crosslinking treatment is in a range of about 10% or more. Specifically, it can be performed by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. The acceleration voltage in electron beam irradiation is determined by the thickness of the sheet that is the object to be irradiated, and the thicker the sheet, the larger the acceleration voltage is required. For example, a 0.5 mm-thick sheet is irradiated with 100 kV or more, preferably 200 kV or more. If the accelerating voltage is lower than this, crosslinking of the intermediate layer does not proceed sufficiently. The irradiation dose is in the range of 5 kGy to 500 kGy, preferably 5 to 200 kGy. When the irradiation dose is less than 5 kGy, the crosslinking of the intermediate layer does not proceed sufficiently, and when it exceeds 500 kGy, there is a concern about deformation or coloring of the sealing material sheet due to the generated heat. Irradiation with ionizing radiation may be performed from one side or from both sides as long as the crosslinking of the intermediate layer can sufficiently proceed to the above-described level. Irradiation may be in an air atmosphere or a nitrogen atmosphere.

  Here, the gel fraction (%) means that 0.1 g of a sealing material sheet is put in a resin mesh, extracted with 60 ° C. toluene for 4 hours, taken out together with the resin mesh, weighed after drying, and mass before and after extraction. Comparison is made and the mass% of the remaining insoluble matter is measured, and this is used as the gel fraction.

  According to the production method of the present invention, by setting the irradiation condition that optimizes the progress of crosslinking of the intermediate layer as described above, it is possible to appropriately suppress the progress of the crosslinking of the outermost layer under the irradiation condition. It can be realized at the same time. For this reason, management of crosslinking conditions is easy, and productivity can be improved by releasing from complicated and complicated management of crosslinking conditions. Further, the setting of the irradiation condition is not necessarily limited to the gel fraction. For example, the thermal shrinkage rate after crosslinking of the sample sealing material sheet may be measured at an initial stage, the result may be fed back to the initial irradiation conditions, and thereafter irradiation may be continued under the same conditions. .

  This crosslinking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line. Further, when the crosslinking treatment is a general heat treatment, generally, the content of the crosslinking agent is 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of all components of the sealing material sheet. However, in the sealing material sheet of the present invention, the content of the crosslinking agent may be 0, and even if it is contained, it is preferably less than 0.5 parts by mass. Thereby, the risk of the productivity fall by gelatinization of the sealing material composition in the sheeting process of a sealing material composition can be reduced. In addition, since the sealing material sheet | seat of this invention obtained by doing in this way has been bridge | crosslinked, the annealing process etc. again are unnecessary and can be used in a modularization process as it is.

<The manufacturing method of a sealing material sheet (2nd embodiment)>
In the second embodiment of the method for producing the encapsulant sheet of the present invention, the amount of the crosslinking agent added to the encapsulant composition is increased in an appropriate amount range that does not lead to a decrease in film-formability, and during the film formation This is a method of adjusting the torque value of each layer of the encapsulant sheet 1 to an optimum range unique to the present application by advancing weak crosslinking and appropriately controlling this. Hereinafter, about the 2nd embodiment of the manufacturing method of the sealing material sheet of this invention, description is abbreviate | omitted about the part similar to a 1st embodiment, and only a different part from a 1st embodiment is demonstrated.

  When manufacturing the sealing material sheet 1 by this 2nd embodiment, 0.02 mass% or more and less than 0.5 mass% crosslinking agent are added with respect to all the resin components of a sealing material composition. .

  The sheet formation of the sealing material sheet in the second embodiment can be performed by the same method as in the first embodiment. However, in order to promote a weak cross-linking reaction during molding, the molding temperature is preferably the melting point of the polyethylene resin constituting the sealing material composition + 50 ° C or higher. Specifically, a high temperature of 150 to 250 ° C. is preferable, and a range of 190 to 230 ° C. is more preferable. Since the molding temperature is equal to or higher than the 1 minute half-life temperature of the crosslinking agent, the crosslinking agent hardly remains after molding. For this reason, the weak crosslinking ends at this molding stage.

<Solar cell module>
Next, a preferred embodiment of the solar cell module of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view showing an example of the layer structure of the solar cell module 10 including the back contact solar cell element 6 and the current collector sheet 4 according to an embodiment of the present invention. The solar cell module 10 includes, from the light receiving surface side of incident light 7, the glass substrate 3, the solar cell element 6 disposed on the glass encapsulant sheet 1 of the present invention, and the current collector sheet 4, and the back side encapsulant sheet 2. And the back surface protection sheet 5 is laminated | stacked in order. The current collector sheet 4 is formed by densely forming a metal wiring portion 42 made of a copper foil or the like on a resin base material 41. The solar cell module 10 uses the encapsulant sheet 1 of the present invention for at least a layer requiring close contact with a metal wiring part such as the metal wiring part 42. About the back surface side sealing material sheet 2 arrange | positioned at the back surface of the resin base material 41 of a current collection sheet, although the sealing material sheet of this invention may be used like the surface side, it is not essential. For example, an optimal sealing material sheet can be selected as appropriate, such as using a white sealing material sheet excellent in light reflectivity.

  Here, since the sealing material sheet laminated on the metal wiring portion 42 and the solar cell element 6 of the current collector sheet 4 is required to have an impact buffering function and further an insulating function, a particularly high level of metal adhesion is provided. Required. The encapsulant sheet 1 of the present invention can be laminated and used on either the light-receiving surface side or the non-light-receiving surface side of the solar cell element 6, but has extremely good metal adhesion. In the solar cell module 10 using the back contact solar cell element 6, it can be particularly preferably used when it is disposed on the surface (light receiving surface side) of the current collector sheet 4 facing the metal wiring portion 42.

  In addition, when the sealing material sheet of this invention is a sealing material sheet which consists of two layers of the intermediate | middle layer 11 and the outermost layer 12 of one layer arrange | positioned at the outermost layer of one side, The exposed surface is laminated in the same manner as described above as a layer in close contact with the metal wiring part 42 of the current collector sheet 4.

  The solar cell module 10 is used as a solar cell module particularly when used in a high-temperature environment by using the encapsulant sheet 1 laminated at least at a position facing the metal wiring part 42 of the current collector sheet 4. It combines heat resistance and water vapor barrier properties and durability supported by high metal adhesion at a high level.

  Further, for example, even when the solar cell element is a thin-film solar cell element and only the metal electrode portion has a protruding shape, the encapsulant sheet 1 has a torque value of Due to the excellent molding characteristics of the small outermost layer 12, it is possible to sufficiently follow such irregularities and ensure high adhesion.

  Furthermore, as another preferred embodiment of the solar cell module of the present invention, a solar cell module including a configuration in which the current collector sheet and the sealing material sheet of the present invention are integrated can be exemplified.

  The solar cell module 10 is formed by sequentially laminating the respective members including the encapsulant sheet 1, the current collector sheet 4, and the solar cell element 6 and then integrating them by vacuum suction or the like, and then by a molding method such as a lamination method. These members can be manufactured by thermocompression molding as an integral molded body.

  The thermocompression treatment at the time of manufacturing the solar cell module 10 of the present invention is performed under such heating conditions that the resin temperature of the encapsulant sheet 1 during the thermocompression treatment is 50 ° C. or more and 100 ° C. or less. It can be carried out. For example, when a conventional EVA sealing material is used, heating exceeding 140 ° C. is generally essential. In addition, since a general polyethylene-based sealing material sheet has a low crosslinking rate, when it is used, for example, when laminating is performed at a temperature of 140 ° C. or lower, heating for a long time is required. There are disadvantages such as a large change in film thickness, or the need for a second heat cure after integration. In the solar cell module 10 of the present invention, the solar cell module can be manufactured in a preferable aspect even within the range of the heating conditions. By making the heating condition in the integration process at the time of modularization into such a low temperature range, the productivity and quality stability of the solar cell module can be enhanced.

  In addition, in the solar cell module 10 of this invention, conventionally well-known material can be especially used for the glass substrate 3, solar cell element 6, and back surface protection sheet 5 which are members other than the sealing material sheet 1 without a restriction | limiting. Moreover, the solar cell module 10 of this invention may also contain members other than the said member. In addition, the sealing material sheet | seat of this invention is preferably applicable not only to the solar cell module 10 provided with the back contact type solar cell element 6, but all the other solar cell modules.

  The resin temperature of the encapsulant sheet can be measured by attaching a temperature sensor thermocouple to the upper surface of the encapsulant sheet during heating and using a temperature / humidity data logger. The resin temperature refers to, for example, the resin temperature of the sealing material sheet measured as described above.

  While the present invention has been specifically described with reference to the embodiment, the present invention is not limited to the above embodiment, and can be implemented with appropriate modifications within the scope of the present invention.

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

<Manufacture of encapsulant sheet for solar cell module>
The encapsulant composition raw materials described below were mixed in the proportions (parts by mass) shown in Table 1 below to obtain compositions for intermediate layers and compositions for outermost layers of the encapsulant sheets of Examples and Comparative Examples, respectively. Using each sealing material composition for an intermediate layer and an outermost layer at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a film forming machine having a 200-mm wide T-die Each resin sheet was produced, each of these resin sheets was laminated, and the sealing material sheet of the three-layer structure of the Example and comparative example provided with an intermediate | middle layer and both outermost layers was manufactured. The total thickness of each sealing material in Examples and Comparative Examples, and the thickness of each layer and the thickness ratio of each layer to the total thickness were as shown in Table 2 below.

The following raw materials were used as a sealing material composition raw material for molding each resin sheet for a sealing material.
Base resin 1 (indicated as “P1” in Table 1, the same shall apply hereinafter): density 0.880 g / cm ³ , melting point 60 ° C., metallocene linear chain having MFR at 190 ° C. of 3.5 g / 10 min Low density polyethylene (M-LLDPE).
Base resin 2 (“P2”): metallocene linear low density polyethylene (M-LLDPE) having a density of 0.885 g / cm ³ , a melting point of 66 ° C., and an MFR at 190 ° C. of 3.6 g / 10 min. .
Base resin 3 (“P3”): Metallocene linear low density polyethylene (M-LLDPE) having a density of 0.885 g / cm ³ , a melting point of 66 ° C., and an MFR at 190 ° C. of 19 g / 10 min.
Silane-modified polyethylene resin 1 (“S1”): 2 parts by mass of vinyltrimethoxysilane with respect to 100 parts by mass of metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and an MFR of 30 g / 10 min. And silane-modified polyethylene resin obtained by mixing 0.15 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200 ° C. Density 0.880 g / cm ³ , MFR 13.0 g / 10 min. Melting point 60 ° C.
Silane-modified polyethylene resin 2 (“S2”): vinyl trimethoxysilane 2 with respect to 100 parts by mass of metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and an MFR of 3.5 g / 10 min. A silane-modified polyethylene resin obtained by mixing mass parts and 0.15 mass parts of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200 ° C. Density 0.880 g / cm ³ , MFR 1.0 g / 10 min. Melting point 60 ° C.
Cross-linking agent ("cross-linking agent"): t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi Corporation, trade name "Lupelox TBEC")

In addition, the following additive was added to each sealing material composition of an Example and a comparative example.
Crosslinking aid: triallyl isocyanurate (Nippon Kasei Co., Ltd., trade name “Tyke”). 0.5 parts by mass are added to each of the sealing material compositions of Examples and Comparative Examples.
UV absorber: manufactured by Chemipro Kasei Co., Ltd., trade name KEMISORB12. Add 0.3 parts by mass to each sealing material composition of Examples and Comparative Examples.
Weathering stabilizer: Ciba Japan Co., Ltd., trade name Tinuvin 770. 0.2 parts by mass is added to each sealing material composition of Examples and Comparative Examples.
Antioxidant: Ciba Japan Co., Ltd., trade name Irganox 1076. 0.05 parts by mass are added to each of the sealing material compositions of Examples and Comparative Examples.

  Next, an electron beam irradiation apparatus (product name EC250 / 15 / manufactured by Iwasaki Electric Co., Ltd.) is applied to the molded sealing material sheets of Examples 1-2 and 4-5 and Comparative Examples 1-3 and 5-6. 180L), an accelerating voltage of 200 kV and an irradiation intensity of each of the intensities shown in Table 1 were applied from both sides to obtain a crosslinked encapsulant sheet.

  And about the sealing material sheet | seat after the shaping | molding of Example 3 and the comparative example 4, it was set as the sealing material sheet of each Example and the comparative example as it was, without performing the crosslinking process by said electron beam irradiation.

  As described above, the torque value for each layer of the prepared sealing material sheets of Examples and Comparative Examples was measured. The measurement was performed according to the above definition, in accordance with JIS K6300-2, using a curast meter under conditions of a temperature of 150 ° C. and a torsional frequency of 100 ± 6 times / minute. The results are shown in Table 2.

  <Evaluation example>

  On the glass substrate (white plate semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm), each of the sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm was laminated and vacuumed at 150 ° C. for 18 minutes. It processed with the heating laminator and the solar cell module evaluation sample was obtained about each Example and the comparative example. These solar cell module evaluation samples were evaluated by measuring heat resistance and metal adhesion under the following test conditions. The results are shown in Table 2.

[Heat-resistant creep test]
Two sealing material sheets of Examples and Comparative Examples cut to 7.5 × 5.0 cm are placed on a glass substrate (white float semi-tempered glass JPT3.2 150 mm × 150 mm × 3.2 mm), and the top A glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) is stacked and subjected to vacuum heating laminator treatment according to the following thermal laminating conditions (a) to (d). About the comparative example, the sample for heat resistance evaluation was obtained. About these heat resistance evaluation samples, the heat resistance creep test on the following test conditions was done, and heat resistance was evaluated.
The measurement is carried out by placing each of the above heat resistance evaluation samples vertically and leaving them at 120 ° C. for 12 hours, and measuring the moving distance of the glass substrate (white float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) after being left to stand. The measurement results were evaluated by the following evaluation criteria A to D.
(Thermal lamination conditions) (a) Vacuum drawing: 4.0 minutes
(B) Pressurization (0 kPa to 100 kPa): 1.5 minutes
(C) Pressure holding (100 kPa): 7.0 minutes
(D) Temperature 150 ° C
(Evaluation criteria) A: Less than 1.5 mm
B: 1.5 mm or more and less than 3.5 mm
C: 3.5 mm or more and less than 5.5 mm
D: 5.5 mm or more

[Metal adhesion test]
The sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm were brought into close contact with each other on a copper foil (75 mm × 50 mm × 0.035 mm), and under the same conditions as the thermal laminating conditions (a) to (d) above. Then, vacuum heating laminator treatment was performed to obtain metal adhesion evaluation samples for the respective examples and comparative examples. For each of these metal adhesion evaluation samples, the adhesion strength under the following test conditions was measured to evaluate the metal adhesion.
In the above-mentioned sample for metal adhesion evaluation, the sealing material sheet adhered on the copper foil was vertically peeled (50 mm / min) with a peel tester (Tensilon Universal Tester RTF-1150-H). The test was conducted and the measurement results were evaluated according to the following evaluation criteria A to D.
Evaluated.
(Evaluation criteria) A: 20.0 N / 15 mm or more
B: 15.0N / 15mm or more and less than 20.0N / 15mm
C: 10.0N / 15mm or more and less than 15.0N / 15mm
D: Less than 10.0N / 15mm

  From Tables 1 and 2, the encapsulant sheet of the present invention in which the torque value of each layer and the thickness of each layer relative to the total thickness are optimized to a specific range is a polyethylene-based sealing material excellent in water vapor barrier. It turns out that it is a sealing material sheet, Comprising: Heat resistance and metal adhesiveness are combined on a high level.

DESCRIPTION OF SYMBOLS 1 Sealing material sheet 11 Intermediate layer 12 Outermost layer 2 Back surface side sealing material sheet 3 Transparent front substrate 4 Current collecting sheet 41 Resin base material 42 Metal wiring part 5 Back surface protection sheet 6 Solar cell element 7 Incident light 10 Solar cell module

Claims (9)

Density 0.870 g / cm ³ or more 0.940 g / cm ³ or less and the intermediate layer to the polyethylene resin as a base resin of a density 0.870 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin as a base resin And an outermost layer, and a plurality of layers including
A multilayer encapsulant sheet having a total thickness of 300 μm or more and 1000 μm or less,
The intermediate layer has a thickness ratio with respect to the total thickness of 0.6 or more and 0.94 or less, and a torque value under the following measurement conditions is 0.11 N · m or more,
The outermost layer has a thickness ratio of the thickness of each single outermost layer to the total thickness in a range of 0.03 to 0.2, and the torque value is less than 0.11 N · m. A sealing material sheet for a certain solar cell module.
[Torque value measurement conditions]
The torque value is measured in accordance with JIS K6300-2 using a curast meter at a temperature of 150 ° C. and a torsional frequency of 100 ± 6 times / minute.   The encapsulant sheet according to claim 1, wherein the intermediate layer has a thickness of 180 μm or more, and the outermost layer has a thickness of 140 μm or less.   The encapsulant sheet according to claim 1 or 2, wherein the polyethylene resin is a metallocene linear low-density polyethylene.   The encapsulant sheet according to any one of claims 1 to 3, wherein the polyethylene resin contains a copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer. It is a manufacturing method of the sealing material sheet according to any one of claims 1 to 4,
Density 0.870 g / cm ³ or more 0.940 g / cm ³ or less and an intermediate layer the intermediate layer composition formed by melting the polyethylene resin as a base resin of a density 0.870 g / cm ³ or more 0.940 g Sheet forming step of forming an uncrosslinked multilayer sheet by laminating an outermost layer formed by melt-molding a composition for outermost layer having a polyethylene resin of / cm ³ or less as a base resin,
A crosslinking step of performing a crosslinking treatment by irradiation of ionizing radiation to the uncrosslinked multilayer sheet,
The content of the crosslinking agent in the intermediate layer composition is 0% by mass or more and less than 0.5% by mass,
The manufacturing method of the sealing material sheet whose content of the crosslinking agent in the said composition for outermost layers is 0 to less than 0.02 mass%.   The method for producing a sealing material sheet according to claim 5, wherein the content of the crosslinking agent in the intermediate layer composition is 0.02% by mass or more and less than 0.5% by mass. It is a manufacturing method of the sealing material sheet according to any one of claims 1 to 4,
Density 0.870 g / cm ³ or more 0.940 g / cm ³ or less and an intermediate layer the intermediate layer composition formed by melting the polyethylene resin as a base resin of a density 0.870 g / cm ³ or more 0.940 g A sheet forming step of forming a preliminary multilayer sheet by laminating an outermost layer obtained by melt-molding a composition for outermost layer having a polyethylene resin of / cm ³ or less as a base resin,
The content of the crosslinking agent in the intermediate layer composition is 0.02% by mass or more and less than 0.5% by mass,
The manufacturing method of the sealing material sheet whose content of the crosslinking agent in the said composition for outermost layers is 0 to less than 0.02 mass%. A solar cell module comprising the encapsulant sheet according to any one of claims 1 to 4 and a solar cell element,
The solar cell module arrange | positioned so that the outermost layer of the said sealing material sheet may face the metal part of the other member which comprises the said solar cell module.   The solar cell element is a back contact type solar cell element, further comprising a current collector sheet in which a metal wiring portion is formed on the surface of a resin base material, and the outermost layer of the encapsulant sheet is formed of the current collector sheet. The solar cell module of Claim 8 arrange | positioned so that a metal wiring part may be faced.

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