JP6287006B2 - Manufacturing method of sealing material sheet for solar cell module - Google Patents

Description

  The present invention relates to a method for producing 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 and proposed. Generally, a solar cell module has a configuration in which a transparent front substrate made of glass or the like, a solar cell element, and a back surface protection sheet are laminated via a sealing material sheet.

  As the solar cell element, in addition to a crystalline silicon solar cell manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate, amorphous silicon or microcrystalline silicon is formed on a substrate such as glass and is extremely thin silicon of about 1 μm or less. There is a thin film solar cell element formed by forming a film. As the thin film solar cell element, there is a compound solar cell using a chalcopyrite compound or the like instead of the silicon. Since all solar cell elements are vulnerable to physical impact and are expected to be used outdoors for a long period of time, solar cell modules including those solar cell elements are required to have high weather resistance and durability. It is done.

  As a sealing material sheet for a solar cell module, a sheet based on EVA (ethylene-vinyl acetate copolymer) excellent in transparency, adhesion and the like has been widely used. However, in recent years, development of a sealing material sheet using a polyethylene resin having a transparency equivalent to EVA and excellent in hydrolysis resistance and the like as compared with EVA has been progressing.

  For example, while the base resin is a polyethylene resin, it can be extruded at a low temperature and can be post-crosslinked. As a result, the solar cell module has excellent transparency, adhesion, and durability. As the encapsulant sheet, an encapsulant composition containing a low-density, low-melting silane-modified polyethylene resin obtained by graft polymerization of an ethylenically unsaturated silane compound on linear low-density polyethylene and a crosslinking agent was used. A sealing material sheet has been proposed (see Patent Document 1).

  However, the above-described encapsulant sheet using a low-density polyethylene-based resin as a base resin still has room for improvement in heat resistance after modularization due to its low density. Therefore, the heat resistance of the encapsulant sheet is improved by crosslinking a low-density polyethylene resin by heat treatment. Such a sealing material sheet comprising a sealing material composition containing a low-density polyethylene-based resin as a base resin and further containing a crosslinking agent must be subjected to a crosslinking treatment by heating in any process until modularization. .

  On the other hand, Patent Documents 2 and 3 disclose a technique for imparting heat resistance by omitting a long-time heat curing step by irradiating a polyethylene resin or the like with ionizing radiation for crosslinking.

  The sealing material sheet described in Patent Document 1 has a problem in that it is difficult to improve the productivity of the solar cell module due to the limitation of the manufacturing conditions accompanying the implementation of the thermal crosslinking treatment.

  According to the manufacturing method of the sealing material sheet which performs the crosslinking process by irradiating with ionizing radiation as in Patent Documents 2 and 3, it is freed from the temperature conditions of the thermal crosslinking process, and a certain degree of productivity improvement can be expected. . However, if a sufficient amount of cross-linking treatment is required to provide sufficient heat resistance to withstand long-term use at high temperatures, the ability to follow the irregularities of other components when modularized (hereinafter referred to as the following) , "Molding characteristics").

  In particular, in solar cell modules using thin-film solar cell elements that have recently been on a growing trend, demands for both heat resistance, adhesion, and molding characteristics are required at extremely high levels. However, according to any of the manufacturing methods disclosed in Patent Documents 1 to 3, it has been extremely difficult to produce a sealing material sheet with high productivity while satisfying the required level of such physical properties. This problem was a common problem for all solar cell modules, but was particularly a serious problem in solar cell modules including thin film solar cell elements.

Japanese Patent Laid-Open No. 2002-235048 JP 2009-249556 A JP 2011-77357 A

  The present invention has been made in view of the above situation, and uses a polyethylene resin having excellent hydrolysis resistance as a base resin, and has improved heat resistance by performing a crosslinking treatment by irradiation with ionizing radiation. An object of the present invention is to provide a sealing sheet that is a material sheet and has extremely excellent adhesion and molding characteristics.

  As a result of intensive studies, the inventors of the present invention have manufactured a sealing material sheet for solar cells with a crosslinking treatment by irradiation with ionizing radiation, and the sealing material sheet is a multilayer sheet and is contained in the outermost layer. Compared to the case where the MFR of the entire outermost layer is simply increased to an appropriate size by making the MFR of the adhesive copolymer resin to be larger than the MFR of the base resin contained in the outermost layer, It has been found that a sealing material sheet having better adhesion and molding characteristics can be obtained while maintaining preferable heat resistance, and the present invention has been completed. More specifically, the present invention provides the following.

(1) A method for producing a sealing material sheet for a solar cell module, comprising: an intermediate layer comprising a sealing material composition for an intermediate layer; and an outermost layer comprising a sealing material composition for an outermost layer. A sheet forming step of laminating and forming a multilayer sheet; and a crosslinking step of performing a crosslinking treatment on the multilayer sheet by irradiation with ionizing radiation, wherein the sealing material composition for the outermost layer has a density of 0.00. contains a base resin for the outermost layer consisting of 870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin, an adhesion copolymer resin, wherein the adhesion copolymer resin after the crosslinking step The manufacturing method of the sealing material sheet | seat for solar cell modules characterized by MFR of being larger than MFR of the base resin for said outermost layers after the said bridge | crosslinking process.

  (2) The method for producing a sealing material sheet according to (1), wherein the adhesive copolymer resin is a silane-modified polyethylene resin.

  (3) The MFR of the adhesive copolymer resin after the crosslinking step exceeds 140% of the MFR of the base resin for the outermost layer after the crosslinking step and is 780% or less (1) or (2 ) Manufacturing method of the sealing material sheet.

(4) sealing material composition for the intermediate layer contains a base resin for the intermediate layer consisting of a density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin, for the intermediate layer Any one of (1) to (3), wherein the base resin is a resin having a larger number of full double bonds per 2000 carbon by infrared absorption spectroscopy than the base resin for the outermost layer The manufacturing method of the sealing material sheet of description.

(5) A solar cell module encapsulant sheet that has been subjected to crosslinking treatment by irradiation with ionizing radiation, wherein the encapsulant sheet is a multilayer sheet comprising an intermediate layer and an outermost layer, the outermost layer, the base resin for the outermost layer consisting of a density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin, an adhesion copolymer resin consisting of silane-modified polyethylene resin, a An encapsulant sheet comprising: the adhesive copolymer resin after the cross-linking step, wherein the MFR of the adhesive copolymer resin is larger than the MFR of the base resin for the outermost layer.

  (6) The encapsulant sheet according to (5), wherein the MFR of the adhesive copolymer resin after the crosslinking step exceeds 140% of the MFR of the base resin for the outermost layer and is 780% or less.

  (7) The sealing material sheet manufactured by the manufacturing method according to any one of (1) to (4), or the sealing material sheet according to (5) or (6), a solar cell element, It is a solar cell module provided with this, Comprising: The solar cell module arrange | positioned so that the said outermost layer of the said sealing material sheet may face the metal electrode of the said solar cell element.

  According to the present invention, a sealing material sheet having a heat resistance sufficiently improved by a crosslinking treatment by irradiation with ionizing radiation using a polyethylene resin having excellent hydrolysis resistance and the like as a base resin, and excellent A sealing material sheet having adhesion and molding characteristics can be provided.

It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the sealing material sheet which can be manufactured with the manufacturing method of this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module using the sealing material sheet | seat which can be manufactured with the manufacturing method of this invention, and a thin film type solar cell element.

  Hereinafter, first, an encapsulant composition (hereinafter also simply referred to as “encapsulant composition”) that can be preferably used in the method for producing an encapsulant sheet for a solar cell module of the present invention, for a solar cell module The encapsulant sheet (hereinafter also simply referred to as “encapsulant sheet”) and its manufacturing method, and the solar cell module using the encapsulant sheet of the present invention and its manufacturing method will be described in order. 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.

<Encapsulant composition>
The sealing material sheet of this invention is a sealing material sheet for solar cell modules manufactured by performing the crosslinking process by ionizing radiation after melt molding of a sealing material composition. The sealing material sheet of the present invention is a multilayer sealing material sheet comprising an intermediate layer and an outermost layer. And the sealing material composition for outermost layer for forming the outermost layer arrange | positioned on the outermost surface of a multilayer sealing material sheet is the base resin which consists of a low density polyethylene resin, silane modified polyethylene resin, etc. And an adhesive copolymer resin. Further, the sealing material composition for the intermediate layer for forming the intermediate layer is also based on the low density polyethylene resin, but unlike the sealing material composition for the outermost layer, the adhesive copolymer resin is It is not an essential component.

[Encapsulant composition for outermost layer]
The sealing material composition for the outermost layer is used for molding the outermost layer formed on at least one outer surface, preferably both outermost surfaces of the multilayer sealing material sheet of the present invention. It is. The sealing material composition for the outermost layer contains, as essential components, a base resin made of a polyethylene resin and an adhesive copolymer resin made of a silane-modified polyethylene resin or the like.

  And, the sealing material composition for the outermost layer is such that the MFR after the crosslinking treatment by the ionizing radiation of the adhesive copolymer resin which is an essential component is larger than the MFR after the crosslinking treatment of the base resin. The material resin of the composition is appropriately selected in advance. More specifically, it is preferable that the MFR of the adhesive copolymer resin after crosslinking exceeds 140% of the MFR of the base resin for the outermost layer after crosslinking and becomes 780% or less. Thereby, although it is the sealing material sheet which improved heat resistance by sufficient bridge | crosslinking progressing, it can hold | maintain also about adhesiveness and a molding characteristic in a preferable range. In the present specification, “MFR” means “MFR” at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2 unless otherwise specified.

  In order to control the relative magnitude relationship of the MFR of the base resin and the adhesive copolymer resin after crosslinking within the above range (over 140% and 780% or less), the sealing material composition for the outermost layer is used. The MFR at the composition stage of the silane-modified polyethylene resin to be added may be about 130% to 740% of the MFR at the composition stage of the base resin. Regarding the selection of the MFR of the material at the composition preparation stage, in addition to the selection of both the base resin and the silane-modified polyethylene resin, the type and amount of the crosslinking agent added to the sealing material composition, and the ionizing radiation It is desirable to make fine adjustments in consideration of the crosslinking conditions such as the irradiation amount, but the MFR ratio of the material resin at the composition stage is within the above range as long as it is within the range of crosslinking conditions by irradiation of ionizing radiation that can be generally assumed. By setting it to (about 130% or more and about 740% or less), the MFR ratio of the resin after the crosslinking treatment can be within the above preferable range (over 140% and 780% or less).

(Base resin)
As the polyethylene resin used as the base resin of the sealing material composition for the outermost layer (hereinafter also referred to as “base resin for the outermost layer”), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or Metallocene linear low density polyethylene (M-LLDPE) can be suitably used as appropriate.

The density of the polyethylene resin used as the base resin for the outermost layer is preferably 0.870 or more and 0.900 g / cm ³ or less. And it is preferable that the density of base resin for outermost layers is a lower density than the base resin of the sealing material composition for intermediate | middle layers. By setting the density of the base resin for the outermost layer within the above range, sufficient adhesion and molding characteristics can be imparted while maintaining the protection performance of the solar cell element.

  The outermost layer base resin is preferably a resin having an MFR of 0.6 g / 10 min or more and 1.6 g / 10 min or less after the crosslinking treatment by irradiation with ionizing radiation. The base resin for the outermost layer is preferably a resin having a larger MFR than the base resin of the encapsulant composition for the intermediate layer (hereinafter also referred to as “base resin for the intermediate layer”). Thereby, the adhesiveness and molding characteristic of a sealing material sheet can be hold | maintained in a preferable range.

  On the other hand, as the base resin for the outermost layer, a polyethylene-based resin in which the number of full double bonds remaining in the composition stage is relatively smaller than the number of full double bonds of the base resin for the intermediate layer should be used. Is preferred. The number of full double bonds of the polyethylene resin that is the base resin for the outermost layer is preferably 0 or more and 1.0 or less, and more preferably 0 or more and 0.5 or less.

  By combining the number of full double bonds of the encapsulant composition for the outermost layer in the combination with the encapsulant composition for the intermediate layer relatively within the above range, crosslinking by irradiation with ionizing radiation is appropriate. Therefore, the molding property of the encapsulant sheet can be maintained in a preferable mode. On the other hand, even if the cross-linking of the outermost layer is suppressed in this way, as detailed above, the total double bond number of the encapsulant composition for the intermediate layer is the same as that of the encapsulant composition for the outermost layer. By limiting to a different range, the progress of crosslinking of the intermediate layer can be promoted in a mode different from that of the outermost layer, and as a result, preferable heat resistance can be maintained as the whole sealing material sheet. In addition, it is not preferable that the number of full double bonds of the sealing material composition for the outermost layer exceeds 0.5 because molding characteristics and adhesiveness deteriorate due to the progress of crosslinking.

Here, “the number of full double bonds” in the present specification means the sheet density d (g / cm ³ ) and sheet thickness t (cm) of the encapsulant composition in the sheet state and the absorption band of the infrared absorption spectrum. It is the value calculated | required by the following formula from the absorbance A of. In addition, about the measurement of the light absorbency A of the absorption band of an infrared absorption spectrum, it carried out by NICOLET6700 made from Thermo Scientific.
Number of terminal vinyl groups = 0.231 / (d × t) × A (910 cm ⁻¹ )
Vinylidene base = 0.271 / (d × t) × A (888 cm ⁻¹ )
Number of trans vinylene groups = 0.328 / (d × t) × A (965 cm ⁻¹ )
Total number of double bonds = number of terminal vinyl groups + number of vinylidene groups + number of transvinylene groups The total number of double bonds per 2000 carbons by the above method.

(Adhesive copolymer resin)
The sealing material composition for the outermost layer contains, as an essential component, an adhesive copolymer resin typified by a silane-modified polyethylene resin in addition to the base resin. The adhesive copolymer resin in the present invention is not necessarily limited to the silane-modified polyethylene resin as long as the adhesion improving component is a resin that has been polymerized in advance. Other epoxy-modified, polyethylene-based resins modified with unsaturated carboxylic acid or derivatives thereof may be used. Examples of unsaturated carboxylic acids include maleic acid, itaconic acid, and fumaric acid. Examples of derivatives thereof include maleic acid monoester, maleic acid diester, maleic anhydride, itaconic acid monoester, itaconic acid. Examples thereof include esters and anhydrides such as diester, itaconic anhydride, fumaric acid monoester, fumaric acid diester, and fumaric anhydride. However, a silane-modified polyethylene resin can be particularly preferably used from the viewpoints of compatibility with the base resin and adhesion with other solar cell module components such as a glass substrate. Hereinafter, the case where the adhesive copolymer resin is a silane-modified polyethylene resin will be described in detail as a specific example of a preferred embodiment of the present invention.

(Silane-modified polyethylene resin)
The silane-modified polyethylene resin is a resin obtained by graft polymerizing low-density polyethylene as a main chain, preferably linear low-density polyethylene, with an ethylenically unsaturated silane compound as a side chain. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, it can improve the adhesion of the sealing material sheet to other members in the solar cell module. The silane-modified polyethylene resin in the present specification refers to, for example, a silane-modified polyethylene resin that can be produced by the following production method, and at least a part of a linear low-density polyethylene resin that becomes a main chain. Is a concept indicating a resin obtained by graft polymerization with an ethylenically unsaturated silane compound. The resin as a main chain of the above, as with the base resin, it is preferred that the density 0.870 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin.

The silane-modified polyethylene resin can be produced by the following method, for example, as described in JP-A-2003-46105. For example, one or more α-olefins, one or more ethylenically unsaturated silane compounds, and, if necessary, one or more other unsaturated monomers are desired. reactions using the container, for example, a pressure 500~4000Kg / cm ^2-position, preferably, 1000~4000Kg / cm ^2-position, temperature, 100 to 400 ° C.-position, preferably under the conditions of 150 to 350 ° C.-position, Part of the silane compound constituting the random copolymer which is produced by random copolymerization simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent. Can be modified or condensed to produce a silane-modified polyethylene resin.

  As the polyethylene-based resin of the main chain, it is preferable to use linear low-density polyethylene that is an ethylene-α-olefin copolymer, and it is more preferable to use metallocene-based 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 comonomer distribution. For this reason, molecular weight distribution is narrow, it is possible to make it the above ultra-low density, and a softness | flexibility can be provided with respect to a sealing material sheet. As a result of the flexibility imparted to the sealing material sheet, the adhesion between the sealing material sheet and a transparent front substrate such as glass can be enhanced.

  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 number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material sheet can be given good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and a transparent front substrate such as glass is further enhanced.

  Examples of ethylenically unsaturated silane compounds to be graft polymerized with linear low density polyethylene include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane , One or more selected from vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane be able to.

  The graft amount, which is the content of the ethylenically unsaturated silane compound in the silane-modified polyethylene resin, is 0.001 to 15% by mass, preferably 0.01 to 5% by mass in the base resin of the silane-modified polyethylene resin. %, Particularly preferably 0.05 to 2% by mass. 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.

  Content in the sealing material composition for outermost layers of the silane modified polyethylene resin used for the sealing material composition for outermost layers of the sealing material sheet of this invention is adhesiveness with the base resin of sealing material composition. The content in 100 parts by mass of the resin component made of the copolymer resin is preferably 8 parts by mass or more and 20 parts by mass or less. In the present invention, if the content of the silane-modified polyethylene resin is 8 parts by mass or more, it is excellent in mechanical strength and heat resistance, but if the content is excessive, it tends to be inferior in tensile elongation and heat-fusibility. It is in.

  By using the silane-modified polyethylene-based resin described above as a component of the sealing material composition for the outer layer among the sealing material composition for the solar cell module, it has excellent adhesion, strength, durability, etc., and In addition, a sealing material sheet excellent in weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other various characteristics can be obtained. Various effects can be obtained in this way by using a silane-modified polyethylene resin, but it is extremely excellent in a sealing material sheet without being affected by manufacturing conditions such as thermocompression bonding for manufacturing a solar cell module. In addition, the greatest advantage is that it can impart excellent heat adhesion to the glass substrate constituting the solar cell module.

[Encapsulant composition for intermediate layer]
The intermediate layer sealing material composition uses a polyethylene-based resin as a base resin in the same manner as the outermost layer sealing material composition. In addition, the adhesive copolymer resin that is an essential component of the sealing material composition for the outer layer is not an essential component in the sealing material composition for the intermediate layer.

(Base resin)
The polyethylene resin used as the base resin for the intermediate layer is a low density polyethylene (LDPE), a linear low density polyethylene (LLDPE), or a metallocene linear chain, similar to the base resin of the sealing material composition for the outermost layer. Low density polyethylene (M-LLDPE) can be preferably used.

The density of the polyethylene resin used as the base resin for the intermediate layer is 0.870 or more and 0.970 g / cm ³ or less, preferably 0.870 or more and 0.930 g / cm ³ or less. The density of the base resin for the intermediate layer is preferably higher than that of the base resin for the outermost layer. By setting the density of the base resin for the intermediate layer within the above range, sufficient heat resistance can be imparted to the sealing material while maintaining the molding characteristics and the protection performance of the solar cell element.

  The base resin for the intermediate layer is preferably a resin having an MFR of 0.1 g / 10 min or more and 4 g / 10 min or less after crosslinking treatment by irradiation with ionizing radiation, which will be described in detail later. The intermediate layer base resin preferably has a smaller MFR than the outermost layer base resin. Thereby, the heat resistance of a sealing material sheet can be hold | maintained in a preferable range.

  Further, the base resin for the intermediate layer is preferably a polyethylene resin in which the number of full double bonds remaining in the composition stage is relatively larger than the number of full double bonds of the base resin for the outermost layer. . Further, the number of full double bonds of the base resin for the intermediate layer is preferably 0.5 or more and 4.0 or less, and more preferably 1.0 or more and 4.0 or less.

  The content of the base resin contained in the intermediate layer sealing material composition is preferably 10 parts by mass or more and 99 parts by mass with respect to 100 parts by mass in total of all resin components in the intermediate layer sealing material composition. It is 50 parts by mass or less, more preferably 50 parts by mass or more and 99 parts by mass or less, and still more preferably 90 parts by mass or more and 99 parts by mass or less. Other resins may be included as long as the number of residual double bonds at the composition stage falls within the above range. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later. In the present specification, the term “all resin components” includes the other resins described above.

  By setting the number of full double bonds of the encapsulant composition for the intermediate layer within the above range, the heat resistance of the encapsulant sheet can be sufficiently improved by sufficiently proceeding with crosslinking by irradiation with ionizing radiation. it can. On the other hand, even if the crosslinking of the intermediate layer by irradiation with ionizing radiation is sufficiently advanced, the total number of double bonds of the sealing material composition for the outermost layer is different from that of the sealing material composition for the intermediate layer By limiting to, the progress of crosslinking of the outermost layer is suppressed in a mode different from that of the intermediate layer, and as a result, preferable molding characteristics can be maintained as the whole sealing material sheet. In addition, the heat resistance of a sealing material sheet is not fully improved as the number of full double bonds of the sealing material composition for intermediate | middle layers is less than 0.5 piece. On the other hand, when the number exceeds 4.0, molding characteristics and adhesion are deteriorated due to excessive progress of crosslinking, which is not preferable.

[Other additives]
Each of the encapsulant compositions for the intermediate layer and the outermost layer can appropriately contain the following additives.

(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.

  As content of a crosslinking agent, it is preferable that it is content of 0 mass part or more and 0.5 mass part or less with respect to a total of 100 mass parts of all the resin components of a sealing material composition, More preferably, it is 0.02. The range is not less than 0.5 parts by mass. By adding 0.02 parts by mass or more of a crosslinking agent, more preferable heat resistance can be imparted to the polyethylene resin used in the sealing material sheet of the present invention. On the other hand, when the addition amount of the cross-linking agent exceeds 2.0 parts by mass, the progress of cross-linking in the cross-linking step becomes excessive, and molding characteristics become insufficient, which is not preferable.

(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.

  Specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA) , Ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, etc. ) An acryloxy compound, a glycidyl methacrylate containing a double bond and an epoxy group, 4-hydroxybutyl acrylate glycidyl ether and 1, containing two or more epoxy groups - 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. In addition, when this range is exceeded, the film-forming property is deteriorated, and the so-called bleed-out in which the silane coupling agent aggregates and solidifies with time and is pulverized on the surface of the sealing material sheet is not preferable.

(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 parts by mass or more and 3 parts by mass or less, more preferably 0.05 parts by mass or more, with respect to 100 parts by mass in total of all resin components of the encapsulant composition. It is the range of -2.0 mass parts or less.

(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, etc., but in the range of 0.001 to 5 parts by mass with respect to 100 parts by mass in total of all resin components of each sealing material composition. Preferably there is. 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.

<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. . The outermost layer contains an adhesive copolymer resin such as a silane-modified polyethylene resin in addition to the base resin for the outermost layer made of a polyethylene resin, and is manufactured through a crosslinking treatment by irradiation with ionizing radiation. The sealed sealing sheet is characterized in that the MFR of the adhesive copolymer resin is higher than the MFR of the base resin for the outermost layer. Hereinafter, as a preferred embodiment of the present invention, a sealing material 1 having a three-layer structure including two outermost layers in total of one layer above and below a single intermediate layer will be described with reference to FIG. However, the present invention is not limited to this embodiment.

  The sealing material 1 includes an intermediate layer 11, and outermost layers 12 are 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 is given sufficient heat resistance by sufficiently proceeding with cross-linking, whereby the durability of the solar cell module 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 is characterized in that the adhesion component, that is, the MFR of the silane-modified polyethylene resin is made larger than the MFR of the polyethylene resin as the base resin. Thereby, the adhesiveness as a solar cell module and the molding characteristic at the time of an integration process can be improved.

  The sealing material sheet 1 is a multilayer sheet formed by laminating resin sheets each having superior physical properties. This is a cross-linked polyethylene resin having an extremely high water vapor barrier property, and is a sealing material sheet for a solar cell module that is extremely excellent in the balance between heat resistance, adhesion and molding characteristics.

  The total thickness of the sealing material sheet 1 including the intermediate layer 11 and the outermost layer 12 is preferably 100 μm or more and 1000 μm or less, and more preferably 200 μm or more and 600 μm or less. If it is less than 100 μm, the impact cannot be sufficiently mitigated, and if it exceeds 1000 μm, no further effect can be obtained and it is uneconomical. In addition, since the sealing material sheet of the present invention has flexibility in the outermost layer and heat resistance in the intermediate layer, which suppresses flow-out and film thickness change during the laminating process, it is about 500 μm or less. Even when the film is thinned, it is possible to provide sufficiently preferable molding properties, heat resistance, and solar cell element protection performance.

  About the ratio of the thickness of each layer in the sealing material sheet 1, the outermost layer 12: the intermediate layer 11: the outermost layer 12 and the n thickness ratio may be in the range of 1: 2: 1 to 1: 30: 1. preferable. By setting the thickness ratio of each layer within this range, the heat resistance and molding characteristics of the sealing material sheet 1 can be maintained within a favorable range.

<Method for producing sealing material sheet>
[Sheet making process]
The melt molding of each composition for the intermediate layer and the outermost layer, each of which has been described in detail above, is a molding method usually used in ordinary thermoplastic resins, that is, injection molding, extrusion molding, hollow molding, compression molding, It is performed by various molding methods such as rotational molding. As an example of the forming method as the multilayer sheet, a method of forming by co-extrusion with two or more 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 the temperature at which crosslinking does not start during film formation, that is, the temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, depending on the 1 minute half-life temperature of the crosslinking agent used. Good. Here, in the method for producing a sealing material sheet of the present invention, a crosslinking agent is not essential in the sealing material composition, and even when a crosslinking agent is added, its content is less than 0.5% by mass. It is limited to. 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. In addition, as described above, it is possible to use a cross-linking agent having a half-life temperature higher than that of the conventional one by solving from the limitation of the heating conditions in the modularization process. Therefore, even if the molding temperature is set higher than before, the gel fraction of the encapsulant composition can be maintained at 0%. 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. 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. 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. .

  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.

  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.

<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 thin-film solar cell element according to the embodiment of the present invention. In the solar cell module 10, the transparent front substrate 2, the thin-film solar cell element 3 formed on the transparent front substrate 2, the sealing material sheet 1, and the back surface protection sheet 4 are sequentially laminated from the light receiving surface side of incident light. ing.

  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 thin film solar cell element 3.

  In the solar cell module 10, by using the sealing material sheet 1, the heat resistance as the solar cell module, the adhesion at the time of modularization, and the molding characteristics are improved in a well-balanced manner. For example, the thin-film solar cell element 3 generally has a shape in which a metal electrode 31 protrudes as shown in FIG. 2, but the thin molding solar cell element 3 has an excellent molding characteristic of the sealing material sheet 1 of the present invention. For example, the encapsulant sheet 1, the thin-film solar cell element 3, and the transparent front substrate 2 can be integrated with high adhesion by following such unevenness sufficiently.

  The layer configuration of the solar cell module of the present invention is not limited to that according to the above embodiment. Since the sealing material sheet 1 of the present invention has adhesiveness to both glass and metal, taking advantage of its characteristics, the solar cell module of various configurations including a glass substrate and a metallic solar cell module can be used. Can be used for general purposes. For example, in a solar cell module, the encapsulant sheet of the present invention is preferably used even when one surface of the encapsulant sheet faces the metal surface and the other surface opposes the glass layer. be able to.

  Moreover, the structure by which a sealing material sheet | seat is arrange | positioned on the upper and lower surfaces of the solar cell element which has spread widely conventionally, for example may be sufficient as the solar cell module of this invention. In this case, the sealing material sheet of this invention can be laminated | stacked and used for any of the said both surfaces. However, since the encapsulant sheet of the present invention is an encapsulant sheet that is particularly excellent in molding characteristics, that is, the ability to follow the unevenness of the opposing substrate, the lower surface (non- The arrangement on the light receiving surface side is particularly effective.

  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. A current collector sheet is a component of a solar cell module that is generally arranged for the purpose of collecting current from a back contact solar cell element, and a conductive circuit for current collection is formed on the surface of a resin base material. It is what has been. Since the sealing material sheet laminated on the circuit of the current collecting sheet and the solar cell element is required to have an impact buffering function and further an insulating function, the molding characteristics for the uneven shape on the current collecting sheet are specially selected. A high level of physical properties is required. As described above, since the encapsulant sheet of the present invention has extremely good molding characteristics, it can be used very preferably even in a solar cell module including the above-described configuration.

  For example, the solar cell module 10 is formed by sequentially laminating a member composed of the transparent front substrate 2, the sealing material sheet 1 and the back surface protection sheet 4 on which the thin film solar cell element 3 is formed, and then integrating them by vacuum suction or the like. The above members can be manufactured by thermocompression molding as an integral molded body by a molding method such as a lamination method.

  Since the sealing material sheet 1 of the present invention has an MFR of the adhesive copolymer resin of the outermost layer larger than that of the base resin for the outermost layer, at the time of integration as this solar cell module, Since the fluidity of the adhesive copolymer resin is higher than that of the resin, there are more opportunities for the adhesive copolymer resin to adhere at the interface between the glass and the sealing material. For this reason, the sealing material sheet 1 of this invention is excellent about the molding characteristic and adhesiveness.

  In the solar cell module 10 of the present invention, the transparent front substrate 2, the thin film solar cell element 3, and the back surface protection sheet 4 which are members other than the sealing material sheet 1 use conventionally known materials without particular limitation. Can do. 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 a thin film type solar cell element but to all other solar cell modules.

  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 are mixed in the proportions (parts by mass) shown in Table 1 below, and the encapsulant compositions for the intermediate layer and the outermost layer of the encapsulant sheets of Examples and Comparative Examples are respectively used. It was set as the sealing material composition. 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 provided with an intermediate | middle layer and both outermost layers and Comparative Examples 1-2 was manufactured. The thicknesses of the sealing materials in Examples and Comparative Examples were all set to a total thickness of 600 μm. About the ratio of the thickness of each layer of the sealing material having a three-layer structure of the example and the comparative example, the thickness ratio of the outermost layer: intermediate layer: outermost layer is 1: 4: 1 in any sealing material sheet. It was made to become.

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 for outermost layer (denoted as “outer layer 1” in the table, the same applies hereinafter): density is 0.880 g / cm ³ , melting point is 60 ° C., and MFR at 190 ° C. is 3.5 g / 10 minutes. Metallocene linear low density polyethylene (M-LLDPE).
Base resin 2 for outermost layer (“outer layer 2”): metallocene linear low density polyethylene (density 0.885 g / cm ³ , melting point 66 ° C., MFR at 190 ° C. 10.0 g / 10 min) M-LLDPE).
Silane-modified polyethylene resin (“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 3.5 g / 10 min. A silane-modified polyethylene resin obtained by mixing 0.15 parts by mass and 0.15 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst), and melting and kneading at 200 ° C. Density 0.880 g / cm ³ , MFR 2.0 g / 10 min. Melting point 60 ° C.
Silane-modified polyethylene resin (“S2”): 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 20 g / 10 min. A 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 8.0 g / 10 min. Melting point 60 ° C.
Silane-modified polyethylene resin (“S3”): 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 26 g / 10 min. A 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 (“S4”): 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 40 g / 10 min. A 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 26.0 g / 10 min. Melting point 60 ° C.
Base resin for intermediate layer (“intermediate”): metallocene linear low density polyethylene (M) having a density of 0.880 g / cm ³ , a melting point of 60 ° C., and an MFR at 190 ° C. of 3.5 g / 10 min. -LLDPE).
Weathering agent master batch 1 (“MB1 for intermediate layer”): base resin: 100 parts by mass. KEMISTAB62 (HALS): 0.6 parts by mass. KEMISORB 12 (UV absorber): 3.5 parts by mass. KEMISORB 79 (UA absorbent): 0.6 parts by mass. CHIMASORB 202 (UV absorber): 0.07 parts by mass. Tricyclodecane dimethanol diacrylate (crosslinking aid): 2.14 parts by mass.
Weathering agent master batch 2 ([MB2 for intermediate layer]): Base resin: 100 parts by weight. Tricyclodecane dimethanol diacrylate (crosslinking aid): 2.04 parts by mass.
Weathering agent master batch 3 (“MB for outermost layer”): base resin: 100 parts by mass. KEMISTAB62 (HALS): 0.6 parts by mass. KEMISORB 12 (UV absorber): 3.5 parts by mass. KEMISORB 79 (UV absorber): 0.6 parts by mass. CHIMASORB 202 (UV absorber): 0.07 parts by mass.
In addition, 10 mass parts of weatherproofing agent master batches 1 and 2 were added to the compositions for intermediate layers of all Examples and Comparative Examples, respectively. Further, 10 parts by mass of the weatherproofing agent master batch 3 was added to each of the compositions for the outermost layers of all Examples and Comparative Examples.

  Table 1 also shows the MFR before and after the crosslinking treatment by irradiation with ionizing radiation of the base resins 1 and 2 for the outermost layer and the silane-modified resins S1 to S4.

The number of full double bonds and the number of terminal vinyl groups per 2000 carbon derived from the base resin of each sealing material composition of Example 3 and Comparative Example 1 were determined by the following formula. The number of full double bonds per 2000 carbons was determined from the density d (g / cm ³ ), the sheet thickness t (cm), and the absorbance A of the absorption band of the infrared absorption spectrum. Measurement of the absorbance A of the absorption band of the infrared absorption spectrum was performed by NICOLET6700 manufactured by Thermo Scientific. The results are shown in Table 2.
Number of terminal vinyl groups = 0.231 / (d × t) × A (910 cm −1)
Vinylidene base = 0.271 / (d × t) × A (888 cm −1)
Number of trans vinylene groups = 0.328 / (d × t) × A (965 cm −1)
Number of full double bonds = number of terminal vinyl groups + number of vinylidene groups + number of transvinylene groups

  Next, with respect to all the uncrosslinked sealing material sheets after the above-described molding of Examples and Comparative Examples, respectively, using an electron beam irradiation device (Iwasaki Electric Co., Ltd., product name EC250 / 15 / 180L), Both surfaces were irradiated with an acceleration voltage of 200 kV and an irradiation intensity of 40 kGy, and a total of 80 kGy was irradiated to produce a crosslinked encapsulant sheet, which was used as an encapsulant sheet in Examples and Comparative Examples.

<Evaluation Example 1: Heat resistance>
A heat-resistant creep test was conducted. Two sheets of the sealing material sheets of Examples and Comparative Examples cut out to 5 cm × 7.5 cm on a large-sized glass plate which has been subjected to grain processing, and 5 cm × 7.5 cm grain glass are placed on top of each other, 150 ° C. A sample for evaluation was prepared by performing a vacuum heating laminator treatment in 10 minutes. Thereafter, the large format glass was placed vertically and allowed to stand at 150 ° C. for 12 hours, and the moving distance (mm) of the 5 cm × 7.5 cm embossed glass after the standing was measured and evaluated. Evaluation was performed according to the following criteria.
(Evaluation criteria) A: 0.00 mm
B: More than 0.00mm and less than 1.0mm
C: 1.0 mm or more The evaluation results are shown in Table 3 as “heat resistance”.

<Evaluation Example 2: Initial adhesion>
Each sealing material sheet of Examples and Comparative Examples is adhered to a glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) and subjected to vacuum heating laminator treatment at 150 ° C. for 12 minutes for evaluation. A sample was prepared. And in said sample for evaluation, the sealing material sheet | seat closely_contact | adhered on a glass substrate is cut into 15 mm width, and vertical peeling (50 mm / min) with a peeling tester (Tensilon universal testing machine RTF-1150-H). ) A test was conducted to measure and evaluate the glass adhesion strength. Evaluation was performed according to the following criteria.
A: 30 N / 15 mm or more B: 25 N / 15 mm or more and less than 30 N / 15 mm C: 20 N / 15 mm or more and less than 25 N / 15 mm D: Less than 20 N / 15 mm The evaluation results are shown in Table 3 as “adhesiveness”.

<Evaluation Example 3: Molding Characteristics>
On the same glass substrate as that used in the heat-resistant creep test, an aluminum plate having a thickness of 200 μm and 150 mm × 150 mm assuming a pseudo solar cell element is allowed to stand, and a lead wire is further provided on the aluminum plate. (250 μm diameter) is placed, and from above, each of the sealing material sheets of Examples and Comparative Examples cut to 150 mm × 150 mm is laminated and vacuum heated under the same heat laminating conditions as in the heat-resistant creep test. Laminator processing was performed, and solar cell module evaluation samples were obtained for the respective examples and comparative examples. About these solar cell module evaluation samples, molding characteristics were evaluated by visual observation according to the following evaluation criteria.
(Evaluation criteria) A: Completely follows the unevenness of the substrate surface facing the encapsulant sheet.
C: A part of the sealing material sheet does not completely follow the unevenness of the substrate surface facing, and a defective laminate portion occurs.
The evaluation results are shown in Table 3 as “molding characteristics”.

  From Tables 1-3, it turns out that the sealing material sheet | seat of the Example manufactured with the manufacturing method of this invention has heat resistance, adhesiveness, and a molding characteristic at a high level.

Further, from the results of Example 2 and Comparative Example 2, even if the MFR of the adhesive copolymer resin contained in the outermost layer is equivalent, the sealing is caused by the relative magnitude relationship with the MFR of the base resin. It can be seen that the glass adhesion of the material sheet is greatly different. And it turns out that it is the sealing material sheet of this invention which limited the relative magnitude relationship of MFR of both these resin to the original range, and can show a particularly advantageous effect especially about glass adhesiveness.

DESCRIPTION OF SYMBOLS 1 Sealant sheet 11 Intermediate layer 12 Outermost layer 2 Transparent front substrate 3 Thin film solar cell element 31 Metal electrode 4 Back surface protection sheet 10 Solar cell module

Claims (3)

A method for producing a sealing material sheet for a solar cell module,
A sheeting step of forming a multilayer sheet by laminating an intermediate layer made of the sealing material composition for the intermediate layer and an outermost layer made of the sealing material composition for the outermost layer;
A cross-linking step of performing cross-linking treatment by irradiation of ionizing radiation to the multilayer sheet,
The sealing material composition for the outermost layer comprises a base resin for the outermost layer consisting of a density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin, an adhesion copolymer resin, a containing, MFR of the adhesion copolymer resin after the crosslinking step, much larger than the MFR of the base resin for the outermost layer after the crosslinking step,
The sealing material composition for the intermediate layer contains a base resin for the intermediate layer consisting of a density 0.870 g / cm ³ or more 0.970 g / cm ³ or less of the polyethylene resin,
The sealing resin for a solar cell module , wherein the base resin for the intermediate layer is a resin having a greater number of full double bonds per 2000 carbon by infrared absorption spectrum method than the base resin for the outermost layer. A method for manufacturing a stop sheet.   The method for producing a sealing material sheet according to claim 1, wherein the adhesive copolymer resin is a silane-modified polyethylene resin.   The sealing according to claim 1 or 2, wherein the MFR of the adhesive copolymer resin after the crosslinking step is more than 140% and not more than 780% of the MFR of the base resin for the outermost layer after the crosslinking step. A method for manufacturing a stop sheet.

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