JP6972849B2 - Manufacturing method of encapsulant composition for solar cell module and encapsulant sheet for solar cell module - Google Patents

Description

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

In recent years, due to growing awareness of environmental issues, solar cells as a clean energy source have been attracting attention. Currently, solar cell modules having various forms have been developed and proposed. Generally, a solar cell module has a structure in which a transparent front substrate, a solar cell element, and a back surface protective sheet are laminated via a sealing material sheet for the solar cell module (see FIG. 1).

An extremely high light resistance is required for a sealing material sheet for a solar cell module, which is supposed to be exposed to strong sunlight for a long period of time outdoors. As an additive for providing this light resistance, a sealing material sheet using a hindered amine-based light resistance stabilizer (hereinafter, also referred to as “HALS”) has been proposed. (See Patent Document 1).

Furthermore, in order to exert the original effect of improving the light resistance of the hindered amine-based light-resistant stabilizer, while avoiding the deterioration of the optical properties of the encapsulant sheet due to the occurrence of bleed-out due to its overdose, the molecular weight should be increased. It is disclosed that it is preferable to use a hindered amine-based light-resistant stabilizer having a high molecular weight of 1200 or more within a certain amount of addition range (see Patent Document 2). In addition, in this specification, "molecular weight" means "number average molecular weight (Mn)" unless otherwise specified.

In the encapsulant sheet described in Patent Document 1, the light resistance can be improved by adding a hindered amine-based light-resistant stabilizer, and further, as described in Patent Document 2, the hindered amine-based light-resistant stabilizer is highly enhanced. The occurrence of bleed-out can also be suppressed by limiting to the molecular weight type HALS and adding after appropriately adjusting the addition amount.

However, in recent years, conventional products such as higher level heat resistance and long-term durability for solar cell modules, which are expected to be used under a wide range of environmental conditions including deserts and rainforests. The extremely high level of weather resistance that was not expected is now required. In order to meet such a requirement, first, it is conceivable to further increase the amount of the above-mentioned high molecular weight type HALS added. However, while the general high molecular weight type HALS is difficult to bleed out, its compatibility with the resin is not always sufficient. In particular, when a large amount of HALS is to be added to the base resin in order to impart the above-mentioned high weather resistance to the encapsulant sheet, the problem of insufficient compatibility has become apparent. I was supposed to do it.

As a response to this problem, the use of HALS, which is a copolymer of a cyclic aminovinyl compound and ethylene (hereinafter, also referred to as “copolymer type ultrahigh molecular weight type HALS”), has been studied (Patent Document 3). reference). Although this HALS is an ultra-high molecular weight type having a molecular weight of more than 30,000, it is extremely excellent in compatibility with a polyethylene resin.

On the other hand, from the viewpoint of designability or improvement of power generation efficiency, the encapsulant sheet for a solar cell module is often required to have not only the above-mentioned weather resistance but also high transparency at the same time. When a high degree of transparency is required for the encapsulant sheet, it is necessary to limit the haze to a resin having a low density of the base resin and keep the haze sufficiently small. Generally, in this case, the density of polyethylene as a base resin needs to be as low ^{as 0.900 g / cm 3} or less, more preferably 0.880 / cm ^3.

However, as a result of the research by the present inventor, when ^{a low density polyethylene having a sufficiently small haze and a density of 0.880 cm 3} is used as the base resin, the above-mentioned "copolymer type super" having excellent compatibility with the polyethylene resin is excellent. Even if "high molecular weight type HALS" is used, if an amount of a certain amount or more sufficient to meet the above-mentioned requirements for high weather resistance is added, the haze of the encapsulant sheet increases and the above-mentioned low It has come to be recognized that the inherent sufficient transparency of the density base resin cannot be maintained.

Japanese Unexamined Patent Publication No. 2004-214641 Japanese Unexamined Patent Publication No. 2012-9693 Japanese Unexamined Patent Publication No. 2010-155915

The present invention has been made in view of the above circumstances, and it is intended to fully enjoy the excellent effect of improving weather resistance by adding "copolymer type ultrahigh molecular weight type HALS" while maintaining sufficient transparency. It is an object of the present invention to provide an encapsulant sheet for a solar cell module which can be used.

The present inventors have excellent resin compatibility with a hindered amine-based light-resistant stabilizer added to the encapsulant composition used as a material in the production of an encapsulant for a solar cell module using a polyethylene-based resin as a base resin. Not only is it specified as "copolymer type ultra-high molecular weight type HALS", but first, the density of the polyethylene-based resin used as the base resin is limited to a specific low density range with a small haze, and this base resin and its addition are added. By optimizing the formulation of the encapsulant composition so that the density difference from the "copolymer type ultra-high molecular weight type HALS" is within a predetermined range, it has excellent transparency and is highly transparent. We have found that it is possible to produce a sealing material sheet having the weather resistance of the above, and have completed the present invention. More specifically, the present invention provides the following.

(1) A sealing material composition for a solar cell module containing low-density polyethylene as a base resin, a cross-linking agent, and a hindered amine-based light-resistant stabilizer. The hindered amine-based light-resistant stabilizer is a cyclic aminovinyl compound. A copolymer of polyethylene and polyethylene having a molecular weight of 30,000 or more, a density of 0.930 g / cm ³ or more, and a content ratio of the cyclic aminovinyl compound to the base resin of 0.1% by mass or more. It is 2% by mass or less, the density of the base resin is 0.900 g / cm ³ or less, and the difference between the density of the base resin and the density of the hindered amine-based light-resistant stabilizer is 0.050 g /. Encapsulant composition less than cm ^3.

(2) The encapsulant composition according to (1), wherein the content of the cross-linking agent with respect to all the resin components is 0.2% by mass or more and 0.5% by mass or less.

(3) A method for manufacturing a sealing material sheet for a solar cell module, which includes a light-resistant stabilizer selection step, a base resin selection step, a material kneading step, and a sheet-forming step, and the light-resistant sheet is described above. In the stabilizer selection step, a hindered amine-based light-resistant stabilizer, which is a copolymer of a cyclic aminovinyl compound and polyethylene and has a molecular weight of 30,000 or more and a density of 0.930 g / cm ^{3 or more, is selected as the light-resistant stabilizer.} In the base resin selection step, the base resin has a low density of ^{0.900 g / cm 3 or less and a density difference of less than 0.050 g / cm 3 from the} hindered amine-based light-resistant stabilizer. Polyethylene is selected, and in the material kneading step, a cross-linking agent and the hindered amine-based light-resistant stabilizer are added to the low-density polyethylene and kneaded to produce a sealing material composition, and the sheet is produced. In the chemical conversion step, a method for producing a sealing material sheet, wherein the sealing material composition is melt-molded to produce a sealing material sheet.

(4) The amount of the hindered amine-based light-resistant stabilizer added is such that the content ratio of the cyclic aminovinyl compound to the base resin is 0.1% by mass or more and 0.2% by mass or less (3). The method for manufacturing a sealing material sheet according to.

(5) The low-density polyethylene has a density of 0.885 g / cm ³ or more, and the hindered amine-based light-resistant stabilizer has a density of 0.930 g / cm ³ or more, according to (3) or (4). The method for manufacturing a sealing material sheet according to the description.

(6) The content of the cross-linking agent with respect to the base resin is 0.2% by mass or more and 0.5% by mass or less. The method for manufacturing a sealing material sheet according to any one of (3) to (5).

According to the present invention, a seal for a solar cell module capable of fully enjoying the excellent effect of improving weather resistance by adding "copolymer type ultra-high molecular weight type HALS" while maintaining sufficient transparency. A stop material sheet can be manufactured.

It is sectional drawing which shows an example of the layer structure of the solar cell module of this invention.

<Encapsulant sheet>
The encapsulant sheet of the present invention (hereinafter, also simply referred to as “encapsulant sheet”) is a film-like or sheet-like encapsulant composition obtained by molding a encapsulant composition described in detail below by a conventionally known method. It was. The sheet shape in the present invention means that the film shape is also included, and there is no difference between the two.

Further, it is preferable to limit the molding temperature of the encapsulant sheet to a low temperature range of 90 ° C to 120 ° C and to mold the encapsulant sheet without cross-linking. The cross-linking treatment can be performed separately after molding, or can be heated to a high temperature at the time of manufacturing the solar cell module described later to complete the cross-linking.

The encapsulant sheet uses a polyethylene resin having a density of 0.900 g / cm ³ or less, preferably 0.890 g / cm ³ or less as a base resin. If the density of polyethylene as the base resin ^{exceeds 0.900 g / cm 3} , it becomes difficult to maintain sufficient transparency of the encapsulant sheet even if the amount of the light-resistant stabilizer added is optimized.

Further, the density of the encapsulant sheet has the above density as the upper limit, while the lower limit thereof is optimized in relation to the density of the hindered amine-based light-resistant stabilizer used as an additive by kneading with the base resin. .. Specifically, the difference between the density of the density of the base resin and a hindered amine light stabilizer is less than 0.050 g / cm ^3, preferably only to be adjusted to less than 0.047 g / cm ^3. In the encapsulant sheet and encapsulant composition of the present invention, it is premised that the density of the hindered amine-based light-resistant stabilizer used is higher than the density of polyethylene as the base resin. The "difference between the density of the base resin and the density of the hindered amine-based light-resistant stabilizer" is, of course, the difference obtained by subtracting the density of the base resin from the density of the hindered amine-based light-resistant stabilizer.

As a representative of the "copolymer type ultra-high molecular weight type HALS" that can be preferably used as a light-resistant stabilizer in the present invention, "XJ-100H" having a ^{density of 0.931 g / cm 3 (molecular weight: 35000,} (Made by Japan Polyethylene Corporation). When using this HALS as light stabilizer, the density of the base resin of the encapsulant sheet may be Dere if exceeded 0.881g / cm ^3, preferably exceeds 0.884 g / cm ³ ..

Further, this encapsulant sheet is formed of an uncrosslinked resin film having a gel fraction of 0% or more and 10% or less, more preferably 0%, in the stage after film formation and before modularization.

However, this uncrosslinked encapsulant sheet contains a predetermined amount of a cross-linking agent, and it is assumed that cross-linking will proceed during any process until after integration as a solar cell module. This is a so-called thermosetting (or cross-linking) resin film. The gel fraction of the encapsulant sheet after the completion of crosslinking in the finished product stage of the final product solar cell module is preferably 50% or more and 90% or less, and more preferably 60% or more and 80% or less. By adjusting the composition and the amount of the cross-linking agent, the cross-linking aid, and other additives to a preferable range as described above, the cross-linking reaction can be appropriately suppressed so that the gel fraction is within the above range. As a result, it has a water vapor barrier of olefin, has flexibility in a low temperature region more than EVA, and can obtain heat resistance at a high temperature, and is olefin-based but has moldability in a low temperature region. Can also be an excellent encapsulant sheet.

Here, the "gel fraction (%)" in the present specification means that 1.0 g of a sealing material sheet is placed in a resin mesh, extracted with xylene at 110 ° C. for 12 hours, and then taken out together with the resin mesh and weighed after drying. Then, the mass before and after extraction was compared, the mass% of the residual insoluble content was measured, and this was used as the gel fraction. The gel fraction of 0% means that the residual insoluble matter is substantially 0 and the crosslinking reaction of the encapsulant composition or the encapsulant sheet has not substantially started. More specifically, "gel fraction 0%" means that the residual insoluble matter is not present at all, and the mass% of the residual insoluble matter measured by a precision balance is less than 0.05% by mass. Suppose to say. The residual insoluble matter does not include pigment components other than the resin component. When a mixture other than these resin components is mixed in the residual insoluble matter by the above test, for example, by separately measuring the content of these mixture in the resin component in advance, these It is possible to calculate the gel fraction that should be originally obtained for the residual insoluble matter derived from the resin component excluding the mixture.

The melt mass flow rate (MFR) of the encapsulant sheet at the stage of uncrosslinking after film formation is MFR measured by JIS-K6922-2 at 190 ° C. and a load of 2.16 kg (hereinafter, this measurement condition in the present specification). The measured value according to MFR is preferably 5 g / 10 minutes or more and 25 g / 10 minutes or less, and more preferably 10 g / 10 minutes or more and 20 g / 10 minutes or less. When the MFR is within the above range, it is possible to obtain a sealing material sheet having excellent adhesion to other members of the solar cell module made of glass, metal or the like. Regarding the MFR when the encapsulant sheet is a multilayer film as described below, the measurement is performed by the above treatment while all the layers are integrally laminated, and the obtained measured value is used as the multilayer. It shall be the MFR value of the encapsulant sheet of.

The encapsulant sheet of the present invention may be a single-layer film, but may be a multilayer film composed of a core layer and skin layers arranged on both sides of the core layer. The multilayer film in the present specification is a film or sheet having a structure having at least one outermost layer, preferably a skin layer formed into both outermost layers, and a core layer which is a layer other than the skin layer. Say that.

When the encapsulant sheet is a multilayer film, it is more preferable to have a layer structure in which the MFR is different for each layer within the range satisfying the essential constituent requirements of the present invention. In this case, the layer having a higher MFR is used. It is preferable to arrange it on the outermost layer side as the skin layer. Although the encapsulant sheet of the present invention has sufficiently preferable transparency, heat resistance, and moderate flexibility even when it is a single-layer encapsulant sheet, it is thus relatively MFR. By arranging the layer having a high content in the outermost layer, it is possible to further improve the adhesion and the molding characteristics while maintaining the above-mentioned preferable transparency and heat resistance as the encapsulant sheet.

For example, in a sealing material sheet which is a multilayer film composed of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and the intermediate layer and the outermost layer composed of all layers other than the outermost layer are formed. The thickness ratio of the outermost layer: the middle layer: the outermost layer is preferably in the range of 1: 3: 1 to 1: 8: 1. By doing so, it is possible to provide preferable molding characteristics in the outermost layer while maintaining preferable heat resistance as a sealing material sheet.

<Encapsulant composition>
The encapsulant composition used for producing the encapsulant sheet of the present invention (hereinafter, also simply referred to as “encapsulant composition”) uses a low-density polyethylene-based resin as a base resin and requires a cross-linking agent. It is a curable resin composition. In the present specification, the term "base resin" is used as a resin composition containing the base resin, which is mixed with the resin having the largest content ratio among the resin components of the resin composition and the resin. It shall refer to the same type of resin used. When polyethylene-based resins having different densities are used as mixed resins as illustrated later in Examples, the entire mixed resin is referred to as a base resin. However, in the present specification, the ethylene chain copolymerized with the cyclic compound in the "copolymer type ultrahigh molecular weight type HALS" constitutes a part of the resin component of the encapsulant composition, but this Is not considered to be part of the base resin.

[Base resin]
The encapsulant composition has a density of 0.900 g / cm ³ or less, preferably 0.890 g / cm ³ or less, and as described above, the density difference from the light-resistant stabilizer to be added is within a predetermined range. Polyethylene in the density range is used as the base resin. By using polyethylene, which has a low density as described above and has a small density difference with the light-resistant stabilizer, as the base resin, it has a high degree of weather resistance while maintaining the original transparency derived from the base resin. Can be prepared for.

As described above, the lower limit of the preferable density range of the base resin of the encapsulant composition is correlatedly determined according to the density difference between the base resin and the light-resistant stabilizer used by kneading. Specific examples of such preferred combinations, for example, a "co-polymer type ultrahigh molecular weight type of HALS" of the above-mentioned density 0.931 g / cm ^3, exceeds the density 0.881g / cm ³ 0.900g / cm ³ or less, preferably, there can be mentioned a combination of 0.884 g / cm ³ greater than 0.890 g / cm ³ low-density polyethylene or less.

By adjusting the density of the base resin within the above range, the adhesion to other members constituting the solar cell module such as the glass protective substrate is enhanced, and the risk of cell cracking during crimping of each member in the laminating process is increased. Can also be reduced.

The polyethylene used as the base resin of the encapsulant composition is linear low density polyethylene (LLDPE) which is a copolymer of ethylene and α-olefin. Further, the base resin is more preferably metallocene-based linear low-density polyethylene (M-LLDPE). The metallocene-based linear low-density polyethylene is synthesized by using a metallocene catalyst which is a single-site catalyst. Such polyethylene has few side chain branches and a uniform distribution of comonomer. Therefore, the molecular weight distribution is narrow, the density can be made ultra-low as described above, and flexibility can be imparted to the encapsulant sheet. As a result of imparting flexibility to the encapsulant sheet, the adhesion between the encapsulant sheet and glass, metal, etc. is enhanced.

Further, since the linear low-density polyethylene has a narrow crystallinity distribution and the same crystal size, not only does it not exist with a large crystal size, but also the crystallinity itself is low due to its low density. Therefore, it is excellent in transparency when processed into a sheet as a sealing material sheet. Therefore, when the encapsulant sheet made of the encapsulant composition using this as a base resin is arranged on the light receiving surface side of the solar cell element in the solar cell module, the incident light on the solar cell element is attenuated. It is possible to prevent a decrease in power generation efficiency.

The "polyethylene resin" in the present specification is not only ordinary polyethylene obtained by polymerizing ethylene, but also a resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin. , Resin obtained by copolymerizing a plurality of different compounds having an ethylenically unsaturated bond, and a modified resin obtained by grafting another chemical species on these resins.

Among them, "a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer" can be preferably used as a part of the base resin of the encapsulant composition. By using such a resin, it is possible to obtain sufficient strength of adhesiveness between another laminated member such as a glass protective substrate or a solar cell element and a sealing material sheet.

The silane copolymer is described in, for example, Japanese Patent Application Laid-Open No. 2003-46105. By using the copolymer as a component of the encapsulant composition of the solar cell module, it is excellent in strength, durability, etc., and also has weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, and hail resistance. It has excellent other characteristics, and has extremely excellent heat fusion properties without being affected by manufacturing conditions such as heat crimping for manufacturing solar cell modules, and is stable, low cost, and suitable for various applications. Suitable solar cell modules can be manufactured.

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

Specifically, for example, one or more kinds of α-olefins, one or more kinds of ethylenically unsaturated silane compounds, and one or more kinds of other unsaturated monomers if necessary. the door, using the desired reaction vessels, for example, a pressure 500~4000Kg / cm ^2-position, preferably, 1000~4000Kg / cm ^2-position, a temperature 100 to 400 ° C.-position, preferably, 150 to 350 ° C.-position conditions Underneath, in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, random copolymerization is carried out simultaneously or stepwise, and if necessary, a random copolymer produced by the copolymerization is formed. A copolymer of α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof can be produced by modifying or condensing a portion of the silane compound.

Further, as the copolymer of α-olefin and ethylenically unsaturated silane compound or its modification or condensate, for example, one or more kinds of α-olefin and, if necessary, other unsaturated monomers. One or more of them may be polymerized simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, using the desired reaction vessel, and then the polymerization thereof. One or more of the ethylenically unsaturated silane compounds are graft-copolymerized with the polyolefin-based polymer produced by the above, and if necessary, a graft copolymer produced by the copolymer is formed. A copolymer of α-olefin and ethylenically unsaturated silane compound or a modified or condensed product thereof can be produced by modifying or condensing a portion of the silane compound.

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

Examples of the ethylenically unsaturated silane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyroxysilane, vinyltriphenoxysilane, and vinyltri. One or more selected from benzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be used.

As the other unsaturated monomer, for example, one or more selected from vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, and vinyl alcohol can be used.

Examples of the radical polymerization initiator that promotes the above-mentioned polymerization and copolymerization include lauroyl peroxide, dipropionyl peroxide, benzoyl peroxide, di-t-butyl peroxide, t-butyl hydroperoxide, and t-butyl peroxide. Organic peroxides such as oxyisobutyrate, molecular oxygen, azo compounds such as azobisisobutyronitrile and azoisobutylvaleronitrile can be used.

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

Examples of the method of modifying or condensing the portion of the silane compound constituting the random copolymer or the method of modifying or condensing the portion of the silane compound constituting the graft copolymer include tin, zinc, iron and lead. Using metal carboxylates such as cobalt, organic metal compounds such as titanium acid esters and chelated products, organic bases, inorganic acids, and silanol condensation catalysts such as organic acids, α-olefins and ethylenically unsaturated silanes are used. Modification or modification of the copolymer of α-olefin and ethylenically unsaturated silane compound by performing dehydration condensation reaction between silanols of the silane compound constituting the random copolymer or graft copolymer with the compound. Examples thereof include a method for producing a condensate.

As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used, but a graft copolymer is more preferable. A graft copolymer obtained by polymerizing polyethylene for polymerization as a main chain and an ethylenically unsaturated silane compound as a side chain is further preferable. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to adhesive strength, it is possible to improve the adhesiveness of the encapsulant sheet for the solar cell module to other members in the solar cell module. can.

The content of the ethylenically unsaturated silane compound when constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is, for example, about 0.001 to 15% by mass with respect to the total copolymer mass. , Preferably about 0.01 to 5% by mass, and particularly preferably about 0.05 to 2% by mass.

[Crosslinking agent]
As the cross-linking agent used in the encapsulant composition, the amount of active oxygen is preferably 8.5% or more and 15.00% or less, preferably 8.5% or more and 10.00% or less. By using a cross-linking agent having an active oxygen amount in the above range, the sealing material sheet can be provided with excellent heat resistance, light resistance, and transparency.

The 1-hour half-life temperature of the cross-linking agent used in the encapsulant composition is preferably 125 ° C. or higher and 145 ° C. or lower. Thereby, the encapsulant composition of the present invention can be made into a composition capable of melt extrusion molding at 120 ° C. or lower.

Specific examples of preferable cross-linking agents satisfying the above conditions include n-butyl 4,4-di (t-butylperoxy) valerate, ethyl 3,3-di (t-butylperoxy) butyrate, and 2,2-. Peroxyketals such as di (t-butylperoxy) butane, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-) Dialkyl peroxides such as butylperoxy) hexane and 2,5-dimethyl-2,5-di (t-peroxy) hexin-3 can be preferably used as a cross-linking agent to be added to the encapsulant composition.

The content of the above-mentioned cross-linking agent in the encapsulant composition is preferably 0.2% by mass or more and 0.5% by mass or less with respect to the base resin in the encapsulant composition, and more preferably 0. It is in the range of 3% by mass or more and 0.4% by mass or less. By adding a cross-linking agent in this range, sufficient durability can be imparted to the encapsulant sheet. The encapsulant sheet of the present invention is formed without substantially progressing crosslinking, and the content of the above-mentioned crosslinking agent in the encapsulant sheet at the sheet stage after film formation is also 0. It is assumed that the range is 2% by mass or more and 0.5% by mass or less.

[Crosslinking aid]
In the encapsulant composition, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group, more preferably the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. It is preferable to contain an agent. This promotes an appropriate cross-linking reaction to improve the adhesion of the encapsulant sheet to glass and metal, and in addition, this cross-linking aid is the crystallinity of the linear low density polyethylene forming the encapsulant sheet. And maintain transparency. As a result, in addition to the above-mentioned effect of improving the adhesiveness, the transparency and low-temperature flexibility of the encapsulant sheet can be further improved.

Specific examples of the cross-linking aid that can be used in the encapsulant composition include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate, and tri. Methylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonane Poly (meth) acryloxy compounds such as diol diacrylates, glycidyl methacrylates containing double bonds and epoxy groups, 4-hydroxybutyl acrylate glycidyl ethers and 1,6-hexanediol diglycidyl ethers containing two or more epoxy groups, 1 , 4-Butandiol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, trimethylolpropane polyglycidyl ether and other epoxy compounds can be mentioned. These may be used alone or in combination of two or more. In addition, among the above-mentioned cross-linking aids, it contributes remarkably to the improvement of glass adhesion of the encapsulant sheet, has good compatibility with linear low-density polyethylene, and reduces crystallinity by cross-linking to maintain transparency. TAIC can be preferably used from the viewpoint of imparting flexibility at low temperatures.

The content of the cross-linking aid in the encapsulant composition is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass, based on the base resin in the encapsulant composition. % Or more and 2.0% by mass or less. Within this range, an appropriate crosslinking reaction can be promoted and the adhesion of the encapsulant sheet can be improved.

[Hinderdamine-based light-resistant stabilizer (HALS)]
The encapsulant composition of the present invention is a copolymer of a cyclic aminovinyl compound and ethylene, having a molecular weight of 30,000 or more and a density of 0.930 g / cm ³ or more and 0.940 g / cm ³ or less, preferably 0. containing 930 g / cm ³ or more 0.932 g / cm ³ or less is light stabilizer ( "co-polymer type ultrahigh molecular weight type of HALS").

This "copolymer type ultra-high molecular weight type HALS" is an ultra-high molecular weight type light-resistant stabilizer having a molecular weight of more than 30,000, but is particularly excellent in compatibility with a polyethylene resin. Although this itself was known, the encapsulant composition of the present invention further uniquely blends the encapsulant composition so that the density difference between the HALS and the base resin is within a certain range. It is optimized based on the knowledge.

More specifically, this "copolymer type ultrahigh molecular weight type HALS" is a light-resistant stabilizer which is a copolymer of ethylene and a cyclic aminovinyl compound represented by the following general formula (1). As an example of a light-resistant stabilizer that meets these requirements and is available on the market, for example, "XJ-100H" (molecular weight: 35000, density 0.931 g / cm ³ , manufactured by Japan Polyethylene Corporation) can be mentioned. ..

（１）
（式（１）中、Ｒ１及びＲ２は水素原子又はメチル基を示し、Ｒ３は水素原子又は炭素数１〜４のアルキル基を示す。）

(1)
(In the formula (1), R1 and R2 represent a hydrogen atom or a methyl group, and R3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

When the above-mentioned "copolymer type ultra-high mass type HALS" is used as the light-resistant stabilizer to be added to the encapsulant composition, the amount of the light-resistant stabilizer added is the above-mentioned relative to the base fat formation of the encapsulant composition. The content ratio of the cyclic aminovinyl compound may be 0.1% by mass or more and 0.2% by mass or less, preferably 0.13% by mass or more and 0.20% by mass or less. By setting the addition amount of the "copolymer type ultra-high molecular weight type HALS" to the upper limit of the above range or more, the effect of stabilizing the light resistance can be sufficiently obtained. Further, by setting the content to the upper limit of the above range or less, bleed-out and the resulting decrease in transparency can be sufficiently suppressed. In this specification, the "cyclic aminovinyl compound" in HALS is referred to as the "HALS component" of the HALS.

[Other additives]
The encapsulant composition may further contain other components. For example, an ultraviolet absorber, a heat stabilizer, an adhesion improver, a nucleating agent, a dispersant, a leveling agent, a plasticizer, a defoaming agent, a flame retardant, and various other fillers can be appropriately added. The content ratio of these additives varies depending on the particle shape, density, etc., but is preferably in the range of 0.001% by mass or more and 60% by mass or less in the encapsulant composition. By including these additives, it is possible to impart stable mechanical strength over a long period of time and an effect of preventing yellowing, cracking, etc. to the encapsulant composition.

<Manufacturing method of encapsulant sheet>
The method for producing a sealing material sheet of the present invention is a manufacturing method using the sealing material composition of the present invention described in detail above, and is a light-resistant stabilizer selection step, a base resin selection step, and a material kneading step. , A sheet-making process, and a process including the above.

[Light resistant stabilizer selection process]
In the light-resistant stabilizer selection step, "copolymer type ultra-high molecular weight type HALS" is selected as the light-resistant stabilizer to be added to the polyethylene-based resin used as the base resin in the encapsulant composition. The criteria for selecting a light-resistant stabilizer are that the light-resistant stabilizer is a copolymer of a cyclic aminovinyl compound and ethylene, has a molecular weight of 30,000 or more, and has a density of 0.930 g / cm ³ or more. It is a thing. As a specific example of such a light-resistant stabilizer, as described above, "XJ-100H" (molecular weight: 35,000, density 0.931 g / cm ³ , manufactured by Japan Polyethylene Corporation) can be mentioned.

[Base resin selection process]
In the base resin selection process, a polyethylene-based resin to be used as the base resin is selected in the encapsulant composition. The criteria for selecting the base resin is that the base resin is ^{low-density polyethylene with a density of 0.900 g / cm 3} or less, preferably 0.890 g / cm ³ or less, and the hindered amine-based light-resistant stable selected in the previous step. The density difference from the agent is ^{less than 0.050 g / cm 3} , preferably less than 0.047 g / cm ³ .

[Material kneading process]
In the material kneading step, a cross-linking agent and a hindered amine-based light-resistant stabilizer selected in the previous step are added to the base resin selected in the previous step and kneaded to produce a sealing material composition.

[Sheet-making process]
In the sheet making step, the encapsulant composition produced in the previous step is melt-molded to produce an encapsulant sheet. The melt molding of the encapsulant composition can be performed by a known molding method, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotary molding. The lower limit of the molding temperature at the time of molding may be a temperature exceeding the melting point of the encapsulant composition. The upper limit of the molding temperature is the temperature at which cross-linking 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 cross-linking agent used. good.

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. In the solar cell module 1 of the present invention, a transparent front substrate 2, a front encapsulant 3, a solar cell element 4, a back encapsulant 5, and a back surface protective sheet 6 are laminated in this order from the light receiving surface side of incident light. .. In the solar cell module 1 of the present invention, the encapsulant sheet of the present invention can be used as the front encapsulant 3 and / or the back encapsulant 5. In particular, by arranging the encapsulant sheet of the present invention having excellent transparency as the front encapsulant 3 arranged on the light receiving surface side of the solar cell element 4, not only the design is improved but also the power generation efficiency is improved. Can also contribute.

In the solar cell module 1, for example, the members including the transparent front substrate 2, the front encapsulant 3, the solar cell element 4, the back encapsulant 5, and the back surface protective sheet 6 are sequentially laminated and then vacuum suctioned or the like. After being integrated, it can be manufactured by heat-pressing molding the above-mentioned member as an integrally molded body by a molding method such as a lamination method. At this time, the front sealing material 3 made of a single-layer sheet and the glass substrate are laminated, or the adhesion strengthening layer of the front sealing material 3 made of a multilayer sheet is an example of the transparent front substrate 2. By laminating so as to face the glass substrate, the adhesion between the glass substrate and the encapsulant sheet can be improved. The above heat crimping is carried out at 110 ° C. or higher, and if the curing step is carried out after the heat crimping, the cross-linking reaction of polyethylene further proceeds. The curing step is performed under heating conditions such that the resin temperature of the encapsulant sheet is 140 ° C. or higher and 170 ° C. or lower. As a result, the cross-linking of the encapsulant sheet can be appropriately advanced, and the heat resistance and light resistance of the solar cell module can be sufficiently enhanced.

The solar cell module of the present invention thus obtained has excellent heat resistance and light resistance, and is highly advanced for a long period of time even when exposed to harsh environments such as strong ultraviolet rays, heat rays, wind and rain, etc. It is possible to maintain the weather resistance of. Further, the excellent transparency can contribute to the improvement of the design and the power generation efficiency of the solar cell module.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[Manufacturing of encapsulant sheet]
The encapsulant composition composed of the following materials was melted to produce encapsulant sheets of Examples and Comparative Examples. This encapsulant sheet was produced by a conventional T-die method so as to have a thickness of 460 μm, thereby forming an uncrosslinked single-layer encapsulant sheet. The film formation temperature was 90 ° C to 100 ° C.

(Base resin 1)
: 85 parts by mass of metallocene-based linear low-density polyethylene (M-LLDPE) with a density of 0.885 g / cm ³ and an MFR of 20 g / 10 at 190 ° C., and the following silane-modified transparent resin (density 0.884 g /). cm ³ ) The mixed resin with 15 parts by mass was designated as "base resin 1". The density of the base resin 1 is 0.885 g / cm ³ . In Example 1 and Comparative Examples 1 and 2, this "base resin 1" was used as the base resin.
(Base resin 2)
: A mixed resin of 85 parts by mass of metallocene linear low density polyethylene (M-LLDPE) with a density of 0.879 g / cm ³ and an MFR of 20 g / 10 minutes at 190 ° C. and 15 parts by mass of the following silane-modified transparent resin. Was designated as "base resin 2". The density of the base resin 2 is 0.880 g / cm ³ . In Comparative Examples 3, 4 and 5, this "base resin 2" was used as the base resin.
(Base resin 3)
: A mixed resin of 85 parts by mass of metallocene linear low density polyethylene (M-LLDPE) with a density of 0.915 g / cm ³ and an MFR of 20 g / 10 minutes at 190 ° C. and 15 parts by mass of the following silane-modified transparent resin. Was designated as "base resin 3". The density of the base resin 3 is 0.910 g / cm ³ . In Comparative Example 6, this "base resin 3" was used as the base resin.
(Silane-modified transparent resin)
: 2 parts by mass of vinyltrimethoxysilane with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ^{3 and an MFR of 2 g / 10 minutes at 190 ° C.} And 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed, melted at 200 ° C., and kneaded to obtain a silane-modified transparent resin. The density of this silane-modified transparent resin is 0.884 g / cm ³ , and the MFR at 190 ° C. is 18 g / 10 minutes. Further, this resin is a resin corresponding to a resin containing "a silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer".

(Hinderdamine-based light-resistant stabilizer 1 (HALS))
: "XJ100H (manufactured by Japan Polyethylene Corporation)", molecular weight 35000, density 0.931 g / cm ³ . This HALS is a copolymer of a cyclic aminovinyl compound represented by the above general formula (1) and ethylene, and the content of the cyclic aminovinyl compound is 5.1% by weight (0.7 mol%). .. Further, this HALS is a HALS corresponding to the above-mentioned "copolymer type ultra-high molecular weight type HALS". This hindered amine-based light-resistant stabilizer (HALS) was mixed with each of the above base resins and used. The amount of HALS added was adjusted so that the content (% by mass) of the "HALS component (" cyclic aminovinyl compound ")" with respect to the base resin in each encapsulant composition was the value shown in Table 1.

(Crosslinking agent)
"Luperox 101 (manufactured by Alchema Yoshitomi Co., Ltd.)", dialkyl peroxides butyl peroxide, molecular weight 290.4, active oxygen amount 9.92 or more, 1 hour half-life temperature 140 ° C. The amount of this cross-linking agent added was adjusted so that the content (% by mass) of the encapsulant composition with respect to the base resin was 0.4% by mass.

[Manufacturing of sample for evaluation of encapsulant sheet]
In order to evaluate the physical properties of each encapsulant sheet in a state of being integrated as a solar cell module, each of the uncrosslinked encapsulant sheets of Examples and Comparative Examples manufactured as described above is sandwiched between ETFE films. , The sample obtained by cross-linking treatment by vacuum heating lamination and subsequent curing treatment was used as a sample for evaluating the encapsulant sheet of Examples and Comparative Examples. The vacuum heating laminating conditions and curing conditions were as follows.
(Vacuum heating laminating conditions) (a) Evacuation: 4.0 minutes
(B) Pressurization: (0 kPa to 50 kPa): 10 seconds
(C) Pressure retention: (50 kPa): 6 minutes
(D) Temperature: 110 ° C.
(Cure conditions) (a) Time 40 minutes, temperature 150 ° C.

[Evaluation example 1: Transparency]
Transparency (HAZE) (measured by JIS K7136, Murakami Color Research Institute Co., Ltd., haze / transmittance system HM150) was measured for each of the above-mentioned encapsulant sheet evaluation samples. The results are shown in Table 2 as "transparency". The evaluation criteria are as follows.
(Evaluation criteria)
A: Haze 3.6% or less B: Haze 3.6% or more and 4.5% or less C: Haze 4.5% or less

[Evaluation example 2: High weather resistance]
Each of the above-mentioned encapsulant sheet evaluation samples was tested for high weather resistance. Each encapsulant sheet evaluation sample is brought into close contact with a glass substrate (white plate semi-tempered glass (JPT 3.2 75 mm × 50 mm × 3.2 mm)) and vacuum-heated laminated under the following vacuum heating laminating conditions and curing conditions. After the treatment, samples for adhesion test were prepared for each of the examples and comparative examples. Then, for each of these samples, the initial adhesion and the adhesion after the weather resistance promotion test (“high-intensity xenon irradiation test”) were measured by the following test method, and the adhesion maintenance rate was measured from the ratio of the two. Was calculated and the high weather resistance of each encapsulant sheet was evaluated.
(Vacuum heating laminating conditions) (a) Evacuation: 4.0 minutes
(B) Pressurization: (0 kPa to 50 kPa): 10 seconds
(C) Pressure retention: (50 kPa): 6 minutes
(D) Temperature: 110 ° C.
(Cure conditions) (a) Time 40 minutes, temperature 150 ° C.
(Peeling test method)
: The sealing material sheet that is in close contact with the glass substrate is cut to a width of 15 mm, and a vertical peeling (50 mm / min) test is performed with a peeling tester (Tencilon universal testing machine RTF-1150-H) to perform a sealing material. The adhesion of the sheet was measured.
(High-intensity xenon irradiation test)
: An irradiation test was conducted for 2000 hours using an Atlas weatherometer Ci4000 under the conditions of an irradiance of 60 W / m ² , a black panel temperature (BPT) of 110 ° C., and a humidity of 50%.
A high-intensity xenon irradiation test was carried out under the above conditions, and after 2000 hours, an adhesion test was carried out by the above-mentioned "peeling test method". The ratio (%) of this adhesion to the initial adhesion was used as an index of "high weather resistance (adhesion maintenance rate)" and evaluated according to the following evaluation criteria. The results are as shown in Table 2.
(Evaluation criteria)
A: Adhesion maintenance rate after the above "high-strength xenon irradiation test" for the initial adhesion is 50% or more B: Same adhesion maintenance rate is 25% or more and less than 50% C: Same adhesion maintenance Rate is less than 25%

From Tables 1 and 2, it can be seen that the encapsulant sheet of the present invention is a encapsulant sheet for a solar cell module which uses polyethylene as a base resin, has excellent transparency, and has extremely high weather resistance. ..

1 Solar cell module 2 Transparent front substrate 3 Front encapsulant 4 Solar cell element 5 Back encapsulant 6 Backside protective sheet

Claims (6)

A sealing material composition for a solar cell module containing low-density polyethylene as a base resin, a cross-linking agent, and a hindered amine-based light-resistant stabilizer.
The hindered amine light stabilizer is a copolymer of a cyclic amino vinyl compound and ethylene, the molecular weight is 30000 or more 35000 or less, a density of less than 0.930 g / cm ³ or more 0.950 g / cm ^3,
The content ratio of the cyclic aminovinyl compound to the base resin is 0.1% by mass or more and 0.2% by mass or less.
The density of the base resin is 0.900 g / cm ³ or less, and the difference between the density of the base resin and the density of the hindered amine-based light-resistant stabilizer is less than ^{0.050 g / cm 3.} Material composition. The encapsulant composition according to claim 1, wherein the content of the cross-linking agent with respect to the base resin is 0.2% by mass or more and 0.5% by mass or less. It is a method of manufacturing a sealing material sheet for a solar cell module.
Light-resistant stabilizer selection process and
Base resin selection process and
Material kneading process and
Including the sheeting process,
Wherein in the light stabilizer selected step, as light stabilizer, a copolymer of cyclic amino vinyl compound and ethylene, a molecular weight of 30,000 or more 35,000, density 0.930 g / cm ³ or more 0.950 g / cm less than ³ Select a hindered amine-based light-resistant stabilizer,
In the base resin selection step, the base resin is a low-density polyethylene ^{having a density of 0.900 g / cm 3} or less and a density difference from the hindered amine-based light-resistant stabilizer of ^{less than 0.050 g / cm 3.} Select,
In the material kneading step, a cross-linking agent and the hindered amine-based light-resistant stabilizer are added to the low-density polyethylene and kneaded to produce a sealing material composition.
In the sheet forming step, a method for producing a sealing material sheet, wherein the sealing material composition is melt-molded to produce a sealing material sheet. The third aspect of claim 3, wherein the addition amount of the hindered amine-based light-resistant stabilizer is such that the content ratio of the cyclic aminovinyl compound to the base resin is 0.1% by mass or more and 0.2% by mass or less. Manufacturing method of encapsulant sheet. The low density polyethylene has a density of 0.885 g / cm ³ or more, and has a density of 0.885 g / cm 3 or more.
The method for producing a sealing material sheet according to claim 3 or 4, wherein the hindered amine-based light-resistant stabilizer has a density of 0.930 g / cm ^{3 or more.} The content of the cross-linking agent with respect to the base resin is 0.2% by mass or more and 0.5% by mass or less. The method for manufacturing a sealing material sheet according to any one of claims 3 to 5.

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