WO2019065457A1

WO2019065457A1 - Sealant composition for solar cell module and production method for sealant sheet for solar cell module

Info

Publication number: WO2019065457A1
Application number: PCT/JP2018/034837
Authority: WO
Inventors: 康佑佐伯; 伸也米田; 滋弘上野; 徳俊赤澤
Original assignee: 大日本印刷株式会社
Priority date: 2017-09-28
Filing date: 2018-09-20
Publication date: 2019-04-04
Also published as: JP6972849B2; JP2019062151A

Abstract

Provided is a sealant sheet which is for a solar cell module and which can sufficiently benefit from an excellent weather resistance improvement effect provided by addition of a "copolymer-type ultra-high molecular weight HALS" while maintaining sufficient transparency. This sealant composition for a solar cell module contains a low-density polyethylene as a base resin, a crosslinking agent, and a hindered amine light-resistant stabilizer, wherein the hindered amine light-resistant stabilizer is a copolymer between a cyclic aminovinyl compound and ethylene, and has a molecular weight of 30,000 or more and a density of 0.930 g/cm3 or more, the content ratio of the cyclic aminovinyl compound to the base resin is 0.1-0.2 mass%, the base resin has a density of 0.900 g/cm3 or less, and the difference in density between the base resin and the hindered amine light-resistant stabilizer is less than 0.050 g/cm3.

Description

Sealant composition for solar cell module and method of manufacturing sealer sheet for solar cell module

The present invention relates to a sealant composition for a solar cell module and a method for producing a sealant sheet for a solar cell module.

BACKGROUND OF THE INVENTION In recent years, solar cells as clean energy sources have attracted attention due to rising awareness of environmental issues. Currently, solar cell modules of various forms have been developed and proposed. In general, a solar cell module has a configuration in which a transparent front substrate, a solar cell element and a back surface protection sheet are laminated via a sealing material sheet for a solar cell module (see FIG. 1).

The sealing material sheet for a solar cell module on the premise of being exposed to strong sunlight for a long period of time outdoors is required to have extremely high light resistance. As an additive for providing this light resistance, a sealing material sheet using a hindered amine light stabilizer (hereinafter also referred to as "HALS") has been proposed. (See Patent Document 1).

Furthermore, while the intrinsic effect of improving the light resistance is exhibited in the hindered amine light stabilizers, on the other hand, in order to avoid the deterioration of the optical properties of the sealing material sheet due to the occurrence of bleed-out due to its excessive administration, the molecular weight is There is disclosed a finding that it is preferable to use a high molecular weight hindered amine light stabilizer with a molecular weight of 1200 or more within a fixed amount range (see Patent Document 2). In the present specification, the term "molecular weight" refers to "number average molecular weight (Mn)" unless otherwise specified.

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

However, in recent years, conventional products such as solar cell modules with higher heat resistance and durability for a longer period, assuming use under a wide range of environmental conditions including deserts and tropical rain forests In this case, extremely high weather resistance which was not supposed is required. In order to meet such requirements, it is conceivable to first further increase the addition amount of the high molecular weight type HALS described above. However, while the general high molecular weight type HALS is difficult to bleed out, the compatibility with the resin has not always been sufficient. In particular, when it is intended to add a large amount of HALS to the base resin in order to impart the above-described high weather resistance to the sealing material sheet, such a problem that the compatibility is insufficient appears. I was supposed to

As a solution to this problem, it has been studied to use HALS (hereinafter also referred to as "copolymer type ultra high molecular weight type HALS") which is a copolymer of a cyclic aminovinyl compound and ethylene (Patent Document 1) 3). 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 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. When a high degree of transparency is required for the sealing material sheet, it is necessary to limit the haze to a sufficiently low level by limiting to a resin having a low density of the base resin. Generally, in this case, the density of polyethylene as a base resin needs to be a low density of 0.900 g / cm ³ or less, more preferably 0.880 / cm ³ .

However, as a result of research conducted by the present inventor, when low density polyethylene of density 0.880 cm ³ with sufficiently low haze is used as the base resin, the above-mentioned “copolymer type super excellent in compatibility with the polyethylene-based resin Even if a high molecular weight type HALS is used, when an amount of a certain amount or more sufficient to meet the above-mentioned high weather resistance requirement is added, the haze of the sealing material sheet is increased, and the above-described low It has been recognized that the base resin of density can not maintain sufficient transparency originally possessed.

Japanese Patent Application Laid-Open No. 2004-214641 JP 2012-9693 A JP, 2010-155915, A

The present invention has been made in view of the above-mentioned circumstances, and while sufficiently maintaining the transparency, fully enjoy the excellent weatherability improvement effect by the addition of "copolymer type ultra high molecular weight type HALS" It is an object of the present invention to provide an encapsulant sheet for a solar cell module capable of

The present inventors have excellent resin compatibility in the production of a sealing material for a solar cell module having a polyethylene-based resin as a base resin, and a hindered amine light stabilizer added to the sealing material composition as a material has excellent resin compatibility. In addition to being specified as “HALS of copolymer type ultra high molecular weight type”, first, the density of the polyethylene resin as the base resin is limited to a specific low density range with a small haze, and addition to this base resin and this By optimizing the formulation of the encapsulant composition so that the difference in density with the “copolymer type ultra-high molecular weight type HALS” falls within a predetermined range, it has excellent transparency and is highly advanced. It has been found that it is possible to produce a sealant sheet having a weather resistance, and the present invention has been completed. More specifically, the present invention provides the following.

(1) A sealing material composition for a solar cell module, comprising a low density polyethylene as a base resin and a crosslinking agent and a hindered amine light stabilizer, wherein the hindered amine light stabilizer is a cyclic aminovinyl compound And a copolymer having a molecular weight of 30,000 or more and a density of 0.930 g / cm ³ or more, and a content ratio of the cyclic aminovinyl compound to the base resin is 0.1% by mass or more. The density of the base resin is 2% by mass or less, and 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 light stabilizer is 0.050 g / cm ³ An encapsulant composition that is less than ³ cm ³ .

(2) The encapsulant composition according to (1), wherein the content of the crosslinking agent is 0.2% by mass or more and 0.5% by mass or less based on all resin components.

(3) A method of manufacturing a sealing material sheet for a solar cell module, comprising: a light resistance stabilizer selection step, a base resin selection step, a material mixing step, and a sheeting step, wherein the light resistance In the stabilizer selection step, a hindered amine light stabilizer which is a copolymer of a cyclic aminovinyl compound and ethylene and has a molecular weight of 30,000 or more and a density of 0.930 g / cm ³ or more is selected as a light stabilizer. In the base resin selection step, the base resin has a density of 0.900 g / cm ³ or less and a density difference with the hindered amine light stabilizer of less than 0.050 g / cm ^3. Polyethylene is selected, and in the material mixing step, a crosslinking agent and the hindered amine light stabilizer are added to the low density polyethylene and mixed. The manufacturing method of the sealing material sheet which manufactures a sealing material composition and manufactures a sealing material sheet by melt-molding the said sealing material composition in the said sheeting process.

(4) The addition amount of the hindered amine light stabilizer is an addition amount such that the content ratio of the cyclic aminovinyl compound to the base resin is 0.1 mass% or more and 0.2 mass% or less, (3) The manufacturing method of the sealing material sheet as described in-.

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

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

According to the present invention, a seal for a solar cell module which can fully enjoy the excellent weatherability improvement effect by the addition of “copolymer type ultra-high molecular weight type HALS” while maintaining sufficient transparency. An adhesive sheet can be manufactured.

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

<Sealing material sheet>
The sealing material sheet (hereinafter, also simply referred to as "sealing material sheet") of the present invention is formed into a film or sheet by molding processing of the sealing material composition, the details of which will be described below, by a conventionally known method. The Incidentally, the sheet-like in the present invention means that the film-like is also included, and there is no difference between the two.

In addition, it is preferable to limit the molding temperature to a low temperature range of 90 ° C. to 120 ° C., and to mold the sealing material sheet without being crosslinked. The crosslinking treatment may be separately performed after molding, or may be heated at a high temperature at the time of manufacturing a solar cell module described later to complete the crosslinking.

The encapsulant sheet has 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. When the density of polyethylene as a base resin exceeds 0.900 g / cm ³ , it becomes difficult to maintain sufficient transparency of the sheet of sealing material even if the addition amount of the light resistant stabilizer is optimized.

The upper limit of the density of the encapsulant sheet is the above-mentioned density, while the lower limit thereof is optimized in correlation with the density of the hindered amine light stabilizer used as an additive by kneading with the base resin. . Specifically, it may be adjusted so that the difference between the density of the base resin and the density of the hindered amine light stabilizer is less than 0.050 g / cm ³ , preferably less than 0.047 g / cm ³ . In the encapsulating material sheet and the encapsulating material composition of the present invention, it is premised that the density of the hindered amine light stabilizer used as the light stabilizer is larger than the density of the polyethylene as the base resin. The “difference between the density of the base resin and the density of the above-mentioned hindered amine light stabilizers” in the specification is, of course, the difference obtained by subtracting the density of the base resin from the density of the hindered amine light stabilizers.

As a representative of “copolymer type ultrahigh molecular weight type HALS” which can be preferably used as a light stabilizer in the present invention, “XJ-100H” (molecular weight: 35,000, density is 0.931 g / cm ³ Nippon Polyethylene Co., Ltd. can be mentioned. 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 .

In addition, this sealing material sheet is formed of an uncrosslinked resin film having a gel fraction of 0% or more and 10% or less, more preferably 0%, at a stage after modularization, after film formation.

However, this uncrosslinked sealing material sheet contains a predetermined amount of a crosslinking agent, and it is assumed that crosslinking proceeds during any process until after integration as a solar cell module. It is a so-called thermosetting (or crosslinking) resin film. The gel fraction of the encapsulant sheet after completion of crosslinking in the final product stage of the solar cell module, which is the final product, is preferably 50% to 90%, and more preferably 60% to 80%. As described above, by adjusting the composition and the addition amount of the crosslinking agent, the crosslinking assistant, and the other additives in a preferable range, it is possible to appropriately suppress the crosslinking reaction so that the gel fraction is in the above range. As a result, it is possible to obtain flexibility in a lower temperature range than that of EVA while having an olefin water vapor barrier, and to obtain heat resistance at high temperatures, and to formability in a low temperature range while being olefinic. Can also be an excellent sealant sheet.

Here, “gel fraction (%)” in the present specification refers to 1.0 g of the encapsulant sheet placed in a resin mesh, extracted with 110 ° C. xylene for 12 hours, then taken out together with the resin mesh and weighed after drying processing Then, mass comparison before and after extraction is performed to measure the mass% of the remaining insoluble content, and this is taken as a gel fraction. The gel fraction of 0% means that the residual insoluble content is substantially zero, and the crosslinking reaction of the encapsulant composition or the encapsulant sheet is not substantially initiated. More specifically, “gel fraction 0%” means that the above-mentioned residual insolubles are not present at all, and the above-mentioned residual insolubles measured by a precision balance have a mass% of less than 0.05% by mass. Shall be said. The above-mentioned residual insolubles do not contain pigment components other than resin components. When inclusions other than these resin components are present in the residual insolubles according to the above-mentioned test, for example, the content of these inclusions in the resin component may be separately measured in advance. The gel fraction to be originally obtained can be calculated for the residual insoluble matter derived from the resin component excluding the inclusions.

The melt mass flow rate (MFR) of the encapsulant sheet at the uncrosslinked stage after film formation is MFR at 190 ° C. measured under JIS-K6922-2 and a load of 2.16 kg (in the present specification, this measurement condition is hereinafter referred to as “MFR”) Is referred to as 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 MFR is in the above-mentioned range, a sealing material sheet excellent in adhesion to other members of the solar cell module made of glass, metal or the like can be obtained. In addition, about MFR in case a sealing material sheet is a multilayer film which is demonstrated below, the measurement by the said process is measured in the multilayer state in which all the layers were integrally laminated, and the obtained measured value is said multilayer The MFR value of the sealant sheet of

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

When making a sealing material sheet into a multilayer film, it is more preferable to set it as the layer structure from which MFR differs for every layer in the range which satisfy | fills the essential component requirements of this invention, and in this case, a layer with a higher MFR It is preferable to arrange | position to the outermost layer side as a skin layer. The encapsulant sheet of the present invention, even in the case of a single-layer encapsulant sheet, has sufficiently favorable transparency, heat resistance, and appropriate flexibility, but in such a manner it is relatively MFR. By arranging the high layer as 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 sealing material sheet.

For example, in a sealing material sheet which is a multilayer film consisting of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and an intermediate layer and an outermost layer consisting of all layers other than the outermost layer It is preferable that the thickness ratio of (1) be in the range of outermost layer: intermediate layer: outmost layer = 1: 3: 1 to 1: 8: 1. By so doing, it is possible to provide the preferable molding characteristics in the outermost layer while maintaining the preferable heat resistance as the sealing material sheet.

<Sealing material composition>
The sealing material composition (hereinafter, also simply referred to as "sealing material composition") used for the production of the sealing material sheet of the present invention has a low density polyethylene resin as a base resin and requires a crosslinking agent as heat. It is a resin composition of a curing system. In the present specification, “base resin” refers to a resin composition containing the base resin, which is mixed with the resin having the largest content ratio in the resin component of the resin composition and the resin. It refers to the same kind of resin being used. When polyethylene resins having different densities are used as a mixed resin as will be exemplified later in the examples, the entire mixed resin is referred to as a base resin. However, in the present specification, with regard to the ethylene chain copolymerized with the cyclic compound in “copolymer type ultrahigh molecular weight type HALS”, although a part of the resin component of the encapsulant composition is constituted, Shall not be considered as 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 with the added light stabilizer is within a predetermined range. The base resin is polyethylene in the density range. By using a polyethylene having a low density as described above and a small density difference with the light stabilizer as the base resin, a high weather resistance can be obtained for the sealant sheet while maintaining the original transparency derived from the base resin. Can be prepared for

The lower limit of the preferable density range of the base resin of the encapsulant composition is, as described above, determined correlatively according to the density difference between the base resin and the light resistant stabilizer used after 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 with other members constituting the solar cell module, such as a glass protective substrate, is enhanced, and the risk of cell breakage at the time of pressure bonding of each member in lamination processing Can also be reduced.

The polyethylene used as a base resin of the encapsulant composition is linear low density polyethylene (LLDPE) which is a copolymer of ethylene and an α-olefin. Further, the base resin is more preferably a metallocene linear low density polyethylene (M-LLDPE). The metallocene based linear low density polyethylene is one synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has less side chain branching and uniform comonomer distribution. For this reason, the molecular weight distribution is narrow, and it is possible to make the ultra-low density as described above, and it is possible to impart flexibility to the sealing material sheet. As a result of the flexibility given to the sealing material sheet, the adhesion between the sealing material sheet and the glass, metal or the like is enhanced.

In addition, linear low density polyethylene has a narrow crystallinity distribution and uniform crystal size, and thus not only does not have a large crystal size but also has low crystallinity itself due to its low density. For this reason, it is excellent in the transparency at the time of processing into a sheet form as a sealing agent sheet. Therefore, in the solar cell module, the sealing material sheet comprising the sealing material composition having the base resin as a base resin, when disposed on the light receiving surface side of the solar cell element, is attenuated by the incident light to the solar cell element. It is possible to prevent the decrease of the power generation efficiency well.

In the “polyethylene resin” in the present specification, not only ordinary polyethylene obtained by polymerizing ethylene but also resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin and the like And resins obtained by copolymerizing a plurality of different compounds having an ethylenically unsaturated bond, and modified resins obtained by grafting another chemical species to 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 a base resin of a sealing material composition. By using such a resin, adhesiveness of sufficient strength can be obtained between another laminated member such as a glass protective substrate or a solar cell element and the sealing material sheet.

The silane copolymer is, for example, one described in JP-A 2003-46105. By using the said copolymer as a component of the sealing material composition of a solar cell module, it is excellent in intensity | strength, durability, etc., And, weather resistance, heat resistance, water resistance, light resistance, wind resistance, falling resistance, Excellent in various other properties, moreover, it has extremely excellent heat sealing property without being affected by the manufacturing conditions such as thermocompression bonding for manufacturing a solar cell module, stably, at low cost, 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, another unsaturated monomer as a comonomer, the copolymer And modified products or condensates of

Specifically, for example, one or more of α-olefins, one or more of ethylenically unsaturated silane compounds, and, if necessary, one or more of other unsaturated monomers. And a pressure of about 500 to 4000 kg / cm ² , preferably about 1000 to 4000 kg / cm ² and a temperature of about 100 to 400 ° C., preferably about 150 to 350 ° C., using a desired reaction vessel. Under this, in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, simultaneously or stepwise, random copolymerize, and, if necessary, construct a random copolymer formed by the copolymer. A portion of the silane compound can be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof.

Also, as a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof, for example, one or more of α-olefins and, if necessary, other unsaturated monomers One or more of them are polymerized simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, as described above, using the desired reaction vessel, and then the polymerization thereof Graft copolymerizing one or more kinds of ethylenically unsaturated silane compounds with the polyolefin polymer formed by the above, and, if necessary, constituting a graft copolymer formed by the copolymer A part of the silane compound is modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof. That.

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

As the ethylenically unsaturated silane compound, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltriphenoxysilane, vinyltriphenoxysilane One or more selected from benzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane can be used.

As another unsaturated monomer, 1 or more types selected from vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, vinyl alcohol can be used, for example.

Examples of radical polymerization initiators that promote the above 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, and azo compounds such as azobisisobutyronitrile and azoisobutylvaleronitrile can be used.

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

As a method of modifying or condensing a portion of a silane compound constituting a random copolymer, or a method of modifying or condensing a portion of a silane compound constituting a graft copolymer, for example, tin, zinc, iron, lead, Α-olefins and ethylenically unsaturated silanes using carboxylic acid salts of metals such as cobalt, organic metal compounds such as titanates and chelates, organic bases, inorganic acids, and silanol condensation catalysts such as organic acids Modification of the copolymer of α-olefin and the ethylenically unsaturated silane compound by dehydrating condensation reaction between silanols of the portion of the silane compound constituting the random copolymer or graft copolymer with the compound The method of manufacturing a condensate is mentioned.

As the silane copolymer, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer can be preferably used, but a graft copolymer is more preferable. It is further preferable to use a graft copolymer in which polyethylene for polymerization is used as a main chain and an ethylenically unsaturated silane compound is used as a side chain. Such graft copolymer improves the adhesion of the encapsulant sheet for the solar cell module to other members in the solar cell module because the degree of freedom of the silanol group contributing to the adhesion becomes high. it can.

The content of the ethylenically unsaturated silane compound in forming 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 mass of the copolymer. Preferably, about 0.01 to 5% by mass, more preferably about 0.05 to 2% by mass is desirable.

[Crosslinking agent]
As a crosslinking agent used for a sealing material composition, the amount of active oxygen should just be 8.5% or more and 15.00% or less, and it is preferable that it is 8.5% or more and 10.00% or less. By using a crosslinking agent having an active oxygen content in the above range, the sealing material sheet can be provided with better heat resistance, light resistance, and transparency.

Moreover, it is preferable to use the thing of 125 degreeC or more and 145 degrees C or less about 1 hour half life temperature of the crosslinking agent used for a sealing material composition. Thereby, the sealing agent composition of this invention can be made into the composition which can be melt-extruded at 120 degrees C or less.

Further, specific examples of preferable crosslinking agents satisfying the above conditions include n-butyl 4,4-di (t-butylperoxy) valerate, ethyl 3,3-di (t-butylperoxy) butyrate, 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) hexine-3 can be preferably used as a crosslinking agent to be added to the encapsulant composition.

The content of the above-mentioned crosslinking agent in the sealing material composition is preferably 0.2% by mass or more and 0.5% by mass or less with respect to the base resin in the sealing material composition, and more preferably 0. It is the range of 3 mass% or more and 0.4 mass% or less. By adding the crosslinking agent in this range, it is possible to impart sufficient durability to the sealing material sheet. In addition, the sealing material sheet of this invention is formed into a film, without advancing crosslinking substantially, and content of said crosslinking agent in the sealing material sheet in the sheet | seat stage after film-forming is also 0.1. It is assumed to be in the range of 2% by mass to 0.5% by mass.

[Crosslinking Aid]
In the encapsulant composition, a crosslinking monomer having a carbon-carbon double bond and / or an epoxy group, and more preferably, the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, a vinyl group It is preferable to contain an agent. In addition to promoting an appropriate crosslinking reaction by this and improving the adhesiveness with respect to the glass and metal of a sealing material sheet, this crosslinking adjuvant forms the crystallinity of linear low density polyethylene which forms a sealing material sheet. And maintain transparency. Thereby, in addition to the effect of the improvement of said adhesiveness, transparency and low temperature flexibility of a sealing material sheet can be made more excellent.

Specific examples of the crosslinking aid that can be used for the sealant composition include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate, and trilyl. 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 compound such as diol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycidyl ether, and containing 2 or more epoxy groups That 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and epoxy compounds such as trimethylolpropane polyglycidyl ether. These may be independent or may combine 2 or more types. Further, among the above-mentioned crosslinking assistants, it significantly contributes to the improvement of the glass adhesion of the sealing material sheet, has good compatibility with linear low density polyethylene, reduces crystallinity by crosslinking, and maintains transparency. TAIC can be preferably used from the viewpoint of imparting flexibility at low temperature.

The content of the crosslinking aid in the encapsulant composition is preferably 0.01% by mass or more and 3% by mass or less, and 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, it is possible to promote an appropriate crosslinking reaction and improve the adhesion of the sealing material sheet.

[Hindered amine light stabilizers (HALS)]
The encapsulant composition of the present invention is a copolymer of a cyclic aminovinyl compound and ethylene and has 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 ultrahigh molecular weight type HALS” is a light resistance stabilizer of ultra high molecular weight type having a molecular weight of more than 30,000, and is particularly excellent in compatibility with polyethylene resins. Although this itself was known, the encapsulant composition of the present invention is further unique in blending the encapsulant composition such that the density difference between the HALS and the base resin is within a certain range. It is optimized based on knowledge.

More specifically, the “copolymer type ultrahigh molecular weight type HALS” is a light stabilizer that is a copolymer of a cyclic aminovinyl compound represented by the following general formula (1) and ethylene. As an example of a light stabilizer that meets such requirements and is commercially available, for example, “XJ-100H” (molecular weight: 35000, density is 0.931 g / cm ³ , manufactured by Nippon Polyethylene Co., Ltd.) can be mentioned. .

(1)
(In formula (1), R 1 and R 2 represent a hydrogen atom or a methyl group, and R 3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.)

When the above-mentioned "copolymer type ultra-high molecular weight type HALS" is used as the light stabilizer added to the encapsulant composition, the addition amount of the light stabilizer is the amount described above with respect to the base oil composition of the encapsulant composition. The addition amount may be such that the content ratio of the cyclic aminovinyl compound is 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 “copolymer type ultrahigh molecular weight type HALS” to the above-mentioned lower limit or more, the effect of light resistance stabilization can be sufficiently obtained. Also, by setting the upper limit of the above range or less, it is possible to sufficiently suppress the bleed out and the drop in transparency due to it. In the present specification, the “cyclic aminovinyl compound” in the HALS is referred to as “HALS component” of the HALS.

[Other additives]
The sealant composition can further contain other components. For example, a UV absorber, a heat stabilizer, an adhesion improver, a nucleating agent, a dispersant, a leveling agent, a plasticizer, an antifoamer, a flame retardant, and various other fillers can be appropriately added. Although the content ratio of these additives differs depending on the particle shape, density and the like, it is preferable that the content ratio of each additive is in the range of 0.001% by mass to 60% by mass in the sealing material composition. By containing these additives, the sealing material composition can be provided with stable mechanical strength over a long period of time, an effect of preventing yellowing, cracking and the like.

<Method of manufacturing encapsulant sheet>
The method for producing a sealant sheet of the present invention is a production method using the sealant composition of the present invention, the details of which have been described above, which is a light stabilizer selection step, a base resin selection step, and a material kneading step A sheeting process.

[Light-resistant stabilizer selection process]
In the light stabilizer selection step, “HALS of copolymer type ultrahigh molecular weight type” is selected as the light stabilizer to be added to the polyethylene-based resin as the base resin in the sealant composition. The criteria for selecting a light stabilizer is that the light stabilizer is a copolymer of a cyclic aminovinyl compound and ethylene, and satisfies the requirement that the molecular weight is 30,000 or more and the density is 0.930 g / cm ³ or more. It is a thing. As a specific example of such a light stabilizer, as described above, “XJ-100H” (molecular weight: 35000, density is 0.931 g / cm ³ , manufactured by Japan Polyethylene Corporation) can be mentioned.

[Base resin selection process]
In the base resin selection step, a polyethylene resin to be a base resin in the encapsulant composition is selected. The criteria for selection of the base resin is that the base resin is a low density polyethylene having a density of 0.900 g / cm ³ or less, preferably 0.890 g / cm ³ or less, and the hindered amine light stability selected in the previous step The density difference with the agent is less than 0.050 g / cm ³ , preferably less than 0.047 g / cm ³ .

[Material mixing process]
In the material kneading step, the sealant composition is produced by adding and crosslinking the crosslinking agent and the hindered amine light stabilizer selected in the previous step to the base resin selected in the previous step.

[Sheeting process]
In the sheeting step, the sealing material composition produced in the previous step is melt-molded to produce a sealing material sheet. Melt molding of the sealing material composition can be performed by known molding methods, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, rotational molding and the like. The lower limit of the molding temperature during molding may be a temperature that exceeds the melting point of the sealing material composition. The upper limit of the molding temperature may be a temperature at which crosslinking does not start during film formation, that is, a temperature at which the gel fraction of the encapsulant composition can be maintained at 0% according to the 1 minute half-life temperature of the crosslinking agent used. .

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer configuration of the solar cell module of the present invention. In the solar cell module 1 of the present invention, the transparent front substrate 2, the front sealing material 3, the solar cell element 4, the back sealing material 5, and the back surface protection sheet 6 are sequentially stacked from the light receiving surface side of incident light. . The solar cell module 1 of the present invention can use the sealant sheet of the present invention as the front sealant 3 and / or the back sealant 5. In particular, by arranging the encapsulant sheet of the present invention having excellent transparency as the front encapsulant 3 disposed on the light receiving surface side of the solar cell element 4, not only improvement in designability but also improvement in power generation efficiency Can also contribute.

The solar cell module 1 is formed, for example, by vacuum suction after sequentially laminating the members including the transparent front substrate 2, the front sealing material 3, the solar cell element 4, the back sealing material 5, and the back protection sheet 6. After being integrated, the above-described members can be manufactured as an integral molded body by thermocompression molding by a molding method such as a lamination method. Then, at this time, the front side sealing material 3 made of a single layer sheet and the glass substrate are laminated, or the above-mentioned adhesion strengthening layer of the front side 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 sealing material sheet can be improved. The above-mentioned thermocompression bonding is carried out at 110 ° C. or higher, and when the curing step is carried out after the thermocompression bonding, the crosslinking reaction of polyethylene further proceeds. The curing step is performed under heating conditions such that the resin temperature of the sealing material sheet is 140 ° C. or more and 170 ° C. or less. Thereby, crosslinking of a sealing material sheet can be made to advance moderately and the heat resistance and light resistance of a solar cell module can fully be raised.

The solar cell module of the present invention obtained in this manner is excellent in heat resistance and light resistance, and even when exposed to severe environments such as strong ultraviolet rays, heat rays, wind and rain, etc., it is highly advanced over a long period of time It is possible to maintain the weather resistance of the In addition, the excellent transparency can also contribute to the improvement of the design of the solar cell module and the power generation efficiency.

Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to the following examples.

[Manufacture of encapsulant sheet]
The sealing material composition which consists of the following material was fuse | melted, and the sealing material sheet of the Example and the comparative example was manufactured. In the production of this sealing material sheet, a film was formed to have a thickness of 460 μm by a conventional method T-die method, whereby a non-crosslinked single layer sealing material sheet was formed. The deposition temperature was 90 ° C. to 100 ° C.

(Base resin 1)
85 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.885 g / cm ³ and an MFR of 20 g / 10 min at 190 ° C., and the following silane-modified transparent resin (density 0.884 g / cm ³ ) A mixed resin with 15 parts by mass of cm ³ was used as “base resin 1”. The density of the base resin 1 is 0.885 g / cm ³ . This “base resin 1” was used as a base resin in Example 1 and Comparative Examples 1 and 2.
(Base resin 2)
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 MFR of 20 g / 10 min at 190 ° C. and 15 parts by mass of the following silane-modified transparent resin Of “Base resin 2”. The density of the base resin 2 is 0.880 g / cm ³ . This "base resin 2" was used as a base resin in Comparative Examples 3, 4 and 5.
(Base resin 3)
Mixed resin of 85 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.915 g / cm ³ and MFR of 20 g / 10 min at 190 ° C. and 15 parts by mass of the following silane modified transparent resin Of “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 a base resin.
(Silane modified transparent resin)
: 2 parts by mass of vinyltrimethoxysilane based on 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min The silane modified transparent resin obtained by mixing and 0.1 mass part of dicumyl peroxides as a radical generating agent (reaction catalyst), melt | melting at 200 degreeC, and knead | mixing. The density of this silane modified transparent resin is 0.884 g / cm ³ , and the MFR at 190 ° C. is 18 g / 10 min. In addition, this resin corresponds to a resin containing “a silane copolymer formed by copolymerizing α-olefin and an ethylenically unsaturated silane compound as a comonomer”.

(Hindered amine light stabilizer 1 (HALS))
"XJ100H (manufactured by Japan Polyethylene Corporation)", molecular weight 35,000, 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 = 5.1% by weight (0.7 mol%) . Moreover, this HALS is a HALS corresponding to the above-mentioned "copolymer type ultrahigh molecular weight type HALS". This hindered amine light stabilizer (HALS) was used by mixing with each of the above base resins. The amount of addition of the HALS was adjusted so that the content (% by mass) of the “HALS component (“ cyclic amino vinyl compound ”)” with respect to the base resin in each sealing material composition was the numerical value shown in Table 1.

(Crosslinking agent)
"Luporox 101 (manufactured by Arkema Yoshitomi Co., Ltd.)", dialkyl peroxides butyl peroxide, molecular weight 290.4, active oxygen content 9.92 or more, half-life temperature 140 ° C. for 1 hour. The addition amount of each of the crosslinking agents was adjusted such that the content (% by mass) of the sealing material composition to the base resin was 0.4% by mass.

[Production of Sample for Sealant Sheet Evaluation]
In order to evaluate the physical property of each sealing material sheet in the state integrated as a solar cell module, each uncrosslinked sealing material sheet of the Example manufactured as mentioned above and a comparative example is inserted | pinched by ETFE film The thing which performed the crosslinking process by vacuum heating lamination and subsequent curing treatment was made into the sample for evaluation of the sealing material sheet of an example and a comparative example. 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 holding: (50 kPa): 6 minutes (d) temperature: 110 ° C.
(Cure condition)
(A) time 40 minutes, temperature 150 ° C.

[Evaluation Example 1: Transparency]
The transparency (HAZE) (measured according to JIS K7136, Murakami Color Research Laboratory, haze-transmittance HM150) was measured for each of the above-described samples for sealing material sheet evaluation. The results are shown in Table 2 as "transparency". Evaluation criteria were 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 more

[Evaluation example 2: high weather resistance]
The test concerning high weather resistance was done about each above-mentioned sealing material sheet evaluation sample. Each sealing material sheet evaluation sample is brought into close contact with a glass substrate (white plate semi-tempered glass (JPT 3.275 mm × 50 mm × 3.2 mm)), and vacuum heating laminating is performed under the following vacuum heating laminating conditions and curing conditions. It processed and the sample for the adhesiveness test was created about each Example and comparative example. Then, for each of these samples, the adhesion in the initial stage and the adhesion after the weathering accelerated test ("high-intensity xenon irradiation test") were measured by the following test method, and the ratio of the both maintained the adhesion maintenance rate Were calculated to evaluate the high weather resistance of each sealing material sheet.
(Vacuum heating laminating conditions)
(A) evacuation: 4.0 minutes (b) pressurization: (0 kPa to 50 kPa): 10 seconds (c) pressure holding: (50 kPa): 6 minutes (d) temperature: 110 ° C.
(Cure condition)
(A) time 40 minutes, temperature 150 ° C.
(Peeling test method)
: Cut the sealing material sheet in close contact with the glass substrate to a width of 15 mm, perform vertical peeling (50 mm / min) test with a peeling tester (Tentiron universal tester RTF-1150-H), and cut the sealing material The adhesion of the sheet was measured.
(High intensity xenon irradiation test)
Irradiation test was conducted for 2000 hours under the conditions of an irradiance of 60 W / m ² , a black panel temperature (BPT) of 110 ° C. and a humidity of 50% using an Atlas Weatherometer Ci4000.
A high-intensity xenon irradiation test was conducted under the above conditions, and after 2000 hours, an adhesion test was conducted according to the "peel test method". The ratio (%) of the adhesion to the initial adhesion described above was used as an index of "high weather resistance (adhesion maintenance ratio)" and was evaluated according to the following evaluation criteria. The results are as shown in Table 2.
(Evaluation criteria)
A: The maintenance ratio of adhesion after the above "high intensity xenon irradiation test" to the initial adhesion is 50% or more B: The adhesion maintenance ratio is 25% or more and less than 50% C: The adhesion maintenance 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 having polyethylene as a base resin, excellent in transparency, and having extremely high weather resistance. .

1 solar cell module 2 transparent front substrate 3 front sealing material 4 solar battery element 5 back sealing material 6 back protective sheet

Claims

An encapsulant composition for a solar cell module, comprising a low density polyethylene as a base resin, a crosslinker, and a hindered amine light stabilizer,
The hindered amine light stabilizer is a copolymer of a cyclic aminovinyl compound and ethylene, and has a molecular weight of 30,000 or more and a density of 0.930 g / cm 3 or more,
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 sealing wherein 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 light stabilizer is less than 0.050 g / cm 3 Material composition.
The sealing material composition according to claim 1, wherein a content of the crosslinking agent with respect to the base resin is 0.2% by mass or more and 0.5% by mass or less.
A method of manufacturing an encapsulant sheet for a solar cell module, comprising:
A light stabilizer selection process,
Base resin selection process,
Material mixing process,
And a sheeting process,
In the light stabilizer selection step, a hindered amine light stabilizer, which 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 as a light stabilizer. Select
In the base resin selection step, a low density polyethylene having a density of 0.900 g / cm 3 or less as the base resin and a density difference with the hindered amine light stabilizer of less than 0.050 g / cm 3. Select
In the material kneading step, a sealing agent composition is produced by adding a crosslinking agent and the hindered amine light stabilizer to the low density polyethylene, and kneading.
In the said sheeting process, the manufacturing method of the sealing material sheet which melt-molds the said sealing material composition, and manufactures a sealing material sheet.
The addition amount of the hindered amine light stabilizer is an addition amount 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. Method of manufacturing encapsulant sheet.
The low density polyethylene has a density of 0.885 g / cm 3 or more,
The manufacturing method of the sealing material sheet of Claim 3 or 4 whose density is 0.930 g / cm < 3 > or more as for the said hindered amine light stabilizer.
The content of the crosslinking agent with respect to the base resin is 0.2% by mass or more and 0.5% by mass or less. The manufacturing method of the sealing material sheet in any one of Claims 3-5.