JP6326919B2 - Sealant sheet for solar cell module - Google Patents

Description

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

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. The solar cell module constituting the solar cell includes a solar cell element, and this solar cell element plays a role of converting light energy such as sunlight into electric energy.

  This solar cell module is always exposed to harsh environments such as strong ultraviolet rays, heat rays, and wind and rain for a long period of time. For this reason, a high degree of weather resistance and durability are calculated | required by the solar cell module. Therefore, high adhesion is required between the members constituting the solar cell module.

  As a sealing material sheet filled in the solar cell module and used to protect the solar cell element from external impacts and prevent moisture from entering the solar cell module, ethylene-vinyl acetate copolymer Combined resins (EVA) have been used as the most common. However, in recent years, as a solution to the problem of deterioration of water vapor barrier properties in long-term use, which is a drawback of EVA resin, sealing for solar cell modules using low-density polyethylene resin instead of EVA resin Material sheets have been proposed.

  However, since polyethylene resin does not have a polar group in the main chain like EVA, for example, it has adhesion to a base material that is a constituent member of a solar cell module, such as glass that is a material of a transparent front substrate of a solar cell module. There was a problem of being insufficient.

  Conventionally, a silane coupling agent has been widely used as an adhesion improving component added to the sealing material composition in order to improve the adhesiveness of the sealing material sheet. In recent years, there has also been proposed a sealing material sheet in which the adhesion between a metal or glass constituting each member of a solar cell module is improved by adding a specific silane coupling agent (Patent Document 1). reference).

JP 2012-195561 A

  The addition of the silane coupling agent in the encapsulant sheet described in Patent Document 1 contributes to the improvement of the adhesion of the encapsulant sheet, but on the other hand, a decrease in the adhesion improving function due to so-called bleed out becomes a problem. There is a case. This problem is particularly noticeable when a silane coupling agent is added to a polyethylene resin having poor compatibility with the silane coupling agent. In the encapsulant sheet for solar cell modules based on low-density polyethylene, improvements to further improve cost performance are required for the method of improving adhesion by adding an adhesion-improving component to the base resin. It was.

  This invention is made | formed in view of the above condition, It is a sealing material sheet for solar cell modules which used low density polyethylene as base resin, Comprising: The sealing material sheet which has sufficient adhesiveness is provided. For the purpose.

  The inventors of the present invention have a sufficient amount of low molecular weight compounds obtained by decomposing a part of the polymeric light stabilizer added to maintain the weather resistance in an appropriate amount ratio in the base resin. It discovered that it could be set as the sealing material sheet for solar cell modules which has adhesiveness, and came to complete this invention. More specifically, the present invention provides the following.

(1) A sealing material sheet for a solar cell module, and density 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin, a hindered amine light stabilizer,
A degradation product of the hindered amine light stabilizer, comprising a low molecular compound having a piperidine ring and having a number average molecular weight of 1000 or less, and the content of the low molecular compound is that of the encapsulant sheet The sealing material sheet which is 0.01 mass% or more and 0.07 mass% or less by content ratio with respect to all the resin components.

  (2) The sealing material according to (1), wherein the low molecular compound is a decomposition product of the hindered amine light stabilizer, has a piperidine ethanol structure, and has a number average molecular weight of 1000 or less. Sheet.

  (3) The content of the hindered amine light stabilizer is 0.08% by mass or more and 0.5% by mass or less, and the content of the low molecular compound is 10% or more of the content of the hindered amine light stabilizer. The sealing material sheet according to (1) or (2), which is 75% or less.

  (4) The encapsulant sheet according to any one of (1) to (3), wherein the hindered amine light stabilizer has a number average molecular weight of 2500 or more.

(5) The encapsulant sheet according to any one of (1) to (4), wherein the hindered amine light stabilizer is a compound represented by the following general formula (Formula 1).

  (6) The encapsulant sheet according to any one of (1) to (5), wherein the polyethylene resin is a metallocene linear low-density polyethylene.

  (7) The sealing according to any one of (1) to (6), wherein the polyethylene-based resin contains a silane copolymer obtained by copolymerizing at least an α-olefin and an ethylenically unsaturated silane compound as a comonomer. Stop sheet.

  (8) A solar cell module provided with the sealing material layer which consists of a sealing material sheet for solar cell modules in any one of (1) to (7).

(9) Density of 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin as a base resin, the content of the number-average molecular weight of 2500 or more hindered amine light stabilizer is more than 0.08 mass% 0. A sheet forming step of melt molding a sealing material composition of 5% by mass or less to obtain an uncrosslinked sealing material sheet, and the uncrosslinked sealing material sheet are subjected to crosslinking treatment by irradiation with ionizing radiation, At the same time, an ionizing radiation irradiation step of decomposing 10% to 75% of the hindered amine light stabilizer into a low molecular compound having a number average molecular weight of 1000 or less, a method for producing a sealing material sheet for a solar cell module.

  ADVANTAGE OF THE INVENTION According to this invention, in the sealing material sheet for solar cell modules which used low density polyethylene as base resin, the sealing material sheet for solar cell modules which has sufficient adhesiveness can be provided.

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

<Sealing material sheet>
Sealing material sheet for a solar cell module of the present invention (hereinafter, simply referred to as "sealing material sheet") has a density of 0.870 g / cm ³ or more 0.940 g / cm ³ or less, preferably, density 0. 870 g / cm ³ or more 0.900 g / cm ³ or less of the polyethylene resin and the hindered amine light stabilizer of molecular weight type as explained in detail below (HALS) and a decomposition product of the HALS, piperidine A low molecular compound having a ring is contained as an essential component. The details of the molecular structure and the like of the low molecular compound peculiar to this application (hereinafter also simply referred to as “low molecular compound”) will be described later.

  And the sealing material sheet for solar cell modules of this invention contains the said polyethylene-type resin used as base resin at least among said essential components, and the sealing material composition formed by high molecular weight type HALS. The resin sheet obtained by melt-molding the product is further irradiated with ionizing radiation and the like, whereby a part of HALS is decomposed to lower the molecular weight to obtain the above low molecular compound.

[Polyethylene resin]
As the base resin, the density in the present invention is 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin, preferably, density 900 g / cm ³ or less of low density polyethylene (LDPE), more preferably a straight Chain low density polyethylene (LLDPE) is used. The linear low density polyethylene is a copolymer of ethylene and α-olefin, and in the present invention, the density is 0.900 g / cm ³ or less, preferably 0.870 g / cm ³ or more and 0.890 g / cm ^3. The range is as follows. If it is this range, favorable transparency and heat resistance can be provided, maintaining sheet workability.

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

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

  The melt mass flow rate (MFR) of the polyethylene resin is preferably 1.0 g / 10 min or more and 40 g / 10 min or less at 190 ° C. and a load of 2.16 kg, preferably 2 g / 10 min or more and 40 g / 10 min or less. More preferably it is. When the MFR is in the above range, the processability during film formation is excellent. In addition, about MFR after the crosslinking process by irradiation of ionizing radiation, it is preferable that it is 0.1 g / 10min or more and 5.0 g / 10min or less.

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

  The “polyethylene resin” in the present invention includes 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. Examples include resins obtained by copolymerizing a plurality of different compounds having an ethylenically unsaturated bond, and modified resins obtained by grafting different chemical species to these resins.

  Among these, a silane copolymer obtained by copolymerizing at least an α-olefin and an ethylenically unsaturated silane compound as a comonomer can be preferably used. By using such a resin, adhesiveness between a member such as a transparent front substrate or a solar cell element and a solar cell module sealing material can be obtained. In particular, in a resin sheet having a polyethylene-based resin as a base resin like the encapsulant sheet of the present invention, it is possible to use a composition containing this silane copolymer rather than by external addition of a silane coupling agent. It is more effective in improving adhesion and adhesion durability.

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

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

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

  Examples of the copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensate thereof include, for example, one or more α-olefins and, if necessary, other unsaturated monomers. One or two or more kinds are polymerized simultaneously or stepwise in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent, using a desired reaction vessel, and then the polymerization. 1 to 2 or more types of ethylenically unsaturated silane compounds are graft-copolymerized to the polyolefin-based polymer produced by the above, and further, if necessary, a graft copolymer produced by the copolymer is constituted. A silane compound portion can be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof. .

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

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

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

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

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

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

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

  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 relative to the total copolymer mass. Preferably, about 0.01 to 5 mass%, particularly preferably about 0.05 to 2 mass% is desirable. In the present invention, when the content of the ethylenically unsaturated silane compound constituting the copolymer of the α-olefin and the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent, but the content is excessive. When it becomes, it exists in the tendency which is inferior to tensile elongation, heat-fusibility, etc.

Content of said polyethylene-type resin in a sealing material sheet should just be 90 mass% or more in all the resin components of a sealing material sheet, and it is preferable that it is 99.9 mass% or more. Within that range, other resins may be included. Examples of other resins include other polyethylene resins exceeding 0.940 g / cm ³ . These may be used, for example, as an additive resin, or may be used to masterbatch other components at the composition stage.

[Hindered amine light stabilizer (HALS)]
The sealing material sheet of the present invention contains a hindered amine light stabilizer (HALS). Further, the number average molecular weight of the HALS is preferably 2500 or more, and the melting point thereof is preferably 80 ° C. or less.

  Furthermore, said HALS contained in the sealing material sheet | seat of this invention is butanedioic acid 1- [2- (4-hydroxy-2,2,6,6) represented by said general formula (Formula 1). -Tetramethylpiperidino) ethyl] (hereinafter also referred to as “HALS1”) is more preferable. This compound itself is already known. For example, “TINUVIN 622 (trade name), (melting point: 50 to 70 ° C., number average molecular weight: 3100 to 4000)” (manufactured by BASF) as a light-resistant stabilizer HALS (HALS1) contained in the sealing material sheet can be used as an essential additive in the production of the sealing material sheet of the present invention.

  Since HALS having a structure represented by the above general formula (Chemical Formula 1) contains only one piperidine ring, an amount of a predetermined amount or more necessary for sufficiently enhancing light resistance is added to the sealing material composition. Even if it is added, the occurrence of bleed-out is easily suppressed, which can contribute to the improvement of the base material adhesion and optical properties of the sealing material.

  On the other hand, a low molecular weight type HALS having a number average molecular weight of about 1000 or less as represented by TINUVIN 770 (number average molecular weight 481) is easy to bleed out due to the low molecular weight, and the amount necessary for the present invention is not contained in the resin. It is not preferable because it is difficult to knead into the above.

  Content of said HALS is 0.08 mass% or more and 0.5 mass% or less in the resin component of a sealing material sheet, Preferably, 0.1 mass% or more and 0.3 mass% or less It is. If it is less than 0.08% by mass, the function as a light-resistant stabilizer becomes insufficient, and adhesion failure or the like after long-term use occurs, which is not preferable. On the other hand, if it exceeds 0.5% by mass, HALS bleed out may occur. Even if HALS having a number average molecular weight outside the above range is contained in an extremely small amount, it is within the scope of the present invention. The trace amount is, for example, less than 0.01% by mass in the composition.

[Low molecular compounds]
The sealing material sheet of the present invention further contains a “low molecular weight compound” having a specific structure, which will be described in detail below, as an essential component. A low molecular compound is a decomposition product of the above-mentioned HALS contained in the encapsulant sheet, and is a low molecular compound having a piperidine ring and having a number average molecular weight of 1000 or less.

  The low molecular weight compound having “piperidine ring” is, for example, a case where HALS contained in the encapsulant sheet is HALS having a structure represented by the above general formula (Formula 1). In the above molecular structure, a compound in which the number average molecular weight is reduced to 1000 or less by cutting other bonding sites (for example, OH group) other than the portion forming the piperidine ring (nitrogen-containing six-membered ring), In addition, it refers to a low molecular compound that still retains the piperidine ring.

  Moreover, among the above, the low molecular compound having a number average molecular weight of 1000 or less is more preferably a low molecular compound having a piperidine ethanol configuration. Note that the low molecular weight type HALS such as the above TINUVIN 770 (number average molecular weight 481) has a number average molecular weight of about 1000, but does not have a piperidine ethanol structure, and therefore has the above “piperidine ethanol structure”. Not included in low molecular weight compounds.

  The content of the low molecular compound is 10% or more and 75% or less, and more preferably 20% or more and 50% or less of the content of the HALS contained in the sealing material sheet.

  By including the low molecular weight compound having the above specific structure in a content within the above specific range, the sealing material sheet of the present invention has improved adhesion. And this effect is an effect that does not appear when a simple low molecular weight type HALS whose structure is different from the predetermined structure of the present application is additionally contained in the encapsulant sheet with the same content ratio, This is a special effect that only the sealing material sheet of the invention has. The details of the mechanism of this effect are not necessarily clear, but the encapsulant sheet contains an unstable low-molecular compound that easily recombines and a light-resistant stabilizer, and is laminated on the encapsulant sheet. It is presumed that this is because chemical bonding with other base material is likely to occur. In addition, such an improvement in adhesion is considered to be due to the fact that the adhesion component needs to move to the interface, and the mobility is improved due to the low molecular weight.

[Other additives]
In any of the encapsulant sheets, the following additives can be appropriately contained as necessary.

(Crosslinking agent)
The encapsulant sheet may contain a necessary minimum amount of crosslinking agent at the composition stage, but it is more preferable not to contain a crosslinking agent. By adding a crosslinking aid described later, adequate crosslinking can proceed sufficiently. On the other hand, when a crosslinking agent such as an organic peroxide is added separately, for integration with the solar cell module. This is because there is an increased risk of problems such as foaming due to degas during the heat laminating process. When adding a crosslinking agent in a suitable amount range, a well-known thing can be used and it does not specifically limit, For example, a well-known radical polymerization initiator can be used.

  When the crosslinking agent is added, the content is preferably 0 part by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass in total of all the resin components in the encapsulant composition. More preferably, it is in the range of 0.02 parts by mass or more and 0.5 parts by mass or less. When the addition amount of the cross-linking agent exceeds 0.5 parts by mass, the progress of cross-linking in the cross-linking step becomes excessive, and molding characteristics become insufficient, which is not preferable.

(Crosslinking aid)
It is preferable that the encapsulant sheet contains a crosslinking aid in addition to the base resin in the composition stage. As a crosslinking aid, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group can be preferably used. More preferably, the cross-linking aid is one in which the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. By adding such a crosslinking aid, the crystallinity of the low density polyethylene can be reduced, and a crosslinked encapsulant sheet excellent in low temperature flexibility can be obtained.

  Specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA) , Ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, etc. ) An acryloxy compound, a glycidyl methacrylate containing a double bond and an epoxy group, 4-hydroxybutyl acrylate glycidyl ether and 1, containing two or more epoxy groups - hexanediol diglycidyl ether, and 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, an epoxy-based compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

(Adhesion improver)
In any of the sealing material sheets of the present invention, an adhesion improver may be appropriately added. Thereby, adhesion durability with another base material can be improved further. As the adhesion improver, a known silane coupling agent can be used. The silane coupling agent is not particularly limited. For example, vinyl-based silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyldiethoxy. A methacryloxy-based silane coupling agent such as silane or 3-methacryloxypropyltriethoxysilane can be preferably used. In addition, these can also be used individually or in mixture of 2 or more types.

  When adding a silane coupling agent as an adhesion improver, the content is 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass in total of all resin components of the sealing material composition. Yes, and the upper limit is preferably 5.0 parts by mass or less. When the content of the silane coupling agent is in the above range, and the polyolefin resin constituting the encapsulant composition contains an appropriate amount of the ethylenically unsaturated silane compound, the adhesion is more preferable. And improve. In addition, when it exceeds this range, the film-forming property is deteriorated, or so-called bleed-out in which the silane coupling agent aggregates and solidifies with time and is pulverized on the surface of the sealing material sheet is not preferable.

(Other ingredients)
The sealing material sheet can further contain other components. For example, components such as various fillers, ultraviolet absorbers, heat stabilizers and antioxidants are exemplified. These content ratios vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001 to 60% by mass in the encapsulant composition. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant composition.

  The encapsulant sheet is obtained by molding and processing the encapsulant composition containing each component described above by a conventionally known method, and is formed into a single-layer or multilayer sheet or film It is. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  The encapsulant sheet is formed into a sheet by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding, which are usually used in ordinary thermoplastic resins. In addition, as an example of the sheet forming method when the encapsulant sheet is a multilayer sheet, a method of forming by co-extrusion using two or more types of melt-kneading extruders can be given.

  The encapsulant sheet preferably has a gel fraction of 0% at the intermediate stage when it is formed into a sheet from the encapsulant composition. Further, the gel fraction in the finished product stage at the time when it is completed as a sealing material sheet through crosslinking treatment by irradiation with ionizing radiation is 25% or less, preferably 10% or less, more preferably 0%. Including 1% or less. Further, the encapsulant sheet may be of a type in which cross-linking further proceeds during thermal lamination treatment for integration as a solar cell module. In that case, it is preferable that the gel fraction of the sealing material sheet after integration as an integrated solar cell module is about 30% to 80%.

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

  When the encapsulant sheet is a multi-layer sheet, it is more preferable to use an encapsulant sheet in which MFR, gel fraction, molecular weight, etc. are separately optimized for each layer. As will be described later, in the solar cell module, the sealing material sheet is generally used with one surface being in close contact with the electrode surface of the solar cell element. In that case, the encapsulant sheet is required to have high adhesion regardless of the unevenness of the electrode surface. Even when the encapsulant sheet of the present invention is a single-layer encapsulant sheet, the encapsulant sheet has preferable adhesion. It is more preferable that it is excellent in molding characteristics. For example, by disposing a layer having a high MFR in the outermost layer on the side to be used in close contact with the electrode surface of the solar cell element, while maintaining preferable heat resistance and the like as a sealing material sheet for a solar cell module, The molding characteristics in the contact surface with the battery element can be further enhanced.

  For example, in the encapsulant sheet that is a multilayer sheet 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 The thickness ratio is preferably in the range of outermost layer: intermediate layer: outermost layer = 1: 3: 1 to 1: 8: 1. By doing in this way, while maintaining the preferable heat resistance as a sealing material, the preferable molding characteristic in an outermost layer can be provided, and also manufacturing cost can be suppressed low.

<Method for producing sealing material sheet>
The sealing material sheet of the present invention can be manufactured by a manufacturing method including at least a sheet forming step and a crosslinking step described below using the above-described sealing material composition having a unique composition according to the present invention. it can.

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

  The lower limit of the molding temperature during molding may be any temperature that exceeds the melting point of the encapsulant composition. The upper limit of the molding temperature is the temperature at which crosslinking does not start during film formation, that is, the temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, depending on the 1 minute half-life temperature of the crosslinking agent used. Good. Here, in the method for producing a sealing material sheet of the present invention, a crosslinking agent is not essential in the sealing material composition, and even when a crosslinking agent is added, its content is less than 0.5% by mass. It is limited to. For this reason, under a normal low density polyethylene resin molding temperature, for example, a heating condition of about 120 ° C., the gel fraction does not change, and the crosslinking that substantially affects the physical properties of the resin does not proceed. In addition, as described above, it is possible to use a cross-linking agent having a half-life temperature higher than that of the conventional one by solving from the limitation of the heating conditions in the modularization process. Therefore, even if the molding temperature is set higher than before, the gel fraction of the encapsulant composition can be maintained at 0%. According to the production method of the present invention that maintains the gel fraction of the encapsulant composition during film formation at 0%, the load on the extruder and the like during film formation is reduced, and the productivity of the encapsulant sheet is increased. It is possible.

[Ionizing radiation irradiation process]
The uncrosslinked encapsulant sheet after the sheet forming step is subjected to a crosslinking treatment with ionizing radiation, and at the same time, the ionizing radiation irradiation step for decomposing part of the HALS to lower the molecular weight is completed. After and before the start of the solar cell module integration step of integrating the sealing material sheet with other members.

  The gel fraction of the encapsulant sheet is set to 0% or more and 25% or less, preferably 10% or less, more preferably 1% or less including 0% by the progress of crosslinking by irradiation with ionizing radiation. The cross-linking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line.

  In addition, due to the progress of crosslinking by irradiation with ionizing radiation, HALS in the encapsulant sheet is reduced in molecular weight by preferentially dividing structural parts other than the piperidine ring part such as OH group, and many of them are It becomes a low molecular compound having the specific structure described in 1.

  The irradiation conditions of ionizing radiation are not particularly limited. It is only necessary to be in a range necessary for appropriate crosslinking to proceed, and by performing ionizing radiation under such conditions, the above-described reduction in the molecular weight of HALS can be promoted to an appropriate degree. Specifically, according to the density of the base resin, the sheet thickness, and other conditions, the gel fraction of the cross-linked encapsulant sheet may be set as appropriate within a desired range. The ionizing radiation can be an electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. Further, the ionizing radiation may be irradiated from one side or from both sides.

  When ionizing radiation is applied by single-sided irradiation, the acceleration voltage is determined by the thickness of the sheet that is the object to be irradiated, and a thicker sheet requires a larger acceleration voltage. For example, in the case of a sheet having a thickness of 0.6 mm, irradiation is performed at 200 kV to 1000 kV, preferably 250 kV to 1000 kV. When the acceleration voltage is less than 200 kV, electrons do not pass through to the outermost layer on the non-irradiated surface side, and the heat resistance of the encapsulant sheet becomes insufficient. The irradiation dose is in the range of 5 kGy to 800 kGy, preferably 10 kGy to 50 kGy. Irradiation may be in an air atmosphere or a nitrogen atmosphere.

  This crosslinking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line. Further, when the crosslinking treatment is a general heat treatment, generally, the content of the crosslinking agent is 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of all components of the sealing material sheet. However, in the sealing material sheet of the present invention, the content of the crosslinking agent may be 0, and even if it is contained, it is preferably less than 0.5 parts by mass. Thereby, the risk of the productivity fall by gelatinization of the sealing material composition in the sheeting process of a sealing material composition can be reduced.

<Solar cell module>
Next, an example of the solar cell module of the present invention will be described with reference to the drawings. 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 sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 are sequentially laminated from the incident light receiving surface side. ing. The solar cell module 1 of the present invention uses the encapsulant sheet of the present invention as the front encapsulant layer 3 serving as at least the light-receiving surface side encapsulant layer. In addition, about the back surface sealing material layer 5, although the sealing material sheet of this invention can also be used, you may use the white sealing material sheet etc. which have reflection performance, for example. Further, in the case of a double-sided lighting type module, the sealing material sheet of the present invention can be preferably used for both the front sealing material layer 3 and the back sealing material layer 5.

  The solar cell module 1 includes, for example, the transparent front substrate 2, the encapsulant sheet that forms the front encapsulant layer 3, the encapsulant sheet that forms the solar cell element 4, the back encapsulant layer 5, and the back surface. The members made of the protective sheet 6 can be sequentially laminated and then integrated by vacuum suction or the like, and then the above-mentioned members can be manufactured by thermocompression forming as an integrally formed body by a molding method such as a lamination method.

  Further, the solar cell module 1 is formed on the front side and the back side of the solar cell element 4 by a molding method usually used in ordinary thermoplastic resins, for example, T-die extrusion molding. In order to form the back surface sealing material layer 5, the sealing material composition according to the present invention is melt-laminated, the solar cell element 4 is sanded, and then the transparent front substrate 2 and the back surface protective sheet 6 are sequentially laminated, Then, they may be manufactured by a method in which these are integrated by vacuum suction or the like and heat-pressed.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4 and the back surface protection sheet 6 which are members other than the front sealing material layer 3 and the back sealing material layer 5 are made of conventionally known materials. It can be used without particular limitation. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. The sealing material sheet of the present invention is not limited to a general single crystal type solar cell element, but includes all other solar cell elements such as a thin film type solar electronic element or a back contact type solar electronic element. It can be used for a solar cell module to be mounted.

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

<Manufacture of sealing material for solar cell module>
Resin sheets for sealing material sheets of Examples and Comparative Examples were molded using the sealing material compositions having the compositions (unit parts by mass) shown in Table 1. First, the sealing material composition was formed into a sheet at an extrusion temperature of 210 ° C. and a take-off speed of 1.5 m / min using a φ30 mm extruder and a film molding machine having a 200-mm width T die, respectively. The layer thickness of these resin sheets was 450 μm.

The following raw materials were used as the sealing material composition raw material.
Base resin: Metallocene linear low density polyethylene (M-LLDPE) having a density of 0.880 g / cm ³ , a melting point of 60 ° C., and an MFR at 190 ° C. of 3.5 g / 10 min. 85 parts by mass of this base resin was added to the encapsulant composition used for molding the encapsulant sheets of all Examples and Comparative Examples.
Silane-modified polyethylene resin: 100 parts by mass of a metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and an MFR of 20 g / 10 min, 2 parts by mass of vinyltrimethoxysilane, and a radical generator ( Silane-modified polyethylene resin obtained by mixing 0.15 parts by mass of dicumyl peroxide as a reaction catalyst), melting and kneading at 200 ° C. Density 0.880 g / cm ³ , MFR 1.0 g / 10 min. Melting point 60 ° C. 15 parts by mass of this silane-modified polyethylene resin was added to the encapsulant compositions used for molding the encapsulant sheets of all Examples and Comparative Examples.
Hindered amine light stabilizer 1 (indicated as “H” in Table 1, hereinafter the same): KEMISTAB 62, number average molecular weight 3100 to 4000, melting point 50 to 70 ° C. Only 0.2 parts by mass of each of the sealing material compositions used for molding the sealing material sheets of Example 1 and Comparative Example 1 was added.
Crosslinking agent: 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (trade name “Lupelox 101” manufactured by Arkema Yoshitomi Co., Ltd.) was used only for the sealing material composition of Comparative Example 1. , 0.08 parts by mass of each was added.

In addition, the following additive was added to each sealing material composition of an Example and a comparative example.
Antioxidant: Ciba Japan Co., Ltd., trade name Irganox 1076. 0.05 parts by mass are added to each of the sealing material compositions of Examples and Comparative Examples.

  Next, using an electron beam irradiation apparatus (product name EC250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) for the resin sheet for the examples, the acceleration voltage is 200 kV and the irradiation intensity is about each example and comparative example 2. Moreover, what applied the ionizing radiation from both surfaces with the intensity | strength (EB irradiation intensity) of Table 1 was used as the sealing material sheet of an Example. Further, the resin sheet for Comparative Example 1 was used as the sealing material sheet of Comparative Example 1 as it was without being irradiated with ionizing radiation.

For each encapsulant sheet of Examples and Comparative Examples, as described below, component analysis by gas chromatograph mass spectrometry method is performed, decomposition products contained in each encapsulant sheet, having a piperidine ring, The content of low molecular weight compounds having a number average molecular weight of 1000 or less was measured. In Table 1, the above-mentioned low molecular weight compound having a piperidine ring as a decomposition product of “H” is indicated as “h”. The results are shown in Table 1. The content of this low molecular compound was measured by the following measuring method.
(Measurement of the content of low molecular weight compounds by gas chromatography mass spectrometry)
0.1 g of the sealing material is dissolved in 50 ml of 60 ° toluene, and 200 ml of methanol is added dropwise to sink only the resin. The solvent in which the additive is dissolved is analyzed and quantified with a gas chromatograph mass spectrometer.

<Evaluation example: Metal adhesion>
Each of the sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm was brought into close contact with each other on a copper plate (75 mm × 50 mm × 0.1 mm) and subjected to a vacuum heating laminator treatment under the following heat laminating conditions. Samples for metal adhesion evaluation were obtained for Examples, Comparative Examples, and Reference Examples. About these metal adhesion evaluation samples, the adhesion rejection under the following test conditions was measured to evaluate the metal adhesion. The results are shown in Table 2.
(Thermal lamination conditions) (a) Vacuum drawing: 5.0 minutes
(B) Pressurization (0 kPa to 100 kPa): 1.5 minutes
(C) Pressure holding (100 kPa): 8.0 minutes
(D) Temperature 150 ° C
[Test method for adhesion strength (N / 15 mm)]
Peeling test method: In the above sample for evaluating metal adhesion, the sealing material sheet in close contact with the copper plate was subjected to a vertical peeling (50 mm / min) test using a peeling tester (Tensilon Universal Tester RTF-1150-H). The metal adhesion strength was measured. In this test, a sheet having an adhesion strength of 10 N / 15 mm or more was evaluated as a sealing material sheet having preferable metal adhesion.

  As can be seen from Tables 1 and 2, the sealing material sheet of the present invention containing low-density polyethylene as a base resin and containing a low-molecular compound having a specific structure is more suitable than a sealing material sheet containing no such compound. It turns out that it has favorable adhesiveness.

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

Claims (3)

Density 0.870 g / cm ³ or more 0.940 g / cm ³ or less of the polyethylene resin as a base resin, the general formula (Formula 1) with a compound an a with a number average molecular weight of 2500 or more hindered amine light stabilizer represented by the following A sheet forming step of obtaining an uncrosslinked sealing material sheet by melt-molding a sealing material composition having a content of the agent of 0.08% by mass or more and 0.5% by mass or less;
Ionizing radiation that crosslinks the uncrosslinked encapsulant sheet by irradiation with ionizing radiation, and simultaneously decomposes 10% to 75% of the hindered amine light stabilizer into a low molecular compound having a number average molecular weight of 1000 or less. An irradiation process,
The content of the low-molecular compound contained in the encapsulant sheet after the ionizing radiation irradiation step measured by component analysis using a gas chromatograph mass spectrometry method is 0 as a content ratio with respect to the total resin components of the encapsulant sheet. The manufacturing method of the sealing material sheet | seat for solar cell modules which irradiates ionizing radiation with the acceleration voltage and irradiation amount which are 0.01 mass% or more and 0.07 mass% or less .

The method for producing a sealing material sheet according to claim 1 , wherein the polyethylene resin is a metallocene linear low-density polyethylene. The said polyethylene-type resin is a manufacturing method of the sealing material sheet of Claim 1 or 2 containing the silane copolymer formed by copolymerizing at least (alpha) -olefin and an ethylenically unsaturated silane compound as a comonomer.

Images