JP5866857B2 - Solar cell module sealing material composition, solar cell module sealing material sheet - Google Patents

Description

  The present invention relates to a solar cell module encapsulant composition and a solar cell module encapsulant sheet using the same, and more specifically, various constituent members of a solar cell module such as a glass substrate and a resin base material. The present invention relates to a sealing material composition for a solar cell module excellent in adhesion durability with a substrate, a sealing material sheet for a solar cell module, and a solar cell module using the same.

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

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

  An ethylene-vinyl acetate copolymer resin as a sealing material that is 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. (EVA) has been used as the most common, but in recent years, instead of EVA resin, as a solution to the problem of reduced water vapor barrier properties in long-term use, which is a drawback of EVA resin, A sealing material for a solar cell module using a polyolefin-based resin has been proposed.

  Polyolefin-based encapsulants tend to lack transparency and flexibility compared to encapsulants that use EVA resin, but a resin that combines multiple low-density polyethylenes in a specific density range. A sealing material using a low-density polyolefin having improved transparency and flexibility as a base resin has been proposed (Patent Document 1).

  However, the above-mentioned sealing material using a low-density polyolefin-based resin as a base resin still has room for improvement in heat resistance after modularization due to its low density. Therefore, the heat resistance of the sealing material is improved by crosslinking a low-density polyolefin resin. Such a low-density polyolefin-based resin as a base resin and a sealing material comprising a sealing material composition further containing a crosslinking agent is subjected to a crosslinking treatment in any step until modularization, It becomes a sealing material excellent in transparency, flexibility and heat resistance.

JP 2011-37883 A

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

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is based on a low-density olefin-based resin, and is transparent by performing a crosslinking treatment in any process up to modularization. An object of the present invention is to provide a solar cell module using a sealing material excellent in properties, flexibility, and heat resistance, and having excellent adhesion durability between various substrates.

  The present inventors have achieved transparency, flexibility, and heat resistance by using a sealing material composition based on a low-density polyolefin resin in which the amount of double bonds remaining in the resin is in a specific range. In addition, it has been found that a solar cell module sealing material sheet having excellent adhesion durability with various base materials can be obtained, 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 sealing material, which is a total of linear low density polyethylene having a density of 0.900 g / cm ³ or less and all resin components in the sealing material composition A crosslinking agent containing 0.02 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass, and the number of total double bonds per 2000 carbons by infrared absorption spectroscopy is 1.8 or more 3 .3 or less encapsulant composition

  (2) The encapsulant composition according to (1), wherein the number of terminal vinyl groups per 2000 carbons is 0.7 or more by infrared absorption spectroscopy.

  (3) The sealing material composition according to (1) or (2), further comprising a silane-modified polyethylene resin obtained by graft polymerization using an ethylenically unsaturated silane compound as a side chain.

  (4) The sealing material composition according to any one of (1) to (3), further containing a silane coupling agent.

  (5) The sealing material composition according to any one of (1) to (4), further comprising a crosslinking aid that is a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group.

  (6) A sealing material sheet obtained by melt-molding the sealing material composition according to (5), wherein the number of full double bonds per 2000 carbons by infrared absorption spectrum method is 1.7 or more. The solar cell module sealing material sheet which is 3.0 or less and has a gel fraction of 2% or more and 80% or less.

  (7) A solar cell module using a sealing material sheet obtained by melt-molding the sealing material composition according to any one of (1) to (5), wherein the solar cell module is integrated with the solar cell module. The solar cell module in which the number of full double bonds per 2000 carbon by the infrared absorption spectrum method of the sealing material sheet is 1.7 or more and 3.0 or less, and the gel fraction is 80% or less.

  According to the present invention, it is a sealing material based on a low-density olefin-based resin and subjected to a crosslinking treatment, which is excellent in transparency, flexibility, and heat resistance, and in excellent adhesion durability to various substrates. It is possible to provide a sealing material having the above characteristics and a solar cell module using the same.

It is sectional drawing which shows an example of the laminated constitution about the solar cell module using the sealing material sheet which concerns on this invention.

  Hereinafter, a sealing material composition for a solar cell module according to the present invention (hereinafter also simply referred to as a sealing material composition), a sealing material sheet for a solar cell module (hereinafter also simply referred to as a sealing material sheet), a solar cell. The module will be described, and then the manufacturing method of the encapsulant sheet and the manufacturing method of the solar cell module will be described in detail sequentially.

<Encapsulant composition>
In the present invention, for the encapsulant composition used for the production of the encapsulant sheet for solar cell module, paying attention to the number of double bonds in the resin that has not been noticed conventionally, the number is within a predetermined range. It is characterized in that the base resin of the sealing material composition is limited to a certain low density polyethylene. Therefore, first, such a sealing material composition will be described.

  The number of full double bonds per 2000 carbons of the encapsulant composition used in the present invention is 1.8 or more and 3.3 or less. By limiting the base resin so that the number of double bonds of the encapsulant composition falls within this range, the adhesion durability of the encapsulant sheet for solar cell modules with various substrates is remarkably improved. The point is a feature of the present invention. When the number of double bonds of the encapsulant composition is less than 1.8, the adhesion durability between the encapsulant sheet and various base materials is not sufficiently improved, and when the number exceeds 3.3, It is not preferable because the adhesiveness may be lowered due to excessive crosslinking.

  Further, the number of terminal vinyls per 2,000 carbons of the encapsulant composition used in the present invention is preferably 0.7 or more per 2,000 carbons because the reactivity is particularly high among double bonds. If the number of remaining terminal vinyl groups is less than 0.7, the adhesion durability between the encapsulant sheet and various base materials is insufficiently improved.

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

  The sealing material composition of this invention contains the linear low density polyethylene (LLDPE) which has a predetermined physical property, and a crosslinking agent in a predetermined ratio. Hereinafter, after describing the essential components, other resins and other components will be described.

[Linear low density polyethylene]
In the present invention, linear low density polyethylene (LLDPE) having a density of 0.900 / cm ³ or less is used. Linear low density polyethylene is a copolymer of ethylene and α- olefin, in the present invention, within the scope thereof density of 0.900 g / cm ³ or less, preferably 0.890 g / cm ³ within the following ranges More preferably, it is the range of 0.870-0.885 g / cm < ³ >. If it is this range, favorable softness | flexibility and transparency can be provided, maintaining sheet workability.

  As the LLDPE used in the sealing material composition of the present invention, a metallocene linear low density polyethylene can be preferably used. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform comonomer distribution. For this reason, molecular weight distribution is narrow, it is possible to make it the above ultra-low density, and a softness | flexibility can be provided with respect to a sealing material sheet. As a result of imparting flexibility, the adhesion between the sealing material sheet and the glass front substrate, the adhesion between the sealing material sheet and the substrate, such as the adhesion between the sealing material sheet and the back surface protection sheet, is increased.

  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 sheet which consists of a sealing material composition of this invention is arrange | positioned between a glass transparent front substrate and a solar cell element, power generation efficiency hardly falls.

  As the α-olefin of the linear low density polyethylene, an α-olefin having no branch is preferably used. Among these, 1-hexene and 1-heptene which are α-olefins having 6 to 8 carbon atoms are preferable. Or 1-octene is particularly preferably used. When the number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material sheet can be given good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and the substrate is further enhanced.

  Moreover, in this invention, MFR in 190 degreeC and load 2.16kg measured by JIS-K6922-2 as said LLDPE (Hereinafter, the measured value by this measurement condition is called MFR in this specification.). Is preferably 6.0 g / 10 min to 40.0 g / 10 min. The MFR is preferably 10 g / 10 min or more and 40.0 g / 10 min or less, and more preferably 12 g / 10 min or more and 40.0 g / 10 min or less. If it is this range, the fluidity | liquidity of a sealing material will be hold | maintained and sufficient adhesiveness with respect to the other structural member laminated | stacked on a sealing material sheet when integrated as a solar cell module can be provided.

  The sealing material composition of the present invention may further contain a silane-modified polyethylene resin. The silane-modified polyethylene resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain to linear low-density polyethylene (LLDPE) or the like as a main chain. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, it can improve the adhesion of the sealing material sheet to other members in the solar cell module.

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

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

  The graft amount, which is the content of the ethylenically unsaturated silane compound, is, for example, 0.001 to 15 masses with respect to a total of 100 mass parts of all the resin components in the sealing material composition containing other polyethylene-based resins described later. Part, preferably 0.01 to 5 parts by mass, particularly preferably 0.05 to 2 parts by mass. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and heat-fusibility tend to be inferior.

The content of the linear low-density polyethylene having a density of 0.900 g / cm ³ or less contained in the encapsulant composition is preferably based on 100 parts by mass of the total resin components in the encapsulant composition. Is 10 to 99 parts by mass, more preferably 50 to 99 parts by mass, and still more preferably 90 to 99 parts by mass. As long as the melting point of the encapsulant composition is less than 80 ° C. and the number of double bonds of the encapsulant composition is in the range of 1.8 to 3.3 as described above, other The resin may be included. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later. In the present specification, the term “all resin components” includes the other resins described above.

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

  As content of a crosslinking agent, it is preferable that it is content of 0.02 mass part or more and 2.0 mass parts or less with respect to a total of 100 mass parts of all the resin components of a sealing material composition, More preferably, it is 0. The range is 3 parts by mass or more and 1.5 parts by mass or less. By adding 0.02 parts by mass or more of a crosslinking agent, sufficient durability can be imparted to the linear low-density polyethylene used in the sealing material sheet of the present invention. On the other hand, when the addition amount of the cross-linking agent exceeds 2.0 parts by mass, the progress of cross-linking in the cross-linking process becomes excessive, and the followability to the unevenness of other members at the time of modularization becomes unfavorable.

[Crosslinking aid]
In the present invention, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group can be used as a crosslinking aid. More preferably, the cross-linking aid is one in which the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. Thereby, in any process until the integration process as a solar cell module is finished, an appropriate crosslinking reaction is promoted, and the gel fraction of the sealing material sheet in a state integrated as a solar cell module is 80. % Or less.

  When the encapsulant sheet of the present invention is a crosslinked encapsulant sheet that has undergone a crosslinking treatment before the integration step as a solar cell module, the above-mentioned carbon-carbon double bond is used as a crosslinking aid. And / or a polyfunctional monomer having an epoxy group. Thereby, an appropriate crosslinking reaction is promoted, and the gel fraction is adjusted to 2% or more and 80% or less.

  In the present invention, the crosslinking aid reduces the crystallinity of the linear low density polyethylene and maintains transparency. Thereby, the crosslinked sealing material sheet excellent in transparency and 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) Poly (meth) acryloxy compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, Glycidyl methacrylate containing epoxy groups, 4-hydroxybutyl acrylate glycidyl ether and 1,6-hexanediol diglycidyl ether containing two or more epoxy groups, 1 4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and epoxy compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among the above, the effect of improving the adhesion to the glass surface is particularly high, the compatibility with low density polyethylene is good, the crystallinity is lowered by crosslinking, the transparency is maintained, and the flexibility at low temperature is given. From this viewpoint, TAIC can be particularly preferably used. Moreover, 1,6-hexanediol diacrylate can also be preferably used from a reactive viewpoint with a silane coupling agent.

  As content of a crosslinking adjuvant, it is preferable that 0.01 mass part-3 mass parts are contained with respect to a total of 100 mass parts of all the resin components of a sealing material composition, More preferably, it is 0.05 mass part. It is the range of -2.0 mass parts. Within this range, an appropriate crosslinking reaction can be promoted to make the gel fraction of the encapsulant sheet 80% or less. By setting the gel fraction to 80% or less, it is preferable because flexibility equal to or higher than EVA can be obtained in a low temperature range from −50 ° C. to 0 ° C. while having the same degree of transparency as conventional EVA.

[Adhesion improver]
By adding an adhesion improver to the encapsulant composition, it is possible to further improve the adhesion durability with other substrates such as glass. As the adhesion improver, a known silane coupling agent can be used. The silane coupling agent is not particularly limited. For example, vinyl-based silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyldiethoxy. A methacryloxy-based silane coupling agent such as silane or 3-methacryloxypropyltriethoxysilane can be preferably used. In addition, these can also be used individually or in mixture of 2 or more types.

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

[Radical absorbent]
The degree of crosslinking can be further finely adjusted by using the above-mentioned crosslinking assistant serving as a radical polymerization initiator in combination with the radical absorbent for quenching it. Examples of such radical absorbents include hindered phenol-based antioxidants, hindered amine-based weather resistance stabilization, and the like. A hindered phenol-based radical absorbent having a high radical absorbing ability near the crosslinking temperature is preferred. It is preferable that the usage-amount of a radical absorber is contained 0.01 mass part-3 mass parts with respect to a total of 100 mass parts of all the resin components of a sealing material composition, More preferably, 0.05 mass part-2 The range is 0.0 parts by mass.

[Other ingredients]
The sealing material composition may further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance to a sealing material sheet produced from the sealing material composition of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, and a heat stabilizer Illustrated. These contents vary depending on the particle shape, density, and the like, but are within the range of 0.001 to 5 parts by mass with respect to 100 parts by mass in total of all resin components of the sealing material composition. Is preferred. 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.

  A weatherproof masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and adding this to a sealing material composition. Thus, good weather resistance can be imparted to the encapsulant sheet. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. The resin used in the weatherproof masterbatch may be a linear low density polyethylene used in the present invention, or other resins described above.

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

<Sealing material sheet>
The encapsulant sheet of the present invention is obtained by melt-molding the above encapsulant composition at a temperature exceeding its melting point to form a sheet or a film, and has undergone a crosslinking treatment after the melt formation. It is a sealing material sheet. The gel fraction of the crosslinked encapsulant sheet is 2% or more and 80% or less. When the gel fraction is within these ranges, the sealing property to the unevenness can be maintained well. In addition, the dimensional stability at the time of shaping | molding can be made very high because a gel fraction shall be 25% or more.

  The number of full double bonds per 2000 carbons derived from all resin components of the crosslinked encapsulant sheet is 1.7 or more and 3.0 or less. The number of double bonds in the encapsulant composition stage and the decrease in the number of double bonds in the stage after being integrated as a solar cell module through a crosslinking treatment are approximately 10% regardless of the type of resin. It is known that the number of double bonds of the encapsulant sheet in the state after the cross-linking treatment is within this range, so that between the encapsulant sheet and various base materials in the solar cell module The adhesion durability in can be improved.

  In addition, the sealing material sheet which comprises the solar cell module of this invention is not limited to this, A crosslinking process is used for this in the integration process as a solar cell module later using the sealing material sheet of a non-crosslinking process. You may do it. The encapsulant sheet formed by melt-forming the encapsulant composition of the present invention is integrated as a solar cell module even if it is uncrosslinked at the stage of the encapsulant sheet, and various types are obtained at the stage of completing the crosslinking treatment. Since it has high adhesion durability with a base material, it can be preferably used as a sealing material sheet constituting the solar cell module of the present invention.

  Below, the manufacturing method of the sealing material sheet | seat which can be used for the solar cell module of this invention is demonstrated.

[Sheet making process]
The melt molding of the sealing material composition is carried out 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. At that time, the lower limit of the molding temperature may be a temperature exceeding the melting point of the encapsulant composition, and the upper limit is a temperature at which crosslinking does not start during extrusion film formation, depending on the 1-minute half-life temperature of the crosslinking agent used. There is no particular limitation as long as it is within these ranges. By this step, an uncrosslinked sealing material sheet can be obtained.

[Crosslinking process]
In the case where the encapsulant sheet of the present invention is a crosslinked encapsulant sheet that has been subjected to a crosslinking treatment before modularization, the uncrosslinked encapsulant sheet after the sheeting step is subjected to a crosslinking treatment. The processing step is performed after the sheet forming step is completed and before the start of the solar cell module integration step of integrating the sealing material sheet with another member. By this crosslinking step, the encapsulant sheet is made into a crosslinked encapsulant sheet having a gel fraction of 2% to 80%. In addition, the crosslinking treatment before the integration step of the solar cell module is not necessarily essential, and an uncrosslinked sealing material sheet using the sealing material composition may be crosslinked in the subsequent integration step of the solar cell module. Good.

  This crosslinking step performed before the integration step of the solar cell module is preferably a heat treatment, but is not limited thereto, and may be a crosslinking treatment with an electromagnetic wave such as UV (ultraviolet light) or EB (electron beam). In the case of heat treatment, the individual crosslinking conditions are not particularly limited, and may be set as appropriate so that the gel fraction is the total treatment result within the range of general crosslinking treatment conditions. In addition, when the crosslinking treatment is a heat treatment, it may also serve as an annealing treatment.

  By passing through the crosslinking step before the integration step as a solar cell module, the gel fraction of the encapsulant sheet becomes 2% or more and 80% or less. The gel fraction is more preferably 25% or more and 80% or less. When the gel fraction is 2% or more, the effect of suppressing the flow by the crosslinking step before the integration step as a solar cell module is exhibited, and the film thickness is prevented from flowing in the sealing material composition in the vacuum heating laminate. Can be kept constant. When the gel fraction exceeds 80%, the fluidity of the encapsulant composition becomes too low, and the module is not well embedded in the irregularities of the module, making it difficult to use as an encapsulant. That is, if the gel fraction is within the above range, the sealing property to the unevenness can be maintained well while suppressing excessive flow. In addition, the dimensional stability at the time of shaping | molding can be made very high because a gel fraction shall be 25% or more. Further, as will be shown later in Examples, even when a crosslinked encapsulant sheet with suppressed fluidity is used, it has sufficiently high adhesion. In addition, a bridge | crosslinking process may be performed in-line continuously following a sheet forming process, and may be performed off-line.

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

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer structure of a solar cell module according to 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 melts the sealing material composition according to the present invention in at least the front sealing material layer 3 laminated with the transparent front substrate 2 among the front sealing material layer 3 and the back sealing material layer 5. A molded sealing material sheet is used.

  As described above, the solar cell module 1 of the present invention uses the encapsulant sheet made of an encapsulant composition having a predetermined composition and a specific number of double bonds, whereby the front encapsulant layer 3 and the back surface are used. The adhesion durability between the sealing material layer 5 and other various base materials such as the transparent front substrate 2 made of glass or the like, and the back surface protection sheet 6 made of a resin base material or the like is improved.

  For example, the solar cell module 1 is formed by sequentially laminating the members including the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6, and thereafter The member can be manufactured by thermocompression molding as an integral molded body by a molding method such as a thermal lamination method.

  When the solar cell module 1 is manufactured using an uncrosslinked encapsulant sheet, the encapsulant sheet is subjected to crosslinking treatment at the time of the thermocompression molding, but the encapsulant sheet is used as a solar cell module. Combined with the case where the crosslinking treatment has been completed before the integration step, the sealing material sheet in a state integrated as a solar cell module, that is, derived from all the resin components of the sealing material sheet in a state after the crosslinking treatment The number of full double bonds per 2000 carbons is 1.7 or more and 3.0 or less. The number of double bonds in the encapsulant composition stage and the decrease in the number of double bonds in the stage after the cross-linking treatment and integration as a module are approximately 10% regardless of the type of resin. I know that it is around. By making the double bond number of the encapsulant sheet in a state integrated as a solar cell module within this range, the adhesion durability between the encapsulant sheet and various base materials in the solar cell module can be improved. Can be improved.

  Moreover, the gel fraction of the sealing material sheet in the state integrated after the crosslinking process and integrated as a solar cell module is 80% or less. When the gel fraction is within this range, it is possible to maintain good sealing performance against unevenness.

  In addition, in the solar cell module 1 of this invention, conventionally well-known things are used without a restriction | limiting especially about 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 transparent front substrate 2. FIG. be able to. About the back surface sealing material layer 5, although it is preferable to use the same sealing material sheet as the front surface sealing material layer 3, it is not necessarily restricted to this. Moreover, the solar cell module 1 of this invention may also contain members other than the said member.

  Although the mechanism for improving the adhesion durability with various substrates such as glass by limiting the number of double bonds of the encapsulant sheet to a predetermined range is not clear, the double bond amount may be within a predetermined range. This is considered to contribute to the optimization of the reaction that can improve the adhesion that occurs during the crosslinking treatment.

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

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
<Manufacture of sealing material sheet>
The components of each composition shown in Table 1 below are mixed and melted in units of parts by mass to form each encapsulant composition, and each encapsulant composition has a thickness of 400 to 480 μm by a conventional T-die method. To form an uncrosslinked sealing material sheet. The film forming temperature was 90 ° C. or higher and lower than 100 ° C.
LLDPE1 (base resin M1): a metallocene linear low-density polyethylene which is a copolymer of ethylene and 1-hexene and has a density of 0.880 g / cm ³ and MFR of ³⁰ g / 10 min.
LLDPE2 (base resin M2): a metallocene linear low-density polyethylene which is a copolymer of ethylene and 1-hexene and has a density of 0.880 g / cm 3 and MFR 3.1 g / 10 min.
Silane-modified polyethylene resin 1 (base resin S1): a copolymer of ethylene and 1-hexene, a metallocene linear low-density polyethylene resin having a density of 0.880 g / cm ³ and an MFR of 8 g / 10 min, 98 Density obtained by mixing 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) with respect to parts by mass, and melting and kneading at 200 ° C. A silane-modified polyethylene resin having 0.884 g / cm ³ and MFR 6.0 g / 10 min.
Silane-modified polyethylene resin 2 (base resin S2): metallocene linear low-density polyethylene resin having a density of 0.881 g / cm ³ and an MFR of 2 g / 10 min at 190 ° C., 98 parts by mass , 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed, melted at 200 ° C., and kneaded to obtain a density of 0.884 g / cm 3. ^3. A silane-modified polyethylene resin having an MFR of 1.8 g / 10 min.
Silane-modified polyethylene resin 3 (base resin S3): a metallocene linear low-density polyethylene resin having a density of 0.898 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min, based on 98 parts by mass , 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed, melted at 200 ° C., and kneaded to obtain a density of 0.901 g / cm ³ , a silane-modified polyethylene resin having an MFR of 1.0 g / 10 min.
Cross-linking agent 1 (labeled as cross-linking 1 in Table 1): t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi Co., Ltd., trade name Luperox TBEC)
Cross-linking agent 2 (labeled as cross-linking 2 in Table 1): 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi, trade name Luperox 101)
Crosslinking aid (labeled as support in Table 1): triallyl isocyanurate (product name SR533, manufactured by Statomer)
UV absorber (labeled UV in Table 1): Chemipro Kasei Co., Ltd., trade name KEMISORB12
Weather stabilizer (labeled as weather resistance in Table 1): Ciba Japan Co., Ltd., trade name Tinuvin 770
Antioxidant (labeled as acid protection in Table 1): Ciba Japan Co., Ltd., trade name Irganox 1076

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

  About Example 1, the bridge | crosslinking temperature was 220 degreeC, the bridge | crosslinking time was further performed for 2.5 minutes, and the crosslinking process by oven was given, and the bridge | crosslinking sealing material sheet was obtained. For Example 2, Comparative Example 1, and Comparative Example 2, an uncrosslinked sealing material sheet was obtained without performing the crosslinking treatment.

  Moreover, about the sealing material sheet | seat using each sealing material composition of Examples 1-2 and Comparative Examples 1-2, after integrating as an evaluation sample for solar cell modules through the process as demonstrated below. Then, a part of the sealing material sheet was peeled off, and the number of double bonds derived from the base resin after modularization was determined by the above formula. The results are shown in Table 2.

<Evaluation example>
Further, the sealing material sheets of Examples 1-2 and Comparative Examples 1-2 cut to a width of 15 mm are laminated on a glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm), and 150 It processed with the vacuum heating laminator in 18 degreeC and 18 degreeC, and the solar cell module evaluation sample was obtained about each Example and the comparative example. About these solar cell module evaluation samples, the adhesion maintenance rate under the following test conditions was evaluated. The results are shown in Table 3.
[Test method for adhesion maintenance rate (%)]
Peeling test method: In the above solar cell module evaluation sample, the sealing material sheet in close contact with each glass substrate was vertically peeled (50 mm / mm) with a peeling tester (Tensilon Universal Tester RTF-1150-H). min) A test was conducted to measure the adhesion strength.
Dump heat (denoted as DH in Table 3) test: Based on JIS C8917, the durability test of the sample module for evaluation was performed for 2000 hours under the conditions of 85 ° C. in the test tank and 85% humidity. The peel test was performed on the sample module for evaluation after the test.
High strength xenon (described as Xe in Table 3) Irradiation test: Based on JIS C8917, the durability test of the sample module for evaluation was performed for 2000 hours under the conditions of black panel temperature (BPT) 63 ° C. and humidity 50%. The peel test was performed on the sample module for evaluation after the test.

  From Table 2 and Table 3, the solar cell module using the sealing material sheet of Examples 1 and 2 using the sealing material composition having the number of double bonds in a specific range is the durable adhesion between the substrates. It can be seen that it is excellent.

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

Claims (7)

A sealing material composition for a solar cell module sealing material,
Linear low density polyethylene having a density of 0.900 g / cm ³ or less;
A silane-modified polyethylene resin obtained by graft polymerization using an ethylenically unsaturated silane compound as a side chain;
A crosslinking agent containing 0.02 parts by mass or more and 2.0 parts by mass or less with respect to a total of 100 parts by mass of all resin components in the sealing material composition,
An encapsulant composition having a number of full double bonds per 2000 carbons of from 1.8 to 3.3 by infrared absorption spectroscopy. The encapsulant composition according to claim 1 , wherein the number of terminal vinyl groups per 2,000 carbons by infrared absorption spectroscopy is 0.7 or more. Furthermore, the sealing material composition of Claim 1 or 2 containing a silane coupling agent. Furthermore, the sealing material composition in any one of Claim 1 to 3 containing the crosslinking adjuvant which is a polyfunctional monomer which has a carbon-carbon double bond and / or an epoxy group. A sealing material sheet formed by melt-molding the sealing material composition according to claim 4 ,
Solar cell module encapsulant sheet having a total number of double bonds per 2000 carbons by infrared absorption spectroscopy of 1.7 to 3.0 and a gel fraction of 2% to 80% . A solar cell module using the sealing material sheet formed by melting a sealing material composition according to any one of claims 1 to 4,
The encapsulant sheet integrated with the solar cell module has a number of full double bonds per 2000 carbon by an infrared absorption spectrum method of 1.7 or more and 3.0 or less, and a gel fraction is A solar cell module that is 80% or less. A method for producing a solar cell module encapsulant sheet,
Sum of all linear resin components having a density of 0.900 g / cm ³ or less, a silane-modified polyethylene resin obtained by graft polymerization using an ethylenically unsaturated silane compound as a side chain, and all resin components in the encapsulant composition A crosslinking agent containing 0.02 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass, and the total number of double bonds per 2000 carbons by infrared absorption spectroscopy is 1.8 or more. 3.3 selecting a sealing material composition that is 3 or less;
A sheeting step for melt-forming the encapsulant composition;
A cross-linking step of cross-linking the melt-formed encapsulant sheet,
In the crosslinking treatment, the encapsulant sheet made of the encapsulant composition has a total number of double bonds per 2000 carbon according to an infrared absorption spectrum method of 1.7 to 3.0. A method for producing a solar cell module sealing material sheet.

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