JP2012094845A - Sealing material for solar cell module and method for manufacturing solar cell module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material for a solar cell module which can improve light conversion efficiency of a solar cell element in comparison with EVA by imparting light scattering effect to a polyethylene-based resin, and to provide a method for manufacturing the same.SOLUTION: In the sealing material for a solar cell module mainly containing a polyethylene-based resin, the crystallization is adjusted so that the haze value of a test specimen as in examples measured by JIS K7136 at a thickness of 400 μm is 1 to 6%, and a spherulite size derived from the polyethylene-based resin exists in the range of 0.1 μm or more and 0.5 μm or less in average. Consequently, light scattering effect is enhanced by the spherulite portion, and a higher light conversion efficiency is obtained in comparison with EVA while having a haze value smaller than that of the conventional EVA.

Description

  The present invention relates to a solar cell module sealing material having high light conversion efficiency and a method for manufacturing a solar cell module using the solar cell module sealing material.

  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.

  Solar cell elements are often manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate. For this reason, the solar cell element is vulnerable to physical impact, and when the solar cell module is mounted outdoors, it is necessary to protect it from rain or the like. Moreover, since the electrical output generated by one solar cell element is small, it is necessary to connect a plurality of solar cell elements in series and parallel so that a practical electrical output can be taken out. For this reason, it is common practice to connect a plurality of solar cell elements and enclose them with a transparent substrate and a sealing material to produce a solar cell module. Generally, a solar cell module is manufactured by a lamination method or the like in which a transparent front substrate, a sealing material, a solar cell element, a sealing material, a back surface protection sheet, and the like are sequentially stacked, and these are vacuum-sucked and heat-pressed.

  As a sealing material used for a solar cell module, ethylene-vinyl acetate copolymer resin (EVA) is most commonly used from the viewpoints of workability, workability, manufacturing cost, etc. Yes. However, EVA resin has a tendency to gradually decompose with long-term use, and deteriorates inside the solar cell module to decrease its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. For this reason, the sealing material for solar cell modules which uses polyolefin-type resin, such as polyethylene, instead of EVA resin is proposed.

  For example, Patent Document 1 discloses a solar cell module in which a sealing material layer is composed of a resin film made of a resin composition containing a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof. A sealing material for a rubber is disclosed.

  On the other hand, in the solar cell module, it is desired to improve the light conversion efficiency as a module by concentrating incident light on the solar cell element as efficiently as possible. It has been studied to impart a light scattering effect). For example, in the following Patent Document 2, EVA (ethylene-vinyl acetate copolymer) sealing material contains a transparent filler having a refractive index different from that of EVA such as glass beads, and light reaches the solar cell element by diffuse reflection. Increasing the amount is being considered.

JP 2003-46105 A JP 2000-183381 A

  Generally, in a sealing material for a solar cell module mainly composed of a polyethylene resin, transparency and flexibility can be improved by reducing the density thereof. However, maintaining the transparency by reducing the density and having the light confinement function by appropriately reflecting and scattering incident sunlight are contradictory at first glance, especially in polyolefin systems. Not considered.

  Moreover, like patent document 2, the conventional technique is providing the light-diffusion effect by disperse | distributing the filler from which a refractive index differs with respect to sunlight as an external additive material. In this case, consideration of material design that achieves compatibility between chemical characteristics such as compatibility and optical characteristics such as refractive index adjustment is essential and very complicated, and in particular, an additive filler required for a solar cell module. Although it is necessary to clear long-term weather resistance etc., patent document 2 does not disclose or suggest such a point.

  The present invention has been made in view of the above situation, and substantially externally added while having good transparency and flexibility suitable for a solar cell module sealing material while using a polyethylene-based resin. It aims at providing the sealing material for solar cell modules which can provide a light-scattering function without a material, and its manufacturing method.

  As a result of intensive studies, the inventors of the present invention have adjusted the size of the spherulites of the low-density polyethylene resin, which is originally a crystalline resin, that is, the crystallinity, in other words, by adjusting the haze value, so that the incidence of sunlight As a result, it was found that the transparency and the light scattering property can be made compatible with each other, and the present invention has been completed. More specifically, the present invention provides the following.

(1) Contains mainly a polyethylene resin,
A sealing material for a solar cell module, wherein a haze value at a thickness of 400 μm of the following test sample measured according to JIS K7136 is 1% or more and 6% or less.
Test sample: Both surfaces of a sealing material (75 mm × 35 mm × 0.4 mm) are sandwiched between blue plate glasses (75 mm × 35 mm × 2.75 mm), and heat-bonded (vacuum drawing at 150 ° C. for 5 minutes, press 1.5 minutes, 100 kPa) And maintained at room temperature (25 ° C.) for 12 hours or longer to adjust the state.

(2) Contains mainly a polyethylene resin,
In the SEM cross-sectional observation, the polyethylene resin-derived spherulites are present in an average size of 0.1 μm or more and 0.5 μm or less.

  (3) The sealing material for solar cell modules according to (1) or (2), which does not substantially contain an inorganic filler.

(4) The polyethylene-based resin has a density of 0.900 g / cm ³ or less, and the MFR at 190 ° C. of the solar cell module sealing material is 0.1 g / 10 min or more and less than 1.0 g / 10 min ( The sealing material for solar cell modules in any one of 1) to (3).

(5) An uncrosslinked encapsulant sheet is obtained by melt-molding an encapsulant composition containing the polyethylene resin having a density of 0.900 g / cm ³ or less, a crosslinking agent, and a crosslinking aid. The solar cell module sealing material according to any one of (1) to (3), wherein the uncrosslinked sealing material sheet is subjected to a crosslinking treatment so that the gel fraction is 2% or more and 80% or less.

  (6) The solar cell module sealing material according to (5), wherein the crosslinking treatment is a crosslinking treatment by irradiation with ionizing radiation.

  (7) The sealing material for solar cell modules according to any one of (1) to (6), wherein the polyethylene resin is a metallocene linear low-density polyethylene.

  (8) The sealing material for solar cell modules according to any one of (1) to (7), wherein the refractive index is 1.40 or more and 1.60 or less.

(9) A solar cell module comprising at least a transparent front substrate, a front sealing material layer, and a solar cell element,
The solar cell module whose said front sealing material layer is the sealing material for solar cell modules in any one of (1) to (8).

  (10) The solar cell module according to (9), wherein the transparent front substrate is a glass substrate having a refractive index of 1.51 or more and 1.54 or less.

(11) A method for producing a sealing material for a solar cell module mainly containing a polyethylene resin,
Crystallization of the polyethylene resin is determined so that the haze value at a thickness of 400 μm of the following test sample measured by JIS K7136 is 1% or more and 6% or less, and / or in SEM cross-sectional observation, derived from the polyethylene resin The manufacturing method of the sealing material for solar cell modules provided with the crystallization adjustment process which adjusts crystallization of the said polyethylene-type resin so that the spherulite of this may exist with an average magnitude | size of 0.1 micrometer or more and 0.5 micrometer or less.
Test sample: Both surfaces of a sealing material (75 mm × 35 mm × 0.4 mm) are sandwiched between blue plate glasses (75 mm × 35 mm × 2.75 mm), and heat-bonded (vacuum drawing at 150 ° C. for 5 minutes, press 1.5 minutes, 100 kPa) And maintained at room temperature (25 ° C.) for 12 hours or longer to adjust the state.

  ADVANTAGE OF THE INVENTION According to this invention, while using polyethylene-type resin substantially independently, it can provide further light-scattering property, providing favorable transparency and a softness | flexibility suitable for the sealing material for solar cell modules. The sealing material for solar cell modules and its manufacturing method can be provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention. It is the table | surface which compared the total light transmittance of the sealing material for solar cell modules in an Example and a comparative example. It is the table | surface which compared the outdoor exposure evaluation of the solar cell module in Example 1 and Comparative Example 2. FIG. It is a SEM cross-sectional photograph of the sealing material for solar cell modules in an Example, and is a photograph of Example 1. It is a SEM cross-sectional photograph of the sealing material for solar cell modules in an Example, and is a photograph of the comparative example 1. FIG. It is a SEM cross-sectional photograph of the sealing material for solar cell modules in an Example, and is a photograph of the comparative example 2. FIG. It is the table | surface which compared the outdoor exposure evaluation of the solar cell module in Example 4 and Comparative Example 3. FIG.

<Sealant composition for solar cell module>
In the present invention, the polyethylene resin is crystallized so that the haze value at a thickness of 400 μm measured according to JIS K7136 is 1% or more and 6% or less for the test sample described in the examples, and / or SEM cross section. In the observation, the spherulite size derived from the polyethylene-based resin is adjusted so as to exist with an average size of 0.1 μm or more and 0.5 μm or less. As a result, the light scattering effect by the spherulite portion is enhanced, and the light conversion efficiency equal to or higher than EVA is obtained while the haze value is equal to or lower than the conventional EVA.

  Methods for controlling crystallinity include changing the base resin density, changing the base resin molecular weight, changing the base MFR, using a cross-linking agent, using a cross-linking aid, using a cross-linking step using heat, EB, etc., modularizing step It is possible to appropriately combine techniques such as changing the cooling conditions in FIG.

<Composition A>
As an example of obtaining the haze value and / or spherulite size within the above range, the composition A contains a polyethylene resin having a density of 0.900 g / cm ³ or less and a polymerization initiator as essential components. It is. Hereinafter, after explaining these essential components, other resins and other components will be explained.

[Polyethylene resin]
As a preferable base resin, low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less, preferably linear 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 to 0.890 g / cm ³ . is there. If it is this range, favorable transparency and heat resistance can be provided, maintaining sheet workability.

  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 which consists of a sealing material composition of this invention is arrange | positioned between a 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 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 sealing material and the base material is increased, and moisture intrusion between the sealing material and the base material can be suppressed.

  The melt mass flow rate (MFR) of the polyethylene resin needs to be 1.0 g / 10 min or more and 40 g / 10 min or less at 190 ° C., and preferably 2 g / 10 min or more and 40 g / 10 min or less. When the MFR is in the above range, the processability during film formation is excellent.

  “Polyethylene resin” includes not only ordinary polyethylene obtained by polymerizing ethylene but also resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin, Resins obtained by copolymerizing a plurality of different compounds having a saturated bond, modified resins obtained by grafting different chemical species to these resins, and the like are included.

  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, adhesion between a sealing material and a member such as a transparent front substrate or a solar cell element can be obtained.

  The silane copolymer is described in, for example, JP-A-2003-46105. By using the copolymer as a component of the encapsulant composition of the solar cell module, it is excellent in strength, durability, etc., and 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. Using a desired reaction vessel, for example, pressure 500-4000 Kg / cm ² position, preferably, 1000-4000 Kg / cm ² position, temperature 100-400 ° C., preferably 150-350 ° C. 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 condensed product 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 the 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 may 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. Kill.

  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 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.

The content of the polyethylene resin having a density of 0.900 g / cm ³ or less contained in the composition is preferably 10% by mass to 99% by mass, more preferably 50% by mass to 99% in the composition. Or less, more preferably 90 to 99% by mass. In other words, other resins may be contained within this range. For example, other polyethylene resins exceeding 0.900 g / cm ³ can be exemplified. These may be used, for example, as an additive resin, and can be used for masterbatching other components described later.

[Polymerization initiator]
Unlike the case where the conventional crosslinking treatment of the solar cell module sealing material composition is performed, the content of the polymerization initiator with respect to the solar cell module sealing material composition is the general crosslinking treatment. A polymerization initiator is used so that the content in a specific range is smaller than in the case of (a weak crosslinking treatment). Content of a polymerization initiator is 0.02 mass% or more and less than 0.5 mass% in the sealing material composition for solar cell modules, Preferably an upper limit is 0.2 mass% or less, More preferably, it is 0.00. 1% by mass or less. Within this range, most of the cross-linking agent is consumed for increasing the molecular weight of the resin, and the formation of the network structure can be suppressed to a small amount, so that the crystallinity can be lowered moderately and the moldability can be maintained after film formation. it can. If it is less than this range, the weak crosslinking of the polyethylene resin does not proceed and the heat resistance is insufficient. On the other hand, if it exceeds this range, the film-forming property is lowered due to the generation of gel during molding, and the transparency is also lowered.

  A well-known thing can be used for a polymerization initiator and 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 t-- Tylhexanoate, t-butyl peroxypivalate, t-butyl peroxyoctoate, t-butyl peroxyisopropyl carbonate, t-butyl peroxybenzoate, di-t-butyl peroxyphthalate, 2,5-dimethyl Peroxyesters such as -2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3, t-butylperoxy-2-ethylhexyl carbonate; Ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; organic peroxides such as t-amyl-peroxy-2-ethylhexyl carbonate, peroxycarbonates such as t-butylperoxy 2-ethylhexyl carbonate, or Azo Examples include azo compounds such as sisobutyronitrile and azobis (2,4-dimethylvaleronitrile), silanol condensation catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctate, dioctyltin dilaurate, and dicumyl peroxide. Can do.

  Of the above, t-butylperoxy 2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and the like can be preferably used. Since the active oxygen content is as high as 5% or more, and the one-minute half-life temperature of the polymerization initiator is 160 to 190 ° C., it is consumed at the time of molding and can remain after molding to suppress the progress of excessive post-crosslinking. preferable. A one-minute half-life temperature of less than 160 ° C. is not preferable because it is difficult to allow the crosslinking reaction to proceed after sufficiently dispersing the polymerization initiator during molding. As is clear from Example 3 described later, a polymerization initiator is not necessarily required in the present invention.

[Crosslinking aid]
It is preferred that substantially no crosslinking aid is used. Here, the crosslinking assistant is, for example, a polyfunctional vinyl monomer and / or a polyfunctional epoxy monomer, and specifically, triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fuma. Polyallyl compounds such as rate and diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6 -Poly (meth) acryloxy compounds such as hexanediol diacrylate and 1,9-nonanediol diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycol Epoxy compounds such as 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexane dimethanol diglycidyl ether, trimethylolpropane polyglycidyl ether and the like containing two or more diyl ethers and epoxy groups Can be mentioned.

  Note that the fact that substantially no crosslinking aid is used means that an amount that does not exhibit a crosslinking effect is within the scope of the present invention even if it is contained in an impurity, and the amount is, for example, in the composition. Is less than 0.01% by mass.

<Composition B>
As another example of obtaining a haze value and / or a spherulite size within the above range, as the composition B, a polyethylene resin having a density of 0.900 g / cm ³ or less, a polymerization initiator (crosslinking agent), and a crosslinking It is a composition containing an auxiliary agent as an essential component. In this case, an uncrosslinked sealant sheet is obtained by melt molding without being crosslinked. Thereafter, a crosslinking treatment is performed to obtain a sealant sheet.

  The same polyethylene resin can be used, but the melt mass flow rate (MFR) is MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS-K6922-2. The measurement value under the measurement conditions is referred to as MFR) is preferably 0.5 g / 10 min or more and 40 g / 10 min or less, more preferably 6 g / 10 min or more and 40 g / 10 min or less. Even if the MFR of the base polyethylene is high, the fluidity can be suppressed in the subsequent crosslinking step. For this reason, even if it is high MFR like the said range, it can be used conveniently.

  As the polymerization initiator, the same ones as described above can be used. However, in the case of the composition B, a crosslinking agent having a 1-minute half-life temperature of 185 ° C. or higher can be freely selected. In addition, by expanding the selection range in this way, there is an advantage that the temperature at which molding can be performed without cross-linking is improved and the productivity is improved.

  When the crosslinking treatment is a general heat treatment, the content of the polymerization initiator is 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass in total of all resin components of the sealing material. The content is preferably in a range of 0.5 parts by mass or more and 1.5 parts by mass or less. By adding 0.5 parts by mass or more of the polymerization initiator, sufficient heat resistance can be imparted to the polyethylene resin used for the sealing material. When the content of the polymerization initiator is less than 0.5 parts by mass, the heat durability is not sufficiently improved. On the other hand, when the content of the polymerization initiator exceeds 1.5 parts by mass, crosslinking in the crosslinking step is performed. This is not preferable because the progress of the process becomes excessive, and the followability to the unevenness of the other members at the time of modularization becomes insufficient.

  In the case where the crosslinking treatment is a crosslinking treatment by irradiation with ionizing radiation, it has been conventionally considered that a polymerization initiator is unnecessary. However, the sealing material composition used in the present invention contains a small amount of a polymerization initiator even in that case. This makes it possible to improve the heat resistance by ionizing radiation and maintain transparency. Although the action of the polymerization initiator in the crosslinking treatment by irradiation with ionizing radiation is not clear, the ionizing radiation has strong energy, so that the crosslinking proceeds. However, the crystals that cause HAZE do not loosen unless the temperature rises above a certain temperature. It is estimated that this is because it remains. In this case, the addition amount of the polymerization initiator to the encapsulant composition is preferably 0.2 parts by mass or more with respect to 100 parts by mass in total of all resin components of the encapsulant. By setting the addition amount of the polymerization initiator to the sealing material composition within this range, in addition to heat resistance and adhesion, a sealing material that is particularly excellent in transparency can be obtained. In this case, if the content of the polymerization initiator is less than 0.2 parts by mass, the effect of improving the transparency is insufficient, but unlike the case where the crosslinking treatment is a general heat treatment, The content may be less than 0.5 parts by mass.

  As the crosslinking aid, those described above can be used, and the content of the crosslinking aid is preferably 0.01% by mass to 3% by mass in the composition, more preferably 0.05% by mass to 2%. The range is 0.0 mass%. Within this range, an appropriate crosslinking reaction can be promoted, and the gel fraction of the crosslinked encapsulant can be 2% or more and 80% or less. It is preferable to set the gel fraction to 2% or more because the effect of suppressing flow by crosslinking before modularization can be obtained. In addition, by setting the gel fraction to 80% or less, it is possible to obtain more flexibility than EVA in a low temperature range from -50 ° C. to 0 ° C. while having the same degree of transparency as conventional EVA. preferable.

[Other components common to compositions A and B]
The solar cell module sealing material composition may further contain other components as long as the effects of the present invention are not impaired. For example, a weather-resistant masterbatch, a light stabilizer, an ultraviolet absorber, and a heat stabilizer for imparting weather resistance to a solar cell module encapsulant produced from the solar cell module encapsulant composition of the present invention Etc. are exemplified. These contents vary depending on the particle shape, density, and the like, but are preferably in the range of 0.001 to 5 mass% in the solar cell module encapsulant composition. By including these additives, it is possible to impart a long-term stable mechanical strength, an effect of preventing yellowing, cracking, and the like to the encapsulant composition for solar cell modules.

  The weather-resistant masterbatch is a dispersion of a light stabilizer, a UV absorber, a heat stabilizer, the above-mentioned antioxidant, etc., in a resin such as polyethylene, and this is a sealing material composition for a solar cell module. By adding to, favorable weather resistance can be imparted to the solar cell module sealing material. 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.

  In addition to the above, the other components used in the solar cell module encapsulant composition of the present invention include an adhesion improver such as a silane coupling agent, a nucleating agent, a dispersant, a leveling agent, a plasticizer, A foaming agent, a flame retardant, etc. can be mentioned.

  In addition, in this invention, it is preferable not to contain an inorganic type filler substantially. This is because the inorganic filler causes optical scattering and affects the light scattering property of the sealing material. Here, substantially containing no inorganic filler means that the haze value at a thickness of 400 μm measured according to JIS K7136 is 1% or more and 6% or less for the test samples described in the Examples, and / or In SEM cross-sectional observation, it means that the filler may be present if the spherulite size derived from the polyethylene-based resin is within a range in which the average size is 0.1 μm or more and 0.5 μm or less. Specifically, the proportion of the inorganic filler in the solar cell module sealing material composition is preferably 5% by mass or less.

<Sealant for solar cell module>

  The solar cell module encapsulant (hereinafter also simply referred to as “encapsulant sheet”) is formed into a sheet or film by molding the above solar cell module encapsulant composition by a conventionally known method. Is. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  In the case of the composition A, 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. Done. However, in order to promote a weak crosslinking reaction during molding, the molding temperature is preferably the melting point of the polyethylene resin + 50 ° C. or higher. Specifically, a high temperature of 150 to 250 ° C. is preferable, and a range of 190 to 230 ° C. is more preferable. Thus, in this invention, since the addition of a polymerization initiator is a small amount, although MFR falls, the grade of the fall is small. For this reason, weak crosslinking can be advanced during melt molding. And even if it is a small amount of polymerization initiators and there is substantially no crosslinking aid, the weak crosslinking of the polyethylene resin proceeds. Since the molding temperature is equal to or higher than the half-life temperature of 1 minute of the polymerization initiator, the polymerization initiator hardly remains after the molding. For this reason, the weak crosslinking ends at this molding stage.

  In this way, the solar cell module encapsulant that has been weakly cross-linked has a sufficient film-forming property in terms of its physical properties, i) maintaining low density, and ii) improving heat resistance. Iii) The haze value is reduced.

Regarding i), the density of the solar cell module encapsulant of the present invention does not increase at 0.900 g / cm ³ or less, which is substantially equal to the density of the raw material polyethylene resin, and the density of the resin composition before and after melt molding. The difference is within 0.05 g / cm ³ . For this reason, transparency is maintained.

On the other hand, ii) the heat resistance is such that the MFR at 190 ° C. is 0.1 g / 10 min or more and less than 1.0 g / 10 min, and preferably the MFR difference at 190 ° C. of the resin composition before and after melt molding is 1.0 g / 10 min. Since it is 10.0 g / 10min or less, the heat resistance is improved while it is within the range of MFR that can be molded. This sealing material for solar cell modules has a gel fraction of 25% or less, preferably 10% or less, and more preferably 1% or less including zero. In addition, the gel fraction here is a value obtained by the following method.
Gel fraction (%): After crosslinking, 1 g of the sealing material is weighed and placed in an 80 mesh wire mesh bag. Next, a sample with the wire mesh is put into a Soxhlet extractor, and xylene is refluxed at the boiling point. After 10 hours of continuous extraction, the sample was taken out together with the wire mesh, weighed after drying, and compared with the mass before and after extraction to measure the mass% of the remaining insoluble matter, which was taken as the gel fraction.

  The decrease in haze value of iii) is due to weak crosslinking, as shown in a comparison between Example 1 (with a crosslinking agent) and Example 3 (without a crosslinking agent) described later. It is presumed that the molecular orientation, that is, crystallization is suppressed by restraining, and the haze value is lowered.

  In the case of the composition B, the melt molding is performed by molding methods usually used in ordinary thermoplastic resins, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. 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. In the manufacturing method of the solar cell module encapsulant of the present invention, as described above, since a crosslinking agent having a half-life temperature higher than that of the conventional one can be used, the molding temperature is set higher than before. By setting, it is possible to reduce the load applied to the extruder, increase the extrusion amount of the sealing material composition, and increase the productivity.

[Crosslinking process]
In the composition B, after that, the crosslinking treatment step of crosslinking the uncrosslinked sealing material after the sheeting step is integrated with the other member after the sheeting step is completed. Performed before the start of the solar cell module integration step. By this cross-linking step, a sealing material having a gel fraction of 2% or more and 80% or less is obtained. The cross-linking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line.

  The method for the crosslinking treatment in the crosslinking step is not particularly limited, but is preferably a crosslinking treatment by heat treatment, more preferably a crosslinking treatment by irradiation with ionizing radiation. A sealing material sheet having preferable physical properties can be produced by any cross-linking treatment, but as shown in the following examples, the cross-linking treatment is performed by cross-linking treatment by irradiation with ionizing radiation. In heat resistance, it can be set as a more preferable sealing material sheet.

  When the cross-linking treatment in the cross-linking step is a heat treatment, the individual cross-linking conditions are not particularly limited, and are appropriately set within the range of general cross-linking treatment conditions so as to obtain the above gel fraction as a total treatment result. do it. In addition, when the crosslinking treatment is a heat treatment, it may also serve as an annealing treatment.

  Even in the case where the crosslinking treatment is a crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited, and may be appropriately set so as to obtain the above gel fraction as a total treatment result. Specifically, it can be performed by ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, etc. Among them, it is preferable to use an electron beam. The acceleration voltage in electron beam irradiation is determined by the thickness of the sheet that is the object to be irradiated, and the thicker the sheet, the larger the acceleration voltage is required. For example, a 0.5 mm-thick sheet is irradiated with 100 kV or more, preferably 200 kV or more. If the acceleration voltage is lower than this, the crosslinking is not sufficiently performed. The irradiation dose is in the range of 10 kGy to 1000 kGy, preferably 10 to 300 kGy. When the irradiation dose is less than 10 kGy, sufficient crosslinking is not performed, and when it exceeds 1000 kGy, there is a concern about deformation or coloring of the sheet due to generated heat. In addition, you may irradiate from both sides. Irradiation may be in an air atmosphere or a nitrogen atmosphere.

  By passing through the cross-linking step, the gel fraction of the encapsulant becomes 2% or more and 80% or less, and a crosslinked encapsulant is obtained. The gel fraction is preferably 2% or more and 80% or less, and more preferably 30% or more and 80% or less. If the gel fraction is less than 2%, the effect of suppressing the flow by the crosslinking step before the modularization step is not exhibited, and the sealing material composition flows in the vacuum heating laminate, making it difficult to keep the film thickness 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 by making a gel fraction 30% or more. The gel fraction (%) is a value obtained by the method of an example described later. The heat shrinkage is preferably 45% or less, more preferably 30% or less, and most preferably 20% or less.

<Haze value>
The sealing material for solar cell modules of the present invention has a haze value of 1% or more and 6% or less, preferably 1% or more and 5% or less at a thickness of 400 μm as measured according to JIS K7136 for the test samples described in the examples. Thereby, both light transmittance and light scattering can be achieved, the amount of light taken into the element can be improved, and the power generation efficiency of the module can be improved. When the haze value is less than 2%, it is transparent, but the crystallization is insufficient and the light scattering effect is small. On the other hand, if the haze value exceeds 6%, the light scattering effect due to crystallization is so great that the amount of light reaching the device is reduced, which is not preferable.

<Spherulite size>
In the sealing material for a solar cell module of the present invention, the spherulites derived from the polyethylene resin exist in an average size of 0.1 μm or more and 0.5 μm or less in SEM cross-sectional observation. Thereby, both light transmittance and light scattering can be achieved, the amount of light taken into the element can be improved, and the power generation efficiency of the module can be improved. If the spherulite size is less than 0.1 μm, it is transparent, but the crystallization is insufficient and the light scattering effect is small. On the other hand, if the spherulite size exceeds 0.5 μm, the light scattering effect due to crystallization is too large and the amount of light reaching the device is reduced, which is not preferable.

  Thus, in the present invention, by using the crystallinity of the polyethylene resin, by adjusting the crystallization within the above range, the light scattering effect is imparted without using the transparent filler as in Patent Document 2. Has been successful. Conventionally, as represented by EVA, even a polyethylene resin has been considered to be more advantageous in terms of light reaching the device, but in the present invention, light scattering is achieved by controlling the crystal of polyethylene. The present invention is characterized in that it has been found that an effect can be obtained.

<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 solar cell module sealing material (hereinafter also simply referred to as “sealing material sheet”) for at least the front sealing material layer 3.

  The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of 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. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method.

  Moreover, 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. The back sealing material layer 5 is melt-laminated, the solar cell element 4 is sanded with the front sealing material layer 3 and the back sealing material layer 5, and then the transparent front substrate 2 and the back surface protection 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.

  Here, in the solar cell module of the present invention, when the light is incident, the incident light is scattered by the front sealing material layer, so that the incident light efficiency to the solar cell element 4 is improved. Moreover, since the reflected light from the back surface protective sheet 6 is scattered again by the front sealing material layer 3, the incident light efficiency to the solar cell element 4 is also improved here. The back sealing material layer 5 may be the same as the front sealing material layer 3 or may contain a white pigment or the like to promote the reflection of incident light.

  At this time, the transparent front substrate 2 is a glass substrate having a refractive index of 1.51 to 1.54 (typical refractive index is 1.51), and the refractive index of the front sealing material layer 3 is 1.40. If it is 1.60 or less, preferably 1.45 or more and 1.55 or less, it is preferable because refraction at the interface between the glass and the front sealing material layer 3 is small and the efficiency of light capture is improved.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4, and the back surface protective sheet 6 that 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. In addition, the sealing material sheet | seat of this invention is applicable not only to a single crystal type but to all other solar cell modules.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
[Test Example 1]
<Manufacture of sealing material for solar cell module>
[Polyethylene resin of Examples 1 to 3]
Silane modified transparent resin: vinyl trimethoxy with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. 2 parts by mass of silane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) are mixed, melted and kneaded at 200 ° C., density 0.884 g / cm ³ , MFR at 190 ° C. A silane-modified transparent resin having a weight of 1.8 g / 10 min was obtained.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and hindered amine light stabilizer 5 with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ Mass parts and 0.5 parts by mass of a phosphorous heat stabilizer were mixed, melted, processed, and pelletized to obtain a master batch.
Polymerization Initiator Compound Resin 1: 2,5-Dimethyl-2,5-Di for 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and an MFR of 190 g at 3.1 g / 10 min. Compound pellets were obtained by impregnating 0.1 part by mass of (t-butylperoxy) hexane.
Polymerization Initiator Compound Resin 2: 2,5-Dimethyl-2,5-Di for 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.4 g / 10 min. Compound pellets were obtained by impregnating 0.1 part by mass of (t-butylperoxy) hexane.

[Example 1]
20 parts by mass of the silane-modified transparent resin, 5 parts by mass of the weather resistant masterbatch, and 80 parts by mass of the polymerization initiator compound resin 1 are mixed, using a φ30 mm extruder, a film molding machine having a 200 mm width T-die, The sealing material for solar cell modules of Example 1 having an extrusion temperature of 210 ° C. and a take-up speed of 1.1 m / min and a total thickness of 400 μm was produced.
[Example 2]
A solar cell module sealing material of Example 2 was produced in the same manner as in Example 1 except that the polymerization initiator compound resin 1 was replaced with the polymerization initiator compound resin 2.
[Example 3]
Example 1 The same manner as in Example 1 except that the polymerization initiator compound resin 1 was replaced with a metallocene linear low density polyethylene having a density of 0.880 g / cm ³ and an MFR at 190 ° C. of 3.1 g / 10 min. No. 4 solar cell module encapsulant was produced (without a crosslinking agent).

[Polyethylene resins of Examples 4 to 8]
LLDPE (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 an MFR of 8 g / 10 min.
LLDPE2 (base resin M2): polyethylene resin (LLDPE): 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.
Silane-modified polyethylene resin (base resin S1): 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) with respect to 98 parts by mass of the base resin M1. A silane-modified polyethylene resin having a density of 0.884 g / cm ³ and an MFR of 6 g / 10 min.
Cross-linking agent: t-butylperoxy-2-ethylhexyl carbonate (manufactured by Arkema Yoshitomi Co., Ltd., trade name Luperox TBEC)
Crosslinking aid: triallyl isocyanurate (manufactured by Statomer, trade name SR533)
UV absorber: manufactured by Chemipro Kasei Co., Ltd., trade name KEMISORB12
Weather resistance stabilizer: Ciba Japan Co., Ltd., trade name Tinuvin 770
Antioxidant: Ciba Japan Co., Ltd., trade name Irganox 1076

[Example 4]
35 parts by mass of M1, 40 parts by mass of M2, 25 parts by mass of S1, 1.2 parts by mass of a crosslinking agent, 0.8 parts by mass of a crosslinking aid, 0.25 parts by mass of a UV absorber, 0.2 of a weather resistance stabilizer Part by mass and 0.05 part by mass of an antioxidant were mixed and melted, and formed into a film having a thickness of 400 μm by a conventional T-die method to obtain an uncrosslinked sealing material sheet. The film forming temperature was 90 ° C. or higher and lower than 100 ° C. Then, the crosslinking process of 200 degreeC x 2 minutes was performed (gel fraction 46.7%), and the sealing material sheet of Example 4 was obtained.

[Example 5]
A sealing material sheet of Example 5 was obtained in the same manner as in Example 4 except that 300 kGy electron beam was irradiated instead of heating as the crosslinking treatment (gel fraction 33.0%).

[Example 6]
After heat-pressing the sealing material sheet of Example 1 under the conditions of Evaluation Example 1 to be described later, it was cooled to room temperature on a water-cooled 5 ° C. iron plate to obtain a test sample of the sealing material sheet of Example 6. .

[Example 7]
The sealing material sheet of Example 1 was subjected to thermocompression bonding under the conditions of Evaluation Example 1 described later, and then cooled to room temperature at 10 ° C./min to obtain a test sample of the sealing material sheet of Example 7.

[Example 8]
The sealing material sheet of Example 1 was subjected to thermocompression bonding under the conditions of Evaluation Example 1 described later, and then cooled to room temperature at 5 ° C./min to obtain a test sample of the sealing material sheet of Example 8.

[Comparative Example 1]
Silane-modified transparent resin: 98 parts by mass of a metallocene linear low density polyethylene (hereinafter referred to as M-LLDPE) having a density of 0.898 g / cm 3 and a melt mass flow rate at 190 ° C. of 2 g / 10 min. On the other hand, 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) were mixed and melted and kneaded at 200 ° C. to obtain a silane-modified transparent resin. .
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and 5 parts by mass of hindered amine light stabilizer with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene with a density of 0.920 g / cm3 Part and 0.5 parts by mass of a phosphorous heat stabilizer were mixed, melted, processed, and pelletized to obtain a master batch.
20 parts by mass of the above silane-modified transparent resin, 5 parts by mass of a weather-resistant masterbatch, and 80 parts by mass of a metallocene linear low density polyethylene having a density of 0.905 g / cm 3 as an additive polyethylene are mixed, φ150 mm extruder, 1000 mm A sealing material for a solar cell module for a surface having a total thickness of 400 μm was produced at an extrusion temperature of 230 ° C. and a take-off speed of 2.3 m / min using a film forming machine having a T-die having a width.

[Comparative Example 2]
The EVA filler of Comparative Example 2 is composed of 1.5 parts by mass of a crosslinking agent (Lupersol 101) and 100 parts by mass of EVA (vinyl acetate content 28%, manufactured by Mitsui DuPont Polychemical, trade name EVAFLEX / EV250 grade). What mix | blended 0.2 mass part of inhibitor (NAUGARD-P) and UV absorber (0.1 mass part of Tinuvin 7709 and 0.3 mass part of Cyasorb UV-531) was used. A film was formed to a thickness of 400 μm by a conventional T-die method to obtain an uncrosslinked filler. The film forming temperature was 90 ° C. to 100 ° C.
[Comparative Example 3]
The sealing material sheet of Example 1 was subjected to thermocompression bonding under the conditions of Evaluation Example 1 described later, and then cooled to room temperature at 1 ° C./min to obtain a test sample of the sealing material sheet of Comparative Example 3.

<Evaluation Example 1>
About an Example and a comparative example, the total light transmittance (JIS K7361) and the haze value (JIS K7136) were measured in Murakami Color Research Laboratory, Haze and transmittance system HM150. The test sample is sandwiched between both sides of a sealing material (75 mm × 35 mm × 0.4 mm) with blue plate glass (75 mm × 35 mm × 2.75 mm), and heat compression (vacuum drawing at 150 ° C. for 5 minutes, press 1.5 minutes, 100 kPa) And maintained at room temperature (25 ° C.) for 12 hours or longer to adjust the state. In addition, PV characteristics are obtained by laminating the above sealing material on the cell in a state where the other than the cell portion of the MOTECH single crystal cell (AS125-150R) is sealed with aluminum to prevent the light from wrapping around. It is Isc value (short-circuit current, unit mA) measured under the conditions of a cell back surface temperature of 25 ° C. and an illuminance of 100 mW / cm 2 using a company-made EWXS-300S-50). The results are shown in Table 1 below. The refractive index was 1.49 in all cases. Moreover, the power generation efficiency in the table is a comparison of the total power generation amount in Evaluation Example 3-2. When Comparative Example 2 is set to 100 (−), 100.1 or more is given as ◯, and 100.4 or more is given as ◎. And less than 100 is evaluated as x.

  From Table 1, although the haze value of an Example is 1% or more and 6% or less and is in the range of this invention, the haze value of Comparative Examples 1 and 3 exceeds the upper limit of the range of this invention. Moreover, the haze value of EVA of Comparative Example 2 is less than 1%.

  Moreover, in the PV characteristics, although the haze value of Example 1 is higher than that of EVA Comparative Example 2, the short-circuit current maintenance rate is equal to or higher than that of EVA, and the power generation efficiency is improved by the light scattering effect. I understand that it helps.

<Evaluation Example 2>
About the sealing material of Example 1 and the EVA sealing material of the comparative example 2, it measured by transmittance | permeability measurement T% (apparatus name UV-2550, Shimadzu Corporation Corp. make) by a spectrophotometer. The result is shown in FIG. From FIG. 2, in the vicinity of a wavelength of 400 to 550 nm, about 1% EVA has a higher transmittance, and a result confirming the difference in the haze value was obtained.

<Evaluation Example 3-1>
For the sealing material of Example 1 and the EVA sealing material of Comparative Example 2, outdoor exposure evaluation by a direct exposure test method (JIS Z23801 01) was performed using a data logger: Memory Hilogger 8430, manufactured by Hioki Electric Co., Ltd. : Shunt HS-01 (50A) Measured under the conditions of 45 ° southward installation by Hioki Electric Co., Ltd. Q-Cells polycrystal cell (Q6LTT3) is connected in series with 4 cells with 2 mm wide lead wires (manufactured by Hitachi Cable Ltd.), and has a configuration of glass / sealing material / cell / sealing material / back sheet. Measurements were made using a modularized one. The result is shown in FIG. From FIG. 3, it can be understood that Example 1 contributes to improvement in power generation efficiency due to the light scattering effect even though the haze value is higher than that of EVA Comparative Example 2, even though the generated power is large.

<Evaluation Example 3-2>
FIG. 7 shows the results of a test similar to the evaluation example 3-1 described above for the sealing material of Example 4 and the EVA sealing material of Comparative Example 2 on a different occasion from Evaluation Example 3-1. Show. From FIG. 7, the crosslinked Example 4 has a larger generated power than the EVA Comparative Example 3 in spite of the higher haze value, and in particular the power generation by the light scattering effect in the evening when the incident angle to the module is smaller. It can be understood that there is a difference in efficiency improvement. In addition, as a result of comparing the total power generation amount per day, it was 2959 W in Example 4 compared to 2878 W in Comparative Example 2.

<Evaluation Example 4>
About the sealing material of Example 1, the sealing material of the comparative example 1, and the EVA sealing material of the comparative example 2, the cross-sectional SEM photograph was measured in apparatus name S-4800 and Hitachi High-Technologies Corporation SEM. . The results are shown in FIGS. 4 is an SEM photograph of Example 1, FIG. 5 is Comparative Example 1, and FIG. 6 is Comparative Example 2. In the drawing, the scale on the lower right is 0.1 μm on one scale (1 μm on all 10 scales).

  The circles enclosed in FIG. 4 are the size of spherulites. In the case of Example 1, spherulites of 0.1 μm to 0.5 μm are obtained, and the light scattering effect is generated by these spherulites. On the other hand, in Comparative Example 1, further crystal growth was observed and a fibrous crystal structure having a size of 0.5 μm or more was observed. In Comparative Example 2, no crystal structure is observed.

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 (11)

Contains mainly polyethylene resin,
A sealing material for a solar cell module, wherein a haze value at a thickness of 400 μm of the following test sample measured according to JIS K7136 is 1% or more and 6% or less.
Test sample: Both surfaces of a sealing material (75 mm × 35 mm × 0.4 mm) are sandwiched between blue plate glasses (75 mm × 35 mm × 2.75 mm), and heat-bonded (vacuum drawing at 150 ° C. for 5 minutes, press 1.5 minutes, 100 kPa) And maintained at room temperature (25 ° C.) for 12 hours or longer to adjust the state. Contains mainly polyethylene resin,
In the SEM cross-sectional observation, the polyethylene resin-derived spherulites are present in an average size of 0.1 μm or more and 0.5 μm or less.   The sealing material for solar cell modules of Claim 1 or 2 which does not contain an inorganic type filler substantially. The polyethylene-based resin has a density of 0.900 g / cm ³ or less, and the MFR at 190 ° C. of the solar cell module sealing material is 0.1 g / 10 min or more and less than 1.0 g / 10 min. 3. The sealing material for solar cell modules in any one of 3. A non-crosslinked sealing material sheet is obtained by melt-molding a sealing material composition containing the polyethylene resin having a density of 0.900 g / cm ³ or less, a crosslinking agent, and a crosslinking aid, The encapsulant for solar cell module according to any one of claims 1 to 3, wherein the encapsulant sheet for crosslinking is subjected to a crosslinking treatment so that the gel fraction is 2% or more and 80% or less.   The solar cell module sealing material according to claim 5, wherein the crosslinking treatment is a crosslinking treatment by irradiation with ionizing radiation.   The solar cell module sealing material according to any one of claims 1 to 6, wherein the polyethylene-based resin is a metallocene-based linear low-density polyethylene.   The sealing material for solar cell modules according to any one of claims 1 to 7, wherein a refractive index is 1.40 or more and 1.60 or less. A solar cell module comprising at least a transparent front substrate, a front sealing material layer, and a solar cell element,
The solar cell module whose said front sealing material layer is the sealing material for solar cell modules in any one of Claim 1-8.   The solar cell module according to claim 9, wherein the transparent front substrate is a glass substrate having a refractive index of 1.51 or more and 1.54 or less. A method for producing a sealing material for a solar cell module mainly containing a polyethylene resin,
Crystallization of the polyethylene resin is determined so that the haze value at a thickness of 400 μm of the following test sample measured by JIS K7136 is 1% or more and 6% or less, and / or in SEM cross-sectional observation, derived from the polyethylene resin The manufacturing method of the sealing material for solar cell modules provided with the crystallization adjustment process which adjusts crystallization of the said polyethylene-type resin so that the spherulite of this may exist with an average magnitude | size of 0.1 micrometer or more and 0.5 micrometer or less.
Test sample: Both surfaces of a sealing material (75 mm × 35 mm × 0.4 mm) are sandwiched between blue plate glasses (75 mm × 35 mm × 2.75 mm), and heat-bonded (vacuum drawing at 150 ° C. for 5 minutes, press 1.5 minutes, 100 kPa) And maintained at room temperature (25 ° C.) for 12 hours or longer to adjust the state.