JP6036117B2 - Manufacturing method of sealing material sheet - Google Patents

Description

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

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

  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, a solar cell module is usually manufactured by connecting a plurality of solar cell elements and enclosing them with a transparent substrate and a sealing material sheet. Generally, a solar cell module is manufactured by a lamination method or the like in which a transparent front substrate, a sealing material sheet, a solar cell element, a sealing material sheet, a back surface protection sheet, and the like are sequentially laminated, and these are vacuum-sucked and heat-pressed. .

  As a sealing material sheet 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. ing. 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 sheet for solar cell modules which uses polyolefin-type resin, such as polyethylene, instead of EVA resin is proposed.

  For example, in Patent Document 1, due to the presence of a predetermined amount of a crosslinking agent in the composition, the MFR of the encapsulant sheet after film formation is lower than that of the raw material polyethylene, thereby being excellent in heat resistance while being transparent. An encapsulant sheet is disclosed.

WO2011 / 152314 International Publication Pamphlet

  However, since the improvement in transparency directly affects the power generation efficiency of the solar cell module, it has been desired to further improve the transparency while imparting heat resistance to the polyethylene resin sealing material sheet.

  The present invention has been made in view of the above situation, and has further transparency and thermal fluidity while having heat resistance suitable for a sealing material sheet for a solar cell module while using a polyethylene-based resin. It is an object of the present invention to provide a sealing material sheet and a method for producing the same that can improve (concave and convex followability).

  The present inventors pay attention to the fact that the polyethylene resin is a crystalline resin in the first place, and the cause of the decrease in transparency of the polyethylene resin. It has been found that by using a polyethylene resin in combination, the crystallinity can be lowered and the transparency and thermal fluidity can be greatly improved, and the present invention has been completed. More specifically, the present invention provides the following.

(1) The following polyethylene-based resin (A) and polyethylene-based resin (B) are contained in a mass ratio of 5:95 to 50:50, and 0.02% by mass or more and 0.0. The manufacturing method of the sealing material sheet for solar cell modules which melt-molds the resin composition containing a crosslinking agent less than 5 mass%.
Polyethylene resin (A): MFR at a density of 0.900 g / cm ³ or less, measured at 190 ° C. according to JIS K7210, and a load of 2.16 kg is 0.1 g / 10 min or more and less than 1.0 g / 10 min.
Polyethylene resin (B): MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS K7210 at a density of 0.900 g / cm ³ or less and 1 g / 10 min or more and less than 40 g / 10 min.

(2) The polystyrene-based weight average molecular weight of the polyethylene resin (A) is 120,000 to 300,000,
The manufacturing method of the sealing material sheet | seat of (1) description whose weight average molecular weight of polystyrene conversion of the said polyethylene-type resin (B) is 50,000 or more and 100,000 or less.

(3) The polyethylene-based resin (A) includes a raw material polyethylene-based resin having a density of 0.900 g / cm ³ or less, a raw material crosslinking agent contained in the composition in an amount of 0.02% by mass or more and less than 0.5% by mass, The manufacturing method of the sealing material sheet as described in (1) or (2) which is obtained by melt-molding the resin composition containing this.

(4) The raw material polyethylene resin and the polyethylene resin (B) are the same resin,
The method for producing a sealing material sheet according to (3), wherein the raw material crosslinking agent and the crosslinking agent are the same crosslinking agent.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the sealing material sheet | seat for solar cell modules which can improve transparency and heat fluidity (unevenness | corrugation followability) significantly using a polyethylene-type resin is provided. can do.

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

<Sealing material sheet composition>
The encapsulant sheet composition for producing the encapsulant sheet for the solar cell module of the present invention includes, in the composition, a polyethylene resin (A), a polyethylene resin (B), a crosslinking agent, Contains at a predetermined ratio.

[Polyethylene resin (B)]
Polyethylene resin as the base resin (B) is preferably a density of 0.900 g / cm ³ or less of low density or polyethylene (LDPE), more preferably a density of 0.900 g / cm ³ or less 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.

  In the present invention, it is preferable to use a metallocene linear low density polyethylene. Metallocene linear low density polyethylene is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and a uniform distribution of comonomer. For this reason, molecular weight distribution is narrow and it is possible to make it the above ultra-low density. In addition, since the crystallinity distribution is narrow and the crystal sizes are uniform, not only a large crystal size does not exist, but also the crystallinity itself is low due to the low density. For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, even if the sealing material sheet for solar cell modules which consists of a sealing material sheet 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 or more and 8 or less carbon atoms, the solar cell module sealing material sheet can be provided with good flexibility and good strength. As a result, the adhesiveness between the solar cell module sealing material sheet and the base material is increased, and the intrusion of moisture between the solar cell module sealing material sheet and the base material can be suppressed.

  The melt mass flow rate (MFR) of the polyethylene resin (B) is 1.0 g / 10 min or more and 40 g / 10 min or less at 190 ° C. and a load of 2.16 kg, preferably 2 g / 10 min or more and 40 g / 10 min. Is less than a minute. When the MFR is in the above range, the processability during film formation is excellent. And this MFR range is a high range compared with the polyethylene-type resin (A) mentioned later, and is high fluidity.

Unless otherwise specified, MFR in the present specification is a value obtained by the following method.
MFR (g / 10 min): Measured according to JIS K7210. Specifically, the synthetic resin was heated and pressurized at 190 ° C. in a cylindrical container heated by a heater, and the amount of resin extruded per 10 minutes from an opening (nozzle) provided at the bottom of the container was measured. . The test machine used was an extrusion plastometer, and the extrusion load was 2.16 kg.

  The polystyrene-based weight average molecular weight of the polyethylene resin (B) is preferably 50,000 or more and 100,000 or less. And this molecular weight range is a low range compared with the polyethylene-type resin (A) mentioned later, and is a high fluidity.

[Polyethylene resin (A)]
The polyethylene resin (A) has a density of 0.900 g / cm ³ or less, MFR at 190 ° C. and a load of 2.16 kg measured according to JIS K7210 is 0.1 g / 10 min or more and less than 1.0 g / 10 min. The polystyrene equivalent weight average molecular weight is 120,000 or more and 300,000 or less. That is, the density is similar to that of the polyethylene resin (B), but the MFR is lower than that of the polyethylene resin (B), and the weight average molecular weight is higher than that of the polyethylene resin (B). By including such a polyethylene-based resin (A) in the composition, transparency and thermal fluidity can be improved. The reason for this is not clear, but the film is formed without mixing the polyethylene (A) having a high weight average molecular weight by mixing the polyethylene resin (A) having a high weight average molecular weight with the polyethylene resin (B) having a low weight average molecular weight. As a result, the progress of the crosslinking reaction is delayed, and a sheet having a low weight average molecular weight is formed. This improves the fluidity to such an extent that the heat resistance is not lost because the weight average molecular weight is slightly lowered, and the added polyethylene (A) having a high weight average molecular weight inhibits crystal growth when the sheet is cooled. It is presumed that HAZE decreases as it acts like a nucleating agent.

The polyethylene resin (A) includes a raw material polyethylene resin having a density of 0.900 g / cm ³ or less and a raw material crosslinking agent contained in the composition in an amount of 0.02% by mass or more and less than 0.5% by mass. The raw material polyethylene resin here is not particularly limited and can be used within the range described in the polyethylene resin (B). Among them, the polyethylene resin ( B) is preferably the same resin. Moreover, although a raw material crosslinking agent is not specifically limited, It is preferable that it is the same crosslinking agent as the said crosslinking agent mentioned later.

  The melt mass flow rate (MFR) of the polyethylene resin (A) is 0.1 g / 10 min or more and less than 1.0 g / 10 min at 190 ° C. and a load of 2.16 kg. Moreover, it is preferable that the polystyrene conversion weight average molecular weights of a polyethylene-type resin (A) are 120,000 or more and 300,000 or less. Thus, the improvement effect of the said transparency and heat fluidity is acquired by setting it as low MFR and high molecular weight compared with polyethylene-type resin (B).

  In the present invention, the raw material polyethylene resin, polyethylene resin (A), and polyethylene resin (B) are not only ordinary polyethylene obtained by polymerizing ethylene, but also ethylenic such as α-olefin. Resins obtained by polymerizing compounds having unsaturated bonds, resins obtained by copolymerizing a plurality of different compounds having ethylenically unsaturated bonds, and modified resins obtained by grafting different chemical species to these resins Etc. 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 member such as a transparent front substrate or a solar cell element and the solar cell module sealing material sheet can be obtained.

  The silane copolymer is described in, for example, JP-A-2003-46105. By using the copolymer as a component of the solar cell module sealing material sheet composition, it is excellent in strength, durability, etc., and weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance In addition, it has excellent heat fusion properties without being affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules, and is stable, low cost, and various. A solar cell module suitable for the application 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 a desired reaction vessel, and then the polymerization. 1 to 2 or more types of ethylenically unsaturated silane compounds are graft-copolymerized to the polyolefin-based polymer produced by the above, and further, if necessary, a graft copolymer produced by the copolymer is constituted. A silane compound portion can be modified or condensed to produce a copolymer of an α-olefin and an ethylenically unsaturated silane compound or a modified or condensed product thereof. That.

  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 adhesive strength, it can improve the adhesion of the solar cell module sealing material sheet to other members in the solar cell module. .

  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 ratio of the polyethylene resin (A) and the polyethylene resin (B) is a mass ratio of 5:95 to 50:50, preferably 5:95 to 40:60, particularly preferably 10:90. ~ 30: 70. When the polyethylene resin (A) is less than 5% by mass, the transparency and the heat fluidity (unevenness followability) are insufficient, and when the polyethylene resin (B) exceeds 50% by mass, heat resistance such as heat-resistant creep is achieved. This is not preferable because the properties are lowered.

[Crosslinking agent]
In the present invention, the content of the crosslinking agent with respect to the encapsulant sheet composition for solar cell modules is different from the case where the conventional crosslinking treatment of the encapsulant sheet composition for solar cell modules is performed. The crosslinking agent is used so that the content in a specific range is smaller than that in the case of general crosslinking treatment. Content of a crosslinking agent is 0.02 mass% or more and less than 0.5 mass% in the sealing material sheet 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. If it is less than this range, the weak crosslinking of the polyethylene resin does not proceed and the heat resistance is insufficient. Moreover, when this range is exceeded, film forming property will fall, for example, gel will generate | occur | produce during shaping | molding, and transparency will also fall.

  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 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. These are preferable because the amount of active oxygen is as high as 5% or more, and the 1-minute half-life temperature of the crosslinking agent is 160 to 190 ° C., which is consumed at the time of molding and remains after molding to suppress the progress of excess post-crosslinking. . 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 crosslinking agent during molding.

  In addition, since the raw material crosslinking agent in this invention can use the same thing as the said crosslinking agent, the description is abbreviate | omitted.

[Crosslinking aid]
In the present invention, the crosslinking aid is an optional component. 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.

[Other ingredients]
The sealing material sheet composition can further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance, various fillers, a light stabilizer, an ultraviolet absorber, and a heat stabilizer 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 encapsulant sheet composition. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant sheet composition.

  A weather-resistant 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 this is added to the encapsulant sheet 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.

  Further, as other components used in the solar cell module sealing material sheet composition of the present invention, in addition to the above, an adhesion improver such as a silane coupling agent, a nucleating agent, a dispersing agent, a leveling agent, a plasticizer, Examples include an antifoaming agent and a flame retardant.

<Sealing material sheet>

  The encapsulant sheet for the solar cell module is obtained by subjecting the above encapsulant sheet composition to the above-described weak crosslinking treatment during molding in the process of molding by a conventionally known method, It is a single layer or multilayer sheet or film. In addition, the sheet form in this invention means the film form, and there is no difference in both.

  The sealing material sheet is formed into a sheet by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding, which are usually used in ordinary thermoplastic resins. In addition, as an example of the sheet forming method when the encapsulant sheet is a multilayer film, a method of forming by co-extrusion using two or more types of melt-kneading extruders can be given. However, in any method, in order to promote a weak crosslinking reaction during molding, it is preferable that the film forming temperature is the melting point of the polyethylene resin + 50 ° C. or more. Specifically, the temperature is preferably 100 to 250 ° C., more preferably 190 to 230 ° C. As described above, in the present invention, since the addition of the crosslinking agent is small, the MFR is reduced, but the degree of the reduction is small. For this reason, weak crosslinking can be advanced during melt molding. And even if it is a small amount of crosslinking agents 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 1 minute half-life temperature of the crosslinking agent, the crosslinking agent hardly remains after molding. For this reason, the weak crosslinking ends at this molding stage.

The solar cell module encapsulant sheet of the present invention that has been weakly cross-linked in this way has, from the standpoint of its physical properties, i) maintained low density and ii) improved heat resistance but sufficient production. It has film properties, and iii) is further characterized by improved transparency. Regarding i), the density of the solar cell module encapsulant sheet of the present invention does not increase at about 0.900 g / cm ³ or less, which is almost equal to the density of the low-density polyethylene resin that is the main raw material, and is melt-molded. The density difference between the resin composition before and after is 0.05 g / cm ^{3 or} less. The transparency is very low at 3.0% to 5.0% with a haze value of 600 μm.

  On the other hand, ii) the heat resistance is such that the MFR is 0.1 g / 10 min or more and less than 1.0 g / 10 min, and preferably the MFR difference of the resin composition before and after melt molding is 1.0 g / 10 min or more and 10.0 g / 10 min. Since it is the following, heat resistance is improving though it is in the range of MFR which can be fabricated. This is the effect of the weak crosslinking treatment in the present invention. In general, there is a positive correlation between the MFR and the density of the resin, so that the MFR can be slightly increased within the range of the moldable MFR without changing the density.

In addition, the result of said weak bridge | crosslinking process can be understood also from the gel fraction. The gel fraction of the sealing material sheet of the present invention is 25% or less, preferably 10% or less, 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 sheet is weighed and put into 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. In addition, about the gel fraction of the sealing material sheet | seat which is a multilayer film, the said process is performed with the multilayer state in which all the layers were laminated | stacked, and the obtained measured value is the said multilayer sealing material sheet. The gel fraction was used.

  As another aspect, the weak crosslinking treatment can be confirmed from the viewpoint of molecular weight. The polystyrene equivalent weight average molecular weight of the encapsulant sheet of the present invention is 120,000 to 300,000, and the ratio of the weight average molecular weight of the encapsulant sheet after weak crosslinking / the polyethylene resin before crosslinking is 1.5 or more. The range is 3.0 or less. From this, it can be understood that although it is made into a macromolecule, a dense cross-linked structure is not formed and a weak cross-link is formed. In addition, the weight average molecular weight in this invention melt | dissolves so that it may become 6 wt% of xylene, a viscosity is measured, and the weight average molecular weight is calculated | required from conversion with the polystyrene sample from the viscosity. As for the molecular weight of the encapsulant sheet, which is a multilayer film, the above-mentioned treatment was carried out with all the layers being laminated, and the obtained measurement value was determined based on the gel content of the multilayer encapsulant sheet. Rate.

  In the sealing material sheet which is a multilayer film, it is more preferable to set it as the sealing material sheet from which MFR for every layer differs. As will be described later, in the solar cell module, the sealing material sheet is generally used with one surface being in close contact with the electrode surface of the solar cell element. In that case, the encapsulant sheet is required to have high adhesion regardless of the unevenness of the electrode surface. Even when the encapsulant sheet of the present invention is a single-layer encapsulant sheet, the encapsulant sheet has preferable transparency, flexibility and heat resistance, but the surface which is in close contact with the electrode surface of the solar cell element. Furthermore, it is more preferable that such molding characteristics are excellent. The encapsulant sheet of the present invention, which is a multilayer film having a different MFR for each layer, can be used as an encapsulant sheet by arranging a layer having a high MFR in close contact with the electrode surface of the solar cell element and using it on the outermost layer. While maintaining the above-described preferable transparency and heat resistance, it is possible to further improve the molding characteristics on the contact surface with the solar cell element.

  For example, in the encapsulant sheet which is a multilayer film composed of three or more layers, the thickness of the outermost layer is 30 μm or more and 120 μm or less, and the intermediate layer and the outermost layer composed of all layers other than the outermost layer The thickness ratio is preferably in the range of outermost layer: intermediate layer: outermost layer = 1: 3: 1 to 1: 8: 1. By doing in this way, the preferable heat resistance as a sealing material sheet can be hold | maintained, the preferable molding characteristic in an outermost layer can be provided, and also manufacturing cost can be suppressed low.

<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, the transparent front substrate 2, the front sealing material sheet layer 3, the solar cell element 4, the back sealing material sheet layer 5, and the back surface protection sheet 6 are sequentially arranged from the incident light receiving surface side. Are stacked. The solar cell module 1 of the present invention uses the encapsulant sheet of the present invention for at least the front encapsulant sheet layer 3.

  In the solar cell module 1, for example, the transparent front substrate 2, the front encapsulant sheet layer 3, the solar cell element 4, the back encapsulant sheet layer 5, and the back protective sheet 6 are sequentially laminated. It can be manufactured by integration by vacuum suction or the like, and then thermocompression-molding the above-mentioned member as an integral molded body by a molding method such as a lamination method.

  Moreover, the solar cell module 1 is formed on the front sealing material sheet layer 3 on each of the front surface side and the back surface side of the solar cell element 4 by a molding method usually used in a normal thermoplastic resin, for example, T-die extrusion molding. The back sealing material sheet layer 5 is melt-laminated to sandwich the solar cell element 4 with the front sealing material sheet layer 3 and the back sealing material sheet layer 5, and then the transparent front substrate 2 and the back surface protection sheet 6 are bonded. They may be manufactured by a method of sequentially laminating them and then integrating them by vacuum suction or the like and heat-pressing them.

  In the solar cell module 1 of the present invention, the back sealing material sheet layer 5, the transparent front substrate 2, the solar cell element 4 and the back surface protection sheet 6 which are members other than the front sealing material sheet layer 3 are conventionally known. The material can be used without any 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.

<Raw material of polyethylene resin (A)>
The following raw materials were used.
Base resin: Metallocene linear low density polyethylene (M-LLDPE) pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min were used.
Silane-modified transparent resin: 2 parts by mass of vinyltrimethoxysilane with respect to 98 parts by mass of M-LLDPE having a density of 0.881 g / cm ³ and an MFR of 2 g / 10 min at 190 ° C., and a radical generator Dicumyl peroxide (0.1 part by mass) as (reaction catalyst) was mixed, melted and kneaded at 200 ° C. to obtain a silane-modified transparent resin.
Crosslinking agent master batch: 2,5-dimethyl-2,5- as a crosslinking agent with respect to 100 parts by mass of M-LLDPE pellets having a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. A master batch was obtained by impregnating 0.5 parts by mass of di (t-butylperoxy) hexane.
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.

<Manufacture of polyethylene resin (A)>
70 parts by mass of a base resin, 20 parts by mass of a silane-modified transparent resin, 10 parts by mass of a crosslinking agent masterbatch, and 5 parts by mass of a weatherproof masterbatch are used as the composition (A), and a single-layer φ30 mm extruder, a 200 mm wide T die is used. A polyethylene-based resin (A) was produced by extrusion molding at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min. The density of this polyethylene resin (A) was 0.880 g / cm ³ , and the MFR at 190 ° C. was 0.24 g / 10 minutes.

<Manufacture of sealing material sheet>
Example 1
Using the above base resin as the polyethylene resin (B), 5 parts by mass of the polyethylene resin (A), 60 parts by mass of the polyethylene resin (B) (the base resin), 20 parts by mass of a silane-modified transparent resin, and crosslinking 10 parts by weight of an agent masterbatch and 5 parts by weight of a weatherproof masterbatch, using a single layer φ30 mm extruder and a film forming machine having a 200 mm wide T die, extrusion temperature (film formation temperature) 210 ° C., The sealing material sheet of Example 1 having a thickness of 600 μm was manufactured by extrusion molding at a take-off speed of 1.1 m / min.

(Example 2)
10 parts by mass of a polyethylene resin (A), 55 parts by mass of a polyethylene resin (B) (the above base resin), 20 parts by mass of a silane-modified transparent resin, 10 parts by mass of a crosslinking agent masterbatch, and 5 parts by mass of a weather resistant masterbatch A sealing material sheet of Example 2 having a thickness of 600 μm was produced in the same manner as Example 1 except that the composition was used.

Example 3
40 parts by mass of a polyethylene resin (A), 25 parts by mass of a polyethylene resin (B) (the above base resin), 20 parts by mass of a silane-modified transparent resin, 10 parts by mass of a crosslinking agent masterbatch, and 5 parts by mass of a weather resistant masterbatch A sealing material sheet of Example 3 having a thickness of 600 μm was produced in the same manner as Example 1 except that the composition was used.

(Comparative Example 1)
Contains no polyethylene resin (A), 70 parts by mass of polyethylene resin (B) (the above base resin), 20 parts by mass of a silane-modified transparent resin, 10 parts by mass of a crosslinking agent masterbatch, 5 parts by mass of a weatherable masterbatch, A sealing material sheet of Comparative Example 1 having a thickness of 600 μm was produced in the same manner as in the Example except that the composition was used as a composition.
(Comparative Example 2)
60 parts by mass of a polyethylene resin (A), 5 parts by mass of a polyethylene resin (B) (the above base resin), 20 parts by mass of a silane-modified transparent resin, 10 parts by mass of a crosslinking agent masterbatch, and 5 parts by mass of a weather resistant masterbatch A sealing material sheet of Comparative Example 2 having a thickness of 600 μm was produced in the same manner as in Example 1 except that the composition was used.

<Evaluation example>
About the sealing material sheet | seat of an Example and a comparative example, haze, uneven | corrugated followable | trackability, and 130 degreeC creep were measured.

  Haze: About 600 μm of the sealing material sheets of Examples and Comparative Examples, after preparing a test piece of a film alone, the haze (%) was measured with Murakami Color Research Institute Haze / Transmittance HM150 according to JISK7136. did.

  Concavity and convexity followability: One solar cell module sealing material of the above-mentioned examples and comparative examples cut to a size of 250 mm square on a 250 mm square semi-tempered glass, and a 10 cm square sun in which the bus bar is fixed with solder One set of battery cells arranged in two vertical x two horizontal, one sheet obtained by cutting the solar cell module sealing materials of the above examples and comparative examples into a size of 250 mm square, arbitrary 250 mm The laminated body which laminated | stacked the sheet | seat 1 sheet | seat for corner | angular solar cells in order was crimped | bonded for 15 minutes at 150 degreeC with the vacuum laminator for manufacture of a solar cell module, and the 4-cell solar cell module was created. In the solar cell module, the number and size of remaining bubbles due to defective lamination were evaluated. The case where the bubbles are not substantially present (there is no bubble having a size of 0.5 mm or more), the bubble size is 0.5 mm or more and less than 2 mm and the number is 3 or less, and the evaluation is more than the evaluation Δ. A large size or a large number was marked with x.

  Creep test: Two pieces of the solar cell module sealing materials of the above examples and comparative examples cut to a size of 75 mm × 50 mm on a semi-tempered glass of 250 mm square, back protection for a solar cell module of 75 mm × 50 mm After laminating one sheet in order, it was pressure-bonded at 150 ° C. for 15 minutes with a vacuum laminator for manufacturing a solar cell module, and the laminate sample was left in an oven at 130 ° C. for 12 hours while being inclined at 45 degrees. Then, the heat resistance was evaluated with the distance of the semi-tempered glass being shifted. A deviation of less than 1.5 mm was indicated by ◯, a deviation of 1.5 mm or more and 3 mm or less by Δ, and a deviation of more than 3 mm by ×.

  From the evaluation result of the title, it can be understood that the sealing material sheet of the present invention is improved in transparency and thermal fluidity.

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

Claims (3)

Obtained by melt-molding a resin composition containing a raw material polyethylene resin having a density of 0.900 g / cm ³ or less and a raw material crosslinking agent contained in the composition in an amount of 0.02% by mass or more and less than 0.5% by mass. The following polyethylene resin (A) and the following polyethylene resin (B) are contained in a mass ratio of 5:95 to 50:50, and 0.02 mass in the composition. The manufacturing method of the sealing material sheet | seat for solar cell modules which melt-molds the resin composition containing the crosslinking agent of 0.5% or more and less than 0.5 mass%.
Polyethylene resin (A): MFR at a density of 0.900 g / cm ³ or less, measured at 190 ° C. according to JIS K7210, and a load of 2.16 kg is 0.1 g / 10 min or more and less than 1.0 g / 10 min.
Polyethylene resin (B): MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS K7210 at a density of 0.900 g / cm ³ or less and 1 g / 10 min or more and less than 40 g / 10 min. The polyethylene resin (A) has a polystyrene equivalent weight average molecular weight of 120,000 to 300,000,
The manufacturing method of the sealing material sheet of Claim 1 whose weight average molecular weight of polystyrene conversion of the said polyethylene-type resin (B) is 50,000 or more and 100,000 or less. The raw polyethylene resin and the polyethylene resin (B) are the same,
The manufacturing method of the sealing material sheet of Claim 1 or 2 with which the said raw material crosslinking agent and the said crosslinking agent are the same.

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