JP2014070149A - Method of producing sealing material sheet for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a sealing material sheet for a solar cell module excellent in glass adhesion strength.SOLUTION: A method of producing a sealing material sheet for a solar cell module includes a crosslinking treatment by irradiating an ionization radiation after melt molding a sealing material composition containing: low density polyethylene having a density of 0.900 g/cmor less; a crosslinking agent contained 0.02 mass% or more and less than 0.5 mass% in the composition; and a silane coupling agent. One-hour half-life temperature of the crosslinking agent is a temperature exceeding a film formation temperature+20°C at the melt molding.

Description

  The present invention relates to a method for producing a sealing material sheet for a polyethylene-based solar cell module, and more particularly to a sealing material sheet that has been subjected to crosslinking treatment with ionizing radiation such as an electron beam.

  Conventionally, a combination of an ethylene-vinyl acetate copolymer resin (EVA) and a crosslinking agent typified by an organic peroxide has been used as a sealing material for a solar cell module. In recent years, polyethylene resins have been studied in place of EVA taking advantage of excellent water vapor barrier properties.

  In this regard, in Patent Document 1 below, linear low density polyethylene having a predetermined density or less is crosslinked by irradiating with ionizing radiation, omitting a long-time heat curing step without using an organic peroxide, and having heat resistance. A technique for imparting is disclosed.

JP 2011-77357 A

  Although the crosslinking treatment by irradiation with ionizing radiation is effective for improving the heat resistance, there is a problem that the adhesion strength with glass or the like is lowered by the crosslinking treatment. Therefore, attempts have been made to improve the adhesion strength by adding a silane coupling agent to the composition and grafting the silane coupling agent onto the resin by irradiation with ionizing radiation.

  However, the graft effect by the irradiation of ionizing radiation onto the polyethylene resin is insufficient, and further improvement in adhesion strength has been demanded.

  The present invention has been made to solve the above-mentioned problems, and its object is to provide a polyethylene-based sealing material sheet that is improved in heat resistance by irradiating with ionizing radiation and at the same time has excellent adhesion. There is.

  The present inventors dared to contain a small amount of a crosslinking agent that is an organic peroxide that was considered unnecessary when irradiating with ionizing radiation, and the ionizing radiation was irradiated without reacting this crosslinking agent during film formation. Occasionally, the grafting effect of the silane coupling agent on the polyethylene resin was enhanced, and as a result, it was found that the adhesion strength could be improved, and the present invention was completed. More specifically, the present invention provides the following.

(1) Sealing containing low density polyethylene having a density of 0.900 g / cm ³ or less, a crosslinking agent contained in the composition in an amount of 0.02% by mass or more and less than 0.5% by mass, and a silane coupling agent. A method for producing a sealing material sheet for a solar cell module that is subjected to crosslinking treatment by irradiating ionizing radiation after melt molding the material composition,
The manufacturing method of the sealing material sheet whose 1-hour half-life temperature of the said crosslinking agent is the temperature exceeding the film-forming temperature at the time of the said melt molding +20 degreeC.

  (2) The manufacturing method of the sealing material sheet as described in (1) whose said film-forming temperature is 130 degrees C or less.

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

  Hereinafter, the encapsulant composition according to the present invention (hereinafter also simply referred to as the encapsulant composition), the encapsulant sheet for the solar cell module of the present invention (hereinafter also simply referred to as the encapsulant sheet), and the A solar cell module using a sealing material sheet will be described.

<Encapsulant composition>
The sealing material composition used in the present invention contains low density polyethylene having a density of 0.900 or less, a crosslinking agent, and a silane coupling agent as essential components. Hereinafter, after describing the essential components, other resins and other components will be described.

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

  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 comonomer distribution. For this reason, molecular weight distribution is narrow, it is possible to make it the above ultra-low density, and can give a softness | flexibility with respect to a sealing material. As a result of the flexibility, the adhesion between the sealing material and the substrate, such as the adhesion between the sealing material and the transparent front substrate and the adhesion between the sealing material and the back surface protective sheet, is increased.

  In addition, since the crystallinity distribution is narrow and the crystal sizes are uniform, not only a large crystal size does not exist, but also the crystallinity itself is low due to the low density. For this reason, it is excellent in transparency when processed into a sheet shape. Therefore, even if the sealing material 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 number of carbon atoms of the α-olefin is 6 or more and 8 or less, the sealing material can be given good flexibility and good strength. As a result, the adhesion between the sealing material and the substrate is further increased.

  The melt mass flow rate (MFR) of low density polyethylene is MFR at 190 ° C. and a load of 2.16 kg measured in accordance with JIS-K6922-2 (hereinafter, the measurement value under this measurement condition is referred to as MFR). It is preferably 0.5 g / 10 min or more and 40 g / 10 min or less, and more preferably 2 g / 10 min or more and 40 g / 10 min or less.

  The encapsulant of the present invention is later crosslinked with ionizing radiation. For this reason, even if MFR of the low density polyethylene used as a base is high, fluidity | liquidity can be suppressed at a later bridge | crosslinking process. For this reason, even if it is high MFR like the said range, it can be used conveniently.

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

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

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

  The graft amount, which is the content of the ethylenically unsaturated silane compound, is, for example, 0.001 to 15 masses with respect to a total of 100 mass parts of all the resin components in the sealing material composition containing other polyethylene-based resins described later. What is necessary is just to adjust suitably so that it may become a% grade, Preferably, 0.01-5 mass% grade, Most preferably, it may be 0.05-2 mass% grade. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and heat-fusibility tend to be inferior.

  The sealing material composition of the present invention may further contain an acid-modified polyethylene resin typified by maleic anhydride modification. The acid-modified polyethylene resin is obtained, for example, by graft polymerization using, for example, maleic anhydride or the like as a side chain on linear low density polyethylene (LLDPE) or the like as a main chain. Such a graft polymer has a high polarity of the acid part which contributes to adhesive force, and can improve the adhesiveness of the sealing material sheet to the metal member in the solar cell module.

The density of the acid-modified polyethylene resin is preferably 0.900 g / cm ³ or less, more preferably 0.890 g / cm ³ or less, and particularly preferably 0.870 g / cm ³ or more. It is. Thereby, heat resistance and the adhesiveness to a metal can be made favorable, suppressing blocking.

  The content of the acid-modified polyethylene resin is preferably 15% by mass or more and 40% by mass or less in all resin components. By setting it as this range, generation | occurrence | production of blocking and acidic gas can be suppressed, and heat resistance and the adhesiveness to a metal can be made favorable.

Specific examples of the acid-modified polyethylene resin include maleic anhydride-modified resin. Specific examples include Admer SF731 (manufactured by Mitsui Chemicals, Inc., density 0.880 g / cm ³ ), Admer SF730 (manufactured by Mitsui Chemicals, Inc., density 0.880 g / cm ³ ), and the like.

The content of the polyethylene resin having a density of 0.900 g / cm ³ or less contained in the encapsulant composition is preferably 10% by mass or more and 99% by mass or less, more preferably 50% by mass or more in the composition. It is 99% by mass or less, more preferably 90% by mass or more and 99% by mass or less. That is, other resins may be included as long as the effects of the present invention are not impaired. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later.

[Crosslinking agent]

  As will be described later, the crosslinking agent used in the present invention has only to have a thermal decomposition temperature of the film forming temperature + 20 ° C. or higher, and for example, a 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-butylperoxy) hexane-3 Dialkyl peroxides such as 2,5-dimethyl-2,5-di (t-peroxy) hexyne-3; bis-3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, benzoyl peroxide, Diacyl such as o-methylbenzoyl peroxide and 2,4-dichlorobenzoyl peroxide -Oxides; t-butyl peroxyacetate, t-butylperoxy-2-ethylhexanoate, t-butylperoxypivalate, t-butylperoxyoctoate, t-butylperoxyisopropyl carbonate, t-butyl Peroxybenzoate, di-t-butylperoxyphthalate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexyne-3 Peroxyesters such as t-butylperoxy-2-ethylhexyl carbonate; organic peroxides such as ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; or azobisisobutyronitrile and azobis (2 , 4-Dimethylvalerontri ) Azo compounds such as, can be mentioned dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctoate, dioctyltin dilaurate, dicumyl peroxide, such a silanol condensation catalyst.

  In the present invention, a one-hour half-life temperature is used as the thermal decomposition temperature of the crosslinking agent. Then, by using a cross-linking agent having a one-hour half-life temperature equal to or higher than the film forming temperature, the cross-linking agent can be reacted at the time of irradiation with ionizing radiation without being consumed during reaction. As a result, it has been found that the grafting effect of the silane coupling agent onto the polyethylene resin is enhanced by the effect of the crosslinking agent, and as a result, the adhesion strength can be improved. When the one-hour half-life temperature is less than the film formation temperature, the crosslinking agent is consumed during film formation, and cannot contribute to the grafting, so that the adhesion strength is not improved. Moreover, the load at the time of extrusion becomes high, a gel is generated during molding and the film forming property is lowered, and the transparency is also lowered.

  As an example of such a cross-linking agent, for example, when the film forming temperature is 120 ° C., a cross-linking agent having a one-hour half-life temperature of more than 140 ° C., preferably 150 ° C. or higher is used. Among them, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane-3 can be exemplified.

  As content of a crosslinking agent, it is 0.02 mass% or more and less than 0.5 mass% in a sealing material composition, Preferably an upper limit is 0.2 mass% or less, More preferably, it is 0.1 mass% or less. It is. If it is less than this range, the amount of heat is insufficient in electron beam cross-linking, so that crystals are not dissolved and haze is hardly lowered. On the other hand, if it exceeds this range, the load at the time of extrusion becomes high, gel is generated during molding, and the film forming property is lowered, and the transparency is also lowered.

[Silane coupling agent]
As the silane coupling agent as an adhesion improver added to the sealing material composition, a methacryloxy silane coupling agent, an acryloxy silane coupling agent, an epoxy silane coupling agent or a mercapto silane coupling agent is preferable. Can be used. Of these, an acryloxy-based or methacryloxy-based silane coupling agent is preferable. Specifically, 3-acryloxypropyltrimethoxysilane 3-acryloxypropyltriethoxysilane 3-methacryloxypropyltrimethoxysilane 3-methacryloxypropyltriethoxy Silane 3-acryloxypropylmethyldimethoxysilane 3-acryloxypropylmethyldiethoxysilane 3-methacryloxypropylmethyldimethoxysilane 3-methacryloxypropylmethyldiethoxysilane and the like. The methacryloxy-based and acryloxy-based silane coupling agents are not particularly limited, and known silane coupling agents can be suitably used. For example, "KBM503" and "KBM-5103" (both manufactured by "Shin-Etsu Silicone Co., Ltd.") are available and can be easily obtained from the market.

  Content of these silane coupling agents is 0.1 mass% or more and 10.0 mass% or less in a sealing material composition, Preferably an upper limit is 5.0 mass% or less preferably. If it is less than this range, the adhesion to the members constituting the solar cell module is not improved to a preferred range. On the other hand, when the above range is exceeded, the film-forming property is deteriorated, and the so-called bleed-out in which the silane coupling agent is agglomerated and solidified with time and is pulverized on the surface of the sealing material is not preferable.

[Crosslinking aid]
In the present invention, a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group may be used as a crosslinking aid. More preferably, the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group. This promotes an appropriate crosslinking reaction, and in the present invention, this crosslinking aid reduces the crystallinity of the low density polyethylene and maintains transparency.

  Specifically, polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA) Poly (meth) acryloxy compounds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, Glycidyl methacrylate containing epoxy groups, 4-hydroxybutyl acrylate glycidyl ether and 1,6-hexanediol diglycidyl ether containing two or more epoxy groups, 1 4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and epoxy compounds such as trimethylolpropane polyglycidyl ether. These may be used alone or in combination of two or more.

  Among these, TAIC is preferably used from the viewpoint of good compatibility with low density polyethylene, lowering crystallinity by crosslinking, maintaining transparency, and imparting flexibility at low temperatures. Further, 1,6-hexanediol diacrylate can also be preferably used.

  As content of a crosslinking adjuvant, it is preferable that 0.01 mass%-3 mass% is contained in a composition, More preferably, it is the range of 0.01 mass part-0.1 mass part. Within this range, an appropriate crosslinking reaction can be promoted in advance before irradiation with ionizing radiation.

[Radical absorbent]
In the present invention, the gel fraction can be adjusted more finely by adjusting the degree of cross-linking by using the above-mentioned cross-linking auxiliary agent serving as a radical polymerization initiator in combination with the radical absorbent for quenching it. . Examples of such radical absorbents include hindered phenol-based antioxidants, hindered amine-based weather resistance stabilization, and the like. A hindered phenol-based radical absorbent having a high radical absorbing ability near the crosslinking temperature is preferred. It is preferable that the usage-amount of a radical absorber is contained in 0.01 to 3 mass% in a composition, More preferably, it is the range of 0.05 mass part-2.0 mass parts. Within this range, the gel fraction can be adjusted by appropriately suppressing the crosslinking reaction.

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

  A weatherproof masterbatch is obtained by dispersing a light stabilizer, an ultraviolet absorber, a heat stabilizer and the above-mentioned antioxidant in a resin such as polyethylene, and adding this to a sealing material composition. Thus, good weather resistance can be imparted to the encapsulant. The weatherproof masterbatch may be prepared and used as appropriate, or a commercially available product may be used. The resin used for the weatherproof masterbatch may be the low density polyethylene used in the present invention, or the 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, other components used in the sealing material composition of the present invention include adhesion improvers, nucleating agents, dispersants, leveling agents, plasticizers, antifoaming agents, flame retardants, and the like. it can.

<Sealing material sheet>
The encapsulant sheet of the present invention is obtained by obtaining a pre-encapsulant sheet by a sheet forming step of melt-molding the above encapsulant composition at a temperature exceeding its melting point, preferably 130 ° C. or less, and then ionizing radiation. Through the cross-linking treatment step, the sheet-like or film-like sealing material sheet for the solar cell module of the present invention is obtained. In addition, the sheet form in this invention means the film form, and there is no difference in both.

[Sheet making process]
The melt molding of the sealing material composition is carried out by various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding, which are usually used in ordinary thermoplastic resins. In the present invention, since the half-life temperature of the crosslinking agent is equal to or lower than the film forming temperature, most of the crosslinking agent remains unreacted in the sheet at this stage. In addition, it is preferable that the gel fraction in this pre-sealing material sheet is 0%. The molecular weight is 120,000 to 300,000 in terms of polystyrene-equivalent weight average molecular weight.

[Crosslinking process]
The cross-linking treatment step of performing a cross-linking treatment by ionizing radiation on the preliminary encapsulating material sheet after the above-mentioned sheeting step, the sun integrating the encapsulating material sheet with other members after the completion of the sheeting step Performed before starting the battery module integration process. 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. In the present invention, the crosslinking agent reacts at this time to assist the grafting of the silane coupling agent onto the polyethylene resin, and the adhesion strength can be improved. This is a novel point of the present invention. is there.

  The cross-linking step is preferably performed using ionizing radiation such as electron beam (EB), α-ray, β-ray, γ-ray, neutron beam, and the like. 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 1-100 Mrad, preferably 1-30 Mrad. When the irradiation dose is less than 1 Mrad, sufficient crosslinking is not performed, and when it exceeds 50 Mrad, 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 Examples described later. The heat shrinkage is preferably 45% or less, more preferably 30% or less, and most preferably 20% or less.

  The haze value of the sealing material sheet of the present invention is 4% or less, preferably 3% or less, at a thickness of 400 μm. As described above, in the present invention, the composition contains a crosslinking agent, and in this state, the crosslinking treatment by ionizing radiation is performed, so that the heat resistance and the transparency are made compatible in the polyethylene resin. There is an excellent point of the invention.

  In addition, since the sealing material sheet | seat of this invention obtained in this way is bridge | crosslinked, the annealing process etc. are unnecessary again and can be used in a modularization process as it is.

<Sealing material sheet and solar cell module using the same>
Next, an example of a sealing material sheet obtained by the production method of the present invention and a solar cell module using the same 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 above-described encapsulant sheet for at least one of the front encapsulant sheet layer 3 and the back encapsulant sheet layer 5.

  The encapsulant sheet of the present invention is obtained, for example, by molding the above encapsulant sheet composition by a conventionally known method, and is in the form of a sheet or a 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. Thus, the encapsulant sheet sheet of the present invention is obtained by forming the solar cell module encapsulant sheet composition into a sheet.

  The encapsulant sheet formed into a sheet may not be a single layer. In order to improve the adhesiveness between the encapsulant sheet and the filled member such as the transparent front substrate 2, the solar cell element 4, and the back surface protective sheet 6, the encapsulant sheet for the solar cell module of the present invention is formed at the interface. The composition should just be arrange | positioned. By allowing the encapsulant sheet composition of the present invention to be present near the interface, the encapsulant sheet of the present invention can be produced at a lower cost.

  As a method for causing the encapsulant sheet composition of the present invention to be present in the vicinity of the interface, for example, the encapsulant sheet has a structure of three or more layers, that is, two outermost layers and the outermost layer. And a method comprising a multilayer film having at least a core layer sandwiched between layers. In order to produce a filler sheet made of a multilayer film as described above, for example, a conventionally known T-die multilayer coextrusion method can be used.

  In the solar cell module 1, for example, 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 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. And the back sealing material sheet layer 5 are 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 protection sheet 6 are 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 transparent front substrate 2, the solar cell element 4, and the back surface protection sheet 6 that are members other than the front surface sealing material sheet layer 3 and the back surface sealing material sheet layer 5 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.

[Test Example 1]
In order to measure the glass adhesion strength, haze value (JIS K7136), 150 ° C. vertical displacement test, thermal shrinkage, total light transmittance, YI (yellowness), and gel fraction of the sealing material sheet of the present invention. As described below, the sealing material sheets of Examples and Comparative Examples were produced, and the physical properties of the respective sealing material sheets were measured.

[Example 1]
First, the following master batch and compound pellets were prepared.
Silane coupling agent master batch: 3 parts per 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and MFR at 190 ° C. of 30 g / 10 min. -2 parts by mass of methacroxytripropylmethoxysilane were mixed, melted and kneaded at 200 ° C to obtain a pelletized master batch.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and hindered amine system with respect to 100 parts by mass of M-LLDPE having a density of 0.881 g / cm ³ and MFR at 190 ° C. of 30 g / 10 min. 5 parts by mass of a light stabilizer and 0.5 parts by mass of a phosphorous heat stabilizer were mixed and melted and processed to obtain a pelletized master batch.
Crosslinking agent compound resin: 2,5-dimethyl-2,5-di (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 30 g / 10 min. Compound pellets were obtained by impregnating 0.05 parts by mass of t-butylperoxy) hexane-3 (1 hour half-life temperature 152 ° C.).

  Next, 20 parts by mass of the silane coupling agent masterbatch, 5 parts by mass of the weatherproof masterbatch, and 80 parts by mass of the crosslinker compound resin are mixed and melted to obtain a sealing material composition, a φ30 mm extruder, 200 mm width A pre-encapsulant sheet having a thickness of 400 μm was prepared at an extrusion temperature of 120 ° C. and a take-off speed of 1.1 m / min.

  Next, the preliminary sealing material sheet was irradiated with an acceleration voltage of 200 kV and an irradiation intensity of 75 kGy (7.5 Mrad) using an electron beam irradiation apparatus (product name: EC250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) Example 1).

[Comparative Example 1]
The sealing of Comparative Example 1 was carried out in the same manner as in Example 1 except that the crosslinking agent compound resin of Example 1 was only M-LLDPE having an MFR of 190 g / 10 min at 190 ° C. without containing a crosslinking agent. A material sheet was obtained.

[Comparative Example 2]
Example except that 0.05 part by mass of 5 dimethyl 2,5 di (t-butylperoxy) hexane (1 hour half-life temperature 140 ° C.) was impregnated as a crosslinking agent in the crosslinking agent compound resin to obtain compound pellets. In the same manner as in Example 1, a sealing material sheet of Comparative Example 2 was obtained.

<Evaluation Example 1>
About an Example and a comparative example, it measured about glass adhesion strength (after an initial stage and dump heat test 1000 hours) and heat-resistant creep. The results are shown in Table 1. Each test condition is as follows.

  Glass adhesion strength: The sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm were adhered to each other on a glass substrate (white plate semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) at 150 ° C., 18 In each minute, the sample is processed with a vacuum heating laminator to obtain solar cell module evaluation samples for each of the examples and comparative examples, and the sealing material sheet in close contact with the glass substrate is peeled off by a peel tester (Tensilon universal test). Machine RTF-1150-H) was subjected to a vertical peeling (50 mm / min) test to measure the glass adhesion strength.

  Heat-resistant creep: Two pieces of the solar cell module sealing material of Example 1 and Reference Example 1 cut into a size of 75 mm × 50 mm on a 250 mm square semi-tempered glass, 75 mm × 50 mm semi-tempered glass 1 After laminating the sheets in order, they were pressure-bonded at 150 ° C. for 15 minutes with a vacuum laminator for manufacturing a solar cell module, and the laminate sample was left standing in an oven at 140 ° C. for 12 hours in a standing state. The displaced distance (mm) of the tempered glass was measured. The results are shown in Table 2.

  From Table 1, it can be understood that the glass adhesion strength is improved in Examples in which the one-hour half-life temperature exceeds the film forming temperature + 20 ° C. as compared with the case without the crosslinking agent.

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 (2)

A sealing material composition comprising low density polyethylene having a density of 0.900 g / cm ³ or less, a crosslinking agent contained in the composition in an amount of 0.02% by mass or more and less than 0.5% by mass, and a silane coupling agent. Is a method for producing a sealing material sheet for a solar cell module that is subjected to crosslinking treatment by irradiating ionizing radiation after melt molding,
The manufacturing method of the sealing material sheet whose 1-hour half-life temperature of the said crosslinking agent is the temperature exceeding the film-forming temperature at the time of the said melt molding +20 degreeC.   The method for producing a sealing material sheet according to claim 1, wherein the film forming temperature is 130 ° C. or lower.

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