JP6028472B2 - Manufacturing method of sealing material sheet for solar cell module - Google Patents

Description

  The present invention relates to a polyethylene-based solar cell module sealing material sheet and a solar cell module using the same.

  Conventionally, as a sealing material sheet for a solar cell module, a combination of an ethylene-vinyl acetate copolymer resin (EVA) and a crosslinking agent typified by an organic peroxide has been used. However, with the recent increase in the output of solar cells, a sealing material having a high electric resistance value is required, and the problem that the electric resistance value of EVA having a polar group becomes apparent. It has become.

  As an alternative material that can solve this electrical resistance problem, it is conceivable to use a polyethylene resin having no polar group. Here, the electrical resistance value of the polyethylene-based sealing material sheet depends on the density of the polyethylene resin used and the degree of crosslinking. The higher the density and the degree of crosslinking, the higher the electric resistance value. However, since a high-density polyethylene resin lacks transparency, it is not preferable as a material for a solar cell encapsulant. Therefore, in order to provide a preferable electrical resistance value in the polyethylene-based sealing material sheet, a crosslinking treatment to low-density polyethylene is essential.

  As such a low-density polyethylene encapsulant sheet, an appropriate amount of a cross-linking agent was added to such an encapsulant composition so that the cross-linking proceeded substantially only during vacuum lamination during integration as a solar cell module. A thermosetting polyethylene sealing material is disclosed (see Patent Document 1).

  In addition to the thermal crosslinking treatment described above, a technique for improving the heat resistance of the encapsulant sheet without using a crosslinking agent by irradiating the polyethylene resin with ionizing radiation as a crosslinking treatment method is also available. It is disclosed (see Patent Document 2).

JP 2012-54521 A JP 2009-249556 A

  Here, for example, when a thermosetting polyethylene resin is used as the material resin of the encapsulant sheet as in the encapsulant sheet described in Patent Document 1, it is necessary to use a resin having a high MFR to some extent. . However, the thermosetting polyethylene resin has a low crosslinking rate due to the small number of double bonds, and takes a lot of time for vacuum heating and pressing (thermal lamination) in the modularization process, resulting in poor productivity. Since it is MFR and the progress of cross-linking is slow, the film thickness changes greatly during thermal lamination, and the yield is reduced.

  In order to solve the problem, development of a thermoplastic polyethylene sealing material has been performed. In thermoplastic resins that are not subjected to thermosetting treatment, including the sealing material sheet described in Patent Document 2 above, physical properties do not change during thermal lamination, so it is inevitably necessary to provide heat resistance. A resin with a low MFR was selected. Specifically, a low-density polyethylene resin having a relatively large molecular weight and low fluidity, more specifically, a melt mass flow rate (MFR) at 190 ° C. and a load of 2.16 kg measured in accordance with JIS K6922-2 (in this specification, Hereinafter, a polyethylene resin having a measured value under these measurement conditions is referred to as “MFR”) of less than 20.0 g / 10 min is used, and a low molecular weight polyethylene resin having an MFR of 20.0 g / 10 min or more is used. In the sealing material of thermoplastic resin, it was practically excluded from the choice as a material resin of the sealing material for solar cell modules.

  However, further cost reduction is required for widespread use of photovoltaic power generation. In general, high molecular weight (low MFR) polyethylene resins are relatively expensive compared to low molecular weight (high MFR) polyethylene resins. Therefore, it has been strongly desired to develop a sealing material sheet that has various physical properties required for a sealing material sheet for a solar cell module and is further excellent in economic efficiency. As means for that, development of a solar cell module sealing material sheet using a low molecular weight (high MFR) polyethylene resin that is generally available at low cost has been demanded.

  The object of the present invention is to produce an excellent solar cell module sealing material sheet having both heat resistance and adhesiveness at a lower cost than in the case of using a conventionally known production method by selecting a low molecular weight (high MFR) polyethylene resin. Is to provide.

  The inventors of the present invention perform film formation by extrusion molding of a high MFR sealing material composition containing a predetermined amount of a crosslinking aid without proceeding with crosslinking, and irradiate with ionizing radiation before modularization. Thus, a sealing material sheet in which the gel fraction and the complex viscosity are optimized within a predetermined preferable range can be obtained, and thereby, the electrical resistance is comparable to or higher than that of the conventional product. The present inventors have found that a solar cell module sealing material sheet having various properties such as value, transparency, heat resistance, and adhesiveness can be produced at a lower cost than conventional products, thereby completing the present invention. More specifically, the present invention provides the following.

(1) A low-density polyethylene having a density of 0.900 g / cm ³ or less and a crosslinking aid which is a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group, and has a gel fraction of 2% The complex viscosity at 100 ° C. or higher and 110 ° C. or lower is 5.0E + 4 Pa · S or higher and 5.0E + 5 Pa · S or lower, and the complex viscosity at 140 ° C. or higher and 150 ° C. or lower is 5.0E + 4 Pa · S or higher. The sealing material sheet for solar cell modules which is 3.0E + 5Pa * S or less and whose complex viscosity in 180 degreeC or more and 200 degrees C or less is 3.0E + 4Pa * S or more and 1.0E + 5Pa * S or less.

  (2) A solar cell module provided with the sealing material layer which consists of a sealing material sheet for solar cell modules as described in (1).

(3) A sheet forming step for obtaining an uncrosslinked encapsulant sheet by melt-molding an encapsulant composition containing a density of 0.900 g / cm ³ or less, a low density polyethylene, and a crosslinking aid; A crosslinking step of crosslinking an uncrosslinked sealing material sheet so that the gel fraction is 2% or more and 80% or less by irradiation with ionizing radiation, and the low density polyethylene was measured according to JIS K6922-2. The manufacturing method of the sealing material sheet for solar cell modules whose MFR in 190 degreeC and a load of 2.16 kg is 20.0 g / 10min or more and 40.0 g / 10min or less.

  According to the solar cell module encapsulant and solar cell module of the present invention, a solar cell module encapsulant sheet having various characteristics required for a solar cell module encapsulant sheet equivalent to a conventional product, It can be obtained at a lower cost than in the past.

It is sectional drawing which shows an example of the laminated constitution about the solar cell module using the sealing material sheet of this invention. It is the graph which showed the change of the complex viscosity in 60-200 degreeC of the sealing material sheet of this invention.

  The encapsulant sheet for solar cell module of the present invention is highly preferable as a encapsulant sheet for solar cell module by limiting the gel fraction and the complex viscosity to the above predetermined ranges. It is characterized by having characteristics. Hereinafter, the solar cell module encapsulant composition (hereinafter also simply referred to as “encapsulant composition”) and the solar cell module encapsulant sheet (hereinafter simply referred to as “encapsulant sheet”) according to the present invention. And the solar cell module in this order.

<Encapsulant composition>
The sealing material composition used in the present invention has a density of 0.900 g / cm ³ or less, and an MFR of 20.0 g / 10 min or more at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2. Low-density polyethylene of 0.0 g / 10 min or less and a crosslinking aid are contained 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 g / cm ³ 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 from 0.870 g / cm ³ or more 0.885 g / cm ³ or less. 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 a softness | flexibility can be provided 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 metallocene linear low density polyethylene has a narrow crystallinity distribution and a uniform crystal size, 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 sheet can be given good flexibility and good strength. As a result, the adhesion between the encapsulant sheet and the substrate is further enhanced.

  The MFR of the low density polyethylene is preferably 20.0 g / 10 min or more and 40.0 g / 10 min or less, and more preferably 25.0 g / 10 min or more and 35.0 g / 10 min or less. The sealing material sheet of the present invention is essential to perform a crosslinking treatment by irradiation with ionizing radiation after molding the sealing material composition, and to add a predetermined amount of crosslinking aid to the sealing material composition. By adjusting the gel fraction and the complex viscosity to a predetermined range while using a polyethylene resin having a high MFR that has not been used as a material resin in the past, the physical properties that are excellent as before or higher It is set as the sealing material sheet provided with.

  The encapsulant sheet of the present invention is a non-crosslinked encapsulant having a gel fraction of 0% by melting and forming an encapsulant composition containing a predetermined amount of a crosslinking aid as an essential component without causing a crosslinking reaction. After forming into a sheet, it can be obtained by carrying out a crosslinking treatment by irradiation with ionizing radiation to obtain a crosslinked sealing material sheet. When the crosslinking treatment is performed by irradiation with ionizing radiation, the fluidity at the time of modularization can be suppressed by the crosslinking treatment by irradiation with ionizing radiation after film formation. Therefore, it is possible to select a low-density polyethylene resin having a somewhat high MFR as a base resin. it can. In general, when the crosslinking treatment is performed by irradiation with ionizing radiation, specifically, as described above, a low density polyethylene resin having an MFR of about 5.0 g / 10 min or less is used in order to balance workability and heat resistance. It was used as a preferable base resin.

  In this specification, the gel fraction (%) refers to 0.1 g of a sealing material sheet placed in a resin mesh, extracted with 60 ° C. toluene for 4 hours, then taken out together with the resin mesh, weighed after drying, Mass comparison before and after extraction is performed to measure the mass% of the remaining insoluble matter, and this is used as the gel fraction. A gel fraction of 0% means that the residual insoluble matter is substantially 0 and that the crosslinking reaction of the encapsulant composition has not substantially started. More specifically, “gel fraction 0%” in the present invention means that the residual insoluble matter is not present at all, and the residual insoluble matter mass% measured by a precision balance is less than 0.05 mass%. Let's say the case.

  Moreover, the sealing material sheet which concerns on this invention can make a softness | flexibility and heat resistance compatible further by using the crosslinking adjuvant of a predetermined amount range as an essential structural component of a sealing material composition. For this reason, for example, even if the MFR is 20.0 g / 10 min or more, which is conventionally considered to be unsuitable as a resin for a sealing material composition because of its too high fluidity, It can be preferably used as a resin. Thereby, the manufacturing cost of the sealing material sheet can be suppressed while providing desired physical properties.

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

  The silane-modified polyethylene resin can be produced, for example, by the method described in JP-A-2003-46105. By using the resin as a component of a sealing material composition for a 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 that have extremely excellent heat-fusibility, are stable and low-cost, and are 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. Part, preferably 0.01 to 5 parts by mass, particularly preferably 0.05 to 2 parts by mass. In the present invention, when the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. However, when the content is excessive, the tensile elongation and the heat fusion property tend to be inferior.

The content of polyethylene having a density of 0.900 g / cm ³ or less contained in the encapsulant composition is preferably 10 or more and 100 with respect to 100 parts by mass in total of all resin components in the encapsulant composition. It is not more than part by mass, more preferably not less than 50 parts by mass and not more than 100 parts by mass, and still more preferably not less than 90 parts by mass and not more than 100 parts by mass. Other resin may be included as long as the melting point of the sealing material composition is within a range of less than 80 ° C. These may be used, for example, as an additive resin, or may be used for masterbatching other components described later.

[Crosslinking aid]
In the sealing material composition for producing the sealing material sheet of the present invention, a crosslinking aid is an essential component. On the other hand, as will be described in detail later, the crosslinking agent is not necessarily an essential component in the encapsulant composition, and if included, it is limited to a very small amount. Such a unique combination of the crosslinking aid and the crosslinking agent in the sealing material composition is a feature of the method for producing the sealing material sheet of the present invention.

  The crosslinking aid is not particularly limited, and known ones can be used. An example of a crosslinking aid that can be preferably used includes a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group. Further, examples of the crosslinking aid that can be used more preferably include those in which the functional group of the polyfunctional monomer is an allyl group, a (meth) acrylate group, or a vinyl group.

  Specific examples of the crosslinking aid that can be used in the production method of the present invention include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, diallyl maleate, and trimethylol. Propane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol Poly (meth) acryloxy compounds such as diacrylate, glycidyl methacrylate containing double bond and epoxy group, 4-hydroxybutyl acrylate glycidyl ether and two or more epoxy groups That 1,6-hexanediol diglycidyl ether, 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 from the viewpoint of reactivity with the silane coupling agent.

  The content of the crosslinking aid is preferably included in a range of 0.05 parts by weight or more and less than 1.0 part by weight, more preferably 0.1 parts per 100 parts by weight of all components of the sealing material composition. It is a range of not less than 0.5 parts by mass.

  By containing the above-mentioned crosslinking aid in the encapsulant composition with the above content, the gel fraction of the crosslinked encapsulant sheet before modularization is promoted by promoting an appropriate crosslinking reaction by irradiation with ionizing radiation. Can be 2% or more and 80% or less.

  Addition of an appropriate amount of a crosslinking aid to the encapsulant composition can appropriately promote the cross-linking reaction by irradiation with ionizing radiation, so that the encapsulant has appropriate heat resistance and surface fluidity. Here, when the crosslinking agent is not contained in the encapsulant composition, if the crosslinking reaction by the irradiation of ionizing radiation is similarly promoted, the irradiation amount of the ionizing radiation is inevitably too strong, The fluidity of the surface is insufficient, resulting in a lack of unevenness followability.

  Moreover, the addition of an appropriate amount of a crosslinking aid to the encapsulant composition can lower the crystallinity of the linear low density polyethylene and maintain transparency. As a result, specifically, it is possible to obtain transparency and heat resistance comparable to those of EVA and a low MFR polyethylene resin, low-temperature flexibility, electrical characteristics, and the like that are superior to those.

[Crosslinking agent]
In the production method of the present invention, the crosslinking agent is not an essential component of the encapsulant composition. The content of the crosslinking agent in the sealing material composition may be zero. Even when a crosslinking agent is added, the addition amount is preferably 0.4 parts by mass or less, and 0.1 parts by mass or less, with respect to 100 parts by mass of all components in the sealing material composition. It is more preferable that By limiting the amount of the crosslinking agent added to the encapsulant composition below this range, it is possible to suppress the crosslinking of the resin during film formation and the film forming process load, and to form a sheet, especially in terms of durability by chemical crosslinking. It can be set as the excellent sealing material sheet. When the content of the cross-linking agent exceeds 0.4 parts by mass, film formation becomes impossible due to cross-linking during film formation. In the method for producing a sealing material sheet of the present invention, the sealing material composition is subjected to a crosslinking treatment by irradiation with ionizing radiation, and 0.05 parts by mass or more of a crosslinking aid is sealed as an essential component. It is added to the stopping material composition. In this case, the addition amount of the cross-linking material is different from the conventional case of thermal cross-linking or cross-linking by irradiation with ionizing radiation, even if the addition amount of the cross-linking material is less than 0.4 parts by mass. Sufficient heat resistance and electrical resistance can be obtained by advancing crosslinking. Thereby, the risk of productivity reduction due to the gelation of the sealing material composition in the sheet forming step of the sealing material composition can also be reduced, and the production cost can be reduced by reducing the amount of the crosslinking agent used. .

  In general, a conventional uncrosslinked sealing material sheet is required to undergo a crosslinking treatment in a modularization process. For this reason, the half-life temperature of the crosslinking agent used for the crosslinking treatment of the uncrosslinked encapsulant sheet is limited by the heating temperature and heating time conditions in the modularization process, and the one-minute half-life temperature is generally less than 185 ° C. Was virtually limited to. However, when the crosslinked sealing material sheet of the present invention is produced, the crosslinking agent can be selected without being subjected to the above-described restrictions. Generally, the upper limit temperature of the cross-linking agent is about 230 ° C. from the viewpoint of resin oxidative degradation, but in the production of the cross-linked encapsulant sheet of the present invention, the half-life temperature for 1 minute is within this range. A crosslinking agent at 185 ° C. or higher can also 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.

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

[Adhesion improver]
In the production method of the present invention in which the crosslinking treatment is performed by irradiation with ionizing radiation, it is preferable to add the above-described adhesion improver to the encapsulant composition. This is because when the ionizing radiation is irradiated in a large amount, the enlargement ratio can be suppressed, but the adhesion component on the surface of the sealing material sheet may be damaged and the adhesion may be lowered, but the low molecular weight silane coupling agent It is presumed that the adhesion can be ensured by the seepage effect. Thereby, irradiation with stronger EB can be performed, and a more preferable enlargement ratio can be suppressed. As the adhesion improver, a known silane coupling agent can be used. The silane coupling agent is not particularly limited. For example, vinyl-based silane coupling agents such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropyldiethoxy. A methacryloxy-based silane coupling agent such as silane or 3-methacryloxypropyltriethoxysilane can be preferably used. In addition, these can also be used individually or in mixture of 2 or more types. Among these, a methacryloxy silane coupling agent can be particularly preferably used.

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

[Radical absorbent]
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. The amount of the radical absorbent used is preferably 0.01 parts by weight or more and 3 parts by weight or less, more preferably 0.05 parts by weight or more and 2.0 parts by weight or less in the composition. Within this range, the crosslinking reaction can be moderately suppressed. Specifically, the gel fraction of the crosslinked encapsulant sheet before modularization can be 80% or less.

[Other ingredients]
The sealing material composition may further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance to a sealing material sheet produced from the sealing material composition of the present invention, various fillers, a light stabilizer, an ultraviolet absorber, and a heat stabilizer Illustrated. These contents vary depending on the particle shape, density and the like, but are preferably in the range of 0.001 to 5 parts by mass in the encapsulant composition. By including these additives, it is possible to impart a mechanical strength that is stable over a long period of time, an effect of preventing yellowing, cracking, and the like to the encapsulant composition.

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

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

  Further, other components used in the sealing material composition of the present invention include nucleating agents, dispersants, leveling agents, plasticizers, antifoaming agents, flame retardants and the like.

<Sealing material sheet>
The sealing material sheet of the present invention obtains an uncrosslinked sealing material sheet by a sheet forming process in which the above-described sealing material composition is melt-molded at a temperature exceeding its melting point, and then a crosslinking process by irradiation with ionizing radiation. As a result, a crosslinked sealing material sheet having a gel fraction of 2% or more and 80% or less is obtained. In addition, the sheet form in this invention means the film form, and there is no difference in both.

[Sheet making process]
Film formation by melt molding of the above-mentioned sealing material composition is performed 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. .

  The lower limit of the molding temperature during molding may be any temperature that exceeds the melting point of the encapsulant composition. The upper limit of the molding temperature is the temperature at which crosslinking does not start during film formation, that is, the temperature at which the gel fraction of the encapsulant composition can be maintained at 0%, depending on the 1 minute half-life temperature of the crosslinking agent used. Good. Here, in the method for producing a sealing material sheet of the present invention, a crosslinking agent is not essential in the sealing material composition, and even when a crosslinking agent is added, the content is 0.4 parts by mass or less. It is limited to. For this reason, under a normal low density polyethylene resin molding temperature, for example, a heating condition of about 120 ° C., the gel fraction does not change, and the crosslinking that substantially affects the physical properties of the resin does not proceed. In addition, as described above, it is possible to use a cross-linking agent having a half-life temperature higher than that of the conventional one by solving from the limitation of the heating conditions in the modularization process. Therefore, even if the molding temperature is set higher than before, the gel fraction of the encapsulant composition can be maintained at 0%. According to the production method of the present invention that maintains the gel fraction of the encapsulant composition during film formation at 0%, the load on the extruder and the like during film formation is reduced, and the productivity of the encapsulant sheet is increased. It is possible.

  In the uncrosslinked encapsulant sheet that has undergone the sheet forming step, it is preferable that the number average molecular weight of the low density polyethylene used as the material of the encapsulant composition is from 50,000 to 80,000. The encapsulant sheet of the present invention can be obtained by using a crosslinking assistant as an essential component of the encapsulant composition and performing a crosslinking step by irradiation with ionizing radiation. Therefore, it is possible to use a resin having relatively higher fluidity than the conventional one as the sealing material composition. Specifically, even within the above range, even a low density polyethylene having a number average molecular weight of 75,000 or less can be preferably used. Thereby, productivity of a sealing material sheet and a solar cell module using the same can be improved. The number average molecular weight can be measured by dissolving in a solvent such as THF and using a conventionally known GPC method.

[Crosslinking process]
The cross-linking process for performing a cross-linking process on the uncross-linked encapsulant sheet after the sheet forming process is performed after the sheet forming process is completed by the cross-linking process by irradiation with ionizing radiation, and the encapsulant sheet is integrated with other members. Before starting the solar cell module integration process. It is a feature of the encapsulant sheet of the present invention that the gel fraction and complex viscosity of the encapsulant sheet are optimized within a predetermined range by such a crosslinking step. Thus, by performing the crosslinking process by irradiation of ionizing radiation, it can be set as the sealing material sheet provided with higher adhesiveness and heat resistance than the case where it manufactures by the crosslinking process by heating.

  Regarding the gel fraction of the cross-linked encapsulant sheet after passing through the cross-linking step by irradiation with ionizing radiation, the irradiation amount of ionizing radiation and the addition amount of the cross-linking agent are appropriately adjusted so as to be 2% or more and 80% or less. . The gel fraction is preferably 2% or more and 80% or less, and more preferably 10% or more and 60% 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. . If 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 it as an encapsulant sheet. 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 encapsulant sheet for a solar cell module preferably has a heat shrinkage rate of a predetermined value or less in order to maintain a high yield rate at the time of module manufacture. For example, 150 degreeC, evacuation: 5 minutes, pressurization: (0 kPa to 100 kPa): 1.5 minutes, pressure holding (100 kPa): 7.0 minutes When sealing is performed under general conditions The thermal contraction rate of the sheet is preferably 45% or less, more preferably 30% or less, and most preferably 20% or less. Even if the sealing material sheet of the present invention uses a high MFR polyethylene resin having an MFR of 20.0 g / 10 min to 40.0 g / 10 min, the shrinkage rate is suppressed to 45% or less. It is something that can be done.

  About the complex viscosity of a sealing material sheet, bridge | crosslinking conditions are adjusted so that the complex viscosity in 100 degreeC or more and 110 degrees C or less may be 5.0E + 4Pa * S or more and 3.0E + 5Pa * S or less. By setting the complex viscosity at 100 ° C. or higher and 110 ° C. or lower to 5.0E + 4 Pa · S or higher, heat resistance necessary as a sealing material sheet for a solar cell module can be provided. Moreover, by setting the complex viscosity to 5.0E + 5 Pa · S or less, it is possible to provide impact resistance performance that can sufficiently protect the solar cell element from external impact.

  Moreover, about the complex viscosity of a sealing material sheet, bridge | crosslinking conditions are adjusted so that the complex viscosity in 140 to 150 degreeC may be 5.0E + 4Pa * S or more and 3.0E + 5Pa * S or less. By setting the complex viscosity at 140 ° C. or more and 150 ° C. or less to 5.0E + 4 Pa · S or more, an excessive change in film pressure during the heat laminating process is suppressed, and by setting the complex viscosity to 3.0E + 5 Pa · S or less. Moreover, the favorable sealing performance by the surroundings of the sealing material to the unevenness | corrugation in the lamination surface between the members of a solar cell module can be provided. That is, it is possible to maintain good sealing performance against unevenness while suppressing excessive flow.

  Furthermore, about the complex viscosity of a sealing material sheet, bridge | crosslinking conditions are adjusted so that the complex viscosity in 180 degreeC or more and 200 degrees C or less may be 3.0E + 4Pa * S or more and 1.0E + 5Pa * S or less. By setting the complex viscosity at 180 ° C. or higher and 200 ° C. or lower to 3.0E + 4 Pa · S or higher, the sealing material sheet for solar cell module is a thermoplastic sealing material sheet that does not require a crosslinking step by a heating step. As mentioned above, the necessary heat resistance can be provided. Further, by setting the complex viscosity to 1.0E + 5 Pa · S or less, necessary adhesion with other members such as glass and metal at the time of integration as a solar cell module can be provided.

  Furthermore, the installation conditions of the solar cell module are often tilted to about 45 degrees and are often exposed to severe temperature conditions under severe direct sunlight. Under such installation conditions, if the viscosity of the encapsulant sheet in the high temperature region is not more than a predetermined value, there is a fear that it may lead to problems such as a shift or crack of the solar electronic element or a short circuit in the module. . About the sealing material whose complex viscosity of the said range of 180 degreeC or more and 200 degrees C or less exists in the said range, said malfunction under all the use conditions which can be assumed can be avoided almost certainly.

  The resin temperature of the encapsulant sheet can be measured by attaching a temperature sensor thermocouple to the upper surface of the encapsulant sheet during heating and using a temperature / humidity data logger. The resin temperature refers to, for example, the resin temperature of the sealing material sheet measured as described above.

  In addition, although the sealing material sheet of this invention can be preferably used as a member which comprises a solar cell module by integrating with another member, it is common in the integration process as a solar cell module. The above crosslinking conditions can be realized by heat laminating treatment depending on conditions. About an example of the additional conditions at the time of such lamination, a specific example is shown in an Example later.

  Here, the complex viscosity (Pa · s) is a rotational rheometer (MCR301 manufactured by Anton Paar), parallel plate geometry (diameter 8 mm), stress 0.5 N, strain 5%, angular velocity 0.1 ( 1 / s), measured at conditions of a heating rate of 5 ° C./min, and this is the complex viscosity.

  Regarding the crosslinking treatment by irradiation with ionizing radiation, the individual crosslinking conditions are not particularly limited, and may be appropriately set so that the complex viscosity is in the above range as a total treatment result. The gel fraction is also preferably in the above range. 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 5 kGy to 500 kGy, preferably 5 to 200 kGy. When the irradiation dose is less than 5 kGy, sufficient crosslinking is not performed, and when it exceeds 500 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.

  This crosslinking treatment may be performed continuously in-line following the sheet forming step, or may be performed off-line. Further, when the crosslinking treatment is a general heat treatment, generally, the content of the crosslinking agent is 0.5 parts by mass or more and 1.5 parts by mass or less with respect to 100 parts by mass of all components of the sealing material sheet. However, in the encapsulant sheet of the present invention, the content of the crosslinking agent may be 0, and even if it is contained, it is preferably less than 0.4 parts by mass. Thereby, the risk of the productivity fall by gelatinization of the sealing material composition in the sheeting process of a sealing material composition can be reduced.

  At the time when the film is formed through the sheet forming step, the encapsulant sheet is uncrosslinked and its gel fraction is 0%. And in the said bridge | crosslinking process, it becomes the bridge | crosslinking sealing material sheet of 2 to 80% of gel fraction. In order to realize such a process, it is necessary to use a polyethylene resin having a high MFR as a base resin and a crosslinking agent having a high 1-minute half-life temperature. Such material selection is possible only when the manufacturing method of the present invention is a novel process different from the conventional configuration as described above. That is, a sheet forming process for forming a sealing material composition containing a crosslinking assistant in an uncrosslinked state, and a sealing material sheet that has been crosslinked before modularization of an uncrosslinked sealing material sheet by irradiation with ionizing radiation Due to the unique configuration, it is possible to produce a sealing material sheet that follows the transition of the gel fraction as described above. With this production method, high adhesion, heat resistance, sufficient volume resistivity, etc. Can be manufactured at a lower cost than in the past.

<Solar cell module>
FIG. 1: is sectional drawing which shows an example of the layer structure about the solar cell module using the sealing material sheet of this 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 above-described sealing material sheet for at least one of the front sealing material layer 3 and the back sealing material layer 5.

[Method for manufacturing solar cell module]
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.

  According to the method for manufacturing a solar cell module of the present invention, the above-described thermocompression treatment can be performed at 110 ° C. or higher and 140 ° C. or lower. When a conventional EVA sealing material is used, heating exceeding 140 ° C. is generally essential. In addition, since a general polyethylene-based sealing material sheet has a low crosslinking rate, when it is used, for example, when laminating is performed at a temperature of 140 ° C. or lower, heating for a long time is required. There are disadvantages such as a large change in film thickness, or the need for a second heat cure after integration.

  Also, conventionally, when a high MFR thermoplastic polyethylene resin having an MFR of 20.0 g / 10 min or more is used, there is a problem that heat resistance and molding stability are inferior. In fact, the MFR was limited to a resin having a MFR of less than 20.0 g / 10 min. However, in the production method of the present invention, since a polyethylene resin having an MFR of 20.0 g / 10 min or more can be used, the laminate process is appropriately performed even at a lower temperature, and the production of the solar cell module is carried out in a preferable mode. can do. For this reason, the range of selection of laminating conditions such as the type and amount of the crosslinking agent, the heating temperature and the time is widened, and by optimizing them, higher productivity than the conventional method can be realized.

  It is preferable that the gel fraction after thermocompression molding of the front sealing material layer 3 and the back sealing material layer 5 using the sealing material sheet of the present invention is 20% or more and 80% or less. By setting it as this range, the solar cell module 1 can be equipped with the sealing material layer which has high transparency, and shall have preferable heat resistance.

  Further, the solar cell module 1 has a complex viscosity of 180 ° C. or more and 200 ° C. or less after the thermocompression bonding of the front sealing material layer 3 and the back sealing material layer 5 using the sealing material sheet of the present invention. It is preferably 0E + 4 Pa · S or more and 1.0E + 5 Pa · S or less. By setting the complex viscosity to 3.0E + 4 Pa · S or higher, a solar cell module using a thermoplastic sealing material sheet that does not require a crosslinking step by a heating step can be provided with necessary heat resistance. Moreover, the adhesiveness between base materials can be provided by making complex viscosity into 1.0E + 5Pa * S or less.

  And the solar cell module of this invention can fully suppress the flow of the sealing material sheet in a vacuum heating lamination by using the sealing material sheet of this invention. In addition, since there is no cross-linking step by the modularization step or the subsequent heating step, the degree of freedom of the vacuum heating laminating condition in the modularization step is increased because the cross-linking conditions need not be considered, and the time for the modularization step is also increased. Can be shortened and productivity is greatly improved. In particular, the problem of the polyethylene-based encapsulant sheet having a slower crosslinking rate than that of EVA can be solved, and the modularization time can be greatly shortened.

  In the solar cell module 1 of the present invention, the transparent front substrate 2, the solar cell element 4 and the back surface protection sheet 6 which are members other than the front sealing material layer 3 and the back sealing material layer 5 are made of conventionally known materials. It can be used without particular limitation. Moreover, the solar cell module 1 of this invention may also contain members other than the said member. In addition, the manufacturing method of the solar cell module of this invention is applicable to manufacture of not only a single crystal type but a thin film type and other solar cell modules.

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

<Manufacture of sealing material sheet>
An encapsulant composition having the following composition was mixed and melted, and formed into a film having a thickness of 400 μm by a conventional T-die method to obtain uncrosslinked encapsulant sheets of Examples and Comparative Examples. . However, for Comparative Example 3, a crosslinked encapsulant sheet having a very weak degree of crosslinking was obtained by advancing the crosslinking reaction in a limited manner during film formation by extrusion molding at 220 ° C.

(Base resin)
Sealed by mixing and melting 75 parts by mass of either of the following two LLDPEs (resin M1 (high MFR) or M2 (low MFR)) with different MFRs and 25 parts by mass of a silane-modified polyethylene resin (resin S) The base resin of the stopping material composition was used.
LLDPE (Resin M1)
: Polyethylene resin (LLDPE). 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. Number average molecular weight 55,000 in terms of polystyrene.
LLDPE (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 ³ g / 10 min. Number average molecular weight 100,000 in terms of polystyrene.
LLDPE (Resin M3)
: Polyethylene resin (LLDPE): A metallocene linear low density polyethylene which is a copolymer of ethylene and 1-hexene and has a density of 0.900 g / cm ³ and MFR of 2 g / 10 min. Number average molecular weight of 120,000 in terms of polystyrene.
Silane-modified polyethylene resin (resin S1)
A copolymer of ethylene and 1-hexene, a metallocene linear low density polyethylene resin having a density of 0.880 g / cm ³ and a melt mass flow rate (MFR) at 190 ° C. of 30 g / 10 min, 98 Density obtained by mixing 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) with respect to parts by mass, and melting and kneading at 200 ° C. Silane-modified polyethylene resin having 0.884 g / cm ³ and MFR of 18 g / 10 min. Number average molecular weight 82,000 in terms of polystyrene.
Silane-modified polyethylene resin (resin S2)
A copolymer of ethylene and 1-hexene, a metallocene linear low density polyethylene resin having a density of 0.880 g / cm ³ and a melt mass flow rate (MFR) at 190 ° C. of 3 g / 10 min, 98 Density obtained by mixing 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) with respect to parts by mass, and melting and kneading at 200 ° C. Silane-modified polyethylene resin having 0.884 g / cm ³ and MFR of 2 g / 10 min. Number average molecular weight 110000 in terms of polystyrene.
(Crosslinking aid)
1,6 hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name A-HD-N) was used as a crosslinking aid, and the amounts (parts by mass) shown in Table 1 were added.
(Crosslinking agent)
2,5 dimethyl 2,5 di (t-butylperoxy) hexane (manufactured by Arkema Yoshitomi Co., Ltd., trade name Luperox 101) was used as a cross-linking agent, and the encapsulant compositions of Examples, Comparative Examples, and Reference Examples The amount (parts by mass) shown in Table 1 was added to each.
(Adhesion improver)
A silane coupling agent was used as an adhesion improver. As the silane coupling agent, 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM503) was used, and the amounts (parts by mass) shown in Table 1 were added.
(Other additives)
0.25 mass part of UV absorbers (Kemipro Kasei Co., Ltd., trade name KEMISORB12) were added to the sealing material compositions of all Examples, Comparative Examples, and Reference Examples.
0.6 parts by mass of a weathering stabilizer (manufactured by Ciba Japan Co., Ltd., trade name Tinuvin 770) was added to the sealing material compositions of all Examples, Comparative Examples, and Reference Examples.
An antioxidant (trade name: Irganox 1076, manufactured by Ciba Japan Co., Ltd.) was added to 0.05 parts by mass of the sealing material compositions of all Examples, Comparative Examples, and Reference Examples.

  MFR of the sealing material composition of each example and comparative example was measured. In this measurement, in order to eliminate the influence of the progress of cross-linking at the time of measurement, the MFR value of each encapsulant composition was determined as the MFR value for each encapsulant composition from which the cross-linking agent component was excluded. It was. The results are shown in Table 1. In addition, about the sealing material composition of the comparative example 3 which advances some bridge | crosslinking at the time of film-forming, MFR after extrusion molding was 0.2 g / 10min. The definition of MFR is as described above.

  Embodiments for carrying out the invention described above for the non-crosslinked encapsulant sheet after film formation in each of Examples and Comparative Examples (for Comparative Example 3, encapsulating sheet in which limited crosslinking has progressed during film formation) The gel fraction was measured by the method described in, and the measurement result was defined as a gel fraction of 1. The results are shown in Table 2. The definition of the gel fraction of 0% is as described above.

  Next, about the uncrosslinked sealing material sheet | seat of Examples 1-6 and Comparative Examples 2-3, 6-7, by the irradiation of ionizing radiation on the bridge | crosslinking conditions (ionizing radiation (EB) irradiation intensity) shown in Table 1. Crosslinking treatment was performed to obtain a crosslinked encapsulant sheet. Irradiation with ionizing radiation was performed on both surfaces of the sealing material sheet with the strength shown in Table 1. However, about the comparative example 3, only the single side | surface of the sealing material sheet was irradiated with ionizing radiation with the intensity | strength shown in Table 1, and also the bridge | crosslinking process which advances bridge | crosslinking was performed. In addition, the sealing material sheet | seat of the said Examples 1-6 and Comparative Examples 2-3, 6-7 is a type of sealing material with which bridge | crosslinking by irradiation of ionizing radiation advances before integration as a solar cell module. This is assumed as a sample of the sheet.

  The uncrosslinked encapsulant sheet of Comparative Example 4 was subjected to a thermal crosslinking treatment with an oven under the crosslinking conditions (temperature, time) shown in Table 1 to obtain a crosslinked encapsulant sheet. The encapsulant sheet of Comparative Example 4 is assumed as a sample of a thermosetting encapsulant sheet that undergoes crosslinking during vacuum lamination during integration as a solar cell module.

  The uncrosslinked sealing material sheets of Comparative Examples 1 and 5 were not subjected to crosslinking treatment.

  About the sealing material sheet of an Example and a comparative example, about the bridge | crosslinking sealing material sheet which performed the crosslinking process on the conditions as shown above, the gel fraction after the said crosslinking process is measured, respectively, and a measurement result is a gel content. The rate was 2. The results are shown in Table 2.

Moreover, about the sealing material sheet of an Example and a comparative example, the heat processing was further performed after each said bridge | crosslinking process. The heat treatment was performed by vacuum heating laminator treatment with a laminator with an encapsulant sheet sandwiched between Aflex ETFE 100 μ made by Asahi Glass. The thermal lamination conditions were as follows (a) to (d). According to the thermal laminating treatment under the following thermal laminating conditions (a) to (d), the resin temperature of the encapsulant sheet becomes 140 ° C. or higher after 2 minutes, and then held at a temperature of 140 ° C. or higher and 150 ° C. or lower for 6 minutes. Will be. In addition, the progress degree of the bridge | crosslinking at the time of a vacuum heating laminator process is decided by the temperature and heating time of a sealing material sheet, and is not influenced by pressurization conditions.
[Heat laminating conditions] (a) Vacuum drawing: 5.0 minutes
(B) Pressurization (0 kPa to 100 kPa): 1.5 minutes
(C) Pressure holding (100 kPa): 8.0 minutes
(D) Temperature 150 ° C

  In addition, the displacement of the encapsulant sheet resin temperature with the passage of time is, as described above, a temperature sensor thermocouple (ST-14K-060-) at the upper part of the central part of the encapsulant sheet sandwiched between ETFEs. GW5.0-ANP) pasted with ASONE Kapton tape (P-221 12.7mm width 5-5018-01), and temperature profile was measured using temperature / humidity data logger (Ondotori TR-72Ui) It is.

<Complex viscosity>
About the sealing material sheet | seat after film forming of an Example and a comparative example, the complex viscosity for each resin temperature was measured with the following method. The results are shown in FIG.

[Test method for complex viscosity]
The complex viscosity was measured using a rotary rheometer (MCR301 manufactured by Anton Paar), parallel plate geometry (diameter 8 mm), stress 0.5 N, strain 5%, angular velocity 0.1 (1 / s), heating rate 5 The measurement was performed under the condition of ° C / min.

The complex viscosity in each of the following temperature ranges is all within the following complex viscosity range, and A is at least in the temperature range of 180 ° C. or higher and 200 ° C. or lower. In any other temperature range, B is not in the following complex viscosity range, B is in the temperature range of 180 ° C. to 200 ° C. and the complex viscosity is not in the following complex viscosity range, and C is in each case. These are shown in the column of complex viscosity in Table 2.
The complex viscosity at 100 ° C. or higher and 110 ° C. or lower is 5.0E + 4 Pa · S or higher and 5.0E + 5 Pa · S or lower.
The complex viscosity at 140 ° C. to 150 ° C. is 5.0E + 4 Pa · S to 3.0E + 5 Pa · S.
The complex viscosity at 180 ° C. or more and 200 ° C. or less is 3.0E + 4 Pa · S or more and 1.0E + 5 Pa · S or less.

<Evaluation Example 1>
The sealing material sheets of Examples and Comparative Examples cut to 5.0 × 5.0 cm were respectively laminated on a glass substrate (blue plate glass 150 mm × 150 mm × 3.0 mm), and further on the glass substrate. In a state where the layers were laminated, a vacuum heating laminator treatment was performed, the enlargement ratio of each sealing material sheet after the treatment was measured, and processing suitability (laminate suitability) was evaluated.
[Expansion rate (%) test method]
The length of the line drawn in a cross shape at the center of the square sealing material sheet (the value indicated by the diameter of the smallest circle including the cross shape) is the length when compared before and after the lamination process. The ratio was measured and this value was taken as the magnification. The heat laminating conditions were the same as the above (a) to (d). The measurement results for each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.
A: Less than 110% B: 110% or more and less than 125% C: 125% or more

<Evaluation Example 2>
The sealing material sheets of Examples and Comparative Examples cut to 5.0 × 5.0 cm were respectively laminated on a glass substrate (blue plate glass 150 mm × 150 mm × 3.0 mm), and further on the glass substrate. In a state where the layers were laminated, a vacuum heating laminator treatment was performed, a change in film pressure of each sealing material sheet after the treatment was measured, and processing suitability (laminate suitability) was evaluated.
[Test method of membrane pressure change rate (%)]
The sample of the square sealing material sheet after the vacuum heating laminator treatment was measured for a thickness ratio when the sample was compared before and after the lamination treatment, and this value was defined as the rate of change in membrane pressure. The heat laminating conditions were the same as the above (a) to (d). The measurement results for each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.
A: Less than 5% B: 5% or more and less than 10% C: 10% or more

<Evaluation Example 3>
Two sealing material sheets of Examples and Comparative Examples cut to 7.5 × 5.0 cm are placed on a glass substrate (white float semi-tempered glass JPT3.2 150 mm × 150 mm × 3.2 mm), and the top A glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) is stacked and subjected to vacuum heating laminator treatment under the same heat laminating conditions as in Evaluation Example 1, and each example and comparative example A battery module evaluation sample was obtained. These solar cell module evaluation samples were subjected to a heat-resistant creep test under the following test conditions to evaluate heat resistance.
[Test method for heat-resistant creep test (mm)]
The solar cell module evaluation sample was placed vertically and allowed to stand at 140 ° C. for 12 hours, and the moving distance of the glass substrate (white plate semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) after being left was measured and evaluated. . The measurement results for each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.
A: Less than 1.2 mm B: 1.2 mm or more and less than 2.5 mm C: 2.5 mm or more

<Evaluation Example 4>
The volume resistance values of the sealing material sheets of Examples and Comparative Examples molded with a thickness of 400 μm were measured by the following methods to evaluate the insulating properties.
[Test method for volume resistance (Ω)]
About said sealing material sheet | seat, the volume resistance value was measured by JISC6481. As a measuring instrument, a super insulation meter (manufactured by Hioki Electric Co., Ltd .: model number SM-8215) was used. The measurement results for each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.
A: 1.0E + 15Ω or more B: 7.0E + 14Ω or more and less than 1.0E + 15Ω C: less than 7.0E + 14Ω

<Evaluation Example 5>
The same heat laminate as in Evaluation Example 1 was prepared by sticking the sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm onto glass substrates (white float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm). Under the conditions, a vacuum heating laminator treatment was performed, and solar cell module evaluation samples were obtained for the respective examples and comparative examples. About these solar cell module evaluation samples, the glass adhesion rejection under the following test conditions was measured to evaluate the glass adhesion. The results are shown in Table 3.
[Test method for glass adhesion strength (N / 15 mm)]
Peeling test method: In the above solar cell module evaluation sample, the sealing material sheet in close contact with the glass substrate was vertically peeled (50 mm / min) with a peeling tester (Tensilon Universal Tester RTF-1150-H). A test was conducted to measure the glass adhesion strength. The measurement results for each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3.
A: 30 N / 15 mm or more B: 25 N / 15 mm or more and less than 30 N / 15 mm C: Less than 25 N / 15 mm

  From Tables 1 to 3 and FIG. 2, the sealing material sheet of the solar cell module of the present invention in which the complex viscosity of the sealing material layer is within a predetermined range has a good balance between laminate suitability and heat resistance. It turns out that it is a sealing material sheet superior to each sealing material sheet of the comparative example whose complex viscosity is outside a predetermined range.

  From Tables 1-3, it turns out that the sealing material sheet | seat of this invention is a sealing material sheet | seat which also has sufficient adhesiveness with respect to the glass which is the main material of the structural member of a solar cell module. In addition, also about adhesiveness with another base material, it is thought that adhesiveness can be improved by adjusting suitably the irradiation conditions of ionizing radiation for every base material to laminate | stack.

  As mentioned above, the sealing material sheet for solar cell modules of this invention can be obtained by forming the sealing material composition containing a crosslinking adjuvant into a film, and performing the crosslinking process by irradiation of ionizing radiation before modularization. However, by optimizing the complex viscosity of the encapsulant layer within a predetermined range, it can be seen that it has various physical properties preferable as an encapsulant sheet for a solar cell module.

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 (1)

A sheet forming step of obtaining an uncrosslinked encapsulant sheet by melt-molding an encapsulant composition containing a density of 0.900 g / cm ³ or less, low density polyethylene, and a crosslinking aid;
Said uncrosslinked sealing material sheet, the gel fraction by the irradiation of ionizing radiation Ri Do 80% less than 2%, complex viscosity crosslinking treatment range as such so that the following (1) to (3) A crosslinking step,
The sealing material composition has an MFR at 190 ° C. and a load of 2.16 kg measured according to JIS K6922-2 of 20.0 g / 10 min to 40.0 g / 10 min.
In the sealing material composition, the content of the crosslinking aid is 0.1 parts by mass or more and less than 0.5 parts by mass with respect to 100 parts by mass of all components,
The said sealing material composition is a manufacturing method of the sealing material sheet for solar cell modules which does not contain a crosslinking agent .
(1) Complex viscosity at 100 ° C to 110 ° C: 5.0E + 4Pa · S to 5.0E + 5Pa · S
(2) Complex viscosity at 140 ° C. or higher and 150 ° C. or lower: 5.0E + 4 Pa · S or higher and 3.0E + 5 Pa · S or lower
(3) Complex viscosity at 180 ° C. or higher and 200 ° C. or lower: 3.0E + 4 Pa · S or higher and 1.0E + 5 Pa · S or lower

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