JP6686430B2 - Encapsulant sheet for solar cell module and solar cell module using the same - Google Patents

Description

  The present invention relates to a sealing material sheet for a solar cell module and a solar cell module using the same. More specifically, the present invention relates to a sealing material sheet that can be suitably used for a solar cell module having a thin film solar cell element mounted thereon (hereinafter, also referred to as “thin film solar cell module”), and a solar cell module using the same.

  2. Description of the Related Art In recent years, solar cells have been attracting attention as a clean energy source because of increasing awareness of environmental problems. At present, various types of solar cell modules have been developed and proposed. Generally, a solar cell module has a configuration in which a transparent front substrate made of glass or the like, a solar cell element, and a back surface protection sheet are laminated with a sealing material sheet interposed therebetween.

  As the encapsulant sheet used for the solar cell module, ethylene-vinyl acetate copolymer resin (EVA) has been used as a conventional ordinary one from the viewpoints of workability, workability, manufacturing cost, etc. However, the EVA resin tends to be gradually decomposed with long-term use and may generate acetic acid gas which affects the solar cell element. For this reason, in recent years, the demand for a sealing material sheet for a solar cell module using a polyethylene resin-based resin instead of the EVA resin is increasing (see Patent Document 1).

  In general, in a sealing material sheet for a solar cell module using a polyethylene resin as a base resin, transparency and flexibility can be improved by making the density low. However, lowering the density causes a problem of insufficient heat resistance. On the other hand, when high-density polyethylene (HDLD), which has excellent heat resistance, is used, it becomes impossible to maintain the conformability to the irregularities on the surface of the facing member (hereinafter referred to as “molding characteristics”) when modularized. In addition, there is a problem that the molding state (wraparound) in the initial state cannot be sufficiently maintained even when used under a high temperature for a long time as described above. In the present specification, the physical properties required to maintain the molding state in the above-described harsh environment are referred to as “molding durability” hereinafter.

  In the encapsulant sheet of Patent Document 1, the crosslinking agent imparts heat resistance and flame retardancy to the low-density polyethylene resin. In this case, the heat resistance is certainly improved, but if a sufficient degree of cross-linking treatment is performed to provide heat resistance sufficient to withstand use at high temperatures for a long period of time, a large amount of decomposition of the cross-linking agent will occur. This causes problems such as deterioration of the solar cell element due to objects, and defects due to generation of bubbles in the encapsulating material layer. Also, in the manufacturing process that requires a cross-linking treatment, the film-forming property deteriorates if the cross-linking progresses during molding.Therefore, it is necessary to consider that the molding is performed at a low temperature and the cross-linking reaction is performed again after the molding. In terms of sex, further improvement was required.

  Here, in the solar cell element, in addition to a crystalline silicon solar cell manufactured by using a single crystal silicon substrate or a polycrystalline silicon substrate, amorphous silicon or microcrystalline silicon is provided on a substrate such as glass with a pole of about 1 μm or less. There is a thin film type solar cell element formed by molding a thin silicon film. In a solar cell module using a thin-film solar cell element, which has been in increasing demand in recent years, compatibility between the heat resistance and the molding durability is required at a particularly high level. The problem of compatibility between heat resistance and molding durability has been a common problem to be solved in all solar cell modules, but in particular, it has been a serious problem in thin-film solar cell modules.

  For example, in order to achieve both heat resistance and molding properties without cross-linking treatment, a skin layer in which two or more kinds of resins having different melting points are mixed and a crystal nucleating agent such as inorganic particles are added to the sealing layer. A multi-layered sheet in which a core layer composed of a stopping material composition is combined with the core layer, thereby encapsulating a solar cell module which has both flexibility and heat resistance while requiring no crosslinking treatment. A material sheet is disclosed (see Patent Document 2).

JP, 2009-10277, A International Publication No. 2012/073971

Like the encapsulant sheet described in Patent Document 1, in the production of an encapsulant sheet using a low-density polyethylene-based resin having a density of 0.900 g / cm ³ or less as a base resin, heat treatment is performed by a crosslinking treatment. A manufacturing method that compensates for the shortage is widely used.At this time, the progress of crosslinking is controlled by adjusting the addition amount of the crosslinking agent and optimizing the crosslinking treatment conditions such as the heating temperature and the ionizing irradiation dose. ing.

However, for example, by using a polyethylene resin having a relatively high density of about 0.910 g / cm ³ or more as the base resin of the encapsulating material composition, the required heat resistance can be obtained without undergoing a crosslinking treatment. In the thermoplastic encapsulant sheet that is supposed to be secured, it is necessary to ensure both the heat resistance of the finished product and the molding durability at the stage of selecting the material resin. A versatile selection criterion has not yet been established for selecting a material resin to meet the requirements.

  On the other hand, the encapsulant sheet described in Patent Document 2 essentially requires a laminated body having a multi-layer structure, and further limits the combination of each of these layers to a special configuration, thereby attempting to solve the above problems. It is a thing. As the encapsulant composition used for the skin layer, a special ethylene-α-copolymer having different heat resistance characteristics from general-purpose polyethylene resin generally widely distributed is selected, and the core layer thereof is The addition of a crystal nucleating agent is essential. In this way, by limiting the materials and their combinations, and the laminated structure as a multilayer body to a special range different from general-purpose products, the balance between flexibility and heat resistance is ensured for the entire encapsulant sheet. It is a thing.

  Therefore, even if the encapsulant sheet described in Patent Document 2 can overcome the above-mentioned problems, an increase in production cost accompanying it is inevitable. In order to spread solar cells aiming to contribute to energy problems, demands for cost reduction of solar cell modules are still strong, and encapsulant sheets made of polyethylene resin are not enough to have the required physical properties. There is also a strong demand for high productivity. In this respect, the encapsulant sheet described in Patent Document 3 has a problem in terms of productivity, and a drastic improvement measure for cost reduction has been sought. Further, even if the encapsulant sheet described in Patent Document 2 has molding characteristics in the initial stage after manufacturing, molding durability that enhances reliability during use under the severe conditions as described above. There was still room for improvement in terms of whether or not the above can be sufficiently maintained.

The present invention has been made in view of the above circumstances, and is a sealing material sheet using a polyethylene-based resin, the productivity is high without a crosslinking step, and heat resistance and molding durability. It is an object of the present invention to provide a sealing material sheet for a solar cell module that has a high standard.

  As a result of earnest studies, the present inventors have determined that the encapsulant sheet is a multi-layer sheet having a three-layer structure in which a skin layer, a core layer, and a skin layer are laminated in this order, and a polyethylene resin having a predetermined density is used as a base. If the encapsulant sheet is made of a resin and further includes a core layer containing an elastic modulus lowering additive capable of lowering the storage elastic modulus, excellent encapsulating property can be obtained without any crosslinking treatment. The inventors have found that molding durability can be exhibited, and completed the present invention. More specifically, the present invention provides the following.

(1) A multilayer encapsulating material sheet configured by a plurality of layers including a core layer and skin layers arranged on both outermost layers of the encapsulating material sheet,
The core layer uses a polyethylene resin having a density of 0.910 g / cm ³ or more and 0.930 g / cm ³ or less as a base resin, and 2% by mass or more and 50% by mass of an elastic modulus lowering additive having a smaller molecular weight than the base resin. % Or less, the storage elastic modulus (E ′) at 85 ° C. is 1.0 × 10 ⁶ Pa or more and 2.0 × 10 ⁷ Pa or less,
The skin layer are both total thickness of the skin layer and the density of 0.890 g / cm ³ or more 0.910 g / cm ³ or less of the polyethylene resin and base resin, the total thickness of the sealing member 1 A sealing material sheet for a solar cell module, which is / 20 or more and 1/3 or less.

  (2) The encapsulant sheet according to (1), wherein the elastic modulus lowering additive is an elastomer and / or a mineral oil.

  (3) The sealing according to (1) or (2), wherein the elastic modulus lowering additive is an elastomer, and the content of the elastomer in the core layer is 15% by mass or more and 45% by mass or less. Material sheet.

(4) The encapsulant sheet according to any one of (1) to (3), wherein the core layer has a storage elastic modulus at 85 ° C. of 5.0 × 10 ⁶ Pa or less.

(5) A thin-film solar cell module comprising the encapsulant sheet according to any one of (1) to (4) and a thin-film solar cell element laminated on a glass substrate. ,
A solar cell module comprising a configuration in which the glass substrate and the solar cell element are in close contact with each other on the same surface of the encapsulant sheet.

(6) A lead wire for collecting current is formed on the surface of the solar cell element, and the lead wire is embedded inside the encapsulant sheet,
The solar cell module according to (5), wherein the thickness of the lead wire is 50% or more and 90% or less of the thickness of the encapsulant sheet on the surface of the solar cell element.

  According to the present invention, although the encapsulant sheet is made of a polyethylene-based resin, a cross-linking step is unnecessary, the productivity is high, and the solar cell module has a high level of heat resistance and molding durability. A sealing material sheet can be provided.

It is sectional drawing which shows typically the laminated constitution of the sealing material sheet of this invention. 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, and a thin film type solar cell element. FIG. 3 is a partially enlarged view of FIG. 2 and is a drawing for explaining molding durability of the encapsulant sheet of the present invention when used in a thin film solar cell module. It is a partial expanded sectional view of the conventional solar cell module which used the conventional sealing material sheet inferior to molding durability for the thin film solar cell module.

  Hereinafter, a sealing material composition that can be preferably used in a sealing material sheet for a solar cell module of the present invention, a sealing material sheet for a solar cell module, and a solar cell using the sealing material sheet of the present invention The modules will be sequentially described. In the present specification, the skin layer refers to a layer disposed on both outermost surface sides of the multilayer encapsulant sheet, and the core layer refers to an intermediate layer other than the skin layer. A three-layer structure in which the core layer has a single-layer structure is a typical embodiment of the present invention, but the core layer itself may have a multi-layer structure composed of a plurality of layers.

<Sealing material composition>
The encapsulant sheet of the present invention can be produced by melt-molding the encapsulant composition described in detail below. As the encapsulating material composition, the encapsulating material composition for the core layer and the encapsulating material composition for the skin layer are separately used for forming each layer. Then, a multi-layered sheet having a three-layer structure in which skin layers are arranged on both outermost surfaces is formed with a predetermined layer thickness and thickness ratio using each of the encapsulant compositions for the core layer and the skin layer. Thereby, the encapsulant sheet of the present invention represented by the encapsulant sheet 1 shown in FIG. 1, for example, can be manufactured. In the present specification, the skin layer means a layer arranged on both outermost surface sides of the multilayer encapsulating material sheet, and the core layer means an inner layer other than the skin layer in the multi-layer encapsulating material sheet. Say that. The core layer itself may have a multilayer internal structure, but a three-layer structure encapsulating material sheet 1 in which skin layers are laminated on both surfaces of a single-layer core layer is a typical example of the present invention. The present invention will be described below centering on the encapsulant sheet 1.

[Encapsulating material composition for core layer]
The encapsulant composition for core layer is a resin composition used for molding the core layer of the encapsulant sheet of the present invention. As the encapsulating material composition for the core layer, a polyethylene resin of 0.910 g / cm ³ or more and 0.930 g / cm ³ or less is used as a base resin. Further, the elastic modulus lowering additive is contained in the range of 2% by mass or more and 50% by mass or less based on the total amount of the sealing material composition. In the present specification, the base resin refers to a resin that is contained in an amount of 50% by mass or more and 100% by mass or less of the total resin components in the encapsulating material composition.

Here, the elastic modulus lowering additive is an additive having a function of lowering the storage elastic modulus of the core layer formed by the encapsulating composition by being contained in the encapsulating composition. Say something. An encapsulant sheet using a core layer formed of the encapsulant composition containing the above-mentioned polyethylene resin of 0.910 g / cm ³ or more and 0.930 g / cm ³ or less and an additive for lowering the elastic modulus. In this case, the encapsulating material sheet can have a high level of both heat resistance and molding durability. In the case of using the encapsulant composition containing a polyethylene resin of 0.910 g / cm ³ or more and 0.930 g / cm ³ or less, which does not require a crosslinking treatment, as in the present invention, an additive for further lowering the elastic modulus is used. By containing 2 to 50 mass% of the total amount of the encapsulant composition, it is possible to achieve both heat resistance and molding durability that were difficult to optimize at an extremely high level. The finding that it is possible is a new finding unique to the present inventors.

(Polyethylene resin)
The base resin used in the encapsulant composition for the core layer according to the present embodiment is a polyethylene-based resin of 0.910 g / cm ³ or more and 0.930 g / cm ³ or less. The content of the polyethylene resin, which is the base resin for the core layer, contained in the encapsulant composition for the core layer is preferably 60 mass with respect to all the resin components in the encapsulant composition for the core layer. % To 99% by mass, more preferably 65% to 99% by mass, still more preferably 70% to 99% by mass. These may be used, for example, as a resin for addition, or may be used as another resin for masterbatching other additive components. In addition, in this specification, the term "all resin components" includes the above-mentioned other resins. The core layer encapsulant composition is a thermoplastic encapsulant composition that does not contain a cross-linking agent and does not require a cross-linking step when molding the encapsulant sheet.

The polyethylene-based resin used as the base resin of the encapsulating material composition for the core layer is 0.910 g / cm ³ or more and 0.930 g / cm ³ or less, more preferably 0.910 g / cm ³ or more 0. Polyethylene-based resin of 0.920 g / cm ³ or less can be used. By setting the density of the base resin of the encapsulant composition for the core layer within the above range, the heat resistance of the encapsulant sheet can be sufficiently improved.

  The melting point of the polyethylene-based resin used as the base resin of the encapsulant composition for the core layer is preferably 100 ° C. or higher and 120 ° C. or lower, and more preferably 100 ° C. or higher and 110 ° C. or lower. By setting the melting point of the base resin of the encapsulant composition for the core layer within the above melting point range, the heat resistance and the molding durability of the encapsulant sheet can be maintained within a generally preferable range.

  The melt mass flow rate (MFR) of the high melting point polyethylene resin used as the base resin of the encapsulant composition for the core layer is 190 g and a load of 2.16 kg, and is 2.0 g / 10 minutes or more and 7.5 g / 10 minutes or less. Is preferable, and more preferably 3.0 g / 10 minutes or more and 6.0 g / 10 minutes or less. By setting the MFR of the base resin of the encapsulant composition for the core layer in the above range, the heat resistance and the molding durability of the encapsulant sheet can be maintained within generally preferable ranges. Further, it is possible to sufficiently enhance the processability during film formation and contribute to the improvement of the productivity of the encapsulant sheet.

The MFR in the present specification is a value obtained by the following method unless otherwise specified.
MFR (g / 10min): Measured according to JIS K7210. Specifically, the synthetic resin was heated and pressurized at 190 ° C. in a cylindrical container heated by a heater, and the amount of resin extruded from an opening (nozzle) provided at the bottom of the container per 10 minutes was measured. . An extrusion type plastometer was used as the test machine, and the extrusion load was 2.16 kg. The MFR of the multi-layered encapsulant sheet was measured by the above-mentioned treatment in the multi-layered state in which all layers were integrally laminated, and the obtained measurement value was taken as the MFR value of the multi-layered encapsulant sheet.

(Additives for lowering elastic modulus)
The elastic modulus lowering additive is an additive having a function of lowering the storage elastic modulus at 85 ° C. of the core layer formed by the encapsulating material composition, by being contained in the encapsulating material composition. Say something. The elastic modulus lowering additive is such that the core layer of the encapsulant sheet to be formed has a storage elastic modulus (E ′) at 85 ° C. of 1.0 × 10 ⁶ Pa or more and 2.0 × 10 ⁷ Pa or less. There is no particular limitation as long as it is an additive. For example, a polyethylene resin having a lower melting point or a lower molecular weight than a polyethylene resin used as a base resin, an elastomer having a storage elastic modulus (E ′) at 85 ° C. lower than that of a polyethylene resin used as a base resin, or a base resin Examples thereof include mineral oils that can reduce the storage elastic modulus (E ') of the polyethylene resin used.

  The elastic modulus lowering additive contained in the encapsulant composition for the core layer of the encapsulant sheet is preferably an elastomer and / or a mineral oil. By containing the elastomer and / or the mineral oil, not only the storage elastic modulus (E ′) of the core layer at 85 ° C. but also the storage elastic modulus (E ′) at low temperature can be lowered. Therefore, it is possible to obtain a sealing material sheet having further excellent molding durability.

  When a polyethylene resin having a lower melting point or a lower molecular weight than the base resin is used as the elastic modulus lowering additive, it is preferable to use a polyethylene resin having a melting point of 55 ° C. or higher and 95 ° C. or lower as the elastic modulus lowering additive. By including a polyethylene resin having a melting point of 55 ° C. or higher and 95 ° C. or lower in the encapsulating material composition for the core layer, the storage elastic modulus (E ′) of the core layer at 85 ° C. can be reduced. The content of the elastic modulus lowering additive is 2% by mass or more and 50% by mass or less, preferably 8% by mass or more and 30% by mass or less, based on all resin components in the encapsulant composition for the core layer. . These may be used, for example, as a resin for addition, or may be used as another resin for masterbatching other additive components.

When a polyethylene resin having a lower melting point or a lower molecular weight than the base resin is used as the elastic modulus lowering additive, the density of the polyethylene resin having a lower melting point or a lower molecular weight is 0.870 g / cm ³ or more and 0.900 g / cm ³ or more. preferably ³ or less, and more preferably less 0.880 g / cm ³ or more 0.900 g / cm ^3. By setting the melting point of the encapsulating material composition for the core layer or the density of the polyethylene resin having a low molecular weight in the above range, the storage elastic modulus (E ′) of the core layer at 85 ° C. is reduced, and The molding durability can be sufficiently improved.

  When a polyethylene resin having a lower melting point or a lower molecular weight than the base resin is used as the elastic modulus lowering additive, the melting point of the low melting point polyethylene resin of the encapsulating material composition for the core layer is 50 ° C. or higher and 90 ° C. or lower. Is preferable, and more preferably 60 ° C. or higher and 90 ° C. or lower. By setting the melting point of the low melting point polyethylene-based resin of the encapsulant composition for the core layer in the above melting point range, the heat resistance and molding durability of the encapsulant sheet can be maintained within a generally preferable range. .

  When a polyethylene resin having a lower melting point or a lower molecular weight than the base resin is used as the elastic modulus lowering additive, the melt mass flow rate (MFR) of the low melting point polyethylene resin of the encapsulating material composition for the core layer is 190. It is preferably 2.0 g / 10 minutes or more and 7.5 g / 10 minutes or less at 0 ° C. and a load of 2.16 kg, and more preferably 3.0 g / 10 minutes or more and 6.0 g / 10 minutes or less. Keeping the heat resistance and the molding durability of the encapsulant sheet within a generally preferable range by setting the melting point of the encapsulant composition for the core layer or the MFR of the low molecular weight polyethylene resin to the above range. You can Further, it is possible to sufficiently enhance the processability during film formation and contribute to the improvement of the productivity of the encapsulant sheet.

When an elastomer is used as the elastic modulus lowering additive, it is preferable to use an elastomer having a storage elastic modulus at 85 ° C. of 1.0 × 10 ⁵ Pa or more and 5.0 × 10 ⁶ Pa or less.

  The elastomer used as the additive for lowering the elastic modulus is not particularly limited. Examples thereof include ethylene-propylene rubbers such as sulfurized rubber) and Esporex (manufactured by Sumitomo Chemical Co., Ltd.).

  When an ethylene-propylene rubber such as EPM or EPDM is used as an elastic modulus lowering additive, the density of the ethylene-propylene rubber decreases as the polymerization ratio of ethylene and propylene approaches 1: 1 and the storage elastic modulus ( It becomes an ethylene-propylene rubber having a low E ′). Therefore, the proportion of ethylene in the total amount of ethylene-propylene rubber is preferably 30% or more and 70% or less, more preferably 40% or more and 60% or less, and further preferably 45% or more and 55% or less.

  When an elastomer is used as the elastic modulus lowering additive, the content of the elastomer is 15% by mass or more and 45% by mass or less, preferably 20% by mass or less with respect to the total resin component in the encapsulant composition for the core layer. It is from 40% by mass to 40% by mass. Further, the elastomer preferably further contains mineral oil. By containing the elastomer and the mineral oil, the storage elastic modulus (E ′) at 85 ° C. and the storage elastic modulus (E ′) at low temperature of the core layer can also be reduced.

When mineral oil is used as the elastic modulus lowering additive, known mineral oil that can be generally used for resins, elastomers and the like can be used. For example, paraffin oil such as Diana Process Oil PW380 (manufactured by Idemitsu Kosan Co., Ltd., Mw = 750, Mw / Mn = 1.15, kinematic viscosity (40 ° C.) = 380 mm ² / S) can be mentioned. By using mineral oil as the elastic modulus lowering additive, it is possible to lower the storage elastic modulus (E ′) itself of the polyethylene resin used as the base resin.

  When a mineral oil is used as the elastic modulus lowering additive, the content of the mineral oil is preferably 2% by mass or more and 20% by mass or less, and more preferably 20% by mass or less, based on all resin components in the encapsulant composition for the core layer. Is 3% by mass or more and 15% by mass or less.

[Sealant composition for skin layer]
The encapsulant composition for the skin layer is a resin composition used for forming the skin layer of the encapsulant sheet of the present invention. As the encapsulant composition for the skin layer, conventionally, as the encapsulant composition for the solar cell module, a density of 0.890 g which is usually used by performing a treatment for improving heat resistance by a crosslinking treatment or the like. / Cm ³ or more and 0.910 g / cm ³ or less of a polyethylene resin is used as a base resin.

  The content of the base resin for the skin layer contained in the encapsulant composition for the skin layer is preferably 60% by mass or more and 99% by mass or more based on all the resin components in the encapsulant composition for the skin layer. The amount is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less. These may be used, for example, as a resin for addition, or may be used as another resin for masterbatching other additive components.

  The polyethylene resin used as the base resin of the encapsulant composition for the skin layer is a low density polyethylene resin (LDPE), a linear low density polyethylene resin (LLDPE), or a metallocene linear low density polyethylene resin. (M-LLDPE) can be preferably used.

Density polyethylene resin used as the base resin of the sealing material composition for the skin layer is a density 0.890 g / cm ³ or more 0.910 g / cm ³ or less, more preferably, 0.890 g / cm ³ or more It is 0.900 g / cm ³ or less. The melting point of the low melting point polyethylene resin used as the base resin of the encapsulant composition for the skin layer is preferably 100 ° C. or lower, more preferably 85 ° C. or higher and 95 ° C. or lower. By setting the density and the melting point of the base resin of the encapsulant composition for the skin layer within the above ranges, it is possible to sufficiently improve the adhesion of the encapsulant sheet during integration as a solar cell module.

  The polyethylene resin used as the base resin of the encapsulant composition for the skin layer has a melt mass flow rate (MFR) of 2.0 g / 10 min or more and 7.5 g / 10 min or less at 190 ° C. and a load of 2.16 kg. It is preferable that the amount is 3.0 g / 10 minutes or more and 6.0 g / 10 minutes or less. By setting the MFR of the base resin of the encapsulant composition for the skin layer in the above range, the adhesiveness of the encapsulant sheet can be kept within a preferable range. Further, it is possible to sufficiently enhance the processability during film formation and contribute to the improvement of the productivity of the encapsulant sheet.

[Other materials]
Both the encapsulating material composition for the core layer and the encapsulating material composition for the skin layer (hereinafter, also referred to as "encapsulating material composition") have α-olefin and an ethylenically unsaturated silane compound as comonomers. It is more preferable that a predetermined amount of a silane copolymer obtained by copolymerization (hereinafter, also referred to as “silane-modified polyethylene-based resin”) be contained in each encapsulating material composition, if necessary. The silane-modified polyethylene-based resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain onto a linear low-density polyethylene-based resin (LLDPE) that is a main chain. Since such a graft copolymer has a high degree of freedom of the silanol group that contributes to the adhesive force, it can improve the adhesiveness of the encapsulant sheet 1 to other members in the solar cell module. The content of the silane-modified polyethylene-based resin in the encapsulating material composition for the core layer is 2% by mass based on all resin components in the encapsulating material composition for the core layer. It is preferably 20% by mass or more and 5% by mass or more and 40% by mass or less with respect to all resin components in the encapsulating material composition for skin layer. Particularly, the encapsulant composition for the skin layer more preferably contains 10% by mass or more of the silane-modified polyethylene resin. The silane-modified amount of the silane-modified polyethylene resin is preferably 1.0% by mass or more and 3.0% by mass or less. The preferred silane-modified polyethylene-based resin content range in the encapsulant composition is based on the premise that the silane modification amount is within this range, and may be finely adjusted depending on the variation in the modification amount. Is desirable.

  The silane-modified polyethylene-based resin can be produced, for example, by the method described in JP-A-2003-46105, and by using the resin as a component of the encapsulant composition for a solar cell module, strength and durability can be improved. Etc., and excellent in weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, hail resistance, and other characteristics. Furthermore, it is affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. It is possible to manufacture a solar cell module that has excellent heat fusion properties, is stable, is low in cost, and is suitable for various applications.

  It is preferable to appropriately add an adhesion improver to the encapsulant composition. By adding the adhesion improver, the adhesion durability with other base materials can be further enhanced. As the adhesion improver, a known silane coupling agent can be used, but a silane coupling agent having an epoxy group (hereinafter, also referred to as an epoxy silane coupling agent) or a silane coupling agent having a mercapto group ( Hereinafter, a mercapto-based silane coupling agent) is particularly preferably used.

  Whichever epoxy silane coupling agent or mercapto silane coupling agent is used, the adhesion of the encapsulant sheet for a solar cell module to glass, metal, and polyamide resin can be simultaneously enhanced. . In order to achieve this object, any silane coupling agent can be preferably used.

The epoxy-based silane coupling agent, the general formula ^{[R3-Si-R4 (3} -m) R5 m] (m represents an integer of 1 to 3, R3 represents an epoxy group, R4 represents an alkyl group, R5 represents an alkoxy group), and examples thereof include β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyl. Examples include methyldiethoxysilane. These may be used alone or in combination of two or more. The epoxy silane coupling agent is not particularly limited, and a known silane coupling agent can be preferably used. For example, there are "KBM303" and "KBM-403" (both manufactured by "Shin-Etsu Silicone Co., Ltd."), which can be easily obtained from the market.

The mercapto-based silane coupling agent is represented by the general formula [R1-Si (OR2) ³ ] (R1 represents a mercaptoalkyl group and R2 represents an alkyl group), and as an example, γ- Examples thereof include mercaptopropyltrimethoxysilane, γ-mercaptomethyltrimethoxysilane and γ-mercaptoethyltrimethoxysilane. The mercapto-based silane coupling agent is not particularly limited, and a known silane coupling agent can be preferably used. For example, there is “KBM802” (manufactured by Shin-Etsu Silicone Co., Ltd.), which can be easily obtained from the market.

  The adhesion of the encapsulant sheet to the metal is improved mainly by the addition of the silane coupling agent as described above, and at that time, the silane copolymer is contained in the encapsulant composition. In addition, the glass adhesion is also sufficiently improved. By appropriately combining and adding a silane copolymer and a specific silane coupling agent to the encapsulant composition, it is possible to simultaneously improve the adhesion to metal and glass within a preferable range.

  When a silane coupling agent is added as an adhesion improver, the content thereof is 0.1% by mass or more and 10.0% by mass or less based on the total resin components of the encapsulating material composition, and the upper limit is preferable. Is 5.0 mass% or less. When the content of the silane coupling agent is in the above range, and the polyolefin resin constituting the encapsulating material composition contains an appropriate amount of the ethylenically unsaturated silane compound, the adhesiveness is in a more preferable range. And improve. In addition, if it exceeds this range, so-called bleed-out may occur in which the film-forming property is deteriorated or the silane coupling agent is aggregated and solidified over time and powdered on the surface of the sealing material sheet, which is not preferable.

  The encapsulant composition may further contain other components. For example, components such as a weather resistance masterbatch for imparting weather resistance to the encapsulant sheet, various fillers, a light stabilizer, an ultraviolet absorber, a heat stabilizer and the like are exemplified. The content of these elements varies depending on the particle shape, density, etc., but is preferably in the range of 0.001% by mass or more and 5% by mass or less in the encapsulating material composition. By including these additives, the encapsulating material sheet can be provided with stable mechanical strength for a long period of time, an effect of preventing yellowing, cracking, and the like.

<Sealing material sheet>
The encapsulating material sheet 1 has a core layer 11, and skin layers 12 are arranged on both surfaces of the core layer 11. However, even in the encapsulating material sheet in which the core layer has a multi-layer structure and other functional layers are arranged in the core layer, the core layer and the skin layer having the constituent requirements of the invention are provided, and It is within the scope of the present invention as long as it is an encapsulant sheet having other constituent features of the present invention.

  The total thickness of the encapsulant sheet 1 having a three-layer structure including the core layer 11 and the skin layer 12 is preferably 250 μm or more and 600 μm or less, and more preferably 300 μm or more and 550 μm or less. If the total thickness is less than 250 μm, the impact cannot be sufficiently mitigated, but if the total thickness is 250 μm or more, for example, even when the encapsulating material sheet 1 is thinned to a total thickness of about 250 μm. It is possible to combine molding durability and heat resistance at a sufficiently preferable level. If the total thickness exceeds 600 μm, the effect of further improving the impact relaxation effect cannot be obtained, the demand for thinning the solar cell module cannot be met, and it is uneconomical, which is not preferable.

  The thickness of the core layer 11 in the encapsulant sheet 1 is preferably 200 μm or more and 400 μm or less, more preferably 250 μm or more and 350 μm or less. The thickness of each layer of the skin layer 12 is preferably 30 μm or more and 100 μm or less, and more preferably 35 μm or more and 80 μm or less. In addition, the total thickness of the two lead wire 32 skin layers 12 laminated on both surfaces of the core layer is 1/20 or more and 1/3 or less of the total thickness of the encapsulant sheet 1, and preferably, It is not less than 1/15 and not more than 1/4. By setting the thickness of each layer of the encapsulating material sheet 1 in such a range, the heat resistance and the molding durability of the encapsulating material sheet 1 can be maintained in a good range.

In the encapsulant sheet 1, the storage elastic modulus (E ′) of 11 of the core layer is in the range of 1.0 × 10 ⁶ Pa or more and 2.0 × 10 ⁷ Pa or less, and preferably 6.5. It is in the range of × 10 ⁶ Pa or more and 1.0 × 10 ⁷ Pa. By setting the storage elastic modulus (E ′) of the core layer 11 after molding the encapsulant sheet 1 to be in the above range, the encapsulant sheet 1 has extremely high heat resistance and molding durability. It can be compatible with the standard.

  The above-mentioned encapsulant sheet is formed into a sheet by a molding method that is usually used in ordinary thermoplastic resins, that is, various molding methods such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. As an example of a method for forming a sheet when the encapsulating material sheet is a multi-layer film, there is a method of forming by coextrusion with three types of melt-kneading extruders.

  However, in any of the above molding methods, the melt molding temperature in the production of the encapsulant sheet 1 is equal to or higher than the melting point of the base resin of the encapsulant composition for the core layer contained in the encapsulant composition + 30 ° C or more. Is preferred. Specifically, the temperature is preferably 175 ° C. or higher and 230 ° C. or lower, and more preferably 190 ° C. or higher and 210 ° C. or lower. Since the encapsulant composition used for the encapsulant sheet 1 is a thermoplastic composition that does not contain a crosslinking agent, it is not necessary to consider the control of the unfavorable progress of crosslinking during melt molding. Thereby, in the production of the encapsulant sheet using the polyethylene resin as the base resin, the solution is solved by the temperature limitation when the thermosetting encapsulant composition that requires the conventional crosslinking treatment is used. Therefore, in order to improve productivity, the melt molding temperature can be set to a higher temperature range. Thereby, the encapsulant sheet 1 can be manufactured with higher productivity than the conventional thermosetting encapsulant sheet.

<Solar cell module>
The basic configuration of the solar cell module 10 using the encapsulant sheet 1 will be described with reference to FIG. The solar cell module 10 includes a transparent front substrate 2, a thin film solar cell element 3 arranged on the surface of the transparent front substrate 2, a sealing material sheet 1, and a back surface protective cover 4 from the light receiving surface side of incident light. It has a structure in which layers are sequentially stacked. The encapsulant sheet 1 is laminated on the non-light-receiving surface side of the solar cell element 3.

  Here, in the solar cell module 10, as shown in FIG. 3, irregularities due to the metal electrodes 31 and the lead wires 32 for current collection exist on the surface of the solar cell element 3 on the non-light-receiving side. When a conventional encapsulant sheet having a polyethylene resin as a base resin is used, if heat resistance is to be ensured by cross-linking treatment or simply increasing the density, as shown in FIG. The formation of voids V may occur after long-term use in a different environment, which has been a problem.

  However, when the encapsulating material sheet 1 having both high heat resistance and molding durability is arranged on the uneven surface, the encapsulating material sheet 1 is the solar cell element 3 as shown in FIG. Since the metal electrode 31 existing on the surface of the non-light-receiving side and the unevenness due to the lead wire 32 for current collection are sufficiently entangled and the molding durability for maintaining this state is excellent, the formation of the above-mentioned void V is performed. Can be prevented.

More specifically, when the lead wire 32 is a lead wire having a thickness (d ₁ ) of about 250 μm or more, the encapsulant sheet 1 exhibits a special effect which is significantly different from the conventional product. . For example, as shown in FIG. 4, when a thick lead wire 32 is arranged, when a conventional encapsulating material sheet 1A made of a general polyethylene resin is arranged on the uneven surface, the thickness of the sealing material sheet 1A thickness (d ₂₎ lead 32 against (d ₁₎ is, as a measure of approximate, if it exceeds 50%, the formation of the void V is a problem It was often However, as shown in FIG. 2, when the encapsulating material sheet 1 is arranged on such an uneven surface, the thickness (d ₁ ) of the lead wire 32 with respect to the thickness (d ₂ ) of the encapsulating material sheet 1 is increased. Is 90% or less, the formation of the void V can be sufficiently prevented. In the present invention, when there is a state where a plurality of lead wires are laminated, such as when the lead wires are arranged so as to cross each other, the plurality of lead wires in the laminated part The total thickness is considered to be the "lead wire thickness" as mentioned above.

  The transparent front substrate 2 is not limited to one made of a specific material as long as it can maintain the weather resistance, impact resistance, and durability of the solar cell module 10 and allows sunlight to pass therethrough with a high transmittance. When the transparent front substrate 2 is a glass substrate, the encapsulant sheet 1 exhibits a special effect which is significantly different from that of the conventional product due to its excellent glass and metal adhesion.

  The solar cell element 3 may be, for example, an amorphous silicon type, a crystalline silicon type, a CdTe type, a CIS type, a GaAs type, and various conventionally known solar cell elements without particular limitation.

  For the back surface protective cover 4, a resin sheet having physical properties that are normally required for a protective layer arranged in the outermost layer of the solar cell module, such as water vapor barrier properties and weather resistance, can be used. Further, the back surface protective cover 4 may be a glass substrate similar to the transparent front substrate 2. Since the encapsulant sheet 1 has good adhesion to both metal and glass, it can be preferably used even when the back surface protective cover 4 is a glass substrate.

  The layer structure of the solar cell module 10 is not limited to the above embodiment. Since the encapsulant sheet 1 has adhesiveness to both glass and metal, it is preferably used for solar cell modules of various configurations including a glass base material and a metallic solar cell module by taking advantage of its characteristics. You can For example, in the solar cell module, the encapsulating material sheet 1 can be preferably used even when one surface of the encapsulating material sheet faces the metal surface and the other surface faces the glass layer. .

  Furthermore, as another preferred embodiment of the solar cell module of the present invention, a solar cell module including a configuration in which the current collecting sheet and the sealing material sheet 1 are integrated can be mentioned. The current collecting sheet is a constituent member of a solar cell module which is generally arranged for the purpose of collecting current from a back contact type solar cell element, and a conductive circuit for current collection is formed on the surface of a resin base material. It has been done. The encapsulant sheet laminated on the circuit and the solar cell element of the current collecting sheet is required to have a shock absorbing function and further an insulating function. Requires a high standard of physical properties. As described above, since the encapsulant sheet of the present invention has extremely good molding durability, it can be preferably used also in the solar cell module having the above configuration.

  In the solar cell module 10, for example, a transparent front substrate 2 having a solar cell element 3 formed thereon, a sealing material sheet 1, and a back surface protective cover 4 are sequentially laminated and then integrated by vacuum suction or the like, and then laminated. The above-mentioned member can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a method.

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

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

<Manufacture of encapsulant sheet for solar cell module>
Raw materials for the encapsulant composition described below were mixed in the proportions (parts by mass) shown in Table 1 below to obtain the encapsulant composition for the core layer and the skin layer for the encapsulant sheets of Examples and Comparative Examples, respectively. A sealing material composition was prepared. Using a φ30 mm extruder and a film forming machine having a 200 mm wide T-die for each sealing material composition, the core layer and the skin layer are extruded at a temperature of 210 ° C. and a take-up speed of 1.1 m / min. Each resin sheet was produced, and these resin sheets were laminated to manufacture a three-layer structure encapsulant sheet having a core layer and a skin layer disposed on both outermost surfaces of Examples and Comparative Examples. The total thickness of each encapsulant sheet in the examples and comparative examples was 450 μm. Regarding the thickness ratio of each layer of the three-layer structure encapsulating material sheets of Examples and Comparative Examples, the thickness ratio of skin layer: core layer: skin layer is 1: 8: The total thickness of 1 (the total thickness of the skin layers (the total of two layers) was set to 1/4 of the total thickness of the encapsulating material sheet).

  The following raw materials were used as the raw material of the sealing material composition for molding each resin sheet for the sealing material sheet.

(Base resin for encapsulant composition for core layer)
Base resin 1 (indicated as “1” in the table): density of 0.919 g / cm ³ , melting point of 105 ° C., MFR at 190 ° C. is 3.5 g / 10 min, metallocene linear low density polyethylene. Resin (M-LLDPE).

Additive 1 for reducing elastic modulus (denoted as "1" in the table, the same applies hereinafter): metallocene having a density of 0.880 g / cm ³ , a melting point of 60 ° C, and an MFR of 3.5 g / 10 minutes at 190 ° C. -Based linear low-density polyethylene-based resin (M-LLDPE).
Additive 2 for lowering elastic modulus: a metallocene-based linear low-density polyethylene-based resin (M-LLDPE) having a density of 0.898 g / cm ³ , a melting point of 90 ° C., and an MFR at 190 ° C. of 3.5 g / 10 min.
Additive for decreasing elastic modulus 3: ethylene / propylene / ENB (5% ENB ratio) (X3012 manufactured by Mitsui Chemicals, Inc.) Storage elastic modulus at 85 ° C. (E ′) 8.00 × 10 ⁵ Pa
Additive 4 for decreasing elastic modulus: ethylene / propylene / ENB (5% ENB ratio oil extended EPT) (3072 EPM manufactured by Mitsui Chemicals, Inc.) Storage elastic modulus (E ') at 85 ° C 3.50 x 10 ⁵ Pa
Additive 5 for lowering elastic modulus: mineral oil (Diana Process Oil PW380 manufactured by Idemitsu Kosan Co., Ltd.)

(Base resin for encapsulant composition for skin layer)
Base resin 2 (denoted as "2" in the table): The above-mentioned additive 2 for lowering elastic modulus was used as the base resin of the encapsulant composition for the skin layer.

(Other additives)
Weathering agent masterbatch: KEMISISTAB62 (HALS) with respect to 100 parts by mass of base resin (density 0.919 g / cm ³ , melting point 105 ° C., low density polyethylene resin having an MFR of 3.5 g / 10 min at 190 ° C.) : 0.6 part by mass. KEMISORB12 (UV absorber): 3.5 parts by mass. KEMISORB 79 (UV absorber): 0.6 parts by mass. The weather resistance master badge was added to the core layer and skin layer compositions of all Examples and Comparative Examples in an amount of 10 parts by mass.

Silane-modified polyethylene-based resin: 2 parts by mass of vinyltrimethoxysilane with respect to 100 parts by mass of a metallocene-based linear low-density polyethylene-based resin having a density of 0.900 g / cm ³ and an MFR of 2.0 g / 10 min. A silane-modified polyethylene resin obtained by mixing 0.15 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst), melting and kneading at 200 ° C. Density 0.900 g / cm ³ , MFR 1.0 g / 10 min. Melting point 100 [deg.] C. The silane-modified polyethylene-based resin was added to the core layer compositions of all Examples and Comparative Examples in an amount of 3 parts by mass, and the skin layer compositions of 15 parts by mass.

<Storage elastic modulus (E ') of each layer>
The storage elastic modulus (E ′) of each layer of Examples and Comparative Examples was measured by DMA in a single film by the following measuring method, and the storage elastic modulus (E ′) at 85 ° C. was compared for each sample. .
(Measurement method) The encapsulant sheets of Examples and Comparative Examples were cut into a size of 5 mm x 20 mm and used as a sample, and measurement was carried out with UBM's Rheogel E-4000. The measurement was performed in the tensile mode under the following conditions.
Initial load 100g, continuous vibration mode, waveform: sine wave, frequency 10hz, heating rate 3 ° C / min
The results are shown in Table 1.

The storage elastic modulus (E ′) of the core layer can be estimated from the storage elastic modulus (E ′) of all layers of the multilayer encapsulant sheet, the composition of each layer, and the thickness ratio of each layer. As a specific example, when the storage elastic modulus (E ′) in all layers of the multilayer encapsulating material sheet of Example 1 was measured by the above-described measurement method, the storage elastic modulus of the core layer single film of the encapsulating material sheet was measured. The modulus (E ′) was 7.50 × 10 ⁶ Pa (see Table 1), whereas the storage elastic modulus (E ′) in all layers was 6.80 × 10 ⁶ Pa. In the encapsulant sheet of the present invention in which the thickness ratio of the skin layer is limited within a predetermined thickness ratio, the storage elastic modulus (E ′) of all layers is slightly reduced due to the influence of the physical properties of the skin layer. It has been confirmed that the fluctuation amount is a very small fluctuation as described above.

<Evaluation example 1: Molding durability>
A lead wire (diameter of 250 μm) was arranged on the surface of the white plate tempered glass having a flat surface, the lead wire was further covered, and each encapsulant sheet of Example and Comparative Example cut to 150 mm × 150 mm was laminated. The sample was subjected to a vacuum heating laminator treatment at a set temperature of 165 ° C., vacuum evacuation for 3 minutes, and atmospheric pressure pressurization for 7 minutes to obtain a solar cell module evaluation sample for each of Examples and Comparative Examples. The resin temperature (achieved temperature) of the encapsulant sheet during lamination during this heat treatment was 162 ° C. For these solar cell module evaluation samples, the state after the following dump heat (DH) test was visually observed, and the molding durability was evaluated according to the following evaluation criteria. D. H. The test was based on JIS C8917, and the durability test of the sample module for evaluation was carried out for 500 hours under the conditions of a test tank temperature of 85 ° C. and a humidity of 85%.
(Evaluation Criteria) A: Completely follows irregularities on the surface of the base material facing the encapsulant sheet. No void formation was observed.
B: 5 bubbles or less within 2 mm ² were observed.
C: A part of the encapsulating material sheet did not completely follow the concavities and convexities on the surface of the facing substrate, and a defective part of lamination (void) was formed in the vicinity of the lead wire.
The evaluation results are shown in Table 1 as "molding durability".

<Evaluation Example 2: Heat resistance test>
A heat resistance creep test was performed as a heat resistance test. One sheet of the encapsulant sheet of Example and Comparative Example cut out into 5 cm × 7.5 cm on the same glass plate as in Evaluation Example 1 was placed one on top of the other, and 5 cm × 7.5 cm of the same glass plate as in Evaluation Example 1 was placed thereon. Then, a vacuum heating laminator treatment was performed under the same conditions as in Evaluation Example 1 above to prepare a sample for evaluation. Then, a large glass was placed vertically and left at 105 ° C. for 12 hours, and the moving distance (mm) of a glass plate of 5 cm × 7.5 cm after standing was measured and evaluated. The evaluation was performed based on the following criteria.
(Evaluation criteria) A: 0.00 mm
B: more than 0.00 mm and less than 1.0 mm
C: 1.0 mm or more The evaluation results are shown in Table 1 as "heat resistance".

  From Table 1, it can be seen that the encapsulant sheets of the examples are encapsulant sheets having a high level of molding durability and heat resistance. From the above, it can be seen that the encapsulant sheet of the present invention is a encapsulant sheet for a solar cell module that does not require a crosslinking step, has high productivity, and has both heat resistance and molding durability at a high level. .

1 Encapsulant Sheet 11 Core Layer 12 Skin Layer 2 Transparent Front Substrate 3 Solar Cell Element 31 Metal Electrode 32 Lead Wire 4 Backside Protective Cover 10 Solar Cell Module

Claims (4)

A method for manufacturing a multilayer encapsulant sheet, which comprises a core layer and a skin layer arranged on both outermost layers of the encapsulant sheet, and comprising a plurality of layers,
The core layer encapsulant composition for forming the core layer comprises a polyethylene resin having a density of 0.910 g / cm ³ or more and 0.930 g / cm ³ or less as a base resin, and 2% by mass of an elastic modulus lowering additive. It is contained in the range of 50% by mass or more and does not contain a crosslinking agent,
Skin layer sealing material composition for forming the skin layer, the density of 0.890 g / cm ³ or more 0.910 g / cm ³ or less of the polyethylene resin as a base resin, does not contain a crosslinking agent,
A melt molding step of melt molding the core layer encapsulant composition and the skin layer encapsulant composition at a melt molding temperature of 175 ° C. or higher;
Crosslinking treatment was not performed for any of the encapsulant compositions,
The storage modulus at 85 ° C. of the core layer, and 1.0 × ¹⁰ 6 Pa or more 2.0 × ¹⁰ 7 Pa or less,
The total thickness of the skin layer, and at least 1/20 1/3 of the total thickness of the sealing material sheet,
A method for manufacturing a sealing material sheet for a solar cell module. The method for producing a sealing material sheet according to claim 1, wherein the additive for lowering the elastic modulus is an elastomer and / or a mineral oil. The method for producing a sealing material sheet according to claim 1 or 2, wherein the elastic modulus lowering additive is an elastomer, and the content of the elastomer in the core layer is 15% by mass or more and 45% by mass or less. . Sealing material sheet manufacturing method according to any one of claims 1 to 3, the storage modulus at 85 ° C. of the core layer, or less 5.0 × 10 6 ^Pa.

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