JP6686291B2 - Encapsulant sheet for solar cell module and encapsulant-integrated backside protection sheet using the same - Google Patents

Description

  The present invention relates to an encapsulant sheet for a solar cell module and an encapsulant-integrated backside protection sheet using the encapsulant sheet.

  Conventionally, as a layer structure of a solar cell module, a structure in which a transparent front substrate, a light-receiving surface-side encapsulant sheet, a solar cell element, a non-light-receiving surface-side encapsulant sheet, and a back surface protective sheet are sequentially laminated from the light-receptive surface side It is common.

  As the encapsulant sheet used for the solar cell module, a resin sheet made of ethylene-vinyl acetate copolymer resin (EVA) is the most common from the viewpoints of workability, workability, manufacturing cost, etc. It is used as a thing. However, the EVA resin tends to be gradually decomposed with long-term use, and deteriorates inside the solar cell module to reduce its strength, or generates acetic acid gas that affects the solar cell element. there is a possibility. Therefore, a sealing material sheet for a solar cell module has been proposed in which a polyolefin resin such as polyethylene is used instead of the EVA resin (Patent Documents 1 and 2).

  Here, in general, in a polyethylene-based resin-based encapsulating material sheet, transparency and flexibility can be improved by reducing the density. However, lowering the density causes problems such as excessive flow during heating and insufficient heat resistance of the base resin, which leads to a risk of product deterioration during long-term use in a high temperature environment.

  On the other hand, in recent years, there has been an increasing demand for thinner solar cell modules, particularly for the encapsulant sheet portion, in order to reduce the size and cost, or from the viewpoint of curl deformation suppression in a treatment process involving heating. ing. However, the thinning of the encapsulant sheet as described above is likely to lead to excessive flow of the encapsulant material resin component due to insufficient heat resistance as described above, and there is a risk of functional deterioration of the encapsulant sheet accompanying this. Increase. This has been an obstacle in promoting the reduction in thickness of the encapsulant sheet, and thus the solar cell module.

  In the sealing materials of Patent Document 1 and Patent Document 2, heat resistance and flame retardancy are imparted by a crosslinking agent. For example, in Patent Document 1, about 1% of a cross-linking agent is added, and in Patent Document 2 as well, an amount of a cross-linking agent having a gel fraction of 30% or more is added. In this case, the heat resistance is certainly improved, but it is difficult to maintain the flexibility. Then, since the film-forming property deteriorates when the crosslinking progresses during the molding, it is necessary to consider such as performing the molding at a low temperature and carrying out the crosslinking reaction again after the molding, as in Patent Document 1, in terms of productivity. There was a strong demand for further improvement.

JP-A-2000-91611 JP, 2009-10277, A

  The present invention has been made in view of the above situation, is a sealing material sheet using a polyethylene resin, good flexibility suitable for a sealing material sheet for a solar cell module, and heat resistance It is an object of the present invention to provide an encapsulant sheet for a solar cell module, which is capable of further reducing the thickness of the solar cell module while having both

  The present inventors have conducted extensive studies to solve the above problems. As a result, the encapsulant sheet for solar cell modules has a multi-layer structure including a core layer and a skin layer, and heat-resistant resin with relatively high density and adhesive resin with relatively low density are optimal for each layer. The inventors have found that the above problems can be solved by the distribution, and have completed the present invention. More specifically, the present invention provides the following.

  (1) An encapsulant sheet for a solar cell module, which is a multilayer sheet having a core layer and a skin layer, wherein the core layer has a melting point of 125 ° C or higher and 170 ° C or lower in a content ratio in all resin components. The heat-resistant resin, which is high-density polyethylene, is contained in an amount of 20% by mass or more and 95% by mass or less, and the content of the adhesive resin, which is a low-density polyethylene having a melting point of 70 ° C or more and 100 ° C or less, is 70% by mass or less, and the skin layer is Is an encapsulant sheet containing 30% by mass or more and 100% by mass or less of the adhesive resin and 40% by mass or less of the heat resistant resin in the content ratio in all resin components.

  (2) The encapsulant sheet according to (1), which has a thickness of 100 μm or more and 400 μm or less.

  (3) The encapsulant sheet according to (1), which has a thickness of 100 μm or more and 250 μm or less.

  (4) A multilayer sheet having a three-layer structure of skin / core / skin, in which one skin layer and / or core layer contains a colored pigment, and the other skin layer contains a colored pigment. The encapsulant sheet according to any one of (1) to (3), which is not provided.

  (5) A sealant for a solar cell module, in which the encapsulant sheet according to any one of (1) to (4) and a back surface protective sheet are laminated in such a manner that the skin layer is exposed to the outermost layer side. Backside protection sheet with integrated stopper.

  (6) An encapsulant-integrated back surface protection sheet for a solar cell module, comprising the encapsulation material sheet according to (4) and a back surface protection sheet laminated together, wherein the one skin contains a colored pigment. An encapsulant-integrated back surface protection sheet, wherein the encapsulant sheet is laminated on the back surface protection sheet in a mode in which a layer faces the back surface protection sheet.

  (7) The encapsulant-integrated back surface protection sheet according to (5) or (6), wherein the back surface protection sheet includes a polyethylene terephthalate layer and / or a hydrolysis-resistant polyethylene terephthalate layer.

  (8) The encapsulant-integrated back surface protection sheet according to any one of (5) to (7), which has a thickness of 180 μm or more and 480 μm or less.

  (9) The solar cell in which the encapsulant-integrated back surface protection sheet according to any one of (5) to (8) is laminated on the non-light-receiving surface side of the solar cell element in a manner in which the skin layer faces each other. Battery module.

  ADVANTAGE OF THE INVENTION According to this invention, while having the favorable flexibility suitable for the sealing material sheet for a solar cell module, and heat resistance, the solar cell module which enables further thinning of a solar cell module. The encapsulant sheet can be provided.

It is a cross-sectional schematic diagram which shows the layer structure of the sealing material sheet of this invention. It is a cross-sectional schematic diagram which shows the layer structure of the sealing material integrated back surface protection sheet which uses the sealing material sheet of this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the solar cell module which uses the sealing material integrated type back surface protection sheet of this invention. It is a cross-sectional schematic diagram which shows an example of the laminated constitution of the conventional general solar cell module.

  Hereinafter, the details of the encapsulant sheet of the present invention, the encapsulant-integrated back surface protective sheet using the same, and the solar cell module using them will be described. The present invention is not limited to the embodiments described below.

<Basic configuration of solar cell module>
First, the basic configuration of the solar cell module 100 using the encapsulant-integrated back surface protection sheet including the encapsulant sheet of the present invention will be described with reference to FIG. The solar cell module 100 is arranged on the non-light-receiving side from the encapsulant-integrated back surface protective sheet 10 of the present invention, the solar cell element 3, the light-receiving side encapsulating sheet 4, and the transparent outermost layer on the light-receiving side. The front substrate 5 is laminated in this order.

  Here, FIG. 4 shows a layer structure of a conventional general solar cell module (solar cell module 100A). The conventional solar cell module 100A includes a back surface protection sheet 7, a non-light-receiving surface-side encapsulant sheet 6, a solar cell element 3, a light-receiving surface-side encapsulant sheet 4, and a light-receiving surface-side outermost layer from the non-light-receiving surface side. The transparent front substrate 5 arranged in the above is laminated in order.

  The encapsulant-integrated back surface protection sheet 10 of the present invention is formed by integrally laminating the encapsulation material sheet 1 of the present invention that can be thinned while maintaining heat resistance and the like, and the back surface protection sheet 2 having a barrier property. (See FIG. 2). Therefore, in the solar cell module 100 using this, the solar cell module is further thinned as compared with the conventional general solar cell module 100A in which the conventional encapsulating material sheets are laminated on both surfaces of the solar cell element 3. Can be realized.

  As the solar cell element 3 used in the solar cell module 100, for example, amorphous silicon type, crystalline silicon type, CdTe type, CIS type, GaAs type, and various conventionally known solar cell elements can be used without particular limitation. .

  The light-receiving surface-side encapsulant sheet 4 is a resin sheet that is disposed in the solar cell module 100 so as to mainly cover the surface of the solar cell element 3 in order to protect the solar cell element 3 from an external impact. As the resin base material forming the light-receiving surface side encapsulant sheet 4, a thermoplastic resin such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), polyethylene resin such as polyethylene is appropriately used. Can be used.

  The transparent front substrate 5 is generally a glass substrate. The transparent front substrate 5 may be another member as long as it maintains the weather resistance, impact resistance, and durability of the solar cell module 100 and transmits sunlight with high transmittance. .

  For example, as a general mode in the conventional solar cell module 100A (FIG. 4), the thickness of the back surface protection sheet 7 is about 80 μm to 100 μm, and the thickness of the non-light-receiving surface side encapsulant sheet 6 is 400 to. Since the thickness is about 600 μm, the total thickness of the resin base material layer including the encapsulating material sheet and the back surface protection sheet laminated on the non-light-receiving surface side of the solar cell element 3 is about 500 μm to 700 μm. On the other hand, in the solar cell module 100 (FIG. 3) of the present invention, the total thickness of the encapsulant-integrated back surface protection sheet laminated on the non-light-receiving surface side of the solar cell element 3 is about 380 to 500 μm. can do. Further, the total thickness of the solar cell module can be further reduced by arranging the encapsulating material sheet 1 containing no colored pigment as the light receiving surface side encapsulating material sheet.

<Sealing material sheet>
The encapsulant sheet 1 of the present invention is a multilayer sheet having a core layer and a skin layer. The encapsulating material sheet 1 may have a layer structure in which the skin layer 12 is laminated only on one surface of the core layer 11, but as shown in FIG. 1, the skin layer 12 is laminated on both surfaces of the core layer 11. It is preferable that it has a layered structure. In any of the above configurations, the encapsulant sheet 1 is obtained as a encapsulant sheet for a solar cell module by blending a heat-resistant component and an adhesive component described below for each layer in an optimal composition. While maintaining various required physical properties such as heat resistance, heat processing suitability, flexibility, and substrate adhesion, it is possible to sufficiently meet the demand for thinning of the solar cell module.

  The thickness of the encapsulant sheet 1 is not particularly limited, but it is preferably in the range of 100 μm or more and 400 μm or less, and even when it is 250 μm or less, the above heat resistance and various other required physical properties are sufficiently retained. be able to. When the skin layer 12 is laminated on both surfaces of the core layer 11 to form the encapsulant sheet 1 having a three-layer structure, the thickness ratio thereof is 1 in the skin: core: skin thickness ratio. The range is preferably from 3: 1 to 1: 30: 1.

[Core layer]
The core layer 11 mainly has a function of imparting heat resistance and appropriate rigidity to the encapsulating material sheet 1. The core layer 11 is made of a core layer composition containing a polyethylene resin as a base resin.

  The thickness of the core layer 11 is, for example, 40 μm or more and 240 μm or less, and is not particularly limited. When the thickness of the core layer 11 is 40 μm or more, good dimensional stability can be given to the encapsulant sheet 1. In addition, since the thickness of the core layer 11 is 240 μm or less, the encapsulating material sheet 1 can be provided with sheet transportability during laminating.

(Core layer composition)
The core layer composition forming the core layer 11 has a base resin made by blending a plurality of polyethylene resins having different melting points. The core layer composition contains 20% by mass or more and 95% by mass or less, preferably 70% by mass or more of a high-density polyethylene resin having a relatively high melting point and a melting point of 125 ° C. or more and 170 ° C. or less in a content ratio of all resin components. The content is not less than mass% and not more than 90 mass%. Further, the core layer composition may contain a low density polyethylene resin having a relatively low melting point of 70 ° C. or more and 100 ° C. or less. In that case, the content of the same component is in the above content ratio, It is 70% by mass or less, and preferably 65% by mass or less. Hereinafter, the high-density polyethylene resin having a melting point of 125 ° C. or higher and 170 ° C. or lower is also referred to as “heat resistant component”, and the low-density polyethylene resin having a melting point of 70 ° C. or higher and 100 ° C. or lower is also referred to as “adhesive component”. That is, the core layer 11 is a layer having a main function of strengthening heat resistance, which is composed of a core layer composition containing the heat-resistant component in a predetermined proportion or more as described above.

As the heat component, a melting point of 125 ° C. or higher 170 ° C. or less, a density of 0.930 g / cm ³ or more 0.990 g / cm ³ or less, preferably, 0.935 g / cm ³ or more 0.970 g / cm @ 3 or less dense Polyethylene (HDPE) can be used. Even when the encapsulant sheet is a thin sheet having a thickness of 400 μm or less, by including HDPE having a melting point and a density range described above as a heat-resistant component in the core layer composition at the compounding ratio as described above, it is preferable. The encapsulant sheet 1 can be provided with heat resistance.

  The high-density polyethylene used as the heat-resistant component has a melt mass flow rate (MFR) of preferably 0.1 g / 10 minutes or more and 40 g / 10 minutes or less at 190 ° C. and a load of 2.16 kg, and 3.0 g / 10 minutes or more. It is more preferably 15 g / 10 minutes or less. When the MFR of the heat-resistant component is in the above range, it is possible to impart excellent heat resistance and excellent durability to the encapsulant sheet 1 having the core layer 11 while being excellent in processability during film formation. it can. Further, by giving sufficient heat resistance to the encapsulant sheet 1, it is possible to suppress the occurrence of curling deformation of the encapsulant sheet, which is likely to cause a problem during the vacuum laminating process particularly in the production of the embodiment battery module.

Unless otherwise specified, the MFR in this specification is a value obtained by the following method.
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.

When the core layer composition contains an adhesion component, it has a melting point of 70 ° C. or higher and 100 ° C. or lower and a density of 0.920 g / cm ³ or less, preferably 0.880 g / cm ³ or more and 0.910 g / cm ³ or less. Polyethylene (LDPE) can be used as the same component. The adhesive component is more preferably a copolymer of ethylene and α-olefin, and linear low density polyethylene (LLDPE) having a melting point and a density within the above range can be used. By setting the kind, the melting point and the density range, and the content ratio of the adhesive components to the above-described composition ranges, it is possible to impart the required flexibility to the encapsulating material sheet 1 while maintaining the heat resistance of the core layer 11. it can.

  As the polyethylene resin used as the adhesion component, metallocene linear low-density polyethylene (M-LLDPE) is more preferable. M-LLDPE is synthesized using a metallocene catalyst which is a single site catalyst. Such polyethylene has few side chain branches and has a uniform distribution of comonomers. Therefore, the molecular weight distribution is narrow, and the above-mentioned ultra-low density can be relatively easily achieved. Further, since the crystallinity distribution is narrow and the crystal sizes are uniform, not only there is no crystal with a large crystal size, but also the crystallinity itself is low due to the low density. Therefore, it is excellent in processability and flexibility when processed into a sheet.

  As the α-olefin of LLDPE, an α-olefin having no branching is preferably used, and among these, 1-hexene, 1-heptene or 1-octene which is an α-olefin having 6 to 8 carbon atoms is preferably used. Are particularly preferably used. When the carbon number of the α-olefin is 6 or more and 8 or less, the core layer 11 can be provided with necessary flexibility and good strength.

  The melt mass flow rate (MFR) of low-density polyethylene used as an adhesive component is preferably 0.5 g / 10 minutes or more and 30 g / 10 minutes or less at 190 ° C. and a load of 2.16 kg, and 1 g / 10 minutes or more and 20 g / It is more preferably 10 minutes or less. When the MFR is in the above range, a resin composition having excellent processability during film formation can be obtained.

  The core layer 11 may further contain silane-modified polyethylene in a predetermined ratio. Here, the silane-modified polyethylene is a resin obtained by graft-polymerizing an ethylenically unsaturated silane compound on low-density polyethylene. The details will be described later.

  The core layer 11 may further contain an inorganic filler. As a result, the rigidity of the core layer 11 is increased, and the occurrence of undesired curl deformation of the encapsulant sheet 1 can be suppressed. Examples of such inorganic fillers include talc (hydrous magnesium silicate), titanium oxide, and others such as calcium carbonate, carbon black, titanium black, Cu-Mn-based composite oxide, Cu-Cr-Mn-based composite oxide, Alternatively, zinc oxide, aluminum oxide, iron oxide, silicon oxide, barium sulfate, calcium carbonate, titanium yellow, chrome green, ultramarine blue, aluminum powder, mica, barium carbonate or the like can be used. The content of the inorganic filler in the core layer composition forming the core layer 11 is not essential, and the content may be in the range of 0% by mass to 30% by mass in the resin component of the core layer composition.

  In addition, when the back protective sheet is required to have a colored appearance, among the above-mentioned inorganic fillers, it is excellent in weather resistance, easy to be made into a paint, and easily available including price. Therefore, the white pigment may further include titanium oxide or the like, and the black pigment may further include carbon black or the like. The inclusion of these colored pigments is preferable in that the power generation efficiency can be improved due to the re-reflection of sunlight, or the demand for design can be met.

[Skin layer]
The skin layer 12 is a layer arranged on one outermost layer or both outermost layers of the encapsulant sheet 1. In the solar cell module 100, the skin layer 12 forms a non-light-receiving surface-side surface of the solar cell element 3 and a contact surface with the light-receiving surface-side sealing material sheet 4, or the sealing material-integrated back surface protection sheet 10. In this case, it becomes a contact surface with the back surface protective sheet 2. In particular, in the former case, the adhesion of the encapsulant sheet 1 and the followability to irregularities of other members during lamination for integration as a solar cell module (hereinafter referred to as "molding characteristics") are improved. Contribute.

  The thickness of the skin layer 12 may be appropriately determined in consideration of the thickness (thinness) required of the encapsulant sheet 1. As an example, in the case where the skin layer 12 has a layer structure laminated on one surface of the core layer 11, a preferable thickness of the skin layer 12 is 3 μm or more and 150 μm or less. When the thickness of the skin layer 12 is 3 μm or more, sufficient adhesion and molding characteristics can be given to the encapsulant sheet 1.

  When the skin layers 12 are formed on both surfaces of the core layer 11, one of the two skin layers 12 may contain a colored pigment. In this case, it is preferable that the other skin layer 12 does not contain a colored pigment. The encapsulant sheet 1 having such a layer configuration is preferably arranged in the solar cell module 100 so that the one skin layer 12 containing the colored pigment faces the back surface protection sheet 2. Thereby, in the solar cell module 100, the encapsulant sheet 1 can exert a light reflecting function on the non-light-receiving surface side of the solar cell element 3 to contribute to the improvement of the power generation rate of the solar cell module 100. At this time, if the other skin layer 12 does not contain a colored pigment, it is possible to prevent deterioration of the adhesion and molding characteristics of the same layer due to the excessive addition of the pigment. Therefore, it is preferable that the other skin layer 12 does not contain a colored pigment.

(Skin layer composition)
The skin layer composition forming the skin layer 12 has a base resin made by blending a plurality of polyethylene resins having different melting points. The skin layer composition is a low density polyethylene resin having a relatively low melting point of 70 ° C. or more and 100 ° C. or less, in a content ratio of all resin components, of 30% by mass or more and 100% by mass or less, preferably 70% by mass. % Or more and 100% by mass or less. Further, the skin layer composition may contain a high density polyethylene resin having a relatively high density and a melting point of 125 ° C. or higher and 170 ° C. or lower. In that case, the content of the same component is in the above content ratio. , 40 mass% or less, and preferably 20 mass% or less. That is, the skin layer 12 is a layer mainly composed of a skin layer composition containing an adhesive component in a predetermined ratio or more as described above and mainly having a function of enhancing the molding property and the adhesiveness.

The skin layer composition has a low density of 70 ° C. or higher and 100 ° C. or lower and a density of 0.920 g / cm ³ or lower, preferably 0.880 g / cm ³ or higher and 0.910 g / cm ³ or lower as the above-mentioned adhesion component. Polyethylene (LDPE), more preferably linear low density polyethylene (LLDPE), which is a copolymer of ethylene and α-olefin and has a melting point and a density within the above ranges, can be used. By setting the kind, the melting point, the density range, and the content ratio of the adhesive components to the above-described composition ranges, preferable flexibility can be imparted to the encapsulant sheet 1 having the skin layer 12.

Additional heat components together in the skin layer composition, i.e., a melting point of 125 ° C. or higher 170 ° C. or less, a density of 0.930 g / cm ³ or more 0.990 g / cm ³ or less, preferably, 0.935 g / cm ³ High density polyethylene (HDPE) of 0.970 g / cm ³ or less can be used. As the heat-resistant component, HDPE having the above melting point and density within the range described above was contained in the skin layer composition, whereby the flexibility of the skin layer 12 resulting from the inclusion of the above-mentioned adhesion component was maintained. As it is, the skin layer 12 can be provided with preferable heat resistance. When both the adhesive component and the heat-resistant component are made of polyethylene resin, good moldability and dispersibility can be obtained due to the high compatibility between the two resins.

  Further, the skin layer composition preferably contains silane-modified polyethylene in a predetermined ratio. The silane-modified polyethylene-based resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain on a linear low-density polyethylene (LLDPE) which is a main chain. Since such a graft copolymer has a high degree of freedom of silanol groups that contribute to the adhesive force, the adhesiveness of the encapsulant sheet 1 can be further improved.

  The graft amount, which is the content of the ethylenically unsaturated silane compound, is such that the graft amount of the ethylenically unsaturated silane compound with respect to 100 parts by mass of the polyethylene resin forming the skin layer is, for example, 0.001 part by mass or more and 15 parts by mass or less. It may be adjusted appropriately so that it is preferably 0.05 parts by mass or less and 2 parts by mass or less, more preferably 0.1 parts by mass or more and 1.0 parts by mass or less. When the content of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent, but when the content is excessive, the tensile elongation and the heat fusion property tend to be poor.

  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 a sealing material composition for a solar cell module, strength and durability can be improved. Excellent in properties such as weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, hail resistance, and other characteristics, and further affect manufacturing conditions such as heating and pressure bonding for manufacturing solar cell modules. It is possible to manufacture a solar cell module having excellent heat fusion properties without being subjected to heat treatment, stably, at low cost, and suitable for various applications.

  Examples of the ethylenically unsaturated silane compound that is graft-polymerized with linear low-density polyethylene include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, and vinyltripentyloxysilane. , At least one selected from vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane. be able to.

(Other ingredients)
The skin layer composition and the core layer composition may further contain other components. For example, components such as various weather-resistant masterbatches for imparting weather resistance to the encapsulant sheet 1, various fillers, light stabilizers, ultraviolet absorbers, and heat stabilizers 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 1 can be provided with a stable improvement in mechanical strength over a long period of time and an effect of preventing yellowing, cracking, and the like.

<Encapsulation material integrated backside protection sheet>
As shown in FIG. 2, the encapsulant-integrated back surface protective sheet 10 is a multilayer resin sheet formed by integrally forming the encapsulant sheet 1 and the back surface protective sheet 2. The thickness of the encapsulant-integrated back surface protection sheet 10 is not particularly limited, but with a thickness in the range of 325 μm or more and 500 μm or less as a general example, a thickness in the range of 180 μm or more and 480 μm or less It can be mentioned as a specific example of the preferred embodiment. Then, the encapsulant-integrated back surface protection sheet 10 is used by being disposed in the solar cell module 100 such that the encapsulant sheet 1 faces the non-light-receiving surface side of the solar cell element 3.

  As the back surface protective sheet 2 that is laminated with the encapsulating material sheet 1 to form the encapsulating material-integrated back surface protective sheet 10, use is made of various resin sheets that have been conventionally used as back surface protective sheets for solar cell modules. You can Examples of the resin sheet forming the back surface protection sheet 2 include polyethylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride resin, and poly (vinyl chloride) resin. (Meth) acrylic resin, polycarbonate resin, polyethylene terephthalate (PET), polyester resin such as polyethylene naphthalate, polyamide resin such as various nylons, polyimide resin, polyamide imide resin, polyaryl phthalate resin, Various resin sheets such as silicone resin, polysulfone resin, polyphenylene sulfide resin, polyether sulfone resin, polyurethane resin, acetal resin, and cellulose resin can be used. Among these, polyethylene terephthalate (PET) can be preferably used from the viewpoints of insulating properties, mechanical strength, cost, physical properties such as transparency, and economical efficiency. In addition, from the viewpoint of further improving mechanical strength and water vapor barrier property, a multilayer sheet obtained by further laminating hydrolysis resistant PET as the outermost layer in addition to the above PET can be particularly preferably used as the back surface protective sheet 2. .

  The thickness of the back surface protective sheet 2 is not particularly limited, but is required for the encapsulant-integrated back surface protective sheet 10 as long as the physical properties such as the water vapor barrier property required for the back surface protective sheet 2 can be maintained. It may be appropriately determined in consideration of the thickness. The thickness of the back surface protective sheet 2 is preferably 25 μm or more and 300 μm or less, and more preferably 25 μm or more and 250 μm or less. When the thickness of the back surface protection sheet 2 is 25 μm or more, preferable durability and weather resistance can be imparted to the encapsulant-integrated back surface protection sheet 10.

  It should be noted that the backside protective sheet 2 can be preferably used by further laminating a weather resistant layer (not shown) on one surface which is supposed to be the outermost layer side when integrated with the solar cell module. As the weather resistant layer, one having excellent weather resistance, heat resistance, light resistance and the like is used. As the base material forming the weather resistant layer, PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ester copolymer), PTFE (polytetrafluoroethylene), ETFE (tetrafluoroethylene. Preferable examples include a resin sheet such as an ethylene copolymer) and a fluorine-based resin such as PVDF (polyvinylidene fluoride), or an aluminum sheet. Further, the weather resistant layer may be one in which a weather resistant coating layer is formed on the surface of the base material layer by surface processing such as fluorine coating, EB coating, silica vapor deposition and the like. Further, the above-mentioned resin sheet or the like having weather resistance, which is made to have a required strength by a predetermined thickness or processing, can be used as the backside protective sheet 2.

  The encapsulating material sheet 1 and the back surface protective sheet 2 in the encapsulant-integrated back surface protection sheet 10 are preferably integrated by a dry laminating method performed via an adhesive layer (not shown). However, as long as it can maintain desired adhesion and durability, it may be integrated by other conventionally known means. For example, an extrusion coat laminating method of directly extruding the resin composition to be the encapsulating material sheet on the surface of the back surface protective sheet 2 with an extruder to form the encapsulating material sheet 1 or a sandwich laminating method which is an application form thereof. The encapsulating material sheet 1 and the back surface protective sheet 2 can be integrated to form the encapsulating material integrated back surface protective sheet 10.

<Manufacturing method of backside protective sheet with integrated encapsulant>
A method for manufacturing the encapsulant-integrated back surface protection sheet of the present invention will be described. The encapsulant-integrated back surface protection sheet 10 includes a “rear surface protection sheet forming step” for forming the back surface protection sheet 2, a “sealing material sheet forming step” for forming the encapsulation material sheet 1, and a back surface protection sheet 2. The encapsulating material sheet 1 can be manufactured by going through an "integration step" in which the encapsulating material sheets 1 are laminated and integrated.

(Back protection sheet forming process)
The back surface protection sheet 2 is formed by forming a resin material such as PET described above by an extrusion method, a cast molding method, a T die method, a cutting method, an inflation method, or another film forming method. You can The back surface protection sheet 2 may contain other additives such as pigments in addition to the above resin materials, as long as the effects of the present invention are not impaired.

(Sealing material sheet forming process)
The encapsulant sheet 1 can be obtained by integrally molding the above-mentioned skin layer composition and core layer composition by a known coextrusion method to form a multilayer sheet.

(Integration process)
The encapsulant sheet 1 of the present invention, the back surface protective sheet 2, and optionally a sheet for forming other layers formed by the same method are appropriately laminated and further integrated to form the encapsulating material of the present invention. The material-integrated backside protection sheet 10 can be obtained. The respective sheets can be integrated by a conventionally known dry laminating method. As the laminating adhesive, conventionally known ones can be used without any particular limitation, and a two-component curing type dry laminating adhesive comprising a urethane-based or epoxy-based main agent and a curing agent can be appropriately used. In addition, this integration step can also be performed by an extrusion coat laminating method or a sandwich laminating method which is an application form thereof.

<Method of manufacturing solar cell module>
In the solar cell module 100, for example, the transparent front substrate 5, the light receiving surface side encapsulant sheet 4, the solar cell element 3, and the encapsulant-integrated back surface protective sheet 10 are sequentially laminated and then vacuum suction is performed. And the like, and then the above-mentioned member can be manufactured by thermocompression molding as an integral molded body by a molding method such as a lamination method. For example, in the case of vacuum heat laminating, the laminating temperature is preferably in the range of 130 ° C to 180 ° C. The laminating time is preferably in the range of 5 to 20 minutes, and particularly preferably in the range of 8 to 15 minutes. Thus, the solar cell module 100 can be manufactured by thermocompression-molding each of the above layers as an integrally molded body.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Manufacture of encapsulant sheet>
Using the following materials, the encapsulating material sheets of Examples and Comparative Examples were prepared by the above-mentioned "method for producing an encapsulating material sheet".

  Mixtures of the following materials having the compositions shown in Table 1 and Table 2 were separately used as the blends for the core layer and the skin layer of the encapsulant sheets of Examples and Comparative Examples. Then, each of these blends was formed into a sheet at an extrusion temperature of 210 ° C. and a take-up speed of 1.1 m / min using a sheet forming machine having a φ30 mm extruder and a T die having a width of 200 mm, and two or three layers thereof were formed. Of the sealing material sheet. The total thickness of each encapsulant sheet and the thickness of each layer are as shown in Tables 1 and 2.

The following raw materials were used as materials for the encapsulant sheet.
High-density polyethylene (HDPE, written as “HD” in the table): Density 0.963 g / cm ³ , melting point 135 ° C. MFR is 7.0 g / 10 minutes.
Low-density polyethylene (LDPE, described as "LD" in the table): density 0.918 g / cm ³ , melting point 106 ° C. MFR is 2.3 g / 10 minutes.
Linear low-density polyethylene (LLDPE, described as “LLD” in the table): density 0.905 g / cm ³ , melting point 97 ° C. MFR 3.5g / 10 minutes.
Silane-modified polyethylene-based resin (indicated as “Si” in the table): Density 0.900 g / cm ³ , MFR 1.2 g / 10 min Metallocene-based linear low-density polyethylene (M-LLDPE) 98 parts by mass, 2 parts by mass of vinyltrimethoxysilane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) are mixed, melted and kneaded at 200 ° C., density 0.903 g / cm ³ , MFR1. A silane-modified transparent resin having a weight of 0.0 g / 10 minutes was obtained.
White pigment masterbatch (denoted as "white MB" in the table): 60 parts by mass of titanium oxide having an average particle size of 0.3 µm was mixed with 40 parts by mass of the above-mentioned high-density polyethylene (HDPE), and the temperature was 200 ° C. It was melted and kneaded in, and molded into pellets.
Weather resistance masterbatch (indicated as “weather resistance MB” in the table): 3.8 parts by weight of benzophenol-based ultraviolet absorber and hindered amine-based light with respect to 100 parts by weight of powder obtained by crushing the above high-density polyethylene (HDPE) 5 parts by mass of the stabilizer and 0.5 parts by mass of the phosphorus-based heat stabilizer were mixed, melted, processed, and molded into pellets.

  Regarding the polyethylene-based resins contained in the core layer and the skin layer of the encapsulant sheets of the above Examples and Comparative Examples, respectively, the content of low-density polyethylene having a melting point of 70 ° C. or higher and 100 ° C. or lower in all resin components ( Mass%) and the content (mass%) of high-density polyethylene having a melting point of 125 ° C. or higher and 170 ° C. or lower were calculated. Each value is shown as "adhesive component" for low-density polyethylene having a melting point of 70 ° C or more and less than 100 ° C and "heat-resistant component" for high-density polyethylene having a melting point of 125 ° C or more and 170 ° C or less. ~ Shown in Table 4.

<Manufacture of backside protective sheet with integrated encapsulant>
Further, the encapsulant sheet of each of the above Examples and Comparative Examples and a PET film (“Melinex S” manufactured by Teijin DuPont Co., Ltd., thickness 100 μm) having a corona-treated surface are prepared by a conventionally known dry lamination method. Then, the encapsulant-integrated back surface protection sheets of Examples and Comparative Examples were obtained.

  For each encapsulant sheet and encapsulant-integrated backside protective sheet of the above-mentioned Examples and Comparative Examples, based on the test method and evaluation criteria described below, laminate suitability, heat resistance, and adhesion were measured and evaluated. did. The results are shown in Tables 3 and 4.

<Evaluation of suitability for lamination>
White plate semi-tempered glass, a solar cell element to which a tab wire has been bonded, a sealing material sheet for the light-receiving surface side, and each "sealing material-integrated back surface protection sheet" of Examples and Comparative Examples The light-receiving surface side encapsulant sheet / tab line-bonded solar cell element / encapsulant / encapsulant-integrated backside protective sheet are laminated in this order, and vacuum heating laminating is performed under the following laminating conditions. Samples for solar cell module evaluation were obtained for each of the examples and comparative examples. With respect to these solar cell module evaluation samples, it was observed by visual observation and observation with an optical microscope whether or not the encapsulating material was buried in the periphery of the wiring portion and could be encapsulated, and the suitability for lamination was evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 and 4 as "suitability for laminating".
(Lamination conditions) Vacuuming: 5.0 minutes
Pressurization (0 kPa to 100 kPa): 1.0 minutes
Pressure holding (100kPa): 10.0 minutes
Temperature 150 ℃
(Lamination processing suitability evaluation criteria)
A: No insufficient embedding B: Insufficient embedding C: Bubbles

<Adhesion evaluation>
EVA sealing material (EVA cross-linking type, thickness of 500 μm) which is generally used as a light-receiving surface side sealing material sheet is laminated on a textured 50 mm × 75 mm × 3.2 mm glass, and the EVA sealing is performed. On the surface of the sealing material, each "sealing material sheet" of Example and Comparative Example cut into a width of 15 mm was laminated with the skin layer (skin 1) of each sealing material sheet facing each other, and the above-mentioned laminating suitability was obtained. A vacuum heating laminating process was performed under the same laminating conditions as those at the time of evaluation to obtain a laminate sample for adhesion evaluation for each Example and Comparative Example. With respect to these laminated body samples for evaluation, the adhesion strength was measured and the adhesion was evaluated by the following “Adhesion strength test method”.

[Adhesion strength test]
In the laminate sample for adhesion evaluation, the encapsulant sheet adhered on glass was subjected to a vertical peeling (50 mm / min) test with a peeling tester (Tensilon universal tester RTF-1150-H), The adhesion strength of the encapsulant sheet was measured. The measurement results of each Example and Comparative Example were evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 and 4 as "adhesion".
(Adhesion evaluation standard)
A: 40 N / 15 mm or more B: 25 N / 15 mm or more and less than 40 N / 15 mm C: 25 N / 15 mm or less

<Heat resistance evaluation>
Two sheets of each encapsulating material sheet of Example and Comparative Example cut into 7.5 × 5.0 cm were placed on a glass substrate (white plate float semi-tempered glass JPT3.2 150 mm × 150 mm × 3.2 mm) so as to be superposed. A glass substrate (white plate float semi-tempered glass JPT3.2 75 mm × 50 mm × 3.2 mm) is placed on top of each other, and vacuum heating laminating treatment is performed under the above laminating conditions, and a heat resistance evaluation laminate for each Example and Comparative Example. I got a sample. With respect to these laminate samples for heat resistance evaluation, the heat resistance creep was measured by the following “Adhesion strength test method” to evaluate the heat resistance.

[Heat resistance creep test]
The laminate sample for heat resistance evaluation was placed vertically, left standing at 130 ° C. for 12 hours, and the moving distance of the glass substrate (white plate float semi-strengthened glass JPT3.2 75 mm × 50 mm × 3.2 mm) after standing was measured and evaluated. did. The measurement results of the encapsulant sheets of Examples and Comparative Examples were evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 and 4 as "heat resistance".
(Heat resistance evaluation standard)
A: less than 1.0 mm B: 3.0 mm or more and less than 6.0 mm C: 6.0 mm or more

  From Table 1 to Table 4, the encapsulant sheet of the present invention and the encapsulant-integrated back surface protective sheet using the same, even when the thickness of the encapsulant sheet is about 300 μm, which is thinner than conventional products, It can be seen that it has both good flexibility and heat resistance suitable for a sealing material sheet for a solar cell module, and is excellent in laminating processability and adhesiveness.

DESCRIPTION OF SYMBOLS 1 Sealant sheet 11 Core layer 12 Skin layers 2 and 7 Back surface protection sheet 3 Solar cell element 4 Light-receiving surface side sealing material sheet 5 Transparent front substrate 6 Non-light-receiving surface side sealing material sheet 10 Sealing material integrated backside protection Sheet 100 solar cell module

Claims (4)

An encapsulant sheet and a back surface protective sheet, which are laminated encapsulant back surface protective sheets for solar cell modules,
The encapsulant sheet is a multi-layer sheet having a three-layer structure of skin layer / core layer / skin layer,
The core layer contains a heat-resistant resin, which is a high-density polyethylene having a melting point of 125 ° C. or more and 170 ° C. or less in excess of 40% by mass and 95% by mass or less, and has a melting point of 70 ° C. or more 100 The content of the adhesive resin, which is low-density polyethylene at 70 ° C or less, is 70% by mass or less,
The skin layer contains 30% by mass or more and 98.2 % by mass or less of the adhesive resin and 10 % by mass or less of the heat resistant resin in a content ratio of all resin components,
One of the skin layers contains a colored pigment,
The other skin layer does not contain a colored pigment,
The encapsulant-integrated backside protection sheet, wherein the encapsulant sheet has a skin layer containing a colored pigment, which is laminated on the backside protection sheet in such a manner as to face the backside protection sheet.   The encapsulant-integrated back surface protection sheet according to claim 1, wherein the back surface protection sheet comprises a polyethylene terephthalate layer and / or a hydrolysis-resistant polyethylene terephthalate layer.   The encapsulant-integrated back surface protection sheet according to claim 1, which has a thickness of 180 μm or more and 480 μm or less.   A solar cell module in which the encapsulant-integrated back surface protective sheet according to any one of claims 1 to 3 is laminated on a non-light-receiving surface side of a solar cell element in a mode in which the skin layer faces.

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