JP2017017261A - Sealing material-integrated back face protective sheet for solar cell module and solar cell module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material-integrated back face protective sheet having high reliability and excellent adhesion durability between a sealing material sheet and a back face protective sheet in long-term use of a solar cell module, and a solar cell module using the above sheet.SOLUTION: The sealing material-integrated back face protective sheet is to be used for a solar cell module, and the sheet comprises a sealing material sheet 11 that is a multilayer sheet having a core layer 111 and a skin layer 112, an adhesive layer 13, and a back face protective sheet 12, laminated in such a manner that the skin layer 112 of the sealing material sheet 11 is exposed on the outermost layer side. The core layer 111 and the skin layer 112 of the sealing material sheet 11 contain low-density polyethylene by 60 mass% or more in the whole resin component of the composition in each layer; the sealing material sheet 11 has a film thickness of 200 μm or more and 400 μm or less; a ratio of a coefficient of linear expansion of the sealing material sheet 11 to a coefficient of linear expansion of the back face protective sheet 12 is 10 or more and 1000 or less; and the adhesive layer 13 has an adhesive force of 30 N/15 mm or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sealing material-integrated back protective sheet for a solar cell module and a solar cell module using the same.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Currently, 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 via a sealing material sheet.

  As a sealing material sheet used for a solar cell module, ethylene-vinyl acetate copolymer resin (hereinafter sometimes referred to as EVA resin) from the viewpoints of workability, workability, manufacturing cost, and the like. A resin sheet made of is used as the most general one. However, EVA resin has a tendency to gradually decompose with long-term use, and deteriorates inside the solar cell module to decrease its strength or generate acetic acid gas that affects the solar cell element. there is a possibility. For this reason, the sealing material sheet for solar cell modules which uses polyolefin resin, such as polyethylene, instead of EVA resin is proposed (patent documents 1 and 2).

  The solar cell module is assumed to be used for a long time in a high temperature environment. For this reason, the solar cell module is required to have a high level of long-term durability. For example, if the adhesion between the resin base materials constituting the solar cell module, such as a sealing material sheet and a back surface protection sheet, decreases during the period of use, the power generation efficiency decreases due to a decrease in barrier properties or is fatal. Cause trouble.

  Here, in the solar cell module, the encapsulant sheet mainly follows the unevenness of other members such as the solar cell element during lamination (hereinafter referred to as “molding characteristics”), and the solar cell element is subjected to external impact. Flexibility is required to ensure impact resistance for protection from damage. On the other hand, the back surface protection sheet is not required to be as flexible as the sealing material sheet because it is required to have excellent barrier properties and weather resistance that reliably block the penetration of moisture and the like. A resin with a high density and a high melting point tends to be selected. This is also a factor that makes it difficult to improve the durability of adhesion between these two layers.

  In order to solve the above-described problem concerning the adhesion durability between the sealing material sheet and the back surface protective sheet in the solar cell module, for example, by providing an easy-adhesion layer on one surface of the back surface protective sheet, the back surface protective sheet and the sealing material are sealed. A solar cell module characterized by remarkably enhancing the adhesiveness with a stopper is disclosed (Patent Document 3). However, the solar cell module of Patent Document 3 must be further laminated with a primer layer in addition to an adhesive layer formed of an adhesive, which increases costs and is preferable from the viewpoint of productivity. Absent. Therefore, there has been a strong demand for the development of a sealing material sheet-integrated back surface protection sheet that can maintain the adhesion durability between the sealing material sheet and the back surface protection sheet without providing other layers such as a primer layer. .

JP 2000-91611 A JP 2009-10277 A JP 2012-216777 A

  The present invention has been made in view of the above situation, and is a sealing material-integrated back protective sheet including a sealing material sheet mainly using low-density polyethylene, and is used for a long time of a solar cell module. Thus, an object of the present invention is to provide a highly reliable sealing material-integrated back surface protection sheet having excellent adhesion durability between the sealing material sheet and the back surface protection sheet.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, pay attention to the ratio of the linear expansion coefficient between the sealing material sheet and the back surface protection sheet constituting the sealing material integrated back surface protection sheet, and the ratio of the linear expansion coefficient between the sealing material sheet and the back surface protection sheet The sealing material sheet of the adhesive layer laminated between the sealing material sheet and the back surface protection sheet, if the sealing material integrated back surface protection sheet with optimized adhesion between the back surface protection sheet, the above The present inventors have found that the problem can be solved and have completed the present invention.

(1) A mode in which the sealing material sheet, which is a multilayer sheet having a core layer and a skin layer, an adhesive layer, and a back surface protection sheet are exposed on the outermost layer side of the sealing material sheet. A sealing material-integrated back surface protection sheet for a solar cell module that is laminated, wherein the core layer and the skin layer of the sealing material sheet have a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less. The low-density polyethylene is contained in an amount of 60% by mass or more in the total resin component of each layer composition, the film thickness of the sealing material sheet is 200 μm or more and 400 μm or less, and the sealing with respect to the linear expansion coefficient of the back surface protection sheet The ratio of the linear expansion coefficient of the material sheet is 10 or more and 1000 or less, and the adhesion force between the sealing material sheet and the back surface protection sheet of the adhesive layer measured by the following adhesion test is 30 N / 1. Sealing material integral back protective sheet is mm.
Adhesion test: After pressing for 10 minutes at 150 ° C. and 100 kPa, a back protection sheet sample piece that is in close contact with the sealing material integrated back protection sheet piece cut to a width of 15 mm is 180 ° C. with a peeling tester at 25 ° C. Degree peel (50 mm / min) test is performed to measure the adhesion strength.

  (2) The sealing material-integrated back surface protection sheet according to (1), wherein the sealing material sheet is a multilayer sheet having a three-layer structure of skin layer / core layer / skin layer.

  (3) In the core layer of the encapsulant sheet, polypropylene is contained in an amount of 5% by mass or more and 40% by mass or less in the total resin component of the core layer composition. (1) or (2) Back protection sheet.

  (4) The sealing material-integrated back protective sheet according to any one of (1) to (3), wherein the back protective sheet includes a polyethylene terephthalate resin and / or a hydrolysis-resistant polyethylene terephthalate resin.

  (5) In the aspect in which the skin layer of the encapsulant sheet faces the non-light-receiving surface side of the solar cell element, the encapsulant-integrated back protective sheet according to any one of (1) to (4), A stacked solar cell module.

  The sealing material-integrated back surface protection sheet of the present invention is a highly reliable sealing material-integrated back surface protection sheet that has excellent durability of adhesion between the sealing material sheet and the back surface protection sheet due to the long-term use of the solar cell module. is there.

It is a schematic diagram of the cross section which shows the layer structure of the sealing material sheet of one Embodiment of this invention. It is a schematic diagram of the cross section which shows the layer structure of the sealing material integrated back surface protection sheet which uses the sealing material sheet of one Embodiment of this invention. It is a schematic diagram of the cross section which shows an example of the laminated constitution of the solar cell module which uses the sealing material integrated back surface protection sheet of one Embodiment of this invention. It is a schematic diagram of the cross section which shows an example of the laminated constitution of the conventional common solar cell module.

  Hereinafter, one embodiment of the sealing material-integrated back protective sheet of the present invention and a solar cell module using the same 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 10 including the sealing material-integrated back surface protection sheet of the present embodiment will be described with reference to FIG. The solar cell module 10 is arranged on the outermost layer on the light receiving surface side from the non-light receiving surface side, the sealing material integrated back surface protection sheet 1, the solar cell element 2, the light receiving surface side sealing material sheet 3 of the present embodiment. The transparent front substrate 4 is laminated in order.

  Here, FIG. 4 shows a layer structure of a conventional general solar cell module (solar cell module 10A). The conventional solar cell module 10A includes a back surface protection sheet 6, a non-light receiving surface side sealing material sheet 5, a solar cell element 2, a light receiving surface side sealing material sheet 3, and an outermost layer on the light receiving surface side from the non-light receiving surface side. The transparent front substrate 4 disposed on the substrate is sequentially stacked.

  The sealing material-integrated back surface protection sheet 1 of the present embodiment includes a sealing material sheet 11 relating to the present embodiment that can be thinned while maintaining heat resistance and the like, and a back surface protection sheet 12 having a barrier property. It is a multilayer sheet formed by lamination (see FIG. 2). Therefore, in the solar cell module 10 using this, the solar cell module is made thinner than the conventional general solar cell module 10A in which the conventional sealing material sheets are laminated on both sides of the solar cell element 3. Can be realized.

  As the solar cell element 2 used in the solar cell module 10, for example, amorphous silicon type, crystalline silicon type, CdTe type, CIS type, GaAs type, and other various conventionally known solar cell elements can be used. .

  The light-receiving surface side sealing material sheet 3 is a resin sheet disposed in the solar cell module 10 so as to cover the surface of the solar cell element 2 mainly in order to protect the solar cell element 2 from external impact. As the resin base material forming the light-receiving surface side sealing material sheet 3, thermoplastic resins such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), and polyethylene can be used as appropriate.

  The transparent front substrate 4 is generally a glass substrate. The transparent front substrate 4 is not particularly limited as long as it maintains the weather resistance, impact resistance, and durability of the solar cell module 10 and transmits sunlight with high transmittance.

  For example, as a general aspect in the conventional solar cell module 10A (FIG. 4), the thickness of the back surface protection sheet 6 is about 70 μm to 200 μm, and the thickness of the non-light-receiving surface side sealing material sheet 5 is 400 to 400 μm. Since it is about 600 micrometers, the total thickness of the resin base material layer containing the sealing material sheet laminated | stacked on the non-light-receiving surface side of the solar cell element 2 and a back surface protection sheet will be about 500 micrometers to about 800 micrometers. On the other hand, in the solar cell module 10 (FIG. 3) of the present invention, the total thickness of the sealing material-integrated back protective sheet 1 laminated on the non-light-receiving surface side of the solar cell element 2 is about 300 μm to 600 μm. It can be. Moreover, it is also possible to make the total thickness of a solar cell module still thinner by arrange | positioning the sealing material sheet of the aspect which does not contain a colored pigment as a light-receiving surface side sealing material sheet.

<Encapsulant integrated back protection sheet>
As shown in FIG. 2, the sealing material-integrated back surface protection sheet 1 is a multilayer resin sheet formed by integrally forming a sealing material sheet 11 and a back surface protection sheet 12. The thickness of the sealing material-integrated back surface protection sheet 1 is not particularly limited, but a thickness in the range of about 300 μm to 600 μm is a general example, and the thickness is in the range of 350 μm to 480 μm. Can be given as specific examples of more preferred embodiments. And the sealing material integrated back surface protection sheet 1 is arrange | positioned and used in the solar cell module 10 in the aspect in which the sealing material sheet 11 faces the non-light-receiving surface side of the solar cell element 2. Hereinafter, the linear expansion coefficient regarding the sealing material integrated back surface protection sheet of this embodiment will be described.

[Linear expansion coefficient]
Here, as described above, generally, the sealing material sheet in the solar cell module is required to have high flexibility, while the back surface protection sheet 12 is required to have high weather resistance of the solar cell module. As a result, a material having a high linear expansion coefficient was selected as the sealing material sheet 11, while a material having a low linear expansion coefficient was used as the material of the back surface protection sheet 12. On the other hand, the sealing material-integrated back surface protection sheet 1 of the present embodiment has a large linear expansion coefficient ratio between the sealing material sheet 11 and the back surface protection sheet 12 that has not been particularly noted in the past. By paying attention to the above, by controlling this difference within a specific range, the long-term adhesion durability between these layers is sufficiently improved.

  Specifically, in the sealing material-integrated back surface protection sheet 1, the ratio of the linear expansion coefficient of the sealing material sheet 11 to the linear expansion coefficient of the back surface protection sheet 12 constituting the sealing material sheet is 10 or more and 1000 or less. The sealing material-integrated back surface protection sheet 1 of the present embodiment is configured so that the ratio of the linear expansion coefficient of the sealing material sheet 11 to the linear expansion coefficient of the back surface protection sheet 12 is 10 or more and 1000 or less. It has significance in that the adhesion durability between the encapsulant sheet 11 and the back surface protection sheet 12 can be improved and the highly reliable encapsulant integrated back surface protection sheet can be provided.

  The ratio of the linear expansion coefficient of the sealing material sheet 11 with respect to the linear expansion coefficient of the back surface protection sheet 12 is 10 or more, so that the flexibility of the sealing material sheet 11 and the weather resistance of the back surface protection sheet 12 are in a preferable range. be able to. When the ratio of the linear expansion coefficient is 1000 or less, the adhesion durability between the sealing material sheet 11 and the back surface protection sheet 12 due to long-term use of the solar cell module 10 is high, and the sealing material is highly reliable. It can be set as a body-type back surface protection sheet.

  In addition, it is preferable that the ratio of the linear expansion coefficient of the sealing material sheet 11 with respect to the linear expansion coefficient of the back surface protection sheet 12 is 10 or more and 100 or less.

  Next, an example of the sealing material sheet 11 and the back surface protection sheet 12 that can make the ratio of the linear expansion coefficient of the sealing material sheet 11 to the linear expansion coefficient of the back surface protection sheet 12 10 or more and 1000 or less will be described. The sealing material sheet 11 and the back surface protection sheet 12 relating to the present invention are not limited to the following embodiments, and can be appropriately modified and implemented within a range in which the object of the present invention can be achieved.

[Encapsulant sheet]
The encapsulant sheet 11 according to this embodiment is a multilayer sheet having a core layer 111 and a skin layer 112. The encapsulant sheet 11 may have a layer configuration in which the skin layer 112 is laminated only on one surface of the core layer 111, but as shown in FIG. 1, the encapsulant sheet 11 has a skin layer / core layer / A multilayer sheet having a three-layer structure of skin layers is preferred. In any of the above configurations, the encapsulant sheet 11 is required for the encapsulant sheet 11 for a solar cell module by blending the resin composition components described below for each layer with an optimum composition. While maintaining various required physical properties such as heat resistance, heat processing suitability, flexibility, substrate adhesion, etc., it is possible to sufficiently respond to requests for thinning solar cell modules.

  The thickness of the encapsulant sheet 11 is in the range of 200 μm or more and 400 μm or less, preferably in the range of 250 μm or more and 350 μm or less. The physical properties can be maintained. In the case where the encapsulant sheet 11 is a multilayer sheet having a three-layer structure of skin layer / core layer / skin layer, the thickness ratio thereof is the thickness ratio of skin layer: core layer: skin layer. The range of 1: 3: 1 to 1: 30: 1 is preferred.

The core layer 111 and the skin layer 112 contain 60% by mass or more of low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in the total resin component of each layer composition. When the low-density polyethylene is contained in the sealing material sheet 11 in such a range, the sealing material sheet 11 having transparency and flexibility can be obtained. In addition, in the total resin component of each layer composition, the core layer 111 means the total resin component of the core layer 111 composition, and the skin layer 112 means the total resin component of the skin layer 112 composition. .

(Core layer)
The core layer 111 mainly has a function of imparting heat resistance and appropriate rigidity to the encapsulant sheet 11. The core layer 111 contains 60% by mass or more of low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in the total resin component of the core layer composition. From the viewpoint of preventing laminator contamination caused by melting of the resin derived from the resin, it is preferable to further contain a heat-resistant resin having higher heat resistance than the low-density polyethylene (hereinafter sometimes simply referred to as a heat-resistant resin). Examples of such a heat resistant resin include polypropylene.

  An example of the thickness of the core layer 111 is 40 μm or more and 240 μm or less, and is not particularly limited. When the thickness of the core layer 111 is 40 μm or more, good dimensional stability can be imparted to the encapsulant sheet 11. In addition, when the thickness of the core layer 111 is 240 μm or less, the encapsulating sheet 11 can be given sheet transportability at the time of lamination.

(Core layer composition)
The core layer 111 is not particularly limited as long as it contains 60% by mass or more of low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in the total resin components of the core layer composition. The low density polyethylene contained in the core layer 111 is preferably a low density polyethylene having a density of 0.910 g / cm ³ or more and 0.940 g / cm ³ or less. Moreover, it is preferable that low density polyethylene is 60 mass% or more and 95 mass% or less in all the resin components of a core layer composition, More preferably, it is 75 mass% or more and 85 mass% or less. The core layer composition preferably further contains a heat resistant resin, and among the heat resistant resins, it is preferred that polypropylene is contained. Polypropylene is preferably 5% by mass or more and 40% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and still more preferably 10% by mass or more and 25% by mass or less in the total resin component of the core layer composition. The core layer 111 is a layer made of a mixed resin of low-density polyethylene and polypropylene, and is a layer that mainly functions as a layer that imparts heat resistance and dimensional stability to the sealing material 11.

  As the polypropylene that can be contained in the core layer composition in the above predetermined amount range, it is more preferable to use a homopolypropylene (homo PP) resin. Homo PP is a polymer composed only of polypropylene and has high crystallinity, and therefore has higher rigidity than block PP and random PP. By using this as an additive resin to the core layer composition, the dimensional stability of the encapsulant sheet 11 can be further enhanced. Moreover, it is preferable that MFR in 230 degreeC of homo PP is 5 g / 10min or more and 12 g / 10min or less. When the MFR is less than 5 g / 10 minutes, the molecular weight increases and the rigidity becomes too high, and the preferable and sufficient flexibility of the encapsulant sheet 11 cannot be secured even by the physical properties of the skin layer 12. If the MFR exceeds 12 g / 10 minutes, the fluidity during heating is not sufficiently suppressed, and the sealing material sheet 11 can be sufficiently provided with heat resistance and dimensional stability as described above. Absent. In addition, unless otherwise specified, “MFR” in the present specification is the value of MFR at 190 ° C. and a load of 2.16 kg measured according to JIS7210 (however, the same applies to the MFR of polypropylene resin) MFR value at 230 ° C. and a load of 2.16 kg).

However, polypropylene has a rigidity much higher than that of low-density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in any of the above structures. Therefore, for example, when polypropylene exceeding 40% by mass is added to the core layer composition exceeding the appropriate addition amount range, the physical properties of polypropylene in the core layer 111 become excessively superior, and the encapsulant sheet The preferable flexibility as a whole cannot be secured even by the physical properties of the skin layer 112.

  By mixing a heat-resistant resin such as polypropylene within the above content range, even when the encapsulant sheet 11 is a thin sheet of 400 μm or less, the encapsulant sheet 11 can have good heat resistance. Therefore, it is preferable. Further, by imparting sufficient heat resistance to the encapsulant sheet 11, it is also possible to suppress the occurrence of curl deformation of the encapsulant sheet 11, which is likely to be a problem particularly during vacuum lamination processing in the production of a solar cell module.

  The core layer 111 can further contain an inorganic filler. Thereby, the rigidity of the core layer 111 is increased and the occurrence of undesirable curl deformation of the encapsulant sheet 11 can be suppressed. Such inorganic fillers include talc (hydrous magnesium silicate) or 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, aluminum powder, mica, barium carbonate, or the like can be used. The inclusion of the inorganic filler in the core layer composition forming the core layer 111 is not essential, and the content thereof may be in the range of 0% by mass to 30% by mass in the total resin components of the core layer composition. .

  In addition, when it is calculated | required that the back surface protection sheet 12 has a colored external appearance, it is excellent in a weather resistance among said inorganic fillers, and it is easy to obtain including price and easy to obtain. Therefore, the white pigment may further include titanium oxide and the like, and the black pigment may further include carbon black and the like. The inclusion of these colored pigments is preferable in that it can improve the power generation efficiency due to re-reflection of sunlight or meet the demands on the design.

(Skin layer)
The skin layer 112 is a layer mainly disposed in the outermost layer of the sealing material-integrated back protective sheet 1. In the solar cell module 10, the skin layer 112 is in close contact with the surface on the non-light receiving surface side of the solar cell element 2 and the light receiving surface side sealing material sheet 3, or in close contact with the back surface protective sheet 12 as necessary. It becomes. In particular, in the former case, it contributes to the improvement of the adhesion of the sealing material sheet 11 and the molding characteristics for integration as a solar cell module.

  The thickness of the skin layer 112 may be appropriately determined in consideration of the thickness (thinness) required for the sealing material sheet 11. As an example, when the skin layer 112 has a layer configuration in which the skin layer 112 is laminated on one surface of the core layer 111, a preferable thickness of the skin layer 112 is 3 μm or more and 150 μm or less. When the thickness of the skin layer 112 is 3 μm or more, sufficient adhesion and molding characteristics can be imparted to the encapsulant sheet 11.

  When the skin layer 112 is formed on both surfaces of the core layer 111, a colored pigment can be contained in any one of the two layers. In this case, it is preferable that at least the outermost surface of the other skin layer 112 preferably contains no colored pigment over substantially the entire other skin layer. The encapsulant-integrated back surface protective sheet 1 having such a layer configuration is preferably disposed in the solar cell module 10 so that one skin layer 112 containing a colored pigment faces the back surface protective sheet 12. Thereby, in the solar cell module 10, the sealing material sheet 11 can exhibit the light reflection function on the non-light-receiving surface side of the solar cell element 2, and can contribute to the improvement of the power generation rate of the solar cell module 10. At this time, if it is assumed that the other skin layer 112 does not contain a colored pigment, the load derived from the pigment on the solar cell element is reduced in the laminating step when integrating as a solar cell module, and the solar cell The occurrence of cracking of the element can be suppressed. In addition, it is possible to avoid the wraparound of the white pigment to the light receiving surface side of the solar cell element, which causes a decrease in power generation efficiency in the laminating step. Therefore, it is preferable that the other skin layer 112 does not contain a colored pigment.

(Skin layer composition)
The skin layer 112 is not particularly limited as long as it contains 60% by mass or more of low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in the total resin components of the skin layer composition. The low density polyethylene is preferably a low density polyethylene having a density of 0.880 g / cm ³ or more and 0.910 g / cm ³ or less. The low density polyethylene is preferably 80% by mass or more and 100% by mass or less, more preferably 98% by mass or more and 100% by mass or less, based on the total resin component of the skin layer composition. And unlike a core layer composition, it is preferable that a skin layer composition does not contain heat resistant resins, such as a polypropylene. As described above, the skin layer 112 is preferably a layer mainly composed of low-density polyethylene having a lower density than the base resin of the core layer composition from the viewpoint of imparting molding characteristics and adhesion to the skin layer 112.

  For the skin layer composition, low density polyethylene (LDPE) in the above density range, more preferably a copolymer of ethylene and α-olefin, and linear low density polyethylene (LLDPE) in the above density range is used. be able to. By giving the kind, density range, and content ratio of the adhesion component within the above-described composition range, a preferable flexibility is imparted to the encapsulant sheet 11 of the encapsulant-integrated back protective sheet 1 having the skin layer 112. Can do.

  The skin layer composition preferably contains silane-modified polyethylene at a predetermined ratio. The silane-modified polyethylene resin is obtained by graft-polymerizing an ethylenically unsaturated silane compound as a side chain to linear low-density polyethylene (LLDPE) or the like as a main chain. Since such a graft copolymer has a high degree of freedom of silanol groups contributing to the adhesive force, the adhesion of the encapsulant sheet 11 of the encapsulant-integrated back surface protective sheet 1 can be further improved.

  The amount of grafting that is the content of the ethylenically unsaturated silane compound is such that the amount of grafting 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. Preferably, it may be appropriately adjusted so that it is 0.05 parts by mass or less, more preferably 0.1 parts by mass or more and 1.0 part by mass or less. When the content of the ethylenically unsaturated silane compound is large, the mechanical strength and the heat resistance are excellent. However, when the content is excessive, the tensile elongation and the heat fusion property tend to be inferior.

  The silane-modified polyethylene resin can be produced, for example, by the method described in JP-A-2003-46105. By using the resin as a component of a sealing material composition for a solar cell module, strength and durability can be increased. In addition, it has excellent weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics, and also affects manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. It is possible to manufacture solar cell modules that have extremely excellent heat-sealability without being received, that are stable, low-cost, and suitable for various applications.

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

(Other ingredients)
The skin layer composition and the core layer composition may further contain other components. For example, components such as various weather resistance master batches, various fillers, light stabilizers, ultraviolet absorbers, heat stabilizers and the like for imparting weather resistance to the encapsulant sheet 11 are exemplified. These contents vary depending on the particle shape, density and the like, but are preferably in the range of 0.001% by mass or more and 5% by mass or less in the total resin composition of the sealing material sheet 11, respectively. . By including these additives, the sealing material sheet 11 of the sealing material-integrated back surface protection sheet 1 is provided with a long-term improvement in mechanical strength, an effect of preventing yellowing, cracking, and the like. Can do.

[Back protection sheet]
As the back surface protection sheet 12 constituting the sealing material integrated back surface protection sheet 1, various resin sheets that have been conventionally used as back surface protection sheets for solar cell modules can be used. Examples of the resin sheet forming the back protective sheet 12 include polyethylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride resin, poly (Meth) acrylic resins, polycarbonate resins, polyethylene terephthalate (PET), polyester resins such as polyethylene naphthalate, polyamide resins such as various nylons, polyimide resins, polyamideimide resins, polyarylphthalate resins, Various resin sheets such as silicone resins, polysulfone resins, polyphenylene sulfide resins, polyether sulfone resins, polyurethane resins, acetal resins, and cellulose resins can be used. Among these, polyethylene terephthalate (PET) can be preferably used from the viewpoints of physical properties such as insulation performance, mechanical strength, cost, transparency, and economy. In addition, from the viewpoint of further improving mechanical strength and water vapor barrier properties, a multilayer sheet obtained by further laminating hydrolysis resistant PET in the outermost layer in addition to the above PET can be particularly preferably used as the back surface protective sheet 12. .

  Although the thickness of the back surface protection sheet 12 is not particularly limited, it is required for the sealing material-integrated back surface protection sheet 1 as long as the physical properties such as the barrier property of water vapor required for the back surface protection sheet 12 can be maintained. What is necessary is just to determine suitably considering thickness. The thickness of the back surface protective sheet 12 is preferably 50 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less. When the thickness of the back surface protection sheet 12 is 50 μm or more, preferable durability and weather resistance can be imparted to the sealing material integrated back surface protection sheet 1.

  In addition, the back surface protection sheet 12 can also be preferably used in which a weathering layer (not shown) is further laminated on one surface assumed to be the outermost layer side when integrated with the solar cell module 10. . As the weather resistant layer, a layer excellent in weather resistance, heat resistance, light resistance and the like is used. As the base material for forming the weather resistant layer, hydrolysis resistant polyethylene terephthalate (hydrolysis resistant PET), PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ester copolymer), PTFE Preferred examples include resin sheets such as fluorine-based resins such as (polytetrafluoroethylene), ETFE (tetrafluoroethylene / ethylene copolymer), PVDF (polyvinylidene fluoride), and aluminum sheets. Among the above, hydrolysis resistant PET can be particularly preferably used. Hydrolysis-resistant PET refers to polyethylene terephthalate having excellent hydrolysis resistance described in JP2012-62380A. This hydrolysis-resistant PET is polyethylene terephthalate containing 2 to 100 ppm of an alkali metal element and 10 to 250 ppm of a phosphorus element, and further polyoxyalkylene with respect to 100 parts by mass of the polyethylene terephthalate resin composition. It is a resin containing 2 to 20 parts by mass of glycol. Hydrolysis-resistant PET is excellent in hydrolysis resistance, and also in heat resistance and durability required for a protective sheet disposed on the back side of the solar cell module. Moreover, since it is excellent in workability and is relatively inexpensive, it can be used very preferably as a material for forming the weather resistant layer of the back surface protective sheet 12.

  In addition, the weather-resistant layer of the back surface protection sheet 12 may be obtained by forming a weather-resistant coating layer on the surface of the base material layer by surface processing such as fluorine coating, EB coating, or silica deposition. Furthermore, the above-mentioned weather-resistant resin sheet or the like having a required strength by a predetermined thickness or processing can be used as the back surface protection sheet 12.

[Adhesive layer]
In the sealing material-integrated back surface protection sheet 1 according to this embodiment, a sealing material sheet 11, an adhesive layer 13, and a back surface protection sheet 12 are laminated. Integration of the sealing material sheet 11 and the back surface protection sheet 12 is performed via an adhesive layer. Moreover, the adhesive force between the sealing material sheet | seat of an adhesive bond layer and a back surface protection sheet shall be 30 N / 15mm, and it is preferable that it is 32 N / 15mm or more. The sealing material including the core layer 111 and the back surface protective sheet 12 of the sealing material sheet 11 having different linear expansion coefficients by setting the adhesive force between the sealing material sheet of the adhesive layer and the back surface protective sheet in such a range. Even if it is the integrated back surface protection sheet 1, it is possible to obtain a highly reliable sealing material integrated back surface protection sheet having excellent adhesion durability between the sealing material sheet and the back surface protection sheet by long-term use of the solar cell module. it can.

The adhesion strength is measured by the following adhesion test.
Adhesion test: After pressing for 10 minutes at 150 ° C. and 100 kPa, a back protection sheet sample piece that is in close contact with the sealing material integrated back protection sheet piece cut to a width of 15 mm is 180 ° C. with a peeling tester at 25 ° C. Degree peel (50 mm / min) test is performed to measure the adhesion strength.

  The adhesive capable of forming the adhesive layer 13 is not particularly limited as long as the adhesive strength between the sealing material sheet and the back surface protective sheet of the adhesive layer is 30 N / 15 mm. A two-component curable dry laminate adhesive composed of an epoxy-based main agent and a curing agent can be used as appropriate.

  The lamination of the adhesive layer 13 is preferably performed by a dry lamination method. However, as long as it can maintain desired adhesion and durability, it may be integrated by other conventionally known means. For example, by the extrusion coat laminating method in which the resin composition that becomes the encapsulating material sheet 11 is directly extruded onto the surface of the back surface protective sheet 12 by an extruder to form the encapsulating material sheet 11, and the sandwich lamination method that is an application form thereof. Also, the sealing material sheet 11 and the back surface protection sheet 12 can be integrated into the sealing material integrated back surface protection sheet 1.

<Sealing material sheet and back surface protection sheet>
By using the sealing material sheet 11 and the back surface protection sheet 12 described above, the ratio of the linear expansion coefficient of the sealing material sheet 11 to the linear expansion coefficient of the back surface protection sheet 12 is preferably 10 or more and 1000 or less. For example, the core layer of the encapsulant sheet 11 is 90 parts by mass of low density polyethylene (density 0.920 g / cm ³ , melting point 123 ° C.) and 10 parts of homo PP (density 0.900 g / cm ³ , melting point 155 ° C.). And the skin layer of the encapsulant sheet 11 is 85 parts by mass of linear low density polyethylene (density 0.898 g / cm ³ , melting point 97 ° C.), silane-modified polyethylene resin (density 0.901 g / cm ³ MFR1). 0.1 g / 10 min) and 15 parts by mass, and each blend was formed into a sheet at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a sheet molding machine having a 200 mm wide T-die, When these are used as the three-layer encapsulant sheet 11 of skin layer / core layer / skin layer, the linear expansion coefficient of the encapsulant sheet 11 at 30 ° C. is 36.5 ppm / K. On the other hand, when a PET film is used as the back surface protective sheet 12, the linear expansion coefficient at 30 ° C. of the back surface protective sheet 12 is 1.1 ppm / K. Therefore, the ratio of the linear expansion coefficient of the sealing material sheet 11 to the linear expansion coefficient of the back surface protection sheet 12 is 33, and a preferable integrated back surface protection sheet can be obtained.

<Method for producing sealing material-integrated back surface protection sheet>
The manufacturing method of the sealing material integrated back surface protection sheet 1 of this embodiment is demonstrated. The sealing material-integrated back surface protection sheet 1 includes a “back surface protection sheet forming step” for forming the back surface protection sheet 12, a “sealing material sheet forming step” for forming the sealing material sheet 11, and the back surface protection sheet 12. It can be manufactured by going through an “integration step” in which the sealing material sheet 11 is laminated and integrated.

(Back surface protection sheet forming process)
The back surface protection sheet 12 is formed by depositing 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, other film forming methods, or the like. Can do. In addition, the back surface protection sheet 12 may contain other additives, such as a pigment other than the said resin material, in the range which does not impair the effect of this invention.

(Encapsulant sheet forming process)
The encapsulant sheet 11 can be obtained by integrally forming the above-described skin layer composition and core layer composition by a known coextrusion method to form a multilayer sheet.

(Integration process)
The sealing material sheet 11, the back surface protection sheet 12, and a sheet for forming other layers formed by the same method as necessary are appropriately laminated and further integrated, whereby the sealing of this embodiment is performed. The stop material-integrated back protective sheet 1 can be obtained. The integration of the sheets can be performed by a conventionally known dry laminating method.

<Method for manufacturing solar cell module>
The solar cell module 10 is, for example, vacuum-sucked after sequentially laminating the members including the transparent front substrate 4, the light-receiving surface side sealing material sheet 3, the solar cell element 2, and the sealing material integrated back surface protection sheet 1. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method. 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, particularly preferably in the range of 8 to 15 minutes. In this way, the solar cell module 10 can be manufactured by thermocompression-bonding each of the above layers as an integrally formed body.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

<Manufacture of sealing material sheet>
Each encapsulant sheet was created by the following method according to the above-described “manufacturing method of encapsulant sheet”.

  Each of the following materials mixed in the composition shown in Table 1 was used separately as a blend for the core layer and skin layer of each encapsulant sheet. Each of these blends was formed into a sheet at an extrusion temperature of 210 ° C. and a take-off speed of 1.1 m / min using a φ30 mm extruder and a sheet molding machine having a 200-mm-wide T die, and these were formed into a skin layer / core layer. / A three-layer sealing material sheet of skin layer was used. The total thickness of each encapsulant sheet and the thickness of each layer were 50 μm for each skin layer, 200 μm for the core layer, and 300 μm for the layer thickness for any encapsulant sheet.

The following raw materials were used as the material for the encapsulant sheet.
Low density polyethylene 1 (LDPE, indicated as “LD1” in the table): density 0.920 g / cm ³ , melting point 123 ° C.
Low density polyethylene 2 (LDPE, indicated as “LD2” in the table): density 0.920 g / cm ³ , melting point 105 ° C.
Linear low-density polyethylene (LLDPE, indicated as “LLD” in the table): density 0.898 g / cm ³ , melting point 97 ° C.
Silane-modified polyethylene resin (denoted as “SiPE” in the table): with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.901 g / cm ³ and MFR of 1.1 g / 10 min. 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., and a silane having a density of 0.901 g / cm ³ . A modified transparent resin was obtained.
Polypropylene (PP, indicated as “PP” in the table): homopolypropylene. Density 0.900 g / cm ³ , melting point 155 ° C. MFR 8.5 g / 10 min (230 ° C.).
White pigment: Titanium oxide having an average particle size of 0.2 μm. 7 parts by mass per 100 parts by mass of the resin component is added only to the core layer of the sealing material sheets of all Examples and Comparative Examples.
UV absorber: manufactured by Chemipro Kasei Co., Ltd., trade name KEMISORB12. All 0.3 parts by mass are added to each of the encapsulant compositions for the core layer and skin layer of all Examples and Comparative Examples.
Weathering stabilizer: BASF Corporation, trade name Tinuvin 622SF. 0.2 parts by mass are added to each of the sealing material compositions for the core layer and skin layer of all Examples and Comparative Examples.
Antioxidant: Ciba Japan Co., Ltd., trade name Irganox 1076. 0.05 parts by mass are added to each of the encapsulant compositions for the core layers and skin layers of all Examples and Comparative Examples.

<Manufacture of adhesives>
[Manufacture of main agent]
1. Production of polyurethane diol 100 parts by mass of an aliphatic polycarbonate diol having a number average molecular weight of 1000 (trade name “Duranol T5651” (hereinafter referred to as “PDC1000”) manufactured by Asahi Kasei Chemicals Corporation) in a flask equipped with a stirrer under a nitrogen atmosphere, 1,6-hexanediol (5 parts by mass), isophorone diisocyanate (27.5 parts by mass), and ethyl acetate (132.5 parts by mass) are added, and absorption of 2270 cm ⁻¹ isocyanate disappears in the infrared absorption spectrum. The mixture was heated to reflux until a 50% solution of polyurethane diol A-1 was obtained. The obtained resin had a hydroxyl value of 14 mg KOH / g and a number average molecular weight of about 8,000.

2. Production of Aliphatic Polycarbonate Diol An aliphatic polycarbonate diol was prepared as the aliphatic polycarbonate diol as the main component. The aliphatic polycarbonate diol is an aliphatic polycarbonate diol having a number average molecular weight of 1000 (manufactured by Asahi Kasei Chemicals Corporation, trade name “Duranol T5651”).

3. Preparation of Main Agent A main agent was prepared using polyurethane diol and aliphatic polycarbonate diol, which are the main component components produced above. The main agent was prepared by blending 15 parts by mass of aliphatic polycarbonate diol with 100 parts by mass of polyurethane diol.

[Manufacture of curing agent]
A curing agent was produced as a curing agent constituting the adhesive. In addition, as a material for the curing agent, isophorone diisocyanate nurate and hexamethylene diisocyanate bifunctional polyurethane diisocyanate ("Duranate D101" manufactured by Asahi Kasei Chemicals Corporation) were used. The blending ratio (mass) of isophorone diisocyanate nurate: hexamethylene diisocyanate bifunctional polyurethane diisocyanate was 40:60. In addition, although the said mixture ratio (mass) is a solid mass ratio which does not contain a solvent, it prepared to 50% of solid content in manufacture.

[Combination of main agent and curing agent]
An adhesive was produced using the main agent and curing agent produced above. In addition, the main agent and the curing agent were blended by dissolving the main agent and the curing agent in a solvent to make each 50 mass% (ethyl acetate solution). The main agent and the curing agent were adjusted at a mass ratio of 18: 3.7.

<Manufacture of sealing material-integrated back surface protection sheet>
Each of the above sealing material sheets and a PET film (“Melinex S” manufactured by Teijin DuPont Co., Ltd., thickness 125 μm) subjected to corona treatment on the surface are used as a bonding agent by the dry laminating method. Thus, the sealing material-integrated back protective sheet of each example was obtained.

  In addition, the ratio of the linear expansion coefficient of the sealing material sheet 11 with respect to the linear expansion coefficient of the back surface protection sheet 12 is shown in Table 1 (expressed as a linear expansion coefficient ratio in Table 1). Moreover, the adhesive force between the sealing material sheet | seat of a sealing material integrated back surface protection sheet of each Example and a back surface protection sheet is shown in Table 1 (it describes with adhesive force (N / 15mm) in Table 1).

<Comparative example>
Prepare each of the above sealing material sheets and corona-treated PET film (“Melinex S”, manufactured by Teijin DuPont Co., Ltd., thickness: 125 μm) separately, and press-bond at 100 kPa for 10 minutes at 150 ° C. with a vacuum laminator. And the laminated body sample of the sealing material which concerns on a comparative example, and a back surface protection sheet was manufactured.

In addition, the adhesive force was measured by the following adhesion test.
Adhesion test: After pressing for 10 minutes at 150 ° C. and 100 kPa, a back protection sheet sample piece that is in close contact with the sealing material integrated back protection sheet piece cut to a width of 15 mm is 180 ° C. with a peeling tester at 25 ° C. Degree peel (50 mm / min) test is performed to measure the adhesion strength.

  About each sealing material integrated back protection sheet of the said Example and a comparative example, based on the test method and evaluation criteria of the following description, it measured and evaluated about the maintenance factor of the power generation efficiency at the time of assuming an actual use environment. . The results are shown in Table 1.

<Evaluation of laminator contamination during laminating>
White plate semi-tempered glass, solar cell element (manufactured by Q-CELLS, cell Q6LTT-200 / 152 156 mm) (2 × 2), sealing material sheet for light-receiving surface side, and examples and comparative examples “ "Sealant-integrated back surface protection sheet" is laminated in the order of white plate semi-tempered glass / light-receiving surface side sealing material sheet / solar cell element / sealing material / sealing material-integrated back surface protection sheet, Under the laminating conditions, a vacuum heating laminating process was performed, and solar cell module evaluation samples were obtained for the respective examples and comparative examples.

  Immediately after taking out the sample from the laminator, the hot plate at the lower part of the laminator and the rubber part of the top plate portion were visually observed to evaluate the presence or absence of laminator contamination during lamination. The evaluation results are shown in Table 1 as “Laminator contamination”.

(Lamination condition) Vacuum drawing: 5.0 minutes
Pressurization (0 kPa to 100 kPa): 1.0 minute
Pressure holding (100 kPa): 10.0 minutes
150 ° C

<Evaluation of power generation efficiency long-term maintenance ratio>
About each said solar cell module evaluation sample, Pmax value before and behind a thermal cycle test was measured, respectively, the maintenance factor of power generation efficiency was computed, and the power generation efficiency long-term maintenance factor was evaluated. The Pmax value is the maximum output value at the operating point where the output of the solar cell is maximum, and the power generation output of the module before and after the following thermal cycle test was measured based on JIS-C 8935-1995. In the thermal cycle, the sample for evaluation described above was put into an oven whose temperature changes in the following predetermined cycle, the sample was put into the oven, and the power generation efficiency before and after the elapse of 500 cycles was measured to calculate the ratio. . The cycle condition of the oven is to reciprocate between −20 ° C. and 90 ° C., the time required to change the temperature in the previous period is 5 hours, the time for maintaining the temperature is 1 hour, and starts from −20 ° C. to 90 ° C. The process of returning to −20 ° C. via one cycle was defined as one cycle. The results are shown in Table 1.

(Evaluation criteria for long-term power generation efficiency)
A: The power generation efficiency maintenance rate is 98% or more.
B: The power generation efficiency maintenance rate is 96% or more.
C: The power generation efficiency maintenance rate is less than 96%.

<Adhesion durability evaluation>
In said thermal cycle test, the peeling strength of the sealing material sheet of a sealing material integrated back surface protection sheet of the Example before and behind a thermal cycle test, and a back surface protection sheet of a comparative example was measured. For each sample, the peel strength (N) was measured for adhesion by 180-degree peel with a width of 15 mm. For the measurement, using a peeling test apparatus (manufactured by “A & D Co., Ltd., trade name“ TENSILON RTG-1210 ”), measurement is performed at 23 ° C. under a peeling condition of 50 mm / min by 180 ° peeling. The average value of four measurements was adopted. The peel strength retention rate was determined from the peel strength before the thermal cycle test and the peel strength after the thermal cycle test. The results are shown in Table 1 (in Table 1, expressed as adhesion durability).

(Adhesion durability evaluation criteria)
A: Peel strength maintenance rate is 90% or more.
B: Peel strength maintenance rate is 50% or more and less than 90%.
C: Peel strength maintenance rate is less than 50%.

  From Table 1, the ratio of the linear expansion coefficient of the sealing material sheet 11 with respect to the linear expansion coefficient of the back surface protection sheet 12 is 10 or more and 1000 or less, and the adhesive force between the sealing material sheet 11 of the adhesive layer and the back surface protection sheet 12 It can be seen that the encapsulant-integrated back surface protective sheet of the example in which is 30 N / 15 mm or more is preferable in terms of power generation efficiency maintenance rate and adhesion durability. Therefore, the sealing material-integrated back surface protection sheet of the present invention is a highly reliable sealing material-integrated back surface protection that has excellent durability of adhesion between the sealing material sheet and the back surface protection sheet due to long-term use of the solar cell module. It turns out that it is a sheet.

DESCRIPTION OF SYMBOLS 1 Sealing material integrated back surface protection sheet 11 Sealing material sheet 111 Core layer 112 Skin layer 12 Back surface protection sheet 13 Adhesive layer 2 Solar cell element 3 Light-receiving surface side sealing material sheet 4 Transparent front substrate 5 Non-light-receiving surface side sealing Stop sheet 6 Back surface protection sheet 10 Solar cell module 10A Solar cell module

Claims (5)

An encapsulant sheet that is a multilayer sheet having a core layer and a skin layer;
An adhesive layer;
A back surface protective sheet is a back surface protection sheet integrated with a sealing material for a solar cell module, which is laminated in such a manner that the skin layer of the sealing material sheet is exposed on the outermost layer side,
The core layer and the skin layer of the sealing material sheet contain 60% by mass or more of low density polyethylene having a density of 0.880 g / cm ³ or more and 0.940 g / cm ³ or less in the total resin component of each layer composition. ,
The sealing material sheet has a thickness of 200 μm or more and 400 μm or less,
The ratio of the linear expansion coefficient of the sealing material sheet to the linear expansion coefficient of the back surface protection sheet is 10 or more and 1000 or less,
The sealing material integrated back surface protection sheet whose contact | adhesion power between the said sealing material sheet of the said adhesive bond layer and the said back surface protection sheet measured by the following adhesive test is 30 N / 15mm or more.
Adhesion test: After pressing for 10 minutes at 150 ° C. and 100 kPa, a back protection sheet sample piece that is in close contact with the sealing material integrated back protection sheet piece cut to a width of 15 mm is 180 ° C. with a peeling tester at 25 ° C. Degree peel (50 mm / min) test is performed to measure the adhesion strength.   The encapsulant-integrated back protective sheet according to claim 1, wherein the encapsulant sheet is a multilayer sheet having a three-layer structure of skin layer / core layer / skin layer.   The encapsulant-integrated back protective sheet according to claim 1 or 2, wherein the core layer of the encapsulant sheet contains 5 mass% or more and 40 mass% or less of polypropylene in the total resin component of the core layer composition.   The sealing material-integrated back surface protection sheet according to any one of claims 1 to 3, wherein the back surface protection sheet includes a polyethylene terephthalate resin and / or a hydrolysis-resistant polyethylene terephthalate resin.   The solar in which the sealing material integrated back surface protection sheet according to any one of claims 1 to 4 is laminated in such a manner that the skin layer of the sealing material sheet faces the non-light-receiving surface side of the solar cell element. Battery module.

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