JP2018060845A - Sealant-integrated backside protection sheet for solar battery module, sealant-integrated backside protection sheet, and solar battery module arranged by use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealant-integrated backside protection sheet which can make contribution to the thinning of a solar battery module in thickness and the cutting of a manufacturing cost, and which can make contribution to the increase in long-term reliability of a solar battery module by exhibiting excellent contact durability when integrated into the solar battery module.SOLUTION: A sealant-integrated backside protection sheet 10 for a solar battery module is arranged by laminating a sealing material layer 1 and a backside protection layer 2. In the sealant-integrated backside protection sheet 10, the sealing material layer 1 has a multilayer structure, in which at least a core layer 11 and a first skin layer 12 include a silane-modified polyethylene; the first skin layer 12 is larger than the core layer 11 in content rate of the silane-modified polyethylene; and the second skin layer 13 does not include the silane-modified polyethylene, otherwise it includes the silane-modified polyethylene at a content rate smaller than that in the core layer 11.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.

  Conventionally, the layer structure shown in FIG. 4 is common for the layer structure of the solar cell module. That is, the transparent front substrate 5, the light receiving surface side sealing material sheet 4, the solar cell element 3, the non-light receiving surface side sealing material sheet 6, and the back surface protection sheet 7 are sequentially laminated from the light receiving surface side.

  Among the above-mentioned members constituting the solar cell module, as the sealing material sheet, a resin sheet made of ethylene-vinyl acetate copolymer resin (EVA) is used from the viewpoints of transparency, workability, manufacturing cost, and the like. It was used for general purposes. 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, in recent years, the sealing material sheet for solar cell modules which uses polyolefin resin instead of EVA resin is proposed, and the demand is expanding.

  As the back surface protective sheet disposed as a protective layer on the outermost layer of the solar cell module, resin sheets using a fluorine resin or a polyester resin such as polyethylene terephthalate (PET) are widely used. Furthermore, a multilayer sheet obtained by laminating these members such as a resin sheet having a barrier property by a dry laminating method or the like is used.

  In recent years, the above-described sealing material sheet and the back surface protection sheet are formed in advance as an integrated product for the purpose of reducing the thickness due to the design requirement for the solar cell module and improving the productivity by simplifying the manufacturing process. Development of a sealing material-integrated back surface protection sheet that has been made is also in progress (see Patent Document 1).

  This sealing material-integrated back surface protection sheet is used by being disposed on the non-light-receiving surface side of the solar cell module in the solar cell module 100, for example, as in the sealing material integrated back surface protection sheet 10 in FIG. Contributes to thinner solar cell modules and improved productivity.

  On the other hand, the encapsulant sheet constituting the encapsulant-integrated back surface protection sheet is laminated in a manner facing the back surface protection sheet constituting the solar cell element 3 and the encapsulant sheet, as shown in FIG. This sealing material sheet is required to have adhesion between these two members and adhesion durability that can withstand long-term use in harsh environments.

  Thus, in order to improve the adhesion of the polyethylene-based sealing material sheet to metal or glass, it is widely performed to contain a certain amount of silane-modified polyethylene in the base resin.

  On the other hand, in order to ensure sufficient adhesion between the polyethylene-based sealing material sheet constituting the sealing material-integrated back surface protection sheet and the polyester-based back surface protection sheet, the back surface protection of the sealing material sheet It is essential to perform corona treatment on the surface on the sheet side. However, when the silane-modified polyethylene is contained in each layer of the encapsulant sheet as described above, there is a problem that water is generated by corona treatment and the adhesion durability of the encapsulant sheet is lowered.

JP 2012-84842 A

  The present invention has been made in view of the above situation, and is a sealing material-integrated back surface protection sheet that can contribute to thinning and manufacturing cost reduction of a solar cell module, and when integrated as a solar cell module It is an object of the present invention to provide a sealing material-integrated back protective sheet that can contribute to improvement of long-term reliability of a solar cell module by exhibiting excellent adhesion durability.

  The inventors of the present invention have a three-layer structure of a first skin layer, a core layer, and a second skin as the sealing material layer constituting the sealing material-integrated back protective sheet, and the outermost surface layer on the sealing material layer side. The above-mentioned problem can be solved by adopting an inclined blending method in which the content of the silane-modified polyethylene gradually decreases from a certain first skin layer toward the second skin layer that is the outermost surface layer on the back protective sheet side. The present invention has been completed. More specifically, the present invention provides the following.

(1) A sealing material-integrated back surface protection sheet for a solar cell module, in which a sealing material layer having a polyethylene resin as a base resin and a back surface protection layer having a polyester resin as a base resin are laminated. The sealing material layer includes a core layer made of a sealing material composition for a core layer having a polyethylene resin as a base resin, and a density of 0.880 g / cm ³ or more and less than 0.910 g / cm ^3. A sealing material composition for a skin layer using a polyethylene resin having a lower density than that of the sealing material composition for the layer as a base resin. A multilayer structure comprising: a first skin layer disposed on a surface; and a second skin layer comprising a sealing material composition for the skin layer and disposed on an interface side with the back surface protective layer. And at least the co The layer and the first skin layer contain silane-modified polyethylene obtained by graft polymerization of an ethylenically unsaturated silane compound to low-density polyethylene, and the first skin layer has a content ratio of the silane-modified polyethylene that is higher than that of the core layer. Largely, the second skin layer does not contain the silane-modified polyethylene, or contains the silane-modified polyethylene in a smaller content ratio than the core layer.

  (2) The amount of polymerized silane in the sealing material composition of the first skin layer is 300 ppm or more and 2000 ppm or less, and the amount of polymerized silane in the sealing material composition of the core layer is 30 ppm or more and less than 300 ppm. The sealing material-integrated back protective sheet according to (1), wherein the amount of polymerized silane in the sealing material composition of the second skin layer is less than 40 ppm.

  (3) The sealing material-integrated back protective sheet according to (1) or (2), wherein the back protective layer includes a polyethylene terephthalate layer and / or a hydrolysis-resistant polyethylene terephthalate layer.

  (4) The sealing material-integrated back surface protective sheet according to any one of (1) to (3) is laminated in such a manner that the first skin layer faces the non-light-receiving surface side of the solar cell element. Solar cell module.

  According to the present invention, a sealing material-integrated back surface protection sheet that can contribute to thinning and manufacturing cost reduction of a solar cell module, and exhibiting excellent adhesion durability when integrated as a solar cell module It is possible to provide a sealing material-integrated back protective sheet that can contribute to the improvement of long-term reliability of a solar cell module.

It is sectional drawing which shows typically an example of the layer structure of the sealing material layer which comprises the sealing material integrated back surface protection sheet of this invention. It is sectional drawing which shows typically another example of the layer structure of the sealing material integrated back surface protection sheet of this invention. It is sectional drawing which shows typically the outline of the laminated constitution of the solar cell module which uses the sealing material integrated back surface protection sheet of this invention. It is sectional drawing which shows typically an example of the laminated constitution of the conventional general solar cell module.

  Hereinafter, the sealing material integrated back surface protection sheet of the present invention and the details of a solar cell module using the same will be described. The present invention is not limited to the embodiments described below.

<Encapsulant integrated back protection sheet>
As shown in FIGS. 1 and 2, the sealing material-integrated back protective sheet 10 for the solar cell module of the present invention mainly has a function of protecting the solar cell element from an impact from the outside of the solar cell module. 1 and a back surface protective layer 2 having a barrier property that prevents moisture and the like from entering mainly from the outside of the solar cell module. Each of the sealing material layer 1 and the back surface protective layer is composed of various resin sheets or the like, but is usually composed of different material resins because different functions are required. The resin layers made of these different resins are usually laminated and integrated by a dry laminating method using an adhesive.

  And the sealing material integrated back surface protection sheet 10 integrated beforehand prior to the integration process as a solar cell module is a non-light-receiving surface of the solar cell element 3 in the solar cell module 100 as shown in FIG. It is laminated on the side to constitute a solar cell module. Moreover, the sealing material integrated back surface protection sheet 10 is disposed in the solar cell module 100 in such a manner that the sealing material layer 1 faces the non-light-receiving surface side of the solar cell element 3.

  The total thickness including the sealing material layer 1 and the back surface protection layer 2, which will be described in detail below, is preferably 250 μm or more and 500 μm or less.

[Encapsulant layer]
As shown in FIG. 1, the sealing material layer 1 which comprises the sealing material integrated back surface protection sheet 10 is the multilayer which comprises the core layer 11 and both skin layers 12 and 13 arrange | positioned on both surfaces of the core layer 11. As shown in FIG. It has a structure.

  As shown in FIG. 2, the first skin layer 12 and the second skin layer 13 (hereinafter collectively referred to as “both skin layers”) are on the side of the encapsulant layer 1 in the encapsulant-integrated back protective sheet 10. It is arranged on the outermost surface. On the other hand, the second skin layer 13 is disposed on the interface side between the back surface protective layer 2 and the sealing material layer 1 in the sealing material integrated back surface protective sheet 10.

  By forming the encapsulant layer 1 of the encapsulant-integrated back protective sheet 10 using a resin composition optimized for each layer described below, the encapsulant layer 1 is required for the encapsulant layer of the solar cell module. While maintaining general required physical properties such as heat resistance and flexibility, it exhibits excellent adhesion durability between each layer when integrated as a solar cell module, contributing to improvement of long-term reliability of the solar cell module be able to.

The core layer of the encapsulant layer 1 and the skin layers 12 and 13 are each formed of an encapsulant composition having polyethylene as a base resin in a predetermined density range. The core layer 11 has a density 0.890 g / cm ³ or more 0.930 g / cm ³ or less, more preferably, a density 0.900 g / cm ³ or more 0.920 g / cm ³ encapsulant composition for following core layer Formed by. Further, both skin layers 12 and 13 are both less than the density 0.880 g / cm ³ or more 0.910 g / cm ^3, more preferably, a density 0.890 g / cm ³ or more 0.900 g / cm ³ or less In addition, it is formed of a sealing material composition for skin layers, which uses a polyethylene resin having a lower density than the sealing material composition for core layers as a base resin. Thus, by adjusting the density of each layer to the above range, a multilayer sealing material layer having both heat resistance and flexibility in a balanced manner can be obtained.

  The sealing material layer 1 contains at least the core layer 11 and the first skin layer 12 with silane-modified polyethylene obtained by graft polymerization of an ethylenically unsaturated silane compound onto low-density polyethylene. And in the sealing material layer 1, content of the silane modified polyethylene for every layer is optimized to the characteristic inclination distribution ratio demonstrated below. Specifically, the content ratio of the silane-modified polyethylene is larger in the first skin layer 12 than in the core layer 11, and the second skin layer does not contain the silane-modified polyethylene, or the silane-modified polyethylene is not contained in the core layer 11. The content ratio is smaller than the content ratio. That is, in the sealing material layer 1, a gradient distribution of the content of the silane-modified polyethylene is formed so that the content of the silane-modified polyethylene gradually decreases from the first skin layer 12 side to the second skin layer 13 side. Has been.

  Here, in the multilayer resin sheet, in particular, when a layer requiring adhesion enhancement is specified in one surface layer, conventionally, by distributing the silane-modified polyethylene only in the one surface layer, It was implemented as a general prescription. However, in the multilayer sheet having a three-layer structure of skin-core-skin, when the layer structure contains a large amount of silane-modified polyethylene only in one skin layer, the difference in layer strength between the layers increases, The present inventors have clarified that cohesive failure tends to occur inside the layer on the side where the layer strength is weak. This is presumably because a layer having a weak layer strength is strongly pulled by a strong layer, so that cohesive failure easily occurs inside the weak layer.

  Therefore, in the sealing material layer 1 of the sealing material-integrated back protective sheet 10, the core layer 11 also contains less silane-modified polyethylene than the first skin layer 12 and more than the second skin layer 13. In this way, the above inclination distribution is formed. Thereby, in the sealing material layer 1, even when a large amount of silane-modified polyethylene is required to be added to the first skin layer 12, the layer strength between the layers as described above can be avoided by avoiding the extreme uneven distribution of the silane-modified polyethylene. The expansion of the difference can be suppressed, the occurrence of the above cohesive failure can be avoided, and the durability of the sealing material-integrated back protective sheet 10 can be enhanced.

  In the sealing material layer 1, the first skin layer 12, which is required to have adhesiveness and adhesion durability with the solar cell element 3, contains a relatively large amount of silane-modified polyethylene to face the first skin layer 12. It is possible to improve adhesion and adhesion durability with respect to a member to a very preferable level.

  In addition, the second skin layer 13 that is in contact with the interface on the back surface protective layer side where corona treatment is usually required does not contain silane-modified polyethylene or contains only a very small amount of silane-modified polyethylene. Generation | occurrence | production of the water which arises by the influence of the corona treatment in an interface can be prevented, and the fall of adhesion durability with the 2nd skin layer 13 and the back surface protective layer 2 in the said interface can be avoided. In the sealing material-integrated back protective sheet 10, corona treatment is applied to at least one of the second skin layer 13 that forms the interface or the surface of the back protective layer 2 that faces the second skin layer 13. The corona treatment is a method of improving the adhesion performance by introducing a polar group to the surface of the resin substrate by irradiating the resin substrate with corona discharge.

  About content of the ethylenically unsaturated silane compound in each layer of the sealing material layer 1, it is as follows. The amount of polymerized silane in the encapsulant composition of the first skin layer 12 is 300 ppm to 2000 ppm, the amount of polymerized silane in the encapsulant composition of the core layer 11 is 30 ppm to less than 300 ppm, and the second skin layer The amount of polymerized silane in 13 sealing material compositions is preferably less than 40 ppm.

  In addition, it is preferable that the sealing material composition which forms the core layer 11 and both skin layers 12 and 13 of the sealing material layer 1 uses polyethylene in a predetermined | prescribed melting | fusing point range as a base resin, respectively. The encapsulant composition for the core layer preferably uses a low density polyethylene having a melting point of 100 ° C. or higher and 115 ° C. or lower as a base resin. On the other hand, it is preferable that the sealing material composition for both skin layers uses low density polyethylene having a melting point of 80 ° C. or higher and lower than 100 ° C. as a base resin. Further, the resin composition is adjusted so that the difference in melting point of the base resin of the encapsulant composition forming the core layer 11 and the skin layers 12 and 13 is within a range of 20 ° C. or less within the melting point range. More preferably. Thus, by adjusting the melting point range of each layer to the above range, wrinkles caused by the difference in shrinkage stress between the layers of the encapsulant layer 1 during the heat processing of the encapsulant-integrated back surface protection sheet 10 are caused. Generation | occurrence | production can be reduced and it can contribute to the improvement of productivity and quality stability of the solar cell module 100. FIG.

  In this specification, the melting point of the resin constituting each layer of the encapsulant layer refers to the melting point of the resin that can be obtained by differential scanning calorimetry (DSC). When there are a plurality of valley peaks in the DSC curve, the melting point indicated by the peak with the largest peak area is referred to as the melting point of the resin.

  The thickness of the sealing material layer 1 is preferably 200 μm or more and 400 μm or less, and more preferably 250 μm or more and 350 μm or less. If the thickness is 200 μm or more, various required physical properties other than the above heat resistance can be sufficiently maintained. In the case where the skin layers 12 and 13 are laminated on both surfaces of the core layer 11 to form the three-layer structure sealing material layer 1, the thickness ratio thereof is the skin: core: skin thickness ratio. In the range of 1: 3: 1 to 1: 30: 1.

[Skin layer]
Both skin layers 12 and 13 are layers arranged in both outermost layers of the sealing material layer 1. In the solar cell module 100, the first skin layer 12 serves as a close contact surface between the non-light-receiving surface side of the solar cell element 3 and the light-receiving surface side sealing material sheet 4, and the second skin layer 13 is the same as the sealing material. It becomes an adhesion surface with the back surface protective layer 2 when forming the body shape back surface protective sheet 10. Both skin layers 12 and 13 have the adhesiveness of the sealing material layer 1 and the ability to follow irregularities of other members during lamination for integration as a solar cell module (hereinafter referred to as “molding characteristics”). Contributes to improvement.

  The thicknesses of the skin layers 12 and 13 may be appropriately determined in consideration of the thickness (thinness) required for the sealing material layer 1. As an example, in the case of a layer configuration in which both skin layers 12 and 13 are laminated on one surface of the core layer 11, the preferred thickness of both skin layers 12 and 13 is 3 μm or more and 150 μm or less. When the thickness of both skin layers 12 and 13 is 3 μm or more, sufficient adhesion and molding characteristics can be imparted to the sealing material layer 1.

(Encapsulant composition for skin layer)
The sealing material composition for the skin layer that forms the first skin layer 12 and the second skin layer 13 uses low density polyethylene having a density of 0.880 g / cm ³ or more and less than 0.910 g / cm ³ as a base resin. The content ratio in the total resin component of the sealing material composition for skin layers of this low density polyethylene resin may be 80% by mass or more and 100% by mass or less, and preferably 98% by mass or more and 100% by mass or less. is there. And the melting point of this base resin is made into the above-mentioned range.

  Unlike the sealing material composition for the core layer, the sealing material composition for the skin layer does not substantially contain polypropylene. The first skin layer 12 and the second skin layer 13 are layers mainly composed of low-density polyethylene having a lower density than the base resin of the core layer sealing material composition, and mainly the sealing material layer. 1 is a layer that functions as a layer that imparts molding characteristics and adhesion to 1. In the present invention, “substantially does not contain polypropylene” means that, for example, the resin-derived polypropylene added to the core layer is impregnated in a trace amount in the skin layer, and this is detected even if this is detected. This means that “polypropylene is not substantially contained” is considered. The above trace amount is, for example, a content ratio in the skin layer, and is less than 0.1% by mass.

  Of the encapsulant composition for skin layer, at least the encapsulant composition for first skin layer preferably contains silane-modified polyethylene in a predetermined ratio. Silane-modified polyethylene is obtained by graft-polymerizing linear low-density polyethylene (LLDPE) or the like as a main chain with an ethylenically unsaturated silane compound as a side chain. Such a graft copolymer can further improve the adhesion of the encapsulant layer 1 because the degree of freedom of silanol groups contributing to the adhesive force is increased.

  The amount of ethylenically unsaturated silane compound in the sealing material composition for the first skin layer is such that the amount of polymerized silane in the sealing material composition of the first skin layer is 300 ppm to 2000 ppm, preferably 300 ppm to 1500 ppm. Hereinafter, more preferably, it may be appropriately adjusted so as to be 300 ppm or more and 1000 ppm or less. When the amount of the ethylenically unsaturated silane compound is large, the mechanical strength and heat resistance are excellent. For example, when the amount of the ethylenically unsaturated silane compound exceeds 2000 ppm, the content becomes excessive, and the tensile strength is increased. It tends to be inferior in elongation and heat-fusibility. In addition, the amount of polymerized silane in each layer of the sealing material can specify the abundance in the resin component by quantifying the elements in each layer by, for example, ICP emission analysis.

  The amount of the ethylenically unsaturated silane compound in the encapsulant composition for the second skin layer is preferably less than 40 ppm on the assumption that it is within the range capable of forming the above-described gradient distribution, More preferably, it is 0 ppm.

  Silane-modified polyethylene 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, durability, etc. It has excellent weather resistance, heat resistance, water resistance, light resistance, wind pressure resistance, yield resistance, and other characteristics, and is also affected by manufacturing conditions such as thermocompression bonding for manufacturing solar cell modules. It is possible to manufacture solar cell modules that are extremely excellent in heat fusion, 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.

[Core layer]
The core layer 11 mainly has a function of imparting heat resistance and appropriate rigidity to the sealing material layer 1. The core layer 11 is made of a sealing material composition for a core layer using low density polyethylene as a base resin. As described above, the core layer 11 is also sealed for the core layer so that the silane-modified polyethylene is contained in the core layer 11 less than the first skin layer 12 and more than the second skin layer 13. An appropriate amount of silane-modified polyethylene is added to the material composition. And the sealing material composition for core layers may mix a polypropylene within the range of predetermined content ratio further.

  An example of the thickness of the core layer 11 is 100 μm or more and 240 μm or less, and is not particularly limited. When the thickness of the core layer 11 is 100 μm or more, good dimensional stability can be imparted to the sealing material layer 1. Moreover, when the thickness of the core layer 11 is 240 μm or less, the encapsulating material layer 1 can be provided with sheet transportability at the time of lamination.

(Encapsulant composition for core layer)
Encapsulant composition for the core layer to form a core layer 11, the density of 0.910 g / cm ³ or more 0.950 g / cm ³ or less of low density polyethylene resin and the base resin. The content ratio in the total resin component of the sealing material composition for the core layer of the low density polyethylene resin may be 60% by mass or more and 95% by mass or less, and preferably 75% by mass or more and 85% by mass or less. It is. And it is preferable to make melting | fusing point of this base resin into the above-mentioned range. In addition, content ratio of each resin in the resin composition used for this invention can be analyzed from the peak ratio etc. which are detected by DSC (differential scanning calorimetry) or IR (infrared spectroscopy) etc., for example.

  The encapsulant composition for the core layer preferably contains 5% by mass or more and 40% by mass or less of polypropylene in the content ratio in all resin components. By adding an appropriate amount of polypropylene to the core layer 11 having low-density polyethylene as a base resin, the function can be further improved as a layer imparting heat resistance and dimensional stability.

  It is more preferable to use a homopolypropylene (homo PP) resin as the polypropylene contained in the above-mentioned predetermined amount range in the encapsulant composition for the core layer. 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 encapsulant composition for the core layer, the dimensional stability of the encapsulant layer 1 can be further enhanced. Moreover, it is preferable that MFR in 230 degreeC of homo PP is 5 g / 10min or more and 125 g / 10min or less. When the MFR is less than 5 g / 10 min, the molecular weight becomes large and the rigidity becomes too high, and the preferable and sufficient flexibility of the sealing material layer 1 cannot be secured even by the physical properties of the skin layers 12 and 13. If the MFR exceeds 125 g / 10 min, the fluidity during heating is not sufficiently suppressed, and the sealing material layer 1 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 the low-density polyethylene used as the base resin in any of the above structures. Therefore, for example, when polypropylene exceeding 40% by mass is added to the sealing material composition for the core layer exceeding the appropriate addition amount range, the physical properties of polypropylene in the core layer 11 become excessively superior. The preferable flexibility of the sealing material layer 1 as a whole cannot be ensured by the physical properties of both skin layers 12 and 13. Therefore, it is preferable to add polypropylene in a limited amount within the above range even in the sealing material composition for the core layer.

  By mixing polypropylene in the above content range, the sealing material layer 1 can be provided with good heat resistance even when the sealing material sheet is a thin sheet having a thickness of 400 μm or less.

(Other ingredients)
The sealing material composition for the skin layer and the sealing material composition for the core layer can further contain other components. For example, components such as various weather resistance master batches, various fillers, light stabilizers, ultraviolet absorbers, and heat stabilizers for imparting weather resistance to the encapsulant layer 1 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 sealing material composition. By containing these additives, the sealing material layer 1 can be provided with a long-term improvement in mechanical strength, an effect of preventing yellowing, cracking, and the like.

[Back side protective layer]
The back surface protective layer 2 constituting the sealing material integrated back surface protective sheet 10 can be formed as a single resin layer made of a resin having a barrier property. Alternatively, the back surface protective layer 2 constituting the sealing material-integrated back surface protective sheet 10 is also formed as a layer having a multilayer structure having a barrier property, in which a single resin layer and other layers are laminated. You can also.

  As the material resin for forming the back surface protective layer 2, various resins that have been conventionally used as back surface protective sheets for solar cell modules can be used. As the resin sheet for forming the back surface protective layer 2, for example, a polycarbonate resin, a polyester resin such as polyethylene terephthalate (PET), or polyethylene naphthalate 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. The polyethylene terephthalate (PET) has a melting point of about 260 ° C, and other polyester resins have a melting point of about 220 ° C to 280 ° C. Any of these resins has a melting point sufficiently higher than that of the olefin resin forming the sealing material layer 1 and is a high melting point resin that does not melt depending on the heating temperature (150 ° C. or lower) at the time of manufacturing a general solar cell module.

  Regarding the layer structure in the case where the back surface protective layer 2 has a multilayer structure, an inner layer layer facing the sealing material layer is formed of PET from the viewpoint of improving mechanical strength and water vapor barrier properties and considering economy. The outer layer 22 exposed on the outermost layer side is formed of hydrolysis-resistant polyethylene terephthalate (hydrolysis-resistant PET), and these layers are integrated with each other through an adhesive layer. Specific examples can be given.

  Although the thickness of the back surface protective layer 2 is not particularly limited, it is required for the sealing material-integrated back surface protective sheet 10 as long as physical properties such as water vapor barrier properties required for the back surface protective layer 2 can be maintained. What is necessary is just to determine suitably considering thickness. The thickness of the back surface protective layer 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 protective layer 2 is 25 μm or more, preferable durability and weather resistance can be imparted to the sealing material integrated back surface protective sheet 10.

  Further, as described above, the surface of the back surface protective layer 2 on the interface side with the sealing material layer may be subjected to corona treatment as a surface treatment for improving adhesion.

[Method of manufacturing sealing material-integrated back surface protection sheet]
The manufacturing method of the sealing material integrated back surface protection sheet of this invention is demonstrated. The sealing material integrated back surface protection sheet 10 includes a “back surface protection sheet forming step” for forming a back surface protection sheet for forming the back surface protection layer 2 and a “sealing material sheet for forming the sealing material layer 1”. It can be manufactured by going through the “stop material sheet forming step” and the “integration step” in which the sealing material sheet is laminated and integrated on the back surface protective layer sheet.

(Back surface protection sheet forming process)
The back surface protective layer sheet 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, or other film forming methods. Can do. In addition, the back surface protective layer 2 may be made of a sheet containing other additives such as a pigment in addition to the resin material as long as the effects of the present invention are not impaired.

(Encapsulant sheet forming process)
The encapsulant layer sheet is formed by integrally forming the above-described encapsulant composition for the skin layer and the encapsulant composition for the core layer into a multilayer sheet by a known co-extrusion method. Can do.

(Integration process)
The sealing material sheet constituting the sealing material layer 1, the back surface protection sheet constituting the back surface protection layer 2, and a sheet for forming other layers formed by the same method as necessary are appropriately laminated. Further, by further integrating, the sealing material-integrated back protective sheet 10 of the present invention can be obtained. The integration of the sheets can be performed by a conventionally known dry laminating method. Conventionally known laminating adhesives can be used and are not particularly limited. A two-component curable dry laminating adhesive composed of a main agent such as urethane or epoxy and a curing agent can be used as appropriate. In addition, this integration process can also be based on the extrusion coat lamination method and the sandwich lamination method which is the application form.

<Solar cell module>
A basic configuration of the solar cell module 100 using the sealing material-integrated back protective sheet 10 of the present invention will be described with reference to FIG. The solar cell module 100 includes, from the non-light-receiving surface side, a sealing material-integrated back surface protection sheet 10, a solar cell element 3, a light-receiving surface-side sealing material sheet 4, and a transparent front substrate 5 disposed on the outermost layer on the light-receiving surface side. Are stacked in order. The sealing material-integrated back surface protection sheet 10 is arranged in such a manner that the sealing material layer 1 faces the non-light-receiving surface side of the solar cell element 3.

  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 other various types of conventionally known solar cell elements can be used. .

  As described above, the light-receiving surface side sealing material sheet 4 that covers the light-receiving surface side surface of the solar cell element 3 is a resin sheet that mainly exhibits a function of protecting the solar cell element 3 from external impact. Moreover, the light-receiving surface side sealing material sheet 4 is required to be a transparent sheet in order to transmit sunlight with high transmittance. As a resin base material for forming the light-receiving surface side sealing material sheet 4, thermoplastic resins such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), polyethylene-based resin such as polyethylene, and the like. It can be used as appropriate.

  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. .

[Method for manufacturing solar cell module]
The solar cell module 100 is, for example, vacuum-sucked after sequentially laminating the members including the transparent front substrate 5, the light-receiving surface side sealing material sheet 4, the solar cell element 3, and the sealing material-integrated back surface protection sheet 10. 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. Thus, the solar cell module 100 can be manufactured by thermocompression-bonding each of the above layers as an integrally molded body.

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

<Manufacture of sealing material sheet>
The sealing material which comprises the sealing material layer of the sealing material integrated back surface protection sheet of an Example and a comparative example by the manufacturing method as described in the column of the said (sealing material sheet formation process) using the following material Created a sheet.

  What mixed the following material by the composition (mass part) of Table 1 was used properly as the sealing material composition of the core layer of the sealing material sheet of an Example and a comparative example, and a skin layer, respectively. Then, these sealing material compositions were 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, A core / skin three-layer encapsulant sheet was obtained. 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.
Linear low-density polyethylene 1 (LLDPE, indicated as “PE1” in the table): density 0.898 g / cm ³ , melting point 90 ° C.
Low density polyethylene 2 (denoted as “PE2” in the table): density 0.919 g / cm ³ , melting point 105 ° C.
Silane-modified polyethylene (denoted as “PESi” in the table): 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) with a density of 0.900 g / cm ³ and MFR of 1.1 g / 10 min. 2 parts by mass of methoxysilane and 0.1 parts by mass of dicumyl peroxide as a radical generator (reaction catalyst) are mixed, melted and kneaded at 200 ° C., and silane-modified polyethylene having a density of 0.900 g / cm ^3. Got.
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.).
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.

  The graft amount (parts by mass) of the ethylenically unsaturated silane compound with respect to 100 parts by mass of the polyethylene-based resin in each layer of the sealing material sheets of the above Examples and Comparative Examples is shown in Table 2 as “Si graft amount”. It was.

<Manufacture of sealing material integrated back surface protection sheet>
The sealing material sheet of each of the above examples and comparative examples and a PET film (Teijin DuPont, “Melinex S”, thickness 125 μm) subjected to corona treatment on the surface are laminated by a conventionally known dry laminating method. And the sealing material integrated back surface protection sheet of each Example and the comparative example was obtained. However, in Comparative Example 5, the PET film was laminated without performing corona treatment.

<Evaluation Example 1: Metal adhesion evaluation of first skin layer>
[Metal adhesion test]
The sealing material layers of the sealing material-integrated back surface protection sheets of Examples and Comparative Examples cut to a width of 15 mm were adhered to copper foils (75 mm × 50 mm × 0.035 mm), respectively, and the following vacuum heating lamination conditions ( A vacuum heating laminator treatment was performed under the same conditions as in a) to (d), and samples for metal adhesion evaluation were obtained for each of the examples and comparative examples. For each of these metal adhesion evaluation samples, the adhesion strength under the following test conditions was measured to evaluate the metal adhesion.
In the above-mentioned sample for metal adhesion evaluation, the sealing material sheet adhered on the copper foil was vertically peeled (50 mm / min) with a peel tester (Tensilon Universal Tester RTF-1150-H). The test was conducted and the measurement results were evaluated according to the following evaluation criteria A to C.
(Vacuum heating lamination conditions) (a) Vacuum drawing: 6.0 minutes
(B) Pressurization (0 kPa to 70 kPa): 1.5 minutes
(C) Pressure holding (70 kPa): 10.0 minutes
(D) Temperature 165 ° C
(Evaluation criteria) A: 15.0N / 15mm or more
B: 10.0N / 15mm or more and less than 15.0N / 15mm
C: Less than 10.0N / 15mm

<Evaluation Example 2: Adhesive evaluation of second skin layer>
Dry lamination with an acrylic adhesive with the second skin layer of the sealing material sheets of Examples and Comparative Examples cut to a width of 15 mm facing the PET film (75 mm × 50 mm × 0.035 mm) for the back surface protective layer. Attempted to adhere. Only Comparative Example 6 in which the corona treatment was not performed was impossible to bond at a level that could withstand practical use.

<Evaluation Example 3: Evaluation of durability of sealing material layer>
[Durability test]
In order to evaluate the light resistance of the encapsulant sheet of the present invention, each sample of the encapsulant-integrated back protective sheet used in Evaluation Example 1 conforms to JIS C8917, and has a test chamber temperature of 85 ° C. and a humidity of 85%. The “dump heat test” was performed under the above conditions, and the durability was evaluated based on the time until peeling visually observable between the sealing material layer and the back surface protective layer. The results are shown in Table 2 as “durability”. The evaluation criteria were as follows.
(Evaluation criteria) A: No peeling occurred after 2000 hours
B: Time until occurrence of peeling is 1000 hours or more and less than 2000 hours
C: Time until occurrence of the peeling is less than 1000 hours

  From Tables 1 and 2, the sealing material integrated back surface protection sheet of the present invention is a sealing material integrated back surface protection sheet that can contribute to the reduction in thickness and manufacturing cost of the solar cell module. It can be seen that it is a sealing material-integrated back protective sheet that can contribute to improvement of long-term reliability of the solar cell module by exhibiting excellent adhesion durability at the time of integration.

DESCRIPTION OF SYMBOLS 1 Sealing material layer 11 Core layer 12 1st skin layer 13 2nd skin layer 2, 7 Back surface protective layer 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 back surface protection sheet 100 Solar cell module

Claims (4)

A sealing material-integrated back surface protection sheet for a solar cell module, in which a sealing material layer based on a polyethylene resin and a back surface protection layer based on a polyester resin are laminated,
The sealing material layer includes a core layer made of a sealing material composition for a core layer having a polyethylene resin as a base resin;
It consists of the sealing material composition for skin layers whose density is lower than that of the sealing material composition for the core layer, and is arranged on the outermost surface on the sealing material layer side in the sealing material-integrated back protective sheet. A first skin layer;
A second skin layer comprising a sealing material composition for the skin layer and disposed on an interface side with the back surface protective layer; and a multilayer structure comprising:
At least the core layer and the first skin layer contain silane-modified polyethylene obtained by graft polymerization of an ethylenically unsaturated silane compound to low-density polyethylene,
The first skin layer has a larger content ratio of the silane-modified polyethylene than the core layer,
The second skin layer does not contain the silane-modified polyethylene, or contains the silane-modified polyethylene in a smaller content ratio than the core layer. The amount of polymerized silane in the sealing material composition of the first skin layer is 300 ppm or more and 2000 ppm or less, the amount of polymerized silane in the sealing material composition of the core layer 11 is 40 ppm or more and less than 300 ppm, The encapsulant-integrated back protective sheet according to claim 1, wherein the amount of polymerized silane in the encapsulant composition of the skin layer 13 is less than 40 ppm.   The encapsulant-integrated back protective sheet according to claim 1 or 2, wherein the back protective layer includes a polyethylene terephthalate layer and / or a hydrolysis-resistant polyethylene terephthalate layer.   The solar cell module by which the sealing material integrated back surface protection sheet in any one of Claim 1 to 3 is laminated | stacked in the aspect which the said 1st skin layer faces the non-light-receiving surface side of a solar cell element.

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