JP6035818B2 - Back surface protection sheet for solar cell module and solar cell module - Google Patents

Description

  The present invention relates to a back surface protection sheet for a solar cell module. More specifically, the back surface protective sheet that has excellent adhesion to the solar cell module sealing material and also has excellent handling properties due to curling deformation being suppressed, and the sun using the back surface protective sheet The present invention relates to a battery module.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. In general, a solar cell module constituting a solar cell has a configuration in which a transparent front substrate, a front sealing material, a solar cell element, a back sealing material, and a back surface protection sheet are laminated in order from the light receiving surface side. It has a function of generating electricity by being incident on the solar cell element.

  The back surface protection sheet for a solar cell module is required to play a role of preventing moisture (water vapor) from entering the back surface sealing material as a member constituting the solar cell module. As such a back surface protection sheet for a solar cell module, for example, a polyethylene-based or fluorine-based resin film is used. Among them, a back surface protection sheet using a polyethylene terephthalate (PET) film is particularly widely used because it is inexpensive and excellent in processability and does not emit toxic gas when burned.

  Moreover, as a sealing material for solar cell modules, polyethylene-based resins such as ethylene-vinyl acetate copolymer resin (EVA) or linear low density polyethylene (LLDPE) are used. The back surface protection sheet for a solar cell module is required to have high adhesion between these sealing materials.

  As a back surface protection sheet with improved adhesion to the sealing material, a layer for improving the adhesion between the sealing material (hereinafter referred to as “adhesion”) on a base material layer made of PET or the like that is inexpensive and excellent in workability. Also referred to as a “strengthening layer”), as a backside protective sheet bonded with a heat-fusible resin layer having excellent adhesion to an ethylene polymer (see Patent Document 1), excellent in hydrolysis resistance, and heat fusion The back surface protection sheet (refer patent document 2, 3) which has arrange | positioned the polypropylene resin which shows adhesiveness in the outermost layer is disclosed.

Japanese Patent Laid-Open No. 10-25357 JP 2007-150084 A JP 2007-19059 A

  In the back surface protection sheet provided with the adhesion reinforcing layer in addition to the base material layer, as in the back surface protection sheets described in Patent Documents 1 to 3, due to the difference in shrinkage between each layer, for example, in the work process When it is in a single wafer state, the back surface protection sheet is curled and the handling property is impaired.

  When the adhesion reinforcing layer is made of a polypropylene resin having a relatively high melting point, as in the back surface protective sheet described in Patent Documents 2 and 3, while suppressing curl deformation of the back surface protective sheet to some extent, The adhesion can be improved to a certain extent. However, in general, there is a trade-off relationship between curling deformation suppression and sealing material improvement in the backside protection sheet, so that both the adhesion and handling properties are compatible at a sufficiently high level. There is no sheet yet, and there has been a strong demand for a more preferable back surface protection sheet having such high adhesion and handling properties.

  The present invention has been made in view of the above situation, and is a back surface protection sheet for a solar cell module that has high adhesion with a sealing material and can withstand use in a harsh environment for a long time. And it aims at providing the back surface protection sheet for solar cell modules which is provided with high handling property by curl deformation being fully controlled, and can contribute greatly to the productivity improvement of a solar cell module.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have adopted a predetermined amount of inorganic filler for the adhesion reinforcing layer formed on the base material layer of the back surface protective sheet in the back surface protective sheet for solar cell modules. Adhesive sufficiently high between the back protective sheet and the sealing material by having a multilayer structure including a polypropylene resin core layer and a polypropylene resin skin layer containing a predetermined amount of ethylene unit And the present invention has been completed. More specifically, the present invention provides the following.

  (1) A back surface protection sheet for a solar cell module, comprising a base material layer made of a resin film and an adhesion reinforcing layer made of a polypropylene resin and disposed on the outermost layer of the back surface protection sheet. The adhesion reinforcing layer has a multilayer structure including a core layer and a skin layer exposed to the outermost layer, and the core layer contains 3% by mass to 30% by mass of an inorganic filler. The back surface protection sheet for solar cell modules which consists of a polypropylene resin, and the said skin layer is a polypropylene resin which contains ethylene unit 2.3 mass% or more and 5.0 mass% or less.

  (2) The said core layer is a back surface protection sheet for solar cell modules as described in (1) which contains 5 mass% or more and 20 mass% or less of talc as said inorganic filler.

  (3) The back surface protection sheet for solar cell modules as described in (1) or (2) whose said base material layer is a polyethylene terephthalate resin.

  (4) The back surface protective sheet for a solar cell module according to any one of (1) to (3), wherein the adhesion reinforcing layer is a three-layer coextruded layer of skin layer / core layer / skin layer.

  (5) The back surface protective sheet for solar cell modules according to any one of (1) to (4), comprising the transparent front substrate, the sealing material, the solar electronic element, and the adhesion reinforcing layer of the back surface protective sheet. A solar cell module in which the sealing material is laminated.

  (6) The solar cell module according to (5), wherein the sealing material is a polyethylene resin or an ethylene-vinyl acetate copolymer resin.

  According to the present invention, the adhesion reinforcing layer formed on the base material layer of the back surface protective sheet for solar cell modules is formed of polypropylene resins having different compositions and physical properties, thereby providing a space between the back surface protective sheet and the sealing material. Can provide a solar cell module back surface protection sheet having high adhesion and excellent handling properties, and furthermore, by using it, it is possible to efficiently produce a solar cell module excellent in weather resistance. it can.

It is a schematic diagram of the cross section which shows an example of the laminated constitution of the solar cell module of this invention. It is a schematic diagram of the cross section which shows an example of the layer structure of the back surface protection sheet for solar cell modules of this invention. It is the partial expanded schematic diagram of the cross section which shows an example of the laminated constitution of the adhesion reinforcement layer of the back surface protection sheet for solar cell modules of this invention. It is the partial expansion schematic diagram of the cross section which shows another example of the layer structure of the adhesion reinforcement layer of the back surface protection sheet for solar cell modules of this invention.

  Hereinafter, the back surface protection sheet for solar cell modules of the present invention (hereinafter also simply referred to as “back surface protection sheet”) and the details of the 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 structure of the solar cell module using the back surface protection sheet for solar cell modules of this invention is demonstrated using FIG. As shown in FIG. 1, the solar cell module 1 includes a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and the back protection sheet of the present invention from the light receiving surface side. 6 is laminated in order.

  The transparent front substrate 2 is generally a glass substrate. The transparent front substrate 2 may also be another member as long as it maintains the weather resistance, impact resistance, and durability of the solar cell module 1 and transmits sunlight with high transmittance. .

  The sealing material layer composed of the front sealing material layer 3 and the back sealing material layer 5 is disposed in the solar cell module 1 in order to fix the position of the solar cell element 4 and alleviate external impact. It is a layer made of a resin base material. As the resin substrate for forming the sealing material layer, polyethylene-based resins such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), and polyethylene can be used. Conventionally, EVA, which has a certain durability and the like, has excellent workability, and is available at a relatively low price, has been widely used. In recent years, however, the problem of reduced steam barrier properties, which is a drawback of EVA, has been solved. For this reason, polyethylene-based resins such as resins obtained by subjecting low-density polyethylene to cross-linking treatment are often used.

  In addition, the back surface protection sheet 6 of this invention is especially excellent in adhesiveness between resin which performed the crosslinking process. Of the above material resins, EVA is generally required to be subjected to a crosslinking treatment when modularized. As the polyethylene-based resin, a low-density polyethylene resin of a type in which an appropriate amount of a crosslinking agent is added and thermally crosslinked at the time of modularization can be preferably used.

  In addition, it is preferable that MFR after the crosslinking process of such a sealing material sheet | seat which consists of a low density polyethylene resin etc. is 0.08 g / 10min or more and less than 1.0 g / 10min. By making MFR into such a range, a sealing material sheet can be provided with preferable heat resistance. In the case where the solar cell module 1 is configured using such a polyethylene resin sealing material and the back surface protective sheet 6 of the present invention, the sealing material is configured from the viewpoint of the balance between heat resistance and adhesion. MFR (MFR at 190 ° C. and load 2.16 kg measured according to JIS-K6922-2 after the crosslinking treatment of the low density polyethylene resin to be performed. In the present specification, the measurement value under these measurement conditions is hereinafter referred to as MFR. ) Is preferably 0.08 g / 10 min or more and less than 1.0 g / 10 min. The gel fraction is preferably 0% or more and 80% or less, and more preferably 0% or more and 20% or less.

  As the solar cell element 4, conventionally known solar cell elements can be widely used. FIG. 1 shows a case where the solar cell element 4 is a crystalline silicon solar cell manufactured using a single crystal silicon substrate or a polycrystalline silicon substrate. In addition, amorphous silicon or microcrystalline silicon is used as a transparent front substrate. 2 may be a thin film solar cell element formed by forming an extremely thin silicon film of about 1 μm or less on 2. The back surface protective sheet 6 of the present invention can also be preferably used for a solar cell module on which a thin film solar cell element is mounted.

  Since the back surface protective sheet 6 is disposed in the outermost layer of the solar cell module 1, it has high weather resistance and high adhesion with the back sealing material layer 5 described above. Is required. The back surface protection sheet 6 has sufficiently enhanced handling properties that can contribute to the improvement of productivity in the manufacturing stage of the solar module while satisfying the requirements in terms of physical properties when used as a solar cell module. is there. Details of the back surface protection sheet 6 according to the present invention will be described later.

<Back protection sheet>
As shown in FIG. 2, the back surface protection sheet 6 is a multilayer structure including at least a base material layer 61 and an adhesion reinforcing layer 62. Further, a layer provided with a weathering layer 63 can also be preferably used, but the weathering layer 63 is not essential in the present invention.

  The adhesion reinforcing layer 62 is disposed on one surface of the base material layer 61, and the weather resistant layer 63 is disposed on the other surface of the base material layer 61 as necessary. It is integrated with the base material layer 61 through a layer (not shown). In the solar cell module 1, the back surface protective sheet 6 is arranged so that the adhesion reinforcing layer 62 and the back surface sealing agent layer 5 are in close contact with each other.

[Base material layer]
The base material layer 61 is a layer arranged as a base material of the back surface protection sheet 6, and uses a resin sheet obtained by molding a resin material into a sheet shape. For example, polyethylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride resin, poly (meth) acrylic resin, polycarbonate resin, polyethylene Polyester resins such as terephthalate (PET) and polyethylene naphthalate, polyamide resins such as various nylons, polyimide resins, polyamideimide resins, polyarylphthalate resins, silicone resins, polysulfone resins, polyphenylene sulfide resins Various resin sheets such as polyethersulfone resin, polyurethane resin, acetal resin, and cellulose resin can be used. Among these, polyethylene terephthalate (PET) can be preferably used from the viewpoint of physical properties such as insulation performance, mechanical strength, cost, transparency, and economy, and hydrolysis resistant PET can be preferably used from the viewpoint of maintaining mechanical strength. .

  The thickness of the base material layer 61 is not particularly limited, but may be appropriately determined in consideration of the thickness required for the back surface protective sheet 6. As for the thickness of the back surface protection sheet 6, the range of 10-500 micrometers is mentioned as a general example. In accordance with this, the thickness of the base material layer 61 is preferably 38 to 250 μm. When the thickness of the base material layer 61 is 38 μm or more, preferable durability and weather resistance can be imparted to the back surface protective sheet 6, and when the thickness of the base material layer 61 is 250 μm or less, lamination processing is performed. It is possible to impart film transportability at the time.

  In a conventionally known general back surface protection sheet using PET as a base material layer, a PET resin film for forming the base material layer and other resin films for forming an adhesion layer are laminated and integrated with an adhesive or the like. At this time, there has been a problem that the back surface protection sheet frequently undergoes curl deformation. However, as will be described in detail later, in the back surface protection sheet 6 of the present invention, the back surface protection sheet 62 has a multi-layer structure having a configuration unique to the present invention, so that the back surface protection can be performed regardless of the type of the base material layer. Sheet curling can be sufficiently suppressed. For this reason, PET excellent in each of the above physical properties and economy can be preferably used as the resin constituting the base material layer.

[Adhesion strengthening layer]
The adhesion reinforcing layer 62 is a layer disposed on one outermost layer of the back surface protection sheet 6, and becomes a contact surface between the back surface sealing material layer 5 in the solar cell module 1, and the back surface protection sheet 6 and the back surface sealing layer. It is a layer having a function of improving the adhesion between the stopper layer 5. In general, the back sealing material layer 5 is made of an ethylene-vinyl acetate alcohol copolymer resin (EVA resin), a low-density polyethylene resin subjected to crosslinking treatment, or the like. The adhesion reinforcing layer 62 is provided with high adhesion between the back surface protective sheet 6 and the back surface sealing material layer 5 made of these resins.

  As shown in FIG. 3A, the adhesion reinforcing layer 62 is a layer composed of two or more layers including a core layer 621 and a skin layer 622 that is laminated on the surface of the core layer 621 and exposed to the outermost layer. The core layer 621 and the skin layer 622 constituting the adhesion reinforcing layer 62 are mainly composed of a polypropylene (PP) resin. Appropriate rigidity can be imparted to the back surface protective sheet 6, and therefore, curling deformation can be suppressed and handling properties can be improved.

  The thickness of the adhesion reinforcing layer 62 may be appropriately determined in consideration of the thickness required for the back surface protective sheet 6. As an example, the thickness of the adhesion reinforcing layer 62 is 10 to 200 μm, and is not particularly limited. When the thickness of the adhesion reinforcing layer 62 is 10 μm or more, sufficient adhesion between the back surface protective sheet 6 and the back sealing material layer 5 can be imparted, and the thickness of the adhesion reinforcing layer 62 is 200 μm. By being below, the film conveyance aptitude at the time of a lamination process can be provided.

  For example, as shown in FIG. 3B, the adhesion reinforcing layer may have a configuration such as an adhesion reinforcing layer 62A having a three-layer structure in which a skin layer 622a, a core layer 621, and a skin layer 621b are sequentially stacked. . Also by such a structure, it can be set as the back surface protection sheet 6 which fully improved adhesiveness and handling property with a sealing material. In addition, there is also a merit that the production efficiency can be improved by adopting such a symmetrical layer structure.

  The adhesion reinforcing layer 62 has a multilayer structure formed by laminating the core layer 621 and the skin layer 622. For example, in order to impart appropriate rigidity to the back surface protection sheet, the adhesion reinforcing layer is a single PP resin having excellent rigidity. If constituted solely, the adhesion between the back surface protective sheet and the sealing material tends to decrease in inverse proportion to the increase in rigidity. Therefore, in the back surface protective sheet 6 of the present invention, the core layer 621 and the skin layer 622 constituting the adhesion reinforcing layer 62 are each made of a polypropylene (PP) resin having a different monomer composition as a material resin for each layer. The content of other additives in each is optimized separately. Thereby, the back surface protection sheet 6 is improving both the adhesiveness and handling property which were in the relationship of the conventional trade-off to the preferable range.

  The core layer 621 is a layer having a function of suppressing curl deformation of the back surface protective sheet 6 by imparting appropriate rigidity to the adhesion reinforcing layer 62 itself while maintaining the adhesion of the adhesion reinforcing layer 62. Therefore, for the core layer 621, a homopolypropylene (homo PP) resin is mainly used. Homo PP is a polymer composed only of polypropylene and has high crystallinity, and therefore has excellent rigidity. By using this for the core layer, curling deformation of the back surface protective sheet 6 can be significantly suppressed and its handling property can be enhanced.

  The core layer 621 further contains an inorganic filler. Thereby, the rigidity of the adhesion reinforcing layer 62 is further increased, and the occurrence of curl deformation in the back surface protective sheet 6 is sufficiently 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. Among them, talc and titanium oxide can be preferably used in order to sufficiently improve the handling property which is the main function and effect of the present invention.

  The content of the inorganic filler in the polypropylene resin film forming the core layer 621 is 3% by mass or more and 30% by mass or less, and preferably 5% by mass or more and 25% by mass or less. When the content in the resin film is less than 3% by mass, the effect of suppressing the occurrence of curl deformation becomes insufficient, and when it exceeds 30% by mass, the mechanical strength becomes insufficient, which is not preferable.

  As the inorganic filler, talc can be particularly preferably used. However, when talc is selected as the inorganic filler to be added, the content in the resin forming the core layer is particularly preferably 5% by mass or more and 20% by mass or less. preferable. As will be shown later in Examples, when the content falls within such a range, the handling property of the back surface protection sheet 6 can be made extremely high. This is thought to be because talc has a high aspect ratio and is aligned horizontally during extrusion molding, so the shrinkage rate in the extrusion direction is small.

  In addition, when it is calculated | required that a back surface protection sheet should have a colored external appearance, it is excellent in a weather resistance among said inorganic fillers, and it is easy to obtain including price that it is easy to paint. Therefore, the white pigment may further include titanium oxide, and the black pigment may further include carbon black. 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. In particular, it has been found that titanium oxide also has an effect of improving the handleability like the above talc.

  As an example, the thickness of the core layer 621 is 40 μm or more and 160 μm or less, and is not particularly limited. When the thickness of the core layer 621 is 40 μm or more, sufficient dimensional stability can be imparted, and when the thickness of the core layer 621 is 160 μm or less, film transportability at the time of lamination is imparted. be able to.

  The skin layer 622 is a layer having a function of developing sufficient adhesion to the sealing material layer of the adhesion reinforcing layer 62. For this purpose, the skin layer 622 is made of a polypropylene resin containing 2.3% by mass or more and 5.0% by mass or less of ethylene units as a copolymer. Thus, the polypropylene resin containing an ethylene unit has lower crystallinity and better flexibility than homo PP. By using such a polypropylene resin for the skin layer 622, the adhesion of the back surface protective sheet 6 to the sealing material layer can be sufficiently enhanced. When the content of the ethylene unit in the polypropylene resin constituting the skin layer 622 is less than 2.3% by mass, the adhesion becomes insufficient. Moreover, since content of an ethylene unit exceeds 5.0 mass%, since heat resistance becomes inadequate, it is unpreferable.

  In order for the content of ethylene units in the polypropylene resin constituting the skin layer 622 to be 2.3% by mass or more and 5.0% by mass or less as described above, a certain amount of ethylene units are contained in the propylene chain. Using random polypropylene (random PP) taken in at random and homo PP, and appropriately adjusting the blending ratio of this random PP in the polypropylene resin, the content of ethylene units in the polypropylene resin is appropriately adjusted. Can be adjusted within a wide range. For example, in the case of using a random PP having an ethylene unit content of 3%, the blending ratio of the random PP is set to about 77% by mass or more, whereby the content of the polypropylene resin constituting the skin layer 622 is increased. The ethylene unit content can be 2.3 mass% or more. As described above, the “content of ethylene units in the polypropylene resin” as used in the present specification means that even when homo PP and random PP are blended in the production process, the blending ratio thereof, etc. Regardless of, the content of the ethylene unit relative to the total amount of all the polypropylene resins constituting each layer.

  It should be noted that, rather than simply blending the ethylene component, as described above, the skin layer 622 is copolymerized with the random PP, so that the skin layer is compared with the case where the PP and the polyethylene resin are simply blended. It is considered that there is a merit that the mechanical strength of 622 is easily maintained.

  The thickness of the skin layer 622 may be appropriately determined in consideration of the thickness required for the back surface protective sheet 6. As an example, the thickness of the skin layer 622 is 6 μm or more and 40 μm or less, and is not particularly limited. When the thickness of the skin layer 622 is 6 μm or more, sufficient adhesion between the back surface protective sheet 6 and the back surface sealing material layer 5 can be imparted, and the thickness of the skin layer 622 is 40 μm or less. By being, the film conveyance aptitude at the time of a lamination process can be provided. The core layer / skin layer thickness ratio is preferably 1/4.

[Weatherproof layer]
When the back surface protection sheet 6 is used for the solar cell module, the weather resistant layer 63 is positioned on the surface on the back surface side of the solar cell module. Therefore, the weather resistant layer 63 is excellent in weather resistance, heat resistance, light resistance and the like. Such resin sheets include PCTFE (polychlorotrifluoroethylene), PFA (tetrafluoroethylene perfluoroalkyl vinyl ester copolymer), PTFE (polytetrafluoroethylene), ETFE (tetrafluoroethylene / ethylene copolymer). Polymer) and resin sheets such as fluorine resins such as PVDF (polyvinylidene fluoride) are preferably exemplified. In particular, when it is necessary to impart gas barrier properties such as water vapor barrier properties to the back surface protective sheet 6, a transparent vapor deposition layer made of a metal oxide may be formed on the surface of the weather resistant layer 63. In this case, the kind of metal oxide to be deposited, the thickness of the deposited layer, and the like may be appropriately set in consideration of the performance required for the back surface protection sheet 6.

<Production method of back surface protection sheet>
The manufacturing method of the back surface protection sheet of this invention is demonstrated. The back surface protective sheet 6 includes a base resin sheet forming step for forming a base resin sheet for forming the base layer 61, an adhesive resin sheet forming step for forming an adhesive resin sheet for forming the adhesion reinforcing layer 62, and It can manufacture by passing through the integration process which laminates | stacks and integrates an adhesive resin sheet with a base resin sheet.

(Base resin sheet forming process)
The base resin sheet for forming the base layer 61 is made of the 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, and other film forming methods. It can be formed by forming a film. The base resin sheet may contain other additives such as pigments in addition to the resin material as long as the effects of the present invention are not impaired.

(Adhesive resin sheet forming process)
The adhesive resin sheet for forming the adhesion reinforcing layer 62 is composed of a resin composition for a core layer containing homo PP as a main component and containing a predetermined inorganic filler, and a resin composition for a skin layer containing random PP as a main component. Can be obtained by integral molding by a known coextrusion method. Each of the resin assemblages described above contains other additives such as other resins and pigments as long as each of them contains PP having a different monomer composition within the above-mentioned range of the predetermined amount. May be.

(Integration process)
The back surface protective sheet of the present invention is formed by laminating and further integrating the base resin sheet, the adhesive resin sheet described above, and a sheet for forming other layers formed by the same method as necessary. 6 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.

<Method for manufacturing solar cell module>
The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method. 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 1 can be manufactured by thermocompression-bonding each of the above layers as an integral molded body.

  EXAMPLES 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 backside protection sheet>
The following base resin sheets and adhesive resin sheets were sequentially laminated and integrated by dry laminating to produce backside protection sheet samples for each of Examples and Comparative Examples.
Base resin sheet: PET film (manufactured by Teijin DuPont, “Melinex S”) with a thickness of 100 μm as the base resin sheet for all back surface protection sheet samples Adhesive resin sheet: The core layer has the following homopolypropylene resin A resin composition obtained by kneading random polypropylene resin and inorganic filler in the proportions shown in Table 1 was used as the composition for the core layer. For the skin layer, a polypropylene resin obtained by kneading the following homopolypropylene resin and random polypropylene resin in the proportions shown in Table 1 was used as the composition for the core layer. Each of the above compositions was formed as a multilayer film by coextrusion to form a resin sheet having a thickness of 120 μm, and an adhesive resin sheet for the back surface protection sheet of each example and comparative example.
Homopolypropylene resin (described as “H-PP” in Table 1) density 0.900 g / cm ³ , melting point 160-170 ° C.
Random polypropylene resin (described as “R-PP” in Table 1) density 0.900 g / cm ³ , melting point 130-150 ° C. The ethylene unit content of the random polypropylene resin was 3 to 4% as disclosed by the manufacturer.
Talc (shown as “T” in Table 1)
Titanium oxide (described as “TiO ₂ ” in Table 1) Average particle size 0.2 to 0.25 μm

<Adhesion evaluation>
About each said back surface protection sheet sample of Examples 1-6 and Comparative Examples 1-3, on the surface of the said adhesion reinforcement layer (adhesive resin sheet side), the following sealing material 1 or cut to the same size as a sample The sheet 1 or 2 was laminated at 140 to 150 ° C. for 11 to 15 minutes using a vacuum laminator for manufacturing a solar cell module to obtain a sample for adhesion evaluation.
Sealant sheet 1 (indicated as “EVA” in Table 2): EVA high-speed crosslinking type, thickness 500 μm (manufactured by Bridgestone). In addition, MFR of the sealing material sheet 1 after the said lamination in 190 degreeC and load 2.16kg was 0 g / 10min.
Sealant sheet 2 (indicated as “PE” in Table 2): a resin blended so that the mass ratio of the following silane-modified transparent resin, weatherproof masterbatch, and polymerization initiator compound resin is 20: 5: 80 LLDPE resin having weak crosslinkability formed to have a thickness of 400 μm at an extrusion temperature of 210 ° C. In addition, MFR of the sealing material sheet 1 after the said lamination in 190 degreeC and a load of 2.16 kg was 0.1 g / 10min.
Silane modified transparent resin: vinyl trimethoxy with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. 2 parts by mass of silane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) are mixed, melted and kneaded at 200 ° C., density 0.884 g / cm ³ , MFR at 190 ° C. A silane-modified transparent resin having a weight of 1.8 g / 10 min.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and hindered amine light stabilizer 5 with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ A master batch in which parts by mass and 0.5 parts by mass of a phosphorous heat stabilizer are mixed, melted, processed, and pelletized.
Polymerization initiator compound resin: t-amyl-peroxy-2-ethylhexyl carbonate with respect to 100 parts by mass of M-LLDPE pellets with a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. Resin impregnated with 1 part by mass and compounded with compound pellets.

Adhesiveness was evaluated about the sample for adhesive evaluation using the samples of Examples 1-6 and Comparative Examples 1-3. Evaluation was performed based on the numerical value measured by the following method.
(Initial adhesion test: peel test)
For each sample for evaluation of adhesion, the adhesion strength was measured for adhesion with a peel strength (N) of 180 mm peel having a width of 15 mm. For the measurement, a peeling test apparatus (manufactured by “A & Day Co., Ltd., trade name“ TENSILON RTA-1150-H ”) was used, and the peeling condition was 50 mm / min at 23 ° C. at 23 ° C. Measurement was performed, and an average value of four measurements was adopted. In fact, when the above peeling was not observed, the result was “> 100 N”. The results are shown in the table.
[Evaluation criteria]
A: An adhesive strength of 80 N / 15 mm or more was evaluated as particularly preferable.
B: The adhesion strength of 40 N / 15 mm or more and less than 80 N / 15 mm was evaluated as preferable.
C: A case where the adhesion strength was less than 40 N / 15 mm was evaluated as a preferable one.

<Handling evaluation>
About each said back surface protection sheet sample of Examples 1-6 and Comparative Examples 1-3, the extent of generation | occurrence | production of curl deformation was measured with the following method, and handling property was evaluated. The results are shown in Table 1.
(Curl deformation measurement test)
The above-mentioned back surface protection sheet sample is cut into a 16 cm square, and a cut is made on the diagonal line of the 13 cm square portion at the center of the sample. The sample was allowed to stand at 60 ° C. for 24 hours and then allowed to stand at room temperature for 1 hour, and then the height of the cut tip was measured to evaluate curl deformation.
[Evaluation criteria]
A: Those less than 27 mm were evaluated as particularly preferred.
B: 27 mm or more and less than 31 mm were evaluated as preferable.
C: The thing of 31 mm or more was evaluated as unpreferable.

  From Tables 1 and 2, it can be seen that the back surface protective sheet of the present invention has excellent adhesion to the sealing material and is excellent in handling properties. On the other hand, in Comparative Example 1 in which the ratio of homo PP in the core layer is low, in the Comparative Example 2 in which the inorganic filler is sufficiently contained, the handling property is not particularly improved and the content of the inorganic filler is small. Has insufficient handleability. On the other hand, it can be seen that the adhesiveness is insufficient for Comparative Examples 2 and 3 in which the ratio of random PP in the skin layer, that is, the content of ethylene units in the polypropylene resin is small.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back surface sealing material layer 6 Back surface protection sheet 61 Base material layer 62 Adhesion reinforcement | strengthening layer 621 Core layer 622 Skin layer 63 Weather resistance layer

Claims (5)

A back surface protection sheet for a solar cell module,
A base material layer made of a resin film;
It consists of a polypropylene resin, and is arranged in the outermost layer of the back surface protection sheet, and consists of a plurality of layers including an adhesion reinforcing layer,
The adhesion reinforcing layer has a multilayer structure including a core layer and a skin layer exposed to the outermost layer,
The core layer contains a homopolypropylene resin, and the core layer contains talc in a resin component that forms the core layer in an amount of 5.0% by mass or more and 20% by mass or less.
The skin layer contains a random polypropylene resin, and the random polypropylene resin contains 2.3% by mass or more and 5.0% by mass or less of an ethylene unit in the polypropylene resin .   The back surface protective sheet for a solar cell module according to claim 1, wherein the base material layer is a polyethylene terephthalate resin.   The back surface protection sheet for solar cell modules according to claim 1, wherein the adhesion reinforcing layer is a three-layer coextruded layer of skin layer / core layer / skin layer. A transparent front substrate;
A sealing material;
Solar electronic elements,
A solar cell module comprising the back surface protective sheet for a solar cell module according to claim 1, wherein the sealing material is laminated on the adhesion reinforcing layer of the back surface protective sheet. The solar cell module according to claim 4, wherein the sealing material is a polyethylene resin or an ethylene-vinyl acetate copolymer resin.

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