JP2015191944A - Back protective sheet and solar cell module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back protective sheet having the adhesion during use, required as the sealant for solar cell module, and has the reworkability immediately after laminate, contributive to enhancement of productivity of the solar cell module.SOLUTION: A back protective sheet 6 consists of a plurality of layers including a base material layer 61, and an adhesion reinforcing layer 62 arranged on the outermost layer. The adhesion reinforcing layer 62 has a multilayer structure including a core layer 621 composed of polypropylene-based resin, and a skin layer 622 exposed to the outermost layer of the back protective sheet. The core layer 621 contains 80 mass% or more of polypropylene resin having a melting point of 160°C or more, and the skin layer 622 contains 50 mass% or more of polypropylene resin containing ethylene unit and having a melting point of 120°C-135°C.

Description

  The present invention relates to a back surface protection sheet for a solar cell module. More specifically, the present invention relates to a back surface protection sheet having reworkability preferable for a manufacturing process, and a solar cell module using the back surface protection sheet.

  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 the sealing material for the solar cell module, a polyethylene resin such as ethylene-vinyl acetate copolymer resin (EVA) is 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. As a “strengthening layer”, there is disclosed a back surface protective sheet (see Patent Documents 1 and 2) in which a polypropylene resin having excellent hydrolysis resistance and heat fusion properties is disposed in the outermost layer. The back surface protection sheet in which the adhesion reinforcing layer is made of a polypropylene resin can suppress curl deformation of the back surface protection sheet in a case where it is in a single wafer state in the work process, for example, which is preferable from the viewpoint of handling properties in the work process. Is.

Japanese Patent Laid-Open No. 2007-150084 Japanese Unexamined Patent Publication No. 2007-19059

  The back surface protection sheet, when used, has strong adhesion to the sealing material sheet, etc., and adhesion durability, assuming that it is used outdoors for a long time after integration as a solar cell module. Is required. However, on the other hand, in the manufacturing site of the solar cell module, the rear surface protection sheet after being integrated as a module in order to redo some processes and promote the reuse of some members such as solar cell elements. There has also been a demand for reworkability that allows the work to be peeled off without damaging the encapsulant sheet or the solar cell element disposed inside the encapsulant sheet or a part cut into an appropriate part. . In this specification, “reworkability” refers to the adaptability of the back surface protection sheet to such work, and “rework” refers to such work itself. .

  Such reworkability required for the back surface protection sheet mainly at the manufacturing site of the solar cell module is essentially in a trade-off relationship with the adhesion and durability required for use as a product. However, since the reworking work is performed after sealing with the sealing material, it is required that the reworking can be performed by heating again at a temperature as low as about 130 ° C to 150 ° C. Therefore, as the back surface protection sheet, a back surface protection sheet having low adhesion at 130 ° C. to 150 ° C. is ideal while having high adhesion at room temperature when used as a product. Moreover, in order to reuse the solar cell element including the encapsulant sheet, the material of the adhesion reinforcing layer of the back surface protective sheet must not be transferred to the encapsulant sheet during rework. Therefore, it is necessary to prevent the adhesion reinforcing layer from cohesive failure in the adhesion reinforcing layer during rework. Such a back surface protection sheet does not yet exist, and such a back surface protection sheet has been strongly demanded particularly in the field of manufacturing solar cell modules.

  The present invention has been made in view of the above situation, and is a back surface protection sheet for a solar cell module having high adhesion capable of withstanding use in a harsh environment for a long time, and at high temperatures. Is provided with a rework property, and an object of the present invention is to provide a back surface protection sheet for a solar cell module that can contribute to improvement of productivity of the solar cell module and recycling by reuse of the constituent members.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have made a polypropylene resin-based adhesion reinforcing layer formed on the base material layer of the back surface protection sheet in the back surface protection sheet for the solar cell module, the core layer. In particular, the skin layer has high adhesion at the time of use by using polypropylene (PP) containing an ethylene unit having a predetermined melting point range at a certain ratio. Nevertheless, the present inventors have found that a back surface protective sheet having reworkability at a high temperature immediately after laminating can be obtained and completed the present invention. More specifically, the present invention provides the following.

  (1) A back surface protection sheet for a solar cell module, comprising a base material layer and an adhesion reinforcing layer disposed on the outermost layer of the back surface protection sheet to reinforce adhesion with a sealing material. The reinforcing layer includes a core layer containing a polypropylene resin having a melting point of 160 ° C. or higher in a total resin of 80% by mass or more and a polypropylene resin containing an ethylene unit having a melting point of 120 ° C. or higher and 135 ° C. or lower and containing 50% by mass or more. A back surface protection sheet, which is a multilayer coextruded film, comprising a skin layer exposed to the surface.

  (2) The back surface protective sheet according to (1), wherein the content of the ethylene unit in the skin layer is more than 5.0% by mass and 10.0% by mass or less.

(3) The sealing material adhesion strength measured by the following adhesion test at 140 ° C. is 15 N / 15 mm or less, and the peel surface is the adhesion reinforcing layer / sealing material layer interface or the core of the adhesion reinforcing layer. The back surface protective sheet according to (1) or (2), which is a layer / skin layer interface.
Adhesion test: The adhesion reinforcing layer of the back surface protective sheet sample piece cut to a width of 15 mm was closely adhered onto the ethylene-vinyl acetate copolymer sealing material layer sample piece (75 mm × 50 mm × 0.05 mm) at 150 ° C. In 18 minutes, processing is performed with a vacuum heating laminator. Thereafter, the back protective sheet sample piece that is in close contact with the sealing material layer sample piece is subjected to a 180 degree peel (1000 mm / min) test with a peel tester at 140 ° C. to measure the adhesion strength.

  (4) The adhesion reinforcing layer is a three-layer coextruded layer of skin layer / core layer / skin layer, and the core layer contains a colored inorganic filler according to any one of (1) to (3). Back protection sheet.

  (5) A solar cell module in which the sealing material that adheres to the adhesion reinforcing layer is an ethylene-vinyl acetate copolymer (EVA) using the back surface protective sheet according to any one of (1) to (4).

  According to the present invention, the adhesion reinforcing layer formed on the base material layer of the back surface protection sheet for solar cell modules has a multilayer structure made of polypropylene resin, and the skin layer disposed on the outermost layer has a predetermined range. By molding with a polypropylene resin containing an ethylene unit with a melting point of, the adhesiveness of the back surface protection sheet to the sealing material sheet is limited to a specific range, thereby achieving high adhesion and excellent handling properties It is possible to provide a back surface protection sheet for a solar cell module that has a rework property.

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 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 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 a back surface protection according to the present invention from the light receiving surface side. The sheets 6 are sequentially stacked.

  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 made up of the front sealing material layer 3 and the back sealing material layer 5 is arranged in the solar cell module 1 to fix the position of the solar cell element 4 and to reduce the impact from the outside. It is a layer made of a resin base material. As the resin substrate for forming the sealing material layer, a thermoplastic resin such as ethylene-vinyl acetate copolymer resin (EVA), ionomer, polyvinyl butyral (PVB), polyethylene resin such as polyethylene can be used as appropriate. However, in the present invention, EVA is preferably used from the viewpoint of the balance between adhesion and reworkability.

  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.

  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 surface sealing material layer 5 described above at normal temperature. It is required to be a thing. The back surface protection sheet 6 has reworkability at high temperatures that can contribute to the improvement of productivity in the manufacturing stage of the solar module while satisfying the demands on the physical properties at the time of use as such a solar cell module. It has been made. 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 disposed so that the adhesion reinforcing layer 62 and the back surface sealing material 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 viewpoints of physical properties such as insulation performance, mechanical strength, cost, transparency, and economy, and hydrolysis resistant PET is particularly preferably used from the viewpoint of maintaining mechanical strength. it can.

  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.

  Furthermore, in the present invention, the adhesion enhancement layer 62 is adhered in order to satisfy the requirement for adhesion at room temperature, which is in use, and also has reworkability at a high temperature in the production process. By limiting the composition to a unique range, the back protection sheet 6 can be reworked at high temperatures.

  As shown in FIG. 3, 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. Thereby, appropriate rigidity can be provided to the back surface protection sheet 6.

  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 3 to 200 μm, and is not particularly limited. When the thickness of the adhesion reinforcing layer 62 is 3 μm or more, sufficient adhesion between the back surface protective sheet 6 and the back surface sealing material layer 5 can be imparted.

  For example, as shown in FIG. 4, 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 622b are sequentially laminated. Also by such a structure, it can be set as the back surface protection sheet 6 which fully improved adhesiveness and rework property with a sealing material. In addition, there exists a merit that production efficiency can be improved by setting it as such a symmetrical layer structure, and curling can be suppressed.

  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 made of polypropylene (PP) resins having different ethylene contents as material resins and used for each layer. Optimized. Thereby, the back surface protection sheet 6 is improving both the adhesiveness and rework property which were in the relationship of the conventional trade-off to the preferable range.

  Further, the adhesion strengthening layer 62 has a sealing material adhesion strength of 15 N / 15 mm or less measured by the following adhesion test at 140 ° C. in the <Issue Temperature Dependency Evaluation> test described later, and a peeled surface. However, it is preferably the adhesion reinforcing layer / encapsulant layer interface or the core layer / skin layer interface of the adhesion reinforcing layer. This means that the core layer of the adhesion reinforcing layer containing a colored pigment such as titanium oxide does not cohesively break and peels at the other laminated interface. If the core layer undergoes cohesive failure, a part of the colored pigment of the adhesion reinforcing layer 62 moves to the sealing material layer side during rework, and cannot be reused, and has no reworkability. The object of the present invention cannot be achieved.

  The core layer 621 is a layer having a function of suppressing the 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. It is a layer comprising 80% by mass or more of a polypropylene (PP) resin having a temperature of 160 ° C. or higher. In order to suppress curl deformation, it is preferable to use a homopolypropylene (homo PP) resin in the core layer 621 in an amount of 80% by mass or more based on the total resin. 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.

  Moreover, cohesive failure in the core layer at 130 to 150 ° C. can be prevented by setting the melting point of the core layer to 160 ° C. or higher. For this reason, the core layer is not coherently broken during rework, so that it is possible to provide an adhesion reinforcing layer with excellent reworkability.

  The core layer 621 preferably 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 handling properties. The content of the inorganic filler in the resin film forming the core layer 621 is not essential, and the content may be in the range of 0% to 30%, but in order to obtain more preferable handling properties, the above content is included. The amount is preferably 5% by mass or more and 25% by mass or less.

  As the inorganic filler, talc can be particularly preferably used. However, when talc is added as the inorganic filler to be added, the content in the resin forming the core layer should be 2% by mass or more and 20% by mass or less. Is particularly preferred. 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 or the like, and the black pigment may further include carbon black or the like. The inclusion of these colored pigments is preferable in that 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.

  An example of the thickness of the core layer 621 is 40 to 160 μm, 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.

<Skin layer>
The skin layer 622 is a layer having a function of developing reworkability at a predetermined temperature as well as sufficient adhesion to the sealing material layer of the adhesion reinforcing layer 62. Therefore, the skin layer 622 contains 50% by mass or more of a polypropylene resin having a melting point of 120 ° C. or higher and 135 ° C. or lower. When the polypropylene resin having a melting point of 120 ° C. or more and 135 ° C. or less is less than 50% by mass, the adhesion at room temperature is insufficient.

  The ethylene unit is preferably more than 5.0% by mass and 10.0% by mass or less. Here, the ethylene unit may be contained as a copolymer component or may be contained as a finely dispersed component such as a rubber component. Polypropylene resin containing ethylene units has lower crystallinity and better flexibility than homo PP, but can be used for the encapsulant layer of the back protection sheet 6 by adjusting the ethylene unit content to a limited range. Adhesion to time can be sufficiently enhanced, and reworkability at a high temperature such as immediately after lamination at the time of production can be imparted.

  When the melting point in the polypropylene resin constituting the skin layer 622 is higher than 135 ° C. or the content of the ethylene unit is less than 5% by mass, the adhesion at room temperature is insufficient. Further, when the melting point is less than 120 ° C. or the content of the ethylene unit exceeds 10% by mass, rework becomes extremely difficult.

  As described above, the rework temperature is about 130 ° C. to 140 ° C., and at this temperature, part of the skin layer or the melting point is higher than the melting point, and it is considered that the rework property is improved.

  As described above, in order to make the content of ethylene units in the polypropylene resin constituting the skin layer 622 more than 5.0% by mass and 10.0% by mass or less, a certain amount of ethylene units are contained in the propylene chain. The incorporated elastomer polypropylene (elastomer PP) alone or a mixed system of the elastomer PP and random PP in which a certain amount of ethylene units are incorporated in the propylene chain may be used. Thus, the content of the ethylene unit in the polypropylene resin can be adjusted to an appropriate range by appropriately adjusting the blending ratio of the elastomer PP and the random PP. For example, an elastomer PP having an ethylene unit content of 5% or more and a random PP having an ethylene unit content of about 2.5% may be used in combination. As described above, the “content of the ethylene unit in the polypropylene resin” as used in the present specification means that even when the elastomer PP and the random PP are blended in the production process, the blending ratio thereof, etc. Regardless of the above, it refers to the content of the ethylene unit relative to the total amount in all the polypropylene resins constituting each layer.

  It should be noted that, rather than simply blending the ethylene component, the skin layer 622 contains a random PP copolymerized as described above, so that the skin layer is simply blended with PP and polyethylene resin. 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 1 μm or more and 40 μm or less, and is not particularly limited. When the thickness of the skin layer 622 is 1 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 thickness ratio between the core layer 621 and the skin layer 622 can be appropriately set within a range of, for example, 50: 1 to 4: 1. The skin layer is basically transparent without containing a colored pigment such as titanium oxide.

[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 addition to resin sheets such as fluororesin, white PET in which polyethylene terephthalate (PET) includes a white pigment such as titanium oxide, transparent polyethylene terephthalate (PET), modified polyphenylene ether (m-PPE), etc. A resin sheet in which a weather-resistant resin is further laminated on the surface by coating or laminating can also be preferably used. Here, polyethylene terephthalate (PET) includes hydrolysis-resistant polyethylene terephthalate (HR-PET). In addition, examples of the weather resistant resin to be further laminated include, for example, a fluororesin, an acrylic resin, or an ionizing radiation curable resin, but are not particularly limited.

  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 layer forming process)
The adhesive resin sheet forming the adhesion reinforcing layer 62 is a resin for a skin layer comprising a resin composition for a core layer containing homo PP as a main component and containing a predetermined inorganic filler, and PP containing a certain amount of PE. The composition can be obtained by integral molding with a known coextrusion method. Each of the above resin assemblages includes other additives such as other resins and pigments as long as each PP contains PP having a predetermined monomer arrangement within the above-mentioned predetermined range. 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 adhesive resin sheet>
The following adhesive resin sheets were sequentially laminated and integrated by dry laminating to produce adhesive resin sheet samples of each example and comparative example.
Core layer: A resin composition in which the following homo PP resin is used for the core layer of the adhesive resin sheet, and the following titanium oxide as an inorganic filler is kneaded so that the content in the homo PP resin is 20% by mass. Was used as a composition for the core layer.
Homo PP: Mitsubishi Plastics Co., melting point 165 ° C
Titanium oxide: Ti-pure R105 (manufactured by Dupont), average particle size 0.2 to 0.25 μm
Skin layer: For the skin layer of the adhesive resin sheet, random PP resin containing ethylene (melting point 140 ° C., ethylene content 3% by mass) and elastomer PP resin (melting point 125 ° C., ethylene content 7% by mass) PP-based resin kneaded so that the ratio of the elastomer PP resin becomes the ratio shown in Table 1 was used as the composition for the skin layer.
Random PP resin (described as “R-PP” in Table 1): melting point 140 ° C., ethylene unit content 2.5%.
Elastomer PP resin (described as “E-PP” in Table 1): melting point 125 ° C., ethylene unit content 7%.
Each of the above compositions was formed as a multilayer film by coextrusion to obtain a resin sheet having a thickness of 60 μm (skin layer 3 μm / core layer 54 μm / skin layer 3 μm), and an adhesive resin sheet of each example and comparative example.

  The HDPE used in the comparative example is a high-density polyethylene (described as “HDPE” in Table 1, density 0.91 to 0.92, MFR 5 to 10 g / 10 min (190 ° C.)) with titanium oxide kneaded. A white high-density polyethylene film obtained by forming a composition (the content of titanium oxide in the composition of titanium oxide at 25% by mass) obtained at 60 μm by melt extrusion was used.

<Manufacture of backside protection sheet>
The adhesive resin sheets of the above Examples and Comparative Examples were laminated with a PET film (“Melinex S” manufactured by Teijin DuPont Co., Ltd.) having a thickness of 100 μm by a conventionally known dry laminating method to obtain a back surface protective sheet.

<Adhesion evaluation>
About each said back surface protection sheet of Examples 1-3 and Comparative Examples 1-4, the following sealing material sheet | seat cut into the same size as a sample is 140 on the surface of the said adhesion reinforcement layer (adhesion resin sheet side). Lamination was performed at 15 ° C. to 155 ° C. for 15 minutes using a vacuum laminator for manufacturing a solar cell module to obtain a sample for adhesion evaluation. As the sealing material sheet (indicated as “EVA” in Table 1), an EVA high-speed crosslinking type (indicated as “EVA” in Table 2), and a thickness of 500 μm (manufactured by Bridgestone) were used.

<Adhesion evaluation>
Adhesiveness was evaluated about the sample for adhesive evaluation using each sample of Examples 1-3 and Comparative Examples 1-4. 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 by peeling strength (N) at 180 ° peeling 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.

<Reworkability evaluation>
About each said back surface protection sheet sample of Examples 1-3 and Comparative Examples 1-3, rework property was evaluated on the following references | standards. The evaluation method was to relaminate the sample laminated in a module form at 145 ° C. for 20 minutes, and then peeled off using a cutter and pliers on a laminator, and confirmed its reworkability [Evaluation Criteria]
○: Reworkability is very good △: Reworkability is good ×: Reworkability is bad

<Evaluation of adhesion temperature dependence>
For Example 3 and Comparative Example 5, the temperature dependence of the adhesion was evaluated. Specifically, a sample using EVA as a sealing material sheet was heated to 80 ° C. to 140 ° C., and the adhesion strength was measured for adhesion. Moreover, the presence or absence of the cohesive failure of the adhesion reinforcement layer at the time of peeling was confirmed. For the measurement, using a peeling test apparatus (INSTRON 5565 manufactured by Instron Japan Company Limited), measurement is performed at 80 ° C. to 140 ° C. under a peeling condition of 1000 mm / min at 180 ° peeling, and an average value of two measurements is obtained. Adopted.

  From Table 2, it can be seen that the back protective sheet of the present invention retains high adhesion in EVA as a sealing material, and at the same time, is excellent in reworkability at high temperatures. On the other hand, the adhesive resin sheet using polypropylene with a low polyethylene content as in Comparative Examples 1 and 2 for the skin layer has a lower adhesive strength than that of the Examples, and the reworkability at high temperatures is also the same as that of the Examples. It turns out that it is inferior compared.

  Moreover, it turns out that the adhesive resin sheet which used the polypropylene with much polyethylene content like Comparative Examples 3 and 4 for the skin layer has weakened adhesive strength with EVA compared with an Example. Further, the adhesive resin sheet using only HDPE (high density polyethylene) as in the skin of Comparative Example 5 has high adhesion to EVA, but is inferior to the examples in reworkability at high temperatures. I understand that.

  From Table 3, it can be seen that the back protective sheet of the present invention is a back protective sheet having an extremely good reworkability because it is a sealing material adhesive layer having an average strength of 15 N / 15 mm or less and an extremely low adhesive property at 130 ° C. .

  On the other hand, the back surface protective sheet according to Comparative Example 5 exceeds the average strength of 15 N / 15 mm at 130 ° C., and the sealing material adhesion layer is cohesively broken at 140 ° C. It can be seen that the reworkability is inferior.

  As described above, the back surface protective sheet of the present invention has sufficient adhesion, and at the same time, is excellent in reworkability, and can contribute to improvement in productivity of the solar cell module. I understand.

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, and an adhesion reinforcing layer that is arranged in the outermost layer of the back surface protection sheet to reinforce the adhesion with the sealing material,
The adhesion reinforcing layer is
A core layer containing a polypropylene resin having a melting point of 160 ° C. or higher in an amount of 80% by mass or more in the total resin;
A back surface protective sheet, which is a multilayer coextruded film, comprising: a skin layer containing 50% by mass or more of a polypropylene resin containing an ethylene unit and having a melting point of 120 ° C. or higher and 135 ° C. or lower and exposed to the outermost layer.   The back surface protection sheet according to claim 1 whose content of said ethylene unit in said skin layer is more than 5.0 mass% and 10.0 mass% or less. The sealing material adhesion strength measured by the following adhesion test at 140 ° C. is 15 N / 15 mm or less, and the peel surface is the adhesion reinforcing layer / sealing material layer interface, or the core layer / skin of the adhesion reinforcing layer. The back surface protective sheet according to claim 1, which is a layer interface.
Adhesion test: The adhesion reinforcing layer of the back surface protective sheet sample piece cut to a width of 15 mm was closely adhered onto the ethylene-vinyl acetate copolymer sealing material layer sample piece (75 mm × 50 mm × 0.05 mm) at 150 ° C. In 18 minutes, processing is performed with a vacuum heating laminator. Thereafter, the back protective sheet sample piece that is in close contact with the sealing material layer sample piece is subjected to a 180 degree peel (1000 mm / min) test with a peel tester at 140 ° C. to measure the adhesion strength.   The back surface protective sheet according to any one of claims 1 to 3, wherein the adhesion reinforcing layer is a three-layer coextruded layer of skin layer / core layer / skin layer, and the core layer contains a colored inorganic filler.   A solar cell module using the back surface protective sheet according to any one of claims 1 to 4, wherein the sealing material in close contact with the adhesion reinforcing layer is an ethylene-vinyl acetate copolymer.

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