JP2013168523A - Protective sheet for solar cell, method for manufacturing the same, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective sheet for a solar cell capable of suppressing occurrence of a warpage or track manifestation in a solar cell module with the protective sheet even when the sheet is manufactured by extrusion coating, a method for manufacturing the sheet, and a solar cell module with the sheet.SOLUTION: A protective sheet 1 for a solar cell comprises a base material 11 and a thermoplastic resin layer 12 laminated on one surface of the base material 11. The thermoplastic resin layer 12 includes a thermoplastic resin A and a thermoplastic resin B. The thermoplastic resin A is composed of an olefin-based resin whose density is less than 920 kg/m. The thermoplastic resin B has a higher density than the thermoplastic resin A and is composed of a resin compatible with the thermoplastic resin A. The thermoplastic resin layer has a density higher than or equal to 875 kg/mand less than or equal to 920 kg/mand a fusion peak temperature of 95°C or higher.

Description

  The present invention relates to a solar cell protective sheet used as a surface protective sheet or a back surface protective sheet of a solar cell module, a method for producing the same, and a solar cell module using the solar cell protective sheet.

  Solar cell modules that convert solar light energy into electrical energy are attracting attention as a clean energy source that can generate electricity without emitting carbon dioxide in response to environmental problems such as air pollution and global warming.

  In general, a solar cell module is composed of a solar cell made of crystalline silicon, amorphous silicon or the like that performs photoelectric conversion, a sealing material (filler) made of an electrical insulator that seals the solar cell, and the surface of the sealing material. It is comprised from the surface protection sheet (front sheet) laminated | stacked on (light-receiving surface) and the back surface protection sheet (back sheet) laminated | stacked on the back surface of the sealing material. In order to provide the solar cell module with the weather resistance and durability that can withstand long-term use outdoors, the solar cell module and sealing material are protected from wind, rain, moisture, dust, mechanical shock, etc. It is necessary to keep the inside of the interior sealed from the outside air. For this reason, the protection sheet for solar cells is required to have moisture resistance and weather resistance that can withstand long-term use.

  Patent Document 1 discloses a solar cell module in which a silicon power generation element is sealed with a sealing material made of an ethylene-vinyl acetate copolymer sheet, and a back sheet is laminated on the back surface of the sealing material. As a back sheet, a sheet in which a fluorine-based plastic film having weather resistance (Tedlar film manufactured by DuPont) is bonded to one side or both sides of a layer that prevents water vapor permeation, such as metal, is disclosed. This back sheet is heat-bonded to the sealing material.

  However, the conventional back sheet as disclosed in Patent Document 1 has a problem in that the back sheet peels off from the sealing material and water vapor enters the sealing material because of low adhesion to the sealing material. Therefore, it has been proposed to provide a heat-sealable layer on the back sheet to improve the adhesion to the above-mentioned sealing material.

  Specifically, Patent Document 2 discloses a back sheet laminated on the back surface of a filler in a solar cell module using an ethylene-vinyl acetate copolymer as a filler, and includes an epoxy compound and / or a silane compound. A heat-fusible layer made of a heat-fusible resin composed mainly of a graft-modified ethylene- (meth) acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, or a mixture thereof is laminated on a heat-resistant film. Has been disclosed.

  In patent document 2, when manufacturing a back sheet, a heat-fusible layer is laminated | stacked with an extrusion coating method with respect to a heat resistant film. Such a method of forming a heat-fusible layer has high productivity, but has a problem that shrinkage occurs due to cooling of the heat-fusible layer and curls occur in the width direction or the flow direction of the roll. If the solar cell module is warped along with the curl of the back sheet, not only will the malfunction occur when the solar cell module is installed, but the solar cell module may be damaged.

  Such curling occurs not only in a laminate in which a heat-fusible layer is laminated on a backsheet, but also, for example, a backsheet and a sealing material on the back side as described in Patent Documents 3 to 5 are laminated. This also causes a problem in the integrated backsheet.

Japanese Patent Laid-Open No. 6-177412 JP 2008-108947 A JP 2011-35289 A JP 2011-49227 A JP 2011-49228 A

  In recent years, since the demand for improving the design and quality of products has been increasing, the occurrence of the phenomenon described below has been regarded as a problem.

  As shown also in FIG. 1 of Patent Document 2, a solar cell module normally contains a plurality of solar cells, and these cells are also referred to as metal wiring (in this specification, “tab line”). ) Are electrically connected to each other. Therefore, at least one of the tab wires is encapsulated with a plurality of solar cells. This tab line may be hidden by a backsheet colored white or black.

  In the process of heating and sealing the solar cell module, the concealability of the backsheet is reduced, and a phenomenon in which the tab wire can be seen through (this phenomenon is also referred to as “line trace manifestation” in this specification) may occur. there were.

  This invention is made | formed in view of such an actual condition, Comprising: It is a protection sheet for solar cells provided with the thermoplastic resin layer and the base material, Comprising: Even when manufactured by extrusion coating, this sheet | seat is provided. PROBLEM TO BE SOLVED: To provide a solar cell protective sheet capable of suppressing the occurrence of warpage in the solar cell module and the occurrence of line traces, a method for producing the sheet, and a solar cell module provided with such a solar cell protective sheet. Objective.

When the present inventors examined in order to achieve the said objective, the following knowledge was acquired.
When the resin as the main component of the thermoplastic resin composition constituting the thermoplastic resin layer provided in the solar cell protective sheet is a relatively low density thermoplastic resin, the shrinkage rate when produced by extrusion coating is reduced. Therefore, the curl amount of the protective sheet for solar cells is reduced, and the occurrence of warpage of the solar cell module including such a sheet is suppressed. This point is also disclosed in Patent Documents 3 to 5.

  However, since the thermoplastic resin layer made of such a thermoplastic resin composition tends to be highly flexible, the amount of deformation of the backsheet around the tab wire becomes excessive when placed in a high temperature environment as described above. Cheap. As a result, the presence of the tab line can be recognized.

  Hardening the thermoplastic resin composition constituting the thermoplastic resin layer is preferable from the viewpoint of avoiding the occurrence of line traces, but the thermoplastic resin contained in the thermoplastic resin composition is simply hard. If it changes into a thing, the curvature amount mentioned above will become large and the curvature of a solar cell module provided with the protection sheet for solar cells will become remarkable.

  The resin component contained in the thermoplastic resin composition is not limited to a relatively low density thermoplastic resin, but is compatible with the low density thermoplastic resin and has a relatively high density. By including a thermoplastic resin, it is possible to simultaneously suppress the warpage in the solar cell module and the suppression of the occurrence of line traces.

The present invention completed based on such knowledge is, firstly, a solar cell protective sheet comprising a base material and a thermoplastic resin layer laminated on at least one surface of the base material. The plastic resin layer is composed of a thermoplastic resin composition including a thermoplastic resin A and a thermoplastic resin B, and the thermoplastic resin A is composed of an olefin resin having a density of less than 920 kg / m ³ , and the thermoplastic resin. The resin B has a higher density than the thermoplastic resin A and is made of a resin that is compatible with the thermoplastic resin A. The thermoplastic resin composition has a density of 875 kg / m ³ or more and 920 kg / m ³ or less. And the melting peak temperature is 95 degreeC or more, The protective sheet for solar cells characterized by the above-mentioned is provided (invention 1).

Second, the present invention is a solar cell protective sheet comprising a base material and a thermoplastic resin layer laminated on at least one surface of the base material, the thermoplastic resin providing the thermoplastic resin layer The resin composition includes a thermoplastic resin A and a thermoplastic resin B. The thermoplastic resin A is made of an olefin resin having a density of less than 920 kg / m ³ , and the thermoplastic resin B is the thermoplastic resin. The thermoplastic resin composition has a higher density than A and is compatible with the thermoplastic resin A, and the thermoplastic resin composition has a density of 875 kg / m ³ or more and 920 kg / m ³ or less, and is stored at 80 ° C. Provided is a protective sheet for a solar cell having an elastic modulus of 3 MPa or more (Invention 2).

  Since the thermoplastic resin layer according to the above inventions (Inventions 1 and 2) is composed of a plurality of thermoplastic resin compositions that are compatible as described above, the characteristics of each resin composition (easy to relieve stress) As a synergistic effect such as excellent heat resistance, it is possible to simultaneously achieve suppression of warpage and suppression of occurrence of line traces.

  In said invention (invention 2), it is preferable that the melting peak temperature of the said thermoplastic resin composition is 95 degreeC or more (invention 3). In this case, it is possible to more stably realize the suppression of warpage and the suppression of occurrence of line traces at the same time.

  In said invention (invention 1-3), it is preferable that the said thermoplastic resin A contains 60 to 100 mass% of ethylene as a monomer unit (invention 4). In this case, it becomes easy to satisfy the conditions required for the thermoplastic resin A.

  In said invention (invention 1-4), it is preferable that the melting peak temperature of the said thermoplastic resin B is 95 degreeC or more (invention 5). In this case, it becomes easy to satisfy the conditions required for the thermoplastic resin composition.

  In said invention (invention 1-5), the said thermoplastic resin composition may contain a coloring material (invention 6). In this case, it is easy to hide the tab lines and the like.

  In said invention (invention 1-6), it is preferable that the said thermoplastic resin layer is what the said thermoplastic resin composition was laminated | stacked on one surface of the said base material by extrusion coating. (Invention 7). In this case, the adhesive force between the thermoplastic resin layer and the base material is increased, and the possibility that they peel off can be reduced.

  In said invention (invention 1-7), you may provide the intervening layer which consists of an adhesive composition which has the adhesiveness with respect to these between the said thermoplastic resin layer and the said base material (invention 8). Also in this case, the adhesive force between the thermoplastic resin layer and the base material is increased, and the possibility that they peel off can be reduced.

  In the above invention (Invention 8), the adhesive composition mainly comprises a copolymer of ethylene and at least one selected from the group consisting of (meth) acrylic acid, (meth) acrylic acid ester and vinyl acetate. It is preferable to use as a component (Invention 9). Since these copolymers have adhesiveness to the base material and the thermoplastic resin layer, they are suitable as an intervening layer.

  In the above inventions (Inventions 8 and 9), the thermoplastic resin layer and the intervening layer are formed by coextrusion coating of the thermoplastic resin composition and the adhesive composition on the substrate. It is preferable that it is made (Invention 10). In this case, the adhesive force of the intervening layer to the thermoplastic resin layer can be particularly increased, and the possibility that the base material and the thermoplastic resin layer are peeled can be further reduced.

  In the above inventions (Inventions 1 to 10), the thermoplastic resin layer may be a layer bonded to a sealing material constituting the solar cell module (Invention 11). Since the thermoplastic resin layer is excellent in adhesiveness with the sealing material, the protective sheet for solar cell is difficult to peel from the sealing material.

  Thirdly, the present invention is a method for producing a protective sheet for a solar cell comprising a base material and a thermoplastic resin layer laminated on at least one surface of the base material. To 6), a method for producing a protective sheet for a solar cell, wherein the thermoplastic resin layer is formed by extrusion-coating the thermoplastic resin composition according to any one of 6 to 6 on at least one surface of the substrate. (Invention 12).

  Since the adhesive force between the thermoplastic resin layer and the substrate is increased by forming the thermoplastic resin layer by extrusion coating, it is possible to reduce the possibility of these peeling.

  Fourthly, the present invention comprises a base material, a thermoplastic resin layer, an adhesive composition having adhesiveness to the base material and the thermoplastic resin layer, and one surface of the base material and the plastic resin layer. A method for producing a protective sheet for a solar cell comprising an intervening layer laminated between one side of the thermoplastic resin composition according to any one of the inventions (Inventions 1 to 6), Provided is a method for producing a protective sheet for a solar cell, which comprises coextruding an adhesive composition on at least one surface of the substrate to form the intervening layer and the thermoplastic resin layer. (Invention 13).

  By forming the intervening layer and the thermoplastic resin layer by extrusion coating, the adhesive force between the intervening layer and the thermoplastic resin layer and the adhesive force between the thermoplastic resin layer and the base material are increased, so that they may peel off. Can be reduced.

  In the above invention (Invention 13), the adhesive composition is mainly composed of a copolymer of ethylene and at least one selected from the group consisting of (meth) acrylic acid, (meth) acrylic acid ester and vinyl acetate. (Invention 14) Since these copolymers have adhesiveness to the base material and the thermoplastic resin layer, they are suitable as an intervening layer.

  Fifth, the present invention provides a plurality of solar cells, electrical wiring for electrically connecting the plurality of solar cells, and sealing that encloses the plurality of solar cells and at least one of the electrical wirings. A solar cell module comprising two protective members stacked on each of the main surfaces of the material and the sealing material, wherein at least one of the protective members is the sun according to any of the above inventions (Inventions 1 to 10) Provided is a solar cell module comprising a battery protective sheet, wherein the thermoplastic resin layer provided in the solar cell protective sheet forms part or all of the sealing material (Invention 15).

  Since the solar cell protective sheet according to any one of the above inventions (Inventions 1 to 10) has excellent adhesion to a sealing material or the like, the solar cell module provided with such a solar cell protective sheet is a line trace. It has the effect based on the solar cell protective sheet that hardly manifests, and hardly changes with time in quality.

  The solar cell protective sheet according to the present invention has a small curl amount because the density of the thermoplastic resin layer is low. Therefore, warpage occurring in the solar cell module is suppressed. In addition, the thermoplastic resin forming the main surface on one side of the sheet has a high melting peak temperature and / or a high storage elastic modulus at a high temperature although the density is relatively low. Even if a solar cell module using a protective sheet as a front sheet and / or a back sheet is left in a high-temperature environment, line traces are unlikely to appear.

It is a schematic sectional drawing of the protection sheet for solar cells which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the protection sheet for solar cells provided with the intervening layer based on other embodiment of this invention. It is a schematic sectional drawing of the protection sheet for solar cells provided with the fluororesin layer based on other embodiment of this invention. It is a schematic sectional drawing of the protection sheet for solar cells provided with a vapor deposition layer based on other embodiment of this invention. It is a schematic sectional drawing of the protection sheet for solar cells provided with the contact bonding layer and metal sheet based on other embodiment of this invention. It is a schematic sectional drawing of the solar cell module which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the solar cell module which the front seat and back seat | sheet concerning other embodiment of this invention consist of the protection sheet for solar cells which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described.
1. Protective sheet for solar cell As shown in FIG. 1, a protective sheet 1 for a solar cell according to the present embodiment is a thermoplastic layered on a base material 11 and one surface (upper surface in FIG. 1) of the base material 11. And a resin layer 12. In one specific example, the solar cell protective sheet 1 has a thermoplastic resin layer 12 functioning as a heat-fusible layer to a sealing material, and a solar cell module surface protective sheet (front sheet) or back surface protective sheet ( Back sheet). In another specific example, in the solar cell protective sheet 1, the thermoplastic resin layer 12 substantially has a function of a sealing material, and is an integrated sheet of a sealing material and a front sheet or a sealing material. It is used as an integrated sheet with a back sheet. Hereinafter, a case where the solar cell protective sheet 1 is used as a front sheet or a back sheet will be mainly described, and a case where the thermoplastic resin layer 12 also substantially has a function of a sealing material will be described as appropriate.

(1) Base Material The base material 11 may be any material as long as it has electrical insulation and can be laminated with the thermoplastic resin layer 12, and a material mainly composed of a resin film is usually used.

  As a resin film used for the base material 11, what is generally used as the resin film in the solar cell module backsheet is selected. Examples of such a resin film include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyamide resins such as nylon (trade name), polycarbonate resins, and polystyrene. A film made of a resin such as a resin, a polyacrylonitrile resin, a polyvinyl chloride resin, a polyvinyl acetal resin, a polyphenylene sulfide resin, or a polyphenylene ether resin is used. Among these resin films, a film made of a polyester resin is preferable, and a PET film is particularly preferable.

  In addition, the said resin film may contain various additives, such as a pigment, a ultraviolet absorber, a ultraviolet stabilizer, a flame retardant, a plasticizer, an antistatic agent, a lubricant, and an antiblocking agent, as needed. Examples of the pigment include titanium dioxide and carbon black. Examples of the ultraviolet absorber include benzophenone series, benzotriazole series, oxalic acid anilide series, cyanoacrylate series, and triazine series.

  Here, when using the solar cell protective sheet 1 according to this embodiment as a back sheet of a solar cell module, the resin film preferably contains a pigment that reflects visible light. Moreover, when using the solar cell protective sheet 1 according to the present embodiment as a front sheet of a solar cell module, it is preferable not to contain a pigment that reduces the light transmittance in the visible light region, thereby improving the weather resistance. It is more preferable to contain an ultraviolet absorber for the purpose.

  In order to improve the adhesion to the thermoplastic resin layer 12 on the surface of the resin film on which the thermoplastic resin layer 12 is laminated, surface treatment such as corona treatment, plasma treatment, primer treatment, etc. is used as an easy adhesion treatment. It is preferable to apply.

  The thickness of the base material 11 is appropriately set based on the electrical insulation required for the solar cell module. For example, when the substrate 11 is a resin film, the thickness is preferably 10 μm or more and 300 μm or less. More specifically, when the substrate 11 is a PET film, the thickness is preferably 10 μm or more and 300 μm or less, and 20 μm or more and 250 μm or less from the viewpoint of electrical insulation and weight reduction. It is more preferable that it is 30 μm or more and 200 μm or less.

(2) Thermoplastic resin layer In one specific example, the thermoplastic resin layer 12 in the present embodiment is bonded to a sealing material, whereby the solar cell protective sheet 1 including the substrate 11 is solar cell module. It is for fixing to. In another specific example, the thermoplastic resin layer 12 substantially has a function of a sealing material, and encloses solar cells and the like to protect them, while in other sealing materials and other protective sheets. It is for adhering to a heat-fusible layer, a base material of another protective sheet, or the like.

i) Thermoplastic Resin Composition The thermoplastic resin layer 12 in the present embodiment is composed of a thermoplastic resin composition, and this thermoplastic resin composition is composed of a thermoplastic resin A and a thermoplastic resin B (details of these resins are described in detail). Will be described later).
The thermoplastic resin composition according to this embodiment has a density of 875 kg / m ³ or more and 920 kg / m ³ or less. The density is a value obtained by measurement according to JIS K7112. The thermoplastic resin composition satisfies at least one of the melting peak temperature of 95 ° C. or higher and the storage elastic modulus at 80 ° C. of 3 MPa or higher, preferably both. The melting peak temperature can be measured with a differential scanning calorimeter, and the storage elastic modulus can be measured with a dynamic viscoelasticity measuring device.

When the density of the thermoplastic resin composition is 920 kg / m ³ or less, the solar cell protective sheet 1 provided with the thermoplastic resin layer 12 obtained from this thermoplastic resin composition can be curled even if manufactured by extrusion coating. Since the amount is reduced, the warpage of the solar cell module including such a sheet is suppressed. Specifically, when the solar cell protective sheet 1 is cut into a 300 mm × 300 mm square and placed on a horizontal table, the warpage of the solar cell module is suppressed when the vertical curl amount is 20 mm or less. Although it is possible, the solar cell protective sheet 1 according to this embodiment can suppress the curl amount to 20 mm or less even when the solar cell protective sheet 1 includes the base material 11 and the thermoplastic resin layer 12.

On the other hand, when the density of the thermoplastic resin composition is 875 kg / m ³ or more, problems that occur when the solar cell protective sheet 1 is a wound body are less likely to occur. Specifically, when the thermoplastic resin layer 12 is tucked and the solar cell protective sheet 1 is wound up, blocking occurs, and the solar cell protective sheet 1 fed out has a blocking mark or is wound up. It is suppressed that the protective sheet 1 for solar cells cannot be paid out. Moreover, when the density of a thermoplastic resin composition is 875 kg / m < ³ > or more, it becomes easy to make the storage elastic modulus in 80 degreeC of a thermoplastic resin composition into 3 MPa or more (it mentions later for details).

From the viewpoint of more stably suppressing the occurrence of warpage and the occurrence of problems during winding, the density of the thermoplastic resin composition is preferably 875 kg / m ³ or more and 920 kg / m ³ or less, and 880 kg / m ^3. and particularly preferably ³ or more 910 kg / ^{m 3} or less.

  Since the thermoplastic resins A and B are compatible with each other as described later, the thermoplastic resin composition has a single melting peak temperature. In this embodiment, “the thermoplastic resins A and B are compatible” means a melting peak obtained by measuring a resin composition obtained by mixing the thermoplastic resin A and the thermoplastic resin B with a differential scanning calorimeter. It means that the temperature is substantially a single peak.

  When the melting peak temperature is 95 ° C. or higher, the content of the thermoplastic resin B in the thermoplastic resin composition falls within an appropriate range. For this reason, excessive deformation of the thermoplastic resin layer 12 is suppressed even if a heat resistance evaluation test is performed under a high temperature condition based on the thermoplastic resin B. Therefore, a solar cell module including the protective sheet 1 for a solar cell provided with a thermoplastic resin layer made of a thermoplastic resin composition having such characteristics as a constituent element is not subjected to a heat resistance evaluation test under a high temperature condition. Traces are unlikely to occur. From the viewpoint of stably suppressing the occurrence of line traces, the melting peak temperature of the thermoplastic resin composition is preferably 100 ° C or higher, and more preferably 105 ° C or higher.

  The upper limit of the melting peak temperature is not particularly limited, but since the upper limit is set for the density of the thermoplastic resin composition as described above, it is actually difficult to reach 140 ° C. or higher.

  When the storage elastic modulus at 80 ° C. of the thermoplastic resin composition is 3 MPa or more, the thermoplastic resin layer 12 may be excessively deformed around the tab wire even if a heat resistance evaluation test is performed under high temperature conditions. It is suppressed. For this reason, the solar cell protective sheet 1 that hardly causes line traces in the solar cell module is obtained. From the viewpoint of further stably suppressing the occurrence of line traces, the storage elastic modulus at 80 ° C. of the thermoplastic resin composition is preferably 3 MPa or more, more preferably 5 MPa or more, and particularly preferably 10 MPa or more. preferable.

  Although the upper limit of the storage elastic modulus at 80 ° C. is not particularly limited, since the upper limit is set for the density of the thermoplastic resin composition as described above, it is actually difficult to be 50 MPa or more.

  Obtaining the effect of suppressing the occurrence of line traces in the solar cell module if either the above melting peak temperature condition or the storage elastic modulus condition at 80 ° C. in the thermoplastic resin composition is satisfied. However, it is preferable to satisfy both of the conditions because the occurrence of line traces can be more stably suppressed.

  Further, the blending ratio of the thermoplastic resins A and B contained in the thermoplastic resin composition is such that the thermoplastic resin composition satisfies the conditions regarding the above density, and the melting peak temperature and / or the storage elastic modulus at 80 ° C. As long as it is satisfied, there is no particular limitation. Based on the above conditions and the compositions of the thermoplastic resins A and B, the range of this blending ratio should be determined, and the content of the thermoplastic resin A in the thermoplastic resin composition is that of the thermoplastic resin B. In many cases, it is equal to or more than the content. If an example of the compounding ratio (mass ratio) of the thermoplastic resin B with respect to the thermoplastic resin A in such a case is mentioned, it will be the range of 0.05-1.0.

  Even if the thermoplastic resin layer 12 in this embodiment is a single layer, since it can suppress generation | occurrence | production of the curvature in a solar cell module provided with the protection sheet 1 for solar cells, it is a single layer also from the surface of material cost and manufacturing cost. It is preferable that

  In addition to the thermoplastic resins A and B described later, the thermoplastic resin composition constituting the thermoplastic resin layer 12 includes, as necessary, a coloring material such as titanium dioxide, an antiblocking agent such as silica particles, and a benzophenone. Various additives such as an ultraviolet absorber, an ultraviolet stabilizer, a flame retardant, a plasticizer, an antistatic agent and a lubricant may be contained.

  The thickness of the thermoplastic resin layer 12 is not particularly limited as long as it exhibits desired adhesion to the adherend and does not impair the effects of the present invention. Specifically, the thickness of the thermoplastic resin layer 12 when used as a heat-fusible layer is preferably 1 μm or more and 200 μm or less, and 10 μm or more and 180 μm or less from the viewpoint of electrical insulation and weight reduction. Is more preferably 50 μm or more and 150 μm or less, and particularly preferably 80 μm or more and 120 μm or less. When the thermoplastic resin layer 12 is also used as a sealing material, the thickness may be about 1 mm at the maximum.

ii) Thermoplastic resin A
The thermoplastic resin A contained in the thermoplastic resin composition is an olefin resin having a density of less than 920 kg / m ³ .

When the density of the thermoplastic resin A is excessively high, the possibility that the solar cell module including the solar cell protective sheet 1 is warped increases. From more stably suppressing the warpage, the density of the thermoplastic resin A is preferably at 915 kg / ^{m 3} or less, more preferably 910 kg / ^{m 3} or less. On the other hand, when the density of the thermoplastic resin A is excessively low, the density as the thermoplastic resin composition is also low, and there is a possibility that the above-described problems during winding and / or line traces may occur. Rise. Accordingly, the density of the thermoplastic resin A is preferably more than 875 kg / m ^{3, and} more preferably 880 kg / m ³ or more.

  In the present embodiment, the olefin-based resin is a homopolymer or copolymer composed of a monomer composed of olefin, and a copolymer composed of a monomer composed of an olefin and a molecule other than olefin, The thermoplastic resin whose mass ratio of the part based on the olefin unit in resin is 1.0 mass% or more is meant.

  The thermoplastic resin layer 12 made of a thermoplastic resin composition containing the thermoplastic resin A, which is an olefin resin, has high adhesion to the sealing material of the solar cell module due to the excellent heat-sealing action of the olefin resin.

  Specific examples of the thermoplastic resin A which is an olefin resin include polyethylene resin, polypropylene resin (PP), polyethylene-polypropylene polymer, olefin elastomer (TPO), cycloolefin resin, ethylene-vinyl acetate copolymer (EVA). , Ethylene-vinyl acetate-maleic anhydride copolymer, ethylene- (meth) acrylic acid copolymer, ethylene-butyl acrylate copolymer (EBA), ethylene- (meth) acrylic acid ester-maleic anhydride copolymer Examples include coalescence. In addition, in this specification, (meth) acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.

  The monomer constituting the thermoplastic resin A, which is an olefin resin, is preferably mainly composed of ethylene, and specifically, preferably contains 60% by mass to 100% by mass of ethylene as a monomer unit. . When the ethylene content is less than 60% by mass, it is difficult to adjust the density of the thermoplastic resin A within the above range, and the adhesiveness of the solar cell module to the sealing material decreases. The possibility increases. From the viewpoint of easily satisfying the density range of the thermoplastic resin A and increasing the adhesion to the sealing material, the higher the ethylene content, the more preferable, specifically 70 mass or more. It is preferable that it is 80 mass% or more. All of the monomers constituting the thermoplastic resin A may be ethylene. In the case of using a monomer other than ethylene from the viewpoint of increasing the affinity with the material constituting the encapsulant, a high content of the monomer is preferable from the viewpoint of increasing the adhesiveness of the encapsulant. The upper limit of the content of the monomer in the thermoplastic resin A is determined so as to satisfy other conditions such as the above-described density range to be satisfied by the thermoplastic resin A.

  The polymer constituting the thermoplastic resin A may be one type or a blend of a plurality of types of polymers. Here, the types of polymers are different from the states of branching (that is, polymer architecture), molecular weight, blending balance of monomers constituting the polymer, and composition of the monomers constituting the polymer, and It means that these combinations are different to the extent that they have a great influence on physical properties.

  From the viewpoint of stably satisfying that the density of the thermoplastic resin A is in the above range with respect to the branched state, it is preferable that the degree of branching per polymer is small. A preferred example of such a polymer having a low degree of branching is a metallocene linear low density polyethylene. Such polyethylene is synthesized using a metallocene catalyst, which is a single site catalyst, and is a linear polymer with a low degree of branching. For this reason, it becomes easy to make the density of the thermoplastic resin A into said range.

From the viewpoint of easily satisfying the conditions to be satisfied by the above-described thermoplastic resin composition, the conditions relating to the density range of the above-described thermoplastic resin A, and the conditions to be satisfied by the thermoplastic resin B described later, The olefin resin is preferably low density polyethylene (LDPE) or very low density polyethylene (VLDPE), and is a linear low density polyethylene synthesized using a metallocene catalyst and has a density of 875 kg / m ³ or more. More preferably, it is less than 920 kg / m ³ .

  The thermoplastic resin A may have a crosslinked structure. The kind of the crosslinking agent that brings about the crosslinked structure is arbitrary, and a compound having an organic peroxide such as dicumyl peroxide or an epoxy group is typical. However, from the viewpoint of facilitating the density range of the thermoplastic resin A to be within the above range, it is preferable that the density of the crosslinked structure in the thermoplastic resin A is small, and the thermoplastic resin A substantially has a crosslinked structure. More preferably not.

  Other characteristics of the thermoplastic resin A are not particularly limited, but from the viewpoint of stably realizing the melting peak temperature of the thermoplastic resin composition at 95 ° C. or higher, the melting peak temperature of the thermoplastic resin A is 85 ° C. It is preferable that the temperature is lower than 95 ° C.

  The thermoplastic resin A has a melt flow rate value of 1 g / 10 min or more and 40 g / 10 min or less at a temperature of 230 ° C. and a load of 2.16 kgf based on JIS K7210: 1999 from the viewpoint of workability and the like. preferable. In particular, from the viewpoint of stably processing the thermoplastic resin layer 12 by extrusion coating, the melt flow rate is preferably 2 g / 10 min or more and 20 g / 10 min or less.

iii) Thermoplastic resin B
The thermoplastic resin B has a higher density than the thermoplastic resin A and is compatible with the thermoplastic resin A. As long as the thermoplastic resin B satisfies the above-described conditions, and the thermoplastic resin composition containing the thermoplastic resin A and the thermoplastic resin B satisfies the above-described conditions, other structural and physical properties of the thermoplastic resin B Features are not limited.

The thermoplastic resin B is preferably made of an olefin resin in the same manner as the thermoplastic resin A from the viewpoint of satisfying the compatibility condition with the thermoplastic resin A described above. Moreover, when the monomer which comprises the olefin resin which concerns on the thermoplastic resin A has ethylene as a main component, the single quantity which comprises the thermoplastic resin B from a compatible viewpoint to this ethylene-based polymer. The body is also preferably composed mainly of ethylene. When the olefin resin related to the thermoplastic resin A is a linear low density polyethylene synthesized using the metallocene catalyst described above and has a density of 875 kg / m ³ or more and less than 920 kg / m ³ , preferably the thermoplastic resin B is 920 kg / ^{m 3} or more 970 kg / ^{m 3} or less of polyethylene, more preferably a 920 kg / ^{m 3} or more 965 kg / ^{m 3} or less of polyethylene.

  The thermoplastic resin B may have a crosslinked structure, but it is preferable that the thermoplastic resin B substantially does not have a crosslinked structure. From the viewpoint of increasing the compatibility with the thermoplastic resin A, the density of the crosslinked structure in the thermoplastic resin B is present. Is preferable, and it is further preferable that the thermoplastic resin B does not substantially have a crosslinked structure.

  The thermoplastic resin B preferably has a melting peak temperature of 95 ° C. or higher, more preferably 110 ° C. or higher, from the viewpoint that the thermoplastic resin composition stably satisfies the above-described conditions regarding the melting peak temperature. More preferably, the temperature is 120 ° C. or higher. The upper limit of the melting peak temperature of the thermoplastic resin B is not particularly limited, but if it is excessively high, it is difficult for the thermoplastic resin B to be compatible with the thermoplastic resin A. The degree is the upper limit.

  In addition, the thermoplastic resin B has a melt flow rate value of 0.1 g / 10 min or more and 20 g / 10 min or less at a temperature of 230 ° C. and a load of 2.16 kgf based on JIS K7210: 1999. It is preferable from the viewpoint. In particular, from the viewpoint of stably processing the thermoplastic resin layer 12 by extrusion coating, the melt flow rate is preferably 2 g / 10 min or more and 10 g / 10 min or less.

(3) Intervening Layer As shown in FIG. 2, the solar cell protective sheet 1 according to the present invention is provided between the base material 11 and the thermoplastic resin layer 12 as shown in FIG. An intervening layer 12 ′ made of an adhesive composition having adhesiveness may be provided. In other words, the intervening layer 12 ′ is laminated between one surface of the base material 11 and one surface of the thermoplastic resin layer 12. The intervening layer is used to firmly bond the base material 11 and the thermoplastic resin layer 12, and may be referred to as a tie layer.
The intervening layer 12 ′ is a copolymer of ethylene and at least one selected from the group consisting of (meth) acrylic acid, (meth) acrylic acid ester and vinyl acetate (hereinafter referred to as “copolymer F”). It is preferable that the main component is. Here, “having the main component” means that the copolymer F is contained to such an extent that the characteristics derived from the copolymer F are dominant for the characteristics of the intervening layer 12 ′. The specific content of the copolymer F in the adhesive composition is not definitely determined because of the influence of other components. For example, the content of the copolymer F in the adhesive composition Is more than 50% by mass, and the higher the content, the better. The intervening layer 12 'made of the above material has a high adhesive force to the base material 11, particularly the base material 11 made of a resin film, and further to the base material 11 made of a PET film.

The copolymer F, which is the main component of the intervening layer 12 ', is amorphous (non-crystalline) at room temperature and has elasticity. Therefore, even if the thermoplastic resin layer 12 containing an olefin resin as a main component shrinks when cooled from the heat-melted state, the shrinkage stress can be relaxed by the intervening layer 12 ′. Therefore, even when the thermoplastic resin layer 12 and the intervening layer 12 ′ are formed on the base material 11 by coextrusion coating, the stress acting on the base material 11 is not easily generated. The amount will be small.
The intervening layer 12 ′ contains the copolymer F as a main component, preferably a copolymer of ethylene and (meth) acrylic acid, a copolymer of ethylene and (meth) acrylic ester, or ethylene and acetic acid. A copolymer of vinyl as a main component, and particularly preferably, a copolymer of ethylene and (meth) acrylic acid ester or a copolymer of ethylene and vinyl acetate as a main component. Species can be used alone or in combination of two or more. In addition, in this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms.

  The (meth) acrylic acid ester is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms, such as methyl (meth) acrylate, ethyl (meth) acrylate, (meth) Examples thereof include propyl acrylate, butyl (meth) acrylate, and 2-ethylhexyl acrylate. Among these, methyl acrylate, butyl acrylate, ethyl hexyl acrylate, and methyl methacrylate are preferable, and one kind can be used alone, or two or more kinds can be used in combination.

  The total content of (meth) acrylic acid, (meth) acrylic acid ester and vinyl acetate as monomer units in the copolymer F is preferably 3.5 mol% or more and 15 mol% or less, More preferably, it is 4 mol% or more and 14 mol% or less. That is, in the copolymer of ethylene and (meth) acrylic acid, the content of (meth) acrylic acid, in the copolymer of ethylene and (meth) acrylic acid ester, the content of (meth) acrylic acid ester, ethylene and In the copolymer with vinyl acetate, the vinyl acetate content is preferably 3.5 mol% or more and 15 mol% or less, and more preferably 4 mol% or more and 14 mol% or less.

  When the content of (meth) acrylic acid, (meth) acrylic acid ester or vinyl acetate is within the above range, the above-described high adhesive force and curl suppressing effect on the substrate 11 become more remarkable. In addition, when the content of (meth) acrylic acid, (meth) acrylic acid ester and vinyl acetate is less than 3.5 mol%, the adhesive force to the base material 11 and the thermoplastic resin layer 12 may be low, In the case of 15 mol% or more, sufficient cohesive force cannot be obtained, and when the solar cell protective sheet 1 is wound up, there is a possibility that winding deviation occurs.

  Interposition layer 12 'should just contain the said copolymer F as a main component, Specifically, it is preferable to contain the said copolymer F 60 mass% or more, and to contain 80 mass% or more. Is more preferable, and it is particularly preferable to contain 90% by mass or more. Of course, the intervening layer 12 ′ may be composed only of the copolymer F.

  The thickness of the intervening layer 12 ′ is not particularly limited as long as the desired adhesion to the substrate 11 and the preferred embodiment exhibit stress relaxation and do not impair the effects of the present invention. Specifically, the thickness of the intervening layer 12 ′ is preferably 5 μm or more and 150 μm or less, more preferably 10 μm or more and 100 μm or less, and particularly preferably 15 μm or more and 75 μm or less.

(4) Fluororesin Layer As shown in FIG. 3, the solar cell protective sheet 1 according to this embodiment is provided on the surface of the substrate 11 on which the thermoplastic resin layer 12 is not laminated (the lower surface in FIG. 3). The fluororesin layer 13 may be provided. By providing the fluororesin layer 13 in this manner, the weather resistance of the solar cell protective sheet 1 is improved. In addition, when the base material 11 consists of a resin film, in order to improve the adhesiveness with the fluororesin layer 13, the surface by which the fluororesin layer 13 of the said resin film is laminated | stacked has a corona treatment and a plasma treatment. It is preferable that surface treatment (easy adhesion treatment) such as primer treatment is performed.

  The fluororesin layer 13 is not particularly limited as long as it contains fluorine. For example, the fluororesin layer 13 is constituted by a sheet having a fluorine-containing resin (fluorine-containing resin sheet), a coating film formed by applying a paint containing the fluorine-containing resin, or the like. Is done. Among these, from the viewpoint of making the fluororesin layer 13 thinner in order to reduce the weight of the solar cell protective sheet 1, a coating film formed by applying a paint having a fluorine-containing resin is preferable.

  As the fluorine-containing resin sheet, for example, a sheet obtained by processing a resin mainly composed of polyvinyl fluoride (PVF), ethylene chlorotrifluoroethylene (ECTFE), or ethylene tetrafluoroethylene (ETFE) is used. Examples of the resin mainly composed of PVF include E.I. I. “Tedlar” (trade name) manufactured by du Pont de Nemours and Company. Examples of the resin mainly composed of ECTFE include “Halar” (trade name) manufactured by Solvay Solexis. Examples of the resin mainly composed of ETFE include “Fluon” (trade name) manufactured by Asahi Glass Co., Ltd.

  When the fluororesin layer 13 is a fluorine-containing resin sheet, the fluororesin layer 13 is laminated on the base material 11 via an adhesive layer. The layer having adhesiveness is composed of an adhesive having adhesiveness to the substrate 11 and the fluorine-containing resin sheet. Examples of such adhesives include acrylic adhesives, polyurethane adhesives, epoxy adhesives, polyester adhesives, and polyester polyurethane adhesives. These adhesives may be used individually by 1 type, and may be used in combination of 2 or more type.

  On the other hand, when the fluororesin layer 13 is a coating film formed by applying a paint having a fluorine-containing resin, usually, the paint containing the fluorine-containing resin is directly applied to the substrate 11 without using an adhesive layer. By doing so, the fluororesin layer 13 is laminated on the substrate 11.

  The paint containing the fluorine-containing resin is not particularly limited as long as it is dissolved in a solvent or dispersed in water and can be applied.

  The fluorine-containing resin contained in the paint is not particularly limited as long as it does not impair the effects of the present invention and contains fluorine. However, it is usually soluble in a paint solvent (organic solvent or water) and can be crosslinked. Things are used. As the fluorine-containing resin, it is preferable to use a fluoroolefin resin having a crosslinkable functional group. Examples of the crosslinkable functional group include a hydroxyl group, a carboxyl group, an amino group, and a glycidyl group. Examples of the fluoroolefin resin include chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, and pentafluoropropylene.

  Specific examples of the fluoroolefin resin having a crosslinkable functional group include “LUMIFLON” (product name) manufactured by Asahi Glass Co., Ltd., “CEFRAL COAT” (product name) manufactured by Central Glass Co., Ltd., and “FLUONATE” (product manufactured by DIC Corporation). Name) and other polymers based on chlorotrifluoroethylene (CTFE) as a main component, and polymers based on tetrafluoroethylene (TFE) such as “ZEFFLE” (trade name) manufactured by Daikin Industries, Ltd. .

  The paint may contain a crosslinking agent, a crosslinking catalyst, a solvent and the like in addition to the fluorine-containing resin described above. These contents may be appropriately set in consideration of the characteristics and thickness of the coating film.

  The coating film of the fluorine-containing resin is preferably crosslinked with a crosslinking agent in order to improve weather resistance and scratch resistance. The crosslinking agent is not particularly limited as long as the effects of the present invention are not impaired, and metal chelates, silanes, isocyanates, or melamines are preferably used. Assuming that the solar cell protective sheet 1 is used outdoors for a long period of time, aliphatic isocyanates are preferable as the crosslinking agent from the viewpoint of weather resistance.

  As a method for applying the coating material to the substrate 11, a known method is used. For example, the coating is performed so that the obtained fluororesin layer 13 has a desired thickness by a bar coating method, a die coating method, a gravure coating method, or the like. do it.

  The thickness of the fluororesin layer 13 is set in consideration of weather resistance, chemical resistance, weight reduction, and the like, and is preferably 5 μm or more and 50 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

(5) Vapor deposition layer, metal sheet As shown in FIG. 4, the protective sheet 1 for solar cells according to this embodiment has a base 11 on the surface of the base 11 on which the thermoplastic resin layer 12 is not laminated. A vapor deposition layer 14 may be provided between the metal sheet 16 and the fluororesin layer 13, or a metal sheet 16 may be laminated via an adhesive layer 15 as shown in FIG. The fluororesin layer 13 described above may be provided on the lower surface in FIGS. Thus, by providing the vapor deposition layer 14 or the metal sheet 16, the moisture-proof property and weather resistance of the protection sheet 1 for solar cells can be improved. In the present embodiment, the “metal sheet” means a sheet-like member made of a metal-based material (that is, a material containing a metal element).

  In addition, when the base material 11 consists of a resin film, in order to improve the adhesiveness with the vapor deposition layer 14 or the contact bonding layer 15, the surface by which the vapor deposition layer 14 or the contact bonding layer 15 of the said resin film is laminated | stacked is a corona. Surface treatment such as treatment, plasma treatment, and primer treatment is preferably performed.

  The vapor deposition layer 14 is comprised from inorganic materials, such as a metal or a semimetal, or an oxide, nitride, silicide, etc. of a metal or a semimetal, By being comprised from such material, the base material 11 (protective sheet for solar cells) It is possible to impart moisture resistance (water vapor barrier property) and weather resistance to 1).

  Examples of the vapor deposition method for forming the vapor deposition layer 14 include chemical vapor deposition such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition, or vacuum vapor deposition, sputtering, and ion plating. A physical vapor phase method such as a method is used. Among these methods, the sputtering method is preferable in consideration of operability and controllability of the layer thickness.

  Examples of the metal used as the raw material of the vapor deposition layer 14 include aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium rim (Na), titanium (Ti), and lead. (Pb), zirconium (Zr), yttrium (Y) and the like. Examples of the semimetal include silicon (Si) and boron (B). Examples of these metal or metalloid oxides, nitrides, and oxynitrides include aluminum oxide, tin oxide, silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxynitride.

  The vapor deposition layer 14 may be made of one kind of inorganic material or may be made of a plurality of kinds of inorganic materials. When the vapor deposition layer 14 is made of a plurality of types of inorganic materials, it may be a vapor deposition layer having a laminated structure in which the layers made of the respective inorganic materials are sequentially vapor deposited, or may be a vapor deposition layer in which a plurality of types of inorganic materials are vapor deposited simultaneously. May be.

  The thickness of the vapor deposition layer 14 is appropriately set in consideration of the water vapor barrier property, and is changed depending on the type of inorganic material used, vapor deposition density, and the like. Usually, the thickness of the vapor deposition layer 14 is preferably 5 nm or more and 200 nm or less, and particularly preferably 10 nm or more and 100 nm or less.

  On the other hand, the metal sheet 16 can also provide moisture resistance (water vapor barrier property) and weather resistance to the base material 11 (protective sheet 1 for solar cells), similarly to the vapor deposition layer 14. The material of the metal sheet 16 is not particularly limited as long as it has such a function, and examples thereof include metals such as aluminum and aluminum alloys such as aluminum-iron alloys.

  The thickness of the metal sheet 16 is not particularly limited as long as the effects of the present invention are not impaired, but from the viewpoint of low pinhole occurrence frequency, high mechanical strength, high water vapor barrier properties, and weight reduction, etc. It is preferably 5 μm or more and 100 μm or less, and particularly preferably 10 μm or more and 50 μm or less.

  The adhesive layer 15 is composed of an adhesive having adhesiveness to the base material 11 and the metal sheet 16. As the adhesive constituting the adhesive layer 15, for example, an acrylic adhesive, a polyurethane adhesive, an epoxy adhesive, a polyester adhesive, a polyester polyurethane adhesive, or the like is used. These adhesives may be used individually by 1 type, and may be used in combination of 2 or more type.

  The thickness of the adhesive layer 15 is not particularly limited as long as the effects of the present invention are not impaired. Usually, the thickness is preferably 1 μm or more and 20 μm or less, and particularly preferably 3 μm or more and 10 μm or less.

  In addition, in the above embodiment, although the solar cell protective sheet 1 in which the thermoplastic resin layer 12 was laminated on one surface of the base material 11 was illustrated, the solar cell protective sheet of the present invention is not limited thereto. The thermoplastic resin layer may also be laminated on the other surface of the substrate 11 (the surface opposite to the one surface).

2. Method for Producing Solar Cell Protective Sheet To produce solar cell protective sheet 1 according to this embodiment (as an example, solar cell protective sheet 1 shown in FIG. 1), the thermoplastic resin constituting thermoplastic resin layer 12 is produced. It is preferable to form the thermoplastic resin layer 12 on the base material 11 by extrusion coating the resin composition on at least one surface of the base material 11. According to such an extrusion coating method, the protection sheet 1 for solar cells can be manufactured with high productivity and at low cost. Moreover, since it is not necessary to separately provide an adhesive layer for adhering the solar cell protective sheet 1 to the sealing material of the solar cell module, it is possible to prevent deterioration over time due to decomposition of the adhesive or the like.

  Specifically, using a T-die extruder or the like, the thermoplastic resin composition containing the thermoplastic resins A and B is melted and kneaded, and the base material 11 is moved at a constant speed while the base material 11 is moved. The thermoplastic resin layer 12 is formed on the base material 11 by extruding and laminating the molten thermoplastic resin composition on one surface of 11 to obtain the protective sheet 1 for solar cells.

  As shown in FIG. 2, in order to laminate the laminate of the intervening layer 12 ′ and the thermoplastic resin layer 12 on one surface of the base material 11, first, on one surface of the base material 11 by the above-described extrusion coating. A layer made of an adhesive composition that gives the intervening layer 12 ′ is laminated to form the intervening layer 12 ′, and the above thermoplastic resin composition is extruded onto the exposed surface opposite to the substrate 11 side. Thus, the thermoplastic resin layer 12 may be formed on the intervening layer 12 ′. Alternatively, the adhesive composition and the thermoplastic resin composition are extruded together from two parallel slits (at this time, the discharge port of the adhesive composition is disposed closer to the substrate 11. ) And layers (intervening layer 12 ′ and thermoplastic resin layer 12) made of each composition may be simultaneously formed on the substrate 11.

  This co-extrusion coating has the advantage of the production process that the solar cell protective sheet 1 can be obtained in a single lamination process, and immediately after co-extrusion, the adhesive composition and the thermoplastic that give the intervening layer 12 '. Since the thermoplastic resin composition that provides the resin layer 12 is in contact with the thermoplastic resin composition in a molten state, there is an advantage that the interaction easily occurs and the adhesion between the obtained intervening layer 12 ′ and the thermoplastic resin layer 12 is increased. Further, if the constituent material of the adhesive composition is appropriately selected and the intervening layer 12 ′ has elasticity, even if the thermoplastic resin layer 12 contracts when cooled from the heated and melted state, the intervening layer 12 The shrinkage stress can be relieved by '. Therefore, there is an advantage that the protective sheet 1 for a solar cell can be easily obtained because the stress acting from the thermoplastic resin layer 12 toward the base material 11 hardly occurs and the curl amount is small. Therefore, when manufacturing the protection sheet 1 for solar cells provided with the structure shown by FIG. 2, manufacturing by coextrusion coating is preferable.

  As shown in FIGS. 3 to 5, when another layer is formed on the substrate 11, the thermoplastic resin layer 12 and the surface of the substrate 11 on the side where the other layer is not formed are provided. What is necessary is just to form intervening layer 12 '.

  The temperature at which the resin composition constituting the thermoplastic resin layer 12 is melted and the temperature at which the adhesive composition constituting the intervening layer 12 ′ used is melted as required are such that these compositions are in a molten state and are melted. The base material 11 is not deformed by the heat of these compositions in a state, preferably 80 ° C. or higher and 350 ° C. or lower, and particularly preferably 150 ° C. or higher and 300 ° C. or lower. In addition, when the resin composition and / or the adhesive composition is likely to be altered, it is preferable to lower the upper limit of the temperature so as to minimize the influence of the alteration.

  Moreover, the discharge amount from the T-die extruder of the resin composition which forms the thermoplastic resin layer 12 is suitably adjusted according to the thickness of the target thermoplastic resin layer 12 and the moving speed of the base material 11.

  The base material 11 is transported in the longitudinal direction at a constant speed by, for example, a roll-to-roll method, and the transport speed is equal to the discharge amount of the resin material forming the thermoplastic resin layer 12 from the T-die extruder. It is adjusted accordingly.

  According to the extrusion coating method as described above, the resin composition for forming the thermoplastic resin layer 12 melted from the T-die extruder is extruded and laminated on one surface of the substrate 11. The thermoplastic resin layer 12 can be firmly bonded, and the solar cell protective sheet 1 can be manufactured with high productivity.

3. Solar Cell Module FIG. 6 is a schematic cross-sectional view of a solar cell module according to an embodiment of the present invention. The solar cell module 10 according to the present embodiment includes a plurality of solar cells 2 made of crystalline silicon, amorphous silicon, or the like, which are photoelectric conversion elements, and tab wires 21 that electrically connect each of the plurality of solar cells 2 ( In FIG. 6, one of the tab wires is provided with a reference numeral.), A sealing material 3 made of an electrical insulator that seals at least one of the solar cells 2 and the tab wire 21, and a sealing material 3 for the solar cell as a back surface protection sheet (back sheet) laminated on the glass plate 4 laminated on the front surface (upper surface in FIG. 6) and the back surface (lower surface in FIG. 6) of the sealing material 3 It consists of a sheet 1. In addition, in order to output the photovoltaic power generated in the solar battery cell 2 to the outside, a part of the tab wire 21 may be exposed to the outside without being sealed. Alternatively, the tab wire 21 is entirely sealed, but the wiring connected to one terminal may be connected to the other terminal of the terminal block exposed to the outside without being sealed.

  In addition, the protective sheet 1 for solar cells is laminated | stacked on the sealing material 3 so that the thermoplastic resin layer 12 may become the sealing material 3 side, and it adheres with respect to the sealing material 3 by this thermoplastic resin layer 12 Power is high. Moreover, since the solar cell protective sheet 1 in the present embodiment has a small amount of curl, warping of the obtained solar cell module 10 is suppressed. Therefore, it is possible to prevent problems caused when the solar cell module 10 is installed or damage of the solar cell module 10 due to warpage of the solar cell module 10.

  The material of the sealing material 3 is preferably an olefin resin, and for example, the material exemplified as the olefin resin constituting the thermoplastic resin A contained in the thermoplastic resin layer 12 is preferable. Among these resins, an ethylene-vinyl acetate copolymer (EVA) is particularly preferable from the viewpoints of high gas barrier properties against oxygen and the like, easy crosslinking, and availability. When the material of the sealing material 3 is an olefin resin, the affinity with the thermoplastic resin layer 12 containing the thermoplastic resin A, which is an olefin resin, increases, and the thermoplastic resin layer 12 and the sealing material 3 The adhesive strength of becomes higher.

  The method for manufacturing the solar cell module 10 is not particularly limited. For example, the solar cell 2 and the tab wire 21 are sandwiched between two sheets constituting the sealing material 3, and the solar cell module 10 is exposed to one of the exposed surfaces of the sheet. The solar cell module 10 can be manufactured by installing the glass plate 4 on the battery protective sheet 1 and the other exposed surface, and pressing and integrating them while heating. At this time, the protective sheet 1 for solar cells is joined to the sealing material 3 by thermal fusion of the thermoplastic resin layer 12 and the sealing material 3.

  In addition, as shown in FIG. 7, it can replace with the glass plate 4 and can also use the protection sheet 1 for solar cells as a surface protection sheet (front sheet). In this case, if a flexible substrate is used for the solar battery cell, a solar battery module having flexibility can be obtained. Thus, by making the solar cell module flexible, it becomes possible to mass-produce by roll-to-roll. In addition, since the flexible solar cell module can be fitted to an object having an arched or parabolic wall surface, it can be installed on a dome-shaped building or a soundproof wall of an expressway. .

  Or the thermoplastic resin layer 12 in the protection sheet 1 for solar cells may have a function of a sealing material. In this case, the solar cell module 10 includes a plurality of solar cells 2, tab wires 21 that electrically connect the plurality of solar cells, the plurality of solar cells 2, and at least one tab wire 21. The enclosing sealing material 3 and the two protective members laminated on each of the main surfaces of the encapsulating material 3 are provided. At least one of these protective members is composed of the solar cell protective sheet 1, and the thermoplastic resin layer 12 provided in the solar cell protective sheet 1 constitutes part or all of the sealing material 3. When the thermoplastic resin layer 12 forms part of the sealing material 3, the solar cell protective sheet 1 is bonded to the sealing material 3 by thermal fusion. When the thermoplastic resin layer 12 forms the entire sealing material 3, the glass plate 4 (configuration in FIG. 6) corresponding to the other of the above protective members or other solar cell protective sheet 1 (FIG. 7). The structure is joined by thermal fusion.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
One surface of a polyethylene terephthalate film (Lumirror X10S manufactured by Toray Industries Inc., thickness 125 μm) as a substrate is subjected to corona treatment (output 2000 W), and a T-die extruder (cylinder temperature: 230 to 280 ° C., T-die temperature: 300). ), 70 parts by mass of a thermoplastic resin A made of polyethylene having a density of 900 kg / m ³ (Evolue-P SP00100 made by Prime Polymer, melting peak temperature 92 ° C.), and polyethylene having a density of 940 kg / m ³ (Prime Polymer Co., Ltd.) 30 parts by mass of thermoplastic resin B made of Evolue-H SP4005, melting peak temperature of 127 ° C., and 10 parts by mass of titanium dioxide so as to have a thickness of 100 μm Extrusion coating on the corona-treated surface of the above polyester film Ring to form a thermoplastic resin layer to obtain a protective sheet for a solar cell of the configuration shown in FIG. In addition, said density was measured based on Test Example 2 mentioned later (hereinafter the same).

[Example 2]
In Example 1, the content of the thermoplastic resin layer A was changed to 50 parts by mass instead of 70 parts by mass, and the content of the thermoplastic resin layer B was changed to 50 parts by mass instead of 30 parts by mass. Except having prepared, operation similar to Example 1 was performed and the solar cell protective sheet of the structure shown in FIG. 1 was obtained.

Example 3
In Example 1, the thermoplastic resin layer A content was changed to 90 parts by mass instead of 70 parts by mass, and the thermoplastic resin layer B content was changed to 10 parts by mass instead of 30 parts by mass. Except having prepared, operation similar to Example 1 was performed and the solar cell protective sheet of the structure shown in FIG. 1 was obtained.

Example 4
In Example 1, the type of the resin constituting the thermoplastic resin layer B was changed to polyethylene having a density of 963 kg / m ³ (Nippon Polyethylene Co., Ltd., Novatec HD HF560, melting peak temperature 134 ° C.) and the thermoplastic resin composition. Except that was prepared, the same operation as in Example 1 was performed to obtain a solar cell protective sheet having the configuration shown in FIG.

Example 5
In Example 1, the type of the resin constituting the thermoplastic resin layer B is changed to polyethylene having a density of 922 kg / m ³ (Nippon Polyethylene Co., Ltd., Novatec LL UE320, melting peak temperature 122 ° C.), and a thermoplastic resin composition is obtained. Except that was prepared, the same operation as in Example 1 was performed to obtain a solar cell protective sheet having the configuration shown in FIG.

Example 6
One side of a polyester film (X10S manufactured by Toray Industries Inc., thickness 125 μm) as a substrate is subjected to corona treatment (output 2000 W), and a T-die film forming machine (cylinder temperature: 230 ° C. or higher and 280 ° C. or lower, T die temperature: 300 ° C), an adhesive composition composed of an ethylene-butyl acrylate copolymer (Lotryl17BA07 manufactured by Arkema) and a polyethylene having a density of 900 kg / m ³ (Evolue-P SP00100 manufactured by Prime Polymer, melting peak temperature 92 ° C) 70 parts by mass of thermoplastic resin A and 30 parts by mass of thermoplastic resin B consisting of polyethylene (Prime Polymer, Evolue-H SP4005, melting peak temperature 127 ° C.) having a density of 940 kg / m ³ , and titanium oxide 10 parts by mass of a thermoplastic resin composition The discharge port of the above-mentioned adhesive composition by coextrusion coating with two 2 layer arranged so that proximal to the substrate side was laminated to the corona treated surface of the polyester film. As a result, a laminate composed of an intervening layer having a thickness of 20 μm and a thermoplastic resin layer having a thickness of 100 μm is formed on the substrate so that the intervening layer is in contact with the substrate, and the solar cell protection having the configuration shown in FIG. A sheet was obtained.

[Comparative Example 1]
In Example 1, the content of the thermoplastic resin layer A was changed to 100 parts by mass instead of 70 parts by mass, and the thermoplastic resin composition was prepared without containing the thermoplastic resin layer B. The same operation was performed to obtain a solar cell protective sheet having the configuration shown in FIG.

[Comparative Example 2]
In Example 1, the content of the thermoplastic resin layer B was changed to 100 parts by mass instead of 30 parts by mass, and the thermoplastic resin composition was prepared without containing the thermoplastic resin layer A. The same operation was performed to obtain a solar cell protective sheet having the configuration shown in FIG.

[Test Example 1] <Melting peak temperature measurement>
About the thermoplastic resin composition which comprises the thermoplastic resin layer in an Example and a comparative example, and the thermoplastic resins A and B contained in the said composition, it is a differential scanning calorimeter (the product made from a TA instrument company, model number) : Q2000), the melting peak temperature was determined based on JIS K7121 (ISO 3146).
-Condition adjustment of test piece It heated at 10 degreeC / min from 0 degreeC to 200 degreeC, and kept at 200 degreeC for 10 minutes, Then, it cooled at 10 degreeC / minute to 0 degreeC.
-Differential scanning calorimetry It heated at 10 degreeC / min from 0 degreeC to 200 degreeC, and drawn the DSC curve. The melting peak temperature (° C.) was determined from the obtained DSC curve. The results are shown in Table 1.

[Test Example 2] <Density measurement>
About the olefin resin which comprises the thermoplastic resin layer in an Example and a comparative example, the density (kg / m < ³ >) was measured according to JISK7112. When measuring a blend of two or more kinds of resins, after kneading at 210 ° C. with a biaxial kneader (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name: Labo Plast Mill) and quenching in a water bath Measurements were again made on the pellets processed again. The results are shown in Table 1.

[Test Example 3] <Storage elastic modulus measurement>
The thermoplastic resin composition produced in the example or comparative example was extrusion coated on the release surface of a release sheet (manufactured by Lintec, product name: SP-PET38T103-1, thickness 38 μm), and the film thickness was 100 μm. A laminate in which a thermoplastic resin layer was laminated on a release sheet was obtained.
For a thermoplastic resin layer having a thickness of 100 mm formed by peeling a release sheet from the laminate, a dynamic viscoelasticity measuring device (manufactured by A & D Corporation, RHEOVIBRON) according to ISO 6721-4 (JIS K7244-4). DDV-01FP) was used to determine the storage modulus at mode: tensile, frequency: 1 Hz, temperature: 80 ° C. The measurement results are shown in Table 1.

[Test Example 4] <Measurement of curl amount>
The protective sheet for a solar cell produced in the example or the comparative example was cut into a 300 mm × 300 mm square, placed on a horizontal table, and the vertical distance (mm) from the table surfaces at the four corners was measured. The average value of each distance of the obtained four places was calculated, and this was taken as the curl amount (mm). The results are shown in Table 1.

[Test Example 5] <Heat resistance evaluation>
A tab wire having a width of 6 mm and a thickness of 150 μm is placed on an ethylene-vinyl acetate copolymer sealing material having a thickness of 400 μm provided on a glass plate (manufactured by Sunvic, Ultra Pearl). After the protective sheet produced in the example or comparative example was overlaid on the placed sealing material, and then the whole (glass / sealing material / tab wire / protective sheet) was degassed under reduced pressure, A test sample was obtained by pressure bonding at a pressure of 1 atm and a temperature of 135 ° C. for 6 minutes.

The obtained test sample was heated in an oven at 120 ° C. for 24 hours, imitating a heat resistance evaluation test. After completion of the simulation heat resistance evaluation test, the test sample was visually observed from the glass surface, and the presence or absence of occurrence of line traces was evaluated according to the following evaluation criteria. The case where it was determined as “x” was regarded as unacceptable.
○: Tab line is not visible,
Δ: A part of the edge portion of the tab line can be confirmed, and ×: The edge portion of the tab line can be confirmed entirely.
The evaluation results are shown in Table 1.

  As can be seen from Table 1, the solar cell protective sheet of the example satisfying the conditions of the present invention has a small curl amount, and even when a heat resistance evaluation is performed on a test sample manufactured using such a sheet, the line trace becomes apparent. The occurrence of was suppressed.

  The solar cell protective sheet according to the present invention is suitably used, for example, as a back sheet or a front sheet of a solar cell module.

DESCRIPTION OF SYMBOLS 1 ... Protective sheet for solar cells 11 ... Base material 12 ... Thermoplastic resin layer 12 '... Intervening layer 13 ... Fluorine resin layer 14 ... Deposition layer 15 ... Adhesive layer 16 ... Metal sheet 2 ... Solar cell 21 ... Tab wire 3 ... Sealing material 4 ... Glass plate 10 ... Solar cell module

Claims (15)

A solar cell protective sheet comprising a substrate and a thermoplastic resin layer laminated on at least one surface of the substrate,
The thermoplastic resin layer is composed of a thermoplastic resin composition containing a thermoplastic resin A and a thermoplastic resin B,
The thermoplastic resin A is composed of an olefin resin having a density of less than 920 kg / m ³ ,
The thermoplastic resin B has a higher density than the thermoplastic resin A and is made of a resin compatible with the thermoplastic resin A,
The thermoplastic resin composition has a density of 875 kg / m ³ or more and 920 kg / m ³ or less, and a melting peak temperature of 95 ° C. or more. A solar cell protective sheet comprising a substrate and a thermoplastic resin layer laminated on at least one surface of the substrate,
The thermoplastic resin composition for providing the thermoplastic resin layer includes a thermoplastic resin A and a thermoplastic resin B,
The thermoplastic resin A is composed of an olefin resin having a density of less than 920 kg / m ³ ,
The thermoplastic resin B has a higher density than the thermoplastic resin A and is made of a resin compatible with the thermoplastic resin A,
The thermoplastic resin composition has a density of 875 kg / m ³ or more and 920 kg / m ³ or less and a storage elastic modulus at 80 ° C. of 3 MPa or more.   The protective sheet for solar cells according to claim 2, wherein the thermoplastic resin composition has a melting peak temperature of 95 ° C. or higher.   The said thermoplastic resin A is a protective sheet for solar cells as described in any one of Claim 1 to 3 which contains ethylene 60 mass% or more and 100 mass% or less as a monomer unit.   The solar cell protective sheet according to any one of claims 1 to 4, wherein a melting peak temperature of the thermoplastic resin B is 95 ° C or higher.   The said thermoplastic resin composition is a protection sheet for solar cells as described in any one of Claim 1 to 5 containing a coloring material.   The said thermoplastic resin layer is a protection sheet for solar cells as described in any one of Claim 1 to 6 in which the said thermoplastic resin composition is laminated | stacked on the one surface of the said base material by extrusion coating.   The protective sheet for solar cells as described in any one of Claim 1 to 7 provided with the intervening layer which consists of an adhesive composition which has adhesiveness with respect to these between the said thermoplastic resin layer and the said base material.   The said adhesive composition is based on the copolymer of ethylene and at least 1 sort (s) chosen from the group which consists of (meth) acrylic acid, (meth) acrylic acid ester, and vinyl acetate as a main component. Protection sheet for solar cells.   The thermoplastic resin layer and the intervening layer are formed by coextrusion coating of the thermoplastic resin composition and the adhesive composition on the substrate. The protective sheet for solar cells as described.   The said thermoplastic resin layer is a layer adhere | attached with the sealing material which comprises a solar cell module, The protective sheet for solar cells as described in any one of Claim 1 to 10 characterized by the above-mentioned. A method for producing a protective sheet for a solar cell, comprising: a base material; and a thermoplastic resin layer laminated on at least one surface of the base material,
7. The solar cell, wherein the thermoplastic resin layer is formed by extrusion coating the thermoplastic resin composition according to any one of claims 1 to 6 on at least one surface of the substrate. Method of manufacturing protective sheet. A base material, a thermoplastic resin layer, and an adhesive composition having adhesiveness to the base material and the thermoplastic resin layer are laminated between one surface of the base material and one surface of the plastic resin layer. A method for producing a protective sheet for a solar cell comprising an interposed layer,
The thermoplastic resin composition according to any one of claims 1 to 6 and the adhesive composition are coextrusion coated on at least one surface of the substrate, and the intervening layer and the heat are coated. A method for producing a protective sheet for a solar cell, comprising forming a plastic resin layer.   The adhesive composition is mainly composed of a copolymer of ethylene and at least one selected from the group consisting of (meth) acrylic acid, (meth) acrylic acid ester and vinyl acetate. Item 14. A method for producing a solar cell protective sheet according to Item 13. A plurality of solar cells, an electrical wiring for electrically connecting the plurality of solar cells, a sealing material enclosing the plurality of solar cells and at least one of the electrical wirings, and a main of the sealing material A solar cell module comprising two protective members stacked on each of the surfaces,
At least one of the protective members is composed of the protective sheet for solar cells described in any one of claims 1 to 10,
The said thermoplastic resin layer with which the said protection sheet for solar cells is provided makes a part or all of the said sealing material, The solar cell module characterized by the above-mentioned.

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