JP2013026340A - Base film for solar cell, back sheet for solar cell, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base film for solar cell having a weather resistance polyester support, and including an easy adhesion layer exhibiting excellent adhesion of the weather resistance polyester support and a functional layer through the heat and humidity before and after aging.SOLUTION: The base film 1 for solar cell includes a polyester support 2 having a carboxyl group content of 20 equivalent/t or less, and a polymer layer 3 arranged on at least one surface of the polyester support and containing a binder and a structure derived from a crosslinking agent. The binder contains at least one kind of acrylate resin and polyester resin, and polyolefin resin, and the crosslinking agent is at least one kind of compound out of a compound having an oxazoline group and a compound having a carbodiimide group.

Description

  The present invention relates to a base film for solar cell, a back sheet for solar cell, and a solar cell module. It is related with the base film for back sheets which provided the easy-adhesion layer with especially high adhesive performance with a functional application layer on the polyester support body with high weather resistance.

  Solar cells are a power generation system that emits no carbon dioxide during power generation and has a low environmental load, and have been rapidly spreading in recent years. The solar cell module is generally between a front base material that is disposed on the front surface side on which sunlight is incident and a so-called back sheet that is disposed on the opposite side (back surface side) to the front surface side on which sunlight is incident. In addition, the solar battery element has a structure in which solar cells sealed with a sealing material are sandwiched, and between the front base material and the solar battery cell and between the solar battery cell and the back sheet, Each is sealed with EVA (ethylene-vinyl acetate) resin or the like.

  The back sheet constituting the solar cell module has a function of preventing moisture from entering from the back surface of the solar cell module, and conventionally glass or fluororesin has been used, but in recent years from the viewpoint of cost etc. Polyester has been applied. And since the back sheet not only has a function of suppressing the permeation of moisture, but also requires durability (weather resistance and light resistance), light reflectivity, electrical insulation, etc., for example, the polymer support is weather resistant. A functional layer such as a layer for enhancing the property and a colored layer to which a white pigment such as titanium oxide is added to give reflection performance is laminated on the polymer support. As a method for producing such a laminated type back sheet, it is known that a method of laminating by coating is preferable from the viewpoint of cost etc. in addition to a method of laminating a functional sheet with an adhesive. It has been required to improve the adhesion between the functional layer and the polymer support so that the functional layer does not peel off.

  As a method for improving the adhesion between such a functional layer and a polymer support, a method of providing an easy adhesion layer between these layers is known. For example, Patent Document 1 and Patent Document 2 describe a polyester film having an easy-adhesion layer mainly composed of a polyester resin as a magnetic tape application and a packaging film application. In patent document 1, even if it is an easily bonding layer of a flat surface by apply | coating the application layer which added the bridge | crosslinking acrylic particle to the polyester resin aqueous dispersion as an easily bonding layer on a biaxially stretched polyester film, it adhere | attaches. It is described that an easily adhesive film having excellent properties can be obtained. Patent Document 2 discloses adhesion and high-temperature hot water by applying an easy-adhesion layer using a crosslinking agent such as carbodiimide or oxazoline compound on a film using a polyester resin having a specific acid value or glass transition temperature. It is described that an easily adhesive film excellent in resistance can be provided.

  On the other hand, in recent years, it has been demanded to use a solar cell module in a high-temperature and high-humidity environment, and it is possible to maintain the adhesiveness between the functional layer and the polymer support even with the passage of time in a humid-heat environment. It has been demanded.

JP 2007-254653 A JP 2009-113240 A

  Under these circumstances, the present inventors improve the weather resistance of the polyester support itself by using a low AV polyester in which the terminal carboxyl group content (hereinafter also referred to as AV value) of the polyester support is low. The knowledge that it can be obtained.

  However, when the inventors try to use the film with an easy-adhesion layer described in Patent Documents 1 and 2 as a base film for a solar cell with an easy-adhesion layer of a solar cell backsheet, It turned out that it was not enough for the adhesive improvement of low AV value polyester with high weather resistance and a functional coating layer (For example, a weathering coating layer; a silicone type polymer layer or a fluorine-type polymer layer).

  The present invention has been made in order to solve the above problems. The problem to be solved by the present invention is a substrate film for solar cells that has a weather-resistant polyester support and has an easy-adhesion layer excellent in adhesion between the weather-resistant polyester support and the functional layer before and after wet heat aging. Is to provide.

  As a result of intensive studies by the present inventors to solve the above problems, a polymer layer having at least two binders in a specific combination and a specific cross-linking agent is provided on a polyester support having a specific AV value. Then, it came to discover that the said subject could be solved.

That is, the present invention which is a specific means for solving the above-described problems is as follows.
[1] A polyester support having a carboxyl group content of 20 equivalent / t or less and a polymer layer disposed on at least one surface of the polyester support and including a structure derived from a binder and a crosslinking agent, A solar cell characterized in that it comprises at least one of an acrylic resin and a polyester resin and a polyolefin resin, and the crosslinking agent is at least one compound selected from a compound having an oxazoline group and a compound having a carbodiimide group. Base film.
[2] In the solar cell base material film according to [1], the polymer layer is preferably formed by applying a coating solution containing the binder and the crosslinking agent.
[3] In the solar cell base film according to [1] or [2], the polyolefin resin is preferably an ionomer type.
[4] In the solar cell base material film according to any one of [1] to [3], the binder preferably includes an acrylic resin and a polyolefin resin.
[5] In the solar cell base material film according to any one of [1] to [4], the polyester support preferably has a thickness of 60 to 300 μm.
[6] In the solar cell base material film according to any one of [1] to [5], the thermal contraction rate of the polyester support is preferably 1% or less.
[7] A white sheet is bonded to the surface of the substrate film for solar cells according to any one of [1] to [6] opposite to the surface on which the polymer layer is provided. A solar cell backsheet characterized by
[8] On the surface on which the polymer layer of the solar cell base material film according to any one of [1] to [6] is disposed, or the solar cell backsheet according to [7]. A back sheet for solar cells, comprising a functional layer on the surface on which the polymer layer is disposed.
[9] In the solar cell backsheet according to [8], the functional layer is preferably a functional coating layer formed by coating.
[10] A solar cell module comprising the solar cell backsheet according to any one of [7] to [9].

  According to the present invention, there is provided a substrate film for a solar cell that has a weather-resistant polyester support and has an easy-adhesion layer excellent in adhesion between the weather-resistant polyester support and the functional layer before and after wet heat aging. Can do. Further, according to the present invention, there is provided a solar cell backsheet provided with the solar cell base film, and a solar cell module exhibiting stable power generation performance over a long period provided with the solar cell backsheet. can do.

It is the schematic which shows an example of the cross section of the base film for solar cells of this invention. It is the schematic which shows another example of the cross section of the base film for solar cells of this invention. It is the schematic which shows an example of the cross section of the solar cell backsheet of this invention using the base film for solar cells of this invention. It is the schematic which shows another example of the cross section of the solar cell backsheet of this invention using the base film for solar cells of this invention. It is the schematic which shows another example of the cross section of the solar cell backsheet of this invention using the base film for solar cells of this invention. It is the schematic which shows another example of the cross section of the solar cell backsheet of this invention using the base film for solar cells of this invention. It is the schematic which shows an example of the cross section of the solar cell module using the solar cell backsheet of this invention.

Hereinafter, the base film for solar cells, the back sheet for solar cells, and the solar cell module of the present invention will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Substrate film for solar cells]
The base film for solar cell of the present invention is a polymer comprising a polyester support having a carboxyl group content of 20 equivalent / t or less and a structure derived from a binder and a crosslinking agent, disposed on at least one surface of the polyester support. And the binder includes at least one of an acrylic resin and a polyester resin and a polyolefin resin, and the crosslinking agent is at least one compound among a compound having an oxazoline group and a compound having a carbodiimide group. It is characterized by that.
In the present specification, the polymer layer is also referred to as an easy adhesion layer.

  First, the structure of the base film for solar cells of this invention is shown in FIG. The base film 1 for solar cells of this invention has the polyester support body 2 and the easily bonding layer (polymer layer) 3 arrange | positioned on the at least one surface of this polyester support body. The easy-adhesion layer may be provided as easy-adhesion layers 3 and 3 ′ on both sides of the polyester support 1 as shown in FIG. 2.

1. Polyester support The base film for a solar cell of the present invention uses a polyester support having a carboxyl group content of 20 equivalent / t (synonymous with eq / t or eq / ton; hereinafter the same). When the carboxyl group content is 20 equivalent / t or less, the retention rate of hydrolysis resistance of the polyester support itself is high, and a decrease in strength of the polyester support itself over time with wet heat can be suppressed to a low level. As a result, adhesion with other functional layers can be maintained even after aging in a moist heat environment.

In the present invention, the carboxyl group content in the polyester is preferably 18 equivalent / t or less, more preferably 15 equivalent / t or less. The lower limit of the carboxyl group content is preferably 2 equivalents / t in terms of maintaining adhesion between the layer formed on the polyester (for example, a colored layer).
The carboxyl group content in the polyester can be adjusted by the polymerization catalyst species and the film forming conditions (film forming temperature and time).
The carboxyl group content (AV) was determined by completely dissolving the target polyester support in a mixed solution of benzyl alcohol / chloroform (= 2/3; volume ratio), using phenol red as an indicator, and using a standard solution (0.025N KOH -Methanol mixed solution), and a value calculated from the appropriate amount.

  The polyester used as the polyester support is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate and the like. Of these, polyethylene terephthalate or polyethylene-2,6-naphthalate is particularly preferred from the viewpoint of the balance between mechanical properties and cost, and the polymer sheet of the present invention is more particularly preferably a polyethylene terephthalate support. preferable.

  The polyester may be a homopolymer or a copolymer. Further, the polyester may be blended with a small amount of another type of resin such as polyimide.

  When the polyester in the present invention is polymerized, it is preferable to use an Sb-based, Ge-based, or Ti-based compound as a catalyst from the viewpoint of keeping the carboxyl group content within a predetermined range, and among these, a Ti-based compound is particularly preferable. In the case of using a Ti-based compound, an embodiment in which polymerization is performed by using the Ti-based compound as a catalyst in a range of 1 ppm to 30 ppm, more preferably 3 ppm to 15 ppm is preferable. When the proportion of the Ti-based compound is within the above range, the terminal carboxyl group can be adjusted to the following range, and the hydrolysis resistance of the resin film substrate can be kept low.

  For the synthesis of polyester using a Ti-based compound, for example, Japanese Patent Publication No. 8-301198, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 397756, Japanese Patent No. 39622626, Japanese Patent No. 39786666 No. 3, Japanese Patent No. 3,996,871, Japanese Patent No. 40000867, Japanese Patent No. 4053837, Japanese Patent No. 4127119, Japanese Patent No. 4134710, Japanese Patent No. 4159154, Japanese Patent No. 4269704, Japanese Patent No. 4135538, etc. it can.

The polyester in the present invention is preferably solid-phase polymerized after polymerization. Thereby, a preferable carboxyl group content can be achieved. Solid-phase polymerization may be a continuous method (a method in which a tower is filled with a resin, which is slowly heated for a predetermined time and then sent out), or a batch method (a resin is charged into a container). , A method of heating for a predetermined time). Specifically, for solid phase polymerization, Japanese Patent No. 2621563, Japanese Patent No. 3121876, Japanese Patent No. 3136774, Japanese Patent No. 3603585, Japanese Patent No. 3616522, Japanese Patent No. 3617340, Japanese Patent No. 3680523, Japanese Patent No. 3717392 are disclosed. The methods described in Japanese Patent Nos. 4167159 and the like can be applied.
The temperature of the solid phase polymerization is preferably 170 ° C. or higher and 240 ° C. or lower, more preferably 180 ° C. or higher and 230 ° C. or lower, and further preferably 190 ° C. or higher and 220 ° C. or lower. The solid phase polymerization time is preferably 5 hours to 100 hours, more preferably 10 hours to 75 hours, and still more preferably 15 hours to 50 hours. The solid phase polymerization is preferably performed in a vacuum or in a nitrogen atmosphere.

For example, after the polyester support is melt-extruded in the form of a film, the polyester support is cooled and solidified with a casting drum to form an unstretched film, and this unstretched film is 1 in the longitudinal direction at Tg to (Tg + 60) ° C. It is a biaxially stretched film that has been stretched so that the total magnification becomes 3 to 6 times twice or more, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C. Is preferred.
Furthermore, what was heat-processed for 1 to 60 second at 180-230 degreeC as needed may be used.

  As for the thickness of the said polyester support body, about 60-300 micrometers is preferable. When the thickness is 60 μm or more, the mechanical strength is good, and when it is 300 μm or less, it is advantageous in terms of cost. As for the thickness of the said polyester support body, it is more preferable that it is 120-280 micrometers, and it is especially preferable that it is 180-250 micrometers.

The viewpoint that the base film for solar cells of the present invention has a heat shrinkage rate of 1.0% or less after aging at 150 ° C. for 30 minutes of the polyester support, the viewpoint of improving the adhesion after wet heat aging And preferably 0.5% or less.
Such an effect is more remarkable when the thickness of the polyester support is 10 to 40 times the thickness of the functional layer described later.
The in-plane heat shrinkage rate after aging at 150 ° C. for 30 minutes of the polyester support can be adjusted by film forming conditions (stretching conditions during film forming, particularly heat relaxation conditions after stretching).
In general, when the molecular weight of the polyester support is large, thermal shrinkage increases, and may be, for example, about 2%. As will be described later, in an example of a preferred embodiment of the present invention, a polyester support is used. In that case, in order to improve hydrolysis resistance, solid phase polymerization is performed, the molecular weight (IV) is increased, the terminal carboxyl group content AV is decreased to 20 eq / t or less, and the thermal contraction rate is increased. It is preferable to form the polyester support so as to satisfy the conditions.

The polyester support preferably has a surface treated by corona treatment, flame treatment, low pressure plasma treatment, atmospheric pressure plasma treatment, or ultraviolet treatment. By applying these surface treatments, it is possible to further improve the adhesiveness when exposed to a humid heat environment. Among these, by performing the corona treatment, a more excellent adhesive improvement effect can be obtained.
These surface treatments improve the adhesion by increasing carboxyl groups and hydroxyl groups on the surface of the polyester support, but use a crosslinking agent (especially an oxazoline or carbodiimide crosslinking agent that is highly reactive with carboxyl groups). In this case, stronger adhesion can be obtained. This is more remarkable in the case of corona treatment.

2. Polymer layer (adhesive layer)
The substrate film for a solar cell of the present invention has a polymer layer that is disposed on at least one surface of the polyester support and includes a structure derived from a binder and a crosslinking agent, and the binder is an acrylic resin or a polyester resin. It contains at least one kind and a polyolefin resin, and the crosslinking agent is at least one kind of compound among a compound having an oxazoline group and a compound having a carbodiimide group. For the polymer layer using only at least one of acrylic resin and polyester resin as a binder, or the polymer layer using a polyolefin resin alone as a binder, in the present invention, a combination of the above binders and a specific cross-linking By using the agent, the adhesion between the polyester support and the functional layer before and after aging in a moist heat environment is increased.

2-1. Binder The binder contained in the easy-adhesion layer contains at least one of an acrylic resin and a polyester resin and a polyolefin resin.
As the polyolefin resin, acrylic resin, and polyester resin, those having the following embodiments can be preferably used.

  The polyolefin resin that can be used in the present invention is a resin having a main chain skeleton of a polyolefin such as polyethylene or polypropylene. Specific examples of the main chain include ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester- (meth) acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate- ( (Meth) acrylic acid copolymer, ethylene-propylene- (meth) acrylic acid copolymer, ethylene-propylene- (meth) acrylic ester- (meth) acrylic acid copolymer, ethylene-maleic anhydride copolymer, Ethylene- (meth) acrylic acid ester-maleic anhydride copolymer, ethylene-butene-maleic anhydride and / or-(meth) acrylic acid copolymer, propylene-butene-maleic anhydride and / or-(meth) Acrylic acid copolymer, copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, ethylene ) Acrylic acid copolymer.

Among these, those obtained by copolymerizing (meth) acrylic acid are preferable, and ionomer type resins obtained by copolymerizing olefin and methacrylic acid are particularly preferable.
The shape and usage of the polyolefin resin of the present invention are not particularly limited as long as a polymer layer can be formed. For example, it may be a water-dispersible olefin resin or a meltable olefin resin. Further, it may be a crystalline olefin resin or a non-crystalline olefin resin.

A commercially available polyolefin-based resin that can be used in the present invention may be used. Commercially available polyolefin resins include, for example, Arrow Base SE-1010, SE-1013N, SD-1010, TC-4010, TD-4010 (manufactured by Unitika Ltd.), Hitech S3148, S3121, S8512 ( As mentioned above, Toho Chemical Co., Ltd.), Chemipearl S-120, S-75N, V100, EV210H (manufactured by Mitsui Chemicals, Inc.) and the like can be mentioned. Among them, in the present invention, it is preferable to use Arrow Base SE-1013N manufactured by Unitika Ltd.
The olefin-based binder used as the binder for the olefin-based polymer layer may be used alone, or a plurality of the olefin-based binders may be mixed and used.

  The acrylic resin that can be used in the present invention is a polymer obtained by polymerizing acrylic monomers such as polymethyl methacrylate, polyethyl methacrylate, and polymethyl acrylate, and is obtained by copolymerizing acrylic acid, methacrylic acid, or the like as necessary. May be. Examples of the acrylic resin include Julimer ET410, Julimer SEK301, Julimer FC30 (all manufactured by Nippon Pure Chemicals Co., Ltd.) and the like.

  Examples of the polyester-based resin that can be used in the present invention include polyesters such as polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN), such as Vylonal MD-1245 (manufactured by Toyobo Co., Ltd.). It is done.

  In this invention, there is no restriction | limiting in particular about the binder ratio of at least 1 sort (s) among an acrylic resin and a polyester resin, and polyolefin resin. For example, the binder ratio between at least one of acrylic resin and polyester resin and polyolefin resin may be 10:90 to 90:10, for example, preferably 40:60 to 60:40, and 50:50. It is also preferable.

  Among these, it is preferable that the binder contains an acrylic resin and a polyolefin resin in the base film for a solar cell of the present invention from the viewpoint of ensuring adhesion with the polyester support and the functional layer. These polymers may be used alone or in combination of two or more.

2-2. Crosslinking agent The said easily bonding layer uses at least 1 type of a carbodiimide type and an oxazoline type compound as a crosslinking agent for bridge | crosslinking the said binder polymer. These combinations are particularly preferred. The ratio of the oxazoline-based compound / carbodiimide-based crosslinking agent can be, for example, 10/90 to 90/10, preferably 10/90 to 50/50, and more preferably 20/80 to 30/70. More preferred.

Specific examples of the carbodiimide-based crosslinking agent include N, N′-dicyclohexylcarbodiimide, N, N′-diisopropylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N- [3- ( Dimethylamino) propyl] -N′-ethylcarbodiimide, N- [3- (dimethylamino) propyl] -N′-propylcarbodiimide, N-tert-butyl-N′-ethylcarbodiimide and the like.
Moreover, as a commercial item marketed, Carbodilite V-02-L2 (Nisshinbo Co., Ltd. product) etc. are mentioned.

Specific examples of the oxazoline-based crosslinking agent include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2- Oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2,2'-bis- (2-oxazoline), 2,2'-methylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (2-oxazoline), 2,2′-trimethylene-bis- (2-oxazoline), 2,2′-tetramethylene-bis- (2-oxazoline) ), 2,2′-hexamethylene-bis- (2-oxazoline), 2,2′-octamethylene-bis- (2-oxazoline), 2,2′-ethylene-bis- (4,4 ′) Dimethyl-2-oxazoline), 2,2'-p-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene-bis- (2-oxazoline), 2,2'-m-phenylene- Bis- (4,4′-dimethyl-2-oxazoline), bis- (2-oxazolinylcyclohexane) sulfide, bis- (2-oxazolinylnorbornane) sulfide and the like can be mentioned. Furthermore, (co) polymers of these compounds can also be preferably used.
As commercially available products, Epocross WS-700, Epocross K-2020E (both manufactured by Nippon Shokubai Co., Ltd.) and the like can be used.

  As content in the said easily bonding layer of a crosslinking agent, 0.5 mass% or more and 50 mass% or less are preferable with respect to the binder polymer which comprises the said easily bonding layer, 0.5 mass% or more and 30 mass% or less. Is more preferably 5.0% by mass or more and 30% by mass or less, still more preferably 5 to 20% by mass, and even more preferably 3% by mass or more and less than 15% by mass. The When the content of the crosslinking agent is 0.5% by mass or more, a sufficient crosslinking effect is obtained while maintaining the strength and adhesiveness of the polymer layer, and when it is 50% by mass or less, particularly 30% by mass or less, When the coating liquid for forming the polymer layer is adjusted, the pot life of the liquid can be kept longer, and when it is less than 15% by mass, the coated surface state can be improved.

  Moreover, you may add other crosslinking agents, such as an epoxy type, an isocyanate type, and a melamine type.

2-3. Other Additives The easy-adhesion layer in the present invention may contain other additives such as surfactants and fillers as necessary.

-Surfactant-
As the surfactant, known anionic and nonionic surfactants can be used. When the surfactant is contained, the content is preferably 0.1 to 10 mg / m ² , more preferably 0.5 to 3 mg / m ² . When the content of the surfactant is 0.1 mg / m ² or more, an excellent layer is obtained by suppressing the occurrence of repelling when forming a layer, and when it is 10 mg / m ² or less, the polymer support and Good adhesion between the second polymer layer can be maintained.

-Inorganic fine particles (fillers)-
As the filler, known fillers (inorganic fine particles) such as colloidal silica and titanium dioxide can be used.
The content of the inorganic fine particles is preferably 20% by mass or less, more preferably 15% by mass or less with respect to the binder polymer in the first polymer layer.

2-4. Thickness of the easy-adhesion layer The thickness of the easy-adhesion layer in the present invention is preferably 0.03 to 1.0 μm, more preferably 0.05 to 0.5 μm. This is because by setting the thickness to 1 μm or less, the adhesiveness is hardly lowered even when placed in a moist heat environment by suppressing the cost to 0.03 μm or more while keeping the cost low.

3. The manufacturing method of the base film for solar cells There is no restriction | limiting in particular in the manufacturing method of the base film for solar cells of this invention, However, It is preferable that the said polymer layer is formed by application | coating. As a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used.
The polymer layer coating solution may be water based using water as a coating solvent, or may be solvent based using an organic solvent such as toluene or methyl ethyl ketone. Among these, from the viewpoint of environmental burden, it is preferable to use water as a solvent. A coating solvent may be used individually by 1 type, and may mix and use 2 or more types.
The polymer layer coating solution is preferably an aqueous coating solution in which 50% by mass or more, preferably 60% by mass or more, of the solvent contained therein is water. The aqueous coating solution is preferable in terms of environmental load, and is advantageous in that the environmental load is particularly reduced when the ratio of water is 50% by mass or more. The proportion of water in the coating liquid for the polymer layer is preferably larger from the viewpoint of environmental load, and more preferably 90% by weight or more of water is contained in the total solvent.

[Back sheet for solar cells]
The solar cell base film of the present invention is particularly preferably used as a solar cell backsheet.
The 1st aspect of the solar cell backsheet of this invention is a solar cell backsheet by which the white sheet was bonded together in the surface on the opposite side to the surface in which the application layer of the base film for solar cells is provided. It is.
On the other hand, the 2nd aspect of the solar cell backsheet of this invention is the surface on which the said polymer layer of the base film for solar cells is arrange | positioned, or the solar cell backsheet of the 1st aspect of this invention. The aspect which has a functional layer on the surface by which the said polymer layer is arrange | positioned can also be mentioned.

The 1st aspect of the solar cell backsheet of this invention is shown in FIG. In FIG. 5, the back sheet 12 for solar cells of this invention has the white sheet 4 bonded together on the surface on the opposite side to the surface in which the easily bonding layer 3 of the base film 1 for solar cells is provided.
The 2nd aspect of the solar cell backsheet of this invention is shown in FIG. 3 and FIG. In FIG. 3, the solar cell backsheet 12 of this invention has the functional layer 5 on the surface in which the easily bonding layer 3 of the base film 1 for solar cells is provided. Further, as shown in FIG. 6, the solar cell backsheet 12 of the present invention is provided with the easy adhesion layers 3 and 3 ′ on both surfaces of the solar cell base film 1, and the easy adhesion layers 3 and 3. Functional layers 5 and 5 'may be provided on both surfaces of'.
Further, the solar cell backsheet of the present invention may be an embodiment in which the above-described first and second embodiments are combined. The aspect which combined the 1st aspect and the 2nd aspect of the solar cell backsheet of this invention is shown in FIG. In FIG. 6, the back sheet 12 for solar cells of this invention has the white sheet 4 bonded to the surface on the opposite side to the surface in which the easily bonding layer 3 of the base film 1 for solar cells is provided, and is easy. The functional layer 5 is provided on the surface on which the adhesive layer 3 is provided.

(White sheet)
The 1st aspect of the solar cell backsheet of this invention can have a light reflection function and light resistance improvement by having a white sheet.
There is no restriction | limiting in particular as said white sheet used for the 1st aspect of the solar cell backsheet of this invention. For example, the white sheet of the following aspect is preferable.
Those obtained by dispersing a white pigment in various resin films or sheets and those coated are preferred. Examples of the resin film or sheet include polyethylene resin, polypropylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), and acrylonitrile-butadiene-styrene copolymer (ABS resin). , Polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin such as polyethylene terephthalate or polyethylene naphthalate, various polyamide resins such as nylon, polyimide resin, polyamideimide Resin, polyarylphthalate resin, silicone resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyurethane resin, acetal resin, cellulose Fat, other, it is possible to use a film or sheet of various resins. In addition, the foaming of the resin enhances the reflectivity so that the reflection is promoted at the interface between the membrane resin and the microbubbles with greatly different refractive indexes, and exhibits a highly reflective white surface with or without white pigment such as titanium oxide. Reflective materials and reflective films can also be used.
In addition, a white sheet described in JP2007-108242A can be preferably used.
The white sheet preferably contains a white pigment. The white pigment is preferably an inorganic pigment such as titanium dioxide, barium sulfate, silicon oxide, aluminum oxide, magnesium oxide, calcium carbonate, kaolin, talc or colloidal silica, or an organic pigment such as hollow particles.
Further, the adhesive used for bonding the white sheet and the polyester support of the solar cell base film of the present invention is not particularly limited, but for example, the adhesion described in JP-A-2006-210557 and the like. An agent can be preferably used.

(Functional coating layer)
In the 2nd aspect of the solar cell backsheet of this invention, it is preferable that the said functional layer is a functional coating layer formed by application | coating. As a coating method, for example, a known coating method such as a gravure coater or a bar coater can be used. The coating solution may be an aqueous system using water as an application solvent, or a solvent system using an organic solvent such as toluene or methyl ethyl ketone. The said easily bonding layer of the base film for solar cells of this invention has high adhesiveness with any of a solvent type and an aqueous type coating liquid. Among these, from the viewpoint of environmental burden, it is preferable to use water as a solvent. A coating solvent may be used individually by 1 type, and may mix and use 2 or more types. A method in which an aqueous coating solution in which a binder is dispersed in water is formed and applied is preferable. In this case, the proportion of water in the solvent is preferably 60% by mass or more, and more preferably 80% by mass or more. That the functional layer is an aqueous coating type can be confirmed by the amount of residual solvent with respect to the entire polymer layer of the solar cell backsheet being 1000 ppm or less. The residual solvent amount with respect to the entire polymer layers of the solar cell backsheet is more preferably 500 ppm or less, and particularly preferably 100 ppm or less.
Examples of the functional coating layer include functional coating layers such as a white layer formed from a solution containing a white pigment and a weather resistant layer formed from a solution containing a fluorine-containing polymer or a silicone-based polymer. Examples of the white pigment include white pigments used in the white sheet, and the reflective layer can be formed by applying a solution that forms a light reflective reflective layer containing the white pigment. In addition, a weather resistant layer may be formed by applying a solution excellent in weather resistance containing an organic solvent and / or water dispersibility, crosslinkability, and amorphous fluoropolymer as shown in JP-T 2010-519742. it can. In such a second embodiment, the solar cell substrate film of the present invention has good adhesion between the functional coating layer and the polyester support before and after aging in a moist heat environment.

(Manufacture of back sheets for solar cells)

The polymer sheet of the present invention can be preferably used as a solar cell backsheet.
The polymer sheet of the present invention comprises a transparent base material (a front base material such as a glass substrate) disposed on the side on which sunlight is incident, and an element structure part (a solar cell element and a sealing material for sealing it). And a solar cell backsheet, a solar cell having a laminated structure of “transparent front substrate / element structure portion / backsheet”, which is applied to either the front substrate or the backsheet. May be. Here, the back sheet is a back surface protection sheet disposed on the side where the front base material is not located as viewed from the element structure portion of the battery side substrate.
In this specification, a battery part having a laminated structure of “transparent front base material / element structure part” in which an element structure part is arranged on a transparent base material arranged on the side where sunlight enters. Is called a “battery side substrate”.
As described above, the solar cell backsheet including the base film of the present invention is provided with a step of applying a solution having the functions such as whitening and weather resistance described above on the film base having the easily adhesive layer. It can be suitably produced by the production method.
As a suitable coating method, for example, a gravure coater or a bar coater can be used.

[Solar cell module]
The solar cell module of the present invention includes at least one back sheet for a solar cell of the present invention.
The solar cell module of the present invention is opposite to the transparent front substrate on the side on which sunlight is incident, the battery side substrate in which the solar cell elements are sealed with the sealing material, and the front substrate of the battery side substrate. It is preferable that the solar cell back sheet | seat arrange | positioned so that the said sealing material may be contacted on the side may be provided, and the solar cell protection sheet of this invention or the solar cell back sheet | seat of this invention may be provided as said solar cell back sheet. By providing the solar cell backsheet of the present invention described above, heat resistance and moisture resistance are good. Thereby, the outstanding weather resistance performance is shown and the stable power generation performance is demonstrated over a long period of time.

  As a specific configuration, for example, the solar cell module of the present invention includes a solar cell element that converts light energy of sunlight into electric energy, a transparent substrate on which sunlight is incident, and the sun of the present invention described above. It is preferably arranged between the battery back sheet and the solar cell element sealed and bonded with a sealing material such as ethylene-vinyl acetate between the substrate and the back sheet.

  FIG. 7 schematically shows an example of the configuration of the solar cell module of the present invention. This solar cell module 10 includes a solar cell element 20 that converts light energy of sunlight into electrical energy, between the transparent substrate 24 on which sunlight is incident and the solar cell backsheet 12 of the present invention described above. And the substrate and the solar cell backsheet 12 are sealed with an ethylene-vinyl acetate sealing material 22 via an adhesive layer 18 to the sealing material. The solar cell backsheet 12 of the present embodiment includes a solar cell base film in which the easy-adhesion layer 3 is provided on one surface side of the polyester support 2. Moreover, the functional coating layer 5 is provided as a back layer in contact with the easy-adhesion layer 3, and the white sheet 4 is bonded to the other surface side (the side on which sunlight is incident).

  The members other than the solar cell module, the solar cell, and the back sheet are described in detail in, for example, “Photovoltaic power generation system constituent material” (supervised by Eiichi Sugimoto, Kogyo Kenkyukai, published in 2008).

  The said transparent substrate should just have the light transmittance which sunlight can permeate | transmit, and can be suitably selected from the base material which permeate | transmits light. From the viewpoint of power generation efficiency, the higher the light transmittance, the better. For such a substrate, for example, a glass substrate, a transparent resin such as an acrylic resin, or the like can be suitably used. Moreover, you may use the solar cell protection sheet of this invention as the said transparent substrate as needed.

  Examples of the solar cell element include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, and group III-V such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic. Various known solar cell elements such as II-VI group compound semiconductor systems can be applied.

The features of the present invention will be described more specifically with reference to the following examples.
The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Unless otherwise specified, “part” is based on mass.

[Production Example 1]
<Production of PET-1>
(Step 1) -Esterification-
A slurry of 100 kg of high-purity terephthalic acid (manufactured by Mitsui Chemicals) and 45 kg of ethylene glycol (manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.) is charged with about 123 kg of bis (hydroxyethyl) terephthalate in advance, at a temperature of 250 ° C. and a pressure of 1 . The esterification reaction tank maintained at 2 × 10 ⁵ Pa was sequentially supplied over 4 hours, and the esterification reaction was carried out over an additional hour after the completion of the supply. Thereafter, 123 kg of the obtained esterification reaction product was transferred to a polycondensation reaction tank.

(Step 2) -Production of polymer pellets-
Subsequently, 0.3% by mass of ethylene glycol was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, based on the resulting polymer. After stirring for 5 minutes, an ethylene glycol solution of cobalt acetate and manganese acetate was added to 30 ppm and 15 ppm, respectively, with respect to the resulting polymer. After further stirring for 5 minutes, a 2% by mass ethylene glycol solution of a titanium alkoxide compound was added to 5 ppm with respect to the resulting polymer. Five minutes later, a 10% by mass ethylene glycol solution of ethyl diethylphosphonoacetate was added so as to be 5 ppm with respect to the resulting polymer. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was gradually heated from 250 ° C. to 285 ° C. and the pressure was reduced to 40 Pa. The time to reach the final temperature and final pressure was both 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, and the polycondensation reaction was stopped. And it discharged to cold water in the shape of a strand, and it cut immediately, and produced the polymer pellet (about 3 mm in diameter, about 7 mm in length). The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours.
However, the titanium alkoxide compound used was the titanium alkoxide compound (Ti content = 4.44% by mass) synthesized in Example 1 of paragraph No. [0083] of JP-A-2005-340616.

(Step 3)-Solid phase polymerization step-
The pellets obtained in step 2 were held in a vacuum vessel maintained at 40 Pa at a temperature of 220 ° C. for 30 hours to carry out solid phase polymerization.

(Process 4) -Production of film-like resin film substrate-
The pellets produced in step 3 were melted at 280 ° C. and cast on a metal drum to produce an unstretched film having a thickness of about 3 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 210 μm was obtained. This was designated as PET-1.
The carboxyl group content of PET-1 was 15 equivalent / t.
The thermal shrinkage rate of PET-1 before and after aging at 150 ° C. for 30 minutes was measured by the following method and found to be 0.4%.
The obtained polymer support PET-1 was conditioned for 24 hours in an atmosphere of 25 ° C. and a relative humidity of 60. Using the conditioned sample, two scratches parallel to the sample surface at intervals of about 30 cm were made with a razor, and the distance L ⁰ was measured. The scratched sample was heat treated by holding it at 150 ° C. for 30 minutes and aging. After the heat-treated sample was conditioned for 24 hours in an atmosphere of 25 ° C. and a relative humidity of 60%, the distance L ¹ between the two scratches was measured.
The thermal contraction rate was calculated from the obtained L ⁰ and L ¹ using the following formula.
Thermal shrinkage [%] = (L ⁰ −L ¹ ) / L ⁰ × 100
The heat shrinkage rate was measured and calculated for each of the MD direction (longitudinal direction) and TD direction (width direction) of the polymer support, and the average value thereof was taken as the heat shrinkage rate of the polymer support. The unit of heat shrinkage is [%]. When the numerical value is positive, it indicates shrinkage, and when it is negative, it indicates elongation.

[Production Example 2]
<Preparation of PET-2>
Similar to PET-1, it was melted at 280 ° C. and cast on a metal drum to prepare an unstretched film having a thickness of about 3.6 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 210 μm was obtained.
The carboxyl group content of PET-2 was 14 equivalent / t. The thermal contraction rate of PET-2 before and after aging at 150 ° C. for 30 minutes was 0.5%.

[Production Example 3]
<Production of PET-3>
Similar to PET-1, it was melted at 280 ° C. and cast on a metal drum to prepare an unstretched film having a thickness of about 1 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 70 μm was obtained.
The carboxyl group content of PET-3 was 15 equivalent / t. The thermal contraction rate of PET-3 before and after aging at 150 ° C. for 30 minutes was 0.4%.

[Production Example 4]
<Preparation of PET-4>
Similar to PET-1, it was melted at 280 ° C. and cast on a metal drum to prepare an unstretched film having a thickness of about 2 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 130 μm was obtained.
The carboxyl group content of PET-4 was 16 equivalent / t. The thermal contraction rate of PET-4 before and after aging at 150 ° C. for 30 minutes was 0.4%.

[Production Example 5]
<PET-5>
Similar to PET-1, it was melted at 280 ° C. and cast on a metal drum to prepare an unstretched film having a thickness of about 4 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 290 μm was obtained.
The carboxyl group content of PET-5 was 15 equivalent / t. The thermal contraction rate of PET-5 before and after aging at 150 ° C. for 30 minutes was 0.8%.

[Production Example 6]
<PET-6>
Similar to PET-1, it was melted at 280 ° C. and cast on a metal drum to prepare an unstretched film having a thickness of about 0.8 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 50 μm was obtained.
The carboxyl group content of PET-6 was 15 equivalent / t. The thermal contraction rate of PET-6 before and after aging at 150 ° C. for 30 minutes was 0.3%.

[Production Example 7]
<PET-7>
Similar to PET-1, it was melted at 280 ° C. and cast on a metal drum to prepare an unstretched film having a thickness of about 4.5 mm. Thereafter, the film was stretched 3.3 times in the longitudinal direction at 90 ° C., and further stretched 3.8 times in the transverse direction at 120 ° C. Thus, a polymer support of biaxially stretched polyethylene terephthalate having a thickness of 320 μm was obtained.
The carboxyl group content of PET-7 was 14 equivalent / t. The thermal contraction rate of PET-7 before and after aging at 150 ° C. for 30 minutes was 1.2%.

[Example 1]
<Manufacture of Solar Cell Substrate Film of Example 1>
-Corona treatment-
Both surfaces of the PET support formed as described above were conveyed at a conveyance speed of 105 m / min, and a corona discharge treatment was performed under the condition of 730 J / m ² .

-Fabrication of easy-adhesion layer-
Thereafter, on one surface of the PET support subjected to the corona discharge treatment, the easy-adhesion layer coating solution of Example 1 below was dried by a bar coating method to a dry film thickness of 0.13 μm and a dry weight of It apply | coated so that it might become 126 mg / m < ² >.

(Easily adhesive layer coating solution of Example 1)
-Polyacrylic binder 25.71 parts by mass (AS-563A, solid content 28%, manufactured by Daicel Finechem Co., Ltd.)
・ Polyolefin binder (A) 35.64 parts by mass (Unitika Ltd. arrow base SE-1013N solid content 20.2%, ionomer type)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

  After apply | coating an easily bonding layer coating liquid, it dried at 180 degreeC for 1 minute, and formed the 1st layer, and obtained the base film for solar cells of Example 1 which is the 2 layer structure shown in FIG.

<Manufacture of Back Sheet for Solar Cell of Example 1>
-Preparation of coating liquids 1 to 4 and formation of an easily adhesive layer-
The coating liquid for functional coating layer formation 1-4 shown below was apply | coated to the surface at the side of the easily bonding layer side of the base film for solar cells of Example 1, and it laminated | stacked on the structure of FIG.

(Coating liquid 1 for forming a functional coating layer)
The following solvent-based coating solution 1 was prepared with reference to the description of [0054] of JP-T-2010-519742.
Lumiflon (registered trademark) used in the coating solution 1 is LF200 grade obtained as a 60% solution (150 g) of xylene from Asahi Glass Co., Ltd. The pigment used in the coating solution 1 is Ti-Pure (registered trademark) R-105 (57 g) obtained from DuPont. The hydrophobically modified silica used in the coating solution 1 is Cab-o-sil TS-720 (10 g) obtained from Cabot Corporation. The cross-linking agent is Desmodur® N3300 (16 g) obtained from Bayer. The catalyst used in the coating solution 1 is dibutyltin dilaurate (0.15 g of MEK 0.1% solution) obtained from Aldrich. A pigment and hydrophobically modified silica were mixed with a Lumiflon (registered trademark) solution using a high shear mixer, a cross-linking agent and a catalyst were added, and a solvent (methyl ethyl ketone) was added so that the total amount was 400 g to obtain a blended solution. Next, the compounded solution was applied to the surface of the easy-adhesion layer of the solar cell substrate film of Example 1 so that the coating weight was 15 g / m ² by a bar coating method.

(Coating liquid 2 for forming a functional coating layer)
In the coating solution 1 prepared above, instead of a 60% solution of Lumiflon (registered trademark) (150 g) in xylene, a 65% solution of butyl acetate in Zeffle SE-700 (registered trademark) obtained from Daikin Corporation A solvent-based coating solution 2 was prepared in the same manner except that (138 g) was used. The obtained coating solution 2 was applied to the surface of the easy-adhesion layer of the base film for solar cell of Example 1 by the same method as the coating solution 1.

(Coating liquid 3 for forming a functional coating layer)
(1) Synthesis of composite polymer aqueous dispersion P-1 (Step 1)
In a reaction vessel equipped with a stirrer and a dropping funnel and purged with nitrogen gas, 81 parts of propylene glycol mono-n-propyl ether (PNP), 360 parts of isopropyl alcohol (IPA), 110 parts of phenyltrimethoxysilane (PTMS), and dimethyl Dimethoxysilane (DMDMS) 71 parts was charged, and the temperature was raised to 80 ° C. with stirring in a nitrogen gas atmosphere.
(Process 2)
Next, 260 parts of methyl methacrylate (MMA), 200 parts of n-butyl methacrylate (BMA), 110 parts of n-butyl acrylate (BA), 30 parts of acrylic acid (AA), 3-methacryloyl at the same temperature in the reaction vessel. A mixture consisting of 19 parts of oxypropyltrimethoxysilane (MPTMS), 31.5 parts of tert-butylperoxy-2-ethylhexanoate (TBPO), and 31.5 parts of PNP was added dropwise over 4 hours. Thereafter, the mixture was heated and stirred at the same temperature for 2.5 hours to obtain an acrylic polymer solution having a weight average molecular weight of 29,300 and containing a carboxyl group and a hydrolyzable silyl group.
(Process 3)
Next, 54.8 parts of deionized water was added thereto, and heating and stirring were continued for 16 hours to hydrolyze the alkoxysilane and further condense with an acrylic polymer, so that the non-volatile content (NV) = 56.3 mass%. A solution of a composite polymer having a structural unit derived from a carboxyl group-containing acrylic polymer and a polysiloxane structural unit having a solution acid value = 22.3 mgKOH / g was obtained.
(Process 4)
Next, 42 parts of triethylamine was added to this solution at the same temperature while stirring, and stirring was performed for 10 minutes. Thereby, 100% of the contained carboxyl groups were neutralized.
(Process 5)
Thereafter, 1250 parts of deionized water was added dropwise at the same temperature over 1.5 hours for phase inversion emulsification, and then the mixture was heated to 50 ° C. and stirred for 30 minutes. Next, a part of water was removed under reduced pressure together with the organic solvent over 3.5 hours at an internal temperature of 40 ° C.
Thus, an aqueous dispersion P-1 of a composite polymer containing a polysiloxane structural unit having a solid content concentration of 42% by mass and an average particle size of 110 nm and a structural unit derived from a carboxyl group-containing acrylic polymer was obtained. The aqueous dispersion P-1 has a polysiloxane structural unit of about 25% and an acrylic polymer structural unit of about 75%.
(2) Preparation of Coating Solution 3 for Functional Coating Layer Formation The following components (i) to (iv) were mixed to prepare an aqueous coating solution 3 containing a composite polymer containing a polysiloxane structural unit.
-Composition of coating solution 3 (i) Composite polymer aqueous dispersion P-1 ... 45.9 parts by mass (binder, solid content concentration 42% by mass)
(Ii) Oxazoline compound (crosslinking agent) 7.7 parts by mass (Epocross WS-700, manufactured by Nippon Shokubai Chemical Industry Co., Ltd., solid content: 25% by mass)
(Iii) Polyoxyalkylene alkyl ether: 2.0 parts by mass (Naguchi Acty CL95, manufactured by Sanyo Chemical Industries, solid content: 1% by mass)
(Iv) Distilled water: 44.4 parts by mass (3) Formation of coating layer The obtained coating solution 3 was bonded to the surface of the easy-adhesion layer and the easy-adhesion layer of the solar cell substrate film of Example 1. The coating was applied so that the amount was 3.0 g / m ² and dried at 180 ° C. for 1 minute to form a coating layer containing a composite polymer containing a polysiloxane structural unit having a dry thickness of 3 μm.

(Coating liquid 4 for forming a functional coating layer)
With reference to the coating solution described in Comparative Example 1 of JP-A-2008-189828, the following aqueous coating solution 4 was prepared.
Silicone compound: 80 parts (Carboxy-modified silicone, Shin-Etsu Chemical Co., Ltd., trade name: X22-3701E)
-Surfactant: 15 parts (Polyoxyethylene (n = 8.5) lauryl ether, Sanyo Chemical Co., Ltd., trade name NAROACTY N-85)
・ Crosslinking agent: 5 parts (Oxazoline, manufactured by Nippon Shokubai Co., Ltd., trade name: Epocross WS-300)

Distilled water was added to these materials until an aqueous solution having a solid content of 2% was obtained to obtain a coating solution 4 for forming a functional coating layer. The obtained coating liquid 4 was applied to the surface of the easy-adhesion layer of the solar cell substrate film of Example 1 so that the coating weight was 1 g / m ² by a bar coating method.

-Bonding white sheets-
A white sheet having a thickness of 25 μm (DuPont) was formed on the surface opposite to the surface provided with the easy-adhesion layer and the functional coating layer of the base film for solar cell of Example 1 with respect to the obtained laminate having the structure shown in FIG. A product name, Tedlar Film, manufactured by Co., Ltd. was bonded. The obtained laminate of the configuration shown in FIG. 6 was used as the solar cell backsheet of Example 1.

<Adhesion evaluation with coating solution for functional coating layer formation>
About the solar cell backsheet of Example 1, the adhesiveness between the base film before and after wet heat aging and each functional coating solution was evaluated.

-Evaluation of adhesiveness with functional coating liquid-
(1) Adhesiveness before wet heat aging In the solar cell backsheet 12 of Example 1 having the configuration shown in FIG. 6, the surface on the functional coating layer 5 side was scratched by 6 single-sided razors in a longitudinal and lateral direction. 25 squares were formed. A Mylar tape (polyester tape) was affixed thereon and peeled by manually pulling it in the 180 ° direction along the sample surface. At this time, the adhesive strength of the functional coating layer was ranked according to the following evaluation criteria according to the number of the peeled cells. Evaluation ranks 4 and 5 are practically acceptable ranges.
<Evaluation criteria>
5: There was no cell which peeled (0 cell).
4: The peeled square was from 0 square to less than 0.5 square.
3: The squares which peeled were 0.5 squares or more and less than 2 squares.
2: The square which peeled was 2 squares or more and less than 10 squares.
1: The square which peeled was 10 squares or more.
The ranking results are shown in Table 1 below.

(2) Adhesiveness after aging with wet heat After the solar cell backsheet 12 of Example 1 having the configuration shown in FIG. 6 was maintained at 120 ° C. under environmental conditions of 100% relative humidity for 48 hours, then 23 ° C. relative After adjusting the humidity for 1 hour in an environment of 50% humidity, the adhesive strength of the functional coating layer 5 was evaluated by the same method and evaluation criteria as the evaluation of “(1) Adhesiveness before wet heat aging”.
The ranking results are shown in Table 1 below.

<Evaluation of flatness>
The solar cell backsheet sample of Example 1 having the configuration shown in FIG. 6 was cut into a size of 30 cm × 40 cm and conditioned for 24 hours in an atmosphere of 25 ° C. and a relative humidity of 60%. This sample is placed on a flat glass plate placed horizontally in a room at 25 ° C. and a relative humidity of 60% (for example, the white sheet 4 in FIG. 6 is in contact with the glass plate). In this state, among the floats of the sample from the glass plate, the “floating height (floating 1)” of the largest distance from the glass plate was measured. The “floating height” was measured up to an order of 1 mm using a height gauge (standard height gauge HS, manufactured by Mitutoyo Corporation).
Subsequently, the sample was placed so that the opposite surface (in this case, the functional coating layer in FIG. 6 was in contact with the glass plate) was in contact with the glass plate, and “Float 2” was measured in the same manner. The average value (unit: mm) of the float 1 and the float 2 was defined as the float of the sample. The smaller the value of the float, the better the flatness of the sample.
The measured floats were ranked into the following 5 ranks.
<Evaluation criteria>
Rank 5 Float 0mm
Rank 4 Float is over 0mm and within 2mm Rank 3 Float is over 2mm and within 4mm Rank 2 Float is over 4mm and within 6mm Rank 1 Float is over 6mm Of these, practically acceptable It is classified into ranks 3 to 5, and ranks 4 and 5 are preferable.
The ranking results are shown in Table 1 below.

[Example 2]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 2 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Example 2)
・ Polyester binder 24.00 parts by mass (Toyobo Co., Ltd. Bironal MD-1245 solid content 30%)
・ Polyolefin binder (A) 35.64 parts by mass (Unitika Ltd. arrow base SE-1013N solid content 20.2%, ionomer type)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Example 3]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 3 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Example 3)
25.71 parts by mass of polyacryl binder (Daicel Finechem Co., Ltd. AS-563A, solid content 28%)
18.00 parts by mass of polyolefin binder (B) (Chemical V-300, solid content 40%, manufactured by Mitsui Chemicals, Inc.)
Ethylene vinyl acetate copolymer carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
Oxazoline compound 3.0 parts by mass (Epocross WS700, solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
Add distilled water to 1000 parts by mass

[Example 4]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 4 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Example 4)
24.00 parts by mass of polyester binder (manufactured by Toyobo Co., Ltd., Baironal MD-1245, solid content 30%)
18.00 parts by mass of polyolefin binder (B) (Chemical V-300, solid content 40%, manufactured by Mitsui Chemicals, Inc.)
Carbodiimide compound 6.13 parts by mass (Carbodilite V-02-L2 solid content 40% manufactured by Nisshinbo Co., Ltd.)
Oxazoline compound 3.0 parts by mass (Epocross WS700, solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
Add distilled water to 1000 parts by mass

[Example 5]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 5 were produced in the same manner as in Example 1 except that PET-1 was replaced with PET-2. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 6]
In Example 2, the base film for solar cells and the solar cell back sheet of Example 6 were produced in the same manner as in Example 2 except that PET-1 was replaced with PET-2. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 7]
In Example 1, the base film for solar cells and the solar cell backsheet of Example 7 were produced in the same manner as in Example 1 except that PET-1 was replaced with PET-3. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 8]
In Example 2, the solar cell base film and solar cell backsheet of Example 8 were produced in the same manner as in Example 2 except that PET-1 was replaced with PET-3. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 9]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 9 were produced in the same manner as in Example 1 except that PET-1 was replaced with PET-4. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 10]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 10 were produced in the same manner as in Example 1 except that PET-1 was replaced with PET-5. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 11]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 11 were produced in the same manner as in Example 1 except that PET-1 was replaced with PET-6. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Example 12]
In Example 1, the base film for solar cells and the solar cell back sheet of Example 12 were produced in the same manner as in Example 1 except that PET-1 was replaced with PET-7. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 1]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 1 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 1)
-Polyurethane binder 18.95 parts by mass (Orestar UD-350, solid content 38%, manufactured by Mitsui Chemicals, Inc.)
・ 35.64 parts by mass of polyolefin binder (available from Unitika Ltd. Arrow Base SE-1013N solid content 20.2%)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 2]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 2 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 2)
-Polyurethane binder 18.95 parts by mass (Orestar UD-350, solid content 38%, manufactured by Mitsui Chemicals, Inc.)
-Polyolefin binder (B) 18.00 parts by mass (Chemical V-300, solid content 40%, manufactured by Mitsui Chemicals, Inc.)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 3]
In Comparative Example 1, a solar cell substrate film and a solar cell backsheet of Comparative Example 3 were produced in the same manner as Comparative Example 1 except that PET-1 was replaced with PET-2. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 4]
In Comparative Example 1, a solar cell substrate film and a solar cell backsheet of Comparative Example 4 were produced in the same manner as Comparative Example 1 except that PET-1 was replaced with PET-3. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 5]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 5 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 5)
-51.42 parts by mass of polyacryl binder (manufactured by Daicel Finechem Co., Ltd. AS-563A, solid content 28%)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 6]
In Comparative Example 5, a solar cell substrate film and a solar cell backsheet of Comparative Example 6 were produced in the same manner as Comparative Example 5 except that PET-1 was replaced with PET-3. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 7] Replacing PET of Comparative Example 5 with PET-2 In Comparative Example 5, the base material for solar cell of Comparative Example 7 was the same as Comparative Example 5 except that PET-1 was replaced with PET-2. Films and solar cell backsheets were manufactured. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 8]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 8 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 8)
-Polyester binder 48.00 parts by mass (Toyobo Co., Ltd. Bironal MD-1245 solid content 30%)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surface activity 15.0 parts by mass (1% aqueous solution of NAROACTY CL-95 manufactured by Sanyo Chemical Industries)
・ Add distilled water to 1000 parts by mass

[Comparative Example 9]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 9 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 9)
Polyolefin binder (A) 71.28 parts by mass (Unitika Co., Ltd. Arrow Base SE-1013N solid content 20.2%)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 10]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 10 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 10)
Polyolefin binder (B) 36.00 parts by mass (Chemical V-300, solid content 40%, manufactured by Mitsui Chemicals, Inc.)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 11]
In Comparative Example 9, a solar cell substrate film and a solar cell backsheet of Comparative Example 11 were produced in the same manner as Comparative Example 9 except that PET-1 was replaced with PET-3. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 12]
In Comparative Example 9, a solar cell substrate film and a solar cell backsheet of Comparative Example 12 were produced in the same manner as Comparative Example 9 except that PET-1 was replaced with PET-2. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.

[Comparative Example 13]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 13 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 13)
・ Polyurethane binder 37.90 parts by mass (Orestar UD-350, solid content 38%, manufactured by Mitsui Chemicals, Inc.)
-Carbodiimide compound 6.13 parts by mass (Nisshinbo Co., Ltd. Carbodilite V-02-L2 solid content 40%)
-Oxazoline compound 3.0 parts by mass (Epocross WS700 solid content 25%, manufactured by Nippon Shokubai Co., Ltd.)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 14]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 15 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 14)
-Polyacrylic binder 25.71 parts by mass (AS-563A, solid content 28%, manufactured by Daicel Finechem Co., Ltd.)
・ Polyolefin binder (A) 35.64 parts by mass (Unitika Ltd. arrow base SE-1013N solid content 20.2%)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 15]
In Example 1, the substrate for solar cells of Comparative Example 15 was obtained in the same manner as in Example 1 except that PET-1 was replaced with PET-3 and the composition of the easy-adhesive coating solution used as described below was changed. Films and solar cell backsheets were manufactured. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 15)
-Polyacrylic binder 25.71 parts by mass (AS-563A, solid content 28%, manufactured by Daicel Finechem Co., Ltd.)
・ Polyolefin binder (A) 35.64 parts by mass (Unitika Ltd. arrow base SE-1013N solid content 20.2%)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

[Comparative Example 16]
In Example 1, the base film for solar cells and the solar cell back sheet of Comparative Example 16 were produced in the same manner as in Example 1 except that the composition of the easy-adhesion coating solution used as described below was changed. The obtained solar cell backsheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1 below.
(Easily adhesive layer coating solution of Comparative Example 16)
・ Polyester binder 24.00 parts by mass (Toyobo Co., Ltd. Bironal MD-1245 solid content 30%)
・ Polyolefin binder (A) 35.64 parts by mass (Unitika Ltd. Arrow Base SE-1013N solid content 20.2%)
Surfactant A 15.0 parts by mass (manufactured by Sanyo Chemical Industries, Ltd. 1% aqueous solution of NAROACTY CL-95)
・ Add distilled water to 1000 parts by mass

From Table 1, it turned out that the base film for solar cells and the back sheet for solar cells of this invention are excellent in the adhesiveness of a weather-resistant polyester support body and a functional layer through before and after wet heat aging.
Further, in the case of using the coating liquids 1 and 2 which are solvent-based coating liquids, and in the case of using the coating liquids 3 and 4 which are water-based coating liquids, the weather-resistant polyester support and the functional coating layer are subjected to the wet heat aging. It was found to be excellent in adhesiveness.

(Example 101)
<Production of solar cell module>
3 mm thick tempered glass, EVA sheet (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.), crystalline solar cell, EVA sheet (SC50B manufactured by Mitsui Chemicals Fabro Co., Ltd.), and the sun of Example 101 By stacking the protective sheet for the battery in this order so that the white layer of the protective sheet for the solar cell is in direct contact with the EVA sheet, by hot pressing using a vacuum laminator (Nisshinbo Co., Ltd., vacuum laminating machine), Glued with EVA. At this time, the back sheet produced in Example 1 was disposed so that the easy-adhesion layer was in contact with the EVA sheet. Moreover, the adhesion method is as follows.
<Adhesion method>
Using a vacuum laminator, evacuation was performed at 128 ° C. for 3 minutes, and then pressure was applied for 2 minutes to temporarily bond. Thereafter, the main adhesion treatment was performed in a dry oven at 150 ° C. for 30 minutes.
As described above, a solar cell module of Example 101 of a crystal system was produced. The produced solar cell module was allowed to stand for 70 hours under an environmental condition of 120 ° C. and 100% relative humidity and then operated for power generation.

(Examples 102 to 124)
In Example 101, a solar cell module was produced in the same manner as in Example 101 except that the solar cell protective sheet produced in Example 1 was replaced with the solar cell protective sheet produced in Examples 2-24.
When the obtained solar cell module was subjected to power generation operation in the same manner as in Example 101, all showed good power generation performance as a solar cell.

DESCRIPTION OF SYMBOLS 1 Base film 2 for solar cells Polyester support body 3, 3 'Easy-adhesion layer 4 White sheet 5, 6' Functional application layer 10 Solar cell module 12 Back sheet 16 for solar cells Support body 18 Adhesiveness to sealing material Layer 22 Encapsulant 20 Solar cell element 24 Transparent front substrate (tempered glass)

Claims (10)

A polyester support having a carboxyl group content of 20 equivalent / t or less;
Having a polymer layer disposed on at least one side of the polyester support and comprising a structure derived from a binder and a crosslinking agent;
The binder includes at least one of an acrylic resin and a polyester resin, and a polyolefin resin;
The base film for solar cells, wherein the crosslinking agent is at least one compound selected from a compound having an oxazoline group and a compound having a carbodiimide group.   The base film for a solar cell according to claim 1, wherein the polymer layer is formed by applying a coating liquid containing the binder and the crosslinking agent.   The base film for a solar cell according to claim 1 or 2, wherein the polyolefin resin is of an ionomer type.   The said binder contains an acrylic resin and polyolefin resin, The base film for solar cells as described in any one of Claims 1-3 characterized by the above-mentioned.   The thickness of the said polyester support body is 60-300 micrometers, The base film for solar cells as described in any one of Claims 1-4 characterized by the above-mentioned.   The base film for solar cells according to any one of claims 1 to 5, wherein the polyester substrate has a heat shrinkage rate of 1% or less.   A white sheet is bonded to the surface opposite to the surface on which the polymer layer of the solar cell base film according to any one of claims 1 to 6 is provided, Back sheet for solar cells.   The said polymer layer of the solar cell backsheet of Claim 7 is arrange | positioned on the surface by which the said polymer layer of the base film for solar cells as described in any one of Claims 1-6 is arrange | positioned. A back sheet for a solar cell, comprising a functional layer on the surface of the solar cell.   The said functional layer is a functional coating layer formed by application | coating, The solar cell backsheet of Claim 8 characterized by the above-mentioned.   The solar cell module characterized by including the solar cell backsheet as described in any one of Claims 7-9.

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